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Sample records for cd sn te

  1. Theoretical and experimental study of α-Sn deposited on CdTe(001)

    International Nuclear Information System (INIS)

    Gomez, J.A.; Guenzburger, D.; Ellis, D.E.; Hu, M.Y.; Baggio-Saitovitc, E.M.; Passamani, E.C.; Alp, E.E.

    2003-01-01

    Gray tin films enriched by over 95% 119 Sn and grown by molecular beam epitaxy on CdTe(001) wafers are characterized by inelastic nuclear resonance spectroscopy and investigated theoretically by embedded-cluster density-functional theory methods. Experimental tin phonon densities of states are obtained via analysis of resonant scattering of the 23.88-keV nuclear transition, making use of a high-resolution spectrometer at the Advanced Photon Source. Conventional Moessbauer spectroscopy is used in the scattering mode to determine hyperfine parameters of the α-Sn phase and, after thermal treatment, the β phase. Electronic structure in the vicinity of Sn-Cd and Sn-Te interfaces is calculated in order to determine local charge transfer and changes in hyperfine parameters for 119 Sn atoms in the interface region. Although, due to sample thickness, both experiments reveal properties essentially of the bulk, the calculations allow investigation of surface and interface regions at an atomic level, thus providing complementary information. Effects of interlayer relaxation are explored.

  2. Laser operation by dissociation of metal complexes. II - New transitions in Cd, Fe, Ni, Se, Sn, Te, V, and Zn

    Science.gov (United States)

    Chou, M. S.; Cool, T. A.

    1977-01-01

    The reported investigation is a continuation of a study conducted by Chou and Cool (1976). The experimental results discussed are partly related to laser transitions in Cd(I), Cd(II), and Zn(II). Laser transitions in Fe(I), Ni(I), Sn(I), Te(I), and V(I) are also considered along with the observation of a laser pulse with two peaks in connection with the study of laser transitions in Se(I). Experiments related to prospective visible laser operation in thallium at 6550 and 6714 are also discussed, giving attention to spontaneous emission measurements at 6550 and 5350 A, the effects of additive molecules, and laser cavity experiments at 6550 and 6714 A.

  3. Characterization of core/shell structures based on CdTe and GaAs nanocrystalline layers deposited on SnO2 microwires

    Science.gov (United States)

    Ghimpu, L.; Ursaki, V. V.; Pantazi, A.; Mesterca, R.; Brâncoveanu, O.; Shree, Sindu; Adelung, R.; Tiginyanu, I. M.; Enachescu, M.

    2018-04-01

    We report the fabrication and characterization of SnO2/CdTe and SnO2/GaAs core/shell microstructures. CdTe or GaAs shell layers were deposited by radio-frequency (RF) magnetron sputtering on core SnO2 microwires synthesized by a flame-based thermal oxidation method. The produced structures were characterized by scanning electron microscopy (SEM), high-resolution scanning transmission electron microscope (HR-STEM), X-ray diffraction (XRD), Raman scattering and FTIR spectroscopy. It was found that the SnO2 core is of the rutile type, while the shells are composed of CdTe or GaAs nanocrystallites of zincblende structure with the dimensions of crystallites in the range of 10-20 nm. The Raman scattering investigations demonstrated that the quality of the porous nanostructured shell is improved by annealing at temperatures of 420-450 °C. The prospects of implementing these microstructures in intrinsic type fiber optic sensors are discussed.

  4. Measurement of cross sections producing short-lived nuclei by 14MeV neutron. Cd, Sn, Te, Nd, Gd, Re

    Energy Technology Data Exchange (ETDEWEB)

    Sakane, H.; Yamamoto, H.; Kawade, K. [Nagoya Univ. (Japan); Iida, T.; Takahashi, A.

    1998-03-01

    Nine neutron activation cross sections producing the nuclei with half-lives between 25sec and 22min were measured at energy range between 13.4 and 14.9 MeV by activation method. The (n,p) and (n,{alpha}) reaction cross sections were measured for the isotopes of {sup 110}Cd, {sup 112}Sn, {sup 122}Te, {sup 130}Te and {sup 185}Re and those of {sup 130}Te, {sup 148}Nd and {sup 158}Gd, respectively. The present results were compared with our systematics proposed on the basis of 58 cross section data of (n,p) and 33 data of (n,{alpha}) reaction. Good agreements have been seen between them. (author)

  5. Electrical and optical properties of SnEuTe and SnSrTe films

    Science.gov (United States)

    Ishida, Akihiro; Tsuchiya, Takuro; Yamada, Tomohiro; Cao, Daoshe; Takaoka, Sadao; Rahim, Mohamed; Felder, Ferdinand; Zogg, Hans

    2010-06-01

    The SnTe, Sn1-xEuxTe and Sn1-xSrxTe (x<0.06) films were prepared by hot wall epitaxy. The ternary alloy films prepared in cation rich condition had hole concentration around 1×1019 cm-3 with high mobility exceeding 2000 cm2/V s at room temperature. Optical transmission spectra were also measured in the temperature range from 100 to 400 K and compared with theoretical calculations. Optical transmission spectra of the SnTe were simulated successfully assuming bumped band edge structures. A band inversion model was proposed for the Sn1-xEuxTe and Sn1-xSrxTe systems, and the optical transmission spectra were also simulated successfully assuming the band inversion model.

  6. Correlation between some thermo-mechanical and physico-chemical properties in multi-component glasses of Se-Te-Sn-Cd system

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Amit; Mehta, Neeraj [Banaras Hindu University, Department of Physics, Institute of Science, Varanasi (India)

    2017-06-15

    The glass transition phenomenon is guided by the swift cooling of a melt (glass-forming liquid). Consequently, the glass as a final product consists of a considerable number of micro-voids having the size of the order of atomic and/or molecular sizes. The model of free volume fluctuation helps in describing the diverse physico-chemical properties of amorphous materials (like glasses and polymers). This theory is based on the fraction of fluctuation free frozen at the glass transition temperature and it forms a basis for determination of various significant thermo-mechanical properties. In the present work, Vickers hardness test method is employed that provides useful information concerning the mechanical behavior of brittle solids. The present work emphasizes the results of micro-indentation measurements on recently synthesized novel Se{sub 78-x}Te{sub 20}Sn{sub 2}Cd{sub x} glassy system. Basic thermo-mechanical parameters such as micro-hardness, volume (V{sub h}), formation energy (E{sub h}) of micro-voids in the glassy network and modulus of elasticity (E) have been determined and their variation with glass composition has been investigated. (orig.)

  7. Shell model calculation for Te and Sn isotopes in the vicinity of {sup 100}Sn

    Energy Technology Data Exchange (ETDEWEB)

    Yakhelef, A.; Bouldjedri, A. [Physics Department, Farhat abbas University, Setif (Algeria); Physics Department, Hadj Lakhdar University, Batna (Algeria)

    2012-06-27

    New Shell Model calculations for even-even isotopes {sup 104-108}Sn and {sup 106,108}Te, in the vicinity of {sup 100}Sn have been performed. The calculations have been carried out using the windows version of NuShell-MSU. The two body matrix elements TBMEs of the effective interaction between valence nucleons are obtained from the renormalized two body effective interaction based on G-matrix derived from the CD-bonn nucleon-nucleon potential. The single particle energies of the proton and neutron valence spaces orbitals are defined from the available spectra of lightest odd isotopes of Sb and Sn respectively.

  8. Thin-film CdS/CdTe solar cells

    International Nuclear Information System (INIS)

    Tyan, Y.S.; Perez-Albuerne, E.A.

    1985-01-01

    A thin-film solar cell with the configuration soda-lime glass ITO/CdS/CdTe/Au was reported earlier to have more than 10% conversion efficiency. To further improve the low-cost potential of the device, an SnO/sub 2/ layer was developed to replace ITO, and a new contact to CdTe using Ni or stainless steel to replace Au. The contact also improves the stability of the device. A low-cost method for monolithic integration of these cells to make a module is discussed. By this method, a module of 32 cm/sup 2/ area and 8.5% efficiency was fabricated. A simple and effective ''cross-cut'' method for minimizing the effects of shorting defects is also described

  9. CdSxTe1-x Alloying in CdS/CdTe Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Duenow, J. N.; Dhere, R. G.; Moutinho, H. R.; To, B.; Pankow, J. W.; Kuciauskas, D.; Gessert, T. A.

    2011-05-01

    A CdSxTe1-x layer forms by interdiffusion of CdS and CdTe during the fabrication of thin-film CdTe photovoltaic (PV) devices. The CdSxTe1-x layer is thought to be important because it relieves strain at the CdS/CdTe interface that would otherwise exist due to the 10% lattice mismatch between these two materials. Our previous work [1] has indicated that the electrical junction is located in this interdiffused CdSxTe1-x region. Further understanding, however, is essential to predict the role of this CdSxTe1-x layer in the operation of CdS/CdTe devices. In this study, CdSxTe1-x alloy films were deposited by RF magnetron sputtering and co-evaporation from CdTe and CdS sources. Both radio-frequency-magnetron-sputtered and co-evaporated CdSxTe1-x films of lower S content (x<0.3) have a cubic zincblende (ZB) structure akin to CdTe, while those of higher S content have a hexagonal wurtzite (WZ) structure like that of CdS. Films become less preferentially oriented as a result of a CdCl2 heat treatment at ~400 degrees C for 5 min. Films sputtered in a 1% O2/Ar ambient are amorphous as deposited, but show CdTe ZB, CdS WZ, and CdTe oxide phases after a CdCl2 heat treatment (HT). Films sputtered in O2 partial pressure have a much wider bandgap (BG) than expected. This may be explained by nanocrystalline size effects seen previously [2] for sputtered oxygenated CdS (CdS:O) films.

  10. CdSxTe1-x Alloying in CdS/CdTe Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Duenow, J. N.; Dhere, R. G.; Moutinho, H. R.; To, B.; Pankow, J. W.; Kuciauskas, D.; Gessert, T. A.

    2011-01-01

    A CdS{sub x}Te{sub 1-x} layer forms by interdiffusion of CdS and CdTe during the fabrication of thin film CdTe photovoltaic (PV) devices. The CdS{sub x}Te{sub 1-x} layer is thought to be important because it relieves strain at the CdS/CdTe interface that would otherwise exist due to the 10% lattice mismatch between these two materials. Our previous work has indicated that the electrical junction is located in this interdiffused CdS{sub x}Te{sub 1-x} region. Further understanding, however, is essential to predict the role of this CdS{sub x}Te{sub 1-x} layer in the operation of CdS/CdTe devices. In this study, CdS{sub x}Te{sub 1-x} alloy films were deposited by radio-frequency magnetron sputtering and coevaporation from CdTe and CdS sources. Both radio-frequency-magnetron-sputtered and coevaporated CdS{sub x}Te{sub 1-x} films of lower S content (x < 0.3) have a cubic zincblende (ZB) structure akin to CdTe, whereas those of higher S content have a hexagonal wurtzite (WZ) structure like that of CdS. Films become less preferentially oriented as a result of a CdCl{sub 2} heat treatment at {approx}400 C for 5 min. Films sputtered in a 1% O{sub 2}/Ar ambient are amorphous as deposited, but show CdTe ZB, CdS WZ, and CdTe oxide phases after a CdCl{sub 2} heat treatment. Films sputtered in O{sub 2} partial pressure have a much wider bandgap than expected. This may be explained by nanocrystalline size effects seen previously for sputtered oxygenated CdS (CdS:O) films.

  11. PbSnTe injection lasers

    International Nuclear Information System (INIS)

    Oron, M.

    1982-03-01

    Carrier confined homostructure PbSnTe lasers were developed and investigated. In this laser structure good electrical and optical confinement can be achieved by a suitable carrier concentration profile. The advantage of these lasers over PbSnTe heterostructure lasers is the perfect lattice matching between the various layers of the structure. The desired carrier concentration profile was achieved by the growth of several epitaxial layers by the LPE method on a suitable substrate. The performance of these lasers was compared with that of previous homostructure and double heterostructure lasers. (H.K.)

  12. Neutron scattering on molten Ge-Sn-Te alloys

    Science.gov (United States)

    Halm, Th; Hinz, W.; Hoyer, W.

    1995-01-01

    Three molten ternary Ge-Sn-Te alloys lying on the quasibinary line Ge-SnTe, and the binary equiatomic alloys SnTe and GeTe have been investigated by neutron "time-of-flight" experiments. Published thermodynamic results are interpreted in terms of the coexistence of SnTe and Ge microgroupings in the melt. Using the experimental obtained data of the binary liquid alloy Sn50Te50 and of liquid Ge the structure factors of the ternary melts are calculated on the base of a microheterogeneous model.

  13. Electrical properties of MIS devices on CdZnTe/HgCdTe

    Science.gov (United States)

    Lee, Tae-Seok; Jeoung, Y. T.; Kim, Hyun Kyu; Kim, Jae Mook; Song, Jinhan; Ann, S. Y.; Lee, Ji Y.; Kim, Young Hun; Kim, Sun-Ung; Park, Mann-Jang; Lee, S. D.; Suh, Sang-Hee

    1998-10-01

    In this paper, we report the capacitance-voltage (C-V) properties of metal-insulator-semiconductor (MIS) devices on CdTe/HgCdTe by the metalorganic chemical vapor deposition (MOCVD) and CdZnTe/HgCdTe by thermal evaporation. In MOCVD, CdTe layers are directly grown on HgCdTe using the metal organic sources of DMCd and DiPTe. HgCdTe layers are converted to n-type and the carrier concentration, ND is low 1015 cm-3 after Hg-vacancy annealing at 260 degrees Celsius. In thermal evaporation, CdZnTe passivation layers were deposited on HgCdTe surfaces after the surfaces were etched with 0.5 - 2.0% bromine in methanol solution. To investigate the electrical properties of the MIS devices, the C-V measurement is conducted at 80 K and 1 MHz. C-V curve of MIS devices on CdTe/HgCdTe by MOCVD has shown nearly flat band condition and large hysteresis, which is inferred to result from many defects in CdTe layer induced during Hg-vacancy annealing process. A negative flat band voltage (VFB approximately equals -2 V) and a small hysteresis have been observed for MIS devices on CdZnTe/HgCdTe by thermal evaporation. It is inferred that the negative flat band voltage results from residual Te4+ on the surface after etching with bromine in methanol solution.

  14. Piezoelectric effect in CdTe/CdMnTe and CdTe/CdZnTe quantum wells

    International Nuclear Information System (INIS)

    Andre, Regis

    1994-01-01

    Materials with zinc-blende type structure are piezoelectric: any strain along a polar axis generates an electrical polarisation. Strained quantum wells of cubic II-VI or III-V semiconductors, grown along [111] or [112] axis, exhibit a strong built-in piezo-electric field (100 kV/cm for 1% strains). Such structures are very promising for applications to optical modulation, but it is necessary to study first the physical properties of piezoelectric heterostructures before they can be used in optical devices. For this purpose, we have performed an optical study of strained CdTe/CdMnTe or CdTe/CdZnTe quantum wells coherently grown by molecular beam epitaxy on [111] or [112] oriented substrates. Effects of piezoelectric field on optical and electronic properties of quantum wells have been analyzed in terms of the envelop function model, taking into account the effects of biaxial strains for [hhk] growth axis. Moreover, we have proposed an original way of measuring piezoelectric field in strained quantum wells, and we have used this method to show that CdTe exhibits strong non-linearities for piezoelectric field versus strain. This effect has never been mentioned before. We have also performed measurements of the piezoelectric coefficient e14 under high hydrostatic pressure inducing strains up to 2%, which shows that part of the non-linear effect is a volume effect. We have also studied the effects of the piezoelectric field on excitons in quantum wells. The binding energy decreases slightly when the electric field increases, but the oscillator strength, for the fundamental transition, decreases dramatically with the overlap of the envelope wavefunctions of electrons and holes. We have performed a modelization of an exciton in a piezoelectric quantum well using two variational parameters. This model provides an accurate calculation of excitonic absorption. Our experimental and theoretical results are in very good agreement, without any fitting parameters, for a large

  15. Surface passivation for CdTe devices

    Energy Technology Data Exchange (ETDEWEB)

    Reese, Matthew O.; Perkins, Craig L.; Burst, James M.; Gessert, Timothy A.; Barnes, Teresa M.; Metzger, Wyatt K.

    2017-08-01

    In one embodiment, a method for surface passivation for CdTe devices is provided. The method includes adjusting a stoichiometry of a surface of a CdTe material layer such that the surface becomes at least one of stoichiometric or Cd-rich; and reconstructing a crystalline lattice at the surface of the CdTe material layer by annealing the adjusted surface.

  16. S and Te inter-diffusion in CdTe/CdS hetero junction

    Energy Technology Data Exchange (ETDEWEB)

    Enriquez, J. Pantoja [Cuerpo Academico-Energia y Sustentabilidad, Universidad Politecnica de Chiapas, Eduardo J. Selvas S/N, Col. Magisterial, Tuxtla Gutierrez 29010, Chiapas (Mexico); Gomez Barojas, E. [CIDS-ICUAP, Apdo. Postal 1651, 72000 Puebla (Mexico); Silva Gonzalez, R.; Pal, U. [Instituto de Fisica, Benemerita Universidad Autonoma de Puebla, Puebla (Mexico)

    2007-09-22

    Effects of post formation thermal annealing of the CdTe-CdS device on the inter-diffusion of S and Te at the junction in a substrate configuration device have been studied by Auger electron spectroscopy. While the migration of S and Te atoms increases with annealing temperature, the extent of S diffusion is always higher than the diffusion of Te atoms. Inter-diffusion of S and Te causes the formation of CdTe{sub 1-x}S{sub x} ternary compound at the CdTe-CdS interface. (author)

  17. Study of CdTe and HgCdTe thin films obtained by electrochemical methods

    International Nuclear Information System (INIS)

    Guillen, C.

    1990-01-01

    Cadmium telluride polycrystalline thin films were fabricated on SnO 2 -coated glass substrates by potentiostatic electrodeposition and characterized by X-ray diffraction, energy dispersive X-ray analyses (EDAX), optical and electrical measurements. The films dseposited at potentials more positive than -0.65 V vs.SCE were p-type but those deposited at more negative potentials were n-type. All CdTe thin films showed a band-gap energy about 1.45 eV and a large absorption coeffici-ent (a=10 5 cm -1 ) above de band edge. The addition of even small amounts of mercury to the CdTe produces higuer conductivity values and lower band-gap energies. We have prepared HgCdTe thin films where the band-gap energies ranged between 0.93 and 0.88 eV depending on the ratio of mercury to cadmium. Heat treatment at 300 0 C increases the crystalline diameter and alter the composition of the electrodeposited films, a decrease of the resistivity values was also observed. (Author)

  18. Recycling of CdTe photovoltaic waste

    Science.gov (United States)

    Goozner, Robert E.; Long, Mark O.; Drinkard, Jr., William F.

    1999-01-01

    A method for extracting and reclaiming metals from scrap CdTe photovoltaic cells and manufacturing waste by leaching the waste with a leaching solution comprising nitric acid and water, skimming any plastic material from the top of the leaching solution, separating the glass substrate from the liquid leachate and electrolyzing the leachate to separate Cd from Te, wherein the Te is deposits onto a cathode while the Cd remains in solution.

  19. High mobility 2D electron gas in CdTe/CdMgTe heterostructures

    International Nuclear Information System (INIS)

    Karczewski, G.; Jaroszynski, J.; Kurowski, M.; Barcz, A.; Wojtowicz, T.; Kossut, J.

    1997-01-01

    We report on iodine doping of molecular beam epitaxy (MBE)-grown Cd(Mn)Te quasi-bulk films and modulation-doped CdTe/Cd 1-y Mg y Te two-dimensional (2D) single quantum well structures. Modulation doping with iodine of CdTe/Cd 1-y Mg y Te structures resulted in fabrication of a 2D electron gas with mobility exceeding 10 5 cm 2 /(Vs). This is the highest mobility reported in wide-gap II-VI materials

  20. Development of optimal SnO{sub 2} contacts for CdTe photovoltaic applications. [Final technical report of Phase II

    Energy Technology Data Exchange (ETDEWEB)

    Xi, Jianping

    1999-09-16

    During this SBIR Phase II project, we have successfully established high quality SnO{sub 2}(F) based transparent conductive oxide coatings by atmospheric pressure chemical vapor deposition technique and built a large area prototype APCVD deposition system which incorporates innovative design features. This work enhances US photovoltaic research capability and other thin film oxide related research capability.

  1. n-(CdMgTe/CdTe)/(p-(CdTe/ZnCdTe/ZnTe)/p-GaAs heterostructure diode for photosensor applications

    Science.gov (United States)

    Yahia, I. S.; AlFaify, S.; Abutalib, M. M.; Chusnutdinow, S.; Wojtowicz, T.; Karczewski, G.; Yakuphanoglu, F.; Al-Bassam, A.; El-Naggar, A. M.; El-Bashir, S. M.

    2016-05-01

    High quality n-(CdMgTe:I/n-CdTe:I)/(p-CdTe:N/p-ZnCdTe:N/p-ZnTe:N)/p-GaAs heterojunction diodes have been fabricated by molecular beam epitaxial growth. The illumination effect on the complex impedance and conductivity of heterostructure diode was investigated. The illumination intensities were taken up to the 200 mW/cm2 with frequency range of 42 Hz to 1 MHz. The observed real and imaginary parts of the complex impedance were strongly dependent on the illumination frequency. The inverse relation was observed between the illumination intensity and the complex impedance. The relaxation mechanism of the diode was analyzed by the Cole-Cole plots. The radius of the Cole-Cole curve decreases with increasing illumination intensity. This suggests a mechanism of illumination dependent on the relaxation process. It is also found that the conductivity increases linearly with increasing the illumination intensity. We can conclude that the new design heterostructure diode in our work is a good candidate in photodetector and optoelectronic applications.

  2. CdTe devices and method of manufacturing same

    Energy Technology Data Exchange (ETDEWEB)

    Gessert, Timothy A.; Noufi, Rommel; Dhere, Ramesh G.; Albin, David S.; Barnes, Teresa; Burst, James; Duenow, Joel N.; Reese, Matthew

    2015-09-29

    A method of producing polycrystalline CdTe materials and devices that incorporate the polycrystalline CdTe materials are provided. In particular, a method of producing polycrystalline p-doped CdTe thin films for use in CdTe solar cells in which the CdTe thin films possess enhanced acceptor densities and minority carrier lifetimes, resulting in enhanced efficiency of the solar cells containing the CdTe material are provided.

  3. Surface preparation effects on efficient indium-tin-oxide-CdTe and CdS-CdTe heterojunction solar cells

    Science.gov (United States)

    Werthen, J. G.; Fahrenbruch, A. L.; Bube, R. H.; Zesch, J. C.

    1983-05-01

    The effects of CdTe surface preparation and subsequent junction formation have been investigated through characterization of ITO/CdTe and CdS/CdTe heterojunction solar cells formed by electron beam evaporation of indium-tin-oxide (ITO) and CdS onto single crystal p-type CdTe. Surfaces investigated include air-cleaved (110) surfaces, bromine-in-methanol etched (110) and (111) surfaces, and teh latter surfaces subjected to a hydrogen heat treatment. Both air-cleaved and hydrogen heat treated surfaces have a stoichiometric Cd to Te ratio. The ITO/CdTe junction formation process involves an air heat treatment, which ahs serious effects on the behavior of junctions formed on these surfaces. Etched surfaces which have a large excesss of Te, are less affected by the junction formation process and result in ITO/CdTe heterojunctions with solar efficiencies of 9% (Vsc =20 mA/cm2). Use of low-doped CdTe results in junctions characterized by considerably larger open-circuit votages (Voc =0.81 V) which are attributable to increasing diode factors caused by a shift from interfacial recombination to recombination in the depletion region. Resulting solar efficiencies reach 10.5% which is the highest value reported to date for a genuine CdTe heterojunction, CdS/CdTe heterojunctions show a strong dependence on CdTe surface condition, but less influence on the junction formation process. Solar efficiencies of 7.5% on an etched and heat treated surface are observed. All of these ITO/CdTe and CdS/CdTe heterojunctions have been stable for at least 10 months.

  4. CdS/CdTe Solar Cells Containing Directly Deposited CdSxTe1-x Alloy Layers: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Duenow, J. N.; Dhere, R. G.; Moutinho, H. R.; To, B.; Pankow, J. W.; Kuciauskas, D.; Gessert, T. A.

    2011-07-01

    A CdSxTe1-x layer forms by interdiffusion of CdS and CdTe during the fabrication of thin-film CdTe photovoltaic (PV) devices. The CdSxTe1-x layer is thought to be important because it relieves strain at the CdS/CdTe interface that would otherwise exist due to the 10% lattice mismatch between these two materials. Our previous work [1] has indicated that the electrical junction is located in this interdiffused CdSxTe1-x region. Further understanding, however, is essential to predict the role of this CdSxTe1-x layer in the operation of CdS/CdTe devices. In this study, CdSxTe1-x alloy films were deposited by radio-frequency (RF) magnetron sputtering and co-evaporation from CdTe and CdS sources. Both RF-magnetron-sputtered and co-evaporated CdSxTe1-x films of lower S content (x<0.3) have a cubic zincblende (ZB) structure akin to CdTe, whereas those of higher S content have a hexagonal wurtzite (WZ) structure like that of CdS. Films become less preferentially oriented as a result of a CdCl2 heat treatment (HT) at ~400 degrees C for 5 min. Films sputtered in a 1% O2/Ar ambient are amorphous as deposited, but show CdTe ZB, CdS WZ, and CdTe oxide phases after a CdCl2 HT. Films sputtered in O2 partial pressure have a much wider bandgap than expected. This may be explained by nanocrystalline size effects seen previously [2] for sputtered oxygenated CdS (CdS:O) films. Initial PV device results show that the introduction of a directly-deposited CdSxTe1-x alloy layer into the device structure produces devices of comparable performance to those without the alloy layer when a CdCl2 HT is performed. Further investigation is required to determine whether the CdCl2 heat treatment step can be altered or eliminated through direct deposition of the alloy layer.

  5. CdS/CdTe Solar Cells Containing Directly-Deposited CdSxTe1-x Alloy Layers

    Energy Technology Data Exchange (ETDEWEB)

    Duenow, J. N.; Dhere, R. G.; Moutinho, H. R.; To, B.; Pankow, J. W.; Kuciauskas, D.; Gessert, T. A.

    2011-01-01

    A CdS{sub x}Te{sub 1-x} layer forms by interdiffusion of CdS and CdTe during the fabrication of thin-film CdTe photovoltaic (PV) devices. The CdS{sub x}Te{sub 1-x} layer is thought to be important because it relieves strain at the CdS/CdTe interface that would otherwise exist due to the 10% lattice mismatch between these two materials. Our previous work [1] has indicated that the electrical junction is located in this interdiffused CdS{sub x}Te{sub 1-x} region. Further understanding, however, is essential to predict the role of this CdS{sub x}Te{sub 1-x} layer in the operation of CdS/CdTe devices. In this study, CdS{sub x}Te{sub 1-x} alloy films were deposited by radio-frequency (RF) magnetron sputtering and co-evaporation from CdTe and CdS sources. Both RF-magnetron-sputtered and co-evaporated CdS{sub x}Te{sub 1-x} films of lower S content (x<;0.3) have a cubic zincblende (ZB) structure akin to CdTe, whereas those of higher S content have a hexagonal wurtzite (WZ) structure like that of CdS. Films become less preferentially oriented as a result of a CdCl{sub 2} heat treatment (HT) at {approx}400 C for 5 min. Films sputtered in a 1% O{sub 2}/Ar ambient are amorphous as deposited, but show CdTe ZB, CdS WZ, and CdTe oxide phases after a CdCl{sub 2} HT. Films sputtered in O{sub 2} partial pressure have a much wider bandgap than expected. This may be explained by nanocrystalline size effects seen previously [2] for sputtered oxygenated CdS (CdS:O) films. Initial PV device results show that the introduction of a directly-deposited CdS{sub x}Te{sub 1-x} alloy layer into the device structure produces devices of comparable performance to those without the alloy layer when a CdCl{sub 2} HT is performed. Further investigation is required to determine whether the CdCl{sub 2} heat treatment step can be altered or eliminated through direct deposition of the alloy layer.

  6. Application of regular associated solution model to the liquidus curves of the Sn-Te and Sn-SnS systems

    Science.gov (United States)

    Eric, H.

    1982-12-01

    The liquidus curves of the Sn-Te and Sn-SnS systems were evaluated by the regular associated solution model (RAS). The main assumption of this theory is the existence of species A, B and associated complexes AB in the liquid phase. Thermodynamic properties of the binary A-B system are derived by ternary regular solution equations. Calculations based on this model for the Sn-Te and Sn-SnS systems are in agreement with published data.

  7. Iodine Doping of CdTe and CdMgTe for Photovoltaic Applications

    Science.gov (United States)

    Ogedengbe, O. S.; Swartz, C. H.; Jayathilaka, P. A. R. D.; Petersen, J. E.; Sohal, S.; LeBlanc, E. G.; Edirisooriya, M.; Zaunbrecher, K. N.; Wang, A.; Barnes, T. M.; Myers, T. H.

    2017-09-01

    Iodine-doped CdTe and Cd1- x Mg x Te layers were grown by molecular beam epitaxy. Secondary ion mass spectrometry characterization was used to measure dopant concentration, while Hall measurement was used for determining carrier concentration. Photoluminescence intensity and time-resolved photoluminescence techniques were used for optical characterization. Maximum n-typ e carrier concentrations of 7.4 × 1018 cm-3 for CdTe and 3 × 1017 cm-3 for Cd0.65Mg0.35Te were achieved. Studies suggest that electrically active doping with iodine is limited with dopant concentration much above these values. Dopant activation of about 80% was observed in most of the CdTe samples. The estimated activation energy is about 6 meV for CdTe and the value for Cd0.65Mg0.35Te is about 58 meV. Iodine-doped samples exhibit long lifetimes with no evidence of photoluminescence degradation with doping as high as 2 × 1018 cm-3, while indium shows substantial non-radiative recombination at carrier concentrations above 5 × 1016 cm-3. Iodine was shown to be thermally stable in CdTe at temperatures up to 600°C. Results suggest iodine may be a preferred n-type dopant compared to indium in achieving heavily doped n-type CdTe.

  8. Production and characterization of CdTe films for CdS/CdTe solar cells

    International Nuclear Information System (INIS)

    Pal, A.K.; Chaudhuri, S.

    1988-01-01

    Cadmium telluride is considered as one of the most promising materials in the field of semiconductor devices due to its near ideal band gap for most efficient conversion of solar energy. It can also be prepared in both n and p type forms so that solar cell with homojunction or heterojunction configurations can be obtained. Earlier CdTe was mostly used in single crystal form for device fabrication. But the devices produced were not cost effective. The obvious answer to this problem is to opt for thin film technology for preparing device grade CdTe films. The fundamental problem of producing device grade CdTe films is associated with inherent high resistivity and a low carrier life time. The authors report, in this paper, studies on the CdTe films produced by hot wall vacuum evaporation. The films were deposited onto glass, molybdenum and single crystal NaCl substrates under various experimental conditions. The optimum values of the deposition parameters were uniquely determined to obtain best quality film for the fabrication of the solar cell. The stoichiometry of the film was tested

  9. Radiochemical neutron activation analysis for 36 elements in geological material: Au, Ag, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Sn, Te, Tl, U, and Zn as well as Sc, Y, and REE

    Energy Technology Data Exchange (ETDEWEB)

    Anders, E; Wolf, R; Morgan, J W; Ebihara, M; Woodrow, A B; Janssens, M J; Hertogen, J

    1988-01-01

    In lunar and terrestrial rocks and in meteorites, the radiochemical neutron activation method decribed here enables determination of the 21 trace and ultratrace elements Ag, Au, Bi, Br, Cd, Cs, Ga, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Te, Tl, U, Zn, as well as 13 rare earth elements (REE), Sc and Y. Materials, techniques and procedures are discussed. 81 refs.

  10. Characterization of normal and inverted interfaces by the Zeeman effect in Cd1-xMnxTe/CdTe/Cd1-yMgyTe quantum wells

    Science.gov (United States)

    Lemaitre, A.; Testelin, C.; Rigaux, C.; Maćkowski, S.; Khoi, Nguyen; Gaj, J. A.; Karczewski, G.; Wojtowicz, T.; Kossut, J.

    1998-02-01

    We present a study of the interface profile in asymmetric Cd1-xMnxTe/CdTe/Cd1-yMgyTe quantum wells, with normal (Cd1-xMnxTe on CdTe) and inverted (CdTe on Cd1-xMnxTe) interfaces. The Zeeman spectra of the confined exciton states were determined by magnetoreflectivity and Kerr rotation measurements. Using a segregation model and an asymmetric exponential profile, we interpret the Zeeman spectra of quantum wells, and determine the interface widths. For the same concentrations of Mn in the barriers and the same growth conditions, the results can be coherently explained assuming an interface width independent of the quantum-well width and the type of interface (normal or inverted).

  11. Optical phonons in PbTe/CdTe multilayer heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Novikova, N. N.; Yakovlev, V. A. [Russian Academy of Sciences, Institute for Spectroscopy (Russian Federation); Kucherenko, I. V., E-mail: kucheren@sci.lebedev.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Karczewski, G. [Polish Academy of Sciences, Institute of Physics (Poland); Aleshchenko, Yu. A.; Muratov, A. V.; Zavaritskaya, T. N.; Melnik, N. N. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2015-05-15

    The infrared reflection spectra of PbTe/CdTe multilayer nanostructures grown by molecular-beam epitaxy are measured in the frequency range of 20–5000 cm{sup −1} at room temperature. The thicknesses and high-frequency dielectric constants of the PbTe and CdTe layers and the frequencies of the transverse optical (TO) phonons in these structures are determined from dispersion analysis of the spectra. It is found that the samples under study are characterized by two TO phonon frequencies, equal to 28 and 47 cm{sup −1}. The first frequency is close to that of TO phonons in bulk PbTe, and the second is assigned to the optical mode in structurally distorted interface layers. The Raman-scattering spectra upon excitation with the radiation of an Ar{sup +} laser at 514.5 nm are measured at room and liquid-nitrogen temperatures. The weak line at 106 cm{sup −1} observed in these spectra is attributed to longitudinal optical phonons in the interface layers.

  12. Surface characterization of GSH-CdTe quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Gautier, J.L., E-mail: juan.gautier@usach.cl [Departamento de Química de los Materiales, Facultad de Química y Biología, Universidad de Santiago de Chile, Av. L. B. O' Higgins 3363, Santiago (Chile); Monrás, J.P. [Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Av. L. B. O' Higgins 3363, Santiago (Chile); Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Av. Vicuña Mackena 20, Santiago (Chile); Osorio-Román, I.O. [Departamento de Química Inorgánica, Facultad de Química, Pontificia Universidad Católica de Chile, Av. V. Mackenna 4860, Santiago (Chile); Vásquez, C.C. [Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Av. L. B. O' Higgins 3363, Santiago (Chile); Bravo, D. [Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Av. Vicuña Mackena 20, Santiago (Chile); Herranz, T.; Marco, J.F. [Instituto de Química Física “Rocasolano” CSIC, c/Serrano 119, 28006 Madrid (Spain); and others

    2013-06-15

    The surface characterization of CdTe QDs synthesized by a novel procedure using glutathione (GSH), low temperatures (60–90 °C) and K{sub 2}TeO{sub 3} as the –Te precursor is reported. Fluorescence of the produced QDs is stable in the pH range 6–13 and QDs inside eukaryotic cells are highly fluorescent. The surface composition of GSH-CdTe QDs with different spectroscopic properties and particle size distributions was determined by XPS. The XPS analysis indicated that the QDs are essentially CdTe, although all nanoparticles contain 12–24% of CdO (and in one case also TeO{sub 2}). GSH decomposes with reaction time releasing small amounts of S{sup −2} ions that react with Cd(Te) to yield Cd(Te)S in a smaller amount than that of CdTe. Finally, the use of QDs in fluorescence mediated immunodetection of bacterial pathogens has been evaluated. - Highlights: • Stable CdTe QDs of different sizes were synthesized by reacting thiol GSH and K{sub 2}TeO{sub 3} at 90 °C. • XPS analysis shows that the QDs contain CdTe, Cd(Te)S and CdO at the surface. • Small amounts of TeO{sub 2} were also observed. • Sulphur allows the binding of the QDs at biomolecules.

  13. Surface characterization of GSH-CdTe quantum dots

    International Nuclear Information System (INIS)

    Gautier, J.L.; Monrás, J.P.; Osorio-Román, I.O.; Vásquez, C.C.; Bravo, D.; Herranz, T.; Marco, J.F.

    2013-01-01

    The surface characterization of CdTe QDs synthesized by a novel procedure using glutathione (GSH), low temperatures (60–90 °C) and K 2 TeO 3 as the –Te precursor is reported. Fluorescence of the produced QDs is stable in the pH range 6–13 and QDs inside eukaryotic cells are highly fluorescent. The surface composition of GSH-CdTe QDs with different spectroscopic properties and particle size distributions was determined by XPS. The XPS analysis indicated that the QDs are essentially CdTe, although all nanoparticles contain 12–24% of CdO (and in one case also TeO 2 ). GSH decomposes with reaction time releasing small amounts of S −2 ions that react with Cd(Te) to yield Cd(Te)S in a smaller amount than that of CdTe. Finally, the use of QDs in fluorescence mediated immunodetection of bacterial pathogens has been evaluated. - Highlights: • Stable CdTe QDs of different sizes were synthesized by reacting thiol GSH and K 2 TeO 3 at 90 °C. • XPS analysis shows that the QDs contain CdTe, Cd(Te)S and CdO at the surface. • Small amounts of TeO 2 were also observed. • Sulphur allows the binding of the QDs at biomolecules

  14. CdTe and Cd1-xZnxTe for nuclear detectors: facts and fictions

    International Nuclear Information System (INIS)

    Fougeres, P.; Siffert, P.; Hageali, M.; Koebel, J.M.; Regal, R.

    1999-01-01

    Both CdTe and Cd 1-x Zn x Te (CZT) can be considered from their physical properties as very good materials for room temperature X- and γ-rays detection. However, despite years of intense material research, no significant advance has been made to help one to choose between both semiconductors. This paper reviews a few facts about CdTe and CZT to attempt to draw a real comparison between both. THM-CdTe and HPB-CZT have been grown and characterized in Strasbourg. Crystal growth, alloying effects, transport properties and defects are reviewed on the basis of our results and the published ones. The results show that it is still very difficult to claim which one is the best

  15. High performance p-i-n CdTe and CdZnTe detectors

    CERN Document Server

    Khusainov, A K; Ilves, A G; Morozov, V F; Pustovoit, A K; Arlt, R D

    1999-01-01

    A breakthrough in the performance of p-i-n CdTe and CdZnTe detectors is reported. The detector stability has been significantly improved, allowing their use in precise gamma and XRF applications. Detectors with energy resolution close to Si and Ge were produced operating with only -30--35 deg. C cooling (by a Peltier cooler of 15x15x10 mm size and a consumed power less than 5 W). Presently detectors with volume of up to 300 mm sup 3 are available. In terms of photoelectric effect efficiency it corresponds to HPGe detectors with volumes of about 1.5 cm sup 3. The possibilities of further improvement of CdTe and CdZnTe detector characteristics are discussed in this paper.

  16. Cubic Crystal-Structured SnTe for Superior Li- and Na-Ion Battery Anodes.

    Science.gov (United States)

    Park, Ah-Ram; Park, Cheol-Min

    2017-06-27

    A cubic crystal-structured Sn-based compound, SnTe, was easily synthesized using a solid-state synthetic process to produce a better rechargeable battery, and its possible application as a Sn-based high-capacity anode material for Li-ion batteries (LIBs) and Na-ion batteries (NIBs) was investigated. The electrochemically driven phase change mechanisms of the SnTe electrodes during Li and Na insertion/extraction were thoroughly examined utilizing various ex situ analytical techniques. During Li insertion, SnTe was converted to Li 4.25 Sn and Li 2 Te; meanwhile, during Na insertion, SnTe experienced a sequential topotactic transition to Na x SnTe (x ≤ 1.5) and conversion to Na 3.75 Sn and Na 2 Te, which recombined into the original SnTe phase after full Li and Na extraction. The distinctive phase change mechanisms provided remarkable electrochemical Li- and Na-ion storage performances, such as large reversible capacities with high Coulombic efficiencies and stable cyclabilities with fast C-rate characteristics, by preparing amorphous-C-decorated nanostructured SnTe-based composites. Therefore, SnTe, with its interesting phase change mechanisms, will be a promising alternative for the oncoming generation of anode materials for LIBs and NIBs.

  17. Surface passivation of HgCdTe by CdZnTe and its characteristics

    Science.gov (United States)

    Lee, T. S.; Choi, K. K.; Jeoung, Y. T.; Kim, H. K.; Kim, J. M.; Kim, Y. H.; Chang, J. M.; Song, W. S.; Kim, S. U.; Park, M. J.; Lee, S. D.

    1997-06-01

    In this paper, we report the results of capacitance-voltage measurements conducted on several metal-insulator semiconductor (MIS) capacitors in which HgCdTe surfaces are treated with various surface etching and oxidation processes. CdZnTe passivation layers were deposited on HgCdTe surfaces by thermal evaporation after the surfaces were etched with 0.5-2.0% bromine in methanol solution, or thin oxide layers (tox ˜ few ten Å) were grown on the surfaces, in order to investigate effects of the surface treatments on the electrical properties of the surfaces, as determined from capacitance-voltage (C-V) measurements at 80K and 1 MHz. A negative flat band voltage has been observed for MIS capacitors fabricated after etching of HgCdTe surfaces with bromine in methanol solutions, which is reported to make the surface Te-rich. It is inferred that residual Te on the surface is a positive charge, Te4+. C-V characteristics for MIS capacitors fabricated on oxide surfaces grown by air-exposure and electrolytic process have shown large hysteresis effects, from which it is inferred that imperfect and electrically active oxide compounds and HgTe particles near the surface become slow interface states.

  18. Nanoparticle precursor route to low-temperature spray deposition of CdTe thin films

    International Nuclear Information System (INIS)

    Pehnt, M.; Schulz, D.L.; Curtis, C.J.; Jones, K.M.; Ginley, D.S.

    1995-01-01

    In this letter we report a nanoparticle-derived route to CdTe thin films. CdTe nanoparticles 39±8 A in diameter, prepared by an organometallic route, were characterized by x-ray diffraction, UV-Vis spectroscopy, transmission electron microscopy, and energy dispersive x-ray spectroscopy. CdTe thin-film deposition was realized by spraying a nanoparticle/butanol colloid onto SnO 2 -coated glass substrates at variable susceptor temperatures. The resultant CdTe films were characterized by atomic force microscopy, x-ray diffraction, and UV-Vis spectroscopy. Smooth and dense CdTe thin films were obtained using growth temperatures ∼200 degree C less than conventional spray pyrolysis. A growth temperature dependence upon CdTe grain size formation and crystallinity was observed by atomic force microscopy and x-ray diffraction. UV-Vis characterization revealed a transformation in the optical properties of the CdTe thin films as a function of growth temperature. copyright 1995 American Institute of Physics

  19. Distribution of Te Inclusions in CdMnTe Crystal Grown by Traveling Heater Method

    Science.gov (United States)

    Lai, Jianming; Zhang, Jijun; Mao, Yifei; Lin, Liwen; Min, Jiahua; Liang, Xiaoyan; Huang, Jian; Tang, Ke; Wang, Linjun

    2018-02-01

    This study investigated Te inclusions in CdMnTe crystals grown by the traveling heater method (THM). Three CdMnTe ingots were grown under different growth temperatures of 850°C, 900°C, and 950°C by the THM method. In the CdMnTe ingots, the concentration of Te inclusion was lower in the middle-to-deposit part, and the size of Te inclusions kept growing till the last-to-deposit part. The concentrations of Te inclusions along the CdMnTe ingots were in the range of 104-106 cm-3, with the size in the range of 3-16 μm. CdMnTe crystals grown under 900°C had the lowest density and size of Te inclusion, due to the smooth and near-planar growth interface as revealed by infrared (IR) transmission microscopy. The relationship between the origin of Te inclusions and growth interface was analyzed during the THM growth of CdMnTe. IR transmission spectrometry was used to characterize Te inclusions in CdMnTe crystals. Current-voltage (I-V) and energy response measurements were carried out to reveal the resistivity (ρ) and energy resolution of CdMnTe detectors. The effects of Te inclusions on the optical and electrical properties of CdMnTe crystals for nuclear detector applications are discussed.

  20. Physical properties of electron beam evaporated CdTe and CdTe:Cu thin films

    Science.gov (United States)

    Punitha, K.; Sivakumar, R.; Sanjeeviraja, C.; Sathe, Vasant; Ganesan, V.

    2014-12-01

    In this paper, we report on physical properties of pure and Cu doped cadmium telluride (CdTe) films deposited onto corning 7059 microscopic glass substrates by electron beam evaporation technique. X-ray diffraction study showed that all the deposited films belong to amorphous nature. The average transmittance of the films is varied between 77% and 90%. The optical energy band gap of pure CdTe film is 1.57 eV and it decreased to 1.47 eV upon 4 wt. % of Cu addition, which may be due to the extension of localized states in the band structure. The refractive index of the films was calculated using Swanepoel method. It was observed that the dispersion data obeyed the single oscillator of the Wemple-Didomenico model, from which the dispersion energy (Ed) parameters, dielectric constants, plasma frequency, and oscillator energy (Eo) of CdTe and CdTe:Cu films were calculated and discussed in detail with the light of possible mechanisms underlying the phenomena. The variation in intensity of photoluminescence band edge emission peak observed at 820 nm with Cu dopant is due to the change in surface state density. The observed trigonal lattice of Te peaks in the micro-Raman spectra confirms the p-type conductive nature of films, which was further corroborated by the Hall effect measurement. The lowest resistivity of 6.61 × 104 Ω cm was obtained for the CdTe:Cu (3 wt. %) film.

  1. Multisegment CdTe nanowire homojunction photodiode

    International Nuclear Information System (INIS)

    Matei, Elena; Enculescu, Ionut; Ion, Lucian; Antohe, Stefan; Neumann, Reinhard

    2010-01-01

    Electrochemical deposition in nanoporous ion track membranes is used for the preparation of multisegment CdTe-homojunction diode nanowires. Our study is based on the fact that the deposition overpotential strongly influences the composition of the compound semiconductor nanowires. Therefore, the transport behavior of the nanowire devices can be tailored by appropriately choosing a certain sequence of electrodeposition potentials. The wires were characterized using scanning electron microscopy, energy dispersive x-ray analysis, optical spectroscopy and x-ray diffraction. The current-voltage characteristics measured prove that, by appropriately choosing the voltage pulse pattern, one can fabricate nanowires with ohmic or rectifying behavior. The semiconducting nanowires are sensitive to light, their spectral sensitivity being characteristic of CdTe. The preparation of functional nanostructures in such a simple approach provides, as a major advantage, an increase in the process reproducibility and opens a wide field of potential optoelectronic applications.

  2. Physical properties of Bi doped CdTe thin films grown by CSVT and their influence on the CdS/CdTe solar cells PV-properties

    International Nuclear Information System (INIS)

    Vigil-Galan, O.; Sanchez-Meza, E.; Ruiz, C.M.; Sastre-Hernandez, J.; Morales-Acevedo, A.; Cruz-Gandarilla, F.; Aguilar-Hernandez, J.; Saucedo, E.; Contreras-Puente, G.; Bermudez, V.

    2007-01-01

    The physical properties of Bi doped CdTe films, grown on glass substrates by the Closed Space Transport Vapour (CSVT) method, from different Bi doped CdTe powders are presented. The CdTe:Bi films were characterized using Photoluminescence, Hall effect, X-Ray diffraction, SEM and Photoconductivity measurements. Moreover, CdS/CdTe:Bi solar cells were made and their characteristics like short circuit current density (J sc ), open circuit voltage (V OC ), fill factor (FF) and efficiency (η) were determined. These devices were fabricated from Bi doped CdTe layers deposited on CdS with the same growth conditions than those used for the single CdTe:Bi layers. A correlation between the CdS/CdTe:Bi solar cell characteristics and the physical properties of the Bi doped CdTe thin films are presented and discussed

  3. TDPAC study of Cd-doped SnO

    Energy Technology Data Exchange (ETDEWEB)

    Munoz, E. L., E-mail: munoz@fisica.unlp.edu.ar [Universidad Nacional de La Plata, Departamento de Fisica-IFLP (CCT-La Plata, CONICET-UNLP), Facultad de Ciencias Exactas (Argentina); Carbonari, A. W. [Instituto de Pesquisas Energeticas y Nucleares-IPEN-CNEN/SP (Brazil); Errico, L. A. [Universidad Nacional de La Plata, Departamento de Fisica-IFLP (CCT-La Plata, CONICET-UNLP), Facultad de Ciencias Exactas (Argentina); Bibiloni, A. G. [Universidad Nacional de La Plata, Departamento de Fisica, Facultad de Ciencias Exactas (Argentina); Petrilli, H. M. [Universidade de Sao Paulo, Instituto de Fisica (Brazil); Renteria, M. [Universidad Nacional de La Plata, Departamento de Fisica-IFLP (CCT-La Plata, CONICET-UNLP), Facultad de Ciencias Exactas (Argentina)

    2007-07-15

    The combination of hyperfine techniques and ab initio calculations has been shown to be a powerful tool to unravel structural and electronic characterizations of impurities in solids. A recent example has been the study of Cd-doped SnO, where ab initio calculations questioned previous TDPAC assignments of the electric-field gradient (EFG) in {sup 111}In-implanted Sn-O thin films. Here we present new TDPAC experiments at {sup 111}In-diffused polycrystalline SnO. A reversible temperature dependence of the EFG was observed in the range 295-900 K. The TDPAC results were compared with theoretical calculations performed with the full-potential linearized augmented plane wave (FP-LAPW) method, in the framework of the density functional theory. Through the comparison with the theoretical results, we infer that different electronic surroundings around Cd impurities can coexist in the SnO sample.

  4. TDPAC study of Cd-doped SnO

    International Nuclear Information System (INIS)

    Munoz, E. L.; Carbonari, A. W.; Errico, L. A.; Bibiloni, A. G.; Petrilli, H. M.; Renteria, M.

    2007-01-01

    The combination of hyperfine techniques and ab initio calculations has been shown to be a powerful tool to unravel structural and electronic characterizations of impurities in solids. A recent example has been the study of Cd-doped SnO, where ab initio calculations questioned previous TDPAC assignments of the electric-field gradient (EFG) in 111 In-implanted Sn-O thin films. Here we present new TDPAC experiments at 111 In-diffused polycrystalline SnO. A reversible temperature dependence of the EFG was observed in the range 295-900 K. The TDPAC results were compared with theoretical calculations performed with the full-potential linearized augmented plane wave (FP-LAPW) method, in the framework of the density functional theory. Through the comparison with the theoretical results, we infer that different electronic surroundings around Cd impurities can coexist in the SnO sample.

  5. Growth of cubic and hexagonal CdTe thin films by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, S.K. [Solid State Physics Laboratory, Lucknow Road, Timarpur, Delhi 110 054 (India)]. E-mail: 628@ssplnet.org; Tiwari, Umesh [Solid State Physics Laboratory, Lucknow Road, Timarpur, Delhi 110 054 (India); Raman, R. [Solid State Physics Laboratory, Lucknow Road, Timarpur, Delhi 110 054 (India); Prakash, Chandra [Solid State Physics Laboratory, Lucknow Road, Timarpur, Delhi 110 054 (India); Krishna, Vamsi [Centre for Energy Studies, Indian Institute of Technology, New Delhi 110 016 (India); Dutta, Viresh [Centre for Energy Studies, Indian Institute of Technology, New Delhi 110 016 (India); Zimik, K. [Laser Science and Technology Centre, Metcalfe House, Delhi 110 054 (India)

    2005-02-01

    The paper reports the growth of cadmium telluride (CdTe) thin films by pulsed laser deposition (PLD) using excimer laser (KrF, {lambda}=248 nm, 10 Hz) on corning 7059 glass and SnO{sub 2}-coated glass (SnO{sub 2}/glass) substrates at different substrate temperatures (T{sub s}) and at different laser energy pulses. Single crystal target CdTe was used for deposition of thin films. With 30 min deposition time, 1.8- to {approx}3-{mu}m-thick films were obtained up to 200 deg. C substrate temperature. However, the film re-evaporates from the substrate surface at temperatures >275 deg. C. Atomic force microscopy (AFM) shows an average grain size {approx}0.3 {mu}m. X-ray diffraction analysis confirms the formation of CdTe cubic phase at all pulse energies except at 200 mJ. At 200 mJ laser energy, the films show hexagonal phase. Optical properties of CdTe were also investigated and the band gap of CdTe films were found as 1.54 eV for hexagonal phase and {approx}1.6 eV for cubic phase.

  6. CdTe-HgTe core-shell nanowire growth controlled by RHEED

    Science.gov (United States)

    Kessel, M.; Hajer, J.; Karczewski, G.; Schumacher, C.; Brüne, C.; Buhmann, H.; Molenkamp, L. W.

    2017-07-01

    We present results on the growth of CdTe-HgTe core-shell nanowires, a realization of a quasi-one-dimensional heterostructure of the topological insulator HgTe. The growth is a two step process consisting of the growth of single crystalline zinc blende CdTe nanowires with the vapor-liquid-solid method and the overgrowth of these wires with HgTe such that a closed shell is formed around the CdTe core structure. The CdTe wire growth is monitored by RHEED allowing us to infer information on the crystal properties from the electron diffraction pattern. This information is used to find and control the optimal growth temperature. High quality single crystal CdTe nanowires grow with a preferred orientation. For the growth of the conductive HgTe shell structure we find that the supplied Hg:Te ratio is the crucial parameter to facilitate growth on all surface facets.

  7. Study of Te Inclusions in CdMnTe Crystals for Nuclear Detector Applications

    International Nuclear Information System (INIS)

    Babalola, O.S.; Bolotnikov, A.; Groza, M.; Hossain, A.; Egarievwe, S.; James, R.; Burger, A.

    2009-01-01

    The concentration, size and spatial distribution of Te inclusions in the bulk of CdMnTe crystals mined from two batches of ingots were studied. An isolated planar layer decorated with Te inclusions was identified in CdMnTe crystals from the second ingot. The internal electric field of a CMT crystal was probed by infrared (IR) imaging employing Pockels electro-optic effect. The effect of an isolated plane of Te inclusions on the internal electric-field distribution within the CdMnTe crystal was studied. Space charge accumulation around the plane of Te inclusions was observed, which was found to be higher when the detector was reverse-biased. The effects of the plane of Te inclusions on the electric-field distribution within the CdMnTe crystal, and the quality of CdMnTe crystals for nuclear detector applications are discussed.

  8. Correction of diagnostic x-ray spectra measured with CdTe and CdZnTe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, M. [Osaka Univ., Suita (Japan). Medical School; Kanamori, H.; Toragaito, T.; Taniguchi, A.

    1996-07-01

    We modified the formula of stripping procedure presented by E. Di. Castor et al. We added the Compton scattering and separated K{sub {alpha}} radiation of Cd and Te (23 and 27keV, respectively). Using the new stripping procedure diagnostic x-ray spectra (object 4mm-Al) of tube voltage 50kV to 100kV for CdTe and CdZnTe detectors are corrected with comparison of those spectra for the Ge detector. The corrected spectra for CdTe and CdZnTe detectors coincide with those for Ge detector at lower tube voltage than 70kV. But the corrected spectra at higher tube voltage than 70kV do not coincide with those for Ge detector. The reason is incomplete correction for full energy peak efficiencies of real CdTe and CdZnTe detectors. (J.P.N.)

  9. HgCdTe at Teledyne

    Science.gov (United States)

    Tennant, W. E.; Arias, J. M.; Bajaj, J.

    2009-05-01

    Since the late '60's Teledyne Imaging Sensors (TIS-formerly Rockwell Science Center) has developed IR sensor technology and produced IR sensors for both military and commercial applications. In the late '70's, after excursions into the Pb-salts and InAsSb alloys, TIS began to study HgCdTe and has pursued this materials system aggressively ever since. Beginning with Te-corner liquid phase epitaxy (LPE) by dipping, tipping, and sliding, Teledyne migrated through metal organic chemical vapor deposition (MOCVD)-a very challenging growth technique-to molecular beam epitaxy (MBE), where we have found a reliable and flexible technique suited to the most advanced architectures. We used substrates from Cd(Zn)Te to sapphire, GaAs, and silicon. Ion implantation and planar diode architectures have allowed high density device geometries exploited in our double layer planar heterostructure (DLPH) single color diodes and our simultaneous multispectral integrated technology (SUMIT) two color diodes. The performance of these devices equals or exceeds that of all baseline MCT devices reported by other techniques. These devices have dark currents that are readily characterized over 13 orders of magnitude by a simple heuristic, "Rule 07," for a wide range of temperature and wavelength.

  10. Investigation of inter-diffusion in bilayer GeTe/SnSe phase change memory films

    International Nuclear Information System (INIS)

    Devasia, Archana; MacMahon, David; Raoux, Simone; Campbell, Kristy A.; Kurinec, Santosh K.

    2012-01-01

    A metal-chalcogenide layer, SnSe, is inserted between the memory layer GeTe and the top electrode to form a phase change memory cell. The GeTe layer exhibits ovonic threshold switching at a threshold field of ∼ 110 V/μm. For subsequent implementation into applications and reliability, material inter-diffusion and sublimation are examined in bilayer phase change films of GeTe/SnSe. Transmission electron microscopy and parallel electron energy loss spectroscopy analyses reveal Sn migration to the GeTe layer, which is responsible for lowering the rhombohedral to cubic structural transformation temperature in GeTe. Incongruent sublimation of SnSe and GeTe is observed at temperatures higher than 500 °C. Severe volatilization of Se results in the separation of a metallic Sn phase. The use of Al 2 O 3 as a capping layer has been found to mitigate these effects. - Highlights: ► In the as-deposited state, GeTe is amorphous and SnSe is orthorhombic in structure. ► After 300 °C, Sn migration results in the formation of a Ge x Sn 1−x Te solid solution. ► Film decomposition and incongruent sublimation are observed at high temperatures. ► A consequence of incongruent sublimation is the separation of metallic Sn phase. ► Al2O3 capping mitigates volatilization and Sn phase separation at high temperatures.

  11. Study of Cd Te recrystallization by hydrated-CdCl{sub 2} thermal treatment

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez V, C.; Albor A, M. L.; Galarza G, U.; Aguilar H, J. R. [IPN, Escuela Superior de Fisica y Matematicas, Departamento de Fisica, San Pedro Zacatenco, 07738 Ciudad de Mexico (Mexico); Gonzalez T, M. A. [IPN, Escuela Superior de Computo, Nueva Industrial Vallejo, 07738 Ciudad de Mexico (Mexico); Flores M, J. M. [IPN, Escuela Superior de Ingenieria Quimica e Industrias Extractivas, Departamento de Ingenieria en Metalurgia y Materiales, Nueva Industrial Vallejo, 07738 Ciudad de Mexico (Mexico); Jimenez O, D. [IPN, Escuela Superior de Ingenieria Mecanica y Electrica, SEPI, Nueva Industrial Vallejo, 07738 Ciudad de Mexico (Mexico)

    2017-11-01

    Cd Te thin films solar cells are currently produced using a layer sequence of glass/FTO/CdS/Cd Te/metal contact (Cu/Ag), these films are deposited by two different techniques, chemical bath deposition (CBD) and close space vapour transport (CSVT). In order to reach reasonable conversion efficiencies, the device has to be thermally treated in a hydrated-CdCl{sub 2} atmosphere. This study was carried out using X-ray diffraction (XRD), photoluminescence, Sem-EDS, four probe method and Sims profiling of Cd Te. These analyses confirm the presence of hydrated CdCl{sub 2} and Cd Te phases on Cd Te surface and shown a good recrystallization morphology helping to the carriers mobility along the structure. Using the thermal treatment was possible to reduce the resistivity of Cd Te thin film; it is a result to the Cl migration along the Cd Te solar cell structure, reducing the defects between CdS and Cd Te thin films. A strong Cd Te thin film recrystallization was observed by the implementation of a hydrated-CdCl{sub 2} treatment doing to this a good candidate to Cd Te solar cells process. (Author)

  12. SYNTHESIS AND CHARACTERIZATION OF CdTe QUANTUM ...

    African Journals Online (AJOL)

    Preferred Customer

    ABSTRACT. L-Cysteine (Cys)-capped CdTe quantum dots (QDs) were prepared when sodium tellurite worked as a tellurium source and sodium borohydride acted as a reductant. The influences of various experimental variables, including pH values, Cd/Te and Cd/Cys molar ratios, on the photoluminescence (PL) quantum ...

  13. Effects of current stressing on the p-Bi2Te3/Sn interfacial reactions

    International Nuclear Information System (INIS)

    Chan, Hsing-Ting; Lin, Chih-Fan; Yen, Yee-Wen; Chen, Chih-Ming

    2016-01-01

    The Sn/p-Bi 2 Te 3 /Sn sandwich-type sample was current stressed with a density of 150 A/cm 2 to investigate the effects of current stressing on the p-Bi 2 Te 3 /Sn interfacial reactions. Asymmetrical heating phenomenon was observed at the anodic Sn/p-Bi 2 Te 3 (50 °C) and cathodic p-Bi 2 Te 3 /Sn (120 °C) interfaces due to the Peltier effect. Besides the Peltier effect, the electromigration effect also influenced the growth of the SnTe phase and therefore polarity growth behavior was observed at the two interfaces. The growth of the SnTe phase at the cathodic p-Bi 2 Te 3 /Sn interface was accelerated because Peltier and electromigration effects drove more Sn atoms (dominant diffusion species) for the phase growth. By measuring the electromigration-induced atomic flux of Sn, the product of diffusivity and effective charge number (D × z*) was calculated to be 6.3 × 10 −9 cm 2 s −1 at 120 °C. - Highlights: • Sn/p-Bi 2 Te 3 /Sn sandwich-type sample is current stressed with a density of 150 A/cm 2 . • Passage of an electric current induces Peltier and electromigration effects. • Peltier effect causes asymmetrical heating at the anode and cathode interfaces. • Both effects accelerate the SnTe growth at the cathode interface. • Sn is the dominant diffusion species identified by a marker experiment.

  14. CdTe ambulatory ventricular function monitor

    International Nuclear Information System (INIS)

    Lazewatsky, J.L.; Alpert, N.M.; Moore, R.H.; Boucher, C.A.; Strauss, H.W.

    1979-01-01

    A prototype device consisting of two arrays of CdTe detectors, ECG amplifiers and gate, microprocessor, and tape recorder was devised to record simultaneous ECG and radionuclide blood pool data from the left ventricle for extended periods during normal activity. The device is intended to record information concerning both normal and abnormal physiology of the heart and to permit the evaluation of new pharmaceuticals under everyday conditions. Preliminary results indicate that the device is capable of recording and reading out data from both phantoms and patients

  15. Pixelated CdZnTe drift detectors

    DEFF Research Database (Denmark)

    Kuvvetli, Irfan; Budtz-Jørgensen, Carl

    2005-01-01

    A technique, the so-called Drift Strip Method (DSM), for improving the CdZnTe detector energy response to hard X-rays and gamma-rays was applied as a pixel geometry. First tests have confirmed that this detector type provides excellent energy resolution and imaging performance. We specifically...... report on the performance of 3 mm thick prototype CZT drift pixel detectors fabricated using material from eV-products. We discuss issues associated with detector module performance. Characterization results obtained from several prototype drift pixel detectors are presented. Results of position...

  16. Preliminary study of CdTe and CdTe:Cu thin films nanostructures deposited by using DC magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Marwoto, Putut; Made, D. P. Ngurah; Sugianto [Departement of Physics, Faculty of Mathematics and Natural Sciences, Universitas Negeri Semarang, Gunungpati, Semarang 50229 Jawa Tengah (Indonesia); Wibowo, Edy; Astuti, Santi Yuli; Aryani, Nila Prasetya [Materials Research Group, Laboratory of Thin Film, Department of Physics, Universitas Negeri Semarang, Gunungpati, Semarang 50229 Jawa Tengah (Indonesia); Othaman, Zulkafli [Departement of Physics, Universiti Teknologi Malaysia (UTM), Skudai, Johor Bahru (Malaysia)

    2013-09-03

    Growth and properties of CdTe and CdTe:Cu thin films nanostrucures deposited by using dc magnetron sputtering are reported. Scanning electron microscope (SEM) was used to observe the surface morphologies of the thin films. At growth conditions of 250 °C and 14 W, CdTe films did not yet evenly deposited. However, at growth temperature and plasma power of 325 °C and 43 W, both CdTe and CdTe:Cu(2%) have deposited on the substrates. In this condition, the morphology of the films indicate that the films have a grain-like nanostructures. Grain size diameter of about 200 nm begin to appear on top of the films. Energy Dispersive X-rays spectroscopy (EDX) was used to investigate chemical elements of the Cu doped CdTe film deposited. It was found that the film deposited consist of Cd, Te and Cu elements. XRD was used to investigate the full width at half maximum (FWHM) values of the thin films deposited. The results show that CdTe:Cu(2%) thin film has better crystallographic properties than CdTe thin film. The UV-Vis spectrometer was used to investigate the optical properties of thin films deposited. The transmittance spectra showed that transmittance of CdTe:Cu(2%) film is lower than CdTe film. It was found that the bandgap energy of CdTe and CdTe:Cu(2%) thin films of about 1.48 eV.

  17. HgCdTe photovoltaic detectors on Si substrates

    International Nuclear Information System (INIS)

    Zanio, K.R.; Bean, R.C.

    1988-01-01

    HgCdTe photovoltaic detectors have been fabricated on Si substrates through intermediate CdTe/GaAs layers. Encapsulation of the GaAs between the CdTe and Si prevents unintentional doping of the HgCdTe by Ga and As. Uniform epitaxial GaAs is grown on three inch diameter Si substrates. Detectors on such large area Si substrates will offer hybrid focal plane arrays whose dimensions are not limited by the difference between the coefficients of thermal expansion of the Si signal processor and the substrate for the HgCdTe detector array. The growth of HgCdTe detectors on the Si signal processors for monolithic focal plane arrays is also considered. 40 references

  18. Density of liquid Hg(1-x)Cd(x)Te

    Science.gov (United States)

    Chandra, D.; Holland, L. R.

    1983-01-01

    Negative thermal expansion has been established in liquid Hg(1-x)Cd(x)Te for x less than 0.2 employing a pycnometric method. Pure HgTe increases in density from its melting point at 670 C to a maximum value at 750 C, where normal thermal expansion progressively resumes. The dependence of density on temperature for liquid Hg(1-x)Cd(x)Te arises almost exclusively from the HgTe portion of the melt, while CdTe acts as a diluent. The temperature corresponding to the maximum density changes slightly with composition, increasing by about 5 C for x = 0.1.

  19. An optimized multilayer structure of CdS layer for CdTe solar cells application

    International Nuclear Information System (INIS)

    Han Junfeng; Liao Cheng; Jiang Tao; Spanheimer, C.; Haindl, G.; Fu, Ganhua; Krishnakumar, V.; Zhao Kui; Klein, A.; Jaegermann, W.

    2011-01-01

    Research highlights: → Two different methods to prepare CdS films for CdTe solar cells. → A new multilayer structure of window layer for the CdTe solar cell. → Thinner CdS window layer for the solar cell than the standard CdS layer. → Higher performance of solar cells based on the new multilayer structure. - Abstract: CdS layers grown by 'dry' (close space sublimation) and 'wet' (chemical bath deposition) methods are deposited and analyzed. CdS prepared with close space sublimation (CSS) has better crystal quality, electrical and optical properties than that prepared with chemical bath deposition (CBD). The performance of CdTe solar cell based on the CSS CdS layer has higher efficiency than that based on CBD CdS layer. However, the CSS CdS suffers from the pinholes. And consequently it is necessary to prepare a 150 nm thin film for CdTe/CdS solar cell. To improve the performance of CdS/CdTe solar cells, a thin multilayer structure of CdS layer (∼80 nm) is applied, which is composed of a bottom layer (CSS CdS) and a top layer (CBD CdS). That bi-layer film can allow more photons to pass through it and significantly improve the short circuit current of the CdS/CdTe solar cells.

  20. Homogeneous CdTe quantum dots-carbon nanotubes heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Vieira, Kayo Oliveira [Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, CEP 36301-160, São João del-Rei, MG (Brazil); Bettini, Jefferson [Laboratório Nacional de Nanotecnologia, Centro Nacional de Pesquisa em Energia e Materiais, CEP 13083-970, Campinas, SP (Brazil); Ferrari, Jefferson Luis [Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, CEP 36301-160, São João del-Rei, MG (Brazil); Schiavon, Marco Antonio, E-mail: schiavon@ufsj.edu.br [Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, CEP 36301-160, São João del-Rei, MG (Brazil)

    2015-01-15

    The development of homogeneous CdTe quantum dots-carbon nanotubes heterostructures based on electrostatic interactions has been investigated. We report a simple and reproducible non-covalent functionalization route that can be accomplished at room temperature, to prepare colloidal composites consisting of CdTe nanocrystals deposited onto multi-walled carbon nanotubes (MWCNTs) functionalized with a thin layer of polyelectrolytes by layer-by-layer technique. Specifically, physical adsorption of polyelectrolytes such as poly (4-styrene sulfonate) and poly (diallyldimethylammonium chloride) was used to deagglomerate and disperse MWCNTs, onto which we deposited CdTe quantum dots coated with mercaptopropionic acid (MPA), as surface ligand, via electrostatic interactions. Confirmation of the CdTe quantum dots/carbon nanotubes heterostructures was done by transmission and scanning electron microscopies (TEM and SEM), dynamic-light scattering (DLS) together with absorption, emission, Raman and infrared spectroscopies (UV–vis, PL, Raman and FT-IR). Almost complete quenching of the PL band of the CdTe quantum dots was observed after adsorption on the MWCNTs, presumably through efficient energy transfer process from photoexcited CdTe to MWCNTs. - Highlights: • Highly homogeneous CdTe-carbon nanotubes heterostructures were prepared. • Simple and reproducible non-covalent functionalization route. • CdTe nanocrystals homogeneously deposited onto multi-walled carbon nanotubes. • Efficient energy transfer process from photoexcited CdTe to MWCNTs.

  1. CuTe Nanoparticles/Carbon Nanotubes as Back Contact for CdTe Solar Cells

    Science.gov (United States)

    Li, Chunxiu; Xu, Hang; Li, Kang; Ma, Xiao; Wu, Lili; Wang, Wenwu; Zhang, Jingquan; Li, Wei; Li, Bing; Feng, Lianghuan

    2018-02-01

    The Schottky barrier between the CdTe layer and metal electrode has opposite polarity to the CdS/CdTe cell junction, which can greatly degrade cell performance. Adding a back contact (BC) layer can reduce the Schottky barrier at metal/ p-CdTe interfaces. Paste including CuTe nanoparticles and carbon nanotubes (CuTe NPs/CNTs) was used as a BC in thin-film CdTe solar cells. The effect of the mass of carbon nanotubes (CNTs) in the paste and the BC annealing temperature on cell performance was explored. Cu film and paste including Cu nanoparticles and carbon nanotubes (Cu NPs/CNTs) were fabricated as the BC for CdTe solar cells. The performance of CdTe solar cells based on different kinds of Cu-containing BCs studied. The fill factor and open-circuit voltage ( V OC) of devices with CuTe NPs/CNTs BC were greatly improved by optimizing the mass of CNTs in the paste and the annealing temperature. The carrier concentration in the CdTe layer was improved by one order of magnitude. The CuTe NPs/CNTs BC showed the best effect on cell efficiency for the Cu-containing BC.

  2. Response of Cds/CdTe Devices to Te Exposure of Back Contact: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Gessert, T. A.; Burst, J. M.; Ma, J.; Wei, S. H.; Kuciauskas, D.; Barnes, T. M.; Duenow, J. N.; Young, M. R.; Rance, W. L.; Li, J. V.; Dippo, P.

    2012-06-01

    Theoretical predictions of thin-film CdS/CdTe photovoltaic (PV) devices have suggested performance may be improved by reducing recombination due to Te-vacancy (VTe) or Te-interstitial (Tei) defects. Although formation of these intrinsic defects is likely influenced by CdTe deposition parameters, it also may be coupled to formation of beneficial cadmium vacancy (VCd) defects. If this is true, reducing potential effects of VTe or Tei may be difficult without also reducing the density of VCd. In contrast, post-deposition processes can sometimes afford a greater degree of defect control. Here we explore a post-deposition process that appears to influence the Te-related defects in polycrystalline CdTe. Specifically, we have exposed the CdTe surface to Te prior to ZnTe:Cu/Ti contact-interface formation with the goal of reducing VTe but without significantly reducing VCd. Initial results show that when this modified contact is used on a CdCl2-treated CdS/CdTe device, significantly poorer device performance results. This suggests two things: First, the amount of free-Te available during contact formation (either from chemical etching or CuTe or ZnTe deposition) may be a more important parameter to device performance than previously appreciated. Second, if processes have been used to reduce the effect of VTe (e.g., oxygen and chlorine additions to the CdTe), adding even a small amount of Te may produce detrimental defects.

  3. Characterization and photoluminescence studies of CdTe ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. The major objective of this work was to detect the change of photoluminescence (PL) intensity of. CdTe nanoparticles (NPs) before and after transfer from liquid phase to polystyrene (PS) matrix by electro- spinning technique. Thio-stabilized CdTe NPs were first synthesized in aqueous, then enwrapped by cetyl-.

  4. Preparation and performance of thin film CdTe mini-module

    Energy Technology Data Exchange (ETDEWEB)

    Jingquan, Zhang; Lianghuan, Feng; Zhi, Lei; Yaping, Cai; Wei, Li; Lili, Wu; Bing, Li; Wei, Cai; Jiagui, Zheng [College of Materials Science and Engineering, Sichuan University, Chengdu, Sichuan 610064 (China)

    2009-06-15

    The film deposition process and integrated technology of the CdTe mini-module with high efficiency are key steps to manufacture large-area modules. In this paper, CdS, CdTe and ZnTe:Cu films with a substrate area of 7 x 10 cm{sup 2} were deposited by chemical bath deposition, close-spaced sublimation and vacuum co-evaporation, respectively. The uniform films were prepared after their thicknesses, structures and electronic characteristics were studied as the function of deposition parameters. The films of SnO{sub 2}:F, CdTe, etc, were scribed by Kr-lamp-pumped Q-switch YAG:Nd laser. The pumped lamp current, Q-switch frequency and scribing rate were optimized. The scribing efficiency of the base frequency light was compared with that of doubled frequency light. The integrated structure design was optimized after simulating. Then the CdTe mini-module of 7.03% efficiency was gained with a total area of 54 cm{sup 2} and nine integrated elementary cells. (author)

  5. Performance optimization of CdTe and CdZnTe detectors for γ-spectrometry

    International Nuclear Information System (INIS)

    Montemont, Guillaume

    2000-01-01

    This study deals with room-temperature gamma spectrometry with CdTe and CdZnTe semiconductor detectors. The aim was the improvement of energy resolution and detection efficiency. Some different phenomena have been investigated. Electronic noise knowledge has enabled us to optimize the design of filtering. Charge transport induces signal shape uncertainty and the processing circuit has been adapted in order to account for these variations. Study and simulation of electrical current induction process has permitted the development of a new Frisch-grid based detection structure. We have reached 3% energy resolutions at 122 keV without detection efficiency loss. Finally, the remaining limits of detector performances have been estimated by focusing on gamma interaction phenomena and material non-uniformity problems. (author) [fr

  6. Synthesis of near-infrared-emitting CdTe/CdSe/ZnSe/ZnS heterostructure.

    Science.gov (United States)

    Yang, Ping

    2014-04-01

    Near-infrared-emitting quantum dots (QDs) were fabricated via organic synthesis strategies through constructing CdTe/CdSe/ZnSe/ZnS multishell heterostructure. An effective shell-coating route was developed for multishell growth on CdTe cores. Core/shell growth was monitored by absorption and photoluminescence (PL) spectroscopy and transmission electron microscopy observation. Yellow emitting CdTe cores were coated with a CdSe shell to generate type II structure. This yields core/shell QDs with red photoluminescence. The passivation by the ZnSe shell having a substantially wide bandgap confines the excitons within the CdTe/CdSe interface and isolates them from the solution environment and consequently improves the stability of the heterostructure. An additional ZnS shell was deposited around the outer layer of CdTe/CdSe/ZnSe QDs to form a heterostructure through the reaction between zinc oleate and trioctylphosphine sulfur in the crude CdTe/CdSe/ZnSe solution. By varying CdTe core size and each shell thickness, the PL wavelength of the obtained heterostructure can span from 580 to 770 nm. The PL efficiency is quenched in CdTe QDs in diluted solution but increases substantially up to 24% for CdTe/CdSe core/shell QDs. The PL efficiency of CdTe/CdSe/ZnSe/ZnS QDs with average diameter of 5.4 nm and a PL peak wavelength of 770 nm is 20%.

  7. Growth of CdTe: Al films; Crecimiento de peliculas de CdTe: Al

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez A, M.; Zapata T, M. [CICATA-IPN, 89600 Altamira, Tamaulipas (Mexico); Melendez L, M. [CINVESTAV-IPN, A.P. 14-740, 07000 Mexico D.F. (Mexico); Pena, J.L. [CINVESTAV-IPN, A.P. 73 Cordemex, 97310 Merida, Yucatan (Mexico)

    2006-07-01

    CdTe: AI films were grown by the close space vapor transport technique combined with free evaporation (CSVT-FE). The Aluminum (Al) evaporation was made by two kinds of sources: one made of graphite and the other of tantalum. The films were deposited on glass substrates. The Al source temperature was varied maintaining the CdTe source temperature fixed as well as the substrate temperature. The films were characterized by x-ray energy dispersive analysis (EDAX), x-ray diffraction and optical transmission. The results showed for the films grown with the graphite source for Al evaporation, the Al did not incorporate in the CdTe matrix, at least to the level of EDAX sensitivity; they maintained the same crystal structure and band gap. For the samples grown with the tantalum source, we were able to incorporate the Al. The x-ray diffraction patterns show that the films have a crystal structure that depends on Al concentration. They were cubic up to 2.16 at. % Al concentration; for 19.65 at. % we found a mixed phase; for Al concentration higher than 21 at. % the films were amorphous. For samples with cubic structure it was found that the lattice parameter decreases and the band gap increases with Al concentration. (Author)

  8. Electrophysical properties of nCdS/pCdTe heterosystem

    International Nuclear Information System (INIS)

    Muzafarova, S.A.

    2006-01-01

    Full text: In this work results of research of electrophysical properties n CdS/pCdTe heterostructure are given. It is shown that at density of current 10 -8 -10 -5 A.cm -2 vol tamper characteristics in hetero system CdTe/CdS is described by thermo ionic law, and in the range 10 -4 -10 -2 A .cm -2 the current in heterostructure is limited by recombination in electronic neutral part of high-resistance of solid structure CdTe 1-x S x . Certain life time τ p and length of diffusion L p of non basic current carriers in solid structure CdTe 1-x S x , as well as superficial recombination rate v R on border of section between CdS and solid structures were considered at influence of irradiation and γ-quanta on the mechanism of current in n CdS/pCdTe heterostructure. From the analysis of dependence doze of sites the direct volt-ampere characteristics were obtained. It is shown that monotonous increase of doze of irradiation and γ-quanta leads to nonmonotonous change of micro parameters of nCdS/pCdTe heterostructure, superficial recombination rate - v R , values of both τ p and lengths of diffusion L p of non basic carriers of potential barrier - qφ B . On border of CdTe 1-x S x there is CdS-solid structure. (author)

  9. Synthesis and characterization of Sn-doped CdZnS nanoparticles

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Tin (Sn)-doped cadmium zinc sulphide nanoparticles (CdZnS : Sn) were synthesized by the chemi- cal bath deposition method with two different concentrations of Sn (2 and 4 mol%). X-ray diffraction (XRD) pattern reveals the formation of CdZnS nanoparticles with cubic and hexagonal structure. It was observed ...

  10. Synthesis and characterization of Sn-doped CdZnS nanoparticles

    Indian Academy of Sciences (India)

    Tin (Sn)-doped cadmium zinc sulphide nanoparticles (CdZnS : Sn) were synthesized by the chemical bath deposition method with two different concentrations of Sn (2 and 4 mol%). X-ray diffraction (XRD) pattern reveals the formation of CdZnS nanoparticles with cubic and hexagonal structure. It was observed that the ...

  11. Te inclusion-induced electrical field perturbation in CdZnTe single crystals revealed by Kelvin probe force microscopy.

    Science.gov (United States)

    Gu, Yaxu; Jie, Wanqi; Li, Linglong; Xu, Yadong; Yang, Yaodong; Ren, Jie; Zha, Gangqiang; Wang, Tao; Xu, Lingyan; He, Yihui; Xi, Shouzhi

    2016-09-01

    To understand the effects of tellurium (Te) inclusions on the device performance of CdZnTe radiation detectors, the perturbation of the electrical field in and around Te inclusions was studied in CdZnTe single crystals via Kelvin probe force microscopy (KPFM). Te inclusions were proved to act as lower potential centers with respect to surrounding CdZnTe matrix. Based on the KPFM results, the energy band diagram at the Te/CdZnTe interface was established, and the bias-dependent effects of Te inclusion on carrier transportation is discussed. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. 13.9%-efficient CdTe polycrystalline thin-film solar cells with an infrared transmission of {approx} 50%

    Energy Technology Data Exchange (ETDEWEB)

    Wu, X.; Zhou, J.; Duda, A.; Keane, J.C.; Gessert, T.A.; Yan, Y.; Noufi, R. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2005-07-01

    To fabricate a high-efficiency polycrystalline thin-film tandem cell, the most critical work is to make a high-efficiency top cell ( > 15%) with high bandgap (E{sub g} = 1.5-1.8 eV) and high transmission (T > 70%) in the near-infrared (NIR) wavelength region. The CdTe cell is one of the candidates for the top cell, because CdTe state-of-the-art single-junction devices with efficiencies of more than 16% are available, although its bandgap (1.48 eV) is slightly lower for a top cell in a current-matched dual-junction device. In this paper, we focus on the development of a: (1) thin, low-bandgap Cu{sub x}Te transparent back-contact; and (2) modified CdTe device structure, including three novel materials: cadmium stannate transparent conducting oxide (TCO), ZnSnO{sub x} buffer layer, and nanocrystalline CdS:O window layer developed at NREL, as well as the high-quality CdTe film, to improve transmission in the NIR region while maintaining high device efficiency. We have achieved an NREL-confirmed 13.9%-efficient CdTe transparent solar cell with an infrared transmission of {approx}50% and a CdTe/CIS polycrystalline mechanically stacked thin-film tandem cell with an NREL-confirmed efficiency of 15.3%. (Author)

  13. Aqueous synthesis of glutathione-capped CdTe/CdS/ZnS and CdTe/CdSe/ZnS core/shell/shell nanocrystal heterostructures.

    Science.gov (United States)

    Samanta, Anirban; Deng, Zhengtao; Liu, Yan

    2012-05-29

    Here we demonstrate the aqueous synthesis of colloidal nanocrystal heterostructures consisting of the CdTe core encapsulated by CdS/ZnS or CdSe/ZnS shells using glutathione (GSH), a tripeptide, as the capping ligand. The inner CdTe/CdS and CdTe/CdSe heterostructures have type-I, quasi-type-II, or type-II band offsets depending on the core size and shell thickness, and the outer CdS/ZnS and CdSe/ZnS structures have type-I band offsets. The emission maxima of the assembled heterostructures were found to be dependent on the CdTe core size, with a wider range of spectral tunability observed for the smaller cores. Because of encapsulation effects, the formation of successive shells resulted in a considerable increase in the photoluminescence quantum yield; however, identifying optimal shell thicknesses was required to achieve the maximum quantum yield. Photoluminescence lifetime measurements revealed that the decrease in the quantum yield of thick-shell nanocrystals was caused by a substantial decrease in the radiative rate constant. By tuning the diameter of the core and the thickness of each shell, a broad range of high quantum yield (up to 45%) nanocrystal heterostructures with emission ranging from visible to NIR wavelengths (500-730 nm) were obtained. This versatile route to engineering the optical properties of nanocrystal heterostructures will provide new opportunities for applications in bioimaging and biolabeling.

  14. CdTe Photovoltaics for Sustainable Electricity Generation

    Science.gov (United States)

    Munshi, Amit; Sampath, Walajabad

    2016-09-01

    Thin film CdTe (cadmium telluride) is an important technology in the development of sustainable and affordable electricity generation. More than 10 GW of installations have been carried out using this technology around the globe. It has been demonstrated as a sustainable, green, renewable, affordable and abundant source of electricity. An advanced sublimation tool has been developed that allows highly controlled deposition of CdTe films onto commercial soda lime glass substrates. All deposition and treatment steps can be performed without breaking the vacuum within a single chamber in an inline process that can be conveniently scaled to a commercial process. In addition, an advanced cosublimation source has been developed to allow the deposition of ternary alloys such as Cd x Mg1- x Te to form an electron reflector layer which is expected to address the voltage deficits in current CdTe devices and to achieve very high efficiency. Extensive materials characterization, including but not limited to scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, high resolution transmission electron microscopy and electron back-scatter diffraction, has been performed to get a better understanding of the effects of processing conditions on CdTe thin film photovoltaics. This combined with computer modeling such as density function theory modeling gives a new insight into the mechanism of CdTe photovoltaic function. With all these efforts, CdTe photovoltaics has seen great progress in the last few years. Currently, it has been recorded as the cheapest source of electricity in the USA on a commercial scale, and further improvements are predicted to further reduce the cost while increasing its utilization. Here, we give an overview of the advantages of thin film CdTe photovoltaics as well as a brief review of the challenges that need to be addressed. Some fundamental studies of processing conditions for thin film CdTe are also presented

  15. Characteristics of CdTe nanocrystals synthesized by a Na2TeO3 source

    International Nuclear Information System (INIS)

    Wang Meiping; Fu Kai; Lin Jinhui

    2011-01-01

    Water-soluble cadmium telluride (CdTe) nanocrystals were synthesized in aqueous solution with thioglycolic acid (TGA) molecules as a stabilizer. A series of TGA-stabilized CdTe nanocrystals were prepared using sodium tellurite as a tellurium source, which avoids the cumbersome processes associated with H 2 Te or NaHTe sources. The synthesized TGA-stabilized CdTe were characterized with X-ray diffraction, TEM and fluorescence spectrophotometer. The particles crystallized predominantly in cubic phase with narrow photoluminescence emission. The effects of reaction time, pH value, and precursor concentration on the photoluminescence properties were investigated in detail. (semiconductor materials)

  16. Process Development for High Voc CdTe Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Ferekides, C. S.; Morel, D. L.

    2011-05-01

    This is a cumulative and final report for Phases I, II and III of this NREL funded project (subcontract # XXL-5-44205-10). The main research activities of this project focused on the open-circuit voltage of the CdTe thin film solar cells. Although, thin film CdTe continues to be one of the leading materials for large-scale cost-effective production of photovoltaics, the efficiency of the CdTe solar cells have been stagnant for the last few years. This report describes and summarizes the results for this 3-year research project.

  17. Recent state of CdTe-based radiation detectors

    International Nuclear Information System (INIS)

    Ohno, R.

    2004-01-01

    Recent state for development of CdTe-based radiation detectors is reviewed. The progress of the technologies such as the crystal growth of CdTe and CdZnTe, the deposition of electrodes on the crystal, the design of read out ASIC, and the bonding between crystal and ASIC, opened the way for the development of imaging devices for practical uses. A X-ray imager for non destructive inspections and a gamma ray imager for small animal radioisotope experiments or nuclear medicine are presented as examples. (author)

  18. Properties of Hg1-xCdxTe epitaxial films grown on (211)CdTe and (211)CdZnTe

    International Nuclear Information System (INIS)

    Di Stefano, M.C.; Gilabert, U.; Heredia, E.; Trigubo, A.B.

    2004-01-01

    Hg 1-x Cd x Te (MCT) epitaxial films have been grown employing single crystalline substrates of CdTe and Cd 0.96 Zn 0.04 Te with (211)Cd and (211)Te crystalline orientations. The Isothermal Vapor Phase Epitaxy (ISOVPE) technique without Hg overpressure has been used for the epitaxial growth. Substrates and films were characterized by optical microscopy, chemical etching and X ray diffraction (Laue technique). The electrical properties were determined by Hall effect measurements. The characterization results allowed to evaluate the crystalline quality of MCT films. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Thermoelectric Properties of Cu2HgSnSe4-Cu2HgSnTe4 Solid Solution

    Czech Academy of Sciences Publication Activity Database

    Navrátil, Jiří; Kucek, V.; Plecháček, T.; Černošková, E.; Laufek, František; Drašar, Č.; Knotek, P.

    2014-01-01

    Roč. 43, č. 10 (2014), s. 3719-3725 ISSN 0361-5235 R&D Projects: GA ČR GA13-33056S Institutional support: RVO:61389013 ; RVO:68378271 Keywords : quaternary diamond-like compounds * Cu2HgSnSe4 * Cu2HgSnTe4 Subject RIV: CA - Inorganic Chemistry Impact factor: 1.798, year: 2014

  20. Electrochemical study of CdS/CdTe solar cells prepared by electrochemical deposition

    International Nuclear Information System (INIS)

    Delmas, V.; Llabres, J.

    1985-01-01

    The growth conditions of thin films of cadmium telluride, using the electrochemical deposition technique, for the production of p-CdTe/n-CdS heterojunction solar cells are presented in this communication. Special attention is paid to the examination of parameters controlling and limiting the growth of CdTe samples presenting one or other type of majority change carriers. Voltammograms were performed under different conditions for growth mechanism determination. In particular, the growth kinetic function on stainless steel and cadmium sulfide substrates is shown. Heterojunctions were prepared by electrochemically depositing CdTe (type P) on CdS thin films, deposited in high vacuum. The aim of this study is characterization of low cost production of CdS/CdTe heterojunctions solar cells by electrochemical deposition

  1. Characterization and photoluminescence studies of CdTe ...

    Indian Academy of Sciences (India)

    SEM) and transmission electron microscope (TEM) to observe their morphology and distribution, respectively. The selective area electronic diffraction (SAED) pattern proved that the CdTe NPs were cubic lattice. The PL spectrum indicated that ...

  2. Interaction of porphyrins with CdTe quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xing; Liu Zhongxin; Ma Lun; Hossu, Marius; Chen Wei, E-mail: weichen@uta.edu [Department of Physics, University of Texas at Arlington, Box 19059 Arlington, TX 76019 (United States)

    2011-05-13

    Porphyrins may be used as photosensitizers for photodynamic therapy, photocatalysts for organic pollutant dissociation, agents for medical imaging and diagnostics, applications in luminescence and electronics. The detection of porphyrins is significantly important and here the interaction of protoporphyrin-IX (PPIX) with CdTe quantum dots was studied. It was observed that the luminescence of CdTe quantum dots was quenched dramatically in the presence of PPIX. When CdTe quantum dots were embedded into silica layers, almost no quenching by PPIX was observed. This indicates that PPIX may interact and alter CdTe quantum dots and thus quench their luminescence. The oxidation of the stabilizers such as thioglycolic acid (TGA) as well as the nanoparticles by the singlet oxygen generated from PPIX is most likely responsible for the luminescence quenching. The quenching of quantum dot luminescence by porphyrins may provide a new method for photosensitizer detection.

  3. Advances in CdTe R&D at NREL

    Energy Technology Data Exchange (ETDEWEB)

    Wu, X.; Zhou, J.; Keane, J. C.; Dhere, R. G.; Albin, D. S.; Gessert, T. A.; DeHart, C.; Duda, A.; Ward, J. J.; Yan, Y.; Teeter, G.; Levi, D. H.; Asher, S.; Perkins, C.; Moutinho, H. R.; To, B.

    2005-11-01

    This paper summarizes the following R&D accomplishments at National Renewable Energy Laboratory (NREL): (1) Developed several novel materials and world-record high-efficiency CdTe solar cell, (2) Developed "one heat-up step" manufacturing processes, and (3) Demonstrated 13.9% transparent CdTe cell and 15.3% CdTe/CIS polycrystalline tandem solar cell. Cadmium telluride has been well recognized as a promising photovoltaic material for thin-film solar cells because of its near-optimum bandgap of ~1.5 eV and its high absorption coefficient. Impressive results have been achieved in the past few years for polycrystalline CdTe thin-film solar cells at NREL. In this paper, we summarize some recent R&D activities at NREL.

  4. Interaction of porphyrins with CdTe quantum dots

    International Nuclear Information System (INIS)

    Zhang Xing; Liu Zhongxin; Ma Lun; Hossu, Marius; Chen Wei

    2011-01-01

    Porphyrins may be used as photosensitizers for photodynamic therapy, photocatalysts for organic pollutant dissociation, agents for medical imaging and diagnostics, applications in luminescence and electronics. The detection of porphyrins is significantly important and here the interaction of protoporphyrin-IX (PPIX) with CdTe quantum dots was studied. It was observed that the luminescence of CdTe quantum dots was quenched dramatically in the presence of PPIX. When CdTe quantum dots were embedded into silica layers, almost no quenching by PPIX was observed. This indicates that PPIX may interact and alter CdTe quantum dots and thus quench their luminescence. The oxidation of the stabilizers such as thioglycolic acid (TGA) as well as the nanoparticles by the singlet oxygen generated from PPIX is most likely responsible for the luminescence quenching. The quenching of quantum dot luminescence by porphyrins may provide a new method for photosensitizer detection.

  5. Characterization and photoluminescence studies of CdTe ...

    Indian Academy of Sciences (India)

    Administrator

    (PS), an inert polymer, is utilized in many research works. Then, it may be an attractive topic to disperse. CdTe NPs into PS matrix in order to generate a novel ... The CdTe/PS mixture was filled to an acutilingual glass tube wrapped with copper wire, which was con- nected with a 12 kV positive d.c. A grounded aluminum.

  6. Nonlinear terahertz response of HgTe/CdTe quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Qinjun [School of Physics and Electronics, Hunan University, Changsha 410082 (China); School of Physics, University of Wollongong, Wollongong, New South Wales 2522 (Australia); Sanderson, Matthew; Zhang, Chao, E-mail: czhang@uow.edu.au [School of Physics, University of Wollongong, Wollongong, New South Wales 2522 (Australia)

    2015-08-24

    Without breaking the topological order, HgTe/CdTe quantum wells can have two types of bulk band structure: direct gap type (type I) and indirect gap type (type II). We report that the strong nonlinear optical responses exist in both types of bulk states under a moderate electric field in the terahertz regime. Interestingly, for the type II band structure, the third order conductivity changes sign when chemical potentials lies below 10 meV due to the significant response of the hole excitation close to the bottom of conduction band. Negative nonlinear conductivities suggest that HgTe/CdTe quantum wells can find application in the gain medium of a laser for terahertz radiation. The thermal influences on nonlinear optical responses of HgTe/CdTe quantum wells are also studied.

  7. Growth and optical properties of CdTe quantum dots in ZnTe nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Wojnar, Piotr; Janik, Elzbieta; Baczewski, Lech T.; Kret, Slawomir; Karczewski, G.; Wojtowicz, Tomasz [Institute of Physics, Polish Academy of Sciences, Al Lotnikow 32/46, 02-668 Warsaw (Poland); Goryca, Mateusz; Kazimierczuk, Tomasz; Kossacki, Piotr [Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul Hoza 69, 00-681 Warsaw (Poland)

    2011-09-12

    We report on the formation of optically active CdTe quantum dots in ZnTe nanowires. The CdTe/ZnTe nanostructures have been grown by a gold nanocatalyst assisted molecular beam epitaxy in a vapor-liquid solid growth process. The presence of CdTe insertions in ZnTe nanowire results in the appearance of a strong photoluminescence band in the 2.0 eV-2.25 eV energy range. Spatially resolved photoluminescence measurements reveal that this broad emission consists of several sharp lines with the spectral width of about 2 meV. The large degree of linear polarization of these individual emission lines confirms their nanowire origin, whereas the zero-dimensional confinement is proved by photon correlation spectroscopy.

  8. Spectroscopic laser parameters of Ag/CdTe nanostructure

    Energy Technology Data Exchange (ETDEWEB)

    Giba, A.E., E-mail: alaadin85@niles.edu.eg [Department of Laser Science and Interaction, National Institute of Laser Enhanced Science, Cairo University, 12613 Giza (Egypt); Gadallah, A.-S. [Department of Laser Science and Interaction, National Institute of Laser Enhanced Science, Cairo University, 12613 Giza (Egypt); Mohamed, M.B. [Department of Laser Applications in Metrology, Photochemistry & Agriculture, National Institute of Laser Enhanced Science, Cairo University, 12613 Giza (Egypt); Azzouz, I.M. [Department of Laser Science and Interaction, National Institute of Laser Enhanced Science, Cairo University, 12613 Giza (Egypt)

    2015-11-15

    We report spectroscopic laser parameters analysis for CdTe quantum dots (QDs) in the presence of Ag nanoparticles (NPs). Absorption and emission cross-sections of about 2 nm-particle size of aqueous CdTe QDs were estimated, when different contents of about 40 nm Ag nanoparticles were added. The fluorescence, radiative lifetimes and the energy transfer between Ag NPs and CdTe QDs have been investigated. Lasing parameters that evaluate the possibility of getting laser action for these nanomaterials were calculated. The energy transfer mechanism between Ag NPs and CdTe QDs was occurred by Forster resonance energy transfer (FRET) as the average distance between them is about 50 nm. - Highlights: • Absorption and emission cross sections of Ag/CdTe have been calculated. • Lasing parameters of these nanomaterials have been also estimated. • The energy transfer mechanism between Ag NPs and CdTe QDs was determined. • Our findings are promising candidate for photonic devices.

  9. Nanowires in the CdHgTe Material System

    Science.gov (United States)

    Haakenaasen, R.; Selvig, E.; Hadzialic, S.; Skauli, T.; Hansen, V.; Tibballs, J. E.; Trosdahl-Iversen, L.; Steen, H.; Foss, S.; Taftø, J.; Halsall, M.; Orr, J.

    2008-09-01

    HgTe nanowires have been grown by molecular beam epitaxy (MBE). They are nucleated at Au particles on Si or GaAs substrates and subsequently self-organize and grow laterally on the surface into 20 50 nm wide, 0.5 1 μm long twisted, but single-crystal, wires. Further growth gives longer, wider, and straighter polycrystalline wires. When unimpeded by Au particles on the surface, the wires become straight and consist of segments of cubic HgTe and hexagonal Te parallel to the wire. Te nanowires and Au␣nanowires have also occasionally been formed. All attempts to grow CdHgTe on Si substrates with or without Au particles have resulted in polycrystalline layers. The phase diagrams and diffusion coefficients imply that CdHgTe or HgTe nanowires will not grow by the vapor liquid solid technique at the low MBE growth temperatures. SiO2 functions as a mask for selective growth of HgTe, but not for CdHgTe.

  10. CdTe and Cd sub 1 sub - sub x Zn sub x Te for nuclear detectors: facts and fictions

    CERN Document Server

    Fougeres, P; Hageali, M; Koebel, J M; Regal, R

    1999-01-01

    Both CdTe and Cd sub 1 sub - sub x Zn sub x Te (CZT) can be considered from their physical properties as very good materials for room temperature X- and gamma-rays detection. However, despite years of intense material research, no significant advance has been made to help one to choose between both semiconductors. This paper reviews a few facts about CdTe and CZT to attempt to draw a real comparison between both. THM-CdTe and HPB-CZT have been grown and characterized in Strasbourg. Crystal growth, alloying effects, transport properties and defects are reviewed on the basis of our results and the published ones. The results show that it is still very difficult to claim which one is the best.

  11. SnTe-TiC-C composites as high-performance anodes for Li-ion batteries

    Science.gov (United States)

    Son, Seung Yeon; Hur, Jaehyun; Kim, Kwang Ho; Son, Hyung Bin; Lee, Seung Geol; Kim, Il Tae

    2017-10-01

    Intermetallic SnTe composites dispersed in a conductive TiC/C hybrid matrix are synthesized by high-energy ball milling (HEBM). The electrochemical performances of the composites as potential anodes for Li-ion batteries are evaluated. The structural and morphological characteristics of the SnTe-TiC-C composites with various TiC contents are investigated by X-ray diffraction (XRD) and high-resolution transmission electron microscopy, which reveal that SnTe and TiC are uniformly dispersed in a carbon matrix. The electrochemical performance is significantly improved by introducing TiC to the SnTe-C composite; higher TiC contents result in better performances. Among the prepared composites, the SnTe-TiC (30%)-C and SnTe-TiC (40%)-C electrodes exhibit the best electrochemical performance, showing the reversible capacities of, respectively, 652 mAh cm-3 and 588 mAh cm-3 after 400 cycles and high rate capabilities with the capacity retentions of 75.4% for SnTe-TiC (30%)-C and 82.2% for SnTe-TiC (40%)-C at 10 A g-1. Furthermore, the Li storage reaction mechanisms of Te or Sn in the SnTe-TiC-C electrodes are confirmed by ex situ XRD.

  12. Formation of self assembled PbTe quantum dots in CdTe on Si(111)

    Science.gov (United States)

    Felder, F.; Fognini, A.; Rahim, M.; Fill, M.; Müller, E.; Zogg, H.

    2010-01-01

    We describe the growth and formation of self assembled PbTe quantum dots in a CdTe host on a silicon (111) substrate. Annealing yields different photoluminescence spectra depending on initial PbTe layer thickness, thickness of the CdTe cap layer and annealing temperature. Generally two distinct emission peaks at ˜0.3 eV and ˜0.45 eV are visible. Model calculations explaining their temperature dependence are performed. The dot size corresponds well with the estimated sizes from electron microscopy images. The quantum dots may be used as absorber within a mid-infrared detector.

  13. Fabrication of CdTe/NiTe films on Ni foils by radio-frequency magnetron sputtering method

    International Nuclear Information System (INIS)

    Mu, Yannan; Zhou, Xiaoming; Yao, Huizhen; Su, Shi; Lv, Pin; Chen, Yanli; Wang, Jun; Fu, Wuyou; Song, Wenxu; Yang, Haibin

    2015-01-01

    Highlights: • The effects of T s on CdTe deposited on Ni by magnetron sputtering is investigated. • An effective method is studied of making CdTe/NiTe without post-treatment. • As-prepared CdTe/NiTe raised optical absorption and PEC properties. • Pre-deposited Te can react with Ni to generate NiTe at T s = 350 °C. - Abstract: Cadmium Telluride (CdTe) semiconductor thin films are fabricated on flexible Ni foil substrates using radio-frequency (RF) magnetron sputtering under different substrate temperatures. The crystal structure and properties of the prepared functional thin films were characterized with series analysis technologies. The characterization results revealed that Nickel Telluride (NiTe) phase formatted at the interface of CdTe and Ni substrate when substrate temperature (T s ) is 450 °C. Specially, XRD results demonstrated that CdTe/NiTe films could also be obtained by pre-depositing Te film on Ni and reducing T s to 350 °C. The investigation on optical and photoelectrochemical (PEC) properties of the products illustrated that compact CdTe/NiTe films had improved the absorption in the visible region. Furthermore, PEC measurements indicated that CdTe/NiTe/Ni photoelectrode can have a promising application in photovoltaic devices

  14. The interfacial free energy of solid Sn on the boundary interface with liquid Cd-Sn eutectic solution

    International Nuclear Information System (INIS)

    Saatci, B; Cimen, S; Pamuk, H; Guenduez, M

    2007-01-01

    Equilibrated grain boundary groove shapes for solid Sn in equilibrium with Cd-Sn liquid were directly observed after annealing a sample at the eutectic temperature for about 8 days. The thermal conductivities of the solid phase, K S , and the liquid phase, K L , for the groove shapes were measured. From the observed groove shapes, the Gibbs-Thomson coefficients were obtained with a numerical method, using the measured G, K S and K L values. The solid-liquid interfacial energy of solid Sn in equilibrium with Cd-Sn liquid was determined from the Gibbs-Thomson equation. The grain boundary energy for solid Sn was also calculated from the observed groove shapes

  15. Experimental determination of band offsets at the SnS/CdS and SnS/InSxOy heterojunctions

    International Nuclear Information System (INIS)

    Abdel Haleem, A. M.; Ichimura, M.

    2010-01-01

    The semidirect x-ray photoelectron spectroscopy technique was used to measure the band alignments at the interface of heterostructures based on SnS. The layers were deposited by electrochemical deposition (ECD), chemical bath deposition (CBD), or photochemical deposition (PCD). The following four kinds of heterojunctions were characterized. (1) ECD-SnS/PCD-CdS. (2) CBD-SnS/PCD-CdS. (3) ECD-SnS/ECD-InS x O y . (4) CBD-SnS/ECD-InS x O y . The valence band offsets ΔE V of those four heterojunctions are determined to be 1.34, 1.59, 0.77, and 0.74±0.3 eV, respectively.

  16. Simple one-pot aqueous synthesis of CdHgTe nanocrystals using sodium tellurite as the Te source

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Zhitao [Institute for Advanced Interdisciplinary Research in Science and Technology, East China Normal University, Shanghai (China); Luo, Chunhua [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics of the Chinese Academy of Sciences, Shanghai (China); Huang, Rong [Key Laboratory of Polar Materials and Devices, Ministry of Education, School of Information Science and Technology, East China Normal University, Shanghai (China); Wang, Yiting [Institute for Advanced Interdisciplinary Research in Science and Technology, East China Normal University, Shanghai (China); Peng, Hui, E-mail: hpeng@ee.ecnu.edu.cn [Key Laboratory of Polar Materials and Devices, Ministry of Education, School of Information Science and Technology, East China Normal University, Shanghai (China); State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University (China); Polymer Electronic Research Centre, The University of Auckland, Private Bag 92019, Auckland (New Zealand); Travas-sejdic, Jadranka [Polymer Electronic Research Centre, The University of Auckland, Private Bag 92019, Auckland (New Zealand)

    2014-09-15

    In this work, we systematically investigated the one-pot aqueous synthesis conditions of CdHgTe nanocrystals (NCs) using sodium tellurite (Na{sub 2}TeO{sub 3}) as the Te source, and found that the added content of Hg{sup 2+} and the initial pH value of reaction solutions significantly affected the photoluminescence quantum yield (PL QY) of alloyed CdHgTe NCs. When the concentration of Cd was 1.0 mmol L{sup −1}, the mole ratio of Cd/Te/Hg/MPA was 1:0.5:0.05:2.4, and the initial pH value of the reaction solution was about 8.78, the PL QY of as-prepared CdHgTe NCs was up to 45%. Characterization by HRTEM and XRD confirmed the crystalline nature of CdHgTe NCs. Compared to other synthetic approaches of CdHgTe NCs, our experimental results indicate that Na{sub 2}TeO{sub 3} could be an attractive alternative Te source to directly synthesize CdHgTe NCs in aqueous media. - Highlights: • A one-pot method was developed for the synthesis of highly luminescent CdHgTe nanocrystals (NCs). • Sodium tellurite was used as the Te source. • The quantum yield reached up to 45%. • The experimental conditions were optimized and the prepared CdHgTe NCs were characterized.

  17. Diffusion of Cd and Te adatoms on CdTe(111 surfaces: A computational study using density functional theory

    Directory of Open Access Journals (Sweden)

    Ebadollah Naderi

    2015-01-01

    Full Text Available CdTe is one of the most promising semiconductor for thin-film based solar cells. Here we report a computational study of Cd and Te adatom diffusion on the CdTe (111 A-type (Cd terminated and B-type (Te terminated surfaces and their migration paths. The atomic and electronic structure calculations are performed under the DFT formalism and climbing Nudge Elastic Band (cNEB method has been applied to evaluate the potential barrier of the Te and Cd diffusion. In general the minimum energy site on the surface is labeled as Aa site. In case of Te and Cd on B-type surface, the sub-surface site (a site just below the top surface is very close in energy to the A site. This is responsible for the subsurface accumulation of adatoms and therefore, expected to influence the defect formation during growth. The diffusion process of adatoms is considered from Aa (occupied to Aa (empty site at the nearest distance. We have explored three possible migration paths for the adatom diffusion. The adatom surface interaction is highly dependent on the type of the surface. Typically, Te interaction with both type (5.2 eV for A-type and 3.8 eV for B-type is stronger than Cd interactions(2.4 eV for B-type and 0.39 eV for A-type. Cd interaction with the A-type surface is very weak. The distinct behavior of the A-type and B-type surfaces perceived in our study explain the need of maintaining the A-type surface during growth for smooth and stoichiometric growth.

  18. APT mass spectrometry and SEM data for CdTe solar cells

    Directory of Open Access Journals (Sweden)

    Jonathan D. Poplawsky

    2016-06-01

    Full Text Available Atom probe tomography (APT data acquired from a CAMECA LEAP 4000 XHR for the CdS/CdTe interface for a non-CdCl2 treated CdTe solar cell as well as the mass spectrum of an APT data set including a GB in a CdCl2-treated CdTe solar cell are presented. Scanning electron microscopy (SEM data showing the evolution of sample preparation for APT and scanning transmission electron microscopy (STEM electron beam induced current (EBIC are also presented. These data show mass spectrometry peak decomposition of Cu and Te within an APT dataset, the CdS/CdTe interface of an untreated CdTe solar cell, preparation of APT needles from the CdS/CdTe interface in superstrate grown CdTe solar cells, and the preparation of a cross-sectional STEM EBIC sample.

  19. Stokes shift and fine-structure splitting in CdSe / CdTe invert type-II ...

    Indian Academy of Sciences (India)

    Worasak Sukkabot

    2018-01-09

    Jan 9, 2018 ... methodology is explained in §2. Section 3 presents the analysis of the Stokes shift and FSS in CdSe/CdTe invert ... Theory and methodology. CdSe/CdTe invert type-II and CdTe/CdSe type-II core/ ... and exchange matrix elements are defined in the third term and fourth term, respectively. The detailed cal-.

  20. Study of sub band gap absorption of Sn doped CdSe thin films

    International Nuclear Information System (INIS)

    Kaur, Jagdish; Rani, Mamta; Tripathi, S. K.

    2014-01-01

    The nanocrystalline thin films of Sn doped CdSe at different dopants concentration are prepared by thermal evaporation technique on glass substrate at room temperature. The effect of Sn doping on the optical properties of CdSe has been studied. A decrease in band gap value is observed with increase in Sn concentration. Constant photocurrent method (CPM) is used to study the absorption coefficient in the sub band gap region. Urbach energy has been obtained from CPM spectra which are found to increase with amount of Sn dopants. The refractive index data calculated from transmittance is used for the identification of oscillator strength and oscillator energy using single oscillator model which is found to be 7.7 and 2.12 eV, 6.7 and 2.5 eV for CdSe:Sn 1% and CdSe:Sn 5% respectively

  1. Study of sub band gap absorption of Sn doped CdSe thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Jagdish; Rani, Mamta [Department of Physics, Panjab University, Chandigarh- 160014 (India); Tripathi, S. K., E-mail: surya@pu.ac.in [Centre of Advanced Study in Physics, Panjab University, Chandigarh- 160014 (India)

    2014-04-24

    The nanocrystalline thin films of Sn doped CdSe at different dopants concentration are prepared by thermal evaporation technique on glass substrate at room temperature. The effect of Sn doping on the optical properties of CdSe has been studied. A decrease in band gap value is observed with increase in Sn concentration. Constant photocurrent method (CPM) is used to study the absorption coefficient in the sub band gap region. Urbach energy has been obtained from CPM spectra which are found to increase with amount of Sn dopants. The refractive index data calculated from transmittance is used for the identification of oscillator strength and oscillator energy using single oscillator model which is found to be 7.7 and 2.12 eV, 6.7 and 2.5 eV for CdSe:Sn 1% and CdSe:Sn 5% respectively.

  2. Comparative study of CdTe sources used for deposition of CdTe thin films by close spaced sublimation technique

    Directory of Open Access Journals (Sweden)

    Wagner Anacleto Pinheiro

    2006-03-01

    Full Text Available Unlike other thin film deposition techniques, close spaced sublimation (CSS requires a short source-substrate distance. The kind of source used in this technique strongly affects the control of the deposition parameters, especially the deposition rate. When depositing CdTe thin films by CSS, the most common CdTe sources are: single-crystal or polycrystalline wafers, powders, pellets or pieces, a thick CdTe film deposited onto glass or molybdenum substrate (CdTe source-plate and a sintered CdTe powder. In this work, CdTe thin films were deposited by CSS technique from different CdTe sources: particles, powder, compact powder, a paste made of CdTe and propylene glycol and source-plates (CdTe/Mo and CdTe/glass. The largest deposition rate was achieved when a paste made of CdTe and propylene glycol was used as the source. CdTe source-plates led to lower rates, probably due to the poor heat transmission, caused by the introduction of the plate substrate. The results also showed that compacting the powder the deposition rate increases due to the better thermal contact between powder particles.

  3. Circular photogalvanic effect in HgTe/CdHgTe quantum well structures

    NARCIS (Netherlands)

    Wittmann, B.; Danilov, S. N.; Bel' kov, V. V.; Tarasenko, S. A.; Novik, E. G.; Buhmann, H.; Brune, C.; Molenkamp, L. W.; Kvon, Z. D.; Mikhailov, N. N.; Dvoretsky, S. A.; Vinh, N. Q.; van der Meer, A. F. G.; Murdin, B.; Ganichev, S. D.

    2010-01-01

    We describe the observation of the circular and linear photogalvanic effects in HgTe/CdHgTe quantum wells. The interband absorption of mid-infrared radiation as well as the intrasubband absorption of terahertz radiation in the quantun well structures is shown to cause a dc electric current due to

  4. Depth profiling study of in situ CdCl{sub 2} treated CdTe/CdS heterostructure with glancing angle incidence X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Vamsi Krishna, K.; Dutta, V

    2004-03-01

    CdTe thin films have been deposited using spray pyrolysis technique without and with in situ CdCl{sub 2} treatment. Scanning electron microscopy studies show enhanced grain growth in the presence of CdCl{sub 2}. Glancing angle incidence X-ray diffraction is used for the micro structural study of polycrystalline CdS/CdTe heterostructure at different depths by changing the incident angle. Spraying of CdCl{sub 2} on CdS prior to CdTe deposition promotes S diffusion throughout CdTe film and also Te diffusion into CdS. Whereas spraying of CdCl{sub 2} in between CdTe deposition prevents S diffusion partially and Te diffusion completely. There is an associated change in the microstress of the CdTe film at different layers. The films without CdCl{sub 2} treatment show compressive microstress varying from -98 to -158 MPa with increasing incident angle. CdCl{sub 2} spray during CdTe deposition shows compressive microstress, which varies from -98 MPa at the interface to -19 MPa near the surface and CdCl{sub 2} spray prior to CdTe deposition leads to a mildly tensile stress, from +40 to +20 MPa, which is very close to the standard shear stress of {approx}10 MPa for CdTe.

  5. Novel Sn-based Contact Structure for GeTe Phase Change Materials.

    Science.gov (United States)

    Simchi, Hamed; Cooley, Kayla A; Ding, Zelong; Molina, Alex; Mohney, Suzanne E

    2018-04-18

    Germanium telluride (GeTe) is a phase change material (PCM) that has gained recent attention due to its incorporation as an active material for radio frequency (RF) switches, as well as memory and novel optoelectronic devices. Considering PCM-based RF switches, parasitic resistances from Ohmic contacts can be a limiting factor in device performance. Reduction of the contact resistance (Rc) is therefore critical for reducing the ON-state resistance in order to meet the requirements of high-frequency RF applications. To engineer the Schottky barrier between the metal contact and GeTe, Sn was tested as an interesting candidate to alter the composition of the semiconductor near its surface, potentially forming narrow bandgap (0.2 eV) SnTe or a graded alloy with SnTe in GeTe. For this purpose, a novel contact stack of Sn/Fe/Au was employed and compared to a conventional Ti/Pt/Au stack. Two different pre-metallization surface treatments of HCl and deionized (DI) H2O were employed to make the Te-rich and Ge-rich interface, respectively. Contact resistance values were extracted using the refined transfer length method (RTLM). The best results were obtained with DI H2O for the Sn-based contacts but HCl treatment for the Ti/Pt/Au contacts. The as-deposited contacts had Rc (ρc) of 0.006 Ω.mm (8 × 10-9 Ω-cm2) for Sn/Fe/Au and 0.010 Ω.mm (3 × 10-8 Ω-cm2) for Ti/Pt/Au. However, the Sn/Fe/Au contacts were stable and their resistance decreased further to 0.004 Ω.mm (4 × 10-9 Ω-cm2) after annealing at 200 oC. In contrast, the contact resistance of the Ti/Pt/Au stack increased to 0.012 Ω.mm (4 × 10-8 Ω-cm2). Transmission electron microscopy (TEM) was used to characterize the interfacial reactions between the metals and GeTe. It was found that formation of SnTe at the interface, in addition to Fe-diffusion (doping) into GeTe, are likely responsible for the superior performance of Sn/Fe/Au contacts, resulting in the lowest reported contact resistance on GeTe.

  6. A facile route to shape controlled CdTe nanoparticles

    International Nuclear Information System (INIS)

    Mntungwa, Nhlakanipho; Rajasekhar, Pullabhotla V.S.R.; Revaprasadu, Neerish

    2011-01-01

    Research highlights: → A facile hybrid solution based/thermolysis route has been used for the synthesis of hexadecylamine capped CdTe nanoparticles. → This method involves the reaction by the addition of an aqueous suspension of a cadmium salt to a freshly prepared NaHTe solution. → The cadmium salt plays an important role in the growth mechanism of the particles and hence its final morphology. - Abstract: Hexadecylamine (HDA) capped CdTe nanoparticles have been synthesized using a facile hybrid solution based/thermolysis route. This method involves the reaction by the addition of an aqueous suspension or solution of a cadmium salt (chloride, acetate, nitrate or carbonate) to a freshly prepared NaHTe solution. The isolated CdTe was then dispersed in tri-octylphosphine (TOP) and injected into pre-heated HDA at temperatures of 190, 230 and 270 deg. C for 2 h. The particle growth and size distribution of the CdTe particles synthesized using cadmium chloride as the cadmium source were monitored using absorption and photoluminescence spectroscopy. The final morphology of the CdTe nanoparticles synthesized from the various cadmium sources was studied by transmission electron microscopy (TEM) and high resolution TEM. The cadmium source has an influence on the final morphology of the particles.

  7. Effects of current stressing on the p-Bi{sub 2}Te{sub 3}/Sn interfacial reactions

    Energy Technology Data Exchange (ETDEWEB)

    Chan, Hsing-Ting; Lin, Chih-Fan [Department of Chemical Engineering, National Chung Hsing University, Taichung 402, Taiwan (China); Yen, Yee-Wen [Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan (China); Chen, Chih-Ming, E-mail: chencm@nchu.edu.tw [Department of Chemical Engineering, National Chung Hsing University, Taichung 402, Taiwan (China)

    2016-05-25

    The Sn/p-Bi{sub 2}Te{sub 3}/Sn sandwich-type sample was current stressed with a density of 150 A/cm{sup 2} to investigate the effects of current stressing on the p-Bi{sub 2}Te{sub 3}/Sn interfacial reactions. Asymmetrical heating phenomenon was observed at the anodic Sn/p-Bi{sub 2}Te{sub 3} (50 °C) and cathodic p-Bi{sub 2}Te{sub 3}/Sn (120 °C) interfaces due to the Peltier effect. Besides the Peltier effect, the electromigration effect also influenced the growth of the SnTe phase and therefore polarity growth behavior was observed at the two interfaces. The growth of the SnTe phase at the cathodic p-Bi{sub 2}Te{sub 3}/Sn interface was accelerated because Peltier and electromigration effects drove more Sn atoms (dominant diffusion species) for the phase growth. By measuring the electromigration-induced atomic flux of Sn, the product of diffusivity and effective charge number (D × z*) was calculated to be 6.3 × 10{sup −9} cm{sup 2} s{sup −1} at 120 °C. - Highlights: • Sn/p-Bi{sub 2}Te{sub 3}/Sn sandwich-type sample is current stressed with a density of 150 A/cm{sup 2}. • Passage of an electric current induces Peltier and electromigration effects. • Peltier effect causes asymmetrical heating at the anode and cathode interfaces. • Both effects accelerate the SnTe growth at the cathode interface. • Sn is the dominant diffusion species identified by a marker experiment.

  8. Strong coupling and polariton lasing in Te based microcavities embedding (Cd,Zn)Te quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Rousset, J.-G., E-mail: j-g.rousset@fuw.edu.pl; Piętka, B.; Król, M.; Mirek, R.; Lekenta, K.; Szczytko, J.; Borysiuk, J.; Suffczyński, J.; Kazimierczuk, T.; Goryca, M.; Smoleński, T.; Kossacki, P.; Nawrocki, M.; Pacuski, W. [Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, PL-02-093 Warszawa (Poland)

    2015-11-16

    We report on properties of an optical microcavity based on (Cd,Zn,Mg)Te layers and embedding (Cd,Zn)Te quantum wells. The key point of the structure design is the lattice matching of the whole structure to MgTe, which eliminates the internal strain and allows one to embed an arbitrary number of unstrained quantum wells in the microcavity. We evidence the strong light-matter coupling regime already for the structure containing a single quantum well. Embedding four unstrained quantum wells results in further enhancement of the exciton-photon coupling and the polariton lasing in the strong coupling regime.

  9. Fabrication of CdS/CdTe-Based Thin Film Solar Cells Using an Electrochemical Technique

    Directory of Open Access Journals (Sweden)

    I. M. Dharmadasa

    2014-06-01

    Full Text Available Thin film solar cells based on cadmium telluride (CdTe are complex devices which have great potential for achieving high conversion efficiencies. Lack of understanding in materials issues and device physics slows down the rapid progress of these devices. This paper combines relevant results from the literature with new results from a research programme based on electro-plated CdS and CdTe. A wide range of analytical techniques was used to investigate the materials and device structures. It has been experimentally found that n-, i- and p-type CdTe can be grown easily by electroplating. These material layers consist of nano- and micro-rod type or columnar type grains, growing normal to the substrate. Stoichiometric materials exhibit the highest crystallinity and resistivity, and layers grown closer to these conditions show n → p or p → n conversion upon heat treatment. The general trend of CdCl2 treatment is to gradually change the CdTe material’s n-type electrical property towards i-type or p-type conduction. This work also identifies a rapid structural transition of CdTe layer at 385 ± 5 °C and a slow structural transition at higher temperatures when annealed or grown at high temperature. The second transition occurs after 430 °C and requires more work to understand this gradual transition. This work also identifies the existence of two different solar cell configurations for CdS/CdTe which creates a complex situation. Finally, the paper presents the way forward with next generation CdTe-based solar cells utilising low-cost materials in their columnar nature in graded bandgap structures. These devices could absorb UV, visible and IR radiation from the solar spectrum and combine impact ionisation and impurity photovoltaic (PV effect as well as making use of IR photons from the surroundings when fully optimised.

  10. Synthesis and superconductivity of In-doped SnTe nanostructures

    Directory of Open Access Journals (Sweden)

    Piranavan Kumaravadivel

    2017-07-01

    Full Text Available InxSn1−xTe is a time-reversal invariant candidate 3D topological superconductor derived from doping the topological crystalline insulator SnTe with indium. The ability to synthesize low-dimensional nanostructures of indium-doped SnTe is key for realizing the promise they hold in future spintronic and quantum information processing applications. But hitherto only bulk synthesized crystals and nanoplates have been used to study the superconducting properties. Here for the first time we synthesize InxSn1−xTe nanostructures including nanowires and nanoribbons, which show superconducting transitions. In some of the lower dimensional morphologies, we observe signs of more than one superconducting transition and the absence of complete superconductivity. We propose that material inhomogeneity, such as indium inhomogeneity and possible impurities from the metal catalyst, is amplified in the transport characteristics of the smaller nanostructures and is responsible for this mixed behavior. Our work represents the first demonstration of InxSn1−xTe nanowires with the onset of superconductivity, and points to the need for improving the material quality for future applications.

  11. IMPROVEMENT OF CdMnTe DETECTOR PERFORMANCE BY MnTe PURIFICATION

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K.H.; Bolotnikov, A.E.; Camarda, G.S.; Tappero, R.; Hossain, A.; Cui, Y.; Yang, G.; Gul, R.; and James, R.B.

    2011-04-25

    Residual impurities in manganese (Mn) are a big obstacle to obtaining high-performance CdMnTe (CMT) X-ray and gamma-ray detectors. Generally, the zone-refining method is an effective way to improve the material's purity. In this work, we purified the MnTe compounds combining the zone-refining method with molten Te, which has a very high solubility for most impurities. We confirmed the improved purity of the material by glow-discharge mass spectrometry (GDMS). We also found that CMT crystals from a multiply-refined MnTe source, grown by the vertical Bridgman method, yielded better performing detectors.

  12. Advanced high performance CdHgTe multiplexed arrays

    Science.gov (United States)

    Baker, I. M.; Charlton, D. E.; Arthurs, C.; Crimes, G.

    1992-12-01

    Very sensitive CdHgTe-silicon hybrid focal plane arrays for infrared applications were demonstrated in linear formats up to 1024 elements and in two dimensional arrays of up to 128 by 128 elements. The hybrid technology is based on photovoltaic, CdHgTe diode arrays coupled to full custom, CMOS, silicon multiplexing circuitry. The technology used for the next generation of advanced linear and two dimensional infrared arrays is described. The use of optical concentration for special applications is described and current progress on the 2.5 micrometer two dimensional focal plane for the HRIS (High Resolution Imaging Spectrometer) program is outlined.

  13. Comparative study of SnS recrystallization in molten CdI{sub 2}, SnCl{sub 2}and KI

    Energy Technology Data Exchange (ETDEWEB)

    Timmo, Kristi; Kauk-Kuusik, Marit; Pilvet, Maris; Mikli, Valdek; Kaerber, Erki; Raadik, Taavi; Leinemann, Inga; Altosaar, Mare; Raudoja, Jaan [Department of Materials Science, Tallinn University of Technology, Tallinn (Estonia)

    2016-01-15

    In the present study, the recrystallization of polycrystalline SnS in different molten salts CdI{sub 2}, SnCl{sub 2} and KI as flux materials are presented. The recrystallization and growth of polycrystalline material in molten salts produces unique SnS monograin powders usable in monograin layer solar cells. XRD and Raman analysis revealed that single phase SnS powder can be obtained in KI at 740 C and in SnCl{sub 2} at 500 C. Long time heating of SnS in molten CdI{sub 2} was accompanied by chemical interaction between SnS and CdI{sub 2} that resulted in a mixture of CdS and Sn{sub 2}S{sub 3} crystals. SEM images showed that morphology of crystals can be controlled by the nature of the flux materials: needle-like Sn{sub 2}S{sub 3} together with round edged crystals of CdS in CdI{sub 2}, flat crystals of SnS with smooth surfaces in SnCl{sub 2} and well-formed SnS crystals with rounded edges in KI had been formed. The temperatures of phase transitions and/or the interactions of SnS and flux materials were determined by differential thermal analysis. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Nanosized Thin SnO2 Layers Doped with Te and TeO2 as Room Temperature Humidity Sensors

    Directory of Open Access Journals (Sweden)

    Biliana Georgieva

    2014-05-01

    Full Text Available In this paper the humidity sensing properties of layers prepared by a new method for obtaining doped tin oxide are studied. Different techniques—SEM, EDS in SEM, TEM, SAED, AES and electrical measurements—are used for detailed characterization of the thin layers. The as-deposited layers are amorphous with great specific area and low density. They are built up of a fine grained matrix, consisting of Sn- and Te-oxides, and a nanosized dispersed phase of Te, Sn and/or SnTe. The chemical composition of both the matrix and the nanosized particles depends on the ratio RSn/Te and the evaporation conditions. It is shown that as-deposited layers with RSn/Te ranging from 0.4 to 0.9 exhibit excellent characteristics as humidity sensors operating at room temperature—very high sensitivity, good selectivity, fast response and short recovery period. Ageing tests have shown that the layers possess good long-term stability. Results obtained regarding the type of the water adsorption on the layers’ surface help better understand the relation between preparation conditions, structure, composition and humidity sensing properties.

  15. Aqueous synthesis of CdTe at FeOOH and CdTe at Ni(OH)2 composited nanoparticles

    International Nuclear Information System (INIS)

    Li Liang; Ren Jicun

    2006-01-01

    Two kinds of bi-functional nanomaterials, CdTe at FeOOH and CdTe at Ni(OH) 2 , were synthesized in water phase. In the synthesis, using the luminescent CdTe nanocrystals (NCs) as a core, Fe 3+ (Ni 2+ ) was added to CdTe NCs aqueous solution and slowly hydrolyzed to deposit a layer of hydroxide onto the luminescent CdTe NCs in the presence of stabilizer. TEM, XRD, XPS, UV, fluorescence spectrometer and physical property measurement system (PPMS) were used to characterize the final products, and the results showed that the as-prepared nanoparticles with core/shell structure exhibited certain magnetic properties and fluorescence. - Graphical abstract: Fluorescent and magnetic bi-functional CdTe at FeOOH and CdTe at Ni(OH) 2 nanoparticles were prepared by seed-mediated approach in water phase

  16. Microstructure of absorber layers in CdTe/CdS solar cells

    CERN Document Server

    Cousins, M A

    2001-01-01

    expected from extrapolating the linear trend in the bulk. These observations are explained in terms of the pinning of the CdTe grain size to the underlying CdS, and the small grain size this causes. A simple model was proposed for a link between the grain-growth to the efficiency improvement. The study also examines the behaviour of defects within grains upon CdCl sub 2 treatment provided the first direct evidence of recovery on CdCl sub 2 treatment in this system. Finally, a computer model is presented to describe the evolution of microstructure during growth. This is shown to be capable of reproducing the observed variation in grain size, but its strict physical accuracy is questioned. This work concerns the microstructure of CSS-grown CdTe layers used for CdTe/CdS solar cells. Particular attention is given to how the development of microstructure on annealing with CdCl sub 2 may correlate with increases in efficiency. By annealing pressed pellets of bulk CdTe powder, it is shown that microstructural change...

  17. High-efficiency large-area CdTe panels

    Energy Technology Data Exchange (ETDEWEB)

    Albright, S.P.; Chamberlin, R.R.; Jordan, J.F. (Photon Energy, Inc., El Paso, TX (USA))

    1990-11-01

    The objective of this three year effort has been to develop an improved materials technology and fabrication process for limited volume production of 1 ft{sup 2} and 4 ft{sup 2} CdS/CdTe photovoltaic modules. The module stability objective by the end of this three year subcontract was to develop techniques to provide ten year life exploration with no greater than 10% degradation. In order to achieve these efficiency and stability objectives, the research program has been separated into tasks including: (1) analysis and characterization of CdS/CdTe Devices; (2) performance optimization on small cells; (3) encapsulation and stability testing; and (4) module efficiency optimization. 27 refs., 18 figs., 3 tabs.

  18. Inelastic x-ray investigation of the ferroelectric transition in SnTe

    Science.gov (United States)

    O'Neill, Christopher D.; Sokolov, Dmitry A.; Hermann, Andreas; Bossak, Alexei; Stock, Christopher; Huxley, Andrew D.

    2017-04-01

    We report that the lowest energy transverse-optic phonon in metallic SnTe softens to near zero energy at the structural transition at TC=75 K and importantly show that the energy of this mode below TC increases as the temperature decreases. Since the mode is a polar displacement this proves unambiguously that SnTe undergoes a ferroelectric displacement below TC. Concentration gradients and imperfect stoichiometry in large crystals may explain why this was not seen in previous inelastic neutron scattering studies. Despite SnTe being metallic we find that the ferroelectric transition is similar to that in ferroelectric insulators, unmodified by the presence of conduction electrons: we find that (i) the damping of the polar mode is dominated by coupling to acoustic phonons rather than electron-phonon coupling, (ii) the transition is almost an ideal continuous transition, and (iii) comparison with density functional calculations identifies the importance of dipolar-dipolar screening for understanding this behavior.

  19. Photovoltaic performance of a Cd1−xMgxTe/CdS top-cell structure

    International Nuclear Information System (INIS)

    Martinez, Omar S.; Regalado-Pérez, E.; Mathews, N.R.; Morales, Erik R.; Reyes-Coronado, David; Galvez, Geovanni Hernández; Mathew, Xavier

    2015-01-01

    In this paper we report the progress in developing a wide band gap alloy material based on CdTe to use as the top-cell absorber in tandem solar cells. High photovoltaic performance for a Cd 1−x Mg x Te/CdS top-cell was achieved by tuning the composition of the Cd 1−x Mg x Te film, and optimizing the device processing. We have carried out studies on the effect of vapor chloride treatment of the Cd 1−x Mg x Te/CdS device and the thermal annealing of the Cu/Au contacts on the opto-electronic properties of the device. With improved contact processing and post deposition treatments, we were able to achieve 9.3% efficiency for a 1.6 eV band gap top-cell; Cd 1−x Mg x Te/CdS on conductive glass substrate. - Highlights: • Cd 1−x Mg x Te films obtained by co-evaporation of CdTe and Mg • Band gap of Cd 1−x Mg x Te can be easily tuned by verifying x. • Band gap of Cd 1−x Mg x Te is stable only for short annealing durations. • Obtained efficiency of a Cd 1−x Mg x Te based device with a band gap of 1.6 eV is 9.3%

  20. Signal-on electrochemiluminescence of biofunctional CdTe quantum dots for biosensing of organophosphate pesticides.

    Science.gov (United States)

    Liang, Han; Song, Dandan; Gong, Jingming

    2014-03-15

    A new, highly sensitive and selective ECL assay biosensor based on target induced signal on has been developed for the detection of organophosphate pesticides (OPs), whereby the smart integration of graphene nanosheets (GNs), CdTe quantum dots (CdTe QDs), and acetylcholinesterase (AChE) enzymatic reaction yields a biofunctional AChE-GNs-QDs hybrid as cathodic ECL emitters for OPs sensing. The electrochemically synthesized GNs were selected as a supporting material to anchor CdTe QDs, exhibiting a significantly amplified ECL signal of QDs. On the basis of the effect of OPs on the ECL signal of AChE-QDs-GNs modified glassy carbon electrode (GCE), a highly sensitive GNs-anchored-QDs-based signal-on ECL biosensor was developed for sensing OPs, combined with the enzymatic reactions and the dissolved oxygen as coreactant. The conditions for OPs detection were optimized by using methyl parathion (MP) as a model OP compound. Under the optimized experimental conditions, such a newly designed system shows remarkably improved sensitivity and selectivity for the sensing of OPs. The detection limit was found to be as low as about 0.06 ng mL(-1) (S/N=3). Toward the goal for practical applications, the resulting sensor was further evaluated by monitoring MP in spiked vegetable samples, showing fine applicability for the detection of MP in real samples. © 2013 Elsevier B.V. All rights reserved.

  1. Stokes shift and fine-structure splitting in CdSe/CdTe invert type-II ...

    Indian Academy of Sciences (India)

    Using the atomistic tight-binding (TB) theory and configuration interaction (CI) description, it is showed that the Stokes shift and fine-structure splitting (FSS) in semiconductor core/shell nanocrystals are predominantly affected by the shell thickness and band profiles. CdSe/CdTe invert type-II and CdTe/CdSe type-II core/shell ...

  2. Detector Performance of Ammonium-Sulfide-Passivated CdZnTe and CdMnTe Materials

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K.H.; Bolotnikov, A.E.; Camarda, G.S.; Marchini, L.; Yang, G.; Hossain, A.; Cui, Y.; Xu, L.; and James, R.B.

    2010-08-01

    Dark currents, including those in the surface and bulk, are the leading source of electronic noise in X-ray and gamma detectors, and are responsible for degrading a detector's energy resolution. The detector material itself determines the bulk leakage current; however, the surface leakage current is controllable by depositing appropriate passivation layers. In previous research, we demonstrated the effectiveness of surface passivation in CZT (CdZnTe) and CMT (CdMnTe) materials using ammonium sulfide and ammonium fluoride. In this research, we measured the effect of such passivation on the surface states of these materials, and on the performances of detectors made from them.

  3. Investigation of microstructural details in low thermal conductivity thermoelectric Sn1-xSbxTe alloy

    Science.gov (United States)

    Vishal, B.; Sahu, R.; Bhat, U.; Datta, R.

    2017-08-01

    We report on the detailed microstructural features in a low thermal conductivity Sn1-xSbxTe (x = 0.04, 0.08, 0.15) alloy investigated by transmission electron microscopy and density functional theory calculation. A near theoretical minimum thermal conductivity is obtained for Sn0.85Sb0.15Te alloy composition containing distinct microstructures. The crisscross lines along {111} planes forming nano-scale structures have been identified as areas with Sb replacing both regular Sn sites and Te anti-sites. This leads to the modulation in the {111} inter-planar spacing (d111) and results in superstructure spots in the electron diffraction pattern. The formation of such structures is supported by theoretical calculation. In general, two different phases are observed in the system, one with Sb replacing the regular Sn sites and another with crisscross lines where Sb replaces both the Sn and Te sites. Theoretical calculation further reveals that while the areas with Sb at the regular site give rise to large thermo-power, the areas with Sb substituting regular and anti-sites combination forming a superstructure contribute towards low lattice thermal conductivity and the combined effect increases the zT to ˜1.

  4. Investigation of electroluminescence properties of CdTe@CdS core ...

    Indian Academy of Sciences (India)

    brication of light emitting device. Therefore, energy diagram of fabricated device is shown in figure 4. According to the energy diagram, using MoO3 will decrease the energy ba- rrier for injection of holes from ITO to HOMO energy state of PVK. Energy barrier of the electron injection from the conduction band of CdTe@CdS ...

  5. Growth of wurtzite CdTe nanowires on fluorine-doped tin oxide glass substrates and room-temperature bandgap parameter determination

    Science.gov (United States)

    Choi, Seon Bin; Song, Man Suk; Kim, Yong

    2018-04-01

    The growth of CdTe nanowires, catalyzed by Sn, was achieved on fluorine-doped tin oxide glass by physical vapor transport. CdTe nanowires grew along the 〈0001〉 direction, with a very rare and phase-pure wurtzite structure, at 290 °C. CdTe nanowires grew under Te-limited conditions by forming SnTe nanostructures in the catalysts and the wurtzite structure was energetically favored. By polarization-dependent and power-dependent micro-photoluminescence measurements of individual nanowires, heavy and light hole-related transitions could be differentiated, and the fundamental bandgap of wurtzite CdTe at room temperature was determined to be 1.562 eV, which was 52 meV higher than that of zinc-blende CdTe. From the analysis of doublet photoluminescence spectra, the valence band splitting energy between heavy hole and light hole bands was estimated to be 43 meV.

  6. Fabrication of CdTe/Si heterojunction solar cell

    Science.gov (United States)

    Bera, Swades Ranjan; Saha, Satyajit

    2016-10-01

    A simple cost effective method is preferred to grow nanoparticles of CdTe. Nanoparticles of CdTe are grown by simple chemical reduction route using EDA as capping agent and Sodium Borohydride as reducing agent. The grown nanoparticles are characterized using transmission electron microscopy (TEM), X-ray diffraction, optical absorption, and photoluminescence study. From optical absorption study, the band-gap was found to be 2.46 eV. From TEM study, the average particle size was found to be within 8-12 nm which confirms the formation of CdTe nanoparticles. Pl spectra indicate the luminescence from surface states at 2.01 eV, which is less compared to the increased band-gap of 2.46 eV. The grown nanoparticles are used to fabricate a heterojunction of CdTe on P-Si by a spin coating technique for solar cell fabrication in a cost effective way. I-V characteristics of the grown heterojunction in dark as well as under light are measured. Efficiency and fill-factor of the device are estimated.

  7. Applications of CdTe to nuclear medicine. Final report

    International Nuclear Information System (INIS)

    Entine, G.

    1985-01-01

    Uses of cadmium telluride (CdTe) nuclear detectors in medicine are briefly described. They include surgical probes and a system for measuring cerebral blood flow in the intensive care unit. Other uses include nuclear dentistry, x-ray exposure control, cardiology, diabetes, and the testing of new pharmaceuticals

  8. Ion Beam Nanostructuring of HgCdTe Ternary Compound

    Science.gov (United States)

    Smirnov, Aleksey B.; Savkina, Rada K.; Udovytska, Ruslana S.; Gudymenko, Oleksandr I.; Kladko, Vasyl P.; Korchovyi, Andrii A.

    2017-05-01

    Systematic study of mercury cadmium telluride thin films subjected to the ion beam bombardment was carried out. The evolution of surface morphology of (111) Hg1 - x Cd x Te ( x 0.223) epilayers due to 100 keV B+ and Ag+ ion irradiation was studied by AFM and SEM methods. X-ray photoelectron spectroscopy and X-ray diffraction methods were used for the investigation of the chemical compound and structural properties of the surface and subsurface region. It was found that in the range of nanoscale, arrays of holes and mounds on Hg0.777Cd0.223Te (111) surface as well as the polycrystalline Hg1 - x Cd x Te cubic phase with alternative compound ( x 0.20) have been fabricated using 100 keV ion beam irradiation of the basic material. Charge transport investigation with non-stationary impedance spectroscopy method has shown that boron-implanted structures are characterized by capacity-type impedance whereas for silver-implanted structures, an inductive-type impedance (or "negative capacitance") is observed. A hybrid system, which integrates the nanostructured ternary compound (HgCdTe) with metal-oxide (Ag2O) inclusions, was fabricated by Ag+ ion bombardment. The sensitivity of such metal-oxide-semiconductor hybrid structure for sub-THz radiation was detected with NEP 4.5 × 10-8 W/Hz1/2at ν ≈ 140 GHz and 296 K without amplification.

  9. Cumulative effects of Te precipitates in CdZnTe radiation detectors

    International Nuclear Information System (INIS)

    Bolotnikov, A.E.; Camarda, G.S.; Carini, G.A.; Cui, Y.; Li, L.; James, R.B.

    2007-01-01

    High-quality radiation detector-grade CdZnTe material is free from large-scale defects, such as grain boundaries, twins, and large Te or Cd inclusions (>50 μm), although it usually contains high concentrations of uniformly distributed Te inclusions and precipitates, typically of ∼20-μm-diameter size or smaller. We address the effects of the small-size Te precipitates on charge collection in CZT detectors, the significance of which is not yet well characterized. The strong correlation that we earlier found between the high-resolution X-ray maps and IR images proved that even small Te precipitates can trap substantial fractions of charge from the electron cloud. In this work, we modeled the transport of an electron cloud across idealized CZT devices containing Te precipitates to demonstrate that their cumulative effect can explain the degradation of energy resolution and the detection efficiency losses observed in actual CZT devices. Due to lack of experimental data on how the Te precipitates interact with an electron cloud, we developed a simplified (phenomenological) model based on the geometrical aspects of the problem. Despite its simplicity, the model correctly reproduced many experimental facts and gave quantitative predictions on the extent to which the presence of Te precipitates and inclusions can be tolerated. The broadening of the electron cloud due to repulsion and diffusion is at the core of the problem, making even low concentrations of small precipitates important in the device's performance

  10. Some physical properties of Cd{sub 1-x}Sn{sub x}S films used as window layer in heterojunction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Oezer, Tuelay [Anadolu University, Science Faculty, Physics Department, Eskisehir (Turkey); Koese, Salih [Eskisehir Osmangazi University, Art and Science Faculty, Physics Department, Eskisehir (Turkey)

    2009-06-15

    CdS has been proved to be an ideal material for use as the window layer for heterojunction solar cells especially with n-CdS/p-CdTe. CdS, Cd{sub 0.9}Sn{sub 0.1}S and Cd{sub 0.8}Sn{sub 0.2}S films were deposited onto glass substrates at 300 C substrate temperature by using ultrasonic spray pyrolysis technique (USP). The effect of Sn concentration on some structural, optical and electrical properties of the films was presented. The crystal structure and orientation of the films were investigated by X-ray diffraction (XRD) patterns. XRD patterns showed that films have polycrystalline nature with a hexagonal structure. The grain size of the films decreased with increasing x values. The optical band gap values were obtained from optical absorption spectra of the films. The optical band gap values of the films were found to be between 2.44 and 2.45 eV. The variations of conductivity of Cd{sub 1-x}Sn{sub x}S (0 {<=} x {<=} 0.2) films have been investigated depending on applied voltage in dark and under illumination. The resistivity significantly decreased with increasing tin concentration and under illumination. (author)

  11. ELECTRICAL AND PHOTOELECTRICAL PROPERTIES OF CdS/Cd1-xMnxTe HETEROJUNCTIONS

    Directory of Open Access Journals (Sweden)

    Petru GAŞIN

    2015-12-01

    Full Text Available Electrical and photoelectrical properties of CdS/Cd1-xMnxTe heterojunction at different temperatures from 293 K to 393 K were studied. The potential barrier at 293 K makes 0,78 V and is linearly decreasing with temperature increase with a temperature coefficient of 5,5·10-3 V·K-1. From lnIinv= f(1/T dependence at U=1V the activation energy of 0,61 eV was determined. CdS/Cd0,6Mn0,4Te heterojunction spectral sensitivity at 300 K covers the wavelength region.PROPRIERĂŢILE ELECTRICE ŞI FOTOELECTRICE ALE HETEROJONCŢIUNILOR CdS/Cd1-xMnxTeÎn intervalul de temperaturi de la 293K până la 393K au fost cercetate proprietăţile electrice şi fotoelectrice ale hetero-joncţiunilor CdS/Cd1-xMnxTe. La 293K potenţialul de difuzie constituie 0,78 V şi cu creşterea temperaturii mărimea lui se micşorează linear cu coeficientul termic egal cu 5,5·10-3 V·K-1. Din dependenţa lnIinv= f(1/T la tensiunea de 1V a fost determinată energia de activare care este egală cu 0,61 eV. Spectrele fotoconductibilităţii denotă că la 300 K hetero-joncţiunile CdS/Cd0,6Mn0,4Te sunt fotosensibile în regiunea de lungimi de undă 0,52÷0,83µm.

  12. A thermodynamic stability of bulk and epitaxial CdHgTe, ZnHgTe and MnHgTe solid solutions

    International Nuclear Information System (INIS)

    Dejbuk, V.G.; Dremlyuzhenko, S.G.; Ostapov, S.Eh.

    2005-01-01

    A thermodynamics of Cd 1-x Hg x Te, Zn x Hg 1-x Te and Mg x Hg 1-x Te alloys has been investigated for a delta-lattice parameter model. The phase diagrams obtained show the stability of Cd 1-x Hg x Te, Zn x Hg 1-x Te in the whole range of compositions, alongside with a miscibility gap for Mn x Hg 1-x Te being of 0.35 x Hg 1-x Te/CdTe and Mn x Hg 1-x Te/Cd 0.96 Zn 0.04 Te epitaxial films result in lowering critical temperatures and narrowing the miscibility gap [ru

  13. Optimizing timing performance of CdTe detectors for PET

    Science.gov (United States)

    Nakhostin, M.

    2017-10-01

    Despite several attractive properties, the poor timing performance of compound semiconductor detectors such as CdTe and CdZnTe has hindered their use in commercial PET imaging systems. The standard method of pulse timing with such detectors is to employ a constant-fraction discriminator at the output of a timing filter which is fed by the pulses from a charge-sensitive preamplifier. The method has led to a time resolution of about 10 ns at full-width at half-maximum (FWHM) with 1 mm thick CdTe detectors. This paper presents a detailed investigation on the parameters limiting the timing performance of Ohmic contact planar CdTe detectors with the standard pulse timing method. The jitter and time-walk errors are studied through simulation and experimental measurements and it is revealed that the best timing results obtained with the standard timing method suffer from a significant loss of coincidence events (~50%). In order to improve the performance of the detectors with full detection efficiency, a new digital pulse timing method based on a simple pattern recognition technique was developed. A time resolution of 3.29  ±  0.10 ns (FWHM) in the energy range of 300-650 keV was achieved with an Ohmic contact planar CdTe detector (5  ×  5  ×  1 mm3). The digital pulse processing method was also used to correct for the charge-trapping effect and an improvement in the energy resolution from 4.83  ±  0.66% to 2.780  ±  0.002% (FWHM) at 511 keV was achieved. Further improvement of time resolution through a moderate cooling of the detector and the application of the method to other detector structures are also discussed.

  14. Studies of CdS/CdTe interface: Comparison of CdS films deposited by close space sublimation and chemical bath deposition techniques

    International Nuclear Information System (INIS)

    Han, Jun-feng; Fu, Gan-hua; Krishnakumar, V.; Schimper, Hermann-Josef; Liao, Cheng; Jaegermann, Wolfram; Besland, M.P.

    2015-01-01

    The CdS layers were deposited by two different methods, close space sublimation (CSS) and chemical bath deposition (CBD) technique. The CdS/CdTe interface properties were investigated by transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The TEM images showed a large CSS-CdS grain size in the range of 70-80 nm. The interface between CSS-CdS and CdTe were clear and sharp, indicating an abrupt hetero-junction. On the other hand, CBD-CdS layer had much smaller grain size in the 5-10 nm range. The interface between CBD-CdS and CdTe was not as clear as CSS-CdS. With the stepwise coverage of CdTe layer, the XPS core levels of Cd 3d and S 2p in CSS-CdS had a sudden shift to lower binding energies, while those core levels shifted gradually in CBD-CdS. In addition, XPS depth profile analyses indicated a strong diffusion in the interface between CBD-CdS and CdTe. The solar cells prepared using CSS-CdS yielded better device performance than the CBD-CdS layer. The relationships between the solar cell performances and properties of CdS/CdTe interfaces were discussed. - Highlights: • Studies of CdS deposited by close space sublimation and chemical bath deposition • An observation of CdS/CdTe interface by transmission electron microscope • A careful investigation of CdS/CdTe interface by X ray photoelectron spectra • An easier diffusion at the chemical bath deposition CdS and CdTe interface

  15. Growth and optical characterization of HgTe-CdTe superlattices

    International Nuclear Information System (INIS)

    Schikora, D.; Tomm, J.W.; Rakkenus, K.; Pessa, M.

    1990-01-01

    The epitaxial growth of HgTe-CdTe superlattices (SL) on GaAs substrates and their luminescence properties are reported. The excitation was performed by Nd-YAG laser pulses and a stimulated emission from SL is observed. An additional transmission measurement was carried out. The results show that the molecular beam epitaxial growth of the SL on GaAs and the (100) orientation of the epitaxial layer could improve the preparation of optically pumped SL-based lasers

  16. Development of a CdTe/CdS solar wafer. Final report; Entwicklung einer CdTe/CdS Duennschicht-Solarzelle. Schlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Koentges, M.; Reineck-Koch, R.

    2002-07-01

    The focus was on the development and optimisation of the close-spaced sublimation process in an inline coating plant for production of stable high-efficiency CdS/CdTe solar wafers. An inline plant was to be constructed by ANTEC GmbH and ISFH. Film layers were to be optimised, and investigations were to show whether processing of single films is possible without breaking the vacuum, e.g. for etching. The results were to be used directly by ANTEC GmbH. An efficiency of 14 percent and an idle voltage of about 850 V were to be achieved with a film thickness of 2 {mu}m. To achieve these goals, the following project stages were envisaged: 1. Replacement of the expensive window material ITO by a less costly material. 2. Higher stability of the back contact by using appropriate intermediate layers. 3. Alternative activation processes other than the conventional CdCl{sub 2} activation. 4. Investigation of the effects of the activation step on the electric properties of the sample. [German] Die uebergreifende Aufgabenstellung des Projektes war die Entwicklung und Optimierung des Close-spaced-Sublimation verfahrens in einer Inline-Beschichtungsanlage fuer die Herstellung stabiler und hocheffizienter CdS/CdTe Duennschichtsolarzellen. Mit dem Wissen der ANTEC GmbH sollte zusammen mit dem ISFH eine Inline-Anlage konzipiert und gebaut werden. Die fuer die Solarzelle notwendigen Einzelschichten sollten in dem Inline-Prozess optimiert werden. Es sollte ermittelt werden, ob eine Prozessierung der Einzelschichten ohne Brechen des Vakuums, z.B. fuer einen Aetzschritt, moeglich ist. Die erzielten Ergebnisse sollen direkt der ANTEC GmbH zufliessen. In dem Projekt wurde als Endziel ein Wirkungsgrad der CdTe/CdS-Duennschichtsolarzelle von 14% und eine Erhoehung der Leerlaufspannung auf Werte um 850 mV angestrebt. Gleichzeitig sollte die CdTe-Schichtdicke auf 2 {mu}m vermindert werden. Um dieses Gesamtziel zu erreichen, sollen folgende Teilaufgaben bearbeitet werden: 1) Das teuere

  17. Raman and photoluminescence spectra of ZnTe/CdSe and ZnTe/CdTe tetrapod shaped nano-hetero structures

    Science.gov (United States)

    Fiore, Angela; Morello, Giovanni; Scremin, Barbara Federica

    2018-01-01

    In the present paper we report the Raman and photoluminescence characterization of two nano-hetero-structures of II-VI semiconductors, tetrapod shaped. The examined samples were constituted of a ZnTe core and either CdSe or CdTe arms. The main contributions to the Raman spectra were assigned to phonons from the arms of the structures, but the weak contribution from the ZnTe core was identified from the separate measurement of spectra of the seeds used for growing the arms. The simultaneously acquired photoluminescence spectra allowed identifying an intense band characteristic of a Type II band alignment at 920 nm for the ZnTe/CdSe nanostructures.

  18. Aqueous synthesis of CdTe/CdS/ZnS quantum dots and their optical and chemical properties.

    Science.gov (United States)

    Li, Zhong; Dong, Chaoqing; Tang, Lichuan; Zhu, Xin; Chen, Hongjin; Ren, Jicun

    2011-01-01

    In this paper, we described a strategy for synthesis of thiol-coated CdTe/CdS/ZnS (core-shell-shell) quantum dots (QDs) via aqueous synthesis approach. The synthesis conditions were systematically optimized, which included the size of CdTe core, the refluxing time and the number of monolayers and the ligands, and then the chemical and optical properties of the as-prepared products were investigated. We found that the mercaptopropionic acid (MPA)-coated CdTe/CdS/ZnS QDs presented highly photoluminescent quantum yields (PL QYs), good photostability and chemical stability, good salt tolerance and pH tolerance and favorable biocompatibility. The characterization of high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD) and fluorescence correlation spectroscopy (FCS) showed that the CdTe/CdS/ZnS QDs had good monodispersity and crystal structure. The fluorescence life time spectra demonstrated that CdTe/CdS/ZnS QDs had a longer lifetime in contrast to fluorescent dyes and CdTe QDs. Furthermore, the MPA-stabilized CdTe/CdS/ZnS QDs were applied for the imaging of cells. Compared with current synthesis methods, our synthesis approach was reproducible and simple, and the reaction conditions were mild. More importantly, our method was cost-effective, and was very suitable for large-scale synthesis of CdTe/CdS/ZnS QDs for future applications. Copyright © 2010 John Wiley & Sons, Ltd.

  19. Characterization of the native defects in HgTe, CdTe, Hg1-x, CdxTe by positron annihilation: evidence of native vacancies

    International Nuclear Information System (INIS)

    Geffroy, B.

    1987-12-01

    Direct evidence of native vacancies is found in as-grown Cd x Hg 1-x Te single crystals prepared by the travelling heating method (THM). The vacancies have characteristics depending on the annealing undergone by the crystals after their growth and on the conduction type in the crystals. In as-grown CdTe and Cd 0.7 Hg 0.3 Te (THM), native vacancies are found in n-type materials. In as-grown HgTe and Cd 0.2 Hg 0.8 Te (THM), native vacancies are found in p materials. They disappear after stoechiometric annealings in which the crystals are converted n-type. From the positron lifetime at the vacancies, 320±4 ps, one can show that the native vacancies are metallic vacancies V Cd in CdTe, V Hg in HgTe, V Hg or/and V Cd in Cd x Hg 1-x Te alloys. The concentration of the metallic vacancies is estimated in as-grown crystals. In as-grown p-type CdTe and Cd 0.7 Hg 0.3 Te (THM), in as-grown then subsequently p-type annealed HgTe and Cd 0.2 Hg 0.8 Te (THM), vacancy type defects are also found giving rise to lifetime of about 290 ps. These defects are also found in crystals grown by Bridgman method. The nature of these defects is discussed. The In doping effects on the metallic vacancies have been studied. It is shown that In addition increases the concentration of metallic vacancies in CdTe (In) (THM). Vacancy-In complexes appear for In concentrations of the order or above 10 17 cm -3 . These complexes disappear after decompensating annealings and only the metallic vacancies survive. Small vacancies clusters of two or three vacancies are found after deformation at room temperature in CdTe (Mn) (THM) [fr

  20. Synthesis and characterization of Sn-doped CdZnS nanoparticles

    Indian Academy of Sciences (India)

    Administrator

    confirmed by energy-dispersive X-ray analysis. The effect of dopant concentration on the photoluminescence ... Cadmium zinc sulphide (CdZnS) alloy compounds have attracted technological interest, because the ..... elements, namely cadmium, sulphur, zinc and Sn. An intense peak for Sn was found in the spectrum due to ...

  1. Novel Approach to Front Contact Passivation for CdTe Photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Kephart, Jason

    2018-02-18

    The goal of this project was to study the use of sputter-deposited oxide materials for interface passivation of CdTe-based photovoltaics. Several candidate materials were chosen based on their promise in passivating the CdTe and CdSeTe semiconductor interface, chemical and thermal stability to device processing, and ability to be deposited by sputter deposition.

  2. Study and development of new CdTe and CdZnTe detection structures for X and γ imagery

    International Nuclear Information System (INIS)

    Rosaz, M.

    1997-01-01

    The aim of this study is to show the interest of applying cadmium telluride (CdTe) for X- and γ- ray imaging applications, with specific technological (via contact nature) and geometric (via Frisch grids) structures suited for each application. This work is divided into three different but complementary parts: the first part describes a simulation model which allows a better understanding of CdTe based γ- ray detectors. The new feature of this model compared to previous ones, is that it is able to take into account the electric field's non uniform spatial distribution inside the detector s. The results enable us to de-convolute the influence of material and contact parameters on the spectrometric performances (energy resolution and peak/valley ratio) of CdTe based detectors; the second part presents different technological structures deposited upon CdTe, (grown by two different methods, i.e Bridgman and High Pressure Bridgman). These structures were characterised in X- and γ- ray detection; theoretical models are developed which allow a certain insight into the detection properties of each couple (material + contact); the third part deals with new contact geometries which allow a screening effect of the bulk (analogous to the Frisch grid effect in gaseous detectors) resulting in improved energy resolution and peak/valley ratios; encouraging first results on prototypes are presented and discussed. This work has allowed a better understanding of physical behaviour of CdTe based detectors, coupled with advances in technological issues to upgrade the overall performances of these detectors for application in X- and γ- ray imaging. (author)

  3. Synthesis and characterization of ternary compound, Mn2SnTe4

    Indian Academy of Sciences (India)

    Administrator

    Laboratorio de Cristalografía, Departamento de Química,. †. Laboratorio de Magnetismo en Sólidos,. Departamento de Física, Facultad de Ciencias, Universidad de Los Andes, Mérida 5101, Venezuela. MS received 7 January 2009; revised 20 April 2009. Abstract. Mn2SnTe4 was synthesized by direct fusion using the ...

  4. Unexpected Au Alloying in Tailoring In-Doped SnTe Nanostructures with Gold Nanoparticles

    Directory of Open Access Journals (Sweden)

    Samuel Atherton

    2017-03-01

    Full Text Available Materials with strong spin-orbit interaction and superconductivity are candidates for topological superconductors that may host Majorana fermions (MFs at the edges/surfaces/vortex cores. Bulk-superconducting carrier-doped topological crystalline insulator, indium-doped tin telluride (In-SnTe is one of the promising materials. Robust superconductivity of In-SnTe nanostructures has been demonstrated recently. Intriguingly, not only 3-dimensional (3D nanostructures but also ultra-thin quasi-2D and quasi-1D systems can be grown by the vapor transport method. In particular, nanostructures with a controlled dimension will give us a chance to understand the dimensionality and the quantum confinement effects on the superconductivity of the In-SnTe and may help us work on braiding MFs in various dimensional systems for future topological quantum computation technology. With this in mind, we employed gold nanoparticles (GNPs with well-identified sizes to tailor In-SnTe nanostructures grown by vapor transport. However, we could not see clear evidence that the presence of the GNPs is necessary or sufficient to control the size of the nanostructures. Nevertheless, it should be noted that a weak correlation between the diameter of GNPs and the dimensions of the smallest nanostructures has been found so far. To our surprise, the ones grown under the vapor–liquid–solid mechanism, with the use of the GNPs, contained gold that is widely and inhomogeneously distributed over the whole body.

  5. In-situ CdS/CdTe Heterojuntions Deposited by Pulsed Laser Deposition

    KAUST Repository

    Avila-Avendano, Jesus

    2016-04-09

    In this paper pulsed laser deposition (PLD) methods are used to study p-n CdTe/CdS heterojunctions fabricated in-situ. In-situ film deposition allows higher quality p-n interfaces by minimizing spurious contamination from the atmosphere. Morphologic and structural analyses were carried for CdTe films deposited on various substrates and different deposition conditions. The electrical characteristics and performance of the resulting p-n heterojunctions were studied as function of substrate and post-deposition anneal temperature. In-situ growth results on diodes with a rectification factor of ~ 105, an ideality factor < 2, and a reverse saturation current ~ 10-8 A. The carrier concentration in the CdTe film was in the range of ~ 1015 cm-3, as measured by C-V methods. The possible impact of sulfur diffusion from the CdS into the CdTe film is also investigated using High Resolution Rutherford Back-Scattering.

  6. MOCVD growth of transparent conducting Cd2SnO4 thin films

    International Nuclear Information System (INIS)

    Metz, A.W.; Poeppelmeier, K.R.; Marks, T.J.; Lane, M.A.; Kannewurt, C.R.

    2004-01-01

    The first preparation of transparent conducting Cd 2 SnO 4 thin films by a simple MOCVD process is described. As-deposited films using Cd(hfa) 2 (TMEDA) (Figure), at 365 C are found to be highly crystalline with a relatively wide range of grain size of 100-300 nm. XRD indicates a cubic spinel Cd 2 SnO 4 crystal structure and the possible presence of a small amount of CdO. The films exhibit conductivities of 2170 S/cm and a bandgap of 3.3 eV, rivaling those of commercial tin-doped indium oxide. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

  7. Carrier concentration dependence of structural disorder in thermoelectric Sn1−xTe

    Directory of Open Access Journals (Sweden)

    Mattia Sist

    2016-09-01

    Full Text Available SnTe is a promising thermoelectric and topological insulator material. Here, the presumably simple rock salt crystal structure of SnTe is studied comprehensively by means of high-resolution synchrotron single-crystal and powder X-ray diffraction from 20 to 800 K. Two samples with different carrier concentrations (sample A = high, sample B = low have remarkably different atomic displacement parameters, especially at low temperatures. Both samples contain significant numbers of cation vacancies (1–2% and ordering of Sn vacancies possibly occurs on warming, as corroborated by the appearance of multiple phases and strain above 400 K. The possible presence of disorder and anharmonicity is investigated in view of the low thermal conductivity of SnTe. Refinement of anharmonic Gram–Charlier parameters reveals marginal anharmonicity for sample A, whereas sample B exhibits anharmonic effects even at low temperature. For both samples, no indications are found of a low-temperature rhombohedral phase. Maximum entropy method (MEM calculations are carried out, including nuclear-weighted X-ray MEM calculations (NXMEM. The atomic electron densities are spherical for sample A, whereas for sample B the Te electron density is elongated along the 〈100〉 direction, with the maximum being displaced from the lattice position at higher temperatures. Overall, the crystal structure of SnTe is found to be defective and sample-dependent, and therefore theoretical calculations of perfect rock salt structures are not expected to predict the properties of real materials.

  8. Strong anharmonicity in the phonon spectra of PbTe and SnTe from first principles

    Science.gov (United States)

    Ribeiro, Guilherme A. S.; Paulatto, Lorenzo; Bianco, Raffaello; Errea, Ion; Mauri, Francesco; Calandra, Matteo

    2018-01-01

    At room temperature, PbTe and SnTe are efficient thermoelectrics with a cubic structure. At low temperature, SnTe undergoes a ferroelectric transition with a critical temperature strongly dependent on the hole concentration, while PbTe is an incipient ferroelectric. By using the stochastic self-consistent harmonic approximation, we investigate the anharmonic phonon spectra and the occurrence of a ferroelectric transition in both systems. We find that vibrational spectra strongly depend on the approximation used for the exchange-correlation kernel in density-functional theory. If gradient corrections and the theoretical volume are employed, then the calculation of the phonon frequencies as obtained from the diagonalization of the free-energy Hessian leads to phonon spectra in good agreement with experimental data for both systems. In PbTe we evaluate the linear thermal expansion coefficient γ =2.3 ×10-5K-1 , finding it to be in good agreement with experimental value of γ =2.04 ×10-5K-1 . Furthermore, we study the phonon spectrum and we do reproduce the transverse optical mode phonon satellite detected in inelastic neutron scattering and the crossing between the transverse optical and the longitudinal acoustic modes along the Γ X direction. The phonon satellite becomes broader at high temperatures but its energy is essentially temperature independent, in agreement with experiments. We decompose the self-consistent harmonic free energy in second-, third-, and fourth-order anharmonic terms. We find that the third- and fourth-order terms are small. However, treating the third-order term perturbatively on top of the second-order self-consistent harmonic free energy overestimates the energy of the satellite associated with the transverse optical mode. On the contrary, a perturbative treatment on top of the harmonic Hamiltonian breaks down and leads to imaginary phonon frequencies already at 300 K. In the case of SnTe, we describe the occurrence of a ferroelectric

  9. Structural, optical, and improved photocatalytic properties of CdS/SnO{sub 2} hybrid photocatalyst nanostructure

    Energy Technology Data Exchange (ETDEWEB)

    Venkata Reddy, Ch., E-mail: cvrphy@gmail.com [School of Mechanical Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of); Ravikumar, R.V.S.S.N. [Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar 522510 (India); Srinivas, Ganganagunta [Engineering Department, lbra College of Technology, lbra 400 (Oman); Shim, Jaesool, E-mail: jshim@ynu.ac.kr [School of Mechanical Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of); Cho, Migyung, E-mail: mgcho@tu.ac.kr [Department of Game Engineering, Tongmyong University, Busan 608-711 (Korea, Republic of)

    2017-07-15

    Highlights: • CdS, SnO{sub 2}, and a CdS/SnO{sub 2} hybrid photocatalyst were synthesized using a two-step technique. • The dislocation density, strain values are higher for CdS/SnO{sub 2} hybrid photocatalyst. • The CdS/SnO{sub 2} has a higher surface area and smaller crystallite size compared to pristine CdS. • The CdS/SnO{sub 2} catalyst greatly reduced recombination of electron and hole pairs. - Abstract: CdS, SnO{sub 2} and CdS/SnO{sub 2} hybrid photocatalyst nanostructure were synthesized using a two-step (co-precipitation/hydrothermal) method. The as-prepared materials were characterized by powder X-ray diffraction, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), surface analysis (BET), photoluminescence spectra (PL), UV–Vis diffusion reflectance spectroscopy (DRS), fourier transform infrared spectroscopy (FT-IR), and photocatalytic activity. The band gap energies calculated from the DRS results are 3.30, 2.15, and 2.99 eV for pristine SnO{sub 2}, CdS, and the CdS/SnO{sub 2} hybrid photocatalyst, respectively. The CdS/SnO{sub 2} hybrid photocatalyst showed more efficient charge carrier separation and improved photocatalytic degradation of methyl orange (MO). The highest degradation rate constant was achieved for the CdS/SnO{sub 2} hybrid photocatalyst (0.02434 min{sup −1}) compared to CdS (0.01381 min{sup −1}) and SnO{sub 2} (0.00878 min{sup −1}). The present study provides insights for improving the photocatalytic activity and photo-stability of CdS/SnO{sub 2} hybrid photocatalyst.

  10. Influence of CdTe Deposition Temperature and Window Thickness on CdTe Grain Size and Lifetime After CdCl2 Recrystallization

    Energy Technology Data Exchange (ETDEWEB)

    Amarasinghe, Mahisha; Colegrove, Eric; Moutinho, Helio; Albin, David; Duenow, Joel; Johnston, Steve; Kephart, Jason; Sampath, Walajabad; Al-Jassim, Mowafak; Sivananthan, Siva; Metzger, Wyatt K.

    2018-03-01

    Grain structure influences both transport and recombination in CdTe solar cells. Larger grains generally are obtained with higher deposition temperatures, but commercially it is important to avoid softening soda-lime glass. Furthermore, depositing at lower temperatures can enable different substrates and reduced cost in the future. We examine how initial deposition temperatures and morphology influence grain size and lifetime after CdCl2 recrystallization. Techniques are developed to estimate grain distribution quickly with low-cost optical microscopy, which compares well with electron backscatter diffraction data providing corroborative assessments of exposed CdTe grain structures. Average grain size increases as a function of CdCl2 temperature. For lower temperature close-spaced sublimation CdTe depositions, there can be more stress and grain segregation during recrystallization. However, the resulting lifetimes and grain sizes are similar to high-temperature CdTe depositions. The grain structures and lifetimes are largely independent of the presence and/or interdiffusion of Se at the interface, before and after the CdCl2 treatment.

  11. Current state-of-the-art industrial and research applications using room-temperature CdTe and CdZnTe solid state detectors

    International Nuclear Information System (INIS)

    Eisen, Y.

    1996-01-01

    Improvements of CdTe crystal quality and significant progress in the growth of large ingots of high resistivity CdZnTe material enable the fabrication of larger area detectors in single element form or monolithic arrays. These advances allow for the development of imaging devices of improved spatial resolution for industrial, research and medical applications. CdTe and CdZnTe detectors operate in single photon counting mode or in current mode (charge integrating mode). The paper presents advantages of CdTe and CdZnTe over common scintillator type detectors, but also presents the shortcomings of the former detectors with respect to charge collection which limit the yields of good spectrometers. The paper reviews industrial and research applications utilizing these detectors and in particular describes in detail two imaging systems for security screening and custom inspection. These systems are characterized by large dynamic range and good spatial resolution and are composed of large arrays of CdTe spectrometers and discriminator grade detectors. A wide energy range detector assembly, for astrophysical research of gamma ray bursts composed of CdTe, HgI 2 and CdZnTe spectrometers in two dimensional arrays is also presented. (orig.)

  12. High Flux Energy-Resolved Photon-Counting X-Ray Imaging Arrays with CdTe and CdZnTe for Clinical CT

    International Nuclear Information System (INIS)

    Barber, William C.; Hartsough, Neal E.; Gandhi, Thulasidharan; Iwanczyk, Jan S.; Wessel, Jan C.; Nygard, Einar; Malakhov, Nail; Wawrzyniak, Gregor; Dorholt, Ole; Danielsen, Roar

    2013-06-01

    We have fabricated fast room-temperature energy dispersive photon counting x-ray imaging arrays using pixellated cadmium zinc (CdTe) and cadmium zinc telluride (CdZnTe) semiconductors. We have also fabricated fast application specific integrated circuits (ASICs) with a two dimensional (2D) array of inputs for readout from the CdZnTe sensors. The new CdTe and CdZnTe sensors have a 2D array of pixels with a 0.5 mm pitch and can be tiled in 2D. The new 2D ASICs have four energy discriminators per pixel with a linear energy response across the entire dynamic range for clinical CT. The ASICs can also be tiled in 2D and are designed to fit within the active area of the 2D sensors. We have measured several important performance parameters including; an output count rate (OCR) in excess of 20 million counts per second per square mm, an energy resolution of 7 keV full width at half maximum (FWHM) across the entire dynamic range, and a noise floor less than 20 keV. This is achieved by directly interconnecting the ASIC inputs to the pixels of the CdTE and CdZnTe sensors incurring very little additional capacitance. We present a comparison of the performance of the CdTe and CdZnTe sensors including the OCR, FWHM energy resolution, and noise floor. (authors)

  13. Progress in the Development of CdTe and CdZnTe Semiconductor Radiation Detectors for Astrophysical and Medical Applications

    OpenAIRE

    Del Sordo, S.; Abbene, L.; Caroli, E.; Mancini, A.; Zappettini, A.; Ubertini, P.

    2009-01-01

    Over the last decade, cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) wide band gap semiconductors have attracted increasing interest as X-ray and gamma ray detectors. Among the traditional high performance spectrometers based on silicon (Si) and germanium (Ge), CdTe and CdZnTe detectors show high detection efficiency and good room temperature performance and are well suited for the development of compact and reliable detection systems. In this paper, we review the current status...

  14. Positron annihilation spectroscopy of vacancy-related defects in CdTe:Cl and CdZnTe:Ge at different stoichiometry deviations

    Science.gov (United States)

    Šedivý, L.; Čížek, J.; Belas, E.; Grill, R.; Melikhova, O.

    2016-01-01

    Positron annihilation spectroscopy (PAS) was used to examine the effect of defined Cd-rich and Te-rich annealing on point defects in Cl-doped CdTe and Ge-doped CdZnTe semi-insulating single crystals. The as-grown crystals contain open-volume defects connected with Cd vacancies . It was found that the Cd vacancies agglomerate into clusters coupled with Cl in CdTe:Cl, and in CdZnTe:Ge they are coupled with Ge donors. While annealing in Cd pressure reduces of the density, subsequent annealing in Te pressure restores . The CdTe:Cl contains negatively-charged shallow traps interpreted as Rydberg states of A-centres and representing the major positron trapping sites at low temperature. Positrons confined in the shallow traps exhibit lifetime, which is shorter than the CdTe bulk lifetime. Interpretation of the PAS data was successfully combined with electrical resistivity, Hall effect measurements and chemical analysis, and allowed us to determine the principal point defect densities. PMID:26860684

  15. Characterization of isothermal vapor phase epitaxial (Hg,Cd)Te

    International Nuclear Information System (INIS)

    Lee, S.B.; Magel, L.K.; Tang, M.F.S.; Stevenson, D.A.; Tregilgas, J.H.; Goodwin, M.W.; Strong, R.L.

    1990-01-01

    We report on the characterization of mercury cadmium telluride (Hg 1-x Cd x Te) film grown by the isothermal vapor phase epitaxial method (ISOVPE) and on the surface conversion of bulk Hg 1-x Cd x Te to larger bandgap material. The crystal perfection is evaluated using defect etching, electron beam and electrolyte electroreflectance (EBER and EER), and Rutherford backscattering spectrometry (RBS). Hall measurements are used to measure carrier densities and mobilities. Surface concentrations and concentration profiles are measured for the ISOVPE grown layers by transmission Fourier transform infrared spectroscopy (FTIR) and electron-probe microanalysis (EPMA) to establish quantitative informations about composition control. Metal--insulator-semiconductor (MIS) structures were made and the properties important to device performance such as compositional uniformity, storage time, and carrier concentration are measured. The ISOVPE layers are compared in quality to films grown by other methods and show promise for MIS devices

  16. Advanced processing of CdTe pixel radiation detectors

    Science.gov (United States)

    Gädda, A.; Winkler, A.; Ott, J.; Härkönen, J.; Karadzhinova-Ferrer, A.; Koponen, P.; Luukka, P.; Tikkanen, J.; Vähänen, S.

    2017-12-01

    We report a fabrication process of pixel detectors made of bulk cadmium telluride (CdTe) crystals. Prior to processing, the quality and defect density in CdTe material was characterized by infrared (IR) spectroscopy. The semiconductor detector and Flip-Chip (FC) interconnection processing was carried out in the clean room premises of Micronova Nanofabrication Centre in Espoo, Finland. The chip scale processes consist of the aluminum oxide (Al2O3) low temperature thermal Atomic Layer Deposition (ALD), titanium tungsten (TiW) metal sputtering depositions and an electroless Nickel growth. CdTe crystals with the size of 10×10×0.5 mm3 were patterned with several photo-lithography techniques. In this study, gold (Au) was chosen as the material for the wettable Under Bump Metalization (UBM) pads. Indium (In) based solder bumps were grown on PSI46dig read out chips (ROC) having 4160 pixels within an area of 1 cm2. CdTe sensor and ROC were hybridized using a low temperature flip-chip (FC) interconnection technique. The In-Au cold weld bonding connections were successfully connecting both elements. After the processing the detector packages were wire bonded into associated read out electronics. The pixel detectors were tested at the premises of Finnish Radiation Safety Authority (STUK). During the measurement campaign, the modules were tested by exposure to a 137Cs source of 1.5 TBq for 8 minutes. We detected at the room temperature a photopeak at 662 keV with about 2 % energy resolution.

  17. HgCdTe Surface and Defect Study Program.

    Science.gov (United States)

    1986-03-01

    HgCdTe at 200 keV, 26 RPT60411 F 21nCp ts Implated i Hg~de atൈ ke 26 R,.’.4.1 SANTA GARSANA RESEARCH CINTER 2H 3 VARIOUS IONS Il•1020 I III m, =’ 200...these interfaces. However, this past work has principally been empirical where a very specific problem has been attached in the context of a given

  18. Metastability and reliability of CdTe solar cells

    Science.gov (United States)

    Guo, Da; Brinkman, Daniel; Shaik, Abdul R.; Ringhofer, Christian; Vasileska, Dragica

    2018-04-01

    Thin-film modules of all technologies often suffer from performance degradation over time. Some of the performance changes are reversible and some are not, which makes deployment, testing, and energy-yield prediction more challenging. Manufacturers devote significant empirical efforts to study these phenomena and to improve semiconductor device stability. Still, understanding the underlying reasons of these instabilities remains clouded due to the lack of ability to characterize materials at atomistic levels and the lack of interpretation from the most fundamental material science. The most commonly alleged causes of metastability in CdTe devices, such as ‘migration of Cu’, have been investigated rigorously over the past fifteen years. Still, the discussion often ended prematurely with stating observed correlations between stress conditions and changes in atomic profiles of impurities or CV doping concentration. Multiple hypotheses suggesting degradation of CdTe solar cell devices due to interaction and evolution of point defects and complexes were proposed, and none of them received strong theoretical or experimental confirmation. It should be noted that atomic impurity profiles in CdTe provide very little intelligence on active doping concentrations. The same elements could form different energy states, which could be either donors or acceptors, depending on their position in crystalline lattice. Defects interact with other extrinsic and intrinsic defects; for example, changing the state of an impurity from an interstitial donor to a substitutional acceptor often is accompanied by generation of a compensating intrinsic interstitial donor defect. Moreover, all defects, intrinsic and extrinsic, interact with the electrical potential and free carriers so that charged defects may drift in the electric field and the local electrical potential affects the formation energy of the point defects. Such complexity of interactions in CdTe makes understanding of temporal

  19. Performance characteristics of CdTe drift ring detector

    Science.gov (United States)

    Alruhaili, A.; Sellin, P. J.; Lohstroh, A.; Veeramani, P.; Kazemi, S.; Veale, M. C.; Sawhney, K. J. S.; Kachkanov, V.

    2014-03-01

    CdTe and CdZnTe material is an excellent candidate for the fabrication of high energy X-ray spectroscopic detectors due to their good quantum efficiency and room temperature operation. The main material limitation is associated with the poor charge transport properties of holes. The motivation of this work is to investigate the performance characteristics of a detector fabricated with a drift ring geometry that is insensitive to the transport of holes. The performance of a prototype Ohmic CdTe drift ring detector fabricated by Acrorad with 3 drift rings is reported; measurements include room temperature current voltage characteristics (IV) and spectroscopic performance. The data shows that the energy resolution of the detector is limited by leakage current which is a combination of bulk and surface leakage currents. The energy resolution was studied as a function of incident X-ray position with an X-ray microbeam at the Diamond Light Source. Different ring biasing schemes were investigated and the results show that by increasing the lateral field (i.e. the bias gradient across the rings) the active area, evaluated by the detected count rate, increased significantly.

  20. Fast Neutron Detection Using Pixelated CdZnTe Spectrometers

    Science.gov (United States)

    Streicher, Michael; Goodman, David; Zhu, Yuefeng; Brown, Steven; Kiff, Scott; He, Zhong

    2017-07-01

    Fast neutrons are an important signature of special nuclear materials (SNMs). They have a low natural background rate and readily penetrate high atomic number materials that easily shield gamma-ray signatures. Therefore, they provide a complementary signal to gamma rays for detecting shielded SNM. Scattering kinematics dictate that a large nucleus (such as Cd or Te) will recoil with small kinetic energy after an elastic collision with a fast neutron. Charge carrier recombination and quenching further reduce the recorded energy deposited. Thus, the energy threshold of CdZnTe detectors must be very low in order to sense the small signals from these recoils. In this paper, the threshold was reduced to less than 5 keVee to demonstrate that the 5.9-keV X-ray line from 55Fe could be separated from electronic noise. Elastic scattering neutron interactions were observed as small energy depositions (less than 20 keVee) using digitally sampled pulse waveforms from pixelated CdZnTe detectors. Characteristic gamma-ray lines from inelastic neutron scattering were also observed.

  1. One-Pot Aqueous Phase Synthesis of CdTe and CdTe/ZnS Core/Shell Quantum Dots.

    Science.gov (United States)

    Zhou, Beiying; Yang, Fengjiu; Zhang, Xin; Cheng, Wenyan; Luo, Wei; Wang, Lianjun; Jiang, Wan

    2016-06-01

    A facile and economical one-pot strategy has been developed for the synthesis of water-solute CdTe and CdTe/ZnS core/shell quantum dots (QDs) using tellurium dioxide (TeO2) as a tellurium precursor and thioglycolic acid (TGA) as stabilizer without any pre-treatment and inert atmosphere protection. As-synthesized QDs were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), electron diffraction spectroscopy (EDS), X-ray powder diffraction (XRD), UV-vis and photoluminescence (PL). The spherical particles were uniformly distributed with the average diameters of 3.2 nm (CdTe QDs) and -5 nm (CdTe/ZnS QDs). By altering the reaction conditions, the emission wavelengths of the CdTe core QDs and CdTe/ZnS core/shell QDs could be tuned from 508 to 574 nm and 526 to 600 nm with narrow full widths at half maximum (FWHM) of 33 to 58 nm, respectively. Meanwhile, on the optimum condition, the luminescence efficiency of CdTe/ZnS QDs can achieve to 74%, which was higher than that of CdTe core QDs (24%).

  2. Probing the sensitive and selective luminescent detection of peroxynitrite using thiol-capped CdTe and CdTe-ZnS quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Adegoke, Oluwasesan [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa); Nyokong, Tebello, E-mail: t.nyokong@ru.ac.za [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa)

    2013-02-15

    CdTe and CdTe-ZnS quantum dots (QDs) capped with 3-mercaptopropionic acid (MPA), thioglycolic acid (TGA), or glutathione (GSH) have been employed for the first time as luminescent probes for the sensitive and selective detection of peroxynitrite (ONOO{sup -}) in aqueous solution. The sensitivity of the proposed probe followed the order: MPA-{sub TGA}-CdTe-ZnS>GSH-{sub TGA}-CdTe-ZnS>MPA-CdTe QDs. The varying degree of quenching is elucidated based on the QD-thiolate bond of CdTe-ZnS being more sensitive to oxidation from ONOO{sup -} than CdTe. The selectivity of the probe in the presence of co-existing species followed the order: GSH-{sub TGA}-CdTe-ZnS>MPA-{sub TGA}-CdTe-ZnS>MPA-CdTe QDs. QDs capped with MPA showed less selectivity for ONOO{sup -} than GSH. The best limit of detection (LOD) of 12.6 nM was obtained for MPA-{sub TGA}-CdTe-ZnS QDs. Time-resolved fluorescence measurements indicated that the interaction between ONOO{sup -} and the QDs is static in nature. - Graphical abstract: CdTe and CdTe-ZnS quantum dots capped with 3-mercaptopropionic acid or glutathione are employed for the detection of peroxynitrite in aqueous solution, with glutathione capped quantum dots showing the best selectivity and core-shell quantum dots showing better sensitivity than core quantum dots. Highlights: Black-Right-Pointing-Pointer CdTe and CdTe-ZnS quantum dots were employed for the detection of peroxynitrite. Black-Right-Pointing-Pointer The best limit of detection of 12.6 nM was obtained. Black-Right-Pointing-Pointer Quantum dots capped with mercaptopropionic acid were less selective for ONOO{sup -} than glutathione. Black-Right-Pointing-Pointer Interaction between peroxynitrite and the quantum dots is static in nature.

  3. CdTe and CdZnTe gamma ray detectors for medical and industrial imaging systems

    CERN Document Server

    Eisen, Y; Mardor, I

    1999-01-01

    CdTe and CdZnTe X-ray and gamma ray detectors in the form of single elements or as segmented monolithic detectors have been shown to be useful in medical and industrial imaging systems. These detectors possess inherently better energy resolution than scintillators coupled to either photodiodes or photomultipliers, and together with application specific integrated circuits they lead to compact imaging systems of enhanced spatial resolution and better contrast resolution. Photopeak efficiencies of these detectors is greatly affected by a relatively low hole mobility-lifetime product. Utilizing these detectors as highly efficient good spectrometers, demands use of techniques to improve their charge collection properties, i.e., correct for variations in charge losses at different depths of interaction in the detector. The corrections for the large hole trapping are made either by applying electronic techniques or by fabricating detector or electrical contacts configurations which differ from the commonly used pla...

  4. Study of the spectrometric performances of monolithic CdZnTe / CdTe gamma ray detectors

    International Nuclear Information System (INIS)

    Gros d'Aillon, E.

    2005-11-01

    Pixelated monolithic CdTe/CdZnTe semiconductor gamma ray detectors are brought to replace scintillation detectors for medical applications, notably for single photon emission computed tomography (SPECT). In addition to compactness, they present better spectrometric performances: energy resolution, detection efficiency, and spatial resolution. Moreover, the photons depth of interaction in the crystal can be measured. This work aimed in studying experimentally and by simulation the correlations between anodes pitch, material physic properties (resistivity and electron transport properties), and detectors spectrometric performances. We have compared several methods of measuring the photon interaction depth, and have obtained an energy resolution ranging from 1.7% to 7% at 122 keV, according to material, for 5 mm thick detectors. Charge sharing between adjacent anodes has been studied and a measured data processing is proposed. (author)

  5. High Power Factor and Enhanced Thermoelectric Performance of SnTe-AgInTe2: Synergistic Effect of Resonance Level and Valence Band Convergence.

    Science.gov (United States)

    Banik, Ananya; Shenoy, U Sandhya; Saha, Sujoy; Waghmare, Umesh V; Biswas, Kanishka

    2016-10-05

    Understanding the basis of electronic transport and developing ideas to improve thermoelectric power factor are essential for production of efficient thermoelectric materials. Here, we report a significantly large thermoelectric power factor of ∼31.4 μW/cm·K 2 at 856 K in Ag and In co-doped SnTe (i.e., SnAg x In x Te 1+2x ). This is the highest power factor so far reported for SnTe-based material, which arises from the synergistic effects of Ag and In on the electronic structure and the improved electrical transport properties of SnTe. In and Ag play different but complementary roles in modifying the valence band structure of SnTe. In-doping introduces resonance levels inside the valence bands, leading to a significant improvement in the Seebeck coefficient at room temperature. On the other hand, Ag-doping reduces the energy separation between light- and heavy-hole valence bands by widening the principal band gap, which also results in an improved Seebeck coefficient. Additionally, Ag-doping in SnTe enhances the p-type carrier mobility. Co-doping of In and Ag in SnTe yields synergistically enhanced Seebeck coefficient and power factor over a broad temperature range because of the synergy of the introduction of resonance states and convergence of valence bands, which have been confirmed by first-principles density functional theory-based electronic structure calculations. As a consequence, we have achieved an improved thermoelectric figure of merit, zT ≈ 1, in SnAg 0.025 In 0.025 Te 1.05 at 856 K.

  6. New chalcogenide glasses in the CdTe-AgI-As{sub 2}Te{sub 3} system

    Energy Technology Data Exchange (ETDEWEB)

    Kassem, M. [Univ. Picardie Jules Verne, F-80000 Amiens (France); Le Coq, D., E-mail: david.lecoq@univ-littoral.fr [Univ. Lille Nord de France, F-59000 Lille (France); ULCO, LPCA, EA 4493, F-59140 Dunkerque (France); Boidin, R.; Bychkov, E. [Univ. Lille Nord de France, F-59000 Lille (France); ULCO, LPCA, EA 4493, F-59140 Dunkerque (France)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Determination of the glass-forming region in the pseudo-ternary CdTe-AgI-As{sub 2}Te{sub 3} system. Black-Right-Pointing-Pointer Characterization of macroscopic properties of the new CdTe-AgI-As{sub 2}Te{sub 3} glasses. Black-Right-Pointing-Pointer Characterization of the total conductivity of CdTe-AgI-As{sub 2}Te{sub 3} glasses. Black-Right-Pointing-Pointer Comparison between the selenide and telluride equivalent systems. -- Abstract: Chalcogenide glasses in the pseudo-ternary CdTe-AgI-As{sub 2}Te{sub 3} system were synthesized and the glass-forming range was determined. The maximum content of CdTe in this glass system was found to be equal to 15 mol.%. The macroscopic characterizations of samples have consisted in Differential Scanning Calorimetry, density, and X-ray diffraction measurements. The cadmium telluride addition does not generate any significant change in the glass transition temperature but the resistance of binary AgI-As{sub 2}Te{sub 3} glasses towards crystallisation is estimated to be decreasing on the base of {Delta}T = T{sub x} - T{sub g} parameter. The total electrical conductivity {sigma} was measured by complex impedance spectroscopy. First, the CdTe additions in the (AgI){sub 0.5}(As{sub 2}Te{sub 3}){sub 0.5} host glass, (CdTe){sub x}(AgI){sub 0.5-x/2}(As{sub 2}Te{sub 3}){sub 0.5-x/2} lead to a conductivity decrease at x {<=} 0.05. Then, the behaviour is reversed at 0.05 {<=} x {<=} 0.15. The obtained results are discussed by comparison with the equivalent selenide system.

  7. Modeling of Copper Migration In CdTe Photovoltaic Devices

    Science.gov (United States)

    Guo, Da

    Thin-film modules of all technologies often suffer from performance degradation over time. Some of the performance changes are reversible and some are not, which makes deployment, testing, and energy-yield prediction more challenging. The most commonly alleged causes of instability in CdTe device, such as "migration of Cu," have been investigated rigorously over the past fifteen years. As all defects, intrinsic or extrinsic, interact with the electrical potential and free carriers so that charged defects may drift in the electric field and changing ionization state with excess free carriers. Such complexity of interactions in CdTe makes understanding of temporal changes in device performance even more challenging. The goal of the work in this dissertation is, thus, to eliminate the ambiguity between the observed performance changes under stress and their physical root cause by enabling a depth of modeling that takes account of diffusion and drift at the atomistic level coupled to the electronic subsystem responsible for a PV device's function. The 1D Unified Solver, developed as part of this effort, enables us to analyze PV devices at a greater depth. In this dissertation, the implementation of a drift-diffusion model defect migration simulator, development of an implicit reaction scheme for total mass conservation, and a couple of other numerical schemes to improve the overall flexibility and robustness of this coupled Unified Solver is discussed. Preliminary results on Cu (with or without Cl-treatment) annealing simulations in both single-crystal CdTe wafer and poly-crystalline CdTe devices show promising agreement to experimental findings, providing a new perspective in the research of improving doping concentration hence the open-circuit voltage of CdTe technology. Furthermore, on the reliability side, in agreement of previous experimental reports, simulation results suggest possibility of Cu depletion in short-circuited cells stressed at elevated temperature

  8. Recent advances in Tl Br, Cd Te and CdZnTe semiconductor radiation detectors: a review

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Icimone B. [Universidade Bandeirante (UNIBAN), Sao Paulo, SP (Brazil)

    2011-07-01

    The success in the development of radiation spectrometers operating at room temperature is based on many years of effort on the part of large numbers of workers around the world. These individuals have contributed to the understanding of the fundamental materials issues associated with the growth of semiconductors for this application, the development of device fabrication and processing technology, and advances in low noise electronics and pulse processing. Progress in this field continues at an accelerated pace, as in evidenced by the improvements in detector performance and by the growing number of commercial products. Thus, the last years have been seen continued effort in the development of room temperature compound semiconductors devices. High-Z compound semiconductor detectors has been explored for high energy resolution, high detection efficiency and are of low cost. Compound semiconductors detectors are well suited for addressing needs of demanding applications such as bore hole logging where high operating temperature are encountered. In this work recent developments in semiconductors detectors were reviewed. This review concentrated on thallium bromide (TlBr), cadmium zinc telluride (CdZnTe) and cadmium telluride (CdTe) crystals detectors. TlBr has higher stopping power compared to common semiconductor materials because it has the higher photoelectric and total attenuation coefficients over wide energy range from 100 keV to 1 MeV. CdTe and CdZnTe detectors have several attractive features for detecting X-ray and low energy gamma ray. Their relatively large band gaps lead to a relatively low leakage current and offer an excellent energy resolution at room temperature. A literature survey and bibliography was also included. (author)

  9. Single photon emission from charged excitons in CdTe/ZnTe quantum dots

    Science.gov (United States)

    Belyaev, K. G.; Rakhlin, M. V.; Sorokin, S. V.; Klimko, G. V.; Gronin, S. V.; Sedova, I. V.; Mukhin, I. S.; Ivanov, S. V.; Toropov, A. A.

    2017-11-01

    We report on micro-photoluminescence studies of individual self-organized CdTe/ZnTe quantum dots intended for single-photon-source applications in a visible spectral range. The quantum dots surface density below 1010 per cm2 was achieved by using a thermally activated regime of molecular beam epitaxy that allowed fabrication of etched mesa-structures containing only a few emitting quantum dots. The single photon emission with the autocorrelation function g(2)(0)<0.2 was detected and identified as recombination of charged excitons in the individual quantum dot.

  10. Performance and Metastability of CdTe Solar Cells with a Te Back-Contact Buffer Layer

    Science.gov (United States)

    Moore, Andrew

    Thin-film CdTe photovoltaics are quickly maturing into a viable clean-energy solution through demonstration of competitive costs and performance stability with existing energy sources. Over the last half decade, CdTe solar technology has achieved major gains in performance; however, there are still aspects that can be improved to progress toward their theoretical maximum efficiency. Perhaps equally valuable as high photovoltaic efficiency and a low levelized cost of energy, is device reliability. Understanding the root causes for changes in performance is essential for accomplishing long-term stability. One area for potential performance enhancement is the back contact of the CdTe device. This research incorporated a thin-film Te-buffer layer into the contact structure, between the CdTe and contact metal. The device performance and characteristics of many different back contact configurations were rigorously studied. CdTe solar cells fabricated with the Te-buffer contact showed short-circuit current densities and open-circuit voltages that were on par with the traditional back-contacts used at CSU. However, the Te-buffer contact typically produced 2% larger fill-factors on average, leading to greater conversation efficiency. Furthermore, using the Te buffer allowed for incorporation of 50% less Cu, which is used for p-type doping but is also known to decrease lifetime and stability. This resulted in an additional 3% fill-factor gain with no change in other parameters compared to the standard-Cu treated device. In order to better understand the physical mechanisms of the Te-buffer contact, electrical and material properties of the Te layer were extracted and used to construct a simple energy band diagram. The Te layer was found to be highly p-type (>1018 cm-3) and possess a positive valence-band offset of 0.35-0.40 eV with CdTe. An existing simulation model incorporating the Te-layer properties was implemented and validated by comparing simulated results of CdTe

  11. Stokes shift and fine-structure splitting in CdSe / CdTe invert type-II ...

    Indian Academy of Sciences (India)

    Worasak Sukkabot

    2018-01-09

    Jan 9, 2018 ... that the Stokes shift and fine-structure splitting (FSS) in semiconductor core/shell nanocrystals are predominantly affected by the shell thickness and band profiles. CdSe/CdTe invert type-II and CdTe/CdSe type-II core/shell nanocrystals are used as the simulated candidates in order to obtain the different ...

  12. Reformulated tight binding calculation for band discontinuity at CdTe/Hg xCd1-xTe heterointerfaces and their type I-type III transitions

    International Nuclear Information System (INIS)

    Ekpunobi, A.J.

    2005-01-01

    A recently reformulated tight binding method is used to calculate the valence band discontinuity at the CdTe/Hg x Cd 1-x Te interface in the s 2 p 2 configuration. The calculated valence band discontinuity of 0.31 eV at CdTe/HgTe interface is in good agreement with self-consistent calculation and accepted experimental value. Calculations were extended to alloy interfaces, which enabled the investigation of the band-offset problem at the transition point. Both valence band discontinuity ratio and conduction band discontinuity ratio show inflexions at the transition point

  13. Reassignment of oxygen-related defects in CdTe and CdSe

    Energy Technology Data Exchange (ETDEWEB)

    Bastin, Dirk

    2015-05-22

    This thesis reassigns the O{sub Te}-V{sub Cd} complex in CdTe and the O{sub Se}-V{sub Cd} complex in CdSe to a sulfur-dioxygen complex SO{sub 2}*, and the O{sub Cd} defect in CdSe to a V{sub Cd}H{sub 2} complex using Fourier transformed infrared absorption spectroscopy. The publications of the previous complexes were investigated by theoreticians who performed first-principle calculations of theses complexes. The theoreticians ruled out the assignments and proposed alternative defects, instead. The discrepancy between the experimentally obtained and theoretically proposed defects was the motivation of this work. Two local vibrational modes located at 1096.8 (ν{sub 1}) and 1108.3 cm{sup -1} (ν{sub 2}) previously assigned to an O{sub Te}-V{sub Cd} complex are detected in CdTe single crystals doped with CdSO{sub 4} powder. Five weaker additional absorption lines accompanying ν{sub 1} and ν{sub 2} could be detected. The relative intensities of the absorption lines match a sulfur-dioxygen complex SO{sub 2}* having two configurations labeled ν{sub 1} and ν{sub 2}. A binding energy difference of 0.5±0.1 meV between the two configurations and an energy barrier of 53±4 meV separating the two configurations are determined. Uniaxial stress applied to the crystal leads to a splitting of the absorption lines which corresponds to an orthorhombic and monoclinic symmetry for ν{sub 1} and ν{sub 2}, respectively. In virgin and oxygen-doped CdSe single crystals, three local vibrational modes located at 1094.1 (γ{sub 1}), 1107.5 (γ{sub 2}), and 1126.3 cm{sup -1} (γ{sub 3}) previously attributed to an O{sub Se}-V{sub Cd} complex could be observed. The signals are accompanied by five weaker additional absorption features in their vicinity. The additional absorption lines are identified as isotope satellites of a sulfur-dioxygen complex SO{sub 2}* having three configurations γ{sub 1}, γ{sub 2}, and γ{sub 3}. IR absorption measurements with uniaxial stress applied to the

  14. First results of a highly granulated 3D CdTe detector module for PET

    Science.gov (United States)

    Chmeissani, Mokhtar; Kolstein, Machiel; Macias-Montero, José Gabriel; Puigdengoles, Carles; García, Jorge; Prats, Xavier; Martínez, Ricardo

    2018-01-01

    We present the performance of a highly granulated 3D detector module for PET, consisting of a stack of pixelated CdTe detectors. Each detector module has 2 cm  ×  2 cm  ×  2 cm of CdTe material, subdivided into 4000 voxels, where each voxel has size 1 mm  ×  1 mm  ×  2 mm and is connected to its own read-out electronics via a BiSn solder ball. Each read-out channel consists of a preamp, a discriminator, a shaper, a peak-and-hold circuit and a 10 bits SAR ADC. The preamp has variable gain where at the maximum gain the ADC resolution is equivalent to 0.7 keV. Each ASIC chip reads 100 CdTe pixel channels and has one TDC to measure the time stamp of the triggered events, with a time resolution of less than 1 ns. With the bias voltage set at  ‑250 V mm‑1 and for 17838 working channels out of a total of 20 000, we have obtained an average energy resolution of 2.2% FWHM for 511 keV photons. For 511 keV photons that have undergone Compton scattering, we measured an energy resolution of 3.2% FWHM. A timing resolution for PET coincidence events of 60 ns FWHM was found.

  15. Coexistence of optically active radial and axial CdTe insertions in single ZnTe nanowire

    Science.gov (United States)

    Wojnar, P.; Płachta, J.; Zaleszczyk, W.; Kret, S.; Sanchez, Ana M.; Rudniewski, R.; Raczkowska, K.; Szymura, M.; Karczewski, G.; Baczewski, L. T.; Pietruczik, A.; Wojtowicz, T.; Kossut, J.

    2016-03-01

    We report on the growth, cathodoluminescence and micro-photoluminescence of individual radial and axial CdTe insertions in ZnTe nanowires. In particular, the cathodoluminescence technique is used to determine the position of each emitting object inside the nanowire. It is demonstrated that depending on the CdTe deposition temperature, one can obtain an emission either from axial CdTe insertions only, or from both, radial and axial heterostructures, simultaneously. At 350 °C CdTe grows only axially, whereas at 310 °C and 290 °C, there is also significant deposition on the nanowire sidewalls resulting in radial core/shell heterostructures. The presence of Cd atoms on the sidewalls is confirmed by energy dispersive X-ray spectroscopy. Micro-photoluminescence study reveals a strong linear polarization of the emission from both types of heterostructures in the direction along the nanowire axis.We report on the growth, cathodoluminescence and micro-photoluminescence of individual radial and axial CdTe insertions in ZnTe nanowires. In particular, the cathodoluminescence technique is used to determine the position of each emitting object inside the nanowire. It is demonstrated that depending on the CdTe deposition temperature, one can obtain an emission either from axial CdTe insertions only, or from both, radial and axial heterostructures, simultaneously. At 350 °C CdTe grows only axially, whereas at 310 °C and 290 °C, there is also significant deposition on the nanowire sidewalls resulting in radial core/shell heterostructures. The presence of Cd atoms on the sidewalls is confirmed by energy dispersive X-ray spectroscopy. Micro-photoluminescence study reveals a strong linear polarization of the emission from both types of heterostructures in the direction along the nanowire axis. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08806b

  16. Hyperfine and ion beam interaction studies of Sn, Te, I and Sm impurities in silicon

    International Nuclear Information System (INIS)

    Kemerink, G.J.

    1981-01-01

    In this thesis the author reports investigations on ion implanted and oven or laser annealed silicon using Moessbauer spectroscopy, Rutherford backscattering (RBS) and channeling, time differential perturbed angular correlation and the Hall-effect. Chapter 1 gives an introduction to this field of research. Chapter 2 deals with an outline of the experimental methods used throughout this work. In chapter 3 results are presented from RBS and channeling experiments on Te-implanted Si. Chapters 4 and 5 concern the results from a study of dopant dependent effects in laser annealed TeSi using 119 Sn, 125 Te and 129 I-Moessbauer spectroscopy. Chapter 6 gives the results from a study of as-implanted and oven annealed TeSi using 129 I-time differential perturbed angular correlation and 129 I-Moessbauer spectroscopy. Chapter 7 describes the results from RBS and channeling experiments on oven and laser annealed ISi. Chapter 8 deals with Hall-effect measurements on TeSi and ISi. Chapter 9 finally covers the investigations of 153 Sm-implanted diamond, Si, Ge and α-Sn using channeling and 153 Eu-Moessbauer spectroscopy. (Auth.)

  17. Preparation and characterization of pulsed laser deposited a novel CdS/CdSe composite window layer for CdTe thin film solar cell

    International Nuclear Information System (INIS)

    Yang, Xiaoyan; Liu, Bo; Li, Bing; Zhang, Jingquan; Li, Wei; Wu, Lili; Feng, Lianghuan

    2016-01-01

    Highlights: • Novel CdS/CdSe composite windows for CdTe cell were prepared by pulsed laser deposition. • SEM images show that CdS/CdSe composite windows are stacking together as the design. • CdTe cells with CdS/CdSe composite windows improved the blue response. • CdTe cells with composite windows show an obvious red shift in the absorption edge. • The volume proportion of CdSe affects the performance of CdTe solar cell. - Abstract: A novel CdS/CdSe composite window structure was designed and then the corresponding films were prepared by pulsed laser deposition as an improved window layer for CdTe-based solar cells. Two types of this composite window structure with 5 cycles and 10 cycles CdS/CdSe respectively both combined with CdS layers were prepared at 200 °C compared with pure CdS window layer and finally were applied into CdTe thin film solar cells. The cross section and surface morphology of the two composite window layers were monitored by using scanning electron microscopy and the result shows that the pulsed laser deposited composite window layers with good crystallinity are stacking together as the design. The devices based on CdS/CdSe composite window layers have demonstrated the enhanced photocurrent collection from both short and long wavelength regions compared to CdS/CdTe solar cell. The efficiency of the best reference CdS/CdTe solar cell was 10.72%. And the device with 5 cycles CdS/CdSe composite window showed efficiency of 12.61% with V OC of 772.92 mV, J SC of 25.11 mA/cm 2 and FF of 64.95%. In addition, there are some differences which exist within the optical transmittance spectra and QE curves between the two CdS/CdSe composite window samples, indicating that the volume proportion of CdSe may influence the performance of CdTe thin film solar cell.

  18. Preparation and characterization of pulsed laser deposited a novel CdS/CdSe composite window layer for CdTe thin film solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaoyan; Liu, Bo; Li, Bing, E-mail: libing70@126.com; Zhang, Jingquan; Li, Wei; Wu, Lili; Feng, Lianghuan

    2016-03-30

    Highlights: • Novel CdS/CdSe composite windows for CdTe cell were prepared by pulsed laser deposition. • SEM images show that CdS/CdSe composite windows are stacking together as the design. • CdTe cells with CdS/CdSe composite windows improved the blue response. • CdTe cells with composite windows show an obvious red shift in the absorption edge. • The volume proportion of CdSe affects the performance of CdTe solar cell. - Abstract: A novel CdS/CdSe composite window structure was designed and then the corresponding films were prepared by pulsed laser deposition as an improved window layer for CdTe-based solar cells. Two types of this composite window structure with 5 cycles and 10 cycles CdS/CdSe respectively both combined with CdS layers were prepared at 200 °C compared with pure CdS window layer and finally were applied into CdTe thin film solar cells. The cross section and surface morphology of the two composite window layers were monitored by using scanning electron microscopy and the result shows that the pulsed laser deposited composite window layers with good crystallinity are stacking together as the design. The devices based on CdS/CdSe composite window layers have demonstrated the enhanced photocurrent collection from both short and long wavelength regions compared to CdS/CdTe solar cell. The efficiency of the best reference CdS/CdTe solar cell was 10.72%. And the device with 5 cycles CdS/CdSe composite window showed efficiency of 12.61% with V{sub OC} of 772.92 mV, J{sub SC} of 25.11 mA/cm{sup 2} and FF of 64.95%. In addition, there are some differences which exist within the optical transmittance spectra and QE curves between the two CdS/CdSe composite window samples, indicating that the volume proportion of CdSe may influence the performance of CdTe thin film solar cell.

  19. Systems and methods for the synthesis of high thermoelectric performance doped-SnTe materials

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Zhifeng; Zhang, Qian; Chen, Gang

    2018-02-27

    A thermoelectric composition comprising tin (Sn), tellurium (Te) and at least one dopant that comprises a peak dimensionless figure of merit (ZT) of 1.1 and a Seebeck coefficient of at least 50 .mu.V/K and a method of manufacturing the thermoelectric composition. A plurality of components are disposed in a ball-milling vessel, wherein the plurality of components comprise tin (Sn), tellurium (Te), and at least one dopant such as indium (In). The components are subsequently mechanically and thermally processed, for example, by hot-pressing. In response to the mechanical-thermally processing, a thermoelectric composition is formed, wherein the thermoelectric composition comprises a dimensionless figure of merit (ZT) of the thermoelectric composition is at least 0.8, and wherein a Seebeck coefficient of the thermoelectric composition is at least 50 .mu.V/K at any temperature.

  20. Giant Pressure-Induced Enhancement of Seebeck Coefficient and Thermoelectric Efficiency in SnTe

    Energy Technology Data Exchange (ETDEWEB)

    Baker, Jason; Kumar, Ravhi; Park, Changyong; Kenney-Benson, Curtis; Cornelius, Andrew; Velisavljevic, Nenad (CIW); (LANL); (UNLV)

    2017-10-30

    The thermoelectric properties of polycrystalline SnTe have been measured up to 4.5 GPa at 330 K. SnTe shows an enormous enhancement in Seebeck coefficient, greater than 200 % after 3 GPa, which correlates to a known pressure-induced structural phase transition that is observed through simultaneous in situ X-ray diffraction measurement. Electrical resistance and relative changes to the thermal conductivity were also measured, enabling the determination of relative changes in the dimensionless figure of merit (ZT), which increases dramatically after 3 GPa, reaching 350 % of the lowest pressure ZT value. The results demonstrate a fundamental relationship between structure and thermoelectric behaviours and suggest that pressure is an effective tool to control them.

  1. Quantum oscillation evidence for a topological semimetal phase in ZrSnTe

    Science.gov (United States)

    Hu, Jin; Zhu, Yanglin; Gui, Xin; Graf, David; Tang, Zhijie; Xie, Weiwei; Mao, Zhiqiang

    2018-04-01

    The layered WHM-type (W =Zr /Hf /La , H =Si /Ge /Sn /Sb , M =S /Se /Te ) materials represent a large family of topological semimetals, which provides an excellent platform to study the evolution of topological semimetal state with the fine tuning of spin-orbit coupling and structural dimensionality for various combinations of W , H , and M elements. In this work, through high field de Haas-van Alphen (dHvA) quantum oscillation studies, we have found evidence for the predicted topological nontrivial bands in ZrSnTe. Furthermore, from the angular dependence of quantum oscillation frequency, we have revealed the three-dimensional Fermi surface topologies of this layered material owing to strong interlayer coupling.

  2. A novel intermediate layer for Au/CdZnTe/FTO photoconductive structure

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yuelu; Wang, Linjun, E-mail: ljwang@shu.edu.cn; Xu, Run; Huang, Jian; Tao, Jun; Meng, Hua; Zhang, Jijun; Min, Jiahua

    2016-12-01

    Highlights: • Graphene layer was spin-coated on CdZnTe to form Au/graphene/CdZnTe/FTO structure. • Graphene layer can significantly improve the contact property of Au/CdZnTe. • Graphene layer can obviously enhance UV photo-response of CdZnTe. • Graphene is a potential buffer material for CdZnTe based high-energy detectors. - Abstract: In this work, graphene is tried to use to improve the performance of polycrystalline CdZnTe high-energy radiation and photon detectors. A graphene intermediate layer is prepared by spin-coating process on the surface of polycrystalline CdZnTe film, which forms a photoconductive Au/graphene/CdZnTe/FTO structure. XRD, Raman, photoelectric response and other characterisation methods are adopted to investigate the effect of graphene layer on the electrical characteristics and UV photo-response performance of CdZnTe photoconductive structure. It is demonstrated that graphene layer can significantly improve the contact property of Au/CdZnTe structure, and obviously enhance its UV photo-response and the UV sensitivity increased with one order of magnitude.

  3. Nanocrystalline CdSnO3 Based Room Temperature Methanol Sensor

    Directory of Open Access Journals (Sweden)

    Shanabhau BAGUL

    2017-04-01

    Full Text Available Synthesis of nanocrystalline CdSnO3 powder by ultrasonic atomizer assisted wet chemical method is reported in this paper. Synthesized CdSnO3 powder was characterized by X-Ray Diffraction (XRD, Field Emission Scanning Electron Microscopy (FESEM and Transmission Electron Microscopy (TEM to examine phase and microstructure. FESEM and TEM analysis reveals that the CdSnO3 powder prepared here is porous monodisperse nanocrystalline in nature, with average particle size of approximately 17 nm or smaller. The material is also characterized by UV-Visible and Photoluminescence (PL spectroscopy. Thick films of synthesized CdSnO3 powder fired at 850 0C are made by using screen printing method. The films surface is modified by using dipping method. CuCl2 (0.005 M dipped (for 2 min thick film shows high response (R= 477 to 100 ppm methanol at room temperature (35 0C. The sensor shows good selectivity and fast response recovery time to methanol. The excellent methanol sensing performance, particularly high response values is observed to be mainly due to porous CdSnO3 surface.

  4. Energy dispersive CdTe and CdZnTe detectors for spectral clinical CT and NDT applications

    Energy Technology Data Exchange (ETDEWEB)

    Barber, W.C., E-mail: william.barber@dxray.com [DxRay, Inc., Northridge, CA (United States); Interon AS, Asker (Norway); Wessel, J.C. [DxRay, Inc., Northridge, CA (United States); Interon AS, Asker (Norway); Nygard, E. [Interon AS, Asker (Norway); Iwanczyk, J.S. [DxRay, Inc., Northridge, CA (United States)

    2015-06-01

    We are developing room temperature compound semiconductor detectors for applications in energy-resolved high-flux single x-ray photon-counting spectral computed tomography (CT), including functional imaging with nanoparticle contrast agents for medical applications and non-destructive testing (NDT) for security applications. Energy-resolved photon-counting can provide reduced patient dose through optimal energy weighting for a particular imaging task in CT, functional contrast enhancement through spectroscopic imaging of metal nanoparticles in CT, and compositional analysis through multiple basis function material decomposition in CT and NDT. These applications produce high input count rates from an x-ray generator delivered to the detector. Therefore, in order to achieve energy-resolved single photon counting in these applications, a high output count rate (OCR) for an energy-dispersive detector must be achieved at the required spatial resolution and across the required dynamic range for the application. The required performance in terms of the OCR, spatial resolution, and dynamic range must be obtained with sufficient field of view (FOV) for the application thus requiring the tiling of pixel arrays and scanning techniques. Room temperature cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) compound semiconductors, operating as direct conversion x-ray sensors, can provide the required speed when connected to application specific integrated circuits (ASICs) operating at fast peaking times with multiple fixed thresholds per pixel provided the sensors are designed for rapid signal formation across the x-ray energy ranges of the application at the required energy and spatial resolutions, and at a sufficiently high detective quantum efficiency (DQE). We have developed high-flux energy-resolved photon-counting x-ray imaging array sensors using pixellated CdTe and CdZnTe semiconductors optimized for clinical CT and security NDT. We have also fabricated high

  5. Energy dispersive CdTe and CdZnTe detectors for spectral clinical CT and NDT applications

    International Nuclear Information System (INIS)

    Barber, W.C.; Wessel, J.C.; Nygard, E.; Iwanczyk, J.S.

    2015-01-01

    We are developing room temperature compound semiconductor detectors for applications in energy-resolved high-flux single x-ray photon-counting spectral computed tomography (CT), including functional imaging with nanoparticle contrast agents for medical applications and non-destructive testing (NDT) for security applications. Energy-resolved photon-counting can provide reduced patient dose through optimal energy weighting for a particular imaging task in CT, functional contrast enhancement through spectroscopic imaging of metal nanoparticles in CT, and compositional analysis through multiple basis function material decomposition in CT and NDT. These applications produce high input count rates from an x-ray generator delivered to the detector. Therefore, in order to achieve energy-resolved single photon counting in these applications, a high output count rate (OCR) for an energy-dispersive detector must be achieved at the required spatial resolution and across the required dynamic range for the application. The required performance in terms of the OCR, spatial resolution, and dynamic range must be obtained with sufficient field of view (FOV) for the application thus requiring the tiling of pixel arrays and scanning techniques. Room temperature cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) compound semiconductors, operating as direct conversion x-ray sensors, can provide the required speed when connected to application specific integrated circuits (ASICs) operating at fast peaking times with multiple fixed thresholds per pixel provided the sensors are designed for rapid signal formation across the x-ray energy ranges of the application at the required energy and spatial resolutions, and at a sufficiently high detective quantum efficiency (DQE). We have developed high-flux energy-resolved photon-counting x-ray imaging array sensors using pixellated CdTe and CdZnTe semiconductors optimized for clinical CT and security NDT. We have also fabricated high

  6. Compensation models in chlorine doped CdTe based on positron annihilation and photoluminescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stadler, W.; Hofman, D.M.; Meyer, B.K. [Technische Universitaet Muenchen, Garching (Germany); Krause-Rehberg, R.; Polity, A.; Abgarjan, Th. [Martin-Luther Universitaet Halle-Wittenberg, FB Physik, Halle (Germany); Salk, M.; Benz, K.W. [Kristallographisches Institut, Universitaet Freiburg, Freiburg (Germany); Azoulay, M. [Soreq, Nuclear Research Centre, Yavne (Israel)

    1995-12-31

    In this investigation positron annihilation, photoluminescence and electron paramagnetic resonance techniques are employed to gain insight in the compensation of CdTe doped with the halogen Cl. We will demonstrate that the high resistivity of CdTe:Cl cannot be explain by the interaction between the shallow effective mass type donor Cl on Te site and the doping induced shallow acceptor complex, a Cd vacancy paired off with a nearest-neighbour Cl atom (A centre). From electron paramagnetic resonance investigations we conclude that the mid gap trap, often detected by electrical methods in CdTe, is not the isolated Cd vacancy. (author). 9 refs, 2 figs, 1 tab.

  7. Fractal features of CdTe thin films grown by RF magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Hosseinpanahi, Fayegh, E-mail: f.hosseinpanahi@yahoo.com [Department of Physics, Payame Noor University, P.O. Box 19395-4697, Tehran (Iran, Islamic Republic of); Raoufi, Davood [Department of Physics, University of Bu Ali Sina, P.O. Box 65174, Hamedan (Iran, Islamic Republic of); Ranjbarghanei, Khadijeh [Department of Physics, Plasma Physics Research Center, Science & Research Branch Islamic Azad University, Tehran (Iran, Islamic Republic of); Karimi, Bayan [Department of Physics, Payame Noor University, P.O. Box 19395-4697, Tehran (Iran, Islamic Republic of); Babaei, Reza [Department of Physics, Plasma Physics Research Center, Science & Research Branch Islamic Azad University, Tehran (Iran, Islamic Republic of); Hasani, Ebrahim [Department of Physics, University of Bu Ali Sina, P.O. Box 65174, Hamedan (Iran, Islamic Republic of)

    2015-12-01

    Graphical abstract: - Highlights: • CdTe thin films were deposited on glass substrates by RF magnetron sputtering at room temperature with different deposition time 5, 10 and 15 min. • Nanostructure of CdTe layer indicates that CdTe films are polycrystalline and have zinc blende structure, irrespective of their deposition time. • Complexity and roughness of the CdTe films and strength of multifractality increase with increasing deposition time. • Detrended fluctuation analysis (DFA) and also multifractal detrended fluctuation analysis (MFDFA) methods showed that prepared CdTe films have multifractal nature. - Abstract: Cadmium telluride (CdTe) thin films were prepared by RF magnetron sputtering on glass substrates at room temperature (RT). The film deposition was performed for 5, 10, and 15 min at power of 30 W with a frequency of 13.56 MHz. The crystal structure of the prepared CdTe thin films was studied by X-ray diffraction (XRD) technique. XRD analyses indicate that the CdTe films are polycrystalline, having zinc blende structure of CdTe irrespective of their deposition time. All CdTe films showed a preferred orientation along (1 1 1) crystalline plane. The surface morphology characterization of the films was studied using atomic force microscopy (AFM). The quantitative AFM characterization shows that the RMS surface roughness of the prepared CdTe thin films increases with increasing the deposition time. The detrended fluctuation analysis (DFA) and also multifractal detrended fluctuation analysis (MFDFA) methods showed that prepared CdTe thin films have multifractal nature. The complexity, roughness of the CdTe thin films and strength of the multifractality increase as deposition time increases.

  8. Fractal features of CdTe thin films grown by RF magnetron sputtering

    International Nuclear Information System (INIS)

    Hosseinpanahi, Fayegh; Raoufi, Davood; Ranjbarghanei, Khadijeh; Karimi, Bayan; Babaei, Reza; Hasani, Ebrahim

    2015-01-01

    Graphical abstract: - Highlights: • CdTe thin films were deposited on glass substrates by RF magnetron sputtering at room temperature with different deposition time 5, 10 and 15 min. • Nanostructure of CdTe layer indicates that CdTe films are polycrystalline and have zinc blende structure, irrespective of their deposition time. • Complexity and roughness of the CdTe films and strength of multifractality increase with increasing deposition time. • Detrended fluctuation analysis (DFA) and also multifractal detrended fluctuation analysis (MFDFA) methods showed that prepared CdTe films have multifractal nature. - Abstract: Cadmium telluride (CdTe) thin films were prepared by RF magnetron sputtering on glass substrates at room temperature (RT). The film deposition was performed for 5, 10, and 15 min at power of 30 W with a frequency of 13.56 MHz. The crystal structure of the prepared CdTe thin films was studied by X-ray diffraction (XRD) technique. XRD analyses indicate that the CdTe films are polycrystalline, having zinc blende structure of CdTe irrespective of their deposition time. All CdTe films showed a preferred orientation along (1 1 1) crystalline plane. The surface morphology characterization of the films was studied using atomic force microscopy (AFM). The quantitative AFM characterization shows that the RMS surface roughness of the prepared CdTe thin films increases with increasing the deposition time. The detrended fluctuation analysis (DFA) and also multifractal detrended fluctuation analysis (MFDFA) methods showed that prepared CdTe thin films have multifractal nature. The complexity, roughness of the CdTe thin films and strength of the multifractality increase as deposition time increases.

  9. Optical band gap of Sn0⋅ 2Bi1⋅ 8Te3 thin films

    Indian Academy of Sciences (India)

    Sn0.2Bi1.8Te3 thin films were grown using the thermal evaporation technique on a (001) face of NaCl crystal as a substrate at room temperature. The optical absorption was measured in the wave number range 500–4000 cm-1. From the optical absorption data the band gap was evaluated and studied as a function of film ...

  10. On the doping problem of CdTe films: The bismuth case

    Energy Technology Data Exchange (ETDEWEB)

    Vigil-Galan, O. [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico); Brown, M. [Department of Physics and Astronomy, The University of Toledo, 43606 Toledo, OH (United States); Ruiz, C.M. [Depto. Fisica de Materiales, Universidad Autonoma de Madrid, 28049 Madrid (Spain); Vidal-Borbolla, M.A. [Instituto de Investigacion en Comunicacion Optica, Av. Karakorum 1470, Lomas 4a. Secc., 78210 San Luis Potosi, SLP (Mexico); Ramirez-Bon, R. [CINVESTAV-IPN, U. Queretaro, Libramiento Norponiente No. 2000, Fracc. Real de Juriquilla, 76230 Santiago de Queretaro, Qro. (Mexico); Sanchez-Meza, E. [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico); Tufino-Velazquez, M. [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico)], E-mail: mtufinovel@yahoo.com.mx; Calixto, M. Estela [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico); Compaan, A.D. [Department of Physics and Astronomy, The University of Toledo, 43606 Toledo, OH (United States); Contreras-Puente, G. [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico)

    2008-08-30

    The controlled increase of hole concentration is an important issue and still an unsolved problem for polycrystalline CdTe-based solar cells. The typical hole concentration of as-grown CdTe thin-films goes up to 10{sup 13} cm{sup -3}, depending on the specific growth technique. The highest electron concentration obtained for CdS, the suitable window partner material of CdTe, is around 10{sup 15} cm{sup -3}. Thus, the PV-performance of a CdS/CdTe device can be optimized if the hole concentration in CdTe is increased. We have faced up this problem by studying the electrical properties of two types of CdTe films: CdTe films grown by Close Space Vapor Transport using a CdTe:Bi powder as the starting material and CdTe sputtered films doped by implantation with different Bi-doses. Temperature-dependent resistivity and Hall effect measurements and a discussion on the efficiency of both doping processes are presented.

  11. CdTe polycrystalline films on Ni foil substrates by screen printing and their photoelectric performance

    International Nuclear Information System (INIS)

    Yao, Huizhen; Ma, Jinwen; Mu, Yannan; Su, Shi; Lv, Pin; Zhang, Xiaoling; Zhou, Liying; Li, Xue; Liu, Li; Fu, Wuyou; Yang, Haibin

    2015-01-01

    Highlights: • The sintered CdTe polycrystalline films by a simple screen printing. • The flexible Ni foil was chose as substrates to reduce the weight of the electrode. • The compact CdTe film was obtained at 550 °C sintering temperature. • The photoelectric activity of the CdTe polycrystalline films was excellent. - Abstract: CdTe polycrystalline films were prepared on flexible Ni foil substrates by sequential screen printing and sintering in a nitrogen atmosphere for the first time. The effect of temperature on the quality of the screen-printed film was investigated in our work. The high-quality CdTe films were obtained after sintering at 550 °C for 2 h. The properties of the sintered CdTe films were characterized by scanning electron microscopy, X-ray diffraction pattern and UV–visible spectroscopy. The high-quality CdTe films have the photocurrent was 2.04 mA/cm 2 , which is higher than that of samples prepared at other temperatures. Furthermore, CdCl 2 treatment reduced the band gap of the CdTe film due to the larger grain size. The photocurrent of photoelectrode based on high crystalline CdTe polycrystalline films after CdCl 2 treatment improved to 2.97 mA/cm 2 , indicating a potential application in photovoltaic devices

  12. On the doping problem of CdTe films: The bismuth case

    International Nuclear Information System (INIS)

    Vigil-Galan, O.; Brown, M.; Ruiz, C.M.; Vidal-Borbolla, M.A.; Ramirez-Bon, R.; Sanchez-Meza, E.; Tufino-Velazquez, M.; Calixto, M. Estela; Compaan, A.D.; Contreras-Puente, G.

    2008-01-01

    The controlled increase of hole concentration is an important issue and still an unsolved problem for polycrystalline CdTe-based solar cells. The typical hole concentration of as-grown CdTe thin-films goes up to 10 13 cm -3 , depending on the specific growth technique. The highest electron concentration obtained for CdS, the suitable window partner material of CdTe, is around 10 15 cm -3 . Thus, the PV-performance of a CdS/CdTe device can be optimized if the hole concentration in CdTe is increased. We have faced up this problem by studying the electrical properties of two types of CdTe films: CdTe films grown by Close Space Vapor Transport using a CdTe:Bi powder as the starting material and CdTe sputtered films doped by implantation with different Bi-doses. Temperature-dependent resistivity and Hall effect measurements and a discussion on the efficiency of both doping processes are presented

  13. Nonstoichiometric composition shift in physical vapor deposition of CdTe thin films

    Science.gov (United States)

    Chin, Ken K.; Cheng, Zimeng; Delahoy, Alan E.

    2015-05-01

    While it is being debated whether Cd vacancy is an effective p-dopant in CdTe, and whether CdTe thin film in solar energy application should be Cd-deficient or Cd-rich, in the theory of CdTe physical vapor deposition (PVD) it has been assumed that both the source material and the thin film product is stoichiometric. To remediate the lack of effective theory, a new PVD model for CdTe photovoltaic (PV) modules is presented in this work, in which the composition of the CdTe thin film under growth is a parameter determined by the source CdTe composition as well as the growth condition. The solid phase Cd1-δTe1+δ compound under deposition temperature is treated as a solid solution with a mole of excess pure Te or Cd as solute and one mole of congruently grown CdTe as solvent. Assuming that the vapor pressure of Te2 can be calculated by using the law of solid solution PTe=H0+aH1+a2H2 round the congruent composition, where the molar number a and the constants H0, H1 and H2 as functions of temperature T are extracted from the experimental data. Thus, the mole fraction of solute in the grown CdTe thin film as well as the growth rate, as a function of the solute mole fraction in the source CdTe can be determined.

  14. Cancer Cell Targeting Using Folic Acid/Anti-HER2 Antibody Conjugated Fluorescent CdSe/CdS/ZnS-MPA and CdTe-MSA Quantum Dots.

    Science.gov (United States)

    Singh, Gurpal; Kumar, Manoj; Soni, Udit; Arora, Vikas; Bansal, Vivek; Gupta, Dikshi; Bhat, Madhusudan; Dinda, Amit K; Sapra, Sameer; Singh, Harpal

    2015-12-01

    CdSe/CdS/ZnS and CdTe quantum dots (QDs) were synthesized by successive ion layer adsorption and reaction (SILAR) technique and direct aqueous synthesis respectively using thiol stabilizers. Synthesized CdSe/CdS/ZnS and CdTe QDs stabilized with 3-mercaptopropionic acid (MPA) and mercaptosuccinic acid (MSA) were used as fluorescent labels after conjugation with folic acid (FA) and anti-HER2 antibodies. Photoluminescence quantum yield of folated CdSe/CdS/ZnS-MPA and CdTe-MSA QDs was 59% and 77% than that of non-folated hydrophilic QDs. The folate receptor-mediated delivery of folic acid-conjugated CdTe-MSA and CdSe/CdS/ZnS-MPA QDs showed higher cellular internalization as observed by confocal laser scanning microscopic studies. Folated and non-folated CdTe-MSA QDs were highly toxic and exhibited only 10% cell viability as compared to > 80% cell viability with CdSe/CdS/ZnS-MPA QDs over the concentration ranging from 3.38 to 50 pmoles. Immunohistochemistry (IHC) results of human breast cancer tissue samples showed positive results with anti-HER2 antibody conjugated CdSe/CdS/ZnS-MPA QDs with better sensitivity and specificity as compared to conventional IHC analysis using diaminobenzedene staining.

  15. Admittance of MIS-Structures Based on HgCdTe with a Double-Layer CdTe/Al2O3 Insulator

    Science.gov (United States)

    Dzyadukh, S. M.; Voitsekhovskii, A. V.; Nesmelov, S. N.; Sidorov, G. Yu.; Varavin, V. S.; Vasil'ev, V. V.; Dvoretsky, S. A.; Mikhailov, N. N.; Yakushev, M. V.

    2018-03-01

    Admittance of MIS structures based on n(p)- Hg1-xCdxTe (at x from 0.22 to 0.40) with SiO2/Si3N4, Al2O3, and CdTe/Al2O3 insulators is studied experimentally at 77 K. Growth of an intermediate CdTe layer during epitaxy results in the almost complete disappearance of the hysteresis of electrophysical characteristics of MIS structures based on graded-gap n-HgCdTe for a small range of the voltage variation. For a wide range of the voltage variation, the hysteresis of the capacitance-voltage characteristics appears for MIS structures based on n-HgCdTe with the CdTe/Al2O3 insulator. However, the hysteresis mechanism differs from that in case of a single-layer Al2O3 insulator. For MIS structures based on p-HgCdTe, introduction of an additional CdTe layer does not lead to a significant decrease of the hysteresis phenomena, which may be due to the degradation of the interface properties when mercury leaves the film as a result of low-temperature annealing changing the conductivity type of the semiconductor.

  16. CdTe and CdSe quantum dots: synthesis, characterizations and applications in agriculture

    International Nuclear Information System (INIS)

    Ung, Thi Dieu Thuy; Tran, Thi Kim Chi; Pham, Thu Nga; Nguyen, Quang Liem; Nguyen, Duc Nghia; Dinh, Duy Khang

    2012-01-01

    This paper highlights the results of the whole work including the synthesis of highly luminescent quantum dots (QDs), characterizations and testing applications of them in different kinds of sensors. Concretely, it presents: (i) the successful synthesis of colloidal CdTe and CdSe QDs, their core/shell structures with single- and/or double-shell made by CdS, ZnS or ZnSe/ZnS; (ii) morphology, structural and optical characterizations of the synthesized QDs; and (iii) testing examples of QDs as the fluorescence labels for agricultural-bio-medical objects (for tracing residual pesticide in agricultural products, residual clenbuterol in meat/milk and for detection of H5N1 avian influenza virus in breeding farms). Overall, the results show that the synthesized QDs have very good crystallinity, spherical shape and strongly emit at the desired wavelengths between ∼500 and 700 nm with the luminescence quantum yield (LQY) of 30–85%. These synthesized QDs were used in fabrication of the three testing fluorescence QD-based sensors for the detection of residual pesticides, clenbuterol and H5N1 avian influenza virus. The specific detection of parathion methyl (PM) pesticide at a content as low as 0.05 ppm has been realized with the biosensors made from CdTe/CdS and CdSe/ZnSe/ZnS QDs and the acetylcholinesterase (AChE) enzymes. Fluorescence resonance energy transfer (FRET)-based nanosensors using CdTe/CdS QDs conjugated with 2-amino-8-naphthol-6-sulfonic acid were fabricated that enable detection of diazotized clenbuterol at a content as low as 10 pg ml −1 . For detection of H5N1 avian influenza virus, fluorescence biosensors using CdTe/CdS QDs bound on the surface of chromatophores extracted and purified from bacteria Rhodospirillum rubrum were prepared and characterized. The specific detection of H5N1 avian influenza virus in the range of 3–50 ng μl −1 with a detection limit of 3 ng μL −1 has been performed based on the antibody-antigen recognition. (review)

  17. CdTe and CdSe quantum dots: synthesis, characterizations and applications in agriculture

    Science.gov (United States)

    Dieu Thuy Ung, Thi; Tran, Thi Kim Chi; Nga Pham, Thu; Nghia Nguyen, Duc; Khang Dinh, Duy; Liem Nguyen, Quang

    2012-12-01

    This paper highlights the results of the whole work including the synthesis of highly luminescent quantum dots (QDs), characterizations and testing applications of them in different kinds of sensors. Concretely, it presents: (i) the successful synthesis of colloidal CdTe and CdSe QDs, their core/shell structures with single- and/or double-shell made by CdS, ZnS or ZnSe/ZnS; (ii) morphology, structural and optical characterizations of the synthesized QDs; and (iii) testing examples of QDs as the fluorescence labels for agricultural-bio-medical objects (for tracing residual pesticide in agricultural products, residual clenbuterol in meat/milk and for detection of H5N1 avian influenza virus in breeding farms). Overall, the results show that the synthesized QDs have very good crystallinity, spherical shape and strongly emit at the desired wavelengths between ˜500 and 700 nm with the luminescence quantum yield (LQY) of 30-85%. These synthesized QDs were used in fabrication of the three testing fluorescence QD-based sensors for the detection of residual pesticides, clenbuterol and H5N1 avian influenza virus. The specific detection of parathion methyl (PM) pesticide at a content as low as 0.05 ppm has been realized with the biosensors made from CdTe/CdS and CdSe/ZnSe/ZnS QDs and the acetylcholinesterase (AChE) enzymes. Fluorescence resonance energy transfer (FRET)-based nanosensors using CdTe/CdS QDs conjugated with 2-amino-8-naphthol-6-sulfonic acid were fabricated that enable detection of diazotized clenbuterol at a content as low as 10 pg ml-1. For detection of H5N1 avian influenza virus, fluorescence biosensors using CdTe/CdS QDs bound on the surface of chromatophores extracted and purified from bacteria Rhodospirillum rubrum were prepared and characterized. The specific detection of H5N1 avian influenza virus in the range of 3-50 ng μl-1 with a detection limit of 3 ng μL-1 has been performed based on the antibody-antigen recognition.

  18. Synthesis of CdSe/ZnS and CdTe/ZnS Quantum Dots: Refined Digestive Ripening

    Directory of Open Access Journals (Sweden)

    Sreeram Cingarapu

    2012-01-01

    Full Text Available We report synthesis of CdSe and CdTe quantum dots (QDs from the bulk CdSe and CdTe material by evaporation/co-condensation using the solvated metal atom dispersion (SMAD technique and refined digestive ripening. The outcomes of this new process are (1 the reduction of digestive ripening time by employing ligands (trioctylphosphine oxide (TOPO and oleylamine (OA as capping agent as well as digestive ripening solvent, (2 ability to tune the photoluminescence (PL from 410 nm to 670 nm, (3 demonstrate the ability of SMAD synthesis technique for other semiconductors (CdTe, (4 direct comparison of CdSe QDs growth with CdTe QDs growth based on digestive ripening times, and (5 enhanced PL quantum yield (QY of CdSe QDs and CdTe QDs upon covering with a ZnS shell. Further, the merit of this synthesis is the use of bulk CdSe and CdTe as the starting materials, which avoids usage of toxic organometallic compounds, eliminates the hot injection procedure, and size selective precipitation processes. It also allows the possibility of scale up. These QDs were characterized by UV-vis, photoluminescence (PL, transmission electron microscopy (TEM, high-resolution transmission electron microscopy (HRTEM, X-ray photoelectron spectroscopy (XPS, and powder XRD.

  19. Magnetic circular dichroism of CdTe nanoparticles

    Science.gov (United States)

    Malakhovskii, A. V.; Sokolov, A. E.; Tsipotan, A. S.; Zharkov, S. M.; Zabluda, V. N.

    2018-04-01

    Magnetic circular dichroism (MCD) of water-soluble CdTe nanoparticles was observed in the visible spectral range for the first time. Diameter of nanoparticles varied from 2.3 to 4.5 nm. Absorption and photoluminescence spectra were also recorded. Absorption line at 19400 cm-1 and luminescent line at 18200 cm-1 were observed. Splitting of value 960 cm-1 was revealed in the MCD spectrum. Approximately the same splitting was extracted from the absorption spectrum. The MCD was identified as the temperature independent paramagnetic mixing effect. Nature of the absorption line and of its splitting are discussed.

  20. Study of a new architecture of gamma cameras with Cd/ZnTe/CdTe semiconductors; Etude d'une nouvelle architecture de gamma camera a base de semi-conducteurs CdZnTe /CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Guerin, L

    2007-11-15

    This thesis studies new semi conductors for gammas cameras in order to improve the quality of image in nuclear medicine. The chapter 1 reminds the general principle of the imaging gamma, by describing the radiotracers, the channel of detection and the types of Anger gamma cameras acquisition. The physiological, physical and technological limits of the camera are then highlighted, to better identify the needs of future gamma cameras. The chapter 2 is dedicated to a bibliographical study. At first, semi-conductors used in imaging gamma are presented, and more particularly semi-conductors CDTE and CdZnTe, by distinguishing planar detectors and monolithic pixelated detectors. Secondly, the classic collimators of the gamma cameras, used in clinical routine for the most part of between them, are described. Their geometry is presented, as well as their characteristics, their advantages and their inconveniences. The chapter 3 is dedicated to a state of art of the simulation codes dedicated to the medical imaging and the methods of reconstruction in imaging gamma. These states of art allow to introduce the software of simulation and the methods of reconstruction used within the framework of this thesis. The chapter 4 presents the new architecture of gamma camera proposed during this work of thesis. It is structured in three parts. The first part justifies the use of semiconducting detectors CdZnTe, in particular the monolithic pixelated detectors, by bringing to light their advantages with regard to the detection modules based on scintillator. The second part presents gamma cameras to base of detectors CdZnTe (prototypes or commercial products) and their associated collimators, as well as the interest of an association of detectors CdZnTe in the classic collimators. Finally, the third part presents in detail the HiSens architecture. The chapter 5 describes both software of simulation used within the framework of this thesis to estimate the performances of the Hi

  1. High-Efficiency, Commercial Ready CdTe Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Sites, James R. [Colorado State Univ., Fort Collins, CO (United States)

    2015-11-19

    Colorado State’s F-PACE project explored several ways to increase the efficiency of CdTe solar cells and to better understand the device physics of those cells under study. Increases in voltage, current, and fill factor resulted in efficiencies above 17%. The three project tasks and additional studies are described in detail in the final report. Most cells studied were fabricated at Colorado State using an industry-compatible single-vacuum closed-space-sublimation (CSS) chamber for deposition of the key semiconductor layers. Additionally, some cells were supplied by First Solar for comparison purposes, and a small number of modules were supplied by Abound Solar.

  2. Cu-doped CdS and its application in CdTe thin film solar cell

    Directory of Open Access Journals (Sweden)

    Yi Deng

    2016-01-01

    Full Text Available Cu is widely used in the back contact formation of CdTe thin film solar cells. However, Cu is easily to diffuse from the back contact into the CdTe absorber layer and even to the cell junction interface CdS/CdTe. This phenomenon is generally believed to be the main factor affecting the CdTe solar cell stability. In this study Cu was intentionally doped in CdS thin film to study its effect on the microstructural, optical and electrical properties of the CdS material. Upon Cu doping, the VCd− and the surface-state-related photoluminescence emissions were dramatically decreased/quenched. The presence of Cu atom hindered the recrystallization/coalescence of the nano-sized grains in the as-deposited CdS film during the air and the CdCl2 annealing. CdTe thin film solar cell fabricated with Cu-doped CdS window layers demonstrated much decreased fill factor, which was induced by the increased space-charge recombination near the p-n junction and the worsened junction crystalline quality. Temperature dependent current-voltage curve measurement indicated that the doped Cu in the CdS window layer was not stable at both room and higher temperatures.

  3. Cross talk experiment with two-element CdTe detector and collimator for BNCT-SPECT

    Energy Technology Data Exchange (ETDEWEB)

    Manabe, Masanobu; Ohya, Ryosuke; Saraue, Nobuhide; Sato, Fuminobu; Murata, Isao [Osaka University, Osaka (Japan)

    2016-12-15

    Boron Neutron Capture Therapy (BNCT) is a new radiation therapy. In BNCT, there exists some very critical problems that should be solved. One of the severest problems is that the treatment effect cannot be known during BNCT in real time. We are now developing a SPECT (single photon emission computed tomography) system (BNCT-SPECT), with a cadmium telluride (CdTe) semiconductor detector. BNCT-SPECT can obtain the BNCT treatment effect by measuring 478 keV gamma-rays emitted from the excited state of 7Li nucleus created by 10B(n,α) 7Li reaction. In the previous studies, we investigated the feasibility of the BNCT-SPECT system. As a result, the S/N ratio did not meet the criterion of S/N >1 because deterioration of the S/N ratio occurred caused by the influence of Compton scattering especially due to capture gamma-rays of hydrogen. We thus produced an arrayed detector with two CdTe crystals to test cross talk phenomenon and to examine an anti-coincidence detection possibility. For more precise analysis for the anti-coincidence detection, we designed and made a collimator having a similar performance to the real BNCT-SPECT. We carried out experiments with the collimator to examine the effect of cross talk of scattering gamma-rays between CdTe elements more practically. As a result of measurement the coincidence events were successfully extracted. We are now planning to carry out evaluation of coincidence rate from the measurement and comparison of it with the numerical calculations.

  4. Spontaneous formation of wurzite-CdS/zinc blende-CdTe heterodimers through a partial anion exchange reaction.

    Science.gov (United States)

    Saruyama, Masaki; So, Yeong-Gi; Kimoto, Koji; Taguchi, Seiji; Kanemitsu, Yoshihiko; Teranishi, Toshiharu

    2011-11-09

    Ion exchange of ionic semiconductor nanoparticles (NPs) is a facile method for the synthesis of type-II semiconductor heterostructured NPs with staggered alignment of band edges for photoelectric applications. Through consideration of the crystallographic orientation and strain at the heterointerface, well-designed heterostructures can be constructed through ion exchange reactions. Here we report the selective synthesis of anisotropically phase-segregated cadmium sulfide (CdS)/ cadmium telluride (CdTe) heterodimers via a novel anion exchange reaction of CdS NPs with an organic telluride precursor. The wurtzite-CdS/zinc blende-CdTe heterodimers in this study resulted from spontaneous phase segregation induced by the differences in the crystal structures of the two phases, accompanying a centrosymmetry breaking of the spherical CdS NPs. The CdS/CdTe heterodimers exhibited photoinduced spatial charge separation because of their staggered band-edge alignment.

  5. Vapour growth of Cd(Zn)Te columnar nanopixels into porous alumina

    International Nuclear Information System (INIS)

    Sochinskii, N.V.; Abellan, M.; Martin Gonzalez, M.; Saucedo, E.; Dieguez, E.; Briones, F.

    2006-01-01

    The vapour phase growth (VPG) of CdTe and Cd 1- x Zn x Te was performed in order to investigate the formation of Cd(Zn)Te columnar nanostructures, which could serve as a basis for micropixels usable for further development of X- and gamma-ray high-resolution imaging devices. The possibility to form the 'Cd(Zn)Te-in-porous alumina' nanostructures by VPG has been demonstrated. The Cd(Zn)Te crystals integrated into nanoporous alumina have shown to have photoluminescence properties compatible with those of the bulk crystals and planar epitaxial layers. Further investigations are going on to improve the structural quality of Cd(Zn)Te nanocrystals

  6. Characterization of CdTe Films Deposited at Various Bath Temperatures and Concentrations Using Electrophoretic Deposition

    Directory of Open Access Journals (Sweden)

    Zulkarnain Zainal

    2012-05-01

    Full Text Available CdTe film was deposited using the electrophoretic deposition technique onto an ITO glass at various bath temperatures. Four batch film compositions were used by mixing 1 to 4 wt% concentration of CdTe powder with 10 mL of a solution of methanol and toluene. X-ray Diffraction analysis showed that the films exhibited polycrystalline nature of zinc-blende structure with the (111 orientation as the most prominent peak. From the Atomic Force Microscopy, the thickness and surface roughness of the CdTe film increased with the increase of CdTe concentration. The optical energy band gap of film decreased with the increase of CdTe concentration, and with the increase of isothermal bath temperature. The film thickness increased with respect to the increase of CdTe concentration and bath temperature, and following, the numerical expression for the film thickness with respect to these two variables has been established.

  7. Fabrication of CdTe quantum dots-apoferritin arrays for detection of dopamine

    Science.gov (United States)

    Le, Thi Hoa; Kim, Ji Hyeon; Park, Sang Joon

    2017-06-01

    A method was proposed for detecting dopamine using a two-dimensional CdTe quantum dots (QDs)-apoferritin array fabricated on a modified silicon (Si) surface. First, CdTe QDs were synthesized in the cavity of horse spleen apoferritin (HsAFr). Then, the characterization of CdTe QDs in apoferritin was performed using photoluminescence (PL) spectroscopy. Transmission electron microscopy was used to analyze the size and structure of CdTe QDs. An atomic force microscopy image was obtained to evaluate the topography of the Si surface. In addition, the PL change resulting from the conjugation reaction of the CdTe QDs-apoferritin array with dopamine was investigated. When the array was linked to dopamine, a significant quenching of fluorescence was observed. Accordingly, the CdTe QDs-apoferritin arrays could be employed as useful sensing media for dopamine detection.

  8. Synthesis and characterization of high-ordered CdTe nanorods

    Science.gov (United States)

    Ma, Ligang; Wei, Zelu; Zhang, Fengming; Wu, Xiaoshan

    2015-12-01

    Cadmium telluride (CdTe) materials are an important absorbed layer and development solar energy conversion devices based on nano-fabrication techniques have attracted considerable interest in fabricating optoelectronic devices. Herein, through close-space sublimation method, vertically high-aligned CdTe nanorods are successfully obtained for the first time, with the help of Anodic Aluminum Oxide (AAO) template, which can perfectly control the morphology, diameter, and spacing among the CdTe nanorods. Its the crystal structure and optical properties are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman scattering, and photoluminescence. The results indicate that CdTe nanorods are textured polycrystalline with the cubic phase and bear good crystallinity. In addition, this deposition technique is a clean, inexpensive, high-throughput, versatile and reproducible for obtaining vertically aligned CdTe nanorod, which shows the potential applications in the future for the preparation of CdTe-based nanostructure solar cells.

  9. High Efficiency Thin Film CdTe and a-Si Based Solar Cells: Annual Technical Report, 4 March 1999 - 3 March 2000

    Energy Technology Data Exchange (ETDEWEB)

    Compaan, A. D.; Deng, X.; Bohn, R. G. (The University of Toledo)

    2001-08-29

    This report describes the research on high-efficiency CdTe-based thin-film solar cells and on high-efficiency a-Si-based thin-film solar cells. Implemented a diode-array spectrograph system and used optical emission spectroscopy to help optimize the reactive sputtering of N-doped ZnTe for CdTe back-contact structures. Identified the photoluminescence signatures of various defect states in CdTe related to Cd vacancies, CuCd acceptors, Cu-VCd complexes, and donor-acceptor pairs, and related these states to instabilities in the hole concentration at room temperature. Showed that Cu is an important non-radiative center in CdS, reducing the PL efficiency. Studied band tailing in CdS weakly alloyed with CdTe and CdTe weakly alloyed with CdS. Fabricated superstrate ITO/CdS/CdTe cells on Mo substrates with efficiencies above 7.5%. Collaborated in studies of EXAFS of Cu in CdTe which indicate a Cu-Te bond length of 2.62 {angstrom} or 6.7% shorter than the CdTe, bond in agreement with calculations of Wei et al. Provided assistance to two groups on laser scribing. Comparatively studied the performance of a-SiGe solar cells and properties of a-SiGe single-layer films deposited using a wide range of H dilution, observed transition from a-SiGe to {mu}c-SiGe at high H dilution and the impact on cell performances. Comparatively studied the performance of a-SiGe solar cells and properties of a-SiGe single-layer films with different Ge contents, suitable for use as component cells of triple-junction devices. Fabricated a-Si-based solar cells on ultra-thin stainless-steel substrate (7.5 micron) and obtained equivalent performance and yield as on the regular SS substrates (127 microns). Comparatively studied the performance of a-Si-based solar cells on SS substrates and on SnO2-coated glass substrates. Studied the performance of p-layers deposited under various deposition conditions for n-i-p type solar cells. Performed an analysis for the component cell current-matching within a

  10. High Efficiency Thin Film CdTe and a-Si Based Solar Cells: Annual Technical Report, 4 March 1999 - 3 March 2000; ANNUAL

    International Nuclear Information System (INIS)

    Compaan, A. D.; Deng, X.; Bohn, R. G.

    2001-01-01

    This report describes the research on high-efficiency CdTe-based thin-film solar cells and on high-efficiency a-Si-based thin-film solar cells. Implemented a diode-array spectrograph system and used optical emission spectroscopy to help optimize the reactive sputtering of N-doped ZnTe for CdTe back-contact structures. Identified the photoluminescence signatures of various defect states in CdTe related to Cd vacancies, CuCd acceptors, Cu-VCd complexes, and donor-acceptor pairs, and related these states to instabilities in the hole concentration at room temperature. Showed that Cu is an important non-radiative center in CdS, reducing the PL efficiency. Studied band tailing in CdS weakly alloyed with CdTe and CdTe weakly alloyed with CdS. Fabricated superstrate ITO/CdS/CdTe cells on Mo substrates with efficiencies above 7.5%. Collaborated in studies of EXAFS of Cu in CdTe which indicate a Cu-Te bond length of 2.62(angstrom) or 6.7% shorter than the CdTe, bond in agreement with calculations of Wei et al. Provided assistance to two groups on laser scribing. Comparatively studied the performance of a-SiGe solar cells and properties of a-SiGe single-layer films deposited using a wide range of H dilution, observed transition from a-SiGe to(mu)c-SiGe at high H dilution and the impact on cell performances. Comparatively studied the performance of a-SiGe solar cells and properties of a-SiGe single-layer films with different Ge contents, suitable for use as component cells of triple-junction devices. Fabricated a-Si-based solar cells on ultra-thin stainless-steel substrate (7.5 micron) and obtained equivalent performance and yield as on the regular SS substrates (127 microns). Comparatively studied the performance of a-Si-based solar cells on SS substrates and on SnO2-coated glass substrates. Studied the performance of p-layers deposited under various deposition conditions for n-i-p type solar cells. Performed an analysis for the component cell current-matching within a triple

  11. Migration of Te atoms and structural changes in CdS/CdTe heterojuctions studied by x-ray scattering and fluorescence

    International Nuclear Information System (INIS)

    Kim, S.; Soo, Y.L.; Kioseoglou, G.; Kao, Y.H.; Compaan, A.D.

    2004-01-01

    X-ray reflectivity and angular dependence of x-ray fluorescence (ADXRF) techniques have been employed for a quantitative study of the Te depth profile and structural changes in a series of CdS/CdTe heterojuctions annealed at various temperatures. The temperature dependence of surface roughening and Te migration is observed in both reflectivity and fluorescence experiments. Changes in the interface morphology and Te distribution are quantified by detailed analysis of the ADXRF data with the aid of reflectivity measurements. The results show that a large amount of Te up to 50% could migrate into the CdS layer and suggest that an extra layer of compounds can be formed near the CdS top surface. We have thus demonstrated that the x-ray reflectivity and ADXRF methods can be used as effective tools for nondestructive characterization of the concentration depth profile and interface morphology in layered structures on a nanometer scale

  12. Multichannel Spectroscopic Ellipsometry for CdTe Photovoltaics: from Materials and Interfaces to Solar Cells

    Science.gov (United States)

    Koirala, Prakash

    Spectroscopic ellipsometry (SE) in the mid-infrared to ultraviolet range has been implemented in order to develop and evaluate optimization procedures for CdTe solar cells at the different stages of fabrication. In this dissertation research, real time SE (RT-SE) has been applied during the fabrication of the as-deposited CdS/CdTe solar cell. Two areas of background research were addressed before undertaking the challenging RT-SE analysis procedures. First, optical functions were parameterized versus temperature for the glass substrate and its overlayers, including three different SnO2 layers. This database has applications not only for RT-SE analysis but also for on-line monitoring of the coated glass itself at elevated temperature. Second, post-deposition modifications of substrate have been studied by infrared spectroscopic ellipsometry (IR-SE) prior to the RT-SE analysis in order to evaluate the need for such modification in the analysis. With support from these background studies, RT-SE has been implemented in analyses of the evolution of the thin film structural properties during sputter deposition of polycrystalline CdS/CdTe solar cells on the transparent conducting oxide (TCO) coated glass substrates. The real time optical spectra collected during CdS/CdTe deposition were analyzed using the optical property database for all substrate components as a function of measurement temperature. RT-SE enables characterization of the filling process of the surface roughness modulations on the top-most SnO2 substrate layer, commonly referred to as the high resistivity transparent (HRT) layer. In this filling process, the optical properties of this surface layer are modified in accordance with an effective medium theory. In addition to providing information on interface formation to the substrate during film growth, RT-SE also provides information on the bulk layer CdS growth, its surface roughness evolution, as well as overlying CdTe interface formation and bulk layer

  13. Luminescence effects of ion-beam bombardment of CdTe surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Olvera, J., E-mail: javier.olvera@uam.e [Laboratorio de Crecimiento de Cristales, Dpto. de Fisica de Materiales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Martinez, O. [Optronlab Group, Dpto. Fisica Materia Condensada, Edificio I-D, Universidad de Valladolid, Paseo de Belen 1, 47011 Valladolid (Spain); Plaza, J.L.; Dieguez, E. [Laboratorio de Crecimiento de Cristales, Dpto. de Fisica de Materiales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2009-09-15

    In the present work, we report the effect of low-energy ion bombardment on CdTe surfaces. The effect is revealed by FESEM images and photoluminescence (PL) measurements carried out before and after irradiation of CdTe polycrystals by means of an ion-beam sputtering (IBS) system. An important improvement in the luminescence of CdTe was observed in the irradiated areas, related to defect-free surfaces.

  14. CdTe-Cu(OH)2 nanocomposite: Aqueous synthesis and characterization

    International Nuclear Information System (INIS)

    Abd El-sadek, M.S.; Moorthy Babu, S.

    2011-01-01

    CdTe-Cu(OH) 2 nanocomposites were synthesized in aqueous solution by a seed-mediated growth approach. The effect of refluxing time and the concentration of Cu 2+ on the preparation of these samples were measured using UV-visible absorption and photoluminescence analysis. The emission peak of the synthesized nanocomposites (CdTe-Cu(OH) 2 ) was shifted from 605 (CdTe seed) to 621 nm. The size of CdTe nanoparticles were averaged about 3.22 nm, and the CdTe-Cu(OH) 2 nanocomposites were averaged as 5.19 nm. The synthesized CdTe-Cu(OH) 2 nanocomposite were characterized with XRD, EDAX, TEM, FT-IR, EPR, and thermal analysis (TG/DTG curves). The results indicate that as-prepared nanoparticles with core/shell structure exhibit interesting optical properties. -- Graphical Abstract: Schematic of aqueous synthesis route for CdTe-Cu(OH) 2 nanocomposite and The Stokes shift of CdTe nanocrystals and CdTe-Cu(OH) 2 Nanocomposites, (CdTe: emission at 605 nm, CdTe-Cu(OH) 2 : emission at 621 nm). Display Omitted Highlights: → CdTe-Cu(OH) 2 nanocomposites were synthesized by a seed-mediated growth approach. → The synthetic procedure is simple, and can be easily scaled up. → The effect of refluxing time on the preparation of these samples was measured. → The Cu(OH) 2 shell thickness was controlled by the amount of Cu in the solution. → TEM images demonstrated homogeneous size distribution for these nanocomposites.

  15. Plasma kinetics and biodistribution of water-soluble CdTe quantum dots in mice: a comparison between Cd and Te

    International Nuclear Information System (INIS)

    Han Ying; Xie Guangyun; Sun Zhiwei; Mu Ying; Han Sihai; Xiao Yang; Liu Na; Wang Hui; Guo Caixia; Shi Zhixiong; Li Yanbo; Huang Peili

    2011-01-01

    Water-soluble quantum dots (QDs) have shown potential as tumor diagnostic agents. However, little is known about their biological behaviors in vivo. Male ICR mice were intravenously given a single dose (2.5 μmol kg −1 body weight) of water-soluble cadmium–telluride (CdTe) QDs (the QDs are approximately 4 nm in diameter and have maximal emission at 630 nm). Inductively coupled plasma mass spectrometry (ICP-MS) was used for measuring the kinetic action of 111 Cd and 125 Te for 7 days. The plasma kinetics of Cd and Te followed a two-compartment model, in which Cd exhibited greater apparent volume of distribution, greater clearance, faster distribution half-life, and significantly slower elimination half-life compared to Te. Contrary to its relatively transient fate in the plasma, high levels of Cd persisted in the liver and kidneys. Te accumulated primarily in the spleen. The different plasma kinetics and distribution patterns of Cd and Te imply that CdTe QDs have been part of the degradation or aggregation in vivo.

  16. Surface-active and electrophysical semiconductors properties of the CdTe-CdSe system

    Science.gov (United States)

    Kirovskaya, I. A.; Bukashkina, T. L.; Ekkert, R. V.; Ushakov, O. V.; Kolesnikov, L. V.; Matyash, Yu I.

    2018-01-01

    Surface properties (acid-base, adsorptive, electrophysical) of binary and multicomponent semiconductors of the CdTe-CdSe system have been holistically studied. Changing patterns of the studied surface properties correlated among themselves and with changing patterns of the bulk physical and chemical properties have been revealed. The nature of active centers, acid-base, adsorptive and electronic interactions mechanisms have been determined with due account for local and collective factors The most active discovered adsorbents are recommended as primary transducers of CO trace impurities measuring cells.

  17. CdTe and CdZnTe room-temperature X-ray and gamma ray detectors and imaging systems

    International Nuclear Information System (INIS)

    Eisen, Y.; Shor, A.

    1998-01-01

    CdTe and CdZnTe X-ray and gamma ray detectors in the form of single elements or as monolithic segmented arrays have been shown to be useful in imaging systems utilized in medical, research or industrial applications. These detectors possess inherently better energy resolution than scintillators coupled to either photodiodes or photomultipliers, and they may lead to compact imaging systems or to imaging systems of enhanced spatial resolution and better contrast resolution. Photopeak efficiencies of these detectors is greatly affected by relatively low hole mobility-lifetime product and therefore continuing efforts are still underway to improve the characteristics of both CdTe and CdZnTe materials in order to achieve reproducible detectors with higher photopeak efficiencies for either low or high energy gamma rays. The paper is divided into three parts. The first part compares the characteristics of planar CdTe and CdZnTe single elements nuclear detectors containing metal contacts. Characteristics include: Charge collection efficiencies for both electrons and holes indicated by the mobility-lifetime product, energy resolutions, leakage currents and robustness in field use. The second part describes excellent spectroscopic results using a 1cm thick CdZnTe monolithic segmented pad detector array. This part also compares spectra for various gamma energies obtained by this segmented detector to that of a 1cm 3 detector acting as a single element planar detector. The third part discusses the characteristics of a new generation nuclear gamma camera for medical diagnostics based on room-temperature CdTe and CdZnTe spectrometers and its advantages over an Anger type scintillating nuclear camera

  18. Preparation and characterization of ZnTe as an interlayer for CdS/CdTe substrate thin film solar cells on flexible substrates

    International Nuclear Information System (INIS)

    Feng, Xianjin; Singh, Kartikay; Bhavanam, Sushma; Palekis, Vasilios; Morel, Don L.; Ferekides, Chris

    2013-01-01

    ZnTe thin films have been prepared on Mo-coated stainless steel substrates by the close spaced sublimation (CSS) technique. Cu-doped ZnTe (ZnTe:Cu) films are prepared by immersing the as-deposited samples in a CuCl–H 2 O solution. The structural and morphological properties of the ZnTe films as a function of substrate temperature are investigated using X-ray diffraction and scanning electron microscopy. CdS/CdTe solar cells with and without the ZnTe and ZnTe:Cu interlayers are prepared and characterized with current–voltage (J–V), spectral response, and capacitance–voltage measurements. The structural and morphological properties of the ZnTe films prepared by CSS are found to be strongly influenced by the substrate temperature. The ‘roll-over’ behavior in the J–V characteristics of the CdS/CdTe solar cells due to a Schottky barrier at the back contact can be eliminated using ZnTe as the interlayer. Preliminary results on the application of ZnTe:Cu films suggest that the open circuit voltage and fill factor can be further improved, depending on processing conditions. - Highlights: ► Thin film CdTe solar cells on flexible stainless steel substrates are prepared. ► Using ZnTe can eliminate the ‘roll-over’ behavior in the current–voltage curve. ► Incorporating Cu can further improve the open circuit voltage and fill factor

  19. Advanced CdTe Photovoltaic Technology: September 2007 - March 2009

    Energy Technology Data Exchange (ETDEWEB)

    Barth, K.

    2011-05-01

    During the last eighteen months, Abound Solar (formerly AVA Solar) has enjoyed significant success under the SAI program. During this time, a fully automated manufacturing line has been developed, fabricated and commissioned in Longmont, Colorado. The facility is fully integrated, converting glass and semiconductor materials into complete modules beneath its roof. At capacity, a glass panel will enter the factory every 10 seconds and emerge as a completed module two hours later. This facility is currently undergoing trials in preparation for large volume production of 120 x 60 cm thin film CdTe modules. Preceding the development of the large volume manufacturing capability, Abound Solar demonstrated long duration processing with excellent materials utilization for the manufacture of high efficiency 42 cm square modules. Abound Solar prototype modules have been measured with over 9% aperture area efficiency by NREL. Abound Solar demonstrated the ability to produce modules at industry leading low costs to NREL representatives. Costing models show manufacturing costs below $1/Watt and capital equipment costs below $1.50 per watt of annual manufacturing capacity. Under this SAI program, Abound Solar supported a significant research and development program at Colorado State University. The CSU team continues to make progress on device and materials analysis. Modeling for increased device performance and the effects of processing conditions on properties of CdTe PV were investigated.

  20. Patterning thick diffused junctions on CdTe

    CERN Document Server

    Kalliopuska, Juha; Sipilä, Heikki; Andersson, Hans; Vähänen, Sami; Eränen, Simo; Tlustos, Lukas

    2009-01-01

    Dividing the detector crystal into discrete pixels enables making an imaging detector, in which the charge collected by each pixel can be read separately. Even if the detector is not meant for imaging, patterns on the crystal surface may be used as guard structures that control and limit the flow of charges in the crystal. This has been exceedingly hard for the detector crystals having thick diffused layers. The paper reports a patterning method of the thick diffused junctions on CdTe. The patterning method of In-diffused pn-junction on CdTe chip is demonstrated by using a diamond blade. The patterning is done by removing material from the pn-junction side of the chip, so that the trenches penetrate the diffused layer. As the trenches extend deeper into the bulk than the junction, the regions separated by the trench are electrically isolated. Electrical characterization results are reported for the strips separated by trenches with various depths. The strip isolation is clearly seen in both measured leakage c...

  1. Neutron scattering studies of Cd1−xMnxTe

    DEFF Research Database (Denmark)

    Giebultowicz, T.; Lebech, Bente; Buras, B

    1984-01-01

    The diluted magnetic (‘‘semimagnetic’’) semiconductor Cd1–xMnxTe reveals intriguing spin glass properties. In this paper, the results of neutron scattering studies of Cd1–xMnxTe are presented. The low‐temperature spin correlations have been studied for several single crystal samples in the compos......The diluted magnetic (‘‘semimagnetic’’) semiconductor Cd1–xMnxTe reveals intriguing spin glass properties. In this paper, the results of neutron scattering studies of Cd1–xMnxTe are presented. The low‐temperature spin correlations have been studied for several single crystal samples...

  2. Highly fluorescent CdTe quantum dots with reduced cytotoxicity-A Robust biomarker

    Directory of Open Access Journals (Sweden)

    Jandi Kim

    2015-03-01

    Full Text Available l-Cysteine (Cys capped CdTe quantum dots (CdTe@Cys QDs were successfully synthesized in an aqueous medium. The synthesized CdTe@Cys samples were analyzed using Fourier transform infrared (FT-IR spectroscopy, fluorescence (FL spectroscopy, transmission electron microscopy (TEM, confocal microscopy and subsequently subjected to the antibacterial test. Systematic investigations were carried out for the determination of optimal conditions namely the ratios of Cd:Te, CdTe:Cys, pH value and the chemical stability of CdTe@Cys. Moreover, the reactivation of FL intensity in the CdTe@Cys sample was done easily by the addendum of Cys. The introduction of additional cysteine to the CdTe@Cys QDs sample showed an enhancement in terms of the FL intensity and stability along with the reduced antibacterial activity. This was further confirmed through Thiazolyl blue tetrazolium bromide (MTT assays. Both the result of the bio-stability tests namely the antibacterial test and MTT assay displayed similarities between the externally added Cys and cytotoxicity of the bacteria and human HeLa cancer cell lines. Confocal microscopic images were captured for the CdTe@Cys conjugated Escherichia coli.

  3. Effect of Heating, Ion-Beam Milling, and ZnTe:Cu Deposition on the Spectroscopic Cathodoluminescence of Polycrystalline CdTe: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Gessert, T. A.; Romero, M. J.; Asher, S. E.

    2001-10-01

    Presented at the 2001 NCPV Program Review Meeting: Cathodoluminescence used to study evolution of electro-optical properties of back surface of CdS/CdTe during initial steps of fabricating NREL ZnTe:Cu contact.

  4. Large-Scale Surfactant-Free Synthesis of p-Type SnTe Nanoparticles for Thermoelectric Applications

    Directory of Open Access Journals (Sweden)

    Guang Han

    2017-02-01

    Full Text Available A facile one-pot aqueous solution method has been developed for the fast and straightforward synthesis of SnTe nanoparticles in more than ten gram quantities per batch. The synthesis involves boiling an alkaline Na2SnO2 solution and a NaHTe solution for short time scales, in which the NaOH concentration and reaction duration play vital roles in controlling the phase purity and particle size, respectively. Spark plasma sintering of the SnTe nanoparticles produces nanostructured compacts that have a comparable thermoelectric performance to bulk counterparts synthesised by more time- and energy-intensive methods. This approach, combining an energy-efficient, surfactant-free solution synthesis with spark plasma sintering, provides a simple, rapid, and inexpensive route to p-type SnTe nanostructured materials.

  5. Solution-Processed Efficient Nanocrystal Solar Cells Based on CdTe and CdS Nanocrystals

    Directory of Open Access Journals (Sweden)

    Songwei Liu

    2018-01-01

    Full Text Available Solution-processed CdTe nanocrystals solar cells have attracted much attention due to their low cost, low material consumption, and potential for roll-to-roll production. Among all kinds of semiconductor materials, CdS exhibits the lowest lattice mismatch with CdTe, which permits high junction quality and high device performance. In this study, high quality CdS nanocrystals were prepared by a non-injection technique with tetraethylthiuram disufide and 2,2′-dithiobisbenzothiazole as the stabilizers. Based on the CdTe and CdS nanocrystals, devices with the architecture of ITO/ZnO/CdS/CdTe/MoOx/Au were fabricated successfully by a solution process under ambient condition. The effects of annealing conditions, film thickness, and detailed device structure on the CdTe/CdS nanocrystal solar cells were investigated and discussed in detail. We demonstrate that high junction quality can be obtained by using CdS nanocrystal thin film compared to traditional CdS film via chemical bath deposition (CBD. The best device had short circuit current density (Jsc, open circuit voltage (Voc and fill factor (FF of 17.26 mA/cm2, 0.56 V, and 52.84%, respectively, resulting in a power conversion efficiency (PCE of 5.14%, which is significantly higher than that reported using CBD CdS as the window layer. This work provides important suggestions for the further improvement of efficiency in CdTe nanocrystal solar cells.

  6. Defects subsystem and homogeneity region of ZnTe and CdTe crystals

    Science.gov (United States)

    Horichok, Ihor; Parashchuk, Taras; Pylyponiuk, Mariia; Soroka, Oksana; Voloshynovych, Marian

    2018-03-01

    Based on the comparison of theoretical calculations of the point defects formation energy by ab initio method and their concentration by the thermodynamic potentials method with the experimental data of the Hall effect study and the homogeneity region width of zinc and cadmium tellurides, it was shown that in the ZnTe crystals, as in the CdTe crystals, at the chalcogen saturation the dominant defects are cationic vacancies and antistructural chalcogen atoms, whose point symmetry corresponds to the Td group. When both zinc and cadmium tellurides are saturated with the metal, the most probable type of the dominant point defects is the electroneutral chalcogen vacancy, the formation of which is accompanied by the significant relaxation of the nearest atoms and loss of initial symmetry.

  7. Measuring Te inclusion uniformity over large areas for CdTe/CZT imaging and spectrometry sensors

    Science.gov (United States)

    Bolke, Joe; O'Brien, Kathryn; Wall, Peter; Spicer, Mike; Gélinas, Guillaume; Beaudry, Jean-Nicolas; Alexander, W. Brock

    2017-09-01

    CdTe and CZT materials are technologies for gamma and x-ray imaging for applications in industry, homeland security, defense, space, medical, and astrophysics. There remain challenges in uniformity over large detector areas (50 75 mm) due to a combination of material purity, handling, growth process, grown in defects, doping/compensation, and metal contacts/surface states. The influence of these various factors has yet to be explored at the large substrate level required for devices with higher resolution both spatially and spectroscopically. In this study, we looked at how the crystal growth processes affect the size and density distributions of microscopic Te inclusion defects. We were able to grow single crystals as large as 75 mm in diameter and spatially characterize three-dimensional defects and map the uniformity using IR microscopy. We report on the pattern of observed defects within wafers and its relation to instabilities at the crystal growth interface.

  8. Magnetospectroscopy of double HgTe/CdHgTe quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Bovkun, L. S.; Krishtopenko, S. S.; Ikonnikov, A. V., E-mail: antikon@ipmras.ru; Aleshkin, V. Ya.; Kadykov, A. M. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Ruffenach, S.; Consejo, C.; Teppe, F.; Knap, W. [Laboratoire Charles Coulomb (L2C), UMR CNRS 5221 and UM (France); Orlita, M.; Piot, B.; Potemski, M. [Laboratoire National des Champs Magnetiques Intenses (LNCMI-G), CNRS-UJF-UPS-INSA (France); Mikhailov, N. N.; Dvoretskii, S. A. [Russian Academy of Sciences, Siberian Branch, Rzhanov Institute of Semiconductor Physics (Russian Federation); Gavrilenko, V. I. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

    2016-11-15

    The magnetoabsorption spectra in double HgTe/CdHgTe quantum wells (QWs) with normal and inverted band structures are investigated. The Landau levels in symmetric QWs with a rectangular potential profile are calculated based on the Kane 8 × 8 model. The presence of a tunnel-transparent barrier is shown to lead to the splitting of states and “doubling” of the main magnetoabsorption lines. At a QW width close to the critical one the presence of band inversion and the emergence of a gapless band structure, similar to bilayer graphene, are shown for a structure with a single QW. The shift of magnetoabsorption lines as the carrier concentration changes due to the persistent photoconductivity effect associated with a change in the potential profile because of trap charge exchange is detected. This opens up the possibility for controlling topological phase transitions in such structures.

  9. Carrier Lifetimes of Iodine-Doped CdMgTe/CdSeTe Double Heterostructures Grown by Molecular Beam Epitaxy

    Science.gov (United States)

    Sohal, S.; Edirisooriya, M.; Ogedengbe, O. S.; Petersen, J. E.; Swartz, C. H.; LeBlanc, E. G.; Myers, T. H.; Li, J. V.; Holtz, M.

    2017-09-01

    Iodine-doped CdMgTe/CdSeTe double heterostructures (DHs) have been grown by molecular beam epitaxy and studied using time-resolved photoluminescence (PL), focusing on absorber layer thickness of 2 μm. The n-type free carrier concentration was varied to ˜7 × 1015 cm-3, 8.4 × 1016 cm-3, and 8.4 × 1017 cm-3 using iodine as dopant in DHs. Optical injection at 1 × 1010 photons/pulse/cm2 to 3 × 1011 photons/pulse/cm2, corresponding to initial injection of photocarriers up to ˜8 × 1015 cm-3, was applied to examine the effects of excess carrier concentration on the PL lifetimes. Iodine-doped DHs exhibited an initial rapid decay followed by a slower decay at free carrier concentration of 7 × 1015 cm-3 and 8.4 × 1016 cm-3. The optical injection dependence of the carrier lifetimes for DHs was interpreted based on the Shockley-Read-Hall model. The observed decrease in lifetime with increasing n is consistent with growing importance of radiative recombination.

  10. Photovoltaic efficiency of intermediate band solar cells based on CdTe/CdMnTe coupled quantum dots

    Science.gov (United States)

    Prado, Silvio J.; Marques, Gilmar E.; Alcalde, Augusto M.

    2017-11-01

    In this work we show the calculation of optimized efficiencies of intermediate band solar cells (IBSCs) based on Mn-doped II-VI CdTe/CdMnTe coupled quantum dot (QD) structures. We focus our attention on the combined effects of geometrical and Mn-doping parameters on optical properties and solar cell efficiency. In the framework of {k \\cdot p} theory, we accomplish detailed calculations of electronic structure, transition energies, optical selection rules and their corresponding intra- and interband oscillator strengths. With these results and by following the intermediate band model, we have developed a strategy which allows us to find optimal photovoltaic efficiency values. We also show that the effects of band admixture which can lead to degradation of optical transitions and reduction of efficiency can be partly minimized by a careful selection of the structural parameters and Mn-concentration. Thus, the improvement of band engineering is mandatory for any practical implementation of QD systems as IBSC hardware. Finally, our calculations show that it is possible to reach significant efficiency, up to  ∼26%, by selecting a restricted space of parameters such as quantum dot size and shape and Mn-concentration effects, to improve the modulation of optical absorption in the structures.

  11. Long-Term Stable Surface Treatments on CdTe and CdZnTe Radiation Detectors

    Science.gov (United States)

    Pekarek, Jakub; Belas, Eduard; Zazvorka, Jakub

    2017-04-01

    The spectral resolution and charge collection efficiency (CCE) of cadmium telluride (CdTe) and cadmium zinc telluride (CZT) room-temperature x-ray and gamma-ray detectors are often limited by high surface leakage current due to conducting surface species created during detector fabrication. Surface treatments play a major role in reduction of this surface leakage current. The effect of various types of surface etching and passivation on the leakage current and thereby the spectral energy resolution, CCE, and internal electric field profile of CdTe/CZT detectors has been studied. The main aim of this work is preparation of long-term stable detectors with strongly reduced leakage current. The time stability of the current-voltage characteristic and spectral resolution was investigated during 21 days and 1 year, respectively, after performing surface treatments. Our results suggest that the optimal detector preparation method is chemomechanical polishing in bromine-ethylene glycol solution followed by chemical etching in bromine-methanol solution then surface passivation in potassium hydroxide or ammonium fluoride (NH4F/H2O2). Detectors prepared using this optimal treatment exhibited low leakage current, high spectral resolution, and long-term stability compared with those subjected to other surface preparation methods.

  12. Dielectric properties and soft modes in semiconducting (Pb, Sn, Ge)Te

    Science.gov (United States)

    Jantsch, W.

    The narrow-gap semiconductors PbTe, SnTe, GeTe and their alloys exhibit a tendency for a ferroelectric displacive phase transition from a high-temperature rocksalt structure to a rhombohedral phase at low temperatures. The critical temperatures vary within an exceedingly wide range: -70 K(PbTe) up to 650 K(GeTe). Owing to the outstanding simplicity of their crystal structure and their well-known electronic properties, the instability and the chemical trends of Tc can be understood in terms of a quantitative pseudopotential model (Sect.5.2). Phenomenological models explain the temperature dependence of the soft mode outside the critical regime fairly well (Sect.5.1). Critical phenomena, however, deserve further attention: the anomalies of the static dielectric constant (Sects.3.1 and 5.3) and the influence of defects are possibly related to a central peak. Additional systematic investigations on the nature and influence of defects are required to obtain more insight into this highly interesting field of general importance.

  13. Stark Broadening of Se IV, Sn IV, Sb IV and Te IV Spectral Lines

    Directory of Open Access Journals (Sweden)

    Milan S. Dimitrijević

    2018-03-01

    Full Text Available Stark broadening parameters, line width and shift, are needed for investigations, analysis and modelling of astrophysical, laboratory, laser produced and technological plasmas. Especially in astrophysics, due to constantly increasing resolution of satellite borne spectrographs, and large terrestrial telescopes, data on trace elements, which were previously insignificant, now have increasing importance. Using the modified semiempirical method of Dimitrijević and Konjević, here, Stark widths have been calculated for 2 Se IV, 6 Sn IV, 2 Sb IV and 1 Te IV transitions. Results have been compared with existing theoretical data for Sn IV. Obtained results will be implemented in the STARK-B database, which is also a part of Virtual atomic and molecular data center (VAMDC.

  14. Spectrum-per-Pixel Cathodoluminescence Imaging of CdTe Thin-Film Bevels

    Energy Technology Data Exchange (ETDEWEB)

    Moseley, John; Al-Jassim, Mowafak M.; Burst, James; Guthrey, Harvey L.; Metzger, Wyatt K.

    2016-11-21

    We conduct T=6 K cathodoluminescence (CL) spectrum imaging with a nano-scale electron beam on beveled surfaces of CdTe thin-films at different critical stages of standard CdTe device fabrication. The through-thickness total CL intensity profiles are consistent with a reduction in grain boundary recombination due to the CdCl2 treatment. Color-coded maps of the low-temperature luminescence transition energies reveal that CdTe thin films have remarkably non-uniform opto-electronic properties, which depend strongly on sample processing history. The grain-to-grain S content in the interdiffused CdTe/CdS region is estimated from a sample size of thirty-five grains, and the S content in adjacent grains varies significantly in CdCl2-treated samples. A low-temperature luminescence model is developed to interpret spectral behavior at grain boundaries and grain interiors.

  15. Spectroscopic study on the doping of polycrystalline CdTe layers for solar cells; Spektroskopische Untersuchungen zur Dotierung von polykristallinen CdTe-Schichten fuer Solarzellen

    Energy Technology Data Exchange (ETDEWEB)

    Kraft, Christian

    2011-11-29

    First in the present thesis the fundamental properties of CdTe are described. In the following it is discussed, how a CdTe solar cell is generally constructed, which specialities are to be regarded, and how an improvement of the actually reachable data of such a solar cell in view of the efficiency can be reached fundamentally and in then practical realization. In the third chapter the physical foundations of the most important methods are discussed, which are applied in the framework of this thesis for the analysis of the CdTe layers. The fourth chapter describes the details of the experiments of this thesis. The fifth chapter deals with the analysis of the photoluminescence of CdTe layers. Special attention is put on the analysis of the excitonic luminescence. The sixth chapter treats the implantation of CdTe layers with phosphor. The influence of phosphorus as dopant on the PL spectra of CdTe and the correponding characteristics of implanted solar cells are presented. Also the influence of radiation damages as consequence of the ion implantation is studied in this chapter by means of the analysis of differently thick absorber layers. In the seventh chapter finally a new procedure for the fabrication of solar cells on the base of CdTe as absorber material is introduced, which shall make possible to change the stoichiometry of cadmium mand tellurium specifically and to present additionally a suited material, in order to form the doping of CdTE a solar-cell material variably. The fundamental properties of the new facility are experimentally determined, and first solar cells are fabricated with this facility and analyzed. Also an in-situ doping with phosphorus is thereby performed and the result studied.

  16. Study of CdTe:Cl and CdZnTe detectors for medical multi-slices X-ray Computed Tomography

    International Nuclear Information System (INIS)

    Ricq, St.

    1999-01-01

    The application of CdTe and CdZnTe detectors to medical X-ray Computed Tomography have been investigated. Different electrodes (Au, Pt, In) have been deposited on CdZnTe HPBM and on CdTe:ClTHM. Their injection properties have been determined with Current-Voltage characteristics. Under X-ray in CT conditions, injection currents measurements reveal trapped carriers space-charges formation. The same way, the comparisons of the responses to X-beam cut-off with various injection possibilities enable to follow the space-charges evolutions and then to determine the predominant traps types. Nevertheless, both hole and electron traps are responsible for the memory effect e.g. the currents levels dependence with irradiation history. This effect is noticed in particular on responses to fast flux variations that simulate scanner's conditions. Trap levels probably corresponding to native defects are responsible for these limitations. In order to make such detectors suitable for X-ray Computed Tomography, significant progresses in CdTe for CdZnTe crystal growth with an important defects densities reduction (factor 10), or possibly counting mode operation, seem necessary. (author)

  17. Electrical and photovoltaic properties of CdTe/ZnTe n-i-p junctions grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Zielony, E., E-mail: eunika.zielony@pwr.edu.pl; Płaczek-Popko, E.; Racino, A.; Gumienny, Z. [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Olender, K.; Wosiński, T.; Karczewski, G.; Chusnutdinow, S. [Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, 02-668 Warsaw (Poland)

    2014-06-28

    Preliminary studies have been performed on photoelectrical properties of CdTe/ZnTe n-i-p junctions grown using the molecular beam epitaxy technique. Photovoltaic properties of the cells have been investigated by the measurements of current-voltage (I-V) characteristics under 1-sun illumination. I-V characteristics yield efficiencies of the cells varying from 3.4% to 4.9%. The low efficiency can be due to the presence of electrically active defects. In order to study the origin of defects in CdTe/ZnTe photovoltaic junctions, space charge techniques (C-V and deep level transient spectroscopy (DLTS)) have been applied. From the C-V measurements, a doping profile was calculated confirming charge accumulation in the i-CdTe layer. The results of the DLTS studies revealed the presence of four traps within a temperature range from 77–420 K. Three of them with activation energies equal to 0.22 eV, 0.45 eV, and 0.78 eV have been ascribed to the hole traps present in the i-CdTe material and their possible origin has been discussed. The fourth, high-temperature DLTS peak observed at ∼350 K has been attributed to extended defects as its amplitude and temperature position depends on the value of the filling pulse width. It is assumed that the defects related to the trap are either located in the i-CdTe layer or at the i-CdTe/ZnTe interface. However, it was found that the trap exhibits twofold nature: it behaves as a majority or as a minority trap, depending on the filling pulse height, which is a characteristic feature of recombination centers. This trap is presumably responsible for the low efficiency of the cells.

  18. Thin Film CdZnTe Detector Arrays for Digital Mammography

    National Research Council Canada - National Science Library

    Sudharsanan, Rengarajan

    1999-01-01

    ...) directly on thin-film transistor (TFT) active matrix arrays for image readout. CdTe and CdZnTe have the potential to meet the requirements for digital mammography due to their high x-ray absorption, large band gap and good carrier transport...

  19. Thin Film CdZnTe Detector Arrays for Digital Mammography

    National Research Council Canada - National Science Library

    Kalkhoran, Nader

    2001-01-01

    ...) directly on thin-film transistor (TFT) active matrix arrays for image readout. CdTe and CdZnTe have the potential to meet the requirements for digital mammography due to their high x-ray absorption, large bandgap and good carrier transport...

  20. Narrowing the size distribution of CdTe nanocrystals using digestive ...

    Indian Academy of Sciences (India)

    2015-06-02

    Jun 2, 2015 ... 2.2 Synthesis of CdTe NCs. CdTe NCs were ... Asymmetric. 2.4 Effect of refluxing time on digestive ripening. To get the control on NCs size and size distribution, digestive ripening is performed using the ... 2 h, distribution of luminescence spectrum become asymmetrical and FWHM increases which limits ...

  1. Dead regions and electric thickness in the CdTe(Cl) radiation detector

    International Nuclear Information System (INIS)

    Hirasawa, Masahiko

    2001-01-01

    The studies suggested that low resistivity (approximately 10 -1 Ω cm) granular regions were distributed in high resistivity (approximately 10 9 Ω cm) CdTe(Cl). The existence and influence of these low resistivity regions in the radiation detector made of high resistivity CdTe(Cl) are examined by experiments, numerical simulations and analytical calculations in the present paper. (author)

  2. Performance updating of CdZnTe strip-drift detectors

    DEFF Research Database (Denmark)

    Shorohov, M.; Tsirkunova, I.; Loupilov, A.

    2007-01-01

    59.6 and 662 keV correspondingly. Recently, significant progress was done in CdZnTe crystals growth technology. In the present paper we present preliminary result of performance updating of CdZnTe strip-drift detectors based on crystal of 10 x 10 x 6 mm 3 produced by Yinnel Tech company. Results...

  3. Growth and characterization of Hg 1– Cd Te epitaxial films by ...

    Indian Academy of Sciences (India)

    Growth of Hg1–CdTe epitaxial films by a new technique called asymmetric vapour phase epitaxy (ASVPE) has been carried out on CdTe and CZT substrates. The critical problems faced in normal vapour phase epitaxy technique like poor surface morphology, composition gradient and dislocation multiplication have ...

  4. The influence of series resistance on the I-V characteristics of CdTe ...

    African Journals Online (AJOL)

    The influence of series resistance (Rs) on the current (I) – voltage(V) characteristics of evaporated cadmium telluride(CdTe) thin films has been investigated. CdTe films of thickness 1000Å were deposited by thermal evaporation in a vacuum of about 10-5torr. For the I – V measurements, the two point probe configuration ...

  5. Evolution of oxygenated cadmium sulfide (CdS:O) during high-temperature CdTe solar cell fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Meysing, Daniel M.; Reese, Matthew O.; Warren, Charles W.; Abbas, Ali; Burst, James M.; Mahabaduge, Hasitha P.; Metzger, Wyatt K.; Walls, John M.; Lonergan, Mark C.; Barnes, Teresa M.; Wolden, Colin A.

    2016-12-01

    Oxygenated cadmium sulfide (CdS:O) produced by reactive sputtering has emerged as a promising alternative to conventional CdS for use as the n-type window layer in CdTe solar cells. Here, complementary techniques are used to expose the window layer (CdS or CdS:O) in completed superstrate devices and combined with a suite of materials characterization to elucidate its evolution during high temperature device processing. During device fabrication amorphous CdS:O undergoes significant interdiffusion with CdTe and recrystallization, forming CdS1-yTey nanocrystals whose Te fraction approaches solubility limits. Significant oxygen remains after processing, concentrated in sulfate clusters dispersed among the CdS1-yTey alloy phase, accounting for ~30% of the post-processed window layer based on cross-sectional microscopy. Interdiffusion and recrystallization are observed in devices with un-oxygenated CdS, but to a much lesser extent. Etching experiments suggest that the CdS thickness is minimally changed during processing, but the CdS:O window layer is reduced from 100 nm to 60-80 nm, which is confirmed by microscopy. Alloying reduces the band gap of the CdS:O window layer to 2.15 eV, but reductions in thickness and areal density improve its transmission spectrum, which is well matched to device quantum efficiency. The changes to the window layer in the reactive environments of device fabrication are profoundly different than what occurs by thermal annealing in an inert environment, which produced films with a band gap of 2.4 eV for both CdS and CdS:O. These results illustrate for the first time the significant changes that occur to the window layer during processing that are critical to the performance of CdTe solar cells.

  6. The CdTe detector module and its imaging performance.

    Science.gov (United States)

    Mori, I; Takayama, T; Motomura, N

    2001-12-01

    In recent years investigations into the application of semiconductor detector technology in gamma cameras have become active world-wide. The reason for this burst of activity is the expectation that the semiconductor-based gamma camera would outperform the conventional Anger-type gamma camera with a large scintillator and photomultipliers. Nevertheless, to date, it cannot be said that this expectation has been met. While most of the studies have used CZT (Cadmium Zinc Telluride) as the semiconductor material, we designed and fabricated an experimental detector module of CdTe (Cadmium Telluride). The module consists of 512 elements and its pixel pitch is 1.6 mm. We have evaluated its energy resolution, planar image performance, single photon emission computed tomography (SPECT) image performance and time resolution for coincidence detection. The average energy resolution was 5.5% FWHM at 140 keV. The intrinsic spatial resolution was 1.6 mm. The quality of the phantom images, both planar and SPECT, was visually superior to that of the Anger-type gamma camera. The quantitative assessment of SPECT images showed accuracy far better than that of the Anger-type camera. The coincidence time resolution was 8.6 ns. All measurements were done at room temperature, and the polarization effect that had been the biggest concern for CdTe was not significant. The results indicated that the semiconductor-based gamma camera is superior in performance to the Anger-type and has the possibility of being used as a positron emission computed tomography (PET) scanner.

  7. Tunable band offset and recombination in ZnO nanowire-CdTe quantum dot heterostructures

    Science.gov (United States)

    He, Haiping; Gan, Lu; Sun, Luwei; Ye, Zhizhen

    2017-10-01

    ZnO nanowire (NW)-CdTe quantum dot (QD) type-II heterostructures were constructed using hydrothermally grown ZnO and colloidal CdTe QDs. Photoluminescence (PL) spectroscopy was used to investigate the charge transfer and band offset between CdTe QDs and ZnO NWs. The results demonstrated that the PL shows obvious redshift and prolonged lifetime in the heterostructure, indicating that it originates from recombination between electrons localized in ZnO and holes localized in CdTe. The results reveal that the band offset and charge recombination can be tuned by the growth time or size of CdTe QDs. Our results demonstrate that PL can be a useful tool to evaluate the band alignment and charge recombination in type-II semiconductor heterostructures.

  8. Evaluation of a miniature CdTe detector for monitoring left ventricular function.

    Science.gov (United States)

    Harrison, K S; Liu, X; Han, S T; Camargo, E E; Wagner, H N

    1982-01-01

    A miniature CdTe probe interfaced to a microcomputer was used to measure left ventricular ejection fraction (LVEF) in 25 patients. LVEF obtained with the CdTe module, in the beat-to-beat mode, or the integrated gated mode agreed well with LVEF obtained with a gamma camera (r = 0.80; r = 0.82 respectively). Similarly, LVEF by CdTe probe agreed with LVEF obtained by gated equilibrium studies performed with a computerized NaI probe. The CdTe probe can provide comparable measurement of LVEF at a fraction of the cost of a camera-computer system and, being small and lightweight, the CdTe probe is adaptable for monitoring patients in intensive care facilities.

  9. Applications of CdTe to nuclear medicine. Annual report, February 1, 1978-January 31, 1979

    International Nuclear Information System (INIS)

    Entine, G.

    1979-01-01

    The use of CdTe radiation detectors in medical applications continues to become more widespread. During this contract period a CdTe detector as small as 1 mm 3 was inserted into a bronchoscope while a CdTe array as large as 4200 mm 3 was used as a prototype gamma camera. Portable battery powered instrumentation was also developed to further enhance the versatility of the CdTe concept. One of these electronic packages which is used in several hospitals is illustrated. The unit provides an LED digital readout and timing circuits to vary the measuring time between 1 and 500 seconds. The total weight is below 0.6 g. The units have been used with several specialized CdTe probes including a plutonium wound probe, a nuclear dentistry probe, an implantible heart probe and an I-125 Fibrinigen sensor. These special probes are also illustrated

  10. HgCdTe infrared detector material: history, status and outlook

    Science.gov (United States)

    Rogalski, A.

    2005-10-01

    This article reviews the history, the present status and possible future developments of HgCdTe ternary alloy for infrared (IR) detector applications. HgCdTe IR detectors have been intensively developed since the first synthesis of this material in 1958. This article summarizes the fundamental properties of this versatile narrow gap semiconductor, and relates the material properties to its successful applications as an IR photoconductive and photovoltaic detector material. An emphasis is put on key developments in the crystal growth and their influence on device evolution. Competitive technologies to HgCdTe ternary alloy are also presented. Recent advances of backside illuminated HgCdTe heterojunction photodiodes have enabled a third generation of multispectral instruments for remote sensing applications and have led to the practicality of multiband IR focal plane array technology. Finally, evaluation of HgCdTe for room temperature long wavelength IR applications is presented.

  11. Design Strategies for High-Efficiency CdTe Solar Cells

    Science.gov (United States)

    Song, Tao

    With continuous technology advances over the past years, CdTe solar cells have surged to be a leading contributor in thin-film photovoltaic (PV) field. While empirical material and device optimization has led to considerable progress, further device optimization requires accurate device models that are able to provide an in-depth understanding of CdTe device physics. Consequently, this thesis is intended to develop a comprehensive model system for high-efficiency CdTe devices through applying basic design principles of solar cells with numerical modeling and comparing results with experimental CdTe devices. The CdTe absorber is central to cell performance. Numerical simulation has shown the feasibility of high energy-conversion efficiency, which requires both high carrier density and long minority carrier lifetime. As the minority carrier lifetime increases, the carrier recombination at the back surface becomes a limitation for cell performance with absorber thickness concentration. (Abstract shortened by ProQuest.).

  12. The Protocol Of KFM Characterization On Cross-section Of CdS/CdTe Thin Film Solar Cell

    International Nuclear Information System (INIS)

    You, L.; Chevalier, N.; Bernardi, S.; Martinez, E.; Mariolle, D.; Feuillet, G.; Chabli, A.; Bertin, F.; Kogelschatz, M.; Bremond, G.

    2011-01-01

    In this work, we report a series of Kelvin Force Microscopy (KFM) measurements, suitable to observe the topography and the contact potential difference (CPD) distribution of the following stack: CdTe/CdS/ITO/glass. The sample is prepared by mechanical polishing after cleavage to decrease the roughness. In order to have a better understanding of the charge transport inside the solar cell and to vary the Fermi level pinning effect, different bias are applied to the sample. The CPD variations with different bias on cross-section in dark condition are presented. We observe the reverse bias widens the CdTe/CdS depletion region. Under illumination, electron and holes are generated near the interface and varies the CPD distribution. Additionally, the chemical composition of each layer has been investigated by nano-Auger electron spectroscopy (AES). We observe the interdiffusion at the CdTe/CdS interface and determine the composition of the active layers to be CdTe/CdS 0.7 Te 0.3 .

  13. Real-time observation of nanoscale topological transitions in epitaxial PbTe/CdTe heterostructures

    Directory of Open Access Journals (Sweden)

    H. Groiss

    2014-01-01

    Full Text Available The almost completely immiscible PbTe/CdTe heterostructure has recently become a prototype system for self-organized quantum dot formation based on solid-state phase separation. Here, we study by real-time transmission electron microscopy the topological transformations of two-dimensional PbTe-epilayers into, first, a quasi-one-dimensional percolation network and subsequently into zero-dimensional quantum dots. Finally, the dot size distribution coarsens by Ostwald ripening. The whole transformation sequence occurs during all stages in the fully coherent solid state by bulk diffusion. A model based on the numerical solution of the Cahn-Hilliard equation reproduces all relevant morphological and dynamic aspects of the experiments, demonstrating that this standard continuum approach applies to coherent solids down to nanometer dimensions. As the Cahn-Hilliard equation does not depend on atomistic details, the observed morphological transformations are general features of the model. To confirm the topological nature of the observed shape transitions, we developed a parameter-free geometric model. This, together with the Cahn-Hilliard approach, is in qualitative agreement with the experiments.

  14. Cadmium flows and emissions from CdTe PV: future expectations

    International Nuclear Information System (INIS)

    Cadmium telluride photovoltaic (CdTe PV) technology is growing rapidly, and already represents the largest contributor to non-silicon based photovoltaics worldwide. We assessed the extent to which CdTe PV will play a notable role in the Cd use and emission flows in the future, and whether it will be environmentally beneficial or detrimental. Our results show that while CdTe PV may account for a large percentage of future global Cd demand, its role in terms of Cd sequestration may be beneficial. We calculated that its potential contribution to yearly global Cd emissions to air and water may well be orders-of-magnitude lower than the respective current Cd emissions rates in Europe.

  15. An ultrasensitive electrochemical biosensor for glucose using CdTe-CdS core-shell quantum dot as ultrafast electron transfer relay between graphene-gold nanocomposite and gold nanoparticle

    Energy Technology Data Exchange (ETDEWEB)

    Gu Zhiguo; Yang Shuping [School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122 (China); Li Zaijun, E-mail: zaijunli@263.net [School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122 (China); Sun Xiulan [School of Food Science and Technology, Jiangnan University, Wuxi 214122 (China); Wang Guangli [School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122 (China); Fang Yinjun [Zhejiang Zanyu Technology Co., Ltd., Hangzhou 310009 (China); Liu Junkang [School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122 (China)

    2011-10-30

    Graphical abstract: We first reported an ultrasensitive electrochemical biosensor for glucose using CdTe-CdS core-shell quantum dot as ultrafast electron transfer relay between graphene-gold nanocomposite and gold nanoparticle. Since promising their electrocatalytic synergy towards glucose was achieved, the biosensor showed high sensitivity (5762.8 nA nM{sup -1} cm{sup -2}), low detection limit (S/N = 3) (3 x 10{sup -12} M) and fast response time (0.045 s). - Abstract: The paper reported an ultrasensitive electrochemical biosensor for glucose which was based on CdTe-CdS core-shell quantum dot as ultrafast electron transfer relay between graphene-gold nanocomposite and gold nanoparticle. Since efficient electron transfer between glucose oxidase and the electrode was achieved, the biosensor showed high sensitivity (5762.8 nA nM{sup -1} cm{sup -2}), low detection limit (S/N = 3) (3 x 10{sup -12} M), fast response time (0.045 s), wide calibration range (from 1 x 10{sup -11} M to 1 x 10{sup -8} M) and good long-term stability (26 weeks). The apparent Michaelis-Menten constant of the glucose oxidase on the medium, 5.24 x 10{sup -6} mM, indicates excellent bioelectrocatalytic activity of the immobilized enzyme towards glucose oxidation. Moreover, the effects of omitting graphene-gold nanocomposite, CdTe-CdS core-shell quantum dot and gold nanoparticle were also investigated. The result showed sensitivity of the biosensor is 7.67-fold better if graphene-gold nanocomposite, CdTe-CdS core-shell quantum dot and gold nanoparticle are used. This could be ascribed to improvement of the conductivity between graphene nanosheets due to introduction of gold nanoparticles, ultrafast charge transfer from CdTe-CdS core-shell quantum dot to graphene nanosheets and gold nanoparticle due to unique electrochemical properties of the CdTe-CdS core-shell quantum dot and good biocompatibility of gold nanoparticle for glucose oxidase. The biosensor is of best sensitivity in all glucose

  16. EFFECT OF HEAT TREATMENT IN PRESENCE OF CdCl2 ON THE PHYSICAL PROPERTIES OF pCdTe/nCdS HETEROJUNCTION SOLAR CELLS

    Directory of Open Access Journals (Sweden)

    Amjad Al QASSEM

    2016-12-01

    Full Text Available  The article is a comprehensive study of the effect of heat treatment in presence of a cadmium chloride (CdCl2 on the physical properties of pCdTe/nCdS solar cells. Heat treatment process plays a key role in enhancing the pCdTe/nCdS hetero-structure photosensitivity, thus improving the performance of solar cells based on them. This article outlines the changes in the structural characteristics and photoelectric properties of such solar cells before and after heat treatment process. The two most popular methods of the heat treatment process based on cadmium chloride are also discussed. One may consider the CdCl2 heat treatment process as one of the very important stages of preparing CdTe/CdO/CdS solar cells, which improves the performance of these cells made in laboratories of the State University of Moldova.INFLUENȚA TRATĂRII TERMICE ÎN PREZENŢA CLORURII DE CADMIU (CdCl2 ASUPRA PROPRIE­TĂ­ŢILOR FIZICE ALE CELULELOR SOLARE CU HETERONCȚIUNEA pCdTe/nCdS Prezentăm un studiu cuprinzător al efectului tratării termice în prezenţa clorurii de cadmiu (CdCl2 asupra proprie­tă­ţilor fizice ale celulelor solare pCdTe/nCdS. Procesul de tratare termică joacă un rol-cheie în ameliorarea fotosensibilităţii heterostructurii pCdTe/nCdS, îmbunătăţind în aşa mod performanţa celulelor solare bazate pe ele. În articol sunt con­tu­rate schimbările în caracteristicile structurale şi proprietăţile fotoelectrice ale acestor celule solare până la şi după pro­cesul de tratare termică. De asemenea, sunt abordate cele mai răspândite metode de tratare termică bazate pe clorura de cadmiu. Tratarea termică în CdCl2 poate fi considerată o etapă foarte importantă în prepararea celulelor solare CdTe/CdO/CdS, care îmbunătăţeşte performanţa acestor celule fabricate în laboratoarele Universităţii de Stat din Moldova.

  17. A study of Sn addition on bonding arrangement of Se-Te alloys using far infrared transmission spectroscopy

    International Nuclear Information System (INIS)

    Kumar, Rajneesh; Rangra, V. S.; Sharma, Parikshit; Katyal, S. C.; Sharma, Pankaj

    2011-01-01

    Far infrared transmission spectra of Se 92 Te 8-x Sn x (x = 0, 1, 2, 3, 4, 5) glassy alloys are obtained in the spectral range 50-600 cm -1 at room temperature. The results are interpreted in terms of the vibrations of the isolated molecular units in such a way so as to preserve fourfold and twofold coordination for Sn and chalcogen atoms (Se,Te), respectively. With the addition of Sn, Far-IR spectra shift toward high frequency side and some new bands start appearing. Sn atoms appear to substitute for the selenium atoms in the outrigger sites due to large bond formation probability. Theoretical calculations of bond energy, relative probability of bond formation, force constant, and wave number were also made to justify the result.

  18. Translocation and neurotoxicity of CdTe quantum dots in RMEs motor neurons in nematode Caenorhabditis elegans

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yunli; Wang, Xiong; Wu, Qiuli; Li, Yiping; Wang, Dayong, E-mail: dayongw@seu.edu.cn

    2015-02-11

    Graphical abstract: - Highlights: • We investigated in vivo neurotoxicity of CdTe QDs on RMEs motor neurons in C. elegans. • CdTe QDs in the range of μg/L caused neurotoxicity on RMEs motor neurons. • Bioavailability of CdTe QDs may be the primary inducer for CdTe QDs neurotoxicity. • Both oxidative stress and cell identity regulate the CdTe QDs neurotoxicity. • CdTe QDs were translocated and deposited into RMEs motor neurons. - Abstract: We employed Caenorhabditis elegans assay system to investigate in vivo neurotoxicity of CdTe quantum dots (QDs) on RMEs motor neurons, which are involved in controlling foraging behavior, and the underlying mechanism of such neurotoxicity. After prolonged exposure to 0.1–1 μg/L of CdTe QDs, abnormal foraging behavior and deficits in development of RMEs motor neurons were observed. The observed neurotoxicity from CdTe QDs on RMEs motor neurons might be not due to released Cd{sup 2+}. Overexpression of genes encoding Mn-SODs or unc-30 gene controlling cell identity of RMEs neurons prevented neurotoxic effects of CdTe QDs on RMEs motor neurons, suggesting the crucial roles of oxidative stress and cell identity in regulating CdTe QDs neurotoxicity. In nematodes, CdTe QDs could be translocated through intestinal barrier and be deposited in RMEs motor neurons. In contrast, CdTe@ZnS QDs could not be translocated into RMEs motor neurons and therefore, could only moderately accumulated in intestinal cells, suggesting that ZnS coating might reduce neurotoxicity of CdTe QDs on RMEs motor neurons. Therefore, the combinational effects of oxidative stress, cell identity, and bioavailability may contribute greatly to the mechanism of CdTe QDs neurotoxicity on RMEs motor neurons. Our results provide insights into understanding the potential risks of CdTe QDs on the development and function of nervous systems in animals.

  19. Epitaxial growth of CdTe thin film on cube-textured Ni by metal-organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Gaire, C.; Rao, S.; Riley, M.; Chen, L.; Goyal, A.; Lee, S.; Bhat, I.; Lu, T.-M.; Wang, G.-C.

    2012-01-01

    Single crystal-like CdTe thin film has been grown by metalorganic chemical vapor deposition on cube-textured Ni(100) substrate. Using X-ray pole figure measurements we observed the epitaxial relationship of {111} CdTe //{001} Ni with [11 ¯ 0] CdTe //[010] Ni and [112 ¯ ] CdTe //[100] Ni . The 12 diffraction peaks in the (111) pole figure of CdTe film and their relative positions with respect to the four peak positions in the (111) pole figure of Ni substrate are consistent with four equivalent orientational domains of CdTe with three to four superlattice match of about 1.6% in the [11 ¯ 0] direction of CdTe and the [010] direction of Ni. The electron backscattered diffraction images show that the CdTe domains are 30° oriented from each other. These high structural quality films may find applications in low cost optoelectronic devices.

  20. CdCl{sub 2} treatment related diffusion phenomena in Cd{sub 1−x}Zn{sub x}S/CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Kartopu, G., E-mail: giray.kartopu@glyndwr.ac.uk; Clayton, A. J.; Barrioz, V.; Lamb, D. A.; Irvine, S. J. C. [Centre for Solar Energy Research (CSER), Glyndŵr University, OpTIC, St. Asaph Business Park, St. Asaph LL17 0JD (United Kingdom); Taylor, A. A. [Physics Department, Durham University, Durham DH1 3LE (United Kingdom)

    2014-03-14

    Utilisation of wide bandgap Cd{sub 1−x}Zn{sub x}S alloys as an alternative to the CdS window layer is an attractive route to enhance the performance of CdTe thin film solar cells. For successful implementation, however, it is vital to control the composition and properties of Cd{sub 1−x}Zn{sub x}S through device fabrication processes involving the relatively high-temperature CdTe deposition and CdCl{sub 2} activation steps. In this study, cross-sectional scanning transmission electron microscopy and depth profiling methods were employed to investigate chemical and structural changes in CdTe/Cd{sub 1−x}Zn{sub x}S/CdS superstrate device structures deposited on an ITO/boro-aluminosilicate substrate. Comparison of three devices in different states of completion—fully processed (CdCl{sub 2} activated), annealed only (without CdCl{sub 2} activation), and a control (without CdCl{sub 2} activation or anneal)—revealed cation diffusion phenomena within the window layer, their effects closely coupled to the CdCl{sub 2} treatment. As a result, the initial Cd{sub 1−x}Zn{sub x}S/CdS bilayer structure was observed to unify into a single Cd{sub 1−x}Zn{sub x}S layer with an increased Cd/Zn atomic ratio; these changes defining the properties and performance of the Cd{sub 1−x}Zn{sub x}S/CdTe device.

  1. Topological crystalline insulator PbxSn1-xTe thin films on SrTiO3 (001 with tunable Fermi levels

    Directory of Open Access Journals (Sweden)

    Hua Guo

    2014-05-01

    Full Text Available In this letter, we report a systematic study of topological crystalline insulator PbxSn1-xTe (0 < x < 1 thin films grown by molecular beam epitaxy on SrTiO3(001. Two domains of PbxSn1-xTe thin films with intersecting angle of α ≈ 45° were confirmed by reflection high energy diffraction, scanning tunneling microscopy, and angle-resolved photoemission spectroscopy (ARPES. ARPES study of PbxSn1-xTe thin films demonstrated that the Fermi level of PbTe could be tuned by altering the temperature of substrate whereas SnTe cannot. An M-shaped valance band structure was observed only in SnTe but PbTe is in a topological trivial state with a large gap. In addition, co-evaporation of SnTe and PbTe results in an equivalent variation of Pb concentration as well as the Fermi level of PbxSn1-xTe thin films.

  2. High-Efficiency Polycrystalline CdTe Thin-Film Solar Cells with an Oxygenated Amorphous CdS (a-CdS:O) Window Layer: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Wu, X.; Dhere, R. G.; Yan, Y.; Romero, M. J.; Zhang, Y.; Zhou, J.; DeHart, C.; Duda, A.; Perkins, C.; To, B.

    2002-05-01

    In the conventional CdS/CdTe device structure, the poly-CdS window layer has a bandgap of {approx}2.4 eV, which causes absorption in the short-wavelength region. Higher short-circuit current densities (Jsc) can be achieved by reducing the CdS thickness, but this can adversely impact device open-circuit voltage (Voc) and fill factor (FF). Also, poly-CdS film has about 10% lattice mismatch related to the CdTe film, which limits the improvement of device Voc and FF. In this paper, we report a novel window material: oxygenated amorphous CdS film (a-CdS:O) prepared at room temperature by rf sputtering. The a-CdS:O film has a higher optical bandgap (2.5-3.1 eV) than the poly-CdS film and an amorphous structure. The preliminary device results have demonstrated that Jsc of the CdTe device can be greatly improved while maintaining higher Voc and FF. We have fabricated a CdTe cell demonstrating an NREL-confirmed Jsc of 25.85 mA/cm2 and a total-area efficiency of 15.4%.

  3. Structural and optical characterization of CdTe quantum dots thin films

    International Nuclear Information System (INIS)

    El-Nahass, M.M.; Youssef, G.M.; Noby, Sohaila Z.

    2014-01-01

    Highlights: • CdTe QDs are prepared by hot injection method. • Thermally evaporated CdTeQDs thin films were prepared. • Structural characterization and analysis were done. • Optical parameters were studied. - Abstract: Cadmium telluride quantum dots (CdTe QDs) have been synthesized using hot-injection chemical technique. The CdTe QDs thin films were deposited onto optical flat fused quartz substrates using thermal evaporation technique. The CdTe QDs powder and the as deposited films were characterized using X-ray diffraction and high resolution transmission electron microscope (HRTEM). The X-ray analysis shows that both CdTe QDs powder and the as deposited films crystallize in cubic zinc-blende type structure with lattice parameter 6.46 Å and 6.45 Å, respectively. The X-ray calculation shows that the average crystallite size of the as deposited CdTe QDs films varied from 1.1 nm for the powder to 2.3 nm for the thin film. The HRTEM examination of the as deposited films shows that the average particle size vary from 2.5 nm for the powder to 2.7 nm for the thin film. For the as deposited films, the dependence of (αhν) 2 on the incident photon energy indicates that the optical transitions within the film are allowed direct with energies observed at E g1 ≅2eV and E g2 ≅2.3eV which attributed to quantum confinement effect. The optical band gap increases from 1.5 eV for microstructure CdTe to 2 eV for nanostructure quantum dots which corresponding to wavelength(620 nm) so it is a great benefit to use CdTe quantum dots as solar harvesting devices application in solar spectrum region (400–800 nm). Urbach energy is calculated and found to be 360 meV which is higher than microstructure CdTe. The refractive index and refractive index dispersion of the as deposited CdTe QDs film has been calculated from transmission and reflection spectra. It has been found that the refractive index is reduced from (2.66) for microstructure CdTe to be (1.7) for CdTe quantum

  4. ZnS-Passivated CdSe/CdS Co-sensitized Mesoporous Zn2SnO4 Based Solar Cells

    International Nuclear Information System (INIS)

    Kim, Kyungho; Park, Ji Eun; Park, Eun Su; Park, Yun Chang; Kim, Joosun; Im, Chan; Lee, Man-Jong

    2014-01-01

    Graphical abstract: - Highlights: • Mesoporous Zn 2 SnO 4 sensitized by CdSe/CdS QDs were synthesized via a two-step sequential process. • Assembled QDs were characterized by HRTEM and STEM mapping. • Efficiency increase in CdSe/CdS co-sensitized Zn 2 SnO 4 DSSCs is discussed. • The role of ZnS passivation layer is discussed by impedance spectroscopy. - Abstract: CdS and CdSe/CdS quantum dot (QD) sensitizers were assembled onto mesoporous ternary Zn 2 SnO 4 photoanodes using a two-step sequential process of successive ionic layer absorption and reaction (SILAR) and chemical bath deposition (CBD) for QD-cosensitized solar cell applications. The assembled CdS and CdSe QDs were observed using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), high-resolution TEM (HRTEM), and STEM/energy-dispersive X-ray spectroscopy (EDS) elemental mapping. CdSe/CdS cosensitized Zn 2 SnO 4 -based cells showed a higher absorption onset position, a stepwise band-edge level alignment, and, thereby, an improved power conversion efficiency (PCE) of 1.628% under one-sun conditions, which is the best result obtained using mesoporous Zn 2 SnO 4 reported to date. In addition, the effect of a ZnS passivation layer on the photovoltaic performance and aging behavior has been investigated. Electrochemical impedance spectroscopy (EIS) showed that the main role of the ZnS layer is to enhance the aging behavior of the CdSe/CdS/Zn 2 SnO 4 cells by improving the electron lifetime and charge recombination

  5. Structural and optical properties of alloyed quaternary CdSeTeS core and CdSeTeS/ZnS core–shell quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Adegoke, Oluwasesan, E-mail: adegoke.sesan@mailbox.co.za [Department of Chemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Lynnwood Road, Pretoria 0002 (South Africa); Nyokong, Tebello, E-mail: t.nyokong@ru.ac.za [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa); Forbes, Patricia B.C., E-mail: patricia.forbes@up.ac.za [Department of Chemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Lynnwood Road, Pretoria 0002 (South Africa)

    2015-10-05

    Highlights: • Alloyed quaternary CdSeTeS core quantum dots (QDs) were synthesized. • Passivation was carried out using a ZnS shell. • Quaternary CdSeTeS core exhibited unique optical properties over CdSeTe/ZnS. • CdSeTeS can be employed as a useful alternative to core/shell QDs. - Abstract: Synthesis of fluorescent alloyed quantum dots (QDs) with unique optical properties suitable for a wide array of chemical, physical and biological applications is of research interest. In this work, highly luminescent and photostable alloyed quaternary CdSeTeS core QDs of two different sizes were fabricated via the organometallic hot-injection synthetic route. Characterization of the nanocrystals were performed using TEM, XRD, UV/vis and fluorescence spectrophotometric techniques. We have demonstrated in this work that the well fabricated alloyed quaternary CdSeTeS core QDs possess unique optical properties that are advantageous over conventional core/shell systems. Formation of the CdSeTeS/ZnS core/shell with the desired optical properties comes with a number of challenges, hence the advantages of the quaternary alloyed core over the core/shell QDs are (i) avoidance of the challenging process of determining the proper shell thickness which can provide the desired optical properties in the core/shell system and (ii) avoidance of the lattice-induced mismatch between the core and the shell material which can either lead to incomplete exciton confinement or dislocation at the core/shell interface.

  6. Charge separation and transfer in hybrid type II tunneling structures of CdTe and CdSe nanocrystals

    International Nuclear Information System (INIS)

    Gross, Dieter Konrad Michael

    2013-01-01

    Closely packed nanocrystal systems have been investigated in this thesis with respect to charge separation by charge carrier tunneling. Clustered and layered samples have been analyzed using PL-measurements and SPV-methods. The most important findings are reviewed in the following. A short outlook is also provided for potential further aspects and application of the presented results. The main purpose of this thesis was to find and quantify electronic tunneling transfer in closely packed self-assembled nanocrystal structures presenting quantum mechanical barriers of about 1 nm width. We successfully used hybrid assemblies of CdTe and CdSe nanocrystals where the expected type II alignment between CdTe and CdSe typically leads to a concentration of electrons in CdSe and holes in CdTe nanocrystals. We were able to prove the charge selectivity of the CdTe-CdSe nanocrystal interface which induces charge separation. We mainly investigated the effects related to the electron transfer from CdTe to CdSe nanocrystals. Closely packing was achieved by two independent methods: the disordered colloidal clustering in solution and the layered assembly on dry glass substrates. Both methods lead to an inter-particle distance of about 1 nm of mainly organic material which acts as a tunneling barrier. PL-spectroscopy was applied. The PL-quenching of the CdTe nanocrystals in hybrid assemblies indicates charge separation by electron transfer from CdTe to CdSe nanocrystals. A maximum quenching rate of up to 1/100 ps was measured leading to a significant global PL-quenching of up to about 70 % for the CdTe nanocrystals. It was shown that charge separation dynamics compete with energy transfer dynamics and that charge separation typically dominates. The quantum confinement effect was used to tune the energetic offset between the CdTe and CdSe nanocrystals. We thus observe a correlation of PL-quenching and offset of the energy states for the electron transfer. The investigated PL

  7. Charge separation and transfer in hybrid type II tunneling structures of CdTe and CdSe nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Gross, Dieter Konrad Michael

    2013-11-08

    Closely packed nanocrystal systems have been investigated in this thesis with respect to charge separation by charge carrier tunneling. Clustered and layered samples have been analyzed using PL-measurements and SPV-methods. The most important findings are reviewed in the following. A short outlook is also provided for potential further aspects and application of the presented results. The main purpose of this thesis was to find and quantify electronic tunneling transfer in closely packed self-assembled nanocrystal structures presenting quantum mechanical barriers of about 1 nm width. We successfully used hybrid assemblies of CdTe and CdSe nanocrystals where the expected type II alignment between CdTe and CdSe typically leads to a concentration of electrons in CdSe and holes in CdTe nanocrystals. We were able to prove the charge selectivity of the CdTe-CdSe nanocrystal interface which induces charge separation. We mainly investigated the effects related to the electron transfer from CdTe to CdSe nanocrystals. Closely packing was achieved by two independent methods: the disordered colloidal clustering in solution and the layered assembly on dry glass substrates. Both methods lead to an inter-particle distance of about 1 nm of mainly organic material which acts as a tunneling barrier. PL-spectroscopy was applied. The PL-quenching of the CdTe nanocrystals in hybrid assemblies indicates charge separation by electron transfer from CdTe to CdSe nanocrystals. A maximum quenching rate of up to 1/100 ps was measured leading to a significant global PL-quenching of up to about 70 % for the CdTe nanocrystals. It was shown that charge separation dynamics compete with energy transfer dynamics and that charge separation typically dominates. The quantum confinement effect was used to tune the energetic offset between the CdTe and CdSe nanocrystals. We thus observe a correlation of PL-quenching and offset of the energy states for the electron transfer. The investigated PL

  8. RGDS-conjugated CdSeTe/CdS quantum dots as near-infrared fluorescent probe: preparation, characterization and bioapplication

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhenzhen; Zhang, Qiyi; Huang, Huaying; Ren, Changjing; Pan, Yujin; Wang, Qing; Zhao, Qiang, E-mail: Zhaoqiang@scu.edu.cn [Sichuan University, School of Chemical Engineering (China)

    2016-12-15

    In the experiments, high-quality, water-soluble and near-infrared (NIR)-emitting CdSeTe and CdSeTe/CdS quantum dots (QDs) were successfully prepared. The average size of CdSeTe⁄CdS QDs was 7.68 nm and CdSeTe QDs was 4.33 nm. Arginine-glycine-aspartic-serine acid (RGDS) peptides were linked to CdSeTe/CdS QDs by N-(3-(dimethylamino)propyl)-N′-ehtylcarbodiimide hydrochloride (EDC) and N′-hydroxysuccinimide (NHS). The prepared RGDS-tagged NIR CdSeTe/CdS QDs (denoted as RGDS-CdSeTe/CdS) had an average diameter of 24.83 nm and were used for cancer cell immunofluorescence imaging. The characteristics of RGDS-conjugated CdSeTe/CdS such as morphology, structure, spectra, stability, cytotoxicity, and near-infrared microscopic imaging were investigated in detail. HepG2 cells were incubated with the novel fluorescent probe (RGDS-CdSeTe/CdS), which realized immunofluorescence targeting and imaging. The results reported here open up new perspectives for integrin-targeted near-infrared imaging and may aid in tumor detection including imaging-guided surgery.

  9. Aqueous synthesis of high-fluorescence CdZnTe alloyed quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Jingwei; Li, Dongmei, E-mail: dmli@mail.shu.edu.cn; Cheng, Tao; Ren, Bing; Wang, Gang; Li, Jie

    2014-03-15

    Highlights: • We have synthesized the CdZnTe QDs with a Zn/Cd molar ratio from 1 to 7. • The reaction was happened in weak acid condition. • The fluorescence emitting peak was continuously tunable from 490 nm to 660 nm. • The maximum quantum yield of our synthesized CdZnTe QDs has reached 78.97%. • Our sample showed excellent stability against time. -- Abstract: High luminescent CdZnTe quantum dots (QDs) were synthesized by a one-step aqueous method using 3-mercapto propionic acid (MPA) as a stabilizer. The as-prepared samples are in good homogeneity and dispersity with an average particle size of 5 nm. Accordingly, the size and composition-dependent fluorescent emission wavelength of the resultant CdZnTe alloyed QDs can be continuously tuned from 490 to 660 nm. Compared with the difficult acquisition of CdZnTe QDs with a high Zn/Cd molar ratio in alkaline condition, CdZnTe QDs with a Zn/Cd molar ratio from 1 to 7 has been obtained in weak acid condition by adjusting the pH value of precursor solution. The maximum quantum yield has reached nearly 80% without any post-treatment. And it also showed excellent stability against time.

  10. PENINGKATAN KUALITAS FILM TIPIS CdTe SEBAGAI ABSORBER SEL SURYA DENGAN MENGGUNAKAN DOPING TEMBAGA (Cu

    Directory of Open Access Journals (Sweden)

    P. Marwoto

    2012-07-01

    Full Text Available Film tipis CdTe dengan doping tembaga (Cu berkonsenterasi 2% telah berhasil ditumbuhkan di atas substrat Indium Tin Oxide (ITO dengan metode dc magnetron sputtering. Penelitian ini dilakukan untuk mengetahui pengaruh doping Cu(2% terhadap struktur morfologi, struktur kristal, fotoluminisensi dan resistivitas listrik film CdTe. Citra morfologi Scanning Electron Microscopy (SEM dan hasil analisis struktur dengan X-Ray Diffraction (XRD menunjukkan bahwa film CdTe:Cu(2% mempunyai citra permukaan dan struktur kristal yang lebih sempurna dibandingkan film CdTe tanpa doping. Hasil analisis spektrometer fotoluminisensi menunjukkan bahwa film CdTe dan CdTe(2% mempunyai puncak fotoluminisensi pada tiga panjang gelombang yang identik yaitu 685 nm (1,81 eV, 725 nm (1,71 eV dan 740 nm (1,67 eV. Film CdTe dengan doping Cu(2% memiliki intensitas puncak fotoluminisensi yang lebih tajam pada pita energi 1,81 eV dibandingkan dengan film CdTe tanpa doping. Pengukuran arus dan tegangan (I-V menunjukkan bahwa pemberian doping Cu(2% dapat menurunkan resistivitas film dari 8,40x109 Ωcm menjadi 6,92x105 Ωcm. Sebagai absorber sel surya, kualitas film tipis CdTe telah berhasil ditingkatkan dengan pemberian doping Cu(2%.CdTe:Cu(2% thin film has been successfully grown on Indium Tin Oxide (ITO substrates by using dc magnetron sputtering. This study was carried out in order to investigate the effect of Cu(2% doping on the morphologycal structure, crystal structure, photoluminesence, and resistivity of CdTe thin film. Scanning Electron Microscopy (SEM  images and X-Ray Diffraction (XRD results showed that CdTe:Cu(2% thin film has morphologycal and crystal structures more perfect than undoped CdTe film. Photoluminesence spectroscopy results showed that CdTe and CdTe:Cu(2% thin films have luminesence peak at three identical wevelength regions i.e. 685 nm (1.81 eV, 725 nm (1.71 eV and 740 nm (1.67 eV however CdTe:Cu(2% film shows sharper photoluminescence peak at band

  11. Influence of Au diffusion on structural, electrical and optical characteristics of CdTe thin films

    International Nuclear Information System (INIS)

    Dzhafarov, T D; Caliskan, M

    2007-01-01

    Diffusion of Au and its effects on structural, electrical and optical properties of CdTe films fabricated by the close-spaced sublimation technique have been investigated. Diffusion of Au was studied in the range 400-550 deg. C using energy dispersive x-ray fluorescence analysis. Au-doped and un-doped CdTe films were characterized by x-ray diffraction (XRD), electrical and optical absorption measurements. The temperature dependence of the diffusion coefficient of Au in CdTe films is described as D = 4.4 x 10 -7 exp(-0.54 eV/kT). The mechanism of Au diffusion in polycrystalline CdTe films is attributed to the fast migration of Au along grain boundaries with simultaneous penetration into grains and settling on Cd-vacancies. It is supposed that the weak influence of Au diffusion on XRD patterns of CdTe films can be explained by dispersal of Au atoms preferentially on Cd-vacancies owing to proximity of the covalent radius of Au and Cd. Au atoms, placed on Cd-vacancies (Au Cd ) during fast cooling from diffusion temperature to room temperature, show an acceptor behaviour with an energy level about of E v + 0.2 eV. The nature of this level is discussed

  12. Doping of polycrystalline CdTe for high-efficiency solar cells on flexible metal foil

    Science.gov (United States)

    Kranz, Lukas; Gretener, Christina; Perrenoud, Julian; Schmitt, Rafael; Pianezzi, Fabian; La Mattina, Fabio; Blösch, Patrick; Cheah, Erik; Chirilă, Adrian; Fella, Carolin M.; Hagendorfer, Harald; Jäger, Timo; Nishiwaki, Shiro; Uhl, Alexander R.; Buecheler, Stephan; Tiwari, Ayodhya N.

    2013-08-01

    Roll-to-roll manufacturing of CdTe solar cells on flexible metal foil substrates is one of the most attractive options for low-cost photovoltaic module production. However, various efforts to grow CdTe solar cells on metal foil have resulted in low efficiencies. This is caused by the fact that the conventional device structure must be inverted, which imposes severe restrictions on device processing and consequently limits the electronic quality of the CdTe layer. Here we introduce an innovative concept for the controlled doping of the CdTe layer in the inverted device structure by means of evaporation of sub-monolayer amounts of Cu and subsequent annealing, which enables breakthrough efficiencies up to 13.6%. For the first time, CdTe solar cells on metal foil exceed the 10% efficiency threshold for industrialization. The controlled doping of CdTe with Cu leads to increased hole density, enhanced carrier lifetime and improved carrier collection in the solar cell. Our results offer new research directions for solving persistent challenges of CdTe photovoltaics.

  13. Synthesis and characterization of TGA-capped CdTe nanoparticles embedded in PVA matrix

    Energy Technology Data Exchange (ETDEWEB)

    Tripathi, S.K.; Kaur, Ramneek; Sharma, Mamta [Panjab University, Department of Physics, Center of Advanced Study in Physics, Chandigarh (India)

    2014-10-25

    This paper reports the synthesis and characterization of TGA-capped CdTe nanoparticles and its nanocomposite in a PVA matrix prepared by ex situ technique. The crystallite sizes of the CdTe nanoparticles and nanocomposite calculated from X-ray diffraction patterns are 6.07 and 7.75 nm with hexagonal structure, respectively. The spherical nature of the CdTe nanoparticles is confirmed from transmission electron microscopy measurements. Fourier transform infrared spectroscopy shows good interaction between the CdTe nanoparticles and PVA matrix. The absorption and emission spectra have also been studied. The stability of the TGA-capped CdTe nanoparticles increases after dispersion in a PVA matrix. In electrical measurements, the dark conductivity and the steady-state photoconductivity of CdTe nanocomposite thin films have been studied. The effect of temperature and intensity on the transient photoconductivity of CdTe nanocomposite is also studied. The values of differential life time have been calculated from the decay of photocurrent with time. The non-exponential decay of photoconductivity is observed indicating that the traps exist at all the energies in the band gap, making these materials suitable for various optoelectronic devices. (orig.)

  14. Synthesis and characterization of TGA-capped CdTe nanoparticles embedded in PVA matrix

    International Nuclear Information System (INIS)

    Tripathi, S.K.; Kaur, Ramneek; Sharma, Mamta

    2015-01-01

    This paper reports the synthesis and characterization of TGA-capped CdTe nanoparticles and its nanocomposite in a PVA matrix prepared by ex situ technique. The crystallite sizes of the CdTe nanoparticles and nanocomposite calculated from X-ray diffraction patterns are 6.07 and 7.75 nm with hexagonal structure, respectively. The spherical nature of the CdTe nanoparticles is confirmed from transmission electron microscopy measurements. Fourier transform infrared spectroscopy shows good interaction between the CdTe nanoparticles and PVA matrix. The absorption and emission spectra have also been studied. The stability of the TGA-capped CdTe nanoparticles increases after dispersion in a PVA matrix. In electrical measurements, the dark conductivity and the steady-state photoconductivity of CdTe nanocomposite thin films have been studied. The effect of temperature and intensity on the transient photoconductivity of CdTe nanocomposite is also studied. The values of differential life time have been calculated from the decay of photocurrent with time. The non-exponential decay of photoconductivity is observed indicating that the traps exist at all the energies in the band gap, making these materials suitable for various optoelectronic devices. (orig.)

  15. Preparation of ultra-high purity CdTe single crystals

    International Nuclear Information System (INIS)

    Wang, J.F.; Song, S.H.; Ishikawa, Y.; Isshiki, M.

    2005-01-01

    High-purity and quality CdTe single crystals are very important for their basic study, as well as practical applications. For this reason, Cd was purified by vacuum distillation (VD) and overlap zone-melting (OZM) method, and Te was purified by normal freezing method. Refined Cd was evaluated by glow discharge mass spectroscopy (GDMS) and residual resistivity ratio (RRR) measurement and Te was evaluated by low-temperature photoluminescence (PL) spectra. Results showed that refined Cd and Te have the purity of 6N-up. Using the refined Cd and Te as starting materials, extremely high-purity CdTe single crystals were prepared by the traditional vertical Bridgman technique. The crystals were characterized by low temperature high-resolution PL spectroscopy. Only a sharp peak at 1.5896 eV was detected in exciton emission region. The full width at half-maximum (FWHM) is less than 0.31 meV. These results indicate that the CdTe crystals are of extremely high-purity and quality

  16. Emission variation in infrared (CdSeTe)/ZnS quantum dots conjugated to antibodies

    Science.gov (United States)

    Jaramillo Gómez, J. A.; Casas Espinola, J. L.; Douda, J.

    2014-11-01

    The paper presents the photoluminescence (PL) and Raman scattering investigations of infrared CdSeTe/ZnS quantum dots (QDs) with emission at 800 nm (1.60 eV) in nonconjugated states and after the conjugation to the anti-papilloma virus antibodies (Ab). The Raman scattering study has shown that the CdSeTe core includes two layers with different material compositions such as: CdSe0.5Te0.5 and CdSe0.7Te0.3. PL spectra of nonconjugated CdSeTe/ZnS QDs are characterized by two Gaussian shape PL bands related to exciton emission in the CdSeTe core and in intermediate layer at the core/shell interface. PL spectra of bioconjugated QDs have changed essentially: the main PL band related to the core emission shifts into high energy and become asymmetric. The energy diagram of double core/shell CdSeTe/ZnS QDs has been analyzed to explain the PL spectrum of nonconjugated QDs and its transformation at the bioconjugation to the papiloma virus antibodies. It is shown that the PL spectrum transformation in bioconjugated QDs can be a powerful technique for biology and medicine.

  17. Emission variation in infrared (CdSeTe)/ZnS quantum dots conjugated to antibodies

    Energy Technology Data Exchange (ETDEWEB)

    Jaramillo Gómez, J.A. [UPIITA – Instituto Politécnico Nacional, México D. F. 07320, México (Mexico); Casas Espinola, J.L., E-mail: jlcasas@esfm.ipn.mx [ESFM – Instituto Politécnico Nacional, México D. F. 07738, México (Mexico); Douda, J. [UPIITA – Instituto Politécnico Nacional, México D. F. 07320, México (Mexico)

    2014-11-15

    The paper presents the photoluminescence (PL) and Raman scattering investigations of infrared CdSeTe/ZnS quantum dots (QDs) with emission at 800 nm (1.60 eV) in nonconjugated states and after the conjugation to the anti-papilloma virus antibodies (Ab). The Raman scattering study has shown that the CdSeTe core includes two layers with different material compositions such as: CdSe{sub 0.5}Te{sub 0.5} and CdSe{sub 0.7}Te{sub 0.3}. PL spectra of nonconjugated CdSeTe/ZnS QDs are characterized by two Gaussian shape PL bands related to exciton emission in the CdSeTe core and in intermediate layer at the core/shell interface. PL spectra of bioconjugated QDs have changed essentially: the main PL band related to the core emission shifts into high energy and become asymmetric. The energy diagram of double core/shell CdSeTe/ZnS QDs has been analyzed to explain the PL spectrum of nonconjugated QDs and its transformation at the bioconjugation to the papiloma virus antibodies. It is shown that the PL spectrum transformation in bioconjugated QDs can be a powerful technique for biology and medicine.

  18. Semi-insulating (Cd,Mn)Te:V crystals: Electrical contacts

    International Nuclear Information System (INIS)

    Witkowska-Baran, M.; Mycielski, A.; Szadkowski, A.J.; Lusakowska, E.; Domu-khovski, V.; Jakiela, R.; Witkowska, B.; Kaliszek, W.

    2007-01-01

    The high-resistivity (Cd,Mn)Te is believed to be suitable to succesfully replace the commonly used (Cd,Zn)Te system as a material for manufacturing large-area X- and γ-ray detectors. The purpose of our study was to elaborate a method of preparing high quality (Cd,Mn)Te crystal plates as well as a technique of producing good electrical contacts to that material. (Cd,Mn)Te was grown using the Bridgman method. The crystals were doped with vanadium to the level of 10 16 cm -3 . The crystals are twinned in the (111) plane, but by slicing the crystal parallel to the twinning plane we obtained monocrystalline plates of large area (e.g. 30 x 30 mm 2 ), which is essential for application purposes. Proper annealing of those plates in cadmium vapours allowed us to reduce the number of cadmium vacancies forming during the growth process. Due to the vanadium dopant acting as a compensating centre we obtained a semi-insulating material. In order to obtain good contacts to the (Cd,Mn)Te plates we used the method proposed initially for CdTe by Rioux et al. The ZnTe:Sb layers (∝1 μm thick) were grown on the epi-ready (Cd,Mn)Te:V plates by the MBE technique. The grown layers were p-type and formed a good electrical contact to the crystal plates. Finally - a standard technique was used to cover the ZnTe layer by a metal layer. The contacts formed on (111) surfaces of (Cd,Mn)Te were studied. We believe that the contacts to the (111) surface are important for applications. In the paper we describe techniques of preparing electrical contacts and results of their characterization. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Recent Progress on Solution-Processed CdTe Nanocrystals Solar Cells

    Directory of Open Access Journals (Sweden)

    Hao Xue

    2016-07-01

    Full Text Available Solution-processed CdTe nanocrystals (NCs photovoltaic devices have many advantages, both in commercial manufacture and daily operation, due to the low-cost fabrication process, which becomes a competitive candidate for next-generation solar cells. All solution-processed CdTe NCs solar cells were first reported in 2005. In recent years, they have increased over four-fold in power conversion efficiency. The latest devices achieve AM 1.5 G power conversion efficiency up to 12.0%, values comparable to those of commercial thin film CdTe/CdS solar cells fabricated by the close-space sublimation (CSS method. Here we review the progress and prospects in this field, focusing on new insights into CdTe NCs synthesized, device fabrication, NC solar cell operation, and how these findings give guidance on optimizing solar cell performance.

  20. FP-LAPW Calculations of the EFG at Cd Impurities in Rutile SnO2

    International Nuclear Information System (INIS)

    Errico, L. A.; Fabricius, G.; Renteria, M.

    2001-01-01

    We report an ab initio study of the electric-field gradient (EFG) at Cd impurities located at the cation site in the semiconductor SnO 2 (rutile phase). The study was performed with the WIEN97 implementation of the FP-LAPW method. In order to simulate the diluted Cd-impurity in the SnO 2 host and to calculate the electronic structure of the system we used a 72-atoms super-cell, studying the relaxation introduced by the impurity in the lattice. The free-relaxation process performed shows that the relaxations of the oxygen nearest-neighbors of the impurity are not isotropic. Our prediction for the EFG tensor are compared with experimental results and point-charge model predictions

  1. Growth and characterization of Hg/sub 1-x/Cd/sub x/Te on CdTe substrates, prepared by organometallic epitaxy

    International Nuclear Information System (INIS)

    Bhat, I.B.; Ghandhi, S.K.

    1986-01-01

    Hg/sub 1-x/Cd/sub x/Te layers have been grown on CdTe substrates using dimethylcadmium, diethyltelluride and mercury in a horizontal reactor. Details of conditions for growth of these layers are presented in this paper. Specular surfaces of Hg/sub 1-x/Cd/sub x/Te with x ≥ 0.15 were obtained on (100) 3 0 → (110) oriented CdTe substrates. Both n-type and rho-type layers could be obtained. The mobility of these layers was measured over the temperature range of 10 K to 300 K. The mobility of n-type Hg/sub .81/Cd/sub .19/Te layers, measured at 2.1 kG, was 3.0 x 10/sup 5/ cm/sup 2//V-sec at 60 K, falling to 2 x 10/sup 5/ cm/sup 2//V-sec at 10 K. P-type layers were also grown, and are described in this paper

  2. Oxygen Incorporation During Fabrication of Substrate CdTe Photovoltaic Devices: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Duenow, J. N.; Dhere, R. G.; Kuciauskas, D.; Li, J. V.; Pankow, J. W.; DeHart, C. M.; Gessert, T. A.

    2012-06-01

    Recently, CdTe photovoltaic (PV) devices fabricated in the nonstandard substrate configuration have attracted increasing interest because of their potential compatibility with flexible substrates such as metal foils and polymer films. This compatibility could lead to the suitability of CdTe for roll-to-roll processing and building-integrated PV. Currently, however, the efficiencies of substrate CdTe devices reported in the literature are significantly lower ({approx}6%-8%) than those of high-performance superstrate devices ({approx}17%) because of significantly lower open-circuit voltage (Voc) and fill factor (FF). In our recent device development efforts, we have found that processing parameters required to fabricate high-efficiency substrate CdTe PV devices differ from those necessary for traditional superstrate CdTe devices. Here, we investigate how oxygen incorporation in the CdTe deposition, CdCl2 heat treatment, CdS deposition, and post-deposition heat treatment affect device characteristics through their effects on the junction. By adjusting whether oxygen is incorporated during these processing steps, we have achieved Voc values greater than 860 mV and efficiencies greater than 10%.

  3. Disorder dependence of helical edge states in HgTe/CdTe quantum wells

    International Nuclear Information System (INIS)

    Chen Liang; Liu Qin; Lin Xulin; Zhang Xiaogang; Jiang, Xunya

    2012-01-01

    In recent years, extensive attention has been focused on a new topological phase induced by nonmagnetic disorder, known as the topological Anderson insulator (TAI). In this work, we study the disorder strength dependence of the edge states in TAI phase in disordered HgTe/CdTe quantum wells. It is shown clearly that the disorder-induced edge states appear above a critical disorder strength after a gap-closing phase transition. These edge states are then found to decline with an increase of disorder strength in a stepwise pattern due to the finite-width effect, where the opposite edges couple to each other through the localized bulk states. This is in sharp contrast with the localization of the edge states themselves by time-reversal symmetry breaking. The size-independent phase boundaries are further obtained through scaling analysis, where a metallic phase is found separating two topologically distinct phases, which is due to the Fermi energy and mass renormalization. (paper)

  4. Cadmium sulfate and CdTe-quantum dots alter DNA repair in zebrafish (Danio rerio) liver cells

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Song; Cai, Qingsong [The Institute of Environmental and Human Health, Texas Tech University, Lubbock, TX 79416 (United States); Chibli, Hicham [Department of Biomedical Engineering, McGill University, Montréal, QC H3A 2B4 (Canada); Allagadda, Vinay [The Institute of Environmental and Human Health, Texas Tech University, Lubbock, TX 79416 (United States); Nadeau, Jay L. [Department of Biomedical Engineering, McGill University, Montréal, QC H3A 2B4 (Canada); Mayer, Gregory D., E-mail: greg.mayer@ttu.edu [The Institute of Environmental and Human Health, Texas Tech University, Lubbock, TX 79416 (United States)

    2013-10-15

    Increasing use of quantum dots (QDs) makes it necessary to evaluate their toxicological impacts on aquatic organisms, since their contamination of surface water is inevitable. This study compares the genotoxic effects of ionic Cd versus CdTe nanocrystals in zebrafish hepatocytes. After 24 h of CdSO{sub 4} or CdTe QD exposure, zebrafish liver (ZFL) cells showed a decreased number of viable cells, an accumulation of Cd, an increased formation of reactive oxygen species (ROS), and an induction of DNA strand breaks. Measured levels of stress defense and DNA repair genes were elevated in both cases. However, removal of bulky DNA adducts by nucleotide excision repair (NER) was inhibited with CdSO{sub 4} but not with CdTe QDs. The adverse effects caused by acute exposure of CdTe QDs might be mediated through differing mechanisms than those resulting from ionic cadmium toxicity, and studying the effects of metallic components may be not enough to explain QD toxicities in aquatic organisms. - Highlights: • Both CdSO{sub 4} and CdTe QDs lead to cell death and Cd accumulation. • Both CdSO{sub 4} and CdTe QDs induce cellular ROS generation and DNA strand breaks. • Both CdSO{sub 4} and CdTe QDs induce the expressions of stress defense and DNA repair genes. • NER repair capacity was inhibited with CdSO{sub 4} but not with CdTe QDs.

  5. Study of CdTe/CdS solar cell at low power density for low-illumination applications

    Energy Technology Data Exchange (ETDEWEB)

    Devi, Nisha, E-mail: nishatanwer1989@gmail.com; Aziz, Anver, E-mail: aaziz@jmi.ac.in [Department Of Physics, Solar PV Lab, Jamia Millia Islamia, New Delhi-110025 (India); Datta, Shouvik [Department of Physics, IISER-Pune, Dr.homi Bhabha road, Pashan, Pune-411008 (India)

    2016-05-06

    In this paper, we numerically investigate CdTe/CdS PV cell properties using a simulation program Solar Cell Capacitance Simulator in 1D (SCAPS-1D). A simple structure of CdTe PV cell has been optimized to study the effect of temperature, absorber thickness and work function at very low incident power. Objective of this research paper is to build an efficient and cost effective solar cell for portable electronic devices such as portable computers and cell phones that work at low incident power because most of such devices work at diffused and reflected sunlight. In this report, we simulated a simple CdTe PV cell at very low incident power, which gives good efficiency.

  6. A new method for preparation of (Cd,Hg)Te thin films

    International Nuclear Information System (INIS)

    Nguyen Van Khai; Ho Thi Phuong; Ta Hong Ngat; Nguyen Van Sung.

    1987-11-01

    A new method for the preparation of (Cd,Hg)Te thin films has been described. This method is based on deposition of polycrystal Cd z Hg 1-z Te on a single crystal CdTe slice. The growth process is carried out in a strong temperature gradient of (50-100)K/cm during a period of (1-24) hours. The optical parameters of the grown films have been measured at the room temperature while the electrical parameters at liquid nitrogen temperature. (author). 14 refs, 4 figs

  7. Doping of polycrystalline CdTe for high-efficiency solar cells on flexible metal foil

    OpenAIRE

    Kranz Lukas; Gretener Christina; Perrenoud Julian; Schmitt Rafael; Pianezzi Fabian; La Mattina Fabio; Blösch Patrick; Cheah Erik; Chirila Adrian; Fella Carolin M.; Hagendorfer Harald; Jäger Timo; Nishiwaki Shiro; Uhl Alexander R.; Buecheler S.

    2013-01-01

    Roll to roll manufacturing of CdTe solar cells on flexible metal foil substrates is one of the most attractive options for low cost photovoltaic module production. However various efforts to grow CdTe solar cells on metal foil have resulted in low efficiencies. This is caused by the fact that the conventional device structure must be inverted which imposes severe restrictions on device processing and consequently limits the electronic quality of the CdTe layer. Here we introduce an innovative...

  8. Simulation of CdTe:Ge crystal properties for nuclear radiation detectors

    Energy Technology Data Exchange (ETDEWEB)

    Sochinskii, N.V. [Instituto de Microelectronica de Madrid, CNM-CSIC, c/Isaac Newton 8 (PTM), Tres Cantos 28760, Madrid (Spain)]. E-mail: ms@imm.cnm.csic.es; Lozano, M. [Instituto de Microelectronica de Barcelona, CNM-CSIC, Campus UAB, Bellaterra 08193, Barcelona (Spain); Pellegrini, G. [Instituto de Fisica de Altas Energias, Campus UAB, Bellaterra 08193, Barcelona (Spain); Ullan, M. [Instituto de Microelectronica de Barcelona, CNM-CSIC, Campus UAB, Bellaterra 08193, Barcelona (Spain)

    2006-11-30

    We report on the simulation results of the electrical properties of a coplanar detector made from Ge-doped CdTe crystals. The simulations have been performed using the commercial modeling package MEDICI. The detailed models of material behavior have been created by varying the concentration of three standard traps associated with CdTe:Ge crystals. These traps are the A-center related to Cd vacancy-residual impurity complex, the Te vacancy defect and the Ge impurity. Their energetic positions were measured by photoluminescence technique. The simulation has revealed the effects of the traps on several important detector characteristics such as leakage current and electric field distribution.

  9. Mechanism of Nanostructure Formation on a Surface of CdZnTe Crystal by Laser Irradiation

    OpenAIRE

    Medvids, A; Mičko, A

    2009-01-01

    Since crystalline Cd1-xZnxTe is widely used in radiation techniques to produce X-ray, gamma-ray, and other hard radiation detectors, present work is a further study of processes, occurring near the surface of Cd1-xZnxTe under laser radiation. Surface morphology and optical property change of Cd0.9Zn0.1Te crystal near-surface layer after irradiation with laser, aimed to create graded band-gap, was investigated. As a radiation source Nd:YAG laser working in Q-modulation mode with parameters...

  10. Simulation of CdTe:Ge crystal properties for nuclear radiation detectors

    International Nuclear Information System (INIS)

    Sochinskii, N.V.; Lozano, M.; Pellegrini, G.; Ullan, M.

    2006-01-01

    We report on the simulation results of the electrical properties of a coplanar detector made from Ge-doped CdTe crystals. The simulations have been performed using the commercial modeling package MEDICI. The detailed models of material behavior have been created by varying the concentration of three standard traps associated with CdTe:Ge crystals. These traps are the A-center related to Cd vacancy-residual impurity complex, the Te vacancy defect and the Ge impurity. Their energetic positions were measured by photoluminescence technique. The simulation has revealed the effects of the traps on several important detector characteristics such as leakage current and electric field distribution

  11. Pre-transition phenomena in CdTe near the melting point

    Science.gov (United States)

    Shcherbak, L.

    1999-02-01

    The influence of slight (up to 2 mol%) CdTe doping by In or Ge on the post-melting effect in CdTe as well as the correlation between the melt's superheating and supercooling has been studied by the DTA method. Some additional endothermic effects above the melting point or liquidus temperature were observed in all the investigated melts. A high degree of structural ordering both in the pure and doped melts was concluded. The structure of the molten state is determined by the thermal pre-history of the solid one. The possibility of a high-temperature CdTe polymorphic modification is discussed.

  12. Vibrational properties of homopolar and heteropolar surfaces and interfaces of the CdTe/HgTe system

    International Nuclear Information System (INIS)

    Rey Gonzalez, R.; Camacho B, A.; Quiroga, L.

    1993-08-01

    We present results of calculations for the density of vibrational modes for (001) and (111) homopolar, as well as for (011) heteropolar free surfaces of CdTe and HgTe. A rigid-ion model with a dynamical matrix parametrization including force constants up to second neighbours is used. We report on the existence of highly localized surface resonant modes at the top of the acoustic branch for CdTe and the bottom of the optical branch for HgTe. A different behaviour in the three directions analysed is found. The interface atomic planes show themselves as phonon gapless layers. The contribution of in-plane and out-of-plane vibration is analysed for both the surface and interface cases. (author). 7 refs, 7 figs

  13. Application of the regular associated solution model to the Cd-Te and Hg-Te binary systems

    Science.gov (United States)

    Kelley, J. D.; Martin, B. G.; Szofran, F. R.; Lehoczky, S. L.

    1982-01-01

    The regular associated solution model is used to treat the phase diagrams of the binary II-VI semiconductor alloy systems Hg-Te and Cd-Te. The equations for the species activity coefficients are used without approximations regarding the magnitudes of the various binary interchange energies or the functional dependence on component mol fraction. The values of the four-adjustable parameters required for description of each system are fixed by fitting liquidus data, and the resulting activity coefficients are used to calculate component partial pressures, which are compared with experimental values as an indpendent check of the validity of the model. The results show that the regular associated solution model provides a usefully accurate, but not complete, description for both the Hg-Te and Cd-Te systems. The relationship of this work to previous investigations is discussed.

  14. X ray spectra measurement using a CdTe detector

    International Nuclear Information System (INIS)

    Kurkova, D.; Judas, L.

    2014-01-01

    X ray spectra were measured using a CdTe XR-100T detector (Amptek). Spectra of N series were measured (according to ISO 4037-1:1996): from N60 to N150 for anode voltage of the tube 60-150 kV, realised by x ray tubeIsovolt Titan in dosimetric laboratory SURO, v.v.i.. Two sets of spectra were measured - first without using the tungsten collimator kit of the spectrometer, in a distance of 7 m from x ray tube and low tube current and second using a tungsten collimator kit measured in a distance 1 m from x ray tube focus and low tube current. Elimination of random coincidences was achieved by reduction of counting rates on the detection system. Further artefacts in measured spectra were compensated using an analytic response matrix. Response matrix was computed and subsequently applied in a program made in MATLAB. We demonstrate a function of response matrix on both model physical spectra and measured spectra. In consequence of mainly continuous character of measured spectra more parameters are needed for its description compared to the line spectra. Therefore we came up with additional parameters for characterization and mutual comparison of x ray spectra. (authors)

  15. CdTe detector based PIXE mapping of geological samples

    Energy Technology Data Exchange (ETDEWEB)

    Chaves, P.C., E-mail: cchaves@ctn.ist.utl.pt [Centro de Física Atómica da Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003 Lisboa (Portugal); IST/ITN, Instituto Superior Técnico, Universidade Técnica de Lisboa, Campus Tecnológico e Nuclear, EN10, 2686-953 Sacavém (Portugal); Taborda, A. [Centro de Física Atómica da Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003 Lisboa (Portugal); IST/ITN, Instituto Superior Técnico, Universidade Técnica de Lisboa, Campus Tecnológico e Nuclear, EN10, 2686-953 Sacavém (Portugal); Oliveira, D.P.S. de [Laboratório Nacional de Energia e Geologia (LNEG), Apartado 7586, 2611-901 Alfragide (Portugal); Reis, M.A. [Centro de Física Atómica da Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003 Lisboa (Portugal); IST/ITN, Instituto Superior Técnico, Universidade Técnica de Lisboa, Campus Tecnológico e Nuclear, EN10, 2686-953 Sacavém (Portugal)

    2014-01-01

    A sample collected from a borehole drilled approximately 10 km ESE of Bragança, Trás-os-Montes, was analysed by standard and high energy PIXE at both CTN (previous ITN) PIXE setups. The sample is a fine-grained metapyroxenite grading to coarse-grained in the base with disseminated sulphides and fine veinlets of pyrrhotite and pyrite. Matrix composition was obtained at the standard PIXE setup using a 1.25 MeV H{sup +} beam at three different spots. Medium and high Z elemental concentrations were then determined using the DT2fit and DT2simul codes (Reis et al., 2008, 2013 [1,2]), on the spectra obtained in the High Resolution and High Energy (HRHE)-PIXE setup (Chaves et al., 2013 [3]) by irradiation of the sample with a 3.8 MeV proton beam provided by the CTN 3 MV Tandetron accelerator. In this paper we present results, discuss detection limits of the method and the added value of the use of the CdTe detector in this context.

  16. The X-ray response of CdZnTe

    CERN Document Server

    Owens, A; Andersson, H; Gagliardi, T; Krumrey, M; Nenonen, S; Peacock, A; Taylor, I; Troeger, L

    2002-01-01

    We report the results of a series of X-ray measurements on a 3.1 mm sup 2 , 2.5 mm thick CdZnTe detector carried out at the BESSY II and HASYLAB synchrotron radiation facilities. The detector energy response function was found to be linear over the energy range 2.3-100 keV with an average rms non-linearity of 0.6%, consistent with statistics. At room temperature, under full-area illumination, the FWHM energy resolution was 1.6 keV at 5.9 keV rising to 2.9 keV at 59.54 keV. At a reduced detector temperature of -20 deg. C, these fall to 380 and 818 eV FWHM, respectively. Under pencil beam illumination, the measured energy resolution at 2.5 keV was 360 eV FWHM rising to 1558 eV at 100 keV. By best fitting the expected resolution function to the experimental data, we derive a value for the Fano factor of (0.099+-0.02). Cooling the detector to -50 deg. C, resulted in no noticeable difference in DELTA E above 60 keV, but a 40% reduction at energies <10 keV. At 5.9 keV, the measured resolution under full-area ill...

  17. Can graphene make better HgCdTe infrared detectors?

    Directory of Open Access Journals (Sweden)

    Shi Yanli

    2011-01-01

    Full Text Available Abstract We develop a simple and low-cost technique based on chemical vapor deposition from which large-size graphene films with 5-10 graphene layers can be produced reliably and the graphene films can be transferred easily onto HgCdTe (MCT thin wafers at room temperature. The proposed technique does not cause any thermal and mechanical damages to the MCT wafers. It is found that the averaged light transmittance of the graphene film on MCT thin wafer is about 80% in the mid-infrared bandwidth at room temperature and 77 K. Moreover, we find that the electrical conductance of the graphene film on the MCT substrate is about 25 times larger than that of the MCT substrate at room temperature and 77 K. These experimental findings suggest that, from a physics point of view, graphene can be utilized as transparent electrodes as a replacement for metal electrodes while producing better and cheaper MCT infrared detectors.

  18. CdTe reflection anisotropy line shape fitting

    International Nuclear Information System (INIS)

    Molina-Contreras, J.R.

    2010-01-01

    In this paper, an empirical novel plane-wave time dependent ensemble is introduced to fit the RA, the reflectance (R) and the imaginary part of the dielectric function oscillation measured around the E 1 and E 1 + Δ 1 transition region in II-VI semiconductors. By applying the new plane-wave time dependent ensemble to the measured spectrum for a (0 0 1) oriented CdTe undoped commercial wafer, crystallized in a zinc-blende structure, a very good agreement was found between the measured spectrum and the fitting. In addition to this, the reliability of the plane-wave time dependent ensemble was probed, by comparing the results with the calculated fitting in terms of a Fourier series and in terms of a six-order polynomial fit. Our analysis suggests, that the experimental oscillation in the line shape of the RA cannot be fitted with a Fourier series using harmonics multiples of the number which dominates the measured RA spectra in the argument of the plane-wave ensemble.

  19. Beta decays of 126Cd and 126In to levels in 126In and 126Sn

    International Nuclear Information System (INIS)

    Gartner, M.L.

    1979-01-01

    A study of the beta decays of 126 Cd and 126 In using the TRISTAN on-line isotope separator facility is reported. Gamma-ray singles measurements were made for both decays usng Ge(Li) and LEPS (low energy photon spectrometer) detectors. In addition, gamma--gamma coincidence measurements and gamma multiscale measurements were made for both decays using Ge(Li) detectors. The half-life for 126 Cd was determined to be 0.506 +- 0.015 sec., and the half-lives for the low- and high-spin 126 In isomers were determined to be 1.83 +- 0.11 sec. and 1.96 +- 0.10 sec., respectively. A total of 11 gamma rays were observed in the decay of 126 Cd, and all but one were placed in a level scheme for 126 In. A total of 48 gamma rays were observed in the decay of the low- and high-spin 126 In isomers and all were placed in a level scheme for 126 Sn. Spin and parity assignments were deduced, whenever possible, on the basis of logft values and gamma decay selection rules. The 126 In decay schemes (one has been proposed for each isomer) are compared with earlier decay studies and with results from 124 Sn(t,p) 126 Sn reaction experiments. The systematics associated with the level schemes are discussed and a comparison is made with the nuclear shell model. 49 references

  20. Live-monitoring of Te inclusions laser-induced thermo-diffusion and annealing in CdZnTe crystals

    International Nuclear Information System (INIS)

    Zappettini, A.; Zambelli, N.; Benassi, G.; Calestani, D.; Pavesi, M.

    2014-01-01

    The presence of Te inclusions is one of the main factors limiting performances of CdZnTe crystals as X-ray detectors. We show that by means of infrared laser radiation it is possible to move and anneal tellurium inclusions exploiting a thermo-diffusion mechanism. The process is studied live during irradiation by means of an optical microscope equipment. Experimental conditions, and, in particular, energy laser fluence, for annealing inclusions of different dimensions are determined.

  1. Live-monitoring of Te inclusions laser-induced thermo-diffusion and annealing in CdZnTe crystals

    Energy Technology Data Exchange (ETDEWEB)

    Zappettini, A.; Zambelli, N.; Benassi, G.; Calestani, D. [Istituto Materiali Elettronica e Magnetismo – Consiglio Nazionale delle Ricerche, Parma (Italy); Pavesi, M. [Istituto Materiali Elettronica e Magnetismo – Consiglio Nazionale delle Ricerche, Parma (Italy); Istituto di Fisica e Scienze della Terra, Università degli Studi di Parma, Parma (Italy)

    2014-06-23

    The presence of Te inclusions is one of the main factors limiting performances of CdZnTe crystals as X-ray detectors. We show that by means of infrared laser radiation it is possible to move and anneal tellurium inclusions exploiting a thermo-diffusion mechanism. The process is studied live during irradiation by means of an optical microscope equipment. Experimental conditions, and, in particular, energy laser fluence, for annealing inclusions of different dimensions are determined.

  2. Investigation of semiconductor heterostructures HgTe/HgCdTe under magnetic fields up to 50 T

    Science.gov (United States)

    Platonov, V. V.; Kudasov, Yu B.; Makarov, I. V.; Maslov, D. A.; Surdin, O. M.

    2017-12-01

    Our paper is devoted to a compact economic magnetic facility, which is equipped by a 300 kJ capacitor bank. The facility is designed for the exploration of magnetic and optical substance properties under magnetic fields up to 50 T and under cryogenic temperatures. The cyclotron resonance and quantum Hall effect measurement results are presented for semiconductor heterostructures HgTe/HgCdTe with quantum wells.

  3. Development of Substrate Structure CdTe Photovoltaic Devices with Performance Exceeding 10%: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Dhere, R. G.; Duenow, J. N.; DeHart, C. M.; Li, J. V.; Kuciauskas, D.; Gessert, T. A.

    2012-08-01

    Most work on CdTe-based solar cells has focused on devices with a superstrate structure. This focus is due to the early success of the superstrate structure in producing high-efficiency cells, problems of suitable ohmic contacts for lightly doped CdTe, and the simplicity of the structure for manufacturing. The development of the CdCl2 heat treatment boosted CdTe technology and perpetuated the use of the superstrate structure. However, despite the beneficial attributes of the superstrate structure, devices with a substrate structure are attractive both commercially and scientifically. The substrate structure eliminates the need for transparent superstrates and thus allows the use of flexible metal and possibly plastic substrates. From a scientific perspective, it allows better control in forming the junction and direct access to the junction for detailed analysis. Research on such devices has been limited. The efficiency of these devices has been limited to around 8% due to low open-circuit voltage (Voc) and fill factor. In this paper, we present our recent device development efforts at NREL on substrate-structure CdTe devices. We have found that processing parameters required to fabricate high-efficiency substrate CdTe PV devices differ from those necessary for traditional superstrate CdTe devices. We have worked on a variety of contact materials including Cu-doped ZnTe and CuxTe. We will present a comparative analysis of the performance of these contacts. In addition, we have studied the influence of fabrication parameters on junction properties. We will present an overview of our development work, which has led to CdTe devices with Voc values of more than 860 mV and NREL-confirmed efficiencies approaching 11%.

  4. SEM, EDS, PL and absorbance study of CdTe thin films grown by CSS method

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Torres, M.E.; Silva-Gonzalez, R.; Gracia-Jimenez, J.M. [Instituto de Fisica, BUAP, Apdo. Postal J-48, San Manuel, 72570 Puebla, Pue. (Mexico); Casarrubias-Segura, G. [CIE- UNAM, 62580 Temixco, Morelos (Mexico)

    2006-09-22

    Oxygen-doped CdTe films were grown on conducting glass substrates by the close spaced sublimation (CSS) method and characterized using SEM, EDS, photoluminescence (PL) and absorbance. A significant change in the polycrystalline morphology is observed when the oxygen proportion is increased in the deposition atmosphere. The EDS analysis showed that all samples are nonstoichiometric with excess Te. The PL spectra show emission bands associated with Te vacancies (V{sub Te}), whose intensities decrease as the oxygen proportion in the CSS chamber is increased. The oxygen impurities occupy Te vacancies and modify the surfaces states, improving the nonradiative process. (author)

  5. The synthesis of newly modified CdTe quantum dots and their application for improvement of latent fingerprint detection

    International Nuclear Information System (INIS)

    Gao Feng; Han Jiaxing; Zhang Jun; Liu Zhiliang; Li Qun; Sun Xiufeng; Zheng Jincheng; Bao Liru; Li Xin

    2011-01-01

    Motivated by the urgent demand for the detection of latent fingerprints using fluorescence-based nanotechnology, this work was devoted to developing a simple synthetic approach to obtain positively charged CdTe QDs with enhanced fluorescence and affinity for the improvement of latent fingerprint detection. Through this synthetic method, the positively charged CdTe-COONH 3 NH 3 + QDs were successfully achieved by using hydrazine hydrate as both the surface stabilizer and pH adjuster during the preparation process. In comparison to the negatively charged CdTe-COO - QDs prepared by using sodium hydroxide as the pH adjuster, the CdTe-COONH 3 NH 3 + QDs showed enhanced fluorescence. The effectiveness of CdTe-COO - and CdTe-COONH 3 NH 3 + QDs for detection of latent fingerprints present on a large variety of smooth objects was systematically and comparatively studied. The results indicate that the detection of latent fingerprints by using CdTe-COONH 3 NH 3 + QDs as fluorescent labeling marks was greatly enhanced, and more characteristic finger ridge details were detected and identified due to their enhanced affinity with latent fingerprints, in comparison to the detection by using CdTe-COO - QDs as fluorescent labeling marks. The CdTe-COONH 3 NH 3 + QDs show superior detection capability than the CdTe-COO - QDs, which greatly improves the applicability of CdTe QDs for practical application in latent fingerprint detection.

  6. Effect of In Situ Thermal Annealing on Structural, Optical, and Electrical Properties of CdS/CdTe Thin Film Solar Cells Fabricated by Pulsed Laser Deposition

    Directory of Open Access Journals (Sweden)

    Alaa Ayad Al-mebir

    2016-01-01

    Full Text Available An in situ thermal annealing process (iTAP has been introduced before the common ex situ cadmium chloride (CdCl2 annealing to improve crystal quality and morphology of the CdTe thin films after pulsed laser deposition of CdS/CdTe heterostructures. A strong correlation between the two annealing processes was observed, leading to a profound effect on the performance of CdS/CdTe thin film solar cells. Atomic force microscopy and Raman spectroscopy show that the iTAP in the optimal processing window produces considerable CdTe grain growth and improves the CdTe crystallinity, which results in significantly improved optoelectronic properties and quantum efficiency of the CdS/CdTe solar cells. A power conversion efficiency of up to 7.0% has been obtained on thin film CdS/CdTe solar cells of absorber thickness as small as 0.75 μm processed with the optimal iTAP at 450°C for 10–20 min. This result illustrates the importance of controlling microstructures of CdTe thin films and iTAP provides a viable approach to achieve such a control.

  7. Uncooled middle wavelength infrared photoconductors based on (111) and (100) oriented HgCdTe

    Science.gov (United States)

    Madejczyk, Paweł; Kębłowski, Artur; Gawron, Waldemar; Martyniuk, Piotr; Kopytko, Małgorzata; Stępień, Dawid; Rutkowski, Jarosław; Piotrowski, Józef; Piotrowski, Adam; Rogalski, Antoni

    2017-09-01

    We present progress in metal organic chemical vapor deposition (MOCVD) growth of (100) HgCdTe epilayers achieved recently at the Institute of Applied Physics, Military University of Technology and Vigo System S.A. It is shown that MOCVD technology is an excellent tool for the fabrication of different HgCdTe detector structures with a wide range of composition, donor/acceptor doping, and without post grown ex-situ annealing. Surface morphology, residual background concentration, and acceptor doping efficiency are compared in (111) and (100) oriented HgCdTe epilayers. At elevated temperatures, the carrier lifetime in measured p-type photoresistors is determined by Auger 7 process with about one order of magnitude difference between theoretical and experimental values. Particular progress has been achieved in the growth of (100) HgCdTe epilayers for medium wavelength infrared photoconductors operated in high-operating temperature conditions.

  8. Development of Buffer Layer Technologies for LWIR and VLWIR HgCdTe Integration on Si

    National Research Council Canada - National Science Library

    Golding, Terry D

    2005-01-01

    This program proposed to develop manufacturable, cost-effective buffer layer technologies that would allow either hybrid or monolithic integration of LWIR and VLWIR HgCdTe infrared focal plane arrays...

  9. Ultra-low Noise, High Bandwidth, 1550nm HgCdTe APD, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Voxtel Inc. proposes to optimize the design of a large area, 1.55?m sensitive HgCdTe avalanche photodiode (APD) that achieves high gain with nearly no excess noise....

  10. Properties of CdTe nanocrystalline thin films grown on different substrates by low temperature sputtering

    International Nuclear Information System (INIS)

    Chen Huimin; Guo Fuqiang; Zhang Baohua

    2009-01-01

    CdTe nanocrystalline thin films have been prepared on glass, Si and Al 2 O 3 substrates by radio-frequency magnetron sputtering at liquid nitrogen temperature. The crystal structure and morphology of the films were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The XRD examinations revealed that CdTe films on glass and Si had a better crystal quality and higher preferential orientation along the (111) plane than the Al 2 O 3 . FESEM observations revealed a continuous and dense morphology of CdTe films on glass and Si substrates. Optical properties of nanocrystalline CdTe films deposited on glass substrates for different deposited times were studied.

  11. Determination and characterization of deep levels in p-CdTe(Cl)

    International Nuclear Information System (INIS)

    Hoeschl, P.; Polivka, P.; Prosser, V.; Vanecek, M.; Skrivankova, M.

    1977-01-01

    CdTe single crystals grown from Te solvent have been used for both evaluation of physical parameters and preparation of nuclear radiation detectors. Ingots were doped with Cl(CdCl 2 ) in the range of 100-5000 ppm. For the experimental determination of the distribution of the donor and acceptor levels in CdTe(Cl) the Hall effect, photoconductivity, drift mobilities, thermo-stimulated currents (TSC) and space charge limited currents (SCLC) were employed. The results are compared with a model based on acceptor-donor pairs separated by distinct distance within the crystal lattice. For a typical detector produced from p-CdTe(Cl) the total resolution was approximately 7keV (FWHM) for the 122keV gamma 57 Co and 5keV (FWHM) for 59keV gamma 241 Am

  12. CdTe Quantum Dots Embedded in Multidentate Biopolymer Based on Salep: Characterization and Optical Properties

    Directory of Open Access Journals (Sweden)

    Ghasem Rezanejade Bardajee

    2013-01-01

    Full Text Available This paper describes a novel method for surface modification of water soluble CdTe quantum dots (QDs by using poly(acrylic acid grafted onto salep (salep-g-PAA as a biopolymer. As-prepared CdTe-salep-g-PAA QDs were characterized by Fourier transform infrared (FT-IR spectrum, thermogravimetric (TG analysis, and transmission electron microscopy (TEM. The absorption and fluorescence emission spectra were measured to investigate the effect of salep-g-PAA biopolymer on the optical properties of CdTe QDs. The results showed that the optical properties of CdTe QDs were significantly enhanced by using salep-g-PAA-based biopolymer.

  13. Low-Roughness Plasma Etching of HgCdTe Masked with Patterned Silicon Dioxide

    Science.gov (United States)

    Ye, Z. H.; Hu, W. D.; Yin, W. T.; Huang, J.; Lin, C.; Hu, X. N.; Ding, R. J.; Chen, X. S.; Lu, W.; He, L.

    2011-08-01

    A novel mask technique utilizing patterned silicon dioxide films has been exploited to perform mesa etching for device delineation and electrical isolation of HgCdTe third-generation infrared focal-plane arrays (IRFPAs). High-density silicon dioxide films were deposited at temperature of 80°C, and a procedure for patterning and etching of HgCdTe was developed by standard photolithography and wet chemical etching. Scanning electron microscopy (SEM) showed that the surfaces of inductively coupled plasma (ICP) etched samples were quite clean and smooth. Root-mean-square (RMS) roughness characterized by atomic force microscopy (AFM) was less than 1.5 nm. The etching selectivity between a silicon dioxide film and HgCdTe in the samples masked with patterned silicon dioxide films was greater than 30:1. These results show that the new masking technique is readily available and promising for HgCdTe mesa etching.

  14. The next generation CdTe technology- Substrate foil based solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Ferekides, Chris [Univ. of South Florida, Tampa, FL (United States)

    2017-03-22

    The main objective of this project was the development of one of the most promising Photovoltaic (PV) materials CdTe into a versatile, cost effective, and high throughput technology, by demonstrating substrate devices on foil substrates using high throughput fabrication conditions. The typical CdTe cell is of the superstrate configuration where the solar cell is fabricated on a glass superstrate by the sequential deposition of a TCO, n-type heterojunction partner, p-CdTe absorber, and back contact. Large glass modules are heavy and present significant challenges during manufacturing (uniform heating, etc.). If a substrate CdTe cell could be developed (the main goal of this project) a roll-to-toll high throughput technology could be developed.

  15. FY 1999 research and development of technologies for commercialization of photovoltaic power generation systems. Development of technologies for production of thin-film solar cells and low-cost, large-area modules (Development of technologies for high-reliability CdTe solar cell modules); 1999 nendo taiyoko hatsuden system jitsuyoka gijutsu kaihatsu seika hokokusho. Usumaku taiyo denchi no seizo gijutsu kaihatsu / tei cost daimenseki module seizo gijutsu kaihatsu (koshinraisei CdTe taiyo denchi module no seizo gijutsu kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    The research and development project is implemented for production of low-cost, large-area modules of CdTe solar cells by the high-quality film-making process and high-function patterning, and the FY 1999 results are reported. The research program for the large-area TCO film-making technologies involves investigations on improvement of SnO{sub 2} film quality by the mist method and continuous film-making, which lead to continuous, stable production of 34 substrates of low resistance of 9.7{omega} on the average. The program for production of the large-area, thin-film CdS/CdTe solar cells involves production of TCO and CdS by the mist method, and patterning of the laminated TCO/CdS film by laser scribing. The CdTe film is formed by the atmospheric pressure CSS method, and treated with CdCl{sub 2} to improve its crystallinity. The CdTe film is patterned by sand blasting, and provided with the carbon and silver electrodes by screen printing, to complete the cell. The process is totally effected at the atmospheric pressure, needing no vacuum device. The CdTe solar cell assembly (130 cells connected in series, opening area: 5,413cm{sup 2}), fabricated on a trial basis, achieves a conversion efficiency of 10%. (NEDO)

  16. Solid solution series between CdIn{sub 2}Te{sub 4} and AgInTe{sub 2} investigated by resonant X-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Welzmiller, Simon; Hennersdorf, Felix; Oeckler, Oliver [Faculty of Chemistry and Mineralogy, Leipzig University (Germany); Fitch, Andy [ESRF - The European Synchrotron, Grenoble (France)

    2014-12-15

    AgInTe{sub 2} and CdIn{sub 2}Te{sub 4} exhibit structures related to the chalcopyrite type. They form a solid solution (CdIn{sub 2}Te{sub 4}){sub x}(Ag{sub 2}In{sub 2}Te{sub 4}){sub 1-x} with a miscibility gap for 0.5 < x < 0.95. Such compounds are interesting for the application in solar cells or as thermoelectric materials. Joint refinements of high-resolution synchrotron powder diffraction data for CdIn{sub 2}Te{sub 4}, Ag{sub 0.75}Cd{sub 0.125}InTe{sub 2} (x = 0.25) and Ag{sub 0.6}Cd{sub 0.2}InTe{sub 2} (x = 0.4) measured at the K-absorption edges of Ag, Cd, In, Te and far away from these edges yield unambiguous information on the element and vacancy distribution. In CdIn{sub 2}Te{sub 4}, the vacancies are completely ordered and cadmium and indium are uniformly distributed over both cation positions. Ag{sub 0.75}Cd{sub 0.125}InTe{sub 2} and Ag{sub 0.6}Cd{sub 0.2}InTe{sub 2}, which represent different Cd contents associated with different vacancy concentrations, exhibit disordered chalcopyrite-type structures. The vacancies concentrate on the Ag position of AgInTe{sub 2} with additional Ag, Cd and little In, whereas the In position remains predominantly occupied by In, little Ag, and almost no Cd. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Investigations of portable cadmium telluride (CdTe(Cl)) detectors for clinical studies with radioactive indicators

    International Nuclear Information System (INIS)

    Bojsen, J.

    1985-01-01

    The combination of small, portable γ-radiation-sensitive Cadmium Telluride (CdTE(Cl)) crystal detectors and portable solid state data storage memories makes it feasible to extend the measuring period in a number of clinical investigations based on the use of various radioisotopes and external detection. Blood sampling can be avoided in some cases. Continuous ambulatory monitoring of relevant physiological parameters is practicable, e.g. kidney function (GFR), left ventricular ejection fraction, subcutaneous blood flow, muscle blood flow and insulin absorption in diabetic patients. In the present methodological study the applicability of the 133-Xe washout technique to subcutaneous (s.c.) adipose tissue blood flow (SBF) has been investigated and adapted to the use of CdTe(Cl) detectors attached to the skin surface for the measurement of local 133-Xe-disappearance rate constants (k). Physical characterization of CdTe(Cl) detectors as γ-sensitive devices has been performed, and adequate counting sensitivities were found without detector energy-resolution properties. The CdTe(Cl) detectors are therefore suitable for single indicator studies. The measuring geometry of CdTe(Cl) detectors was studied and compared with that of stationary Sodium Iodide (NaI(Tl)) detectors in both phantom and in vivo investigations. The spatial properties of CdTe(Cl) detectors could to some extent be adjusted by pulse height discrimination and lead collimation. When long-term measurements were complicated by for instance physical activity of the patients, the small CdTe(Cl) detectors in general showed equal or better performance than the heavy and voluminous NaI(Tl) detectors. The free movement of the ambulatory patient and the avoidance of cable connections to stationary data-collecting systems gave improved possibilities for measurements of the relevant parameters. From this point of view, portable CdTe(Cl) detectors must be considered an important advance for radioactivity studies in

  18. High-resolution CdTe detectors with application to various fields (Conference Presentation)

    Science.gov (United States)

    Takeda, Shin'ichiro; Orita, Tadashi; Arai, Yasuo; Sugawara, Hirotaka; Tomaru, Ryota; Katsuragawa, Miho; Sato, Goro; Watanabe, Shin; Ikeda, Hirokazu; Takahashi, Tadayuki; Furenlid, Lars R.; Barber, H. Bradford

    2016-10-01

    High-quality CdTe semiconductor detectors with both fine position resolution and high energy resolution hold great promise to improve measurement in various hard X-ray and gamma-ray imaging fields. ISAS/JAXA has been developing CdTe imaging detectors to meet scientific demands in latest celestial observation and severe environmental limitation (power consumption, vibration, radiation) in space for over 15 years. The energy resolution of imaging detectors with a CdTe Schottky diode of In/CdTe/Pt or Al/CdTe/Pt contact is a highlight of our development. We can extremely reduce a leakage current of devises, meaning it allows us to supply higher bias voltage to collect charges. The 3.2cm-wide and 0.75mm-thick CdTe double-sided strip detector with a strip pitch of 250 µm has been successfully established and was mounted in the latest Japanese X-ray satellite. The energy resolution measured in the test on ground was 2.1 keV (FWHM) at 59.5 keV. The detector with much finer resolution of 60 µm is ready, and it was actually used in the FOXSI rocket mission to observe hard X-ray from the sun. In this talk, we will focus on our research activities to apply space sensor technologies to such various imaging fields as medical imaging. Recent development of CdTe detectors, imaging module with pinhole and coded-mask collimators, and experimental study of response to hard X-rays and gamma-rays are presented. The talk also includes research of the Compton camera which has a configuration of accumulated Si and CdTe imaging detectors.

  19. Recent Developments of Flexible CdTe Solar Cells on Metallic Substrates: Issues and Prospects

    OpenAIRE

    M. M. Aliyu; M. A. Islam; N. R. Hamzah; M. R. Karim; M. A. Matin; K. Sopian; N. Amin

    2012-01-01

    This study investigates the key issues in the fabrication of CdTe solar cells on metallic substrates, their trends, and characteristics as well as effects on solar cell performance. Previous research works are reviewed while the successes, potentials, and problems of such technology are highlighted. Flexible solar cells offer several advantages in terms of production, cost, and application over glass-based types. Of all the metals studied as substrates for CdTe solar cells, molybdenum appears...

  20. Degradation processes occur on the CdTe thin films solar elements

    CERN Document Server

    Mirsagatov, S A; Makhmudov, M; Muzapharova, S A

    1999-01-01

    It is shown the Cu in CdTe polycristalline films is diffusing on the complex mechanism. By bringing of W atoms in thin CdTe layers it is possible to operate diffusion's speed of Cu atoms. Initiation of the (Cu sup + W sub C sub d sup -) complexes under the conditions N(W sub C sub d sup -)>=N(Cu sub i sup +) hardly reduce the diffusion velocity of Cu atoms.

  1. Extended defects in MBE-grown CdTe-based solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Wichrowska, Karolina; Wosinski, Tadeusz; Kret, Slawomir; Chusnutdinow, Sergij; Karczewski, Grzegorz [Institute of Physics, Polish Academy of Sciences, Warsaw (Poland); Rawski, Michal [Analytical Laboratory, Maria Curie-Sklodowska University, Lublin (Poland); Yastrubchak, Oksana [Institute of Physics, Maria Curie-Sklodowska University, Lublin (Poland)

    2015-08-15

    Extended defects in the p -ZnTe/n -CdTe heterojunctions grown by the molecular-beam epitaxy technique on two different substrates, GaAs and CdTe, have been investigated by deep-level transient spectroscopy (DLTS) and transmission electron microscopy (TEM). Four hole traps, called H1 to H4, and one electron trap, called E3, have been revealed in the DLTS spectra measured for the heterojunctions grown on the GaAs substrates. The H1, H3, H4 and E3 traps have been attributed to the electronic states of dislocations on the ground of their logarithmic capture kinetics. The DLTS peaks associated with the H1 and E3 traps were not observed in the DLTS spectra measured for the heterojunction grown on the CdTe substrate. They are most likely associated with threading dislocations generated at the mismatched interface with the GaAs substrate. Cross-sectional TEM images point out that they are dislocations of the 60 -type. In both the types of heterojunctions the H4 trap was observed only under forward-bias filling pulse, suggesting that this trap is associated with the CdTe/ZnTe interface. In addition, TEM images revealed also the presence of intrinsic and extrinsic stacking faults in the CdTe layers, which may considerably affect their electronic properties. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Recent progress in MOCVD growth for thermoelectrically cooled HgCdTe medium wavelength infrared photodetectors

    Science.gov (United States)

    Gawron, W.; Martyniuk, P.; Kębłowski, A.; Kolwas, K.; Stępień, D.; Piotrowski, J.; Madejczyk, P.; Pędzińska, M.; Rogalski, A.

    2016-04-01

    The authors report on advanced metalorganic chemical vapour deposition (MOCVD) of Hg1-xCdxTe (HgCdTe) structures for high operating temperature, medium wavelength infrared (MWIR) detector application. MOCVD technology with wide range of composition and donor/acceptor doping and without post grown annealing was proved to be an excellent tool for HgCdTe heterostructure epitaxial growth used for uncooled photodetector design. The interdiffused multilayer process (IMP) technique was applied for the HgCdTe deposition. HgCdTe epilayers were grown at 350 °C with Hg source kept at 210 °C. The II/VI mole ratio was assumed in the range from 1.5 to 3 during CdTe/HgTe cycles of the IMP process. The MWIR detectors grown by MOCVD exhibit detectivity ∼7.3 × 1011 Jones at λPEAK = 3.5 μm and T = 230 K being determined by background limited photodetector (BLIP) condition.

  3. [The impact of ZnS/CdS composite window layer on the quantun efficiency of CdTe solar cell in short wavelength].

    Science.gov (United States)

    Zhang, Li-xiang; Feng, Liang-huan; Wang, Wen-wu; Xu, Hang; Wu, Li-li; Zhang, Jing-quan; Li, Wei; Zeng, Guang-gen

    2015-02-01

    ZnS/CdS composite window layer was prepared by magnetron sputtering method and then applied to CdTe solar cell. The morphology and structure of films were measured. The data of I-V in light and the quantum efficiency of CdTe solar cells with different window layers were also measured. The effect of ZnS films prepared in different conditions on the performance of CdTe solar cells was researched. The effects of both CdS thickness and ZnS/CdS composite layer on the transmission in short wavelength were studied. Particularly, the quantum efficiency of CdTe solar cells with ZnS/CdS window layer was measured. The results show as follows. With the thickness of CdS window layer reducing from 100 to 50 nm, the transmission increase 18.3% averagely in short wavelength and the quantum efficiency of CdTe solar cells increase 27.6% averagely. The grain size of ZnS prepared in 250 degrees C is smaller than prepared at room temperature. The performance of CdTe solar cells with ZnS/CdS window layer is much better if ZnS deposited at 250 degrees C. This indicates grain size has some effect on the electron transportation. When the CdS holds the same thickness, the transmission of ZnS/CdS window layer was improved about 2% in short wavelength compared with CdS window layer. The quantum efficiency of CdTe solar cells with ZnS/CdS window layer was also improved about 2% in short wavelength compared with that based on CdS window layer. These indicate ZnS/CdS composite window layer can increase the photon transmission in short wavelength so that more photons can be absorbed by the absorbent layer of CdTe solar cells.

  4. Comparison of CdS films deposited by different techniques: Effects on CdTe solar cell

    International Nuclear Information System (INIS)

    Lee, Jaehyeong

    2005-01-01

    Polycrystalline cadmium sulfide (CdS) thin-films were deposited on glass substrate by chemical bath deposition (CBD) and vacuum evaporation (VE) techniques. VE-CdS films consisted primarily of hexagonal phase, whereas CBD CdS films containing primarily the cubic form. VE-grown films were shown to have better crystallinity than CBD-grown films. The grain size of the CBD films is smaller than the ones of VE films. VE-CdS films exhibited relatively high transmittance in the above-gap region and band gap compared with CBD films. However, CdTe solar cells with these low quality CBD-CdS layers yield higher and more stable characteristics. Current-voltage-temperature measurements showed that the current transport for both cells was controlled by both tunneling and interface recombination but the cells with CBD-CdS displayed less tunneling

  5. Study of CdTe:Cl and CdZnTe detectors for medical multi-slices X-ray Computed Tomography; Etude de detecteurs en CdTe:Cl et CdZnTe pour la tomographie X medicale multicoupes

    Energy Technology Data Exchange (ETDEWEB)

    Ricq, St

    1999-09-28

    The application of CdTe and CdZnTe detectors to medical X-ray Computed Tomography have been investigated. Different electrodes (Au, Pt, In) have been deposited on CdZnTe HPBM and on CdTe:ClTHM. Their injection properties have been determined with Current-Voltage characteristics. Under X-ray in CT conditions, injection currents measurements reveal trapped carriers space-charges formation. The same way, the comparisons of the responses to X-beam cut-off with various injection possibilities enable to follow the space-charges evolutions and then to determine the predominant traps types. Nevertheless, both hole and electron traps are responsible for the memory effect e.g. the currents levels dependence with irradiation history. This effect is noticed in particular on responses to fast flux variations that simulate scanner's conditions. Trap levels probably corresponding to native defects are responsible for these limitations. In order to make such detectors suitable for X-ray Computed Tomography, significant progresses in CdTe for CdZnTe crystal growth with an important defects densities reduction (factor 10), or possibly counting mode operation, seem necessary. (author)

  6. Radiative recombination mechanisms in CdTe thin films deposited by elemental vapor transport

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Shamara [Department of Electrical Engineering, University of South Florida, 4202 East Fowler Ave, Tampa, FL 33620 (United States); Vatavu, Sergiu, E-mail: svatavu@usm.md [Department of Electrical Engineering, University of South Florida, 4202 East Fowler Ave, Tampa, FL 33620 (United States); Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., Chisinau, MD-2009, Republic of Moldova (Moldova, Republic of); Evani, Vamsi; Khan, Md; Bakhshi, Sara; Palekis, Vasilios [Department of Electrical Engineering, University of South Florida, 4202 East Fowler Ave, Tampa, FL 33620 (United States); Rotaru, Corneliu [Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., Chisinau, MD-2009, Republic of Moldova (Moldova, Republic of); Ferekides, Chris [Department of Electrical Engineering, University of South Florida, 4202 East Fowler Ave, Tampa, FL 33620 (United States)

    2015-05-01

    A photoluminesence (PL) study of the radiative recombination mechanisms for CdTe films deposited under different Cd and Te overpressure by elemental vapor transport is presented. The experiment and analysis have been carried out in the temperature range of 12-130 K. The intensity of the PL laser excitation beam was varied by two orders of magnitude. It has been established that the bands in the 1.47-1.50 eV are determined by transitions involving shallow D and A states and the 1.36x-1.37x eV band is due to band to level transitions. Deep transitions at 1.042 eV and 1.129 eV are due to radiative transitions to levels determined by CdTe native defects. - Highlights: • Photoluminescense (PL) of CdTe thin films is present in the 0.8-1.6 eV spectral region. • High intensity excitonic peaks are among the main radiative paths. • Radiative transitions at 1.36x eV are assisted by dislocations caused levels. • Extremal Cd/Te overpressure ratios enhance PL for 1.497 eV, 1.486 eV, 1.474 eV bands. • PL intensity reaches its max value for the 0.45 and 1.25 Cd/Te overpressure ratios.

  7. Temperature dependence of the Faraday rotation for CdMnCoTe films

    International Nuclear Information System (INIS)

    Ahn, J. Y.; Tanaka, M.; Imamura, M.

    2001-01-01

    The temperature dependence of magneto-optical property in the visible wavelength region has been studied on four-element semimagnetic semiconductor CdMnCoTe films deposited on quartz glass substrates by using MBE equipment. A large dispersion of Faraday rotation was observed, and the peak of the Faraday rotation was shifted to the higher photon energies with increasing Mn concentration at low temperatures. At 180 K, the value of the Faraday rotation observed for the Cd 0.647 Mn 0.34 Co 0.013 Te film on quartz glass was -0.36 deg/cmG at 630 nm. It is equivalent to the value of -0.36 deg/cmG observed at 77 K for the Cd 0.52 Mn 0.48 Te film on quartz glass. At 77 K, the Faraday rotation observed for the Cd 0.647 Mn 0.34 Co 0.013 Te film on quartz glass was -0.49 deg/cmG at 610 nm. The value is approximately two times larger than that of the Cd 0.52 Mn 0.48 Te film deposited on the same quartz glass substrate. The origin of the enhancement of Faraday rotation in CdMnCoTe films has been discussed in terms of the magnetic susceptibility χ. [copyright] 2001 American Institute of Physics

  8. Distributed Bragg reflectors obtained by combining Se and Te compounds: Influence on the luminescence from CdTe quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Rousset, J.-G., E-mail: j-g.rousset@fuw.edu.pl; Kobak, J.; Janik, E.; Slupinski, T.; Golnik, A.; Kossacki, P.; Nawrocki, M.; Pacuski, W. [Faculty of Physics, Institute of Experimental Physics, University of Warsaw, ul. Pasteura 5, PL-02-093 Warszawa (Poland); Parlinska-Wojtan, M. [Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Krakow (Poland)

    2016-05-14

    We report on the optical properties of structures containing self assembled CdTe quantum dots (QDs) combined with Te and Se based distributed Bragg reflectors either in a half cavity geometry with a relatively broad cavity mode or in a full cavity geometry where the cavity mode is much narrower. We show that for both structures the extraction coefficient of the light emitted from the QDs ensemble is enhanced by more than one order of magnitude with respect to the QDs grown on a ZnTe buffer. However, a single QD line broadening is observed and attributed to an unintentional incorporation of Se in the vicinity of the CdTe QDs. We show that postponing the QDs growth for 24 h after the distributed Bragg reflector deposition allows recovering sharp emission lines from individual QDs. This two step growth method is proven to be efficient also for the structures with CdTe QDs containing a single Mn{sup 2+} ion.

  9. Optical Parameters of Spray-Deposited CdS1- y Te y Thin Films

    Science.gov (United States)

    Ikhmayies, Shadia J.

    2017-02-01

    CdS x Te1- x and CdS1- y Te y solid solutions are usually formed in the interfacial region in CdS/CdTe solar cells during the deposition of the CdTe layer and/or the processing steps of the device. In this work, indium-doped CdS1- y Te y thin films were prepared by first producing CdS:In thin films by the spray pyrolysis technique on glass substrates, then annealing the films in nitrogen atmosphere in the presence of elemental tellurium. The films were characterized by scanning electron microscopy, energy dispersive x-ray spectroscopy, and transmittance measurements. The transmittance was used to deduce the reflectance from which the optical parameters were computed. The extinction coefficient, refractive index, the real and imaginary parts of the dielectric constant, optical conductivity, and energy loss were computed, and their dependence on the composition was investigated. In addition, the dispersion of the refractive index was analyzed by the single oscillator model, and dispersion parameters were investigated.

  10. Vapor CdCl2-Optimization and Screening Experiments for an All Dry Chloride Treatment of CdS/CdTe Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Mahathongdy, Y.; Wolden, C. A.; Baldwin, R. M. (Colorado School of Mines, Golden, CO); Albin, D. S. (National Renewable Energy Laboratory)

    1998-10-01

    A dry vapor treatment of CdCl2 is being developed as an alternative approach to the conventional solution CdCl2 treatment of CdS/CdTe devices. In this alternative process, the CdS/CdTe substrates are vapor treated in a close-spaced sublimation configuration. A 16-run Plackett-Burman screening experiment identified source temperature, substrate temperature, and treatment time as being the most significant parameters in the process. Subsequently, a 20-run Central Composite Design showed that a source temperature of 380-390 C, a temperature gradient (DT) of 5 C, and a time of 10 minutes provides the most process tolerant combination, yielding a total-area efficiency of 12.6%. A strong interaction between DT and treatment time was also identified. The model indicated that for a small DT, device performance improved with decreasing time, whereas at larger values of DT, performance increased with increasing time.

  11. Effects of surface preparation on the properties of metal/CdTe junctions

    International Nuclear Information System (INIS)

    Werthen, J.G.; Haering, J.; Fahrenbruch, A.L.; Bube, R.H.

    1983-01-01

    The effects of surface preparation on the properties of single crystal CdTe junctions have been investigated through characterization of metal/CdTe junctions. Oriented surfaces include air-cleaved (110) surfaces, bromine-in-methanol etched (110) and (111) surfaces, and bromine-in-methanol etched surfaces subjected to a hydrogen heat treatment. Surface photovoltage measurements of the surfaces indicate larger band bending on the etched surfaces than on the cleaved and heat treated surfaces. X-ray photoelectron spectroscopy analysis verifies that excess Te remains after bromine-in-methanol etching and that cleaving leaves a stoichiometric surface. Hydrogen heat treatment of an etched CdTe surface restores a stoichiometric cleaved-like surface from that altered by the etching process. The barrier height for metal/CdTe junctions formed on cleaved surfaces depends on metal work function and reaches 0.99 V in an Al/CdTe junction and 0.87 V in a Cr/CdTe junction. Junctions formed with different metals on etched (110) surfaces result in barrier heights of 0.55--0.65 V with no dependence of the barrier height on the metal work function being observed, due to the presence of an etch-induced layer that partially governs the properties the surface. Heat treatment of an etched surface results in metal/CdTe junctions with characteristics similar to those of junctions formed on cleaved surfaces, and dependence of barrier height on metal work function is again observed, indicating the removal of an etch-induced layer by the heat treatment and the production of a junction similar to that on the cleaved surface

  12. Development of Combinatorial Pulsed Laser Deposition for Expedited Device Optimization in CdTe/CdS Thin-Film Solar Cells

    Directory of Open Access Journals (Sweden)

    Ali Kadhim

    2016-01-01

    Full Text Available A combinatorial pulsed laser deposition system was developed by integrating a computer controlled scanning sample stage in order to rapidly screen processing conditions relevant to CdTe/CdS thin-film solar cells. Using this system, the thickness of the CdTe absorber layer is varied across a single sample from 1.5 μm to 0.75 μm. The effects of thickness on CdTe grain morphology, crystal orientation, and cell efficiency were investigated with respect to different postprocessing conditions. It is shown that the thinner CdTe layer of 0.75 μm obtained the best power conversion efficiency up to 5.3%. The results of this work shows the importance that CdTe grain size/morphology relative to CdTe thickness has on device performance and quantitatively exhibits what those values should be to obtain efficient thin-film CdTe/CdS solar cells fabricated with pulsed laser deposition. Further development of this combinatorial approach could enable high-throughput exploration and optimization of CdTe/CdS solar cells.

  13. Very high resolution detection of gamma radiation at room-temperature using P-I-N detectors of CdZnTe and HgCdTe

    Science.gov (United States)

    Hamilton, W. J.; Rhiger, D. R.; Sen, S.; Kalisher, M. H.; James, K.; Reid, C. P.; Gerrish, V.; Baccash, C. O.

    1994-08-01

    High-energy photon detectors have been constructed by engineering and fabricating p-i-n diode structures consisting of bulk CdZnTe and epitaxial HgCdTe. The p-i-n structure was obtained by liquid-phase epitaxial growth of p and n doped HgCdTe layers on 'intrinsic' CdZnTe material about 1mm thick and approximately 25mm square. Curve tracing shows I-V curves with diode characteristics having resistivity above 1011 Omega -cm and leakage current of less than 400 pA to about - 60V reverse bias on a typical test piece approximately 5 x 8 x 1 mm. Spectra of similar test pieces have been obtained at room temperature with various nuclear isotopic sources over the range of 22 keV to 662 keV which show exceptionally high energy resolution. Resolution as good as 1.82% FWHM was obtained for the 356 keV line of 133Ba with a P/V = 3.4. The performance of these detectors combined with contemporary infrared technology capable of fabricating 2D arrays of these II-VI materials opens up manifold exciting applications in astrophysics, medical, industrial, environmental, and defense spectroscopy and imaging.

  14. Three-dimensional defects in CdTe films obtained by pulsed laser deposition

    NARCIS (Netherlands)

    Sagan, P; Virt, IS; Zawislak, J; Rudyj, IO; Kuzma, M

    2004-01-01

    The quality of Cd chalcodenides epitaxial films can be enhanced seriously by applying a pulsed (electron beam or laser beam) method for ablation of targets. The structure of laser deposited CdTe layers was investigated by transmission high energy electron diffraction. This method is very useful for

  15. Current–voltage characteristics of Ag, Al, Ni–(n)CdTe junctions

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Schottky barriers of Ag, Al, Ni–(n)CdTe structures have been prepared and studied. The films were prepared by rf sputtering and doped with Cd metal. Diode ideality factor of these junctions are greater than unity and barrier height varies from 0⋅6–0⋅7 eV and are affected by room illumination. Photovoltaic effect of.

  16. In-situ CdCl{sub 2}-treated CdTe film surface analysis by X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Vamsi Krishna, K.; Dutta, V. [Centre for Energy Studies, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 100 016 (India)

    2004-07-01

    CdTe thin films are deposited using a spray pyrolysis technique without and with in-situ CdCl{sub 2} treatment. An X-ray photoelectron spectroscopy technique is used to study the Cd, Te, O and Cl chemical environments and the valence-band spectra of the CdTe film surface. A shift in the Fermi-level position of {proportional_to}200 meV towards the valence-band maximum is observed in the CdTe film after the in-situ CdCl{sub 2} treatment, which is attributed to the increment of the Cl concentration and the improvement in the grain growth of the CdTe film. In addition to the increment of the Cl concentration, less surface oxidation is observed compared to that for ex-situ treatment. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Microstructural, optical and electrical properties of Cl-doped CdTe single crystals

    Directory of Open Access Journals (Sweden)

    Choi Hyojeong

    2016-09-01

    Full Text Available Microstructural, optical and electrical properties of Cl-doped CdTe crystals grown by the low pressure Bridgman (LPB method were investigated for four different doping concentrations (unintentionally doped, 4.97 × 1019 cm−3, 9.94 × 1019 cm−3 and 1.99 × 1020 cm−3 and three different locations within the ingots (namely, samples from top, middle and bottom positions in the order of the distance from the tip of the ingot. It was shown that Cl dopant suppressed the unwanted secondary (5 1 1 crystalline orientation. Also, the average size and surface coverage of Te inclusions decreased with an increase in Cl doping concentration. Spectroscopic ellipsometry measurements showed that the optical quality of the Cl-doped CdTe single crystals was enhanced. The resistivity of the CdTe sample doped with Cl at the 1.99 × 1020 cm−3 was above 1010 Ω.cm.

  18. Production of CdTe Semiconductor Thin Films by Electrodeposition Technique for Solar Cell Applications

    Directory of Open Access Journals (Sweden)

    Ahmet PEKSÖZ

    2016-08-01

    Full Text Available Electro-deposited cadmium tellurite (CuTe thin film was grown onto ITO-coated glass substrate for 120 seconds at the room temperature and a constant cathodic potential of -0.85 V. Deposition solution was prepared from cadmium chloride (CdCl2, sodium tellurite (Na2TeO3 and pure water. The pH value of the deposition solution was adjusted to 2.0 by adding HCl. The EDX analysis shows that the film has 52% Cd and 48% Te elemental compositions. Film thickness was found to be 140 nm. The CdTe thin film exhibits p-type semiconductor character, and has an energy bandgap of 1.47 eV. 

  19. Novel patterning of CdS / CdTe thin film with back contacts for photovoltaic application

    Science.gov (United States)

    Ilango, Murugaiya Sridar; Ramasesha, Sheela K.

    2018-04-01

    The heterostructure of patterned CdS / CdTe thin films with back contact have been devised with electron beam lithography and fabricated using sputter deposition technique. The metallic contacts for n-CdS and p-CdTe are patterned such that both are placed at the bottom of the cell. This avoids losses due to contact shading and increases absorption in the window layer. Patterning of the device surface helps in increasing the junction area which can modulate the absorption of more number of photons due to total internal reflection. Computing the surface area between a planar and a patterned device has revealed 133% increase in the junction area. The physical and optical properties of the sputter-deposited CdS / CdTe layers are also presented. J- V characteristics of the solar cell showed the fill factor to be 25.9%, open circuit voltage to be 17 mV and short-circuit current density to be 113.68 A/m2. The increase in surface area is directly related to the increase in the short circuit current of the photovoltaic cell, which is observed from the results of simulated model in Atlas / Silvaco.

  20. T-x-y diagrams for reciprocal systems PbX + CdI2 = CdX + PbI2 (X=S, Se, Te)

    International Nuclear Information System (INIS)

    Odin, I.N.

    2001-01-01

    The present research is undertaken in search of the new complex phases with interesting physical properties. The synthesized samples was analyzed by differential thermal, X-ray diffraction and microstructural methods. The diagonal cross-section CdTe - PbI 2 of the mutual PbTe + CdI 2 = CdTe + PbI 2 system is stable. The T-x phase diagram of the CdTe - PbI 2 system possess eutectic type, the coordinates of eutectic point is 657 ± 2 K, 15 ± 1 mol. % of CdTe. The lead iodide based solid solutions with the mixed structure and the CdTe based solid solutions take place in the equilibria. Solid CdTe dissolves 0.2 mol. % PbI 2 . The fields of the primary crystallization of the CdTe, Pb 1-x Cd x I 2 , PbTe based solid solutions are on the liquidus surface [ru

  1. Timing performance of pixellated CdZnTe detectors

    International Nuclear Information System (INIS)

    Amrami, R.; Shami, G.; Hefetz, Y.; Pansky, A.; Wainer, N.

    1999-01-01

    Recently introduced nuclear medicine cameras in which Positron Emission Tomography (PET) and the traditional Single Photon Emission Computerized Tomography (SPECT), are combined opened new horizon for the nuclear medicine field These systems applying NaI(Tl) scintillation detectors we very well tested and mailable for some time in the medical imaging field However the traditional NaI(Tl) cameras, optimized for low energy radiation imaging, suffer some severe limitations. The relatively low density (3.67 g/cm 2 ) of NaI(Tl) limits the sensitivity. By incarcerating the NaI(Tl) thickness, the spatial resolution decreases. The long decay time (230 nsec) of the light emitted in NaI(Tl) restricts the the use of coincidence technique , as well as the count rate. In recent years CdZn Te (CZT) detectors are studied for the purpose of SPECT nuclear medical radiation imaging in the form of pixellated and microstrip detectors. CZT detector can served as a good candidate for replacing NaI(Tl) for PET and SPECT imaging due to their relatively high stopping power (density = (6.0 g/im 3 , high Z(48, 30, 52)) and their high count rate capability. Unfortunately there are several difficulties in PET application due to the difficulty in manufacturing thick crystals, registration of the full energy deposited in several pixels and their timing capabilities. The latter is due to large ballistic signal variation induced. This variations caused by the pulse shape, which is composed of two main components, the electron and the hole. The electrons travel about ten times faster than the holes. A photon absorbed clear the cathode plane will cause a large and fast signal induced by the electron and a small and slow signal induced due to the holes. Photons absorbed near the anode plane will induce the opposite signals. The distribution of photon absorption depth in the crystal causes signal splits over a number of pixels, due to the well-known 'small pixel effect'. The different pulses slope

  2. Reduction of Fermi level pinning and recombination at polycrystalline CdTe surfaces by laser irradiation

    Science.gov (United States)

    Simonds, Brian J.; Kheraj, Vipul; Palekis, Vasilios; Ferekides, Christos; Scarpulla, Michael A.

    2015-06-01

    Laser processing of polycrystalline CdTe is a promising approach that could potentially increase module manufacturing throughput while reducing capital expenditure costs. For these benefits to be realized, the basic effects of laser irradiation on CdTe must be ascertained. In this study, we utilize surface photovoltage spectroscopy (SPS) to investigate the changes to the electronic properties of the surface of polycrystalline CdTe solar cell stacks induced by continuous-wave laser annealing. The experimental data explained within a model consisting of two space charge regions, one at the CdTe/air interface and one at the CdTe/CdS junction, are used to interpret our SPS results. The frequency dependence and phase spectra of the SPS signal are also discussed. To support the SPS findings, low-temperature spectrally-resolved photoluminescence and time-resolved photoluminescence were also measured. The data show that a modest laser treatment of 250 W/cm2 with a dwell time of 20 s is sufficient to reduce the effects of Fermi level pinning at the surface due to surface defects.

  3. Reduction of Fermi level pinning and recombination at polycrystalline CdTe surfaces by laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Simonds, Brian J. [Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah 84112 (United States); Kheraj, Vipul [Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah 84112 (United States); Department of Applied Physics, S. V. National Institute of Technology, Surat 395 007 (India); Palekis, Vasilios; Ferekides, Christos [Electrical Engineering, University of South Florida, Tampa, Florida 33620 (United States); Scarpulla, Michael A., E-mail: scarpulla@eng.utah.edu [Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah 84112 (United States); Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112 (United States)

    2015-06-14

    Laser processing of polycrystalline CdTe is a promising approach that could potentially increase module manufacturing throughput while reducing capital expenditure costs. For these benefits to be realized, the basic effects of laser irradiation on CdTe must be ascertained. In this study, we utilize surface photovoltage spectroscopy (SPS) to investigate the changes to the electronic properties of the surface of polycrystalline CdTe solar cell stacks induced by continuous-wave laser annealing. The experimental data explained within a model consisting of two space charge regions, one at the CdTe/air interface and one at the CdTe/CdS junction, are used to interpret our SPS results. The frequency dependence and phase spectra of the SPS signal are also discussed. To support the SPS findings, low-temperature spectrally-resolved photoluminescence and time-resolved photoluminescence were also measured. The data show that a modest laser treatment of 250 W/cm{sup 2} with a dwell time of 20 s is sufficient to reduce the effects of Fermi level pinning at the surface due to surface defects.

  4. Directional solidification of filamentary shapes of Pb--Cd and Pb--Sn eutectic alloys

    International Nuclear Information System (INIS)

    Dhindaw, B.K.; Verhoeven, J.D.; Spencer, C.R.; Gibson, E.D.

    1978-01-01

    Eutectic alloys of Pb--Cd and Pb--Sn were directionally solidified as thin filamentary strips contained in stainless steel and quartz capillaries. As the solidification rate increased the filament width, w, had to be reduced to maintain complete alignment of the lamellae clear across the filament. It was determined that in order to achieve complete alignment the ratio of filament width to lamellar spacing, w/lambda had to be less than about 30. Experiments were carried out at rates of 2-400 μm/s and at temperature gradients of 130 and 320 0 C/cm

  5. Spectroscopic, topological, and electronic characterization of ultrathin a-CdTe:O tunnel barriers

    International Nuclear Information System (INIS)

    Dolog, Ivan; Mallik, Robert R.; Malz, Dan; Mozynski, Anthony

    2004-01-01

    Ultrathin oxygenated amorphous CdTe (a-CdTe:O) films are prepared by rf sputtering of CdTe in a background of argon or argon/nitrogen/oxygen mixtures. Atomic force microscopy (AFM) is used to characterize the films and shows that they have an island structure typical of most sputtered thin films. However, when sufficiently low powers and deposition rates are employed during sputtering, the resulting films are remarkably smooth and sufficiently thin for use as barrier layers in inelastic electron tunneling (IET) junctions. Four terminal current-voltage data are recorded for Al/a-CdTe:O/Pb tunnel junctions and conductance-voltage curves are derived numerically. WKB fits to the conductance-voltage curves are obtained using a two-component trapezoidal plus square (TRAPSQR) model barrier potential to determine values for the tunnel barrier parameters (height, shape, and width); these parameters are consistent with AFM topological measurements and values from similar devices reported in the literature. IET spectra are presented which confirm that electrons tunnel through ultrathin regions of the a-CdTe:O films, which contain aluminum oxide subregions in a manner consistent with the TRAPSQR barrier model. Because tunneling occurs predominantly through these ultrathin regions, IET spectroscopic data obtained are representative of states at, or within a few tenths of nanometers from, the surface and confirm that the a-CdTe:O surface stoichiometry is very sensitive to changes in the argon/oxygen/nitrogen concentration ratios during film growth. Full IET spectra, current-voltage, and conductance-voltage data are presented together with tunnel barrier parameters derived from (WKB) fits to the data. The results presented here indicate that inelastic electron tunneling spectroscopy is a useful tool for characterizing the surface states of a-CdTe:O and possibly other photovoltaic materials

  6. A renewed search for short-lived 126Sn in the early Solar System: Hydride generation MC-ICPMS for high sensitivity Te isotopic analysis

    Science.gov (United States)

    Brennecka, Gregory A.; Borg, Lars E.; Romaniello, Stephen J.; Souders, Amanda K.; Shollenberger, Quinn R.; Marks, Naomi E.; Wadhwa, Meenakshi

    2017-03-01

    Although there is limited direct evidence for supernova input into the nascent Solar System, many models suggest it formed by the gravitational collapse of a molecular cloud that was triggered by a nearby supernova. Existing lines of evidence, mostly in the form of short-lived radionuclides present in the early Solar System, are potentially consistent with this hypothesis, but still allow for alternative explanations. Since the natural production of 126Sn is thought to occur only in supernovae and this isotope has a short half-life (126Sn→126Te, t1/2 = 235 ky), the discovery of extant 126Sn would provide unequivocal proof of supernova input to the early Solar System. Previous attempts to quantify the initial abundance of 126Sn by examining Sn-Te systematics in early solids have been hampered by difficulties in precisely measuring Te isotope ratios in these materials. Thus, here we describe a novel technique that uses hydride generation to dramatically increase the ionization efficiency of Te-an approximately 30-fold increase over previous work. This introduction system, when coupled to a MC-ICPMS, enables high-precision Te isotopic analyses on samples with aluminum-rich inclusions (CAIs) that exhibit an exceptionally large range in Sn/Te ratios, facilitating the search for the short-lived isotope 126Sn. This sample set shows no evidence of live 126Sn, implying at most minor input of supernova material during the time at which the CAIs formed. However, based on the petrology of this sample set combined with the higher than expected concentrations of Sn and Te, as well as the lack of nucleosynthetic anomalies in other isotopes of Te suggest that the bulk of the Sn and Te recovered from these particular refractory inclusions is not of primary origin and thus does not represent a primary signature of Sn-Te systematics of the protosolar nebula during condensation of CAIs or their precursors. Although no evidence of supernova input was found based on Sn-Te systematics

  7. High luminescent fibers with hybrid SiO2-coated CdTe nanocrystals fabricated by electrospinning technique

    International Nuclear Information System (INIS)

    Cao, Yongqiang; Liu, Ning; Yang, Ping; Shi, Ruixia; Ma, Qian; Zhang, Aiyu; Zhu, Yuanna; Wang, Junpeng; Wang, Jianrong

    2015-01-01

    The polyvinylpyrrolidone (PVP) hybrid luminescent micro-/nanofibers doped with the novel hybrid SiO 2 -coated CdTe nanocrystals (HS-CdTe NCs) have been fabricated for the first time via the electrospinning technique. The morphologies and photoluminescence (PL) emissions of HS-CdTe/PVP micro-/nanofibers prepared by doping the HS-CdTe NCs with the different PL peak wavelength (571, 616, and 643 nm) in PVP fibers were investigated by optical and PL microscope. The results revealed that all the HS-CdTe/PVP hybrid fibers showed an ultralong length for several hundreds of micrometers and a relatively uniform diameter of 1000 ∼ 1200 nm. The hybrid fibers displayed a wavelength-tunable PL emission, determining by the PL of doped HS-CdTe NCs. Moreover, similar to the original PL properties of HS-CdTe NCs before the electrospinning, the HS-CdTe/PVP fibers also showed a series of superior PL properties, such as narrow and symmetry PL spectrum, high, and uniform brightness. For comparison purpose, we also prepared three CdTe/PVP hybrid fibers by doping the 553 nm, 600 nm, and 633 nm PL-emitting CdTe NCs respectively in PVP electrospinning fibers. The characterization results showed that, the obtained three CdTe/PVP hybrid fibers had a basically satisfactory micro-/nanofiber morphology with a long length and relatively uniform diameter, but all the fibers exhibited very weak PL emissions. The enormous contrast in PL properties between HS-CdTe/PVP and CdTe/PVP fibers should mainly be ascribed to the different connection modes of ligands with the NCs and the passivation effect of inert hybrid silica shell on HS-CdTe. It is hopeful that the high luminescent HS-CdTe/PVP micro-/nanofibers with the tunable PL peak wavelength would be a good candidate in the optical sensor, light-emitting devices (LEDs), nanometer-scale waveguides, and the other related photonic materials. - Highlights: • The HS-CdTe/PVP electrospun hybrid fibers were fabricated for the first time. • The

  8. Characterization of HgCdTe and HgCdSe Materials for Third Generation Infrared Detectors

    Science.gov (United States)

    2011-12-01

    and Xinghui Kongde for being my best basketball buddies. Finally, I would like to express my most sincere thanks and appreciate towards my parents...annealing on CdTe/Si It has been reported that in situ thermal cycle annealing (TCA), wherein annealing is performed intermittently during the growth

  9. In situ synthesis of highly luminescent glutathione-capped CdTe/ZnS quantum dots with biocompatibility.

    Science.gov (United States)

    Liu, Ying-Fan; Yu, Jun-Sheng

    2010-11-01

    This paper focuses on the in situ synthesis of novel CdTe/ZnS core-shell quantum dots (QDs) in aqueous solution. Glutathione (GSH) was used as both capping reagent and sulfur source for in situ growth of ZnS shell on the CdTe core QDs. The maximum emission wavelengths of the prepared CdTe/ZnS QDs can be simply tuned from 569 nm to 630 nm. The PL quantum yield of CdTe/ZnS QDs synthesized is up to 84%, larger than the original CdTe QDs by around 1.7 times. The PL lifetime results reveal a triexponential decay model of exciton and trap radiation behavior. The average exciton lifetime at room temperature is 17.1 ns for CdTe (2.8 nm) and 27.4 ns for CdTe/ZnS (3.7 nm), respectively. When the solution of QDs is dialyzed for 3 h, 1.17 ppm of Cd(2+) is released from CdTe QDs and 0.35 ppm is released from CdTe/ZnS. At the dose of 120 microg/ml QDs, 9.5% of hemolysis was induced by CdTe QDs and 3.9% was induced by CdTe/ZnS QDs. These results indicate that the synthesized glutathione-capped CdTe/ZnS QDs are of less toxicity and better biocompatibility, so that are attractive for use in biological detection and related fields. Copyright 2010 Elsevier Inc. All rights reserved.

  10. Growth of CdZnTe Crystals for Radiation Detector Applications by Directional Solidification

    Science.gov (United States)

    Su, Ching-Hua

    2014-01-01

    Advances in Cadmium Zinc Telluride (Cd(sub 1-x)Zn(sub x)Te) growth techniques are needed for the production of large-scale arrays of gamma and x-ray astronomy. The research objective is to develop crystal growth recipes and techniques to obtain large, high quality CdZnTe single crystal with reduced defects, such as charge trapping, twinning, and tellurium precipitates, which degrade the performance of CdZnTe and, at the same time, to increase the yield of usable material from the CdZnTe ingot. A low gravity material experiment, "Crystal Growth of Ternary Compound Semiconductors in Low Gravity Environment", will be performed in the Material Science Research Rack (MSRR) on International Space Station (ISS). One section of the flight experiment is the melt growth of CdZnTe ternary compounds. This talk will focus on the ground-based studies on the growth of Cd(sub 0.80)Zn(sub 0.20)Te crystals for radiation detector applications by directional solidification. In this investigation, we have improved the properties that are most critical for the detector applications (electrical properties and crystalline quality): a) Electrical resistivity: use high purity starting materials (with reproducible impurity levels) and controlled Cd over pressure during growth to reproducibly balance the impurity levels and Cd vacancy concentration b) Crystalline quality: use ultra-clean growth ampoule (no wetting after growth), optimized thermal profile and ampoule design, as well as a technique for supercool reduction to growth large single crystal with high crystalline quality

  11. Synthesis of highly luminescent and biocompatible CdTe/CdS/ZnS quantum dots using microwave irradiation: a comparative study of different ligands.

    Science.gov (United States)

    He, Hua; Sun, Xing; Wang, Xiaojuan; Xu, Hai

    2014-11-01

    We compared the effects of several ligands frequently used in aqueous synthesis, including L-cysteine, L-cysteine hydrochloride, N-acetyl-L-cysteine (NAC), glutathione and 3-mercaptopropionic acid, for microwave synthesis of CdTe quantum dots (QDs) in a sealed vessel with varied temperatures and times, and then developed a rapid microwave-assisted protocol for preparing highly luminescent, photostable and biocompatible CdTe/CdS/ZnS core-multishell QDs. The effects of molecular structures of these ligands on QD synthesis under high temperatures were explored. Among these ligands, NAC was found to be the optimal ligand in terms of the optical properties of resultant QDs and reaction conditions. The emission wavelength of NAC-capped CdTe QDs could reach 700 nm in 5 min by controlling the reaction temperature, and the resultant CdTe/CdS/ZnS core-multishell QDs could achieve the highest quantum yields up to 74% with robust photostability. In addition, the effects of temperature, growth time and shell-precursor ratio on shell growth were examined. Finally, cell culturing indicated the low cytotoxicity of CdTe/CdS/ZnS core-multishell QDs as compared to CdTe and CdTe/CdS QDs, suggesting their high potential for applications in biomedical imaging and diagnostics. Copyright © 2014 John Wiley & Sons, Ltd.

  12. Analysis of grain boundaries, twin boundaries, and Te precipitates in CdZnTe grown by high-pressure Bridgeman method

    International Nuclear Information System (INIS)

    Heffelfinger, J.R.; Medlin, D.L.; James, R.B.

    1998-03-01

    Grain boundaries and twin boundaries in commercial Cd 1-x Zn x Te, which is prepared by a high pressure Bridgeman technique, have been investigated with transmission electron microscopy, scanning electron microscopy, infrared light microscopy and visible light microscopy. Boundaries inside these materials were found to be decorated with Te precipitates. The shape and local density of the precipitates were found to depend on the particular boundary. For precipitates that decorate grain boundaries, their microstructure was found to consist of a single, saucer shaped grain of hexagonal Te (space group P3 1 21). Analysis of a Te precipitate precipitates by selected area diffraction revealed the Te to be aligned with the surrounding Cd 1-x Zn x Te grains. This alignment was found to match the (111) Cd 1-x Z x Te planes with the (1 bar 101) planes of hexagonal Te. Crystallographic alignments between the Cd 1-x Zn x Te grains were also observed for a high angle grain boundary. The structure of the grain boundaries and the Te/Cd 1-x Zn x Te interface are discussed

  13. Photovoltaic performance of a Cd{sub 1−x}Mg{sub x}Te/CdS top-cell structure

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Omar S. [Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Temixco, Morelos 62580 (Mexico); Centro del Cambio Global y la Sustentabilidad en el Sureste, Villahermosa, Tabasco 86080 (Mexico); Regalado-Pérez, E.; Mathews, N.R. [Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Temixco, Morelos 62580 (Mexico); Morales, Erik R. [División Académica de Ingeniería y Arquitectura, Universidad Juárez Autónoma de Tabasco, Cunduacán, Tabasco 86690 (Mexico); Reyes-Coronado, David [Unidad Académica Playa del Carmen, Universidad de Quintana Roo, Playa del Carmen, Quintana Roo 77710 (Mexico); Galvez, Geovanni Hernández [Centro del Cambio Global y la Sustentabilidad en el Sureste, Villahermosa, Tabasco 86080 (Mexico); Mathew, Xavier, E-mail: xm@ier.unam.mx [Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Temixco, Morelos 62580 (Mexico)

    2015-05-01

    In this paper we report the progress in developing a wide band gap alloy material based on CdTe to use as the top-cell absorber in tandem solar cells. High photovoltaic performance for a Cd{sub 1−x}Mg{sub x}Te/CdS top-cell was achieved by tuning the composition of the Cd{sub 1−x}Mg{sub x}Te film, and optimizing the device processing. We have carried out studies on the effect of vapor chloride treatment of the Cd{sub 1−x}Mg{sub x}Te/CdS device and the thermal annealing of the Cu/Au contacts on the opto-electronic properties of the device. With improved contact processing and post deposition treatments, we were able to achieve 9.3% efficiency for a 1.6 eV band gap top-cell; Cd{sub 1−x}Mg{sub x}Te/CdS on conductive glass substrate. - Highlights: • Cd{sub 1−x}Mg{sub x}Te films obtained by co-evaporation of CdTe and Mg • Band gap of Cd{sub 1−x}Mg{sub x}Te can be easily tuned by verifying x. • Band gap of Cd{sub 1−x}Mg{sub x}Te is stable only for short annealing durations. • Obtained efficiency of a Cd{sub 1−x}Mg{sub x}Te based device with a band gap of 1.6 eV is 9.3%.

  14. Development of a novel deltamethrin sensor based on molecularly imprinted silica nanospheres embedded CdTe quantum dots

    Science.gov (United States)

    Ge, Shenguang; Lu, Juanjuan; Ge, Lei; Yan, Mei; Yu, Jinghua

    2011-09-01

    A novel procedure for the determination of deltmethrin (DM) is reported. The water-soluble CdTe quantum dots (QDs) and highly fluorescent silica molecularly imprinted nanospheres embedded CdTe QDs (CdTe-SiO 2-MIPs) were prepared and characterized by fluorescence spectroscopy, UV-vis spectroscopy, TEM and IR. The fluorescence nanosensor based CdTe-SiO 2-MIPs is developed. The possible quenching mechanism is discussed by DM. Under optimal conditions, the relative fluorescence intensity of CdTe-SiO 2-MIPs decreased with increasing DM by a Stern-Volmer type equation in the concentration range of 0.5-35.0 μg mL -1, the corresponding detection limit is 0.16 μg mL -1. The developed sensor based on CdTe-SiO 2-MIPs was applied to determine DM in fruit and vegetable samples.

  15. X-ray photoelectron spectroscopy studies of the surface composition of highly luminescent CdTe nanoparticles in multilayer films

    International Nuclear Information System (INIS)

    Zhang Hao; Yang Bai

    2002-01-01

    3-Mercaptopropionic acid-stabilized CdTe nanoparticles were prepared and assembled layer-by-layer with poly(diallyldimethylammonium chloride) (PDAC) to form a polymer-supported ultrathin film by virtue of the Coulombic interaction between negatively charged CdTe and positively charged PDAC. The composition of the CdTe nanoparticle multilayer films was analyzed by X-ray photoelectron spectroscopy (XPS) combined with optical absorbance and luminescence measurements. It was experimentally observed that Cd-thiol complexes on the surface of the CdTe nanoparticles provide the crucial chemical passivation responsible for the high photoluminescence (PL) efficiency of the CdTe particles. The high PL efficiency and high stability of CdTe particles corresponded to the particles with the high surface coverage with Cd-thiol complexes. Moreover, XPS data indicated the surface coverage with Cd-thiol complexes could be increased around the CdTe particle by either reflux or adjusting the pH of resulted CdTe colloidal suspension, which was consistent with the results from optical absorbance and luminescence spectra. It appeared that the popular method of constructing multilayer films could be used as a tool to characterize the surface composition of nanometer-sized particles

  16. Synthesis of SnTe/AgSbSe2 nanocomposite as a promising lead-free thermoelectric material

    Directory of Open Access Journals (Sweden)

    Jun He

    2016-06-01

    Full Text Available A series of SnTe-AgSbSe2 composites were synthesized by a zone-melting method. The nanostructure of the composites was determined by the high resolution transmission electron microscope. The results show that the lattice thermal conductivity is decreased to ∼0.6 W/m·K at 820 K due to the intense scattering of phonon. Also, the carrier concentration increases with AgSbSe2 amounts, and a large effective mass of ∼ 4m0 at room temperature appears at a high carrier concentration of ∼2 × 1021/cm3. A relatively high thermoelectric figure of merit ZT of 0.92 at 820 K is obtained by composition optimization. It is indicated that the SnTe-AgSbSe2 composite should be a promising thermoelectric material.

  17. HRTEM Analysis of Crystallographic Defects in CdZnTe Single Crystal

    Science.gov (United States)

    Yasar, Bengisu; Ergunt, Yasin; Kabukcuoglu, Merve Pinar; Parlak, Mehmet; Turan, Rasit; Kalay, Yunus Eren

    2018-01-01

    In recent years, CdZnTe has attracted much attention due to its superior electrical and structural properties for room-temperature operable gamma and x-ray detectors. However, CdZnTe (CZT) material has often suffered from crystallographic defects encountered during the growth and post-growth processes. The identification and structural characterization of these defects is crucial to synthesize defect-free CdZnTe single crystals. In this study, Cd0.95 Zn0.05 Te single crystals were grown using a three-zone vertical Bridgman system. The single crystallinity of the material was ensured by using x-ray diffraction measurements. High-resolution electron microscopy (HRTEM) was used to characterize the nano-scale defects on the CdZnTe matrix. The linear defects oriented along the ⟨211⟩ direction were examined by transmission electron microscopy (TEM) and the corresponding HRTEM image simulations were performed by using a quantitative scanning TEM simulation package.

  18. Effect of electric field on spray deposited CdTe thin films

    Energy Technology Data Exchange (ETDEWEB)

    Vamsi Krishna, K.; Dutta, V.; Paulson, P.D

    2003-11-01

    CdTe thin films have been deposited using spray pyrolysis with and without electric field. The improvement in the film properties with the electric field is observed which is mainly due to the reduction of droplet size. The presence of CdTeO{sub 3} peaks in the X-ray diffraction pattern for films deposited without electric field at 350 deg. C is attributed to the slow dissociation of complexes containing Cd and Te ions on the substrate. The reduction in the droplet size under the influence of electric field and faster dissociation of droplets at high temperature leads to complete pyrolytic reaction for a nearly oxide free CdTe film formation. Energy dispersive X-ray analysis indicates stoichiometric Cd and Te atomic concentrations, with oxygen and chlorine impurities in varying amount for different substrate temperatures, with and without electric field. The presence of chlorine gives rise to an intense photoluminescence peak at 1.40 eV along with a weak peak at 0.84 eV. The intensities of both peaks diminish when the films are prepared with the electric field, due to reduction of chlorine concentration and morphological changes in the films.

  19. Strain relaxation of CdTe on Ge studied by medium energy ion scattering

    Energy Technology Data Exchange (ETDEWEB)

    Pillet, J.C., E-mail: jean-christophe.pillet@cea.fr [Univ. Grenoble Alpes, CEA, LETI, MINATEC campus, F38000 Grenoble (France); CEA, LETI, Département Optique et Photonique, F38054 Grenoble (France); Pierre, F. [Univ. Grenoble Alpes, CEA, LETI, MINATEC campus, F38000 Grenoble (France); CEA, LETI, Service de Caractérisation des Matériaux et Composants, F38054 Grenoble (France); Jalabert, D. [Univ. Grenoble Alpes, CEA, LETI, MINATEC campus, F38000 Grenoble (France); CEA-INAC/UJF-Grenoble 1 UMR-E, SP2M, LEMMA, Minatec Grenoble F-38054 (France)

    2016-10-01

    We have used the medium energy ion scattering (MEIS) technique to assess the strain relaxation in molecular-beam epitaxial (MBE) grown CdTe (2 1 1)/Ge (2 1 1) system. A previous X-ray diffraction study, on 10 samples of the same heterostructure having thicknesses ranging from 25 nm to 10 μm has allowed the measurement of the strain relaxation on a large scale. However, the X-ray diffraction measurements cannot achieve a stress measurement in close proximity to the CdTe/Ge interface at the nanometer scale. Due to the huge lattice misfit between the CdTe and Ge, a high degree of disorder is expected at the interface. The MEIS in channeling mode is a good alternative in order to profile defects with a high depth resolution. For a 21 nm thick CdTe layer, we observed, at the interface, a high density of Cd and/or Te atoms moved from their expected crystallographic positions followed by a rapid recombination of defects. Strain relaxation mechanisms in the vicinity of the interface are discussed.

  20. Enhancement in microstructural and optoelectrical properties of thermally evaporated CdTe films for solar cells

    Directory of Open Access Journals (Sweden)

    Subhash Chander

    2018-03-01

    Full Text Available The optimization of microstructural and optoelectrical properties of a thin layer is an important step prior device fabrication process, so an enhancement in these properties of thermally evaporated CdTe thin films is reported in this communication. The films having thickness 450 nm and 850 nm were deposited on thoroughly cleaned glass and indium tin oxide (ITO substrates followed by annealing at 450 °C in air atmosphere. These films were characterized for microstructural and optoelectrical properties employing X-ray diffraction, scanning electron microscopy coupled with energy-dispersive spectroscopy, UV-Vis spectrophotometer and source meter. The films found to be have zinc-blende cubic structure with preferred reflection (111 while the crystallographic parameters and direct energy band gap are strongly influenced by the film thickness. The surface morphology studies show that the films are uniform, smooth, homogeneous and nearly dense-packed as well as free from voids and pitfalls as where elemental analysis revealed the presence of Cd and Te element in the deposited films. The electrical analysis showed linear behavior of current with voltage while conductivity is decreased for higher thickness. The results show that the microstructural and optoelectrical properties of CdTe thin layer could be enhanced by varying thickness and films having higher thickness might be processed as promising absorber thin layer to the CdTe-based solar cells. Keywords: CdTe thin film, Microstructural, Optoelectrical, Thermal evaporation

  1. Preparation of bioconjugates of CdTe nanocrystals for cancer marker detection

    Energy Technology Data Exchange (ETDEWEB)

    Hu Fengqin [Key Laboratory of Colloid, Interface Science and Chemical Thermodynamics, Molecular Science Center, Institute of Chemistry, Chinese Academy of Sciences, Zhong Guan Cun, Bei Yi Jie 2, Beijing 100080 (China); Ran Yuliang [Department of Cell and Molecular Biology, Cancer Institute, Chinese Academy of Medical Sciences and Peking Union Medical College, Pan Jia Yuan, Chao Yang Qu, Beijing 100021 (China); Zhou Zhuan [Department of Cell and Molecular Biology, Cancer Institute, Chinese Academy of Medical Sciences and Peking Union Medical College, Pan Jia Yuan, Chao Yang Qu, Beijing 100021 (China); Gao Mingyuan [Key Laboratory of Colloid, Interface Science and Chemical Thermodynamics, Molecular Science Center, Institute of Chemistry, Chinese Academy of Sciences, Zhong Guan Cun, Bei Yi Jie 2, Beijing 100080 (China)

    2006-06-28

    Highly fluorescent CdTe quantum dots (Q-dots) stabilized by 3-mercaptopropionic acid (MPA) were prepared by an aqueous solution approach and used as fluorescent labels in detecting a cancer marker, carcinoembryonic antigen (CEA), expressed on human colon carcinoma cell line LS 180. Nonspecific adsorptions of CdTe Q-dots on carcinoma cells were observed and effectively eliminated by replacing MPA with a thiolated PEG (poly(ethylene glycol), Mn = 750) synthesized according to literature. It was unexpectedly found out that the PEG-coated CdTe Q-dots exhibited very strong and specific affinity to anti-CEA monoclonal antibody rch 24 (rch 24 mAb). The resultant CdTe-(rch 24 mAb) conjugates were successfully used in detections of CEA expressed on the surface of cell line LS 180. Further experiments demonstrated that the fluorescent CdTe Q-dots exhibited much better photostability and a brighter fluorescence than FITC, which consequently led to a higher efficiency in the cancer marker detection.

  2. Luminescent behavior of CdTe quantum dots: Neodymium(III) complex-capped nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, Margarida S. [Centro de Geologia do Porto, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto (Portugal); Algarra, Manuel, E-mail: magonzal@fc.up.pt [Centro de Geologia do Porto, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto (Portugal); Jimenez-Jimenez, Jose; Rodriguez-Castellon, Enrique [Departamento de Quimica Inorganica, Facultad de Ciencias, Universidad de Malaga, Campus de Teatinos s/n 29071, Malaga (Spain); Campos, Bruno B.; Esteves da Silva, Joaquim C.G. [Centro de Investigacao em Quimica (CIQ-UP), Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto (Portugal)

    2013-02-15

    A water soluble complex of neodymium(III) with CdTe quantum dots nanoparticles was synthesized. The obtained homogeneous solutions were characterized by fluorescence, X-ray photoelectron and energy dispersive X-ray spectroscopies. The effect of the refluxing time of the reaction on the fluorescence intensity and emission wavelength has been studied. It was found that the emission wavelength of the solutions of neodymium(III) complex capped CdTe QDs nanoparticles shifted from about 540 to 735 nm. For an emission wavelength of 668 nm, the most reproducible nanoparticles obtained, the pH effect over the fluorescence emission and its intensity were studied. The purified and lyophilized solid obtained was morphologically characterized by transmission electron microscopy (TEM). The quantitative composition was determined by fluorescence X-ray spectroscopy (EDAX) and the X-ray photoelectron analysis (XPS) confirmed the presence of neodymium(III) at the surface of the CdTe nanoparticles forming a complex with the carboxylate groups from 3-mercaptopropanoic acid of the CdTe QDs. Due to the optical behavior of this complex, it could be of potential interest as a light source in optical devices. - Highlights: Black-Right-Pointing-Pointer CdTe quantum dots nanoparticles. Black-Right-Pointing-Pointer Neodymium(III) complexed quantum dots. Black-Right-Pointing-Pointer Strong red fluorescent emission nanomaterial soluble in water.

  3. Studying nanotoxic effects of CdTe quantum dots in Trypanosoma cruzi

    Directory of Open Access Journals (Sweden)

    Cecilia Stahl Vieira

    2011-03-01

    Full Text Available Semiconductor nanoparticles, such as quantum dots (QDs, were used to carry out experiments in vivo and ex vivo with Trypanosoma cruzi. However, questions have been raised regarding the nanotoxicity of QDs in living cells, microorganisms, tissues and whole animals. The objective of this paper was to conduct a QD nanotoxicity study on living T. cruzi protozoa using analytical methods. This was accomplished using in vitro experiments to test the interference of the QDs on parasite development, morphology and viability. Our results show that after 72 h, a 200 μM cadmium telluride (CdTe QD solution induced important morphological alterations in T. cruzi, such as DNA damage, plasma membrane blebbing and mitochondrial swelling. Flow cytometry assays showed no damage to the plasma membrane when incubated with 200 μM CdTe QDs for up to 72 h (propidium iodide cells, giving no evidence of classical necrosis. Parasites incubated with 2 μM CdTe QDs still proliferated after seven days. In summary, a low concentration of CdTe QDs (2 μM is optimal for bioimaging, whereas a high concentration (200 μM CdTe could be toxic to cells. Taken together, our data indicate that 2 μM QD can be used for the successful long-term study of the parasite-vector interaction in real time.

  4. Recent Developments of Flexible CdTe Solar Cells on Metallic Substrates: Issues and Prospects

    Directory of Open Access Journals (Sweden)

    M. M. Aliyu

    2012-01-01

    Full Text Available This study investigates the key issues in the fabrication of CdTe solar cells on metallic substrates, their trends, and characteristics as well as effects on solar cell performance. Previous research works are reviewed while the successes, potentials, and problems of such technology are highlighted. Flexible solar cells offer several advantages in terms of production, cost, and application over glass-based types. Of all the metals studied as substrates for CdTe solar cells, molybdenum appears the most favorable candidate, while close spaced sublimation (CSS, electrodeposition (ED, magnetic sputtering (MS, and high vacuum thermal evaporation (HVE have been found to be most common deposition technologies used for CdTe on metal foils. The advantages of these techniques include large grain size (CSS, ease of constituent control (ED, high material incorporation (MS, and low temperature process (MS, HVE, ED. These invert-structured thin film CdTe solar cells, like their superstrate counterparts, suffer from problems of poor ohmic contact at the back electrode. Thus similar strategies are applied to minimize this problem. Despite the challenges faced by flexible structures, efficiencies of up to 13.8% and 7.8% have been achieved in superstrate and substrate cell, respectively. Based on these analyses, new strategies have been proposed for obtaining cheaper, more efficient, and viable flexible CdTe solar cells of the future.

  5. Selective Detection of Formaldehyde Gas Using a Cd-Doped TiO2-SnO2 Sensor

    Directory of Open Access Journals (Sweden)

    Yuichi Ikuhara

    2009-11-01

    Full Text Available We report the microstructure and gas-sensing properties of a nonequilibrium TiO2-SnO2 solid solution prepared by the sol-gel method. In particular, we focus on the effect of Cd doping on the sensing behavior of the TiO2-SnO2 sensor. Of all volatile organic compound gases examined, the sensor with Cd doping exhibits exclusive selectivity as well as high sensitivity to formaldehyde, a main harmful indoor gas. The key gas-sensing quantities, maximum sensitivity, optimal working temperature, and response and recovery time, are found to meet the basic industrial needs. This makes the Cd-doped TiO2-SnO2 composite a promising sensor material for detecting the formaldehyde gas.

  6. Effect of NH4F/H2O2 Passivation on CdZnTe Detector

    International Nuclear Information System (INIS)

    Park, Se-Hwan; Ha, Jang-Ho; Cho, Yoon-Ho; Kim, Han-Soo; Kim, Yong-Kyun

    2006-01-01

    CdZnTe is the most promising material for X-ray and γ-ray detector. Many researchers have studied the fabrication process of CdZnTe detector. Generally, the CdZnTe crystal was grinded, mechanically polished, and chemically etched. After that, the metal electrodes were deposited on the crystal. Bromine/Methanol etchant is widely used for the chemical etching of the CdZnTe surface. The chemical etching is very important process to fabricate the CdZnTe radiation detector. The mechanical polishing would make the scratch on the CdZnTe surface, and remain the dangling bonds on the surface. The chemical etching could remove the mechanical scratch on the surface. However, the CdZnTe surface would remain non-stoichiometric after the chemical etching with Bromine/Methanol etchant, because the bromine reacts with cadmium more easily. The passivation is very important process to remove the non-stoichimetry of the CdZnTe surface. Also, the passivation could make the CdZnTe detector electrically inert to its environment

  7. Effect of interfacial reactions on the photoelectrical performance of In(CrOx)/CdTe/ITO heterostructures

    International Nuclear Information System (INIS)

    Bojko, B.T.; Kopach, G.I; Khripunov, G.S.

    2000-01-01

    The effect of interphase interaction of interlinking layers on photoelectric properties of cadmium telluride base polycrystalline photoelectric converters was studied to optimize their production process. It was shown that reduction of the high level of CdTe surface grains moving of space charge range in the base layer from the finely-crystalline defects layer at CdTe/ITO interface and CrO x /CdTe contact substitution for In/CdTe rear contact increased the efficiency of those photoelectric converters up to 6 % [ru

  8. Characterization and photoluminescence studies of CdTe nanoparticles before and after transfer from liquid phase to polystyrene

    International Nuclear Information System (INIS)

    Wang, Shugang; Li, Yaoxian; Bai, Jie; Yang, Qingbiao; Song, Yan; Zhang, Chaoqun

    2009-01-01

    The major objective of this work was to detect the change of photoluminescence (PL) intensity of CdTe nanoparticles (NPs) before and after transfer from liquid phase to polystyrene (PS) matrix by electrospinning technique. Thio-stabilized CdTe NPs were first synthesized in aqueous, then enwrapped by cetyl-trimethylammonium bromide (CTAB), and finally, transferred into PS matrix to form CdTe/PS nanofibres by electrospinning. Then, CdTe/PS nanofibres were characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM) to observe their morphology and distribution, respectively. The selective area electronic diffraction (SAED) pattern proved that the CdTe NPs were cubic lattice. The PL spectrum indicated that CdTe NPs have been transferred into PS nanofibres, and the PL intensity of CdTe NPs in the nanofibres was even higher than that before CdTe NPs were introduced into PS nanofibres. Moreover, X-ray photoelectron spectra (XPS) revealed that thiol-stabilized CdTe NPs were enwrapped by CTAB, and PS acted as a dispersant in the process of electrospinning. (author)

  9. Automatic Control System for the High Pressure CdTe Crystal Growth Furnace

    Directory of Open Access Journals (Sweden)

    Petr Praus

    2006-08-01

    Full Text Available CdTe and (CdZnTe bulk single crystals have been widely used as substrates for MBE and LPE epitaxy of infrared (HgCdTe as well as gamma- and X-ray detectors. The Cd1-xZnxTe (x = 0.04-0.1 single crystals with diameter up to 100 mm and height at most 40 mm were prepared in our laboratory in a vertical arrangement by gradual cooling of the melt (the Vertical Gradient Freezing method. Achievement of excellent crystal quality required full control of Cd pressure during the growth process and application of high Cd pressures (up to 4 bar at growth temperature. An electronic control system was designed to control both temperature and internal pressure of two zones CZT crystal growth furnace by using two high performance PID controllers/setpoint programmers. Two wire current loop serial communication bus was used for the data exchange and computer control of the furnace electronics setup. Control software was written to supervise the crystal growth process and to collect all important data and parameters.

  10. Approaching the r-process "waiting point" nuclei below $^{132}$Sn: quadrupole collectivity in $^{128}$Cd

    CERN Multimedia

    Reiter, P; Blazhev, A A; Nardelli, S; Voulot, D; Habs, D; Schwerdtfeger, W; Iwanicki, J S

    We propose to investigate the nucleus $^{128}$Cd neighbouring the r-process "waiting point" $^{130}$Cd. A possible explanation for the peak in the solar r-abundances at A $\\approx$ 130 is a quenching of the N = 82 shell closure for spherical nuclei below $^{132}$Sn. This explanation seems to be in agreement with recent $\\beta$-decay measurements performed at ISOLDE. In contrast to this picture, a beyond-mean-field approach would explain the anomaly in the excitation energy observed for $^{128}$Cd rather with a quite large quadrupole collectivity. Therefore, we propose to measure the reduced transition strengths B(E2) between ground state and first excited 2$^{+}$-state in $^{128}$Cd applying $\\gamma$-spectroscopy with MINIBALL after "safe" Coulomb excitation of a post-accelerated beam obtained from REX-ISOLDE. Such a measurement came into reach only because of the source developments made in 2006 for experiment IS411, in particular the use of a heated quartz transfer line. The result from the proposed measure...

  11. Effect of CdCl{sub 2} annealing treatment on structural and optoelectronic properties of close spaced sublimation CdTe/CdS thin film solar cells vs deposition conditions

    Energy Technology Data Exchange (ETDEWEB)

    Spalatu, N., E-mail: nickspalatu@gmail.com [Department of Materials Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Hiie, J.; Mikli, V.; Krunks, M.; Valdna, V.; Maticiuc, N.; Raadik, T. [Department of Materials Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Caraman, M. [Physics Department, Moldova State University, A. Mateevici str. 60, Chisinau MD 2009, Republic of Moldova (Moldova, Republic of)

    2015-05-01

    CdTe/CdS thin films were deposited by close-spaced vacuum sublimation at substrate temperatures 250-500 °C. The effect of substrate temperature in conjunction with CdCl{sub 2} heat treatment on the properties of CdTe/CdS thin films and devices is reported. X-ray diffraction measurements of structural properties of the films were carried out to study their phase composition and texture. Surface morphology, grain size and growth mechanism of the films were determined by the scanning electron microscopy. The photoluminescence measurements allowed us to establish the correlation between the point and extended defect structure on the one hand and the growth conditions on the other. The CdTe/CdS solar cells fabricated at high substrate temperature, exhibited improved electrical characteristics compared to cells fabricated at low substrate temperature, yielding a high efficiency. - Highlights: • Dependence of CdTe/CdS solar cell properties on substrate temperature of CSS CdTe. • Increase of substrate temperature leads to formation of large densely packed grains. • Decrease in substrate temperature leads to formation of columnar grains. • CdCl{sub 2} treatment unifies the CdTe/CdS structure regardless of substrate temperature. • Increase in substrate temperature enhanced efficiency of CdTe/CdS solar cells.

  12. Optical and structural characterization of oleic acid-stabilized CdTe nanocrystals for solution thin film processing

    Directory of Open Access Journals (Sweden)

    Claudio Davet Gutiérrez-Lazos

    2014-06-01

    Full Text Available This work presents results of the optical and structural characterization of oleic acid-stabilized cadmium telluride nanocrystals (CdTe-NC synthesized by an organometallic route. After being cleaned, the CdTe-NC were dispersed in toluene to obtain an ink-like dispersion, which was drop-cast on glass substrate to deposit a thin film. The CdTe-NC colloidal dispersion as well as the CdTe drop-cast thin films were characterized with regard to the optical and structural properties. TEM analysis indicates that the CdTe-NC have a nearly spherical shape (3.5 nm as mean size. Electron diffraction and XRD diffraction analyses indicated the bulk-CdTe face-centered cubic structure for CdTe-NC. An additional diffraction line corresponding to the octahedral Cd3P2 was also detected as a secondary phase, which probably originates by reacting free cadmium ions with trioctylphosphine (the tellurium reducing agent. The Raman spectrum exhibits two broad bands centered at 141.6 and 162.3 cm−1, which could be associated to the TO and LO modes of cubic CdTe nanocrystals, respectively. Additional peaks located in the 222 to 324 cm−1 range, agree fairly well with the wavenumbers reported for TO modes of octahedral Cd3P2.

  13. Chromium-induced ferromagnetism with perpendicular anisotropy in topological crystalline insulator SnTe (111) thin films

    Science.gov (United States)

    Wang, Fei; Zhang, Hongrui; Jiang, Jue; Zhao, Yi-Fan; Yu, Jia; Liu, Wei; Li, Da; Chan, Moses H. W.; Sun, Jirong; Zhang, Zhidong; Chang, Cui-Zu

    2018-03-01

    Topological crystalline insulator is a recently discovered topological phase of matter. It possesses multiple Dirac surface states, which are protected by the crystal symmetry. This is in contrast to the time-reversal symmetry that is operative in the well-known topological insulators. In the presence of a Zeeman field and/or strain, the multiple Dirac surface states are gapped. The high-Chern-number quantum anomalous Hall (QAH) state is predicted to emerge if the chemical potential resides in all the Zeeman gaps. Here, we use molecular-beam epitaxy to grow 12 double-layer (DL) pure and Cr-doped SnTe (111) thin film on heat-treated SrTi O3 (111) substrate using a quintuple layer of insulating (Bi0.2Sb0.8 ) 2T e3 topological insulator as a buffer film. The Hall traces of Cr-doped SnTe film at low temperatures display square hysteresis loops indicating long-range ferromagnetic order with perpendicular anisotropy. The Curie temperature of the 12 DL S n0.9C r0.1Te film is ˜110 K. Due to the chemical potential crossing the bulk valence bands, the anomalous Hall resistance of 12 DL S n0.9C r0.1Te film is substantially lower than the predicted quantized value (˜1 /4 h /e2 ). It is possible that with systematic tuning the chemical potential via chemical doping and electrical gating, the high-Chern-number QAH state can be realized in the Cr-doped SnTe (111) thin film.

  14. Spin-polarized charge transport in HgTe/CdTe quantum well topological insulator under a ferromagnetic metal strip

    Science.gov (United States)

    Wu, Zhenhua; Luo, Kun; Yu, Jiahan; Wu, Xiaobo; Lin, Liangzhong

    2018-02-01

    Electron tunneling through a single magnetic barrier in a HgTe topological insulator has been theoretically investigated. We find that the perpendicular magnetic field would not lead to spin-flip of the edge states due to the conservation of the angular moment. By tuning the magnetic field and the Fermi energy, the edge channels can be transited from switch-on states to switch-off states and the current from unpolarized states can be filtered to fully spin polarized states. These features offer us an efficient way to control charge/spin transport in a HgTe/CdTe quantum well, and pave a way to construct the nanoelectronic devices utilizing the topological edge states.

  15. New Architecture towards Ultrathin CdTe Solar Cells for High Conversion Efficiency

    OpenAIRE

    Teyou Ngoupo, A.; Ouédraogo, S.; Zougmoré, F.; Ndjaka, J. M. B.

    2015-01-01

    Solar Cell Capacitance Simulator in 1 Dimension (SCAPS-1D) is used to investigate the possibility of realizing ultrathin CdTe based solar cells with high and stable conversion efficiency. In the first step, we modified the conventional cell structure by substituting the CdS window layer with a CdS:O film having a wide band gap ranging from 2.42 to 3.17 eV. Thereafter, we simulated the quantum efficiency, as well as the parameters of J-V characteristics, and showed how the thickness of CdS:O l...

  16. Characterization of a pixel CdTe detector for nuclearv medicine imaging

    OpenAIRE

    Ariño Estrada, Gerard

    2015-01-01

    Aquesta tesi presenta la caracterització d'un disseny de detector pxel de CdTe per aplicació en imatge en medicina nuclear. El treball d'aquesta tesi s'ha portat a terme en el marc del projecte Voxel Imaging PET (VIP) Pathnder. El projecte VIP es un projecte ambiciós que pretén provar la viabilitat d'utilitzar detectors pixel·lats de CdTe en imatge en medicina nuclear. El disseny proposat és el mòdul VIP, que consta de blocs de CdTe de 10 mm 10 mm de superfcie i 2 mm de gruix, que estan segme...

  17. Electrochemical Determination of Uric Acid at CdTe Quantum Dot Modified Glassy Carbon Electrodes.

    Science.gov (United States)

    Pan, Deng; Rong, Shengzhong; Zhang, Guangteng; Zhang, Yannan; Zhou, Qiang; Liu, Fenghai; Li, Miaojing; Chang, Dong; Pan, Hongzhi

    2015-01-01

    Cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical behavior of uric acid (UA) at a CdTe quantum dot (QD) modified the glassy carbon electrode (GCE). CdTe QDs, as new semiconductor nanocrystals, can greatly improve the peak current of UA. The anodic peak current of UA was linear with its concentration between 1.0×10(-6) and 4.0×10(-4) M in 0.1 M pH 5.0 phosphate buffer solution. The LOD for UA at the CdTe electrode (1.0×10(-7) M) was superior to that of the GCE. In addition, we also determined the effects of scan rate, pH, and interferences of UA for the voltammetric behavior and detection. The results indicated that modified electrode possessed excellent reproducibility and stability. Finally, a new and efficient electrochemical sensor for detecting UA was developed.

  18. Studies of the surface regions of (Cd,Mn)Te crystals

    International Nuclear Information System (INIS)

    Kochanowska, Dominika; Witkowska-Baran, Marta; Mycielski, Andrzej; Rasinski, Marcin; Lewandowska, Malgorzata

    2014-01-01

    The growth process conditions affect quality of the crys-tal. Structural defects such as grains, twin boundaries and precipitates are formed during the crystal growth. The defects (especially-inclusions) at the surface can be investigated in a microscale by the scanning electron microscopy (SEM). It is shown in the article that a well known etchant, usually used for visual inspection of the quality of the CdTe-related crystals, can be applied to the preparation of the (Cd,Mn)Te surface for SEM investigations. Samples, cut from different parts of a (Cd,Mn)Te crystal, were ground, mechano-chemically polished, and treated by the special etchant (to indicate polarity and to reveal twinning). After that treatment the defects (grain and twin boundaries, tellurium inclusions) at the surface became much more accessible for both SEM and visual investigations. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Impulse response measurement in the HgCdTe avalanche photodiode

    Science.gov (United States)

    Singh, Anand; Pal, Ravinder

    2018-04-01

    HgCdTe based mid-wave infrared focal plane arrays (MWIR FPAs) are being developed for high resolution imaging and range determination of distant camouflaged targets. Effect of bandgap grading on the response time in the n+/ν/p+ HgCdTe electron avalanche photodiode (e-APD) is evaluated using impulse response measurement. Gain normalized dark current density of 2 × 10-9 A/cm2 at low reverse bias for passive mode and 2 × 10-4 A/cm2 at -8 V for active mode is measured in the fabricated APD device, yielding high gain bandwidth product of 2.4 THZ at the maximum gain. Diffusion of carriers is minimized to achieve transit time limited impulse response by introducing composition grading in the HgCdTe epilayer. The noise equivalent photon performance less than one is achievable in the FPA that is suitable for active cum passive imaging applications.

  20. A new MBE CdTe photoconductor array detector for X-ray applications

    International Nuclear Information System (INIS)

    Yoo, S.S.; Sivananthan, S.; Faurie, J.P.; Rodricks, B.; Bai, J.; Montano, P.A.; Argonne National Lab., IL

    1994-10-01

    A CdTe photoconductor array x-ray detector was grown using Molecular Beam Epitaxially (MBE) on a Si (100) substrate. The temporal response of the photoconductor arrays is as fast as 21 psec risetime and 38 psec Full Width Half Maximum (FWHM). Spatial and energy responses were obtained using x-rays from a rotating anode and synchrotron radiation source. The spatial resolution of the photoconductor was good enough to provide 75 microm FWHM using a 50 microm synchrotron x-ray beam. A substantial number of x-ray photons are absorbed effectively within the MBE CdTe layer as observed from the linear response up to 15 keV. These results demonstrate that MBE grown CdTe is a suitable choice of the detector materials to meet the requirements for x-ray detectors in particular for the new high brightness synchrotron sources

  1. Heavy doping of CdTe single crystals by Cr ion implantation

    Science.gov (United States)

    Popovych, Volodymyr D.; Böttger, Roman; Heller, Rene; Zhou, Shengqiang; Bester, Mariusz; Cieniek, Bogumil; Mroczka, Robert; Lopucki, Rafal; Sagan, Piotr; Kuzma, Marian

    2018-03-01

    Implantation of bulk CdTe single crystals with high fluences of 500 keV Cr+ ions was performed to achieve Cr concentration above the equilibrium solubility limit of this element in CdTe lattice. The structure and composition of the implanted samples were studied using secondary ion mass spectrometry (SIMS), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS) to characterize the incorporation of chromium into the host lattice and to investigate irradiation-induced damage build-up. It was found that out-diffusion of Cr atoms and sputtering of the targets alter the depth distribution and limit concentration of the projectile ions in the as-implanted samples. Appearance of crystallographically oriented, metallic α-Cr nanoparticles inside CdTe matrix was found after implantation, as well as a strong disorder at the depth far beyond the projected range of the implanted ions.

  2. Band offset at the heterojunction interfaces of CdS/ZnSnP2, ZnS/ZnSnP2, and In2S3/ZnSnP2

    Science.gov (United States)

    Nakatsuka, Shigeru; Nose, Yoshitaro; Shirai, Yasuharu

    2016-05-01

    Heterojunctions were formed between ZnSnP2 and buffer materials, CdS, ZnS, and In2S3, using chemical bath deposition. The band offset was investigated by X-ray photoelectron spectroscopy based on Kraut method. The conduction band offset, ΔEC, between ZnSnP2 and CdS was estimated to be -1.2 eV, which significantly limits the open circuit voltage, VOC. Conversely, ΔEC at the heterojunction between ZnSnP2 and ZnS was +0.3 eV, which is within the optimal offset range. In the case of In2S3, ΔEC was a relatively small value, -0.2 eV, and In2S3 is potentially useful as a buffer layer in ZnSnP2 solar cells. The J-V characteristics of heterojunction diodes with an Al/sulfides/ZnSnP2 bulk/Mo structure also suggested that ZnS and In2S3 are promising candidates for buffer layers in ZnSnP2 thin film solar cells, and the band alignment is a key factor for the higher efficiency of solar cells with heterojunctions.

  3. Multilayer solar cells based on CdTe grown from nitrate precursor

    Science.gov (United States)

    Salim, Hussein I.

    This thesis presents the research and development of low-cost multilayer graded-bandgap solar cells based on electrodeposited CdTe. The electronic quality layers used in this research are electrodeposited CdS and CdTe and chemical bath deposited (CBD) CdS. In the literature, the electrodeposition of CdS layers has been mainly reported using sodium thiosulphate (Na2S2O3), ammonium thiosulphate (NH4)2S2O3 and thioacetamide (C2H5NS) as the precursor for sulphur ions. The major disadvantages of these precursors are the precipitation of elemental S and CdS particles in the solution during growth which can affect the quality of the deposited thin films. Electrodeposition of the CdS from acidic and aqueous solutions using thiourea (SC(NH2)2) precursor has been able to overcome this disadvantage. No visible precipitations of elemental S or CdS particles were observed in the deposition electrolyte showing a stable bath during the growth.Also, in the literature, the CdTe thin films have been mainly electrodeposited using CdSO4 as the precursor for Cd ions whereas in this thesis the electrodeposition of the CdTe thin films were carried out comprehensively using cadmium nitrate Cd(NO3)2 as the precursor for Cd ions. Reports are scarce on the electrodeposition of CdS and CdTe thin films history using thiourea and nitrate precursors. Using these precursors, the CdS and CdTe have been successfully electrodeposited from aqueous solution on glass/fluorine-doped tin oxide (FTO) substrates, using simplified two-electrode system instead of the conventional three-electrode system. Also, the CBD-CdS thin films have been successfully grown from aqueous solution on glass/FTO substrates.The electrodeposited and chemical bath deposited materials were characterised for their structural, compositional, morphological, optical, electrical and defect properties using X-ray diffraction (XRD), Raman spectroscopy, energy dispersive X-ray diffraction (EDX), scanning electron microscopy (SEM), atomic

  4. Bond lengths in Cd1-xZnxTe beyond linear laws revisited

    International Nuclear Information System (INIS)

    Koteski, V.; Haas, H.; Holub-Krappe, E.; Ivanovic, N.; Mahnke, H.-E.

    2004-01-01

    We have investigated the development of local bond lengths with composition in the Cd 1-x Zn x Te mixed system by measuring the fine structure in X-ray absorption (EXAFS) at all three constituent atoms. The bond strength is found to dominate over the averaging of the bulk so that the local bond length deviates only slightly from its natural value determined for the pure binary components ZnTe and CdTe, respectively. The deviations are significantly less than predicted by a simple radial force constant model for tetrahedrally co-ordinated binary systems, and the bond-length variation with concentration is significantly non-linear. For the second shell, bimodal anion-anion distances are found while the cation-cation distances can already be described by the virtual crystal approximation. In the diluted regime close to the end-point compounds, we have complemented our experimental work by ab initio calculations based on density functional theory with the WIEN97 program using the linearised augmented plane wave method. Equilibrium atomic lattice positions have been calculated for the substitutional isovalent metal atom in a 32-atom super cell, Zn in the CdTe lattice or Cd in the ZnTe lattice, respectively, yielding good agreement with the atomic distances as determined in our EXAFS experiments

  5. Characterization of CdZnTe after argon ion beam bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Bensalah, H., E-mail: hakima.bensalah@uam.es [Departamento de Fisica de Materiales, Laboratorio de Crecimiento de Cristales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Hortelano, V. [GdS-Optronlab Group, Departamento Fisica Materia Condensada, Universidad de Valladolid, Edificio I-D, Paseo de Belen 1, 47011 Valladolid (Spain); Plaza, J.L. [Departamento de Fisica de Materiales, Laboratorio de Crecimiento de Cristales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Martinez, O. [GdS-Optronlab Group, Departamento Fisica Materia Condensada, Universidad de Valladolid, Edificio I-D, Paseo de Belen 1, 47011 Valladolid (Spain); Crocco, J.; Zheng, Q.; Carcelen, V.; Dieguez, E. [Departamento de Fisica de Materiales, Laboratorio de Crecimiento de Cristales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2012-12-05

    Highlights: Black-Right-Pointing-Pointer After argon irradiation using low fluence, the defects on surface were removed. Black-Right-Pointing-Pointer The PL intensity increases after irradiation. This increase should be related to the improved quality of the CdZnTe surfaces. Black-Right-Pointing-Pointer Irradiation process lead to an elimination of Te precipitates from the surfaces of the CdZnTe samples. - Abstract: The objective of this work is to analyze the effects of argon ion irradiation process on the structure and distribution of Te inclusions in Cd{sub 1-x}Zn{sub x}Te crystals. The samples were treated with different ion fluences ranging from 2 to 8 Multiplication-Sign 10{sup 17} cm{sup -2}. The state of the samples before and after irradiation were studied by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Cathodoluminescence, Photoluminescence, and micro-Raman spectroscopy. The effect of the irradiation on the surface of the samples was clearly observed by SEM or AFM. Even for small fluences a removal of polishing scratches on the sample surfaces was observed. Likely correlated to this effect, an important enhancement in the luminescence intensity of the irradiated samples was observed. An aggregation effect of the Te inclusions seems to occur due to the Ar bombardment, which are also eliminated from the surfaces for the highest ion fluences used.

  6. Measurements of Charge Sharing Effects in Pixilated CZT/CdTe Detectors

    DEFF Research Database (Denmark)

    Kuvvetli, Irfan; Budtz-Jørgensen, Carl

    2007-01-01

    In this paper, charge sharing and charge loss effects in pixilated CZT/CdTe detectors are investigated by measurements. We measured charge sharing effects function of the inter-pixel gap (with same pixel pitch), the photon energy and the detector bias voltage for a large numbers of CZT and CdTe...... pixel detector samples. The results are used for the development of the large area X-ray and Gamma ray detector for the Atmosphere-Space Interactions Monitor (ASIM) planned for the ISS ESA Columbus module. Charge sharing measurements on detector samples with identical size and pixel geometry...

  7. Modeling and Design of a Thin-Film CdTe/Ge Tandem Solar Cell

    Science.gov (United States)

    Sharp, James; Pulfrey, David; Umana-Membreno, Gilberto A.; Faraone, Lorenzo; Dell, John M.

    2012-10-01

    Thin-film cadmium telluride (CdTe) solar cells have found widespread application, with current commercially available module efficiencies reaching 14.4% and production costs falling as low as US 0.75/W_p. Despite the proliferation of this technology, there have been comparatively few developments in research circles in recent years. Rather than attempt to further advance the materials science of CdTe solar cells, it is proposed to realize an efficiency improvement over conventional cells by means of a novel tandem structure. Three such structures are examined herein, and results of simulation using Synopsys Sentaurus TCAD are presented.

  8. NUMERICAL SIMULATION AND OPTIMIZATION OF PERFORMANCES OF A SOLAR CELL BASED ON CdTe

    OpenAIRE

    A. M. Ferouani; M. R. Merad Boudia; K. Rahmoun

    2015-01-01

    This article has as an aim the study and the simulation of the photovoltaic cells containing CdTe materials, contributing to the development of renewable energies, and able to feed from the houses, the shelters as well as photovoltaic stations… etc. CdTe is a semiconductor having a structure of bands with an indirect gap of a value of 1,5 eV at ambient temperature what means that photon wavelength of approximately 1200 nm will be able to generate an electron-hole pair. One speaks about photog...

  9. Method in analysis of CdZnTe γ spectrum with artificial neural network

    International Nuclear Information System (INIS)

    Ai Xianyun; Wei Yixiang; Xiao Wuyun

    2005-01-01

    The analysis of gamma-ray spectra to identify lines and their intensities usually requires expert knowledge and time consuming calculations with complex fitting functions. CdZnTe detector often exhibits asymmetric peak shape particularly at high energies making peak fitting methods and sophisticated isotope identification programs difficult to use. This paper investigates the use of the neural network to process gamma spectra measured with CdZnTe detector to verify nuclear materials. Results show that the neural network method gives advantages, in particular, when large low-energetic peak tailings are observed. (authors)

  10. Determination of dispersion parameters of thermally deposited CdTe thin film

    Science.gov (United States)

    Dhimmar, J. M.; Desai, H. N.; Modi, B. P.

    2016-05-01

    Cadmium Telluride (CdTe) thin film was deposited onto glass substrates under a vacuum of 5 × 10-6 torr by using thermal evaporation technique. The prepared film was characterized for dispersion analysis from reflectance spectra within the wavelength range of 300 nm - 1100 nm which was recorded by using UV-Visible spectrophotometer. The dispersion parameters (oscillator strength, oscillator wavelength, high frequency dielectric constant, long wavelength refractive index, lattice dielectric constant and plasma resonance frequency) of CdTe thin film were investigated using single sellimeir oscillator model.

  11. Determination of dispersion parameters of thermally deposited CdTe thin film

    Energy Technology Data Exchange (ETDEWEB)

    Dhimmar, J. M., E-mail: bharatpmodi@gmail.com; Desai, H. N.; Modi, B. P. [Department of Physics, Veer Narmad South Gujarat University, Surat, Gujarat (India)

    2016-05-23

    Cadmium Telluride (CdTe) thin film was deposited onto glass substrates under a vacuum of 5 × 10{sup −6} torr by using thermal evaporation technique. The prepared film was characterized for dispersion analysis from reflectance spectra within the wavelength range of 300 nm – 1100 nm which was recorded by using UV-Visible spectrophotometer. The dispersion parameters (oscillator strength, oscillator wavelength, high frequency dielectric constant, long wavelength refractive index, lattice dielectric constant and plasma resonance frequency) of CdTe thin film were investigated using single sellimeir oscillator model.

  12. Facile aqueous synthesis and growth mechanism of CdTe nanorods

    International Nuclear Information System (INIS)

    Gong Haibo; Hao Xiaopeng; Gao Chang; Wu Yongzhong; Du Jie; Xu Xiangang; Jiang Minhua

    2008-01-01

    Single-crystal CdTe nanorods with diameters of 50-100 nm were synthesized under a surfactant-assisted hydrothermal condition. The experimental results indicated that with a temporal dependence the morphologies of CdTe nanocrystallites changed from nanoparticles to smooth surface nanorods. The crystal structure, morphology and optical properties of the products were investigated by x-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and fluorescence spectrophotometer. Furthermore, the formation mechanisms of the nanorods were investigated and discussed on the basis of the experimental results.

  13. Determination of dispersion parameters of thermally deposited CdTe thin film

    International Nuclear Information System (INIS)

    Dhimmar, J. M.; Desai, H. N.; Modi, B. P.

    2016-01-01

    Cadmium Telluride (CdTe) thin film was deposited onto glass substrates under a vacuum of 5 × 10 −6 torr by using thermal evaporation technique. The prepared film was characterized for dispersion analysis from reflectance spectra within the wavelength range of 300 nm – 1100 nm which was recorded by using UV-Visible spectrophotometer. The dispersion parameters (oscillator strength, oscillator wavelength, high frequency dielectric constant, long wavelength refractive index, lattice dielectric constant and plasma resonance frequency) of CdTe thin film were investigated using single sellimeir oscillator model.

  14. Recent Progress on Solution-Processed CdTe Nanocrystals Solar Cells

    OpenAIRE

    Hao Xue; Rongfang Wu; Ya Xie; Qiongxuan Tan; Donghuan Qin; Hongbin Wu; Wenbo Huang

    2016-01-01

    Solution-processed CdTe nanocrystals (NCs) photovoltaic devices have many advantages, both in commercial manufacture and daily operation, due to the low-cost fabrication process, which becomes a competitive candidate for next-generation solar cells. All solution-processed CdTe NCs solar cells were first reported in 2005. In recent years, they have increased over four-fold in power conversion efficiency. The latest devices achieve AM 1.5 G power conversion efficiency up to 12.0%, values compar...

  15. Theoretical investigation of Sn-doped Ge{sub 2}Sb{sub 2}Te{sub 5} alloy in crystalline phase

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Janpreet; Tripathi, S. K., E-mail: surya@pu.ac.in [Department of Physics, Center of Advanced Study in Physics, Panjab University, Chandigarh-160014 (India); Singh, Gurinder; Kaura, Aman [University Institute of Engineering and Technology Hoshiarpur-146001 (India)

    2015-06-24

    Ge{sub 2}Sb{sub 2}Te{sub 5} (GST) is technologically important for phase-change random access memory applications. It has been shown that the 2.2 atomic % doping of Sn weakens the Ge–Te bond strength while maintaining the symmetry of stable phase of GST. The influence of Sn doping upon the phase change characteristics of the crystalline GST alloy has been investigated by ab initio calculations. The lattice parameter, average interface distances between two adjacent (111) layers, equilibrium volume, metallic character and electrical resistance has been calculated for the stable phase of GST and Sn-doped GST.

  16. Magnetic quantum ratchet effect in (Cd,Mn)Te- and CdTe-based quantum well structures with a lateral asymmetric superlattice

    Science.gov (United States)

    Faltermeier, P.; Budkin, G. V.; Unverzagt, J.; Hubmann, S.; Pfaller, A.; Bel'kov, V. V.; Golub, L. E.; Ivchenko, E. L.; Adamus, Z.; Karczewski, G.; Wojtowicz, T.; Popov, V. V.; Fateev, D. V.; Kozlov, D. A.; Weiss, D.; Ganichev, S. D.

    2017-04-01

    We report on the observation of magnetic quantum ratchet effect in (Cd,Mn)Te- and CdTe-based quantum well structures with an asymmetric lateral dual grating gate superlattice subjected to an external magnetic field applied normal to the quantum well plane. A dc electric current excited by cw terahertz laser radiation shows 1 /B oscillations with an amplitude much larger as compared to the photocurrent at zero magnetic field. We show that the photocurrent is caused by the combined action of a spatially periodic in-plane potential and the spatially modulated radiation due to the near-field effects of light diffraction. Magnitude and direction of the photocurrent are determined by the degree of the lateral asymmetry controlled by the variation of voltages applied to the individual gates. The observed magneto-oscillations with enhanced photocurrent amplitude result from Landau quantization and, for (Cd,Mn)Te at low temperatures, from the exchange enhanced Zeeman splitting in diluted magnetic heterostructures. Theoretical analysis, considering the magnetic quantum ratchet effect in the framework of semiclassical approach, describes quite well the experimental results.

  17. 2p1v states populated in 135Te from 9Be induced reactions with a 132Sn beam

    Energy Technology Data Exchange (ETDEWEB)

    Allmond, James M [ORNL; Stuchbery, Andrew E [ORNL; Brown, Alex [National Superconducting Cyclotron Laboratory (NSCL), Michigan State University; Beene, James R [ORNL; Galindo-Uribarri, Alfredo {nmn} [ORNL; Gross, Carl J [ORNL; Liang, J Felix [ORNL; Padilla-Rodal, Elizabeth [Universidad Nacional Autonoma de Mexico (UNAM); Radford, David C [ORNL; Varner Jr, Robert L [ORNL; Ayres, A. [University of Tennessee, Knoxville (UTK); Batchelder, J. C. [Oak Ridge Associated Universities (ORAU); Bey, A. [University of Tennessee, Knoxville (UTK); Bingham, C. R. [University of Tennessee, Knoxville (UTK); Howard, Meredith E [ORNL; Jones, K. L. [University of Tennessee, Knoxville (UTK); Manning, Brett M [ORNL; Mueller, Paul Edward [ORNL; Nesaraja, Caroline D [ORNL; Pain, Steven D [ORNL; Peters, William A [ORNL; Ratkiewicz, Andrew J [ORNL; Schmitt, Kyle [University of Tennessee, Knoxville (UTK); Shapira, Dan [ORNL; Smith, Michael Scott [ORNL; Stone, N. J. [University of Tennessee, Knoxville (UTK); Stracener, Daniel W [ORNL; Yu, Chang-Hong [ORNL

    2014-01-01

    Gamma-ray transitions in $^{134}$\\textrm{Te}, $^{135}$\\textrm{Te}, and $^{136}$\\textrm{Te} were measured from $^{9}$\\textrm{Be} induced reactions with a radioactive $^{132}$\\textrm{Sn} beam at a sub-Coulomb barrier energy of $3$~MeV per nucleon using particle-$\\gamma$ coincidence spectroscopy. The transitions were selected by gating on alpha-like particles in a \\textrm{CsI} detector following a combination of ($^{9}$\\textrm{Be},$\\alpha 1n$), ($^{9}$\\textrm{Be},$\\alpha 2n$), and ($^{9}$\\textrm{Be},$\\alpha 3n$) reactions. Distorted wave Born approximation calculations suggest little to no contribution from the ($^{9}$\\textrm{Be},$^{7}$\\textrm{He}), ($^{9}$\\textrm{Be},$^{6}$\\textrm{He}), and ($^{9}$\\textrm{Be},$^{5}$\\textrm{He}) direct reactions. Gamma-ray transitions from previously known $2^+\\otimes \

  18. Photoelectric converters on Cr/x/Te/y/-Zn/x/Cd/1-x/S heterojunction

    Science.gov (United States)

    Konstantinova, E. M.; Stratieva, N. R.

    The layer properties of Zn(x)Cd(1-x)S(x) are are investigated, and the use of these materials in heterojunction photocells and convertors is evaluated. Results show that the calculated lattice mismatch of the semiconductor decreases with an increase of the Zn content in the solid solutions. A Cr(x)Te(y)-Zn(x)Cd(1-x)S heterojunction is fabricated and is found to have an increase in efficiency of 1% when the open-circuit voltage is raised by about 150 mV and the other parameters are held constant. The open-circuit voltage for photocells based on Cr(x)Te(y) and Zn(x)Cd(1-x)S, with x = 0.05-0.3, is measured under 80 mW/sq cm illumination, and is shown to be lower than the open circuit voltages for Cr(x)Te(y)-Zn(x) Cd(1-x)S samples. In addition, the I-V characteristics of the samples are determined. It is concluded that the wide spectral sensitivity, the high open-circuit voltage, as well as satisfactory conversion efficiencies, of solar cells based on Cr(x)Te(y)-Zn(x)Cd(1-x)S will allow the development of solar energy convertors with improved parameters.

  19. Comparison of Minority Carrier Lifetime Measurements in Superstrate and Substrate CdTe PV Devices: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Gessert, T. A.; Dhere, R. G.; Duenow, J. N.; Kuciauskas, D.; Kanevce, A.; Bergeson, J. D.

    2011-07-01

    We discuss typical and alternative procedures to analyze time-resolved photoluminescence (TRPL) measurements of minority carrier lifetime (MCL) with the hope of enhancing our understanding of how this technique may be used to better analyze CdTe photovoltaic (PV) device functionality. Historically, TRPL measurements of the fast recombination rate (t1) have provided insightful correlation with broad device functionality. However, we have more recently found that t1 does not correlate as well with smaller changes in device performance, nor does it correlate well with performance differences observed between superstrate and substrate CdTe PV devices. This study presents TRPL data for both superstrate and substrate CdTe devices where both t1 and the slower TRPL decay (t2) are analyzed. The study shows that changes in performance expected from small changes in device processing may correlate better with t2. Numerical modeling further suggests that, for devices that are expected to have similar drift field in the depletion region, effects of changes in bulk MCL and interface recombination should be more pronounced in t2. Although this technique may provide future guidance to improving CdS/CdTe device performance, it is often difficult to extract statistically precise values for t2, and therefore t2 data may demonstrate significant scatter when correlated with performance parameters.

  20. Development of SnS (FTO/CdS/SnS) thin films by nebulizer spray pyrolysis (NSP) for solar cell applications

    Science.gov (United States)

    Arulanantham, A. M. S.; Valanarasu, S.; Jeyadheepan, K.; Ganesh, V.; Shkir, Mohd

    2018-01-01

    Herein we report a well-organized analysis on various key-properties of SnS thin films for solar cell fabricated by nebulizer spray pyrolysis technique. X-ray diffraction study reveals the polycrystalline nature of deposited films with orthorhombic crystal structure. The crystallite size was calculated and observed to be in the range of 8-28 nm with increasing molarity of precursor solution. The stoichiometry composition of SnS was confirmed by EDX study. SEM/AFM studies divulge the well-covered deposited surface with spherical grains and the size of grains is increasing with concentration and so the roughness. A remarkable decrease in band gap from 2.6 eV to 1.6 eV was noticed by raising the molar concentration from 0.025 M up to 0.075 M. A single strong emission peak at about 825 nm is observed in PL spectra with enhanced intensity which may be attributed to near band edge emission. From the Hall effect measurement, it was found that the SnS thin film exhibits p-type conductivity. The calculated values of resistivity and carrier concentration are 0.729 Ω cm and 3.67 × 1018/cm3 respectively. Furthermore, to study the photovoltaic properties of SnS thin films a heterojunction solar cell, FTO/n-CdS/p-SnS was produced and the conversion efficiency was recorded about 0.01%.

  1. Reformulated tight binding calculation for band discontinuity at CdTe/Hg {sub x}Cd{sub 1-x}Te heterointerfaces and their type I-type III transitions

    Energy Technology Data Exchange (ETDEWEB)

    Ekpunobi, A.J. [Department of Physics and Industrial Physics, Nnamdi Azikiwe University, P.M.B. 5025, Awka, Anambra State (Nigeria)

    2005-02-25

    A recently reformulated tight binding method is used to calculate the valence band discontinuity at the CdTe/Hg {sub x}Cd{sub 1-x}Te interface in the s{sup 2}p{sup 2} configuration. The calculated valence band discontinuity of 0.31 eV at CdTe/HgTe interface is in good agreement with self-consistent calculation and accepted experimental value. Calculations were extended to alloy interfaces, which enabled the investigation of the band-offset problem at the transition point. Both valence band discontinuity ratio and conduction band discontinuity ratio show inflexions at the transition point.

  2. Switchable photoluminescence of CdTe nanocrystals by temperature-responsive microgels

    Czech Academy of Sciences Publication Activity Database

    Agrawal, M.; Rubio-Retama, J.; Zafeiropoulos, N. E.; Gaponik, N.; Gupta, S.; Cimrová, Věra; Lesnyak, V.; López-Cabarcos, E.; Tzavalas, S.; Rojas-Reyna, R.; Eychmuller, A.; Stamm, M.

    2008-01-01

    Roč. 24, č. 17 (2008), s. 9820-9824 ISSN 0743-7463 R&D Projects: GA AV ČR IAA4050409; GA MŠk(CZ) 1M06031 Institutional research plan: CEZ:AV0Z40500505 Keywords : switchable photoluminescence * temperature-responsive microgels * CdTe nanocrystals Subject RIV: CD - Macromolecular Chemistry Impact factor: 4.097, year: 2008

  3. Investigating the electronic properties of multi-junction ZnS/CdS/CdTe graded bandgap solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Olusola, O.I., E-mail: olajideibk@yahoo.com [Electronic Materials and Sensors Group, Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield S1 1WB (United Kingdom); Department of Physics, School of Science, The Federal University of Technology, Akure (FUTA), P.M.B. 704 (Nigeria); Madugu, M.L.; Dharmadasa, I.M. [Electronic Materials and Sensors Group, Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield S1 1WB (United Kingdom)

    2017-04-15

    The fabrication of multi-junction graded bandgap solar cells have been successfully implemented by electroplating three binary compound semiconductors from II-VI family. The three semiconductor materials grown by electroplating techniques are ZnS, CdS and CdTe thin films. The electrical conductivity type and energy bandgap of each of the three semiconductors were determined using photoelectrochemical (PEC) cell measurement and UV–Vis spectrophotometry techniques respectively. The PEC cell results show that all the three semiconductor materials have n-type electrical conductivity. These two material characterisation techniques were considered in this paper in order to establish the relevant energy band diagram for device results, analysis and interpretation. Solar cells with the device structure glass/FTO/n-ZnS/n-CdS/n-CdTe/Au were then fabricated and characterised using current-voltage (I-V) and capacitance-voltage (C-V) techniques. From the I-V characteristics measurement, the fabricated device structures yielded an open circuit voltage (V{sub oc}) of 670 mV, short circuit current density (J{sub sc}) of 41.5 mA cm{sup −2} and fill-factor (FF) of 0.46 resulting in ∼12.8% efficiency when measured at room temperature under AM1.5 illumination conditions. The device structure showed an excellent rectification factor (RF) of 10{sup 4.3} and ideality factor (n) of 1.88. The results obtained from the C-V measurement also showed that the device structures have a moderate doping level of 5.2 × 10{sup 15} cm{sup −3}. - Highlights: • Electroplating of n-ZnS, n-CdS and n-CdTe binary compound semiconductors. • Fabrication of Schottky barrier solar cells from glass/FTO/n-ZnS/n-CdS/n-CdTe/Au. • Development of multi-junction graded bandgap solar cells using n-n-n structures.

  4. Effect of microwave treatment on the luminescence properties of CdS and CdTe:Cl Single Crystals

    International Nuclear Information System (INIS)

    Red’ko, R. A.; Budzulyak, S. I.; Korbutyak, D. V.; Lotsko, A. P.; Vakhnyak, N. D.; Demchyna, L. A.; Kalytchuk, S. M.; Konakova, R. V.; Milenin, V. V.; Bykov, Yu. V.; Egorov, S. V.; Eremeev, A. G.

    2015-01-01

    The effect of microwave radiation on the luminescence properties of CdS and CdTe:Cl single crystals is studied. It is established that the exposure of these semiconductors to short-term (≤30 s) microwave radiation substantially modifies their impurity and defect structure. The mechanisms of transformation of the defect subsystem of II–VI single crystals upon microwave treatment are discussed. It is shown that the experimentally observed changes are defined by the nonthermal effects of microwave radiation at a power density of 7.5 W cm –2 ; at 90 W cm –2 , nonthermal effects are prevailing

  5. Cancer Cell Targeting Using Folic Acid/Anti-HER2 Antibody Conjugated Fluorescent CdSe/CdS/ZnS-Mercaptopropionic Acid and CdTe-Mercaptosuccinic Acid Quantum Dots.

    Science.gov (United States)

    Singh, Gurpal; Kumar, Manoj; Soni, Udit; Arora, Vikas; Bansal, Vivek; Gupta, Dikshi; Bhat, Madhusudan; Dinda, Amit K; Sapra, Sameer; Singh, Harpal

    2016-01-01

    CdSe/CdS/ZnS and CdTe quantum dots (QDs) were synthesized by successive ion layer adsorption and reaction (SILAR) technique and direct aqueous synthesis respectively using thiol stabilizers. Synthesized CdSe/CdS/ZnS and CdTe QDs stabilized with 3-mercaptopropionic acid (MPA) and mercaptosuccinic acid (MSA) were used as fluorescent labels after conjugation with folic acid (FA) and anti-HER2 antibodies. Photoluminescence quantum yield of folated CdSe/CdS/ZnS-MPA and CdTe-MSA QDs was 59% and 77% than that of non-folated hydrophilic QDs. The folate receptor-mediated delivery of folic acid-conjugated CdTe-MSA and CdSe/CdS/ZnS-MPA QDs showed higher cellular internalization as observed by confocal laser scanning microscopic studies. Folated and non-folated CdTe-MSA QDs were highly toxic and exhibited only 10% cell viability as compared to > 80% cell viability with CdSe/CdS/ZnS-MPA QDs over the concentration ranging from 3.38 to 50 pmoles. Immunohistochemistry (IHC) results of human breast cancer tissue samples showed positive results with anti-HER2 antibody conjugated CdSe/CdS/ZnS-MPA QDs with better sensitivity and specificity as compared to conventional IHC analysis using diaminobenzedene staining.

  6. Silk fibroin linked Zn/Cd-doped SnO2 nanoparticles to purify the organically polluted water

    Science.gov (United States)

    Bhuvaneswari, K.; Divya Bharathi, R.; Pazhanivel, T.

    2018-02-01

    Photocatalytic degradation of toxic organic pollutant is a challenging tasks for environmental protection. Recently most of the researchers are focusing on metal oxide semiconductors, such as TiO2, ZnO, and SnO2 as efficient photocatalysts for photocatalytic degradation of organic pollutant. In this regard, we are eager to increase the photocatalytic activity with the help of organic molecule (Silk Fibroin (SF)). Metal oxides are attached on the surface of SF with the help of polyvinyl alcohol (PVA). In this present work, pure SnO2, (Cd/Zn) doped SnO2 and SF linked nanoparticles have been successfully synthesized by microwave technique. The synthesized samples were investigated by XRD, FTIR and UV-DRS techniques. The surface morphology of all the samples were investigated by FESEM analysis. Photocatalytic activities of Cd doped SnO2 nanoparticles and SF attached Cd/Zn doped SnO2 nanoparticles were studied on methylene blue (MB) dye under UV–vis light illumination.

  7. High efficiency thin film CdTe and a-Si based solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Compaan, A. D.; Deng, X.; Bohn, R. G.

    2000-01-04

    This report describes work done by the University of Toledo during the first year of this subcontract. During this time, the CdTe group constructed a second dual magnetron sputter deposition facility; optimized reactive sputtering for ZnTe:N films to achieve 10 ohm-cm resistivity and {approximately}9% efficiency cells with a copper-free ZnTe:N/Ni contact; identified Cu-related photoluminescence features and studied their correlation with cell performance including their dependence on temperature and E-fields; studied band-tail absorption in CdS{sub x}Te{sub 1{minus}x} films at 10 K and 300 K; collaborated with the National CdTe PV Team on (1) studies of high-resistivity tin oxide (HRT) layers from ITN Energy Systems, (2) fabrication of cells on the HRT layers with 0, 300, and 800-nm CdS, and (3) preparation of ZnTe:N-based contacts on First Solar materials for stress testing; and collaborated with Brooklyn College for ellipsometry studies of CdS{sub x}Te{sub 1{minus}x} alloy films, and with the University of Buffalo/Brookhaven NSLS for synchrotron X-ray fluorescence studies of interdiffusion in CdS/CdTe bilayers. The a-Si group established a baseline for fabricating a-Si-based solar cells with single, tandem, and triple-junction structures; fabricated a-Si/a-SiGe/a-SiGe triple-junction solar cells with an initial efficiency of 9.7% during the second quarter, and 10.6% during the fourth quarter (after 1166 hours of light-soaking under 1-sun light intensity at 50 C, the 10.6% solar cells stabilized at about 9%); fabricated wide-bandgap a-Si top cells, the highest Voc achieved for the single-junction top cell was 1.02 V, and top cells with high FF (up to 74%) were fabricated routinely; fabricated high-quality narrow-bandgap a-SiGe solar cells with 8.3% efficiency; found that bandgap-graded buffer layers improve the performance (Voc and FF) of the narrow-bandgap a-SiGe bottom cells; and found that a small amount of oxygen partial pressure ({approximately}2 {times} 10

  8. Characterization of CBD-CdS layers with different S/Cd ratios in the chemical bath and their relation with the efficiency of CdS/CdTe solar cells

    International Nuclear Information System (INIS)

    Vigil-Galan, O.; Morales-Acevedo, A.; Cruz-Gandarilla, F.; Jimenez-Escamilla, M.G.; Aguilar-Hernandez, J.; Contreras-Puente, G.; Sastre-Hernandez, J.; Sanchez-Meza, E.; Ramon-Garcia, M.L.

    2007-01-01

    In previous papers we have reported the improvement of the efficiency of CdS/CdTe solar cells by varying the thiourea/CdCl 2 ratio (R tc ) in the chemical bath solution used for the deposition of the CdS layers. In this work, a more complete study concerning the physical properties of Chemical Bath Deposited (CBD) CdS layers studied by photoluminescence, X-ray diffraction and optical spectroscopy are correlated to the I-V characteristics under AM 1.5 sunlight and the spectral response of CdS/CdTe solar cells. It is confirmed that the optimum R tc for the CBD CdS films is R tc = 5, since in this case the best solar cells were obtained and these films show the better optical and structural characteristics

  9. Elaboration of fabrication technology of ITO/CdS/CdTe solar cells on flexible polymer substrates

    International Nuclear Information System (INIS)

    Potlog, T.; Spalatu, N.; Capros, N.

    2007-01-01

    The development of high efficiency, stable, lightweight and flexible solar cell is important for terrestrial and space applications. We have developed a novel process to make solar cells on flexible polymer sheets. A thin layer of CdTe compound semiconductor is used for the absorption of solar light and generation of electrical current. In this work the solar electricity conversion efficiency of 4,66% is the highest efficiency reported for a solar cell grown on a polymer sheet. (authors)

  10. Photoluminescence of CdTe nanocrystals grown by pulsed laser ablation on a template of Si nanoparticles

    International Nuclear Information System (INIS)

    Guillen-Cervantes, A.; Silva-Lopez, H.; Becerril-Silva, M.; Arias-Ceron, J.S.; Campos-Gonzalez, E.; Zelaya-Angel, O.; Medina-Torres, A.C.

    2015-01-01

    CdTe nanocrystals were grown on eroded Si (111) substrates at room temperature by pulsed laser ablation. Before growth, Si substrates were subjected to different erosion time in order to investigate the effect on the CdTe samples. The erosion process consists of exposition to a pulsed high-voltage electric arc. The surface consequence of the erosion process consists of Si nanoparticles which acted as a template for the growth of CdTe nanocrystals. CdTe samples were studied by X-ray diffraction (XRD), room temperature photoluminescence (RT PL) and high-resolution transmission electron microscopy (HRTEM). CdTe nanocrystals grew in the stable cubic phase, according to XRD spectra. A strong visible emission was detected in photoluminescence (PL) experiments. The PL signal was centered at 540 nm (∝2.34 eV). With the effective mass approximation, the size of the CdTe crystals was estimated around 3.5 nm. HRTEM images corroborated the physical characteristics of CdTe nanocrystals. These results could be useful for the development of CdTe optoelectronic devices. (orig.)

  11. Enhanced glutathione content allows the in vivo synthesis of fluorescent CdTe nanoparticles by Escherichia coli.

    Directory of Open Access Journals (Sweden)

    Juan P Monrás

    Full Text Available The vast application of fluorescent semiconductor nanoparticles (NPs or quantum dots (QDs has prompted the development of new, cheap and safer methods that allow generating QDs with improved biocompatibility. In this context, green or biological QDs production represents a still unexplored area. This work reports the intracellular CdTe QDs biosynthesis in bacteria. Escherichia coli overexpressing the gshA gene, involved in glutathione (GSH biosynthesis, was used to produce CdTe QDs. Cells exhibited higher reduced thiols, GSH and Cd/Te contents that allow generating fluorescent intracellular NP-like structures when exposed to CdCl(2 and K(2TeO(3. Fluorescence microscopy revealed that QDs-producing cells accumulate defined structures of various colors, suggesting the production of differently-sized NPs. Purified fluorescent NPs exhibited structural and spectroscopic properties characteristic of CdTe QDs, as size and absorption/emission spectra. Elemental analysis confirmed that biosynthesized QDs were formed by Cd and Te with Cd/Te ratios expected for CdTe QDs. Finally, fluorescent properties of QDs-producing cells, such as color and intensity, were improved by temperature control and the use of reducing buffers.

  12. The growth of various buffer layer structures and their influence on the quality of (CdHg)Te epilayers

    CSIR Research Space (South Africa)

    Gouws, GJ

    1993-05-01

    Full Text Available The suitability of various buffer layer structures on (100) GaAs for (CdHg)Te growth by organometallic vapour phase epitaxy (OMVPE) was investigated. The preferred epitaxial orientation of (100) GaAs/ (lll) CdTe was found to be unsuitable due...

  13. Epitaxial growth of CdTe thin film on cube-textured Ni by metal-organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gaire, C. [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY, 12180-3590 (United States); Rao, S. [Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180-3590 (United States); Riley, M. [Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180-3590 (United States); Chen, L. [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY, 12180-3590 (United States); Goyal, A. [Oak Ridge National Lab, Oak ridge, TN, 37831-6116 (United States); Lee, S. [US Army ARDEC Benet Labs, Watervliet, NY, 12189-4050 (United States); Bhat, I. [Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180-3590 (United States); Lu, T.-M. [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY, 12180-3590 (United States); Wang, G.-C., E-mail: wangg@rpi.edu [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY, 12180-3590 (United States)

    2012-01-01

    Single crystal-like CdTe thin film has been grown by metalorganic chemical vapor deposition on cube-textured Ni(100) substrate. Using X-ray pole figure measurements we observed the epitaxial relationship of {l_brace}111{r_brace}{sub CdTe}//{l_brace}001{r_brace}{sub Ni} with [11{sup Macron }0]{sub CdTe}//[010]{sub Ni} and [112{sup Macron }] {sub CdTe}//[100]{sub Ni}. The 12 diffraction peaks in the (111) pole figure of CdTe film and their relative positions with respect to the four peak positions in the (111) pole figure of Ni substrate are consistent with four equivalent orientational domains of CdTe with three to four superlattice match of about 1.6% in the [11{sup Macron }0] direction of CdTe and the [010] direction of Ni. The electron backscattered diffraction images show that the CdTe domains are 30 Degree-Sign oriented from each other. These high structural quality films may find applications in low cost optoelectronic devices.

  14. Selective optosensing of clenbuterol and melamine using molecularly imprinted polymer-capped CdTe quantum dots.

    Science.gov (United States)

    The Huy, Bui; Seo, Min-Ho; Zhang, Xinfeng; Lee, Yong-Ill

    2014-07-15

    A novel procedure for the optosensing of clenbuterol and melamine was developed using molecularly imprinted polymer-capped CdTe quantum dots (MIP-CdTe QDs). The MIP-CdTe QDs were synthesized by a radical polymerization process among CdTe QDs, a template, 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS). The sizes of the MIP-CdTe particles were controlled by the speed of polymerization, concentration of the template, concentration of the quantum dots, and the ratio of template, monomer and cross-linker. Excellent selectivity and high sensitivity of MIP-CdTe QDs toward clenbuterol/melamine molecules were observed based on the fluorescence quenching of QDs. Experimental results showed that the optimum molar ratios of template, monomer, and cross-linker were 1:8:20 and 1:4:20 for analyzing clenbuterol and melamine, respectively. Under optimum conditions, these MIP-CdTe QDs showed a limit of detection of 0.4 μM (120 ng/mL) for clenbuterol and 0.6 μM (75 ng/mL) for melamine. The feasibility of the developed method in real samples was successfully evaluated through the analysis of clenbuterol and melamine in milk and liver samples with satisfactory recoveries of 92-97%. The MIP-CdTe QDs could be easily regenerated for subsequent sample analysis with water. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Photoluminescence of CdTe nanocrystals grown by pulsed laser ablation on a template of Si nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Guillen-Cervantes, A.; Silva-Lopez, H.; Becerril-Silva, M.; Arias-Ceron, J.S.; Campos-Gonzalez, E.; Zelaya-Angel, O. [CINVESTAV-IPN, Physics Department, Apdo. Postal 14-740, Mexico (Mexico); Medina-Torres, A.C. [Escuela Superior de Fisica y Matematicas del IPN, Mexico (Mexico)

    2014-11-12

    CdTe nanocrystals were grown on eroded Si (111) substrates at room temperature by pulsed laser ablation. Before growth, Si substrates were subjected to different erosion time in order to investigate the effect on the CdTe samples. The erosion process consists of exposition to a pulsed high-voltage electric arc. The surface consequence of the erosion process consists of Si nanoparticles which acted as a template for the growth of CdTe nanocrystals. CdTe samples were studied by X-ray diffraction (XRD), room temperature photoluminescence (RT PL) and high-resolution transmission electron microscopy (HRTEM). CdTe nanocrystals grew in the stable cubic phase, according to XRD spectra. A strong visible emission was detected in photoluminescence (PL) experiments. The PL signal was centered at 540 nm (∝2.34 eV). With the effective mass approximation, the size of the CdTe crystals was estimated around 3.5 nm. HRTEM images corroborated the physical characteristics of CdTe nanocrystals. These results could be useful for the development of CdTe optoelectronic devices. (orig.)

  16. Stimulated emission from HgCdTe quantum well heterostructures at wavelengths up to 19.5 μm

    Science.gov (United States)

    Morozov, S. V.; Rumyantsev, V. V.; Fadeev, M. A.; Zholudev, M. S.; Kudryavtsev, K. E.; Antonov, A. V.; Kadykov, A. M.; Dubinov, A. A.; Mikhailov, N. N.; Dvoretsky, S. A.; Gavrilenko, V. I.

    2017-11-01

    We report on stimulated emission at wavelengths up to 19.5 μm from HgTe/HgCdTe quantum well heterostructures with wide-gap HgCdTe dielectric waveguide, grown by molecular beam epitaxy on GaAs(013) substrates. The mitigation of Auger processes in structures under study is exemplified, and the promising routes towards the 20-50 μm wavelength range, where HgCdTe lasers may be competitive to the prominent emitters, are discussed.

  17. Structural, electronic and optical properties of ilmenite and perovskite CdSnO{sub 3} from DFT calculations

    Energy Technology Data Exchange (ETDEWEB)

    Sesion Jr, P D [Escola de Ciencias e Tecnologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, Rio Grande do Norte (Brazil); Henriques, J M [Departamento de Fisica Teorica e Experimental, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, Rio Grande do Norte (Brazil); Barboza, C A; Albuquerque, E L [Departamento de Biofisica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-900 Natal, Rio Grande do Norte (Brazil); Freire, V N [Departamento de Fisica, Universidade Federal do Ceara, 60455-970 Fortaleza, Ceara (Brazil); Caetano, E W S, E-mail: ewcaetano@gmail.co [Instituto Federal de Educacao, Ciencia e Tecnologia do Ceara, Avenida 13 de Maio, 2081, Benfica, 60040-531 Fortaleza, Ceara (Brazil)

    2010-11-03

    CdSnO{sub 3} ilmenite and perovskite crystals were investigated using both the local density and generalized gradient approximations, LDA and GGA, respectively, of the density functional theory (DFT). The electronic band structures, densities of states, dielectric functions, optical absorption and reflectivity spectra related to electronic transitions were obtained, as well as the infrared absorption spectra after computing the vibrational modes of the crystals at q = 0. Dielectric optical permittivities and polarizabilities at {omega} = 0 and {infinity} were also calculated. The results show that GGA-optimized geometries are more accurate than LDA ones, and the Kohn-Sham band structures obtained for the CdSnO{sub 3} polymorphs confirm that ilmenite has an indirect band gap, while perovskite has a direct band gap, both being semiconductors. Effective masses for both crystals are obtained for the first time, being highly isotropic for electrons and anisotropic for holes. The optical properties reveal a very small degree of anisotropy of both crystals with respect to different polarization planes of incident light. The phonon calculation at q = 0 for perovskite CdSnO{sub 3} does not show any imaginary frequencies, in contrast to a previous report suggesting the existence of a more stable crystal of perovskite CdSnO{sub 3} with ferroelectric properties.

  18. Improved power conversion efficiency for bulk heterojunction solar cells incorporating CdTe-CdSe nanoheterostructure acceptors and a conjugated polymer donor

    Energy Technology Data Exchange (ETDEWEB)

    Dayal, Smita; Zhong, Haizheng; Kopidakis, Nikos; Scholes, Gregory D.; Rumbles, Garry

    2015-03-24

    In this paper, we report photovoltaic devices based on composites of a branched nanoheterostructure containing a CdTe core and CdSe arms, CdTe(c)-CdSe(a), combined with either poly(3-hexylthiophene), P3HT, or poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)], PCPDTBT, with solar power conversion efficiencies of 1.2% and 1.8%, respectively. Finally, a comparison with previously reported composite devices of a related branched nanoheterostructure: CdSe(c)-CdTe(a) reveals an improved device performance that is attributed to a better electron percolation pathway provided by the dominant, higher electron affinity CdSe arms of the nanoheterostructures.

  19. CdTe/CZT under high flux irradiation

    International Nuclear Information System (INIS)

    Strassburg, Matthias; Schroeter, Christian; Hackenschmied, Peter

    2011-01-01

    Direct converting quantum counting detectors based on cadmium telluride and cadmium zinc telluride have been investigated with respect to their properties under intense X-ray irradiation. To derive a detailed picture of the performance of such detectors, the influence of the electric field, the detector thickness, the temperature and the intensity of the X-ray irradiation was studied. The results are discussed in terms of the ''polarization'' phenomenon, a reduction of the electric field strength inside the detector due to immobile charge carriers accumulating during irradiation. Furthermore, the impact of Te-inclusions and -precipitates is presented.

  20. Characteristics of HgCdTe epilayer grown by LPE using horizontal ...

    Indian Academy of Sciences (India)

    Unknown

    (i) the compensation of Hg loss from growth solution, by providing an additional Hg-vapour source in the form ... the substrate is removed from solution after growth ensuring a better wipe-off. 5 g of growth compound ( ... constituents Hg, Cd and Te takes place upon annealing improving the homogeneity of the epilayer giving ...

  1. Overcoming degradation mechanisms in CdTe solar cells: First annual report, August 1998--August 1999

    Energy Technology Data Exchange (ETDEWEB)

    Cahen, D.; Gartsman, K.; Hodes, G.; Rotlevy, O.; Visoly-Fisher, I,; Dobson, K.

    2000-02-28

    The authors have studied the importance of chemical processes for the stability of CdTe solar cells, in particular, diffusion in the ohmic contact/absorber junction regions. Both whole cells and test systems containing only the ohmic contact and the absorber are used. They found several experimental methods to be useable tools to follow the effects of impurity diffusion on the CdTe grain boundaries, grain bulk, and surface. In addition, they have explored alternative contacting schemes. The first year of activities led to the following tentative conclusions: Grain boundaries in CdTe/CdS cells are NOT fully passivated and are expected to be electrically active; There appears to be fast ionic diffusion in the vicinity of the Cu/HgTe/graphite back-contact, possibly enhanced by grain boundary diffusion; The macroscopic response to stress is different for cells with identical back-contact, but from different manufacturers. Different factors and/or different reactions to identical factors are possibly at work here; and Ni-P appears to be a promising back-contact material.

  2. ZnS shell growth on thiol capped CdTe quantum dots using gamma irradiation

    Science.gov (United States)

    Raju, S. P.; Hareesh, K.; Pai, S. Chethan; Dhole, S. D.; Sanjeev, Ganesh

    2017-05-01

    The formation of ZnS shell on 3-Mercaptopropionic acid (MPA) capped CdTe quantum dots (QDs) using gamma radiation has been reported in this study. Hydrothermally synthesized CdTe QDs were exposed to gamma radiation before and after introducing shell source materials (Zn+MPA complex). The gamma rays exposed samples were characterized using UV-Vis spectroscopy, Photoluminescence spectroscopy (PL) and X-Ray Diffraction (XRD) techniques. The redshift in absorption spectra for gamma irradiated samples indicates the formation of bigger nanoparticles as the shell stretched the core size. The shift in the XRD peaks (cubic zinc blade structure) towards higher angle reveals the formation of MPA capped CdTe/ZnS core/shell QDs against gamma radiation. The variation in PL spectra also followed the same redshift corroborating the UV-Vis and XRD results. The increase in PL intensity only after introducing shell source material against gamma radiation clearly confirms ZnS shell saturated the surface dangling bonds by increasing radiative decay mechanism over CdTe core surface.

  3. Diagnostic X-ray spectrometry using a commercial CdZnTe detector

    International Nuclear Information System (INIS)

    Becker, P.H.B.

    1998-01-01

    X ray spectrometry using Ge or Si detectors is an established tool to measure characterization parameters of X-ray beams. This work describes how a commercial CdZnTe was used to perform diagnostic X-ray spectrometry. Spectra were measured for two X-ray machines and compared with similar data found in the literature with an agreement of 2% rms

  4. Fabrication and performance of p-i-n CdTe radiation detectors

    CERN Document Server

    Niraula, M; Aoki, T; Tomita, Y; Nihashi, T; Hatanaka, Y

    1999-01-01

    We report on the fabrication and performance of CdTe radiation detectors in a new p-i-n structure which helps to reduce the leakage current to a minimum level. Chlorine-doped single-crystal CdTe substrates having resistivity in the order of 10 sup 9 OMEGA cm were used in this study. Iodine-doped n-type CdTe layers were grown homoepitaxially on one face of each crystals using the hydrogen plasma-radical-assisted metalorganic chemical vapor deposition technique at low substrate temperature of 150 deg. C. Indium electrode was evaporated on the n-CdTe side while a gold electrode on the opposite side acted as a p-type contact. Detectors thus fabricated exhibited low leakage current (below 0.4 nA/mm sup 2 at 250 V applied reverse bias for the best one) and good performance at room temperature. Spectral response of the detectors showed improved energy resolution for Am-241, Co-57, and Cs-137 radioisotopes. Detectors were further tested with X-ray photons of different intensities for their potential application in im...

  5. Temperature dependence of dc photoconductivity in CdTe thin films

    Indian Academy of Sciences (India)

    Therefore, it clearly supports the non-existence of physical barrier at CdTe ... presence of potential surface barrier at the electrode–film interface. ... Pradip Kumar Kalita clearly indicates the increase in density of grain boundary states as reported in earlier communication [12]. In these smaller grained films, therefore, the ...

  6. A pixellated gamma-camera based on CdTe detectors clinical interests and performances

    CERN Document Server

    Chambron, J; Eclancher, B; Scheiber, C; Siffert, P; Hage-Ali, M; Regal, R; Kazandjian, A; Prat, V; Thomas, S; Warren, S; Matz, R; Jahnke, A; Karman, M; Pszota, A; Németh, L

    2000-01-01

    A mobile gamma camera dedicated to nuclear cardiology, based on a 15 cmx15 cm detection matrix of 2304 CdTe detector elements, 2.83 mmx2.83 mmx2 mm, has been developed with a European Community support to academic and industrial research centres. The intrinsic properties of the semiconductor crystals - low-ionisation energy, high-energy resolution, high attenuation coefficient - are potentially attractive to improve the gamma-camera performances. But their use as gamma detectors for medical imaging at high resolution requires production of high-grade materials and large quantities of sophisticated read-out electronics. The decision was taken to use CdTe rather than CdZnTe, because the manufacturer (Eurorad, France) has a large experience for producing high-grade materials, with a good homogeneity and stability and whose transport properties, characterised by the mobility-lifetime product, are at least 5 times greater than that of CdZnTe. The detector matrix is divided in 9 square units, each unit is composed ...

  7. The role of substrate surface alteration in the fabrication of vertically aligned CdTe nanowires

    International Nuclear Information System (INIS)

    Neretina, S; Devenyi, G A; Preston, J S; Mascher, P; Hughes, R A; Sochinskii, N V

    2008-01-01

    Previously we have described the deposition of vertically aligned wurtzite CdTe nanowires derived from an unusual catalytically driven growth mode. This growth mode could only proceed when the surface of the substrate was corrupted with an alcohol layer, although the role of the corruption was not fully understood. Here, we present a study detailing the remarkable role that this substrate surface alteration plays in the development of CdTe nanowires; it dramatically improves the size uniformity and largely eliminates lateral growth. These effects are demonstrated to arise from the altered surface's ability to limit Ostwald ripening of the catalytic seed material and by providing a surface unable to promote the epitaxial relationship needed to sustain a lateral growth mode. The axial growth of the CdTe nanowires is found to be exclusively driven through the direct impingement of adatoms onto the catalytic seeds leading to a self-limiting wire height associated with the sublimation of material from the sidewall facets. The work presented furthers the development of the mechanisms needed to promote high quality substrate-based vertically aligned CdTe nanowires. With our present understanding of the growth mechanism being a combination of selective area epitaxy and a catalytically driven vapour-liquid-solid growth mode, these results also raise the intriguing possibility of employing this growth mode in other material systems in an effort to produce superior nanowires

  8. Enhancement in microstructural and optoelectrical properties of thermally evaporated CdTe films for solar cells

    Science.gov (United States)

    Chander, Subhash; Dhaka, M. S.

    2018-03-01

    The optimization of microstructural and optoelectrical properties of a thin layer is an important step prior device fabrication process, so an enhancement in these properties of thermally evaporated CdTe thin films is reported in this communication. The films having thickness 450 nm and 850 nm were deposited on thoroughly cleaned glass and indium tin oxide (ITO) substrates followed by annealing at 450 °C in air atmosphere. These films were characterized for microstructural and optoelectrical properties employing X-ray diffraction, scanning electron microscopy coupled with energy-dispersive spectroscopy, UV-Vis spectrophotometer and source meter. The films found to be have zinc-blende cubic structure with preferred reflection (111) while the crystallographic parameters and direct energy band gap are strongly influenced by the film thickness. The surface morphology studies show that the films are uniform, smooth, homogeneous and nearly dense-packed as well as free from voids and pitfalls as where elemental analysis revealed the presence of Cd and Te element in the deposited films. The electrical analysis showed linear behavior of current with voltage while conductivity is decreased for higher thickness. The results show that the microstructural and optoelectrical properties of CdTe thin layer could be enhanced by varying thickness and films having higher thickness might be processed as promising absorber thin layer to the CdTe-based solar cells.

  9. Investigation of deep level defects in CdTe thin films

    Energy Technology Data Exchange (ETDEWEB)

    Shankar, H.; Castaldini, A. [Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy); Dieguez, E.; Rubio, S. [Crystal Growth Lab, Department of Materials Physics, Faculty of Science, University Autonoma of Madrid, Ciudad Universitaria de Cantoblanco, 28049, Madrid (Spain); Dauksta, E.; Medvid, A. [Institute of Technical Physics, Riga Technical University, 14 Azenes Str, Riga, Latvia, Department of Materials (Latvia); Cavallini, A. [Department of Physics and Astronomy,University of Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy)

    2014-02-21

    In the past few years, a large body of work has been dedicated to CdTe thin film semiconductors, as the electronic and optical properties of CdTe nanostructures make them desirable for photovoltaic applications. The performance of semiconductor devices is greatly influenced by the deep levels. Knowledge of parameters of deep levels present in as-grown materials and the identification of their origin is the key factor in the development of photovoltaic device performance. Photo Induced Current Transient Spectroscopy technique (PICTS) has proven to be a very powerful method for the study of deep levels enabling us to identify the type of traps, their activation energy and apparent capture cross section. In the present work, we report the effect of growth parameters and LASER irradiation intensity on the photo-electric and transport properties of CdTe thin films prepared by Close-Space Sublimation method using SiC electrical heating element. CdTe thin films were grown at three different source temperatures (630, 650 and 700 °C). The grown films were irradiated with Nd:YAG LASER and characterized by Photo-Induced Current Transient Spectroscopy, Photocurrent measurementand Current Voltage measurements. The defect levels are found to be significantly influenced by the growth temperature.

  10. Studies on interaction between CdTe quantum dots and α ...

    Indian Academy of Sciences (India)

    Administrator

    Fluorescence spectra were measured with a LS-55 (Perkin-Elmer,. USA) spectrofluorimeter equipped with a xenon .... Stern–Volmer dynamic quenching constant and the concentration of quencher CdTe, respectively, kq is ... again that the quenching is not caused by dynamic collision but from the formation of a complex.

  11. Performance of CdZnTe coplanar-grid gamma-ray detectors

    International Nuclear Information System (INIS)

    Luke, P.N.; Eissler, E.E.

    1995-11-01

    CdZnTe crystals grown using the high-pressure Bridgman method exhibit many properties that are desirable for radiation detector fabrication, such as high resistivity, stable operation, relative ease of processing, and the availability of large volume crystals. However, as is common with other compound semi-conductor materials, currently available CdZnTe crystals have poor charge transport characteristics. This seriously the spectral performance of detectors, especially in gamma-ray detection. The coplanar-grid detection technique was recently developed to address such charge collection problems. This technique was first demonstrated using a 5 mm cube CdZnTe detector, and a dramatic improvement in spectral response has been achieved. These early results verified the effectiveness of this technique and suggested that large-volume gamma-ray detectors with high energy resolution can be realized. To further the development of such detectors, it is important to understand the various factors that affect detector performance. The purpose of this paper is to examine the effects of material properties on the spectral performance of CdZnTe coplanar-grid detectors. Theoretical spectral response is to show the level of performance that can be achieved given the typical carrier mobility-lifetime (μτ) properties of present-day materials. Nonuniformity in the charge transport properties of the material, which could limit the energy resolution of the detectors, has been studied experimentally and some of the results are presented here

  12. Low-temperature photoluminescence analysis of CdTeSe crystals for radiation-detector applications

    Energy Technology Data Exchange (ETDEWEB)

    YANG G.; Roy, U. N.; Bolotnikov, A. E.; Cui, Y.; Camarda, G.S.; Hossain, A.; and James, R. B.

    2015-10-05

    Goal: Understanding the changes of material defects in CdTeSe following annealing. Experimental results and discussions: Infrared (IR) transmission microscopy; current-voltage measurements (Highlight: Improvement of resistivity of un-doped crystals after annealing); low-temperature photoluminescence (PL) spectrum of as-grown and annealed samples.

  13. Studies on interaction between CdTe quantum dots and α ...

    Indian Academy of Sciences (India)

    Administrator

    Studies on interaction between CdTe quantum dots and α-chymotrypsin by molecular spectroscopy. JIANNIAO TIAN. 1. , SHENGZHI WEI. 1. , YANCHUN ZHAO. 1. , RONGJUN LIU. 1 and. SHULIN ZHAO. 2. 1. Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources. (Guangxi Normal University) ...

  14. Time resolution improvement of Schottky CdTe PET detectors using digital signal processing

    International Nuclear Information System (INIS)

    Nakhostin, M.; Ishii, K.; Kikuchi, Y.; Matsuyama, S.; Yamazaki, H.; Torshabi, A. Esmaili

    2009-01-01

    We present the results of our study on the timing performance of Schottky CdTe PET detectors using the technique of digital signal processing. The coincidence signals between a CdTe detector (15x15x1 mm 3 ) and a fast liquid scintillator detector were digitized by a fast digital oscilloscope and analyzed. In the analysis, digital versions of the elements of timing circuits, including pulse shaper and time discriminator, were created and a digital implementation of the Amplitude and Rise-time Compensation (ARC) mode of timing was performed. Owing to a very fine adjustment of the parameters of timing measurement, a good time resolution of less than 9.9 ns (FWHM) at an energy threshold of 150 keV was achieved. In the next step, a new method of time pickoff for improvement of timing resolution without loss in the detection efficiency of CdTe detectors was examined. In the method, signals from a CdTe detector are grouped by their rise-times and different procedures of time pickoff are applied to the signals of each group. Then, the time pickoffs are synchronized by compensating the fixed time offset, caused by the different time pickoff procedures. This method leads to an improved time resolution of ∼7.2 ns (FWHM) at an energy threshold of as low as 150 keV. The methods presented in this work are computationally fast enough to be used for online processing of data in an actual PET system.

  15. Arsenic complexes optical signatures in As-doped HgCdTe

    International Nuclear Information System (INIS)

    Gemain, F.; Robin, I. C.; Brochen, S.; Ballet, P.; Gravrand, O.; Feuillet, G.

    2013-01-01

    In this paper, the optical signatures of arsenic complexes in As-doped HgCdTe samples grown by molecular beam epitaxy are clearly identified using comparison between photoluminescence spectra, Extended X-Ray Absorption Fine Structure, and Hall measurements. The ionization energies of the different complexes are measured both by photoluminescence and Hall measurements.

  16. Arsenic complexes optical signatures in As-doped HgCdTe

    Energy Technology Data Exchange (ETDEWEB)

    Gemain, F.; Robin, I. C.; Brochen, S.; Ballet, P.; Gravrand, O.; Feuillet, G. [CEA-LETI Minatec Campus, 17 rue des Martyrs, 38000 Grenoble (France)

    2013-04-08

    In this paper, the optical signatures of arsenic complexes in As-doped HgCdTe samples grown by molecular beam epitaxy are clearly identified using comparison between photoluminescence spectra, Extended X-Ray Absorption Fine Structure, and Hall measurements. The ionization energies of the different complexes are measured both by photoluminescence and Hall measurements.

  17. Development of CdZnTe X-ray detectors at DSRI

    DEFF Research Database (Denmark)

    van Pamelen, M.A.J.; Budtz-Jørgensen, Carl; Kuvvetli, Irfan

    2000-01-01

    An overview of the development of CdZnTe X-ray detectors at the Danish Space Research Institute is presented. Initiated in the beginning of 1996, the main motivation at that time was to develop focal plane detectors for the novel type of hard X-ray telescopes, which are currently under study at D...

  18. CdZnTe drift detector with correction for hole trapping

    DEFF Research Database (Denmark)

    van Pamelen, M.A.J.; Budtz-Jørgensen, Carl

    1998-01-01

    The results are presented of a CdZnTe drift detector for which the energy determination can be corrected for hole trapping. The electronic noise and the hole contribution to the signal are reduced and the signals are also corrected for any residual effects of hole trapping. This is achieved by us...

  19. Comparative study on toxicity of extracellularly biosynthesized and laboratory synthesized CdTe quantum dots

    Czech Academy of Sciences Publication Activity Database

    Komínková, M.; Milosavljevic, V.; Vítek, Petr; Polanská, H.; Číhalová, K.; Dostálová, S.; Hynstová, V.; Guran, R.; Kopel, P.; Richtera, L.; Masarik, M.; Brtnický, M.; Kynický, J.; Zítka, O.; Adam, V.

    2017-01-01

    Roč. 241, JAN (2017), s. 193-200 ISSN 0168-1656 R&D Projects: GA MŠk(CZ) LO1415 Institutional support: RVO:67179843 Keywords : Quantum dots * Biosynthesis * Escherichia coli (E. coli) * CdTe * Toxicity Subject RIV: EI - Biotechnology ; Bionics OBOR OECD: Environmental biotechnology Impact factor: 2.599, year: 2016

  20. Growth and characterization of CdTe single crystals for radiation detectors

    CERN Document Server

    Funaki, M; Satoh, K; Ohno, R

    1999-01-01

    To improve the productivity of CdTe radiation detectors, the crystal growth by traveling heater method (THM) as well as the quality of the fabricated detectors were investigated. In the THM growth, optimization of the solvent volume was found to be essential because it affects the shape of the growth interface. The use of the slightly tilted seed from B was also effective to limit the generation of twins having different directions. Single-crystal (1 1 1) wafers, larger than 30x30 mm sup 2 were successfully obtained from a grown crystal of 50 mm diameter. Pt/CdTe/Pt detectors of dimensions 4x4x2 mm sup 3 , fabricated from the whole crystal ingot, showed an energy resolution (FWHM of 122 keV peak from a sup 5 sup 7 Co source) between 6% and 8%. Similarly, Pt/CdTe/In detectors of dimensions 2x2x0.5 mm sup 3 showed a resolution better than 3%. These characteristics encourage the practical applications of various types of CdTe detectors.

  1. Surface plasmon polariton enhanced ultrathin nano-structured CdTe solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Luk, Ting S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Center for Integrated Nanotechnologies; Fofang, Nche T. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Center for Integrated Nanotechnologies; Cruz-Campa, Jose L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Frank, Ian [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Center for Integrated Nanotechnologies; Campione, Salvatore [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Center for Integrated Nanotechnologies

    2014-08-21

    Here, we demonstrate numerically that two-dimensional arrays of ultrathin CdTe nano-cylinders on Ag can serve as an effective broadband anti-reflection structure for solar cell applications. Such devices exhibit strong absorption properties, mainly in the CdTe semiconductor regions, and can produce short-circuit current densities of 23.4 mA/cm2, a remarkable number in the context of solar cells given the ultrathin dimensions of our nano-cylinders. The strong absorption is enabled via excitation of surface plasmon polaritons (SPPs) under plane wave incidence. In particular, we identified the key absorption mechanism as enhanced fields of the SPP standing waves residing at the interface of CdTe nano-cylinders and Ag. We compare the performance of Ag, Au, and Al substrates, and observe significant improvement when using Ag, highlighting the importance of using low-loss metals. Although we use CdTe here, the proposed approach is applicable to other solar cell materials with similar absorption properties.

  2. Temperature dependence of dc photoconductivity in CdTe thin films

    Indian Academy of Sciences (India)

    Keeping the above aspects in mind, an experimental study on pho- toconductivity processes in pure CdTe thin films ... form of a Faraday caze to keep undesirable noise at minimum. 3. Results and discussion ..... represented in table 1 which show a decreasing trend with increasing ambient temperature. Howeverγ < 1 at any ...

  3. Further comments on segregation during Bridgman growth of Cd(x)Hg(1-x)Te

    Science.gov (United States)

    Lehoczky, S. L.; Szofran, F. R.

    1984-01-01

    The authors comment on recent papers published by Capper et al. (1983) and Jones et al. (1983) which report and discuss the variation of composition with axial position in Bridgman-grown Cd(x)Hg(1-x)Te alloys. The validity of a diffusion-controlled model for non-mixing growth conditions is particularly noted.

  4. Preparation of High Purity CdTe for Nuclear Detector: Electrical and Nuclear Characterization

    Science.gov (United States)

    Zaiour, A.; Ayoub, M.; Hamié, A.; Fawaz, A.; Hage-ali, M.

    High purity crystal with controllable electrical properties, however, control of the electrical properties of CdTe has not yet been fully achieved. Using the refined Cd and Te as starting materials, extremely high-purity CdTe single crystals were prepared by the traditional vertical THM. The nature of the defects involved in the transitions was studied by analyzing the position of the energy levels by TSC method. The resolution of 4.2 keV (FWHM) confirms the high quality and stability of the detectors: TSC spectrum was in coherence with detectors spectrum with a horizontal plate between 0.2 and 0.6 eV. The enhancement in resolution of detectors with a full width at half- maximum (less than 0.31 meV), lead to confirm that the combination of vacuum distillation and zone refining was very effective to obtain more purified CdTe single crystals for photovoltaic or nuclear detectors with better physical properties.

  5. Neutron scattering studies of a dilute magnetic semiconductor: Cd1-xMnxTe

    DEFF Research Database (Denmark)

    Steigenberger, Ursula; Lebech, Bente; Galazka, Robert R.

    1986-01-01

    The development of the magnetic ordering in the magnetic semiconductor Cd1-xMnxTe was investigated by elastic neutron scattering. A detailed study of the correlation length and the intensity as a function of temperature, direction in reciprocal space and concentration of the magnetic ions has been...

  6. Thermographic analysis of the growth of Cd1-xZnxTe single crystals

    Science.gov (United States)

    Shcherbak, Larysa P.; Kopach, Oleh V.; Fochuk, Petro M.; Bolotnikov, Aleksey E.; James, Ralph B.

    2010-08-01

    Bulk Cd1-xZnxTe (0pre-history of the melts (superheating, thermo-cycling, and cooling rate) on various physical properties based on our thermographic analyses, electrical conductivity and viscosity measurements. Increasing the Zn content causes non-monotonic dependencies in the quality of the crystals' structure.

  7. Synthesis and characterization of CdTe/CdSe core/shell nanoparticles with high emission from 570 to 610 nm

    International Nuclear Information System (INIS)

    Valencia, O G Rojas; Tellez, M Corea; Espinola, J L Casas

    2015-01-01

    The paper presents the advance process of synthesis of CdTe/CdSe core/shell Quantum Dots (QDs) with emission wavelength from 570 to 610 nm. This synthesis was performed using modified Hot-Injection method. The CdTe/CdSe core-shell QDs have been characterized by the transmission electron microscopy (TEM) with the aim to control the QDs shape and the average size. The optical absorption and photoluminescence (PL) spectra are investigated in four samples obtained at different reaction times (5, 10, 15 and 20 s) of core growth after the CdSe passivation of the CdTe cores. Obtained results have shown that synthesized QDs have a good crystallinity, spherical shape and bright emission at 610 nm. The reaction time enlargement permits increasing the average size of CdTe/CdSe core-shell QDs, together with “red” shifting the PL wavelength and increasing the PL intensity. The advantages of synthesized CdTe/CdSe core/shell QDs are discussed. (paper)

  8. Analysis of the electrical conduction in CdHgTe crystals

    International Nuclear Information System (INIS)

    Dziuba, Z.

    1987-01-01

    The electrical conduction versus magnetic field in p-like CdHgTe samples at 77 K is investigated by analysing the conductivity tensor components. The electrical conduction is mainly due to electrons in the conduction band and low-mobility carriers in an impurity band. In the investigated samples Cd/sub x/Hg/sub 1-x/Te with the composition x approximately 0.17 the concentration of electrons in the conduction band is higher than the intrinsic one and in samples with the composition close to HgTe the concentration of electrons in the conduction band is equal to or lower than the intrinsic one. The model of a half-filled impurity band situated close to the bottom of the conduction band is proposed to account for the concentration of electrons in the conduction band. (author)

  9. Multidirectional channeling analysis of epitaxial CdTe layers using an automatic RBS/channeling system

    Energy Technology Data Exchange (ETDEWEB)

    Wielunski, L.S.; Kenny, M.J. [CSIRO, Lindfield, NSW (Australia). Applied Physics Div.

    1993-12-31

    Rutherford Backscattering Spectrometry (RBS) is an ion beam analysis technique used in many fields. The high depth and mass resolution of RBS make this technique very useful in semiconductor material analysis [1]. The use of ion channeling in combination with RBS creates a powerful technique which can provide information about crystal quality and structure in addition to mass and depth resolution [2]. The presence of crystal defects such as interstitial atoms, dislocations or dislocation loops can be detected and profiled [3,4]. Semiconductor materials such as CdTe, HgTe and Hg+xCd{sub 1-x}Te generate considerable interest due to applications as infrared detectors in many technological areas. The present paper demonstrates how automatic RBS and multidirectional channeling analysis can be used to evaluate crystal quality and near surface defects. 6 refs., 1 fig.

  10. Mercury cadmium telluride (HgCdTe) thin films fabricated by close spaced sublimation technique

    International Nuclear Information System (INIS)

    Hannan, M.A.; Basharat, M.; Ali, A.; Shah, N.A.; Maqsood, A.

    2007-01-01

    Thin films of HgCdTe were fabricated by deposition of HgTe on the CdTe thin film substrates. Both depositions were carried out through close spaced sublimation (CSS) technique. The structural investigation performed by means of X-ray diffraction (XRD) technique and energy dispersive X-ray spectroscopy (EDS) showed that the deposited films exhibit a polycrystalline structure with large number of sharp grain boundaries. The samples were then characterized optically to determine the refractive index. Absorption coefficient and the optical band gaps. The estimated band gap decreased, typically from 1.46 to 1.43 Ev as Hg content in the films increased from 1.41 to 3.29-wt. the deposited films showed high value of resistivity. Which decreased with increasing temperature showing the semiconducting behavior of the films. The prepared films gave response to infrared radiation. (author)

  11. Surface morphology study on CdZnTe crystals by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Azoulay, M.; George, M.A.; Burger, A.; Collins, W.E.; Silberman, E. [Fisk Univ., Nashville, TN (United States)

    1993-03-01

    The study of the crystal surface morphology of CdZnTe is important for the understanding of the fundamentals of crystal growth in order to improve the crystal quality which is essential in applications such as substrates for epitaxy or performance of devices, i.e., room temperature nuclear spectrometers. We present a first atomic force microscopy study on CdZnTe. Cleaved (110) surfaces were imaged in the ambient and an atomic layer step structure was revealed. The effects of thermal annealing on the atomic steps together with Te precipitation along these steps are discussed in terms of deformation due to stress relief and the diffusion of tellurium precipitates. 12 refs., 3 figs.

  12. Fermiology of the strongly spin-orbit coupled superconductor Sn(1-x)In(x)Te: implications for topological superconductivity.

    Science.gov (United States)

    Sato, T; Tanaka, Y; Nakayama, K; Souma, S; Takahashi, T; Sasaki, S; Ren, Z; Taskin, A A; Segawa, Kouji; Ando, Yoichi

    2013-05-17

    We have performed angle-resolved photoemission spectroscopy on the strongly spin-orbit coupled low-carrier density superconductor Sn(1-x)In(x)Te (x = 0.045) to elucidate the electronic states relevant to the possible occurrence of topological superconductivity, as recently reported for this compound based on point-contact spectroscopy. The obtained energy-band structure reveals a small holelike Fermi surface centered at the L point of the bulk Brillouin zone, together with a signature of a topological surface state, indicating that this material is a doped topological crystalline insulator characterized by band inversion and mirror symmetry. A comparison of the electronic states with a band-noninverted superconductor possessing a similar Fermi surface structure, Pb(1-x)Tl(x)Te, suggests that the anomalous behavior in the superconducting state of Sn(1-x)In(x)Te is related to the peculiar orbital characteristics of the bulk valence band and/or the presence of a topological surface state.

  13. Effect of CdCl{sub 2} treatment on structural and electronic property of CdTe thin films deposited by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Islam, M.A. [Solar Energy Research Institute (SERI), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Hossain, M.S.; Aliyu, M.M. [Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Karim, M.R. [Center of Excellence for Research in Engineering Materials (CEREM) College of Engineering, King Saud University, Riyadh, 11421 (Saudi Arabia); Razykov, T.; Sopian, K. [Solar Energy Research Institute (SERI), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Amin, N., E-mail: nowshad@eng.ukm.my [Solar Energy Research Institute (SERI), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Center of Excellence for Research in Engineering Materials (CEREM) College of Engineering, King Saud University, Riyadh, 11421 (Saudi Arabia)

    2013-11-01

    The structural and electrical properties of the magnetron sputtered CdTe thin films with subsequent CdCl{sub 2} solution treatment have been studied with a major focus on the influence of CdCl{sub 2} treatment to achieve high quality thin films. In this study, CdTe films with a thickness of 1.5 to 2 μm have been grown using the magnetron sputtering technique on top of glass substrate at an optimized substrate temperature of 250 °C. Aqueous CdCl{sub 2} concentration varied from 0.3 mol to 1.2 mol with the annealing temperature from 360 °C to 450 °C. The surface roughness of the films increases with the increase of solution concentration, while it fluctuates with the increase of annealing temperature. The density of nucleation centers and the strain increases for the films treated at 360 °C with 0.3 M to1.2 M while the grain growth of the films reduces. However, these strains are released at higher annealing temperatures, resulting in reduced dislocation densities, structural defects as well as increased crystalline property and grain size. The carrier concentration increases with the increase of treated CdCl{sub 2} concentration and subsequent annealing temperature. The highest carrier concentration of 1.05 × 10{sup 14}/cm{sup 3} was found for the CdTe thin films treated with 0.3 M CdCl{sub 2} solution followed by an annealing treatment at 420 °C for 20 min. - Highlights: • CdTe thin films are grown as absorption layers in CdTe solar cells by sputtering. • CdTe film quality in terms of structural and electronic properties is examined. • All growth parameters are optimized in the range of 1.5 to 2 μm CdTe films.

  14. Gamma radiation detectors on the base CdTe for environmental monitoring

    International Nuclear Information System (INIS)

    Bayramov, A.A.; Safarov, N.A.

    2006-01-01

    Full text: The purpose of the given work is development of small - sized dosimeters of gamma - radiation on basis CdTe for definition of a radiations level in an environment and for the control over the illegal moving of radioactive substances. It is supposed, that these dosimeters will replace devices in which as Geiger counters are used. Cadmium telluride (CdTe) is the first material to have been developed as a room-temperature semiconductor detector. Its E g ap of 1,45 eV gives a high enough resistively for room temperature operation, and Z of 48 and 52 gives a higher gamma radiation detection efficiency that either Si (E g ap=1,12 and Z=14) or Ge (E g ap=0,66 and Z=32). Gamma rays and charged particles interact with a solid by converting most of their energy into electron-hole pairs. In scintillators like NaI (Tl) the intensity of the fluorescence arising from these charge carriers is observed with a photomultiplier tube and is proportional to the radiation energy. Semiconductor detectors instead use an electric field to collect the charge carriers and the resulting current pulse is amplified and is proportional to the radiation energy. Polarization effects, which are temporary decrease in either the depleted thickness or the charge collection properties. The primary limitation on increasing E for CdTe detectors is the requirement to avoid excessive noise due to a high leakage current. Low resistively n-type CdTe has resistively between 10 :104 cm, which limits both E and depleted thickness. High resistively CdTe has between 10 6 : 10 1 0 cm. CdTe detectors with between 10 6 : 10 7 cm have been operated at 0 degrees Celcium which reduces the leakage current and allows E to be increased. However, a major disadvantage is the lack of room-temperature operation. High-Z room-temperature detectors have a number of different applications as spectrometers, radiation counters. CdTe provides improved energy-resolution compared to NaI without the need for bulky cooling

  15. Study of the Mg incorporation in CdTe for developing wide band gap Cd1−xMgxTe thin films for possible use as top-cell absorber in a tandem solar cell

    International Nuclear Information System (INIS)

    Martínez, Omar S.; Millán, Aduljay Remolina; Huerta, L.; Santana, G.; Mathews, N.R.; Ramon-Garcia, M.L.; Morales, Erik R.; Mathew, X.

    2012-01-01

    Highlights: ► Thin films of Cd 1−x Mg x Te with high spatial uniformity and band gap in the range of 1.6–1.96 eV were deposited by vacuum co-evaporation of CdTe and Mg. ► Obtained Cd 1−x Mg x Te films have the structural characteristics of the CdTe, evidence of the change in atomic scattering due to incorporation of Mg was observed. ► XRD and XPS data confirmed the incorporation of Mg in the lattice of CdTe. ► SEM images revealed the impact of Mg incorporation on the morphology of the films, the changes in grain size and grain morphology are noticeable. - Abstract: Thin films of Cd 1−x Mg x Te with band gap in the range of 1.6–1.96 eV were deposited by vacuum co-evaporation of CdTe and Mg on glass substrates heated at 300 °C. Different experimental techniques such as XRD, UV–vis spectroscopy, SEM, and XPS were used to study the effect of Mg incorporation into the lattice of CdTe. The band gap of the films showed a clear tendency to increase as the Mg content in the film is increased. The Cd 1−x Mg x Te films maintain all the structural characteristics of the CdTe, however, diminishing of intensity for the XRD patterns is observed due to both change in preferential orientation and change in atomic scattering due to the incorporation of Mg. SEM images showed significant evidences of morphological changes due to the presence of Mg. XRD, UV–vis spectroscopy, and XPS data confirmed the incorporation of Mg in the lattice of CdTe. The significant increase in band gap of CdTe due to incorporation of Mg suggests that the Cd 1−x Mg x Te thin film is a candidate material to use as absorber layer in the top-cell of a tandem solar cell.

  16. Development of near-infrared ratiometric fluorescent probe based on cationic conjugated polymer and CdTe/CdS QDs for label-free determination of glucose in human body fluids.

    Science.gov (United States)

    Yu, Mengze; Zhao, Kunli; Zhu, Xiaohua; Tang, Shiyun; Nie, Zhou; Huang, Yan; Zhao, Peng; Yao, Shouzhuo

    2017-09-15

    Quantum dots (QDs) have attracted extensive attention in biomedical applications, because of their broad excitation spectra, narrow and symmetric emission peaks etc. Furthermore, near-infrared (NIR) QDs have further advantages including low autofluorescence, good tissue penetration and low phototoxicity. In this work, the electrostatic interaction and fluorescence resonance energy transfer (FRET) between NIR CdTe/CdS QDs and cationic conjugated polymer (CCP) was studied for the first time. Based on the newly discovered phenomena and the result that hydrogen peroxide (H 2 O 2 ) can efficiently quench the fluorescence of NIR CdTe/CdS QDs, a novel NIR ratiometric fluorescent probe for determination of H 2 O 2 and glucose was developed. Under the optimized conditions, the detection limit of H 2 O 2 and glucose assay were 0.1mM and 0.05mM (S/N=3), with a linear range of 0.2-4mM and 0.1-5mM, respectively. Because of the NIR spectrum, this ratiometric probe can be also applied for the determination of glucose in whole blood samples directly, providing a valuable platform for glucose sensing in clinic diagnostic and drug screening. Copyright © 2017. Published by Elsevier B.V.

  17. Operation of CdZnTe Semiconductor Detectors in Liquid Scintillator for the COBRA Experiment

    International Nuclear Information System (INIS)

    Oldorf, Christian

    2015-08-01

    COBRA, the Cadmium-Zinc-Telluride O-neutrino double-Beta Research Apparatus, is an experiment aiming for the measurement of the neutrinoless double beta decay with several isotopes, in particular 116 Cd, 106 Cd and 130 Te. A highly granular large scale experiment with about 400 kg of CdZnTe semiconductor detectors is currently under development. To provide evidence for the neutrinoless double beta decay of 116 Cd, a background rate in the order of 10 -3 counts/keV/kg/a is needed to achieve the required half-life sensitivity of at least 2 . 10 26 years. To reach this target, the detectors have to be operated in a highly pure environment, shielded from external radiation. Liquid scintillator is a promising candidate as a circum fluent replacement for the currently used lacquer. Next to the function as highly pure passivation material, liquid scintillator also acts as a neutron shield and active veto for external gammas. Within this thesis, the design, construction and assembly of a test set-up is described. The operation of four CdZnTe detectors after several years of storage in liquid scintillator is demonstrated. Next to extensive material compatibility tests prior to the assembly, the commissioning of the set-up and the characterization of the detectors are shown. Finally, results concerning the background reduction capability of liquid scintillator and the detection of cosmic muons are presented and compared to a Monte Carlo simulation.

  18. Study and development of new CdTe and CdZnTe detection structures for X and {gamma} imagery; Etude et realisation de nouvelles structures de detection a base de CdTe et CdZnTe pour l`imagerie X et {gamma}

    Energy Technology Data Exchange (ETDEWEB)

    Rosaz, M

    1997-10-24

    The aim of this study is to show the interest of applying cadmium telluride (CdTe) for X- and {gamma}- ray imaging applications, with specific technological (via contact nature) and geometric (via Frisch grids) structures suited for each application. This work is divided into three different but complementary parts: the first part describes a simulation model which allows a better understanding of CdTe based {gamma}- ray detectors. The new feature of this model compared to previous ones, is that it is able to take into account the electric field`s non uniform spatial distribution inside the detector s. The results enable us to de-convolute the influence of material and contact parameters on the spectrometric performances (energy resolution and peak/valley ratio) of CdTe based detectors; the second part presents different technological structures deposited upon CdTe, (grown by two different methods, i.e Bridgman and High Pressure Bridgman). These structures were characterised in X- and {gamma}- ray detection; theoretical models are developed which allow a certain insight into the detection properties of each couple (material + contact); the third part deals with new contact geometries which allow a screening effect of the bulk (analogous to the Frisch grid effect in gaseous detectors) resulting in improved energy resolution and peak/valley ratios; encouraging first results on prototypes are presented and discussed. This work has allowed a better understanding of physical behaviour of CdTe based detectors, coupled with advances in technological issues to upgrade the overall performances of these detectors for application in X- and {gamma}- ray imaging. (author) 93 refs.

  19. Synthesis and optical characterization of nanocrystalline CdTe thin films

    Science.gov (United States)

    Al-Ghamdi, A. A.; Khan, Shamshad A.; Nagat, A.; Abd El-Sadek, M. S.

    2010-11-01

    From several years the study of binary compounds has been intensified in order to find new materials for solar photocells. The development of thin film solar cells is an active area of research at this time. Much attention has been paid to the development of low cost, high efficiency thin film solar cells. CdTe is one of the suitable candidates for the production of thin film solar cells due to its ideal band gap, high absorption coefficient. The present work deals with thickness dependent study of CdTe thin films. Nanocrystalline CdTe bulk powder was synthesized by wet chemical route at pH≈11.2 using cadmium chloride and potassium telluride as starting materials. The product sample was characterized by transmission electron microscope, X-ray diffraction and scanning electron microscope. The structural characteristics studied by X-ray diffraction showed that the films are polycrystalline in nature. CdTe thin films with thickness 40, 60, 80 and 100 nm were prepared on glass substrates by using thermal evaporation onto glass substrate under a vacuum of 10 -6 Torr. The optical constants (absorption coefficient, optical band gap, refractive index, extinction coefficient, real and imaginary part of dielectric constant) of CdTe thin films was studied as a function of photon energy in the wavelength region 400-2000 nm. Analysis of the optical absorption data shows that the rule of direct transitions predominates. It has been found that the absorption coefficient, refractive index ( n) and extinction coefficient ( k) decreases while the values of optical band gap increase with an increase in thickness from 40 to 100 nm, which can be explained qualitatively by a thickness dependence of the grain size through decrease in grain boundary barrier height with grain size.

  20. Synthesis and characterization of (Cd,Zn)S buffer layer for Cu2ZnSnSe4 solar cells

    Science.gov (United States)

    Ben Messaoud, Khaled; Buffière, Marie; Brammertz, Guy; Lenaers, Nick; Boyen, Hans-Gerd; Sahayaraj, Sylvester; Meuris, Marc; Amlouk, Mosbah; Poortmans, Jef

    2017-07-01

    In order to improve the electrical performances of Cu2ZnSnSe4 (CZTSe) based solar cells, the standard CdS buffer layer was replaced by (Cd,Zn)S processed by chemical bath deposition. The morphology and composition of the (Cd,Zn)S thin films were studied as a function of [Zn]/([Zn]  +  [Cd]) ratio in the chemical bath (80, 85 and 90%). The CZTSe/(Cd,Zn)S solar cells with and without Cd partial electrolyte (Cd PE) treatment were compared to CZTSe/CdS reference devices using current-voltage and external quantum efficiency measurements. The (Cd,Zn)S thin films show a non-homogeneity of Zn distribution and phase formation, with a shift from Zn(O,OH) x to ZnS phase when increasing the deposition time and a decrease of the layers thicknesses when increasing the Zn concentration in chemical bath. A model for the growth of (Cd,Zn)S thin films is proposed. The resulting CZTSe/(Cd,Zn)S devices show an important reduction of the barrier at the hetero-interface, which is attributed to the lower density of O contamination in (Cd,Zn)S compared to CdS, inducing a lower density of deep p-type recombination centers. Despite the reduced compensation of the buffer layer, CZTSe/(Cd,Zn)S devices show a deterioration of the open circuit voltage and the fill factor with the increase of Zn content in (Cd,Zn)S. These electrical losses were avoided by Cd PE treatment prior to the deposition of (Cd,Zn)S.

  1. Photoluminescence Imaging of Large-Grain CdTe for Grain Boundary Characterization

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, Steve; Allende Motz, Alyssa; Reese, Matthew O.; Burst, James M.; Metzger, Wyatt K.

    2015-06-14

    In this work, we use photoluminescence (PL) imaging to characterize CdTe grain boundary recombination. We use a silicon megapixel camera and green (532 nm) laser diodes for excitation. A microscope objective lens system is used for high spatial resolution and a field of view down to 190 um x 190 um. PL images of large-grain (5 to 50 um) CdTe samples show grain boundary and grain interior features that vary with processing conditions. PL images of samples in the as-deposited state show distinct dark grain boundaries that suggest high excess carrier recombination. A CdCl2 treatment leads to PL images with very little distinction at the grain boundaries, which illustrates the grain boundary passivation properties. Other process conditions are also shown, along with comparisons of PL images to high spatial resolution time-resolved PL carrier lifetime maps.

  2. Effects on structural, electronic transport and optical properties of doped and undoped ZnTe thin Films for CdTe/Cd solar cells

    International Nuclear Information System (INIS)

    Tariq, G.H.; Anis-ur-Rehman, M.

    2011-01-01

    To overcome the naturally existing Schottky barrier problem between p-CdTe and any metal, an intermediate semiconductor thin buffer layer is a better choice prior to the final metallization for contact. Among many investigated back contact materials the ZnTe is suitable as a buffer layer. ZnTe thin films were deposited onto glass substrates by the thermal evaporation technique under vacuum approx. equal to 2 X 10/sup -5/mbar. Undoped ZnTe thin films are highly resistive, extrinsic doping of Cu was made to improve the electrical conductivity. Films were doped by immersing in Cu NO/sub 3/)sub 2)/.5H/sub 2/O solutions for Cu doping. To optimize the growth parameters the prepared films were characterized using various techniques. The structural analysis of these films was performed by X-ray diffraction (XRD) technique and optical transmission. X-ray diffraction identified the phases present in these films and also observed that the prepared films were polycrystalline. Also the spectral dependence of absorption coefficient was determined from spectrophotometer. Energy band gap index were calculated from obtained optical measurements data. (author)

  3. Vapor CdCl{sub 2}{emdash}optimization and screening experiments for an all dry chloride treatment of CdS/CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Albin, D.S. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Mahathongdy, Y.; Wolden, C.A.; Baldwin, R.M. [Colorado School of Mines, Golden, Colorado 80401 (United States)

    1999-03-01

    A dry vapor treatment of CdCl{sub 2} is being developed as an alternative approach to the conventional solution CdCl{sub 2} treatment of CdS/CdTe devices. In this alternative process, the CdS/CdTe substrates are vapor treated in a close-spaced sublimation configuration. A 16-run Plackett-Burman screening experiment identified source temperature, substrate temperature, and treatment time as being the most significant parameters in the process. Subsequently, a 20-run Central Composite Design showed that a source temperature of 380{endash}390&hthinsp;{degree}C, a temperature gradient ({Delta}T) of 5&hthinsp;{degree}C, and a time of 10 minutes provides the most process tolerant combination, yielding a total-area efficiency of 12.6{percent}. A strong interaction between {Delta}T and treatment time was also identified. The model indicated that for a small {Delta}T, device performance improved with decreasing time, whereas at larger values of {Delta}T, performance increased with increasing time. {copyright} {ital 1999 American Institute of Physics.}

  4. Vapor CdCl2—optimization and screening experiments for an all dry chloride treatment of CdS/CdTe solar cells

    Science.gov (United States)

    Mahathongdy, Yoxa; Albin, David S.; Wolden, Colin A.; Baldwin, Robert M.

    1999-03-01

    A dry vapor treatment of CdCl2 is being developed as an alternative approach to the conventional solution CdCl2 treatment of CdS/CdTe devices. In this alternative process, the CdS/CdTe substrates are vapor treated in a close-spaced sublimation configuration. A 16-run Plackett-Burman screening experiment identified source temperature, substrate temperature, and treatment time as being the most significant parameters in the process. Subsequently, a 20-run Central Composite Design showed that a source temperature of 380-390 °C, a temperature gradient (ΔT) of 5 °C, and a time of 10 minutes provides the most process tolerant combination, yielding a total-area efficiency of 12.6%. A strong interaction between ΔT and treatment time was also identified. The model indicated that for a small ΔT, device performance improved with decreasing time, whereas at larger values of ΔT, performance increased with increasing time.

  5. Leaching of cadmium and tellurium from cadmium telluride (CdTe) thin-film solar panels under simulated landfill conditions.

    Science.gov (United States)

    Ramos-Ruiz, Adriana; Wilkening, Jean V; Field, James A; Sierra-Alvarez, Reyes

    2017-08-15

    A crushed non-encapsulated CdTe thin-film solar cell was subjected to two standardized batch leaching tests (i.e., Toxicity Characteristic Leaching Procedure (TCLP) and California Waste Extraction Test (WET)) and to a continuous-flow column test to assess cadmium (Cd) and tellurium (Te) dissolution under conditions simulating the acidic- and the methanogenic phases of municipal solid waste landfills. Low levels of Cd and Te were solubilized in both batch leaching tests (<8.2% and <3.6% of added Cd and Te, respectively). On the other hand, over the course of 30days, 73% of the Cd and 21% of the Te were released to the synthetic leachate of a continuous-flow column simulating the acidic landfill phase. The dissolved Cd concentration was 3.24-fold higher than the TCLP limit (1mgL -1 ), and 650-fold higher than the maximum contaminant level established by the US-EPA for this metal in drinking water (0.005mgL -1 ). In contrast, the release of Cd and Te to the effluent of the continuous-flow column simulating the methanogenic phase of a landfill was negligible. The remarkable difference in the leaching behavior of CdTe in the columns is related to different aqueous pH and redox conditions promoted by the microbial communities in the columns, and is in agreement with thermodynamic predictions. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. EGS4 calculations for a Cd-Zn-Te detector to measure synchrotron radiation at PEP-II

    International Nuclear Information System (INIS)

    Nelson, W.R.; Kadyk, J.

    1997-01-01

    Calculations have been performed with the EGS4 Code System for a CdZnTe semiconductor detector to be used in background studies of synchrotron radiation at PEP-II. The simulations take into account K-shell fluorescent-photon production in a CdZnTe mixture, electron-hole pair collection and electronic-noise broadening. The results are compared with measurements made with encapsulated 241 Am, 133 Ba and 109 Cd sources

  7. Laser induced magneto-Raman optical gain of an exciton and a biexciton in a CdTe/ZnTe quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Sujanah, P. [Dept. of Physics, The American College, Madurai 625 002 (India); John Peter, A., E-mail: a.john.peter@gmail.com [Dept. of Physics, Govt. Arts College, Melur 625 106, Madurai (India); Lee, Chang Woo, E-mail: cwlee@khu.ac.kr [Department of Chemical Engineering, College of Engineering, Kyung Hee University, 1732 Deogyeong-daero, Gihung, Yongin, Gyeonggi 446-701 (Korea, Republic of)

    2016-06-15

    Magnetic field and laser field amplitude dependent electronic and optical properties of exciton and biexciton in a CdTe/ZnTe quantum dot nanostructure are brought out taking into account the spatial confinement effect. Binding energies of exciton and biexciton as functions of laser field amplitude and magnetic field strength are computed in a CdTe/ZnTe quantum dot for the constant dot radius 30 Å. Oscillator strength, resonant absorption coefficients and resonant optical Raman intensity of the exciton and biexciton as a function of laser field amplitude are obtained in the presence of magnetic field strength in a CdTe/ZnTe quantum dot. The laser field induced magneto-Raman gain is studied for a constant dot radii. The Coulomb interaction energy which is involved in Hartree potential is obtained numerically. The result shows that the applications of magnetic field strength and the laser field amplitude alter the electronic and optical properties considerably in the CdTe/ZnTe quantum dot.

  8. The effect of dephasing on edge state transport through p-n junctions in HgTe/CdTe quantum wells.

    Science.gov (United States)

    Zhang, Ying-Tao; Song, Juntao; Sun, Qing-Feng

    2014-02-26

    Using the Landauer-Büttiker formula, we study the effect of dephasing on the transport properties of the HgTe/CdTe p-n junction. It is found that in the HgTe/CdTe p-n junction the topologically protected gapless helical edge states manifest a quantized 2e²/h plateau robust against dephasing, in sharp contrast to the case for the normal HgTe/CdTe quantum well. This robustness of the transport properties of the edge states against dephasing should be attributed to the special construction of the HgTe/CdTe p-n junction, which limits the gapless helical edge states to a very narrow region and thus weakens the influence of the dephasing on the gapless edge states to a large extent. Our results demonstrate that the p-n junction could be a substitute device for use in experimentally observing the robust edge states and quantized plateau. Finally, we present a feasible scheme based on current experimental methods.

  9. Synthesis of CdTe/CdS/ZnS quantum dots and their application in imaging of hepatocellular carcinoma cells and immunoassay for alpha fetoprotein

    Energy Technology Data Exchange (ETDEWEB)

    Tian Jianniao; Liu Rongjun; Zhao Yanchun; Peng Yan; Hong Xue; Zhao Shulin [Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources (Ministry of Education of China), College of Chemistry and Chemical Engineering of Guangxi Normal University, Guilin 541004 (China); Xu Qing, E-mail: tianjn58@yahoo.com.cn [Pharmacology Department of Guilin Medical College, Guilin 541004 (China)

    2010-07-30

    We report the imaging of hepatocellular carcinoma cells and the immunoassay for alpha fetoprotein (AFP) using CdTe/CdS/ZnS core-shell-shell QDs. Stable and high PLQY (20%-48%) CdTe/CdS/ZnS core-shell-shell QDs were synthesized by a stepwise process. Bioconjugation of the core-shell-shell QDs with streptavidin (SA) was successfully applied in immunofluorescent imaging of the human hepatocellular carcinoma (HCC) cell line HepG2.2.15. Furthermore, the thioglycolic acid (TGA)-capped CdTe/CdS/ZnS core-shell-shell QDs fluorescence lifetime is longer than fluorescein, so it was first engaged to conjugate with antigen for the determination of protein (AFP) by fluorescence polarization immunoassay.

  10. Structural stability of ternary C22–Zr6X2Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and C22–Zr6Sn2T′ (T′=Fe, Co, Ni, Cu) compounds

    International Nuclear Information System (INIS)

    Colinet, Catherine; Crivello, Jean-Claude; Tedenac, Jean-Claude

    2013-01-01

    The crystal and electronic structures, and the thermodynamic properties of Zr 6 X 2 Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and Zr 6 Sn 2 T′ (T′=Fe, Co, Ni, Cu) ternary compounds in the Fe 2 P-type structure have been investigated by means of first principle calculations. The calculated structural parameters are in good agreement with the experimental data. The total electronic densities of states as well as the Bader charges of the atoms have been computed. Both electronic and size effects allow to explain the stability of the ternary Zr 6 X 2 Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and Zr 6 Sn 2 T′ (T′=Fe, Co, Ni, Cu) compounds. - Graphical abstract: Valence charge electronic localization function (ELF) calculated for Zr 6 Sb 2 Co compound. Display Omitted - Highlights: • Structural stability of Zr 6 X 2 T′ compounds (X: p element, T′: late transition metal) in the Fe 2 P-type structure. • First principles calculation of lattice parameters and enthalpies of formation. • Electronic densities of state in the series Zr 6 Sn 2 T′ (T′=Fe, Co, Ni, Cu). • Electronic densities of state in the series Zr 6 X 2 Co (X=Al, Ga, Sn, As, Sb, Bi, Te)

  11. Lattice defects in semiconducting Hg/1-x/Cd/x/Te alloys. III - Defect structure of undoped Hg0.6Cd0.4Te

    Science.gov (United States)

    Vydyanath, H. R.; Donovan, J. D.; Nelson, D. A.

    1981-01-01

    Hall effect measurements were carried out on undoped Hg0.6Cd0.4Te crystals quenched to room temperature subsequent to equilibration at temperatures varying from 450 to 720 C under various partial pressures of Hg. The variation of the hole concentration as a function of the partial pressure of Hg indicates that the native acceptor defects are doubly ionized. Native donor defects are found to be negligible in concentration and the p-type to n-type conversion is shown to be due to residual donors and not due to native donor defects. Thermodynamic constant for the incorporation of the doubly ionized native acceptor defect has been established.

  12. Electrical characterization of the temperature dependence in CdTe/CdS heterojunctions deposited in-situ by pulsed laser deposition

    Science.gov (United States)

    Avila-Avendano, Jesus; Quevedo-Lopez, Manuel; Young, Chadwin

    2018-02-01

    The I-V and C-V characteristics of CdTe/CdS heterojunctions deposited in-situ by Pulsed Laser Deposition (PLD) were evaluated. In-situ deposition enables the study of the CdTe/CdS interface by avoiding potential impurities at the surface and interface as a consequence of exposure to air. The I-V and C-V characteristics of the resulting junctions were obtained at different temperatures, ranging from room temperature to 150 °C, where the saturation current (from 10-8 to 10-4 A/cm2), ideality factor (between 1 and 2), series resistance (from 102 to 105 Ω), built-in potential (0.66-0.7 V), rectification factor (˜106), and carrier concentration (˜1016 cm-3) were obtained. The current-voltage temperature dependence study indicates that thermionic emission is the main transport mechanism at the CdTe/CdS interface. This study also demonstrated that the built-in potential (Vbi) calculated using a thermionic emission model is more accurate than that calculated using C-V extrapolation since C-V plots showed a Vbi shift as a function of frequency. Although CdTe/CdS is widely used for photovoltaic applications, the parameters evaluated in this work indicate that CdTe/CdS heterojunctions could be used as rectifying diodes and junction field effect transistors (JFETs). JFETs require a low PN diode saturation current, as demonstrated for the CdTe/CdS junction studied here.

  13. Charge-carrier transport and recombination in heteroepitaxial CdTe

    International Nuclear Information System (INIS)

    Kuciauskas, Darius; Farrell, Stuart; Dippo, Pat; Moseley, John; Moutinho, Helio; Li, Jian V.; Allende Motz, A. M.; Kanevce, Ana; Zaunbrecher, Katherine; Gessert, Timothy A.; Levi, Dean H.; Metzger, Wyatt K.; Colegrove, Eric; Sivananthan, S.

    2014-01-01

    We analyze charge-carrier dynamics using time-resolved spectroscopy and varying epitaxial CdTe thickness in undoped heteroepitaxial CdTe/ZnTe/Si. By employing one-photon and nonlinear two-photon excitation, we assess surface, interface, and bulk recombination. Two-photon excitation with a focused laser beam enables characterization of recombination velocity at the buried epilayer/substrate interface, 17.5 μm from the sample surface. Measurements with a focused two-photon excitation beam also indicate a fast diffusion component, from which we estimate an electron mobility of 650 cm 2 (Vs) −1 and diffusion coefficient D of 17 cm 2  s −1 . We find limiting recombination at the epitaxial film surface (surface recombination velocity S surface  = (2.8 ± 0.3) × 10 5  cm s −1 ) and at the heteroepitaxial interface (interface recombination velocity S interface  = (4.8 ± 0.5) × 10 5  cm s −1 ). The results demonstrate that reducing surface and interface recombination velocity is critical for photovoltaic solar cells and electronic devices that employ epitaxial CdTe.

  14. Structural and optical properties of Cu-doped CdTe films with hexagonal phase grown by pulsed laser deposition

    Directory of Open Access Journals (Sweden)

    F. de Moure-Flores

    2012-06-01

    Full Text Available Cu-doped CdTe thin films were prepared by pulsed laser deposition on Corning glass substrates using powders as target. Films were deposited at substrate temperatures ranging from 100 to 300 °C. The X-ray diffraction shows that both the Cu-doping and the increase in the substrate temperature promote the presence of the hexagonal CdTe phase. For a substrate temperature of 300 °C a CdTe:Cu film with hexagonal phase was obtained. Raman and EDS analysis indicate that the films grew with an excess of Te, which indicates that CdTe:Cu films have p-type conductivity.

  15. Surface treatment effects on the I-V characteristics of HgCdTe LW infrared photovoltaic detectors

    Science.gov (United States)

    Xie, Xiaohui; Liao, Qingjun; Zhu, Jianmei; He, Gaoyin; Wang, Jianxin; He, Min; Hu, Xiaoning

    2012-10-01

    The weakness of HgCdTe materials is a weak Hg-Te bond, which results in bulk, surface and interface instabilities. Usual surface preparation methods for bulk HgCdTe wafers are chemical etch with bromine-in-methanol (Br-MeOH). Because the bromine etch forms Te-enrich HgCdTe surface due to the depletion of Hg and Cd. This Te-enrich surface layer is easily oxidized when exposed to air or acids, and this native oxide is one of the main reasons degrading the passivation properties. Besides the surface of the material will have more damages during the ion implantation, which is used to process a junction. In this way, appropriate surface passivation is required and is very important for HgCdTe photovoltaic detectors. This paper presents the different surface treatment methods on the I-V characteristics of HgCdTe infrared photovoltaic detectors. The results of the experiments show that the performance of the diodes with surface treatment by the bromine-in-ethanol etching and lactic acid in glycol solution oxidation is better than other diodes, which have no surface treatment or only bromine-in-ethanol etching. So it proves that the process of surface treatment in appropriate methods can improve the quality of surface passivation.

  16. Experimental and theoretical comparison of Sb, As, and P diffusion mechanisms and doping in CdTe

    Science.gov (United States)

    Colegrove, E.; Yang, J.-H.; Harvey, S. P.; Young, M. R.; Burst, J. M.; Duenow, J. N.; Albin, D. S.; Wei, S.-H.; Metzger, W. K.

    2018-02-01

    Fundamental material doping challenges have limited CdTe electro-optical applications. In this work, the As atomistic diffusion mechanisms in CdTe are examined by spatially resolving dopant incorporation in both single-crystalline and polycrystalline CdTe over a range of experimental conditions. Density-functional theory calculations predict experimental activation energies and indicate that As diffuses slowly through the Te sublattice and quickly along GBs similar to Sb. Because of its atomic size and associated defect chemistry, As does not have a fast interstitial diffusion component similar to P. Experiments to incorporate and activate P, As, and Sb in polycrystalline CdTe are conducted to examine if ex situ Group V doping can overcome historic polycrystalline doping limits. The distinct P, As, and Sb diffusion characteristics create different strategies for increasing hole density. Because fast interstitial diffusion is prominent for P, less aggressive diffusion conditions followed by Cd overpressure to relocate the Group V element to the Te lattice site is effective. For larger atoms, slower diffusion through the Te sublattice requires more aggressive diffusion, however further activation is not always necessary. Based on the new physical understanding, we have obtained greater than 1016 cm‑3 hole density in polycrystalline CdTe films by As and P diffusion.

  17. Experimental and theoretical comparison of Sb, As, and P diffusion mechanisms and doping in CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Colegrove, Eric; Yang, Ji-Hui; Harvey, Steven P.; Young, Matthew; Burst, James M.; Duenow, Joel N.; Albin, David S.; Wei, Su-Huai; Metzger, Wyatt

    2018-01-10

    Fundamental material doping challenges have limited CdTe electro-optical applications. In this work, the As atomistic diffusion mechanisms in CdTe are examined by spatially resolving dopant incorporation in both single-crystalline and polycrystalline CdTe over a range of experimental conditions. Density-functional theory calculations predict experimental activation energies and indicate As diffuses slowly through the Te sublattice and quickly along GBs similar to Sb. Because of its atomic size and associated defect chemistry, As does not have a fast interstitial diffusion component similar to P. Experiments to incorporate and activate P, As, and Sb in polycrystalline CdTe are conducted to examine if ex-situ Group V doping can overcome historic polycrystalline doping limits. The distinct P, As, and Sb diffusion characteristics create different strategies for increasing hole density. Because fast interstitial diffusion is prominent for P, less aggressive diffusion conditions followed by Cd overpressure to relocate the Group V element to the Te lattice site is effective. For larger atoms, slower diffusion through the Te sublattice requires more aggressive diffusion, however further activation is not always necessary. Based on the new physical understanding, we have obtained greater than 10^16 cm^-3 hole density in polycrystalline CdTe films by As and P diffusion.

  18. Aligned ZnO/CdTe core-shell nanocable arrays on indium tin oxide: synthesis and photoelectrochemical properties.

    Science.gov (United States)

    Wang, Xina; Zhu, Haojun; Xu, Yeming; Wang, Hao; Tao, Yin; Hark, Suikong; Xiao, Xudong; Li, Quan

    2010-06-22

    Vertically aligned ZnO/CdTe core-shell nanocable arrays-on-indium tin oxide (ITO) are fabricated by electrochemical deposition of CdTe on ZnO nanorod arrays in an electrolyte close to neutral pH. By adjusting the total charge quantity applied during deposition, the CdTe shell thickness can be tuned from several tens to hundreds of nanometers. The CdTe shell, which has a zinc-blende structure, is very dense and uniform both radially and along the axial direction of the nanocables, and forms an intact interface with the wurtzite ZnO nanorod core. The absorption of the CdTe shell above its band gap ( approximately 1.5 eV) and the type II band alignment between the CdTe shell and the ZnO core, respectively, demonstrated by absorption and photoluminescence measurements, make a nanocable array-on-ITO architecture a promising photoelectrode with excellent photovoltaic properties for solar energy applications. A photocurrent density of approximately 5.9 mA/cm(2) has been obtained under visible light illumination of 100 mW cm(-2) with zero bias potential (vs saturated calomel electrode). The neutral electrodeposition method can be generally used for plating CdTe on nanostructures made of different materials, which would be of interest in various applications.

  19. High-efficiency, flexible CdTe solar cells on ultra-thin glass substrates

    Energy Technology Data Exchange (ETDEWEB)

    Mahabaduge, H. P.; Rance, W. L.; Burst, J. M.; Reese, M. O.; Gessert, T. A.; Metzger, W. K.; Barnes, T. M. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Meysing, D. M.; Wolden, C. A.; Li, J.; Beach, J. D. [Colorado School of Mines, Golden, Colorado 80401 (United States); Garner, S. [Corning, Inc., Corning, New York 14831 (United States)

    2015-03-30

    Flexible, high-efficiency, low-cost solar cells can enable applications that take advantage of high specific power, flexible form factors, lower installation and transportation costs. Here, we report a certified record efficiency of 16.4% for a flexible CdTe solar cell that is a marked improvement over the previous standard (14.05%). The improvement was achieved by replacing chemical-bath-deposited CdS with sputtered CdS:O and also replacing the high-temperature sputtered ZnTe:Cu back contact layer with co-evaporated and rapidly annealed ZnTe:Cu. We use quantum efficiency and capacitance-voltage measurements combined with device simulations to identify the reasons for the increase in efficiency. Both device simulations and experimental results show that higher carrier density can quantitatively account for the increased open circuit voltage (V{sub OC}) and Fill Factor (FF), and likewise, the increase in short circuit current density (J{sub SC}) can be attributed to the more transparent CdS:O.

  20. Carrier generation and collection in CdS/CdSe-sensitized SnO2 solar cells exhibiting unprecedented photocurrent densities.

    Science.gov (United States)

    Hossain, Md Anower; Jennings, James Robert; Koh, Zhen Yu; Wang, Qing

    2011-04-26

    CdS/CdSe-sensitized nanostructured SnO(2) solar cells exhibiting record short-circuit photocurrent densities have been fabricated. Under simulated AM 1.5, 100 mW cm(-2) illumination, photocurrents of up to 17.40 mA cm(-2) are obtained, some 32% higher than that achieved by otherwise identical semiconductor-sensitized solar cells (SSCs) employing nanostructured TiO(2). An overall power conversion efficiency of 3.68% has been achieved for the SnO(2)-based SSCs, which compares very favorably to efficiencies obtained by the TiO(2)-based SSCs. The characteristics of these SSCs were studied in more detail by optical measurements, spectral incident photon-to-current efficiency (IPCE) measurements, and impedance spectroscopy (IS). The apparent conductivity of sensitized SnO(2) photoanodes is apparently too large to be measured by IS, yet for otherwise identical TiO(2) electrodes, clear electron transport features could be observed in impedance spectra, tacitly implying slower charge transport in TiO(2). Despite this, electron diffusion length measurements suggest that charge collection losses are negligible in both kinds of cell. SnO(2)-based SSCs exhibit higher IPCEs compared with TiO(2)-based SSCs which, considering the similar light harvesting efficiencies and the long electron diffusion lengths implied by IS, is likely to be due to a superior charge separation yield. The resistance to charge recombination is also larger in SnO(2)-based SSCs at any given photovoltage, and open-circuit photovoltages under simulated AM 1.5, 100 mW cm(-2) illumination are only 26-56 mV lower than those obtained for TiO(2)-based SSCs, despite the conduction band minimum of SnO(2) being hundreds of millielectronvolts lower than that of TiO(2).

  1. Novel Contact Materials for Improved Performance CdTe Solar Cells Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Rockett, Angus [Colorado School of Mines, Golden, CO (United States); Marsillac, Sylvain [Old Dominion Univ., Norfolk, VA (United States); Collins, Robert [Univesity of Toledo

    2018-04-15

    This program has explored a number of novel materials for contacts to CdTe solar cells in order to reduce the back contact Schottky barrier to zero and produce an ohmic contact. The project tested a wide range of potential contact materials including TiN, ZrN, CuInSe2:N, a-Si:H and alloys with C, and FeS2. Improved contacts were achieved with FeS2. As part of understanding the operation of the devices and controlling the deposition processes, a number of other important results were obtained. In the process of this project and following its conclusion it led to research that resulted in seven journal articles, nine conference publications, 13 talks presented at conferences, and training of eight graduate students. The seven journal articles were published in 2015, 2016, and 2017 and have been cited, as of March 2018, 52 times (one cited 19 times and two cited 11 times). We demonstrated high levels of doping of CIS with N but electrical activity of the resulting N was not high and the results were difficult to reproduce. Furthermore, even with high doping the contacts were not good. Annealing did not improve the contacts. A-Si:H was found to produce acceptable but unstable contacts, degrading even over a day or two, apparently due to H incorporation into the CdTe. Alloying with C did not improve the contacts or stability. The transition metal nitrides produced Schottky type contacts for all materials tested. While these contacts were found to be unsatisfactory, we investigated FeS2 and found this material to be effective and comparable to the best contacts currently available. The contacts were found to be chemically stable under heat treatment and preferable to Cu doped contacts. Thus, we demonstrated an improved contact material in the course of this project. In addition, we developed new ways of controlling the deposition of CdTe and other materials, demonstrated the nature of defects in CdTe, and studied the distribution of conductivity and carrier type in CdTe

  2. Impact of annealing on the chemical structure and morphology of the thin-film CdTe/ZnO interface

    Energy Technology Data Exchange (ETDEWEB)

    Horsley, K., E-mail: horsley5@unlv.nevada.edu; Hanks, D. A.; Weir, M. G. [Department of Chemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154 (United States); Beal, R. J. [Materials Science and Engineering Department, University of Arizona, Tucson, Arizona 85721 (United States); Wilks, R. G. [Solar Energy Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), 14109 Berlin (Germany); Blum, M. [Department of Chemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154 (United States); Advanced Light Source (ALS), Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Häming, M. [Department of Chemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154 (United States); Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen (Germany); Hofmann, T. [Department of Chemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154 (United States); Bundeswehr Research Institute for Materials, Fuels and Lubricants (WIWeB), Institutsweg 1, 85435 Erding (Germany); Weinhardt, L. [Department of Chemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154 (United States); Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen (Germany); ANKA Synchrotron Radiation Facility, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen (Germany); and others

    2014-07-14

    To enable an understanding and optimization of the optoelectronic behavior of CdTe-ZnO nanocomposites, the morphological and chemical properties of annealed CdTe/ZnO interface structures were studied. For that purpose, CdTe layers of varying thickness (4–24 nm) were sputter-deposited on 100 nm-thick ZnO films on surface-oxidized Si(100) substrates. The morphological and chemical effects of annealing at 525 °C were investigated using X-ray Photoelectron Spectroscopy (XPS), X-ray-excited Auger electron spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy, and atomic force microscopy. We find a decrease of the Cd and Te surface concentration after annealing, parallel to an increase in Zn and O signals. While the as-deposited film surfaces show small grains (100 nm diameter) of CdTe on the ZnO surface, annealing induces a significant growth of these grains and separation into islands (with diameters as large as 1 μm). The compositional change at the surface is more pronounced for Cd than for Te, as evidenced using component peak fitting of the Cd and Te 3d XPS peaks. The modified Auger parameters of Cd and Te are also calculated to further elucidate the local chemical environment before and after annealing. Together, these results suggest the formation of tellurium and cadmium oxide species at the CdTe/ZnO interface upon annealing, which can create a barrier for charge carrier transport, and might allow for a deliberate modification of interface properties with suitably chosen thermal treatment parameters.

  3. The influence of physical and technological magnetron sputtering modes on the structure and optical properties of CdS and CdTe films

    Directory of Open Access Journals (Sweden)

    G.S. Khrypunov

    2017-07-01

    Full Text Available To create technology for preparation of CdS and CdTe thin films by direct current magnetron sputtering, the influence of physical and technological condensation modes on the crystal structure and optical properties of these films were investigated. The laboratory method of DC magnetron sputtering with preheating of the target for the mentioned films on glass substrates was developed. We obtained the CdS layers with hexagonal structure 150…200 nm thick under conditions when the plasma discharge current density was 1.1 mA/cm2 and the deposition rate – 30…40 nm/min. The bandgap in the obtained CdS films is Eg = 2.38…2.41 eV. After annealing in vacuum, the optical transparence of CdS films reaches 80…90%, which allows to use these films as a transparent window layer in solar cells based on heterojunctions of CdS/CdTe. When the plasma discharge current density is 2.2…5.4 mA/cm2 and the deposition rate is 200 nm/min, we obtained CdTe layers with hexagonal structure up to 5 µm thick. The transmittance of CdTe films with hexagonal structure in the wavelength range of the visible spectrum is up to 5%, and in the infrared spectral range is about 60%. The bandgap in the obtained CdTe layers of different thickness is 1.52…1.54 eV. After chloride treatment as a result of the phase transition wurtzite–sphalerite, the investigated CdTe films contain only the stable cubic structure and can be used as a base layer of solar cells.

  4. Optimization of the front contact to minimize short-circuit current losses in CdTe thin-film solar cells

    Science.gov (United States)

    Kephart, Jason Michael

    . In this work numerous HRT layers were examined beginning with an empirical optimization to create a SnO2-based HRT which allows significantly reduced CdS thickness while maintaining diode quality. The role of this layer was explored through measurement of band alignment parameters via photoemission. These results suggest a negative correlation of work function to device open-circuit voltage, which implies that non-ideal band alignment at the front interface of CdTe is in large part responsible for the loss of electronic quality. Several scenarios explored through 1-dimensional modeling in the SCAPS program corroborate this theory. A sputter-deposited (Mg,Zn)O layer was tested which allows for complete elimination of the CdS window layer with an increase in open-circuit voltage and near complete transmission of all above-bandgap light. An additional window layer material---sputtered, oxygenated CdS---was explored for its transparency. This material was found only to produce high efficiency devices with an effective buffer layer such as the optimized SnO2-base HRT. The dependence of chemical, optical, electrical, and device properties on oxygen content was explored, and the stability of these devices was determined to depend largely on the minimization of copper in the device. Both sputter-deposited alloy window layers appeared to have tunable electron affinity which was critical to optimizing band alignment and therefore device efficiency. Several scenarios explored through 1-dimensional modeling in the SCAPS program corroborate this theory. Both window layers allowed an AM1.5G efficiency increase from a baseline of approximately 13% to 16%.

  5. Ultraviolet radiation synthesis of water dispersed CdTe/CdS/ZnS core-shell-shell quantum dots with high fluorescence strength and biocompatibility

    Science.gov (United States)

    Xu, Bin; Cai, Bing; Liu, Ming; Fan, Hongsong

    2013-05-01

    This study explored a simple and fast method utilizing ultraviolet (UV) irradiation to synthesize CdTe/CdS/ZnS QDs in aqueous solution. Based on the reaction of photolysis and chemical deposition, the CdS and ZnS shell can be successively deposited around the thiol-capped CdTe cores through the interaction of Cd2+/Zn2+ and S2- produced by UV irradiation. The effect of the UV irradiation time, the ratios of thioglycolic acid (TGA)/Cd and TGA/Zn on the shell formation, shell stability, and the photoluminescence (PL) intensity of the QDs, was systematically investigated. Keeping the ratio of TGA/Cd, increasing UV irradiation time from 30 to 120 s, the blue-shift of the fluorescence emission peak position of CdTe/CdS QDs was observed. As the irradiation time increased continuously from 120 to 300 s, the red-shift of the emission peak position was observed. In the total irradiation time, the PL intensity of all the samples was enhanced. By applying 300 s irradiation on the samples, the emission peak was blue-shifted at a fixed TGA/Cd ratio of 1:1 and red-shifted at the ratios of 2:1, 4:1, 8:1, and 13:1. The PL intensity reached its highest value at the ratio of 2:1. The effect of TGA/Zn ratio on ZnS shell formation showed a similar progress. Under an optimum synthesized reaction condition, the particle sizes of CdTe core, CdTe/CdS core-shell and CdTe/CdS/ZnS core-shell-shell QDs were 2.6 nm, 3.4 nm, and 4.6 nm respectively. This study confirmed that with the core-shell-shell structure, CdTe/CdS/ZnS QDs had high anti-oxidability, photostability, and low toxicity. Therefore they can be further used in cell imaging efficiently.

  6. Ultraviolet radiation synthesis of water dispersed CdTe/CdS/ZnS core-shell-shell quantum dots with high fluorescence strength and biocompatibility.

    Science.gov (United States)

    Xu, Bin; Cai, Bing; Liu, Ming; Fan, Hongsong

    2013-05-24

    This study explored a simple and fast method utilizing ultraviolet (UV) irradiation to synthesize CdTe/CdS/ZnS QDs in aqueous solution. Based on the reaction of photolysis and chemical deposition, the CdS and ZnS shell can be successively deposited around the thiol-capped CdTe cores through the interaction of Cd²⁺/Zn²⁺ and S²⁻ produced by UV irradiation. The effect of the UV irradiation time, the ratios of thioglycolic acid (TGA)/Cd and TGA/Zn on the shell formation, shell stability, and the photoluminescence (PL) intensity of the QDs, was systematically investigated. Keeping the ratio of TGA/Cd, increasing UV irradiation time from 30 to 120 s, the blue-shift of the fluorescence emission peak position of CdTe/CdS QDs was observed. As the irradiation time increased continuously from 120 to 300 s, the red-shift of the emission peak position was observed. In the total irradiation time, the PL intensity of all the samples was enhanced. By applying 300 s irradiation on the samples, the emission peak was blue-shifted at a fixed TGA/Cd ratio of 1:1 and red-shifted at the ratios of 2:1, 4:1, 8:1, and 13:1. The PL intensity reached its highest value at the ratio of 2:1. The effect of TGA/Zn ratio on ZnS shell formation showed a similar progress. Under an optimum synthesized reaction condition, the particle sizes of CdTe core, CdTe/CdS core-shell and CdTe/CdS/ZnS core-shell-shell QDs were 2.6 nm, 3.4 nm, and 4.6 nm respectively. This study confirmed that with the core-shell-shell structure, CdTe/CdS/ZnS QDs had high anti-oxidability, photostability, and low toxicity. Therefore they can be further used in cell imaging efficiently.

  7. Hydrothermal synthesis of CdTe QDs: Their luminescence quenching in the presence of bio-molecules and observation of bistable memory effect in CdTe QD/PEDOT:PSS heterostructure

    International Nuclear Information System (INIS)

    Khatei, Jayakrishna; Koteswara Rao, K.S.R.

    2011-01-01

    Highlights: · CdTe QD has been prepared by modified hydrothermal method in room ambient. · Luminescence quenching of CdTe QDs in the presence of bio-molecules demonstrated. · The CdTe QDs shows memory effect (electrical bistability). - Abstract: We report one-pot hydrothermal synthesis of nearly mono-disperse 3-mercaptopropionic acid capped water-soluble cadmium telluride (CdTe) quantum dots (QDs) using an air stable Te source. The optical and electrical characteristics were also studied here. It was shown that the hydrothermal synthesis could be tuned to synthesize nano structures of uniform size close to nanometers. The emissions of the CdTe QDs thus synthesized were in the range of 500-700 nm by varying the duration of synthesis. The full width at half maximum (FWHM) of the emission peaks is relatively narrow (40-90 nm), which indicates a nearly uniform distribution of QD size. The structural and optical properties of the QDs were characterized by transmission electron microscopy (TEM), photoluminescence (PL) and Ultraviolet-visible (UV-Vis) spectroscopy. The photoluminescence quenching of CdTe QDs in the presence of L-cysteine and DNA confirms its biocompatibility and its utility for biosensing applications. The room temperature current-voltage characteristics of QD film on ITO coated glass substrate show an electrically induced switching between states with high and low conductivities. The phenomenon is explained on the basis of charge confinement in quantum dots.

  8. Evaluation of Polarization Effects of e(-) Collection Schottky CdTe Medipix3RX Hybrid Pixel Detector

    OpenAIRE

    Astromskas, V; Gimenez, EN; Lohstroh, A; Tartoni, N

    2016-01-01

    This paper focuses on the evaluation of operational conditions such as temperature, exposure time and flux on the polarization of a Schottky electron collection CdTe detector. A Schottky e- collection CdTe Medipix3RX hybrid pixel detector was developed as a part of the CALIPSO-HIZPAD2 EU project. The 128 ×128 pixel matrix and 0.75 mm thick CdTe sensor bump-bonded to Medipix3RX readout chips enabled the study of the polarization effects. Single and quad module Medipix3RX chips were used which ...

  9. One-step aqueous synthesis of graphene-CdTe quantum dot-composed nanosheet and its enhanced photoresponses.

    Science.gov (United States)

    Lu, Zhisong; Guo, Chun Xian; Yang, Hong Bin; Qiao, Yan; Guo, Jun; Li, Chang Ming

    2011-01-15

    Although CdTe nanocrystal has been applied in quantum dot (QD)-based solar cells, there is no report on a graphene-CdTe QD hybrid system and its photoresponses. In this work, graphene-CdTe QD composed nanosheets were one-step synthesized in aqueous solution using a hydrothermal method and demonstrated enhanced photoresponses, rendering potentials in optoelectronics applications. This work could provide an environmental-friendly and universal approach to fabricate graphene-based hybrid nanomaterials for various applications. Copyright © 2010 Elsevier Inc. All rights reserved.

  10. Constructing Well-Ordered CdTe/TiO2Core/Shell Nanowire Arrays for Solar Energy Conversion.

    Science.gov (United States)

    Al-Haddad, Ahmed; Wang, Zijie; Zhou, Min; Tarish, Samar; Vellacheri, Ranjith; Lei, Yong

    2016-10-01

    Well-ordered CdTe/TiO 2 heteronanostructure arrays are fabricated via a convenient anodic aluminum oxide template-directed approach and applied to photoelectrochemistry and solar energy devices. Both the CdTe and TiO 2 present a decent crystalline quality. In comparison to the photoanode with only TiO 2 nanotube array, the CdTe/TiO 2 heteronanostructure electrodes possess a dramatic performance improvement. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Investigation of Processing, Microstructures and Efficiencies of Polycrystalline CdTe Photovoltaic Films and Devices

    Science.gov (United States)

    Munshi, Amit Harenkumar

    CdTe based photovoltaics have been commercialized at multiple GWs/year level. The performance of CdTe thin film photovoltaic devices is sensitive to process conditions. Variations in deposition temperatures as well as other treatment parameters have a significant impact on film microstructure and device performance. In this work, extensive investigations are carried out using advanced microstructural characterization techniques in an attempt to relate microstructural changes due to varying deposition parameters and their effects on device performance for cadmium telluride based photovoltaic cells deposited using close space sublimation (CSS). The goal of this investigation is to apply advanced material characterization techniques to aid process development for higher efficiency CdTe based photovoltaic devices. Several techniques have been used to observe the morphological changes to the microstructure along with materials and crystallographic changes as a function of deposition temperature and treatment times. Traditional device structures as well as advanced structures with electron reflector and films deposited on Mg1-xZnxO instead of conventional CdS window layer are investigated. These techniques include Scanning Electron Microscopy (SEM) with Electron Back Scattered Diffraction (EBSD) and Energy dispersive X-ray spectroscopy (EDS) to study grain structure and High Resolution Transmission Electron Microscopy (TEM) with electron diffraction and EDS. These investigations have provided insights into the mechanisms that lead to change in film structure and device performance with change in deposition conditions. Energy dispersive X-ray spectroscopy (EDS) is used for chemical mapping of the films as well as to understand interlayer material diffusion between subsequent layers. Electrical performance of these devices has been studied using current density vs voltage plots. Devices with efficiency over 18% have been fabricated on low cost commercial glass substrates

  12. Technology support for initiation of high-throughput processing of thin-film CdTe PV modules. Phase 1 technical report, March 14, 1995--March 13, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Sasala, R.; Powell, R.; Dorer, G. [Solar Cells, Inc., Toledo, OH (United States)

    1996-06-01

    Progress has been made in the important areas of stability, advanced deposition techniques, efficiency, the back contact, no-contact film diagnostics (photoluminescence) and Cd waste control. The progress in stability has been in both the demonstration of devices maintaining at least 90% of the initial efficiency for over 19,000 hours of continuous light soak and the development of methods which can accurately predict long term behavior based on the first 5,000--10,000 hours of life. Experiments were conducted to determine if device behavior could be accelerated with thermal or voltage stresses. Notable achievements in deposition technology include depositing CdTe on a 3,600 cm{sup 2} substrate at 600 torr and designing and fabricating a new deposition feed system with a remote semiconductor source. The efficiency has been increased on small area devices to 13.3% by decreasing the thickness of the CdS and of the glass substrate. Work also focused on using a high resistivity SnO{sub 2} buffer layer between the TCO and thin CdS to help preserve the open-circuit voltage while increasing the current-density. The back contacting process has been simplified by replacing the wet post-deposition etch with a vapor Te deposition step on small area devices. Results show that the devices perform comparably in efficiency but better in stability under light-soaking and open-circuit conditions. Preliminary studies of the correlation between CdS photoluminescence after the chloride treatment and the final device efficiency have shown a positive correlation which may be applicable for in-line quality control. The final area of progress was through the successful demonstration of preventing at least 99.9% of all incoming Cd from leaving in an uncontrolled manner through the land, air or water.

  13. Atomic-resolution characterization of the effects of CdCl2 treatment on poly-crystalline CdTe thin films

    Science.gov (United States)

    Paulauskas, T.; Buurma, C.; Colegrove, E.; Guo, Z.; Sivananthan, S.; Chan, M. K. Y.; Klie, R. F.

    2014-08-01

    Poly-crystalline CdTe thin films on glass are used in commercial solar-cell superstrate devices. It is well known that post-deposition annealing of the CdTe thin films in a CdCl2 environment significantly increases the device performance, but a fundamental understanding of the effects of such annealing has not been achieved. In this Letter, we report a change in the stoichiometry across twin boundaries in CdTe and propose that native point defects alone cannot account for this variation. Upon annealing in CdCl2, we find that the stoichiometry is restored. Our experimental measurements using atomic-resolution high-angle annular dark field imaging, electron energy-loss spectroscopy, and energy dispersive X-ray spectroscopy in a scanning transmission electron microscope are supported by first-principles density functional theory calculations.

  14. Molecular beam epitaxy of CdSe epilayers and quantum wells on ZnTe substrate

    International Nuclear Information System (INIS)

    Park, Y.M.; Andre, R.; Kasprzak, J.; Dang, Le Si; Bellet-Amalric, E.

    2007-01-01

    We have grown zinc-blende cadmium selenide (CdSe) epilayers on ZnTe-(0 0 1) substrate by molecular beam epitaxy (MBE). By controlling the substrate temperature and beam-equivalent pressure (BEP) ratio, of Se to Cd, we determined the most suitable growth condition based on reflection high-energy electron diffraction (RHEED) pattern. At a substrate temperature of 280 deg. C and a BEP ratio of 3.6, the RHEED pattern showed a V-like feature, indicating a rough surface with facets. As the substrate temperature was increased to 360 deg. C at the same BEP ratio, a V-like RHEED pattern moved to a clear streaky pattern. Moreover when the BEP ratio was increased to 4.8 at 360 deg. C of substrate temperature, a clear (2 x 1) reconstruction of the CdSe layer was observed. A CdSe/CdMgSe single quantum well structure was also grown on ZnTe-(0 0 1) substrate by MBE. The RHEED pattern showed a clear (2 x 1) surface reconstruction during the growth. By photoluminescence measurement, a good optical property of the structure was obtained

  15. Interaction of different thiol-capped CdTe quantum dots with bovine serum albumin

    International Nuclear Information System (INIS)

    Wang Qisui; Zhang Xiaolei; Zhou Xiaolan; Fang Tingting; Liu Pengfei; Liu Peng; Min Xinmin; Li, Xi

    2012-01-01

    Due to their unique optical properties, quantum dots (QDs) are rapidly revolutionizing many areas of medicine and biology. Despite the remarkable speed of development of nanoscience, relatively little is known about the interaction of nanoscale objects with organism. In this work, interaction of CdTe QDs coated with mercaptopropanoic acid (MPA), L-cysteine (L-cys), and glutathione (GSH) with bovine serum albumin (BSA) was investigated. Fluorescence (FL), UV–vis absorption, and circular dichroism (CD) spectra methods were used. The Stern-Volmer quenching constant (K sv ) at different temperatures, corresponding thermodynamic parameters (ΔH, ΔG and ΔS), and information of the structural features of BSA were gained. We found that QDs can effectively quench the FL of BSA in a ligand-dependent manner, electrostatic interactions play a major role in the binding reaction, and the nature of quenching is static, resulting in forming QDs-BSA complexes. The CD spectra showed that the secondary and tertiary structure of BSA was changed. This study contributes to a better understanding of the ligand effects on QDs-proteins interactions, which is a critical issue for the applications in vivo. - Highlights: ► The interaction between three thiol-capped QDs and BSA by UV–vis, FL, and CD spectra. ► The bio-effect of CdTe QDs on BSA was a ligand-dependent manner. ► The thermodynamic parameters and the structural features of BSA were gained.

  16. Structural and chemical evolution of the CdS:O window layer during individual CdTe solar cell processing steps

    Energy Technology Data Exchange (ETDEWEB)

    Abbas, A.; Meysing, D. M.; Reese, M. O.; Barnes, T. M.; Walls, J. M.; Wolden, C. A.

    2018-01-01

    Oxygenated cadmium sulfide (CdS:O) is often used as the n-type window layer in high-performance CdTe heterojunction solar cells. The as-deposited layer prepared by reactive sputtering is XRD amorphous, with a bulk composition of CdS0.8O1.2. Recently it was shown that this layer undergoes significant transformation during device fabrication, but the roles of the individual high temperature processing steps was unclear. In this work high resolution transmission electron microscopy coupled to elemental analysis was used to understand the evolution of the heterojunction region through the individual high temperature fabrication steps of CdTe deposition, CdCl2 activation, and back contact activation. It is found that during CdTe deposition by close spaced sublimation at 600 degrees C the CdS:O film undergoes recrystallization, accompanied by a significant (~30%) reduction in thickness. It is observed that oxygen segregates during this step, forming a bi-layer morphology consisting of nanocrystalline CdS adjacent to the tin oxide contact and an oxygen-rich layer adjacent to the CdTe absorber. This bilayer structure is then lost during the 400 degrees C CdCl2 treatment where the film transforms into a heterogeneous structure with cadmium sulfate clusters distributed randomly throughout the window layer. The thickness of window layer remains essentially unchanged after CdCl2 treatment, but a ~25 nm graded interfacial layer between CdTe and the window region is formed. Finally, the rapid thermal processing step used to activate the back contact was found to have a negligible impact on the structure or composition of the heterojunction region.

  17. Improvement of the sensitivity of CdTe detectors in the high energy regions

    Energy Technology Data Exchange (ETDEWEB)

    Nishizawa, Hiroshi; Ikegami, Kazunori; Takashima, Kazuo; Usami, Teruo [Mitsubishi Electric Corp., Tokyo (Japan); Yamamoto, Takayoshi

    1996-07-01

    In order to improve the efficiency of the full energy peak in the high energy regions, we had previously suggested a multi-layered structure of CdTe elements and have since confirmed the sensitivity improvement of the full energy peak. And furthermore, we have suggested a new type structure of multi-layered elements in this paper and we confirmed that the efficiency of the full energy peak became higher and that more proper energy spectra were obtained by our current experiment than by the detector with the conventional structure. This paper describes a simulation and experiment to improve the efficiency of the full energy peak and to obtain the more proper energy spectra of {sup 137}Cs (662keV) and {sup 60}Co (1.17 and 1.33MeV) using the new structure of CdTe detector. (J.P.N.)

  18. CdTe quantum dot as a fluorescence probe for vitamin B12 in dosage form

    Science.gov (United States)

    Vaishnavi, E.; Renganathan, R.

    2013-11-01

    We here report the CdTe quantum dot (CdTe QDs)-based sensor for probing vitamin B12 derivatives in aqueous solution. In this paper, simple and sensitive fluorescence quenching measurements has been employed. The Stern-Volmer constant (KSV), quenching rate constant (kq) and binding constant (K) were rationalized from fluorescence quenching measurement. Furthermore, the fluorescence resonance energy transfer (FRET) mechanism was discussed. This method was applicable over the concentration ranging from 1 to 14 μg/mL (VB12) with correlation coefficient of 0.993. The limit of detection (LOD) of VB12 was found to be 0.15 μg/mL. Moreover, the present approach opens a simple pathway for developing cost-effective, sensitive and selective QD-based fluorescence sensors/probes for biologically significant VB12 in pharmaceutical sample with mean recoveries in the range of 100-102.1%.

  19. Electrodeposition and characterization of CdSe x-Te 1- x semiconducting thin films

    Science.gov (United States)

    Benamar, E.; Rami, M.; Fahoume, M.; Chraibi, F.; Ennaoui, A.

    1999-07-01

    Thin polycrystalline films of cadmium chalcogenides CdSe xTe 1-x ( 0 ≤ x ≤ 1) have been prepared by electrochemical plating on ITO (indium tin oxide) coated glass substrates from an acid sulfate solution at 90 °C. Structural, morphological and compositional studies of the deposited films are reported as a function of the x coefficient. XRD analysis shows that all deposits have a cubic structure with a preferred orientation along the (111) direction. The composition in the films is found to vary linearly with the composition in the solution. The increase in the selenium content x in the CdSe xTe 1-x films decreases the lattice constant and increases the band gap. Nevertheless this latter presents a minimum for x = 0.27.

  20. Evaluation of CdZnTe detector for personal surveymeter applications

    International Nuclear Information System (INIS)

    Lee, H.K.; Choi, M.J.

    1996-01-01

    In this paper, we report the fabrication and characterization of the personal surveymeter using home made Cd 0.8 Zn 0.2 Te detector for the field application. The detector structure is the bulk type and Au electrode is formed by electroless deposition method. The properties of Au film were analyzed by the AFM, RBS and Auger spectroscopy. The reliability test results showed that TO-5 packaged CdZnTe detector had good stability. When the detector bias voltage was higher, the detector response was more stable at the low temperature. The personal surveymeter also showed good linear response about gamma dose rate from 1 mRad/hr to 500 Rad/hr