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Sample records for cdte crystals grown

  1. Characterization of the vapour grown CdTe crystals for high energy radiation detectors

    Science.gov (United States)

    Popovych, V. D.; Virt, I. S.; Tsutsura, D. I.; Tsybrii (Ivasiv), Z. F.; Sizov, F. F.; Parfenjuk, O. A.; Ilashchuk, M. I.

    2006-03-01

    Growth steps and set-up for the pure and chlorine doped cadmium telluride single crystals preparation by a vertical configuration of sublimation travelling heater method without seeding are described. The structural, electrical and transport properties of as-grown material were investigated by different techniques: infrared transmission spectroscopy, double-crystal X-ray diffractometry, Hall effect, conductivity, photoelectric measurements and chemical etching. It was concluded that the most suitable material for fabrication of X-ray and -ray non-cooling detectors are single crystals doped with Cl in the range of NCl = 1018-1019 cm-3.

  2. Characterization of the vapour grown CdTe crystals for high energy radiation detectors

    International Nuclear Information System (INIS)

    Popovych, V.D.; Tsutsura, D.I.; Virt, I.S.; Tsybrii-Ivasiv, Z.F.; Sizov, F.F.; Parfenjuk, O.A.; Ilashchuk, M.I.

    2006-01-01

    Growth steps and set-up for the pure and chlorine doped cadmium telluride single crystals preparation by a vertical configuration of sublimation travelling heater method without seeding are described. The structural, electrical and transport properties of as-grown material were investigated by different techniques: infrared transmission spectroscopy, double-crystal X-ray diffractometry, Hall effect, conductivity, photoelectric measurements and chemical etching. It was concluded that the most suitable material for fabrication of X-ray and γ-ray non-cooling detectors are single crystals doped with Cl in the range of N Cl =10 18 -10 19 cm -3 . (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. 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.)

  4. 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.)

  5. 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.

  6. Synthesis and characterization of CdTe nanostructures grown by RF magnetron sputtering method

    Science.gov (United States)

    Akbarnejad, Elaheh; Ghoranneviss, Mahmood; Hantehzadeh, Mohammad Reza

    2017-08-01

    In this paper, we synthesize Cadmium Telluride nanostructures by radio frequency (RF) magnetron sputtering system on soda lime glass at various thicknesses. The effect of CdTe nanostructures thickness on crystalline, optical and morphological properties has been studied by means of X-ray diffraction (XRD), UV-VIS-NIR spectrophotometry, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), respectively. The XRD parameters of CdTe nanostructures such as microstrain, dislocation density, and crystal size have been examined. From XRD analysis, it could be assumed that increasing deposition time caused the formation of the wurtzite hexagonal structure of the sputtered films. Optical properties of the grown nanostructures as a function of film thickness have been observed. All the films indicate more than 60% transmission over a wide range of wavelengths. The optical band gap values of the films have obtained in the range of 1.62-1.45 eV. The results indicate that an RF sputtering method succeeded in depositing of CdTe nanostructures with high purity and controllable physical properties, which is appropriate for photovoltaic and nuclear detector applications.

  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. 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.

  10. 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.

  11. 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)

  12. Use of photoluminescence spectroscopy to characterize the crystalline quality of CdTe films grown by a modified CSVT technique

    International Nuclear Information System (INIS)

    Mendoza-Alvarez, J.G.; Sanchez-Sinencio, F.; Zelaya, O.; Gonzalez-Hernandez, Y.J.; Cardenas, M.; Chao, S.S.

    1987-01-01

    The authors have employed photoluminescence measurements at 10-300 0 K to study the effects of deposition parameters, surface preparation and heat treatment on the properties of CdTe polycrystalline thin films. The films were grown using a modified hot wall close spaced vapor transport system. The authors found strong differences in the photoluminescence spectra of samples grown under different conditions. Heat treatments in the as-grown samples increase the average particle size and reduce the native defect density

  13. 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

  14. Spectroscopic and microscopic investigation of MBE-grown CdTe (211)B epitaxial thin films on GaAs (211)B substrates

    Science.gov (United States)

    Özden, Selin; Koc, Mumin Mehmet

    2018-03-01

    CdTe epitaxial thin films, for use as a buffer layer for HgCdTe defectors, were grown on GaAs (211)B using the molecular beam epitaxy method. Wet chemical etching (Everson method) was applied to the epitaxial films using various concentrations and application times to quantify the crystal quality and dislocation density. Surface characterization of the epitaxial films was achieved using Atomic force microscopy and Scanning electron microscopy (SEM) before and after each treatment. The Energy Dispersive X-Ray apparatus of SEM was used to characterize the chemical composition. Untreated CdTe films show smooth surface characteristics with root mean square (RMS) roughnesses of 1.18-3.89 nm. The thicknesses of the CdTe layers formed were calculated via FTIR spectrometry and obtained by ex situ spectroscopic ellipsometry. Raman spectra were obtained for various temperatures. Etch pit densities (EPD) were measured, from which it could be seen that EPD changes between 1.7 × 108 and 9.2 × 108 cm-2 depending on the concentration of the Everson etch solution and treatment time. Structure, shape and depth of pits resulting from each etch pit implementation were also evaluated. Pit widths varying between 0.15 and 0.71 µm with heights varying between 2 and 80 nm were observed. RMS roughness was found to vary by anything from 1.56 to 26 nm.

  15. Surface defect states in MBE-grown CdTe layers

    Energy Technology Data Exchange (ETDEWEB)

    Olender, Karolina; Wosinski, Tadeusz; Fronc, Krzysztof; Tkaczyk, Zbigniew; Chusnutdinow, Sergij; Karczewski, Grzegorz [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland)

    2014-02-21

    Semiconductor surface plays an important role in the technology of semiconductor devices. In the present work we report results of our deep-level transient spectroscopy (DLTS) investigations of surface defect states in nitrogen doped p-type CdTe layers grown by the molecular-beam epitaxy technique. We observed a deep-level trap associated with surface states, with the activation energy for hole emission of 0.33 eV. DLTS peak position in the spectra for this trap, and its ionization energy, strongly depend on the electric field. Our measurements allow to determine a mechanism responsible for the enhancement of hole emission rate from the traps as the phonon-assisted tunnel effect. Density of surface defect states significantly decreased as a result of passivation in ammonium sulfide. Capacitance-voltage measurements confirmed the results obtained by the DLTS technique.

  16. Energy Band Gap, Intrinsic Carrier Concentration and Fermi Level of CdTe Bulk Crystal between 304 K and 1067 K

    Science.gov (United States)

    Su, Ching-Hua

    2007-01-01

    Optical transmission measurements were performed on CdTe bulk single crystal. It was found that when a sliced and polished CdTe wafer was used, a white film started to develop when the sample was heated above 530 K and the sample became opaque. Therefore, a bulk crystal of CdTe was first grown in the window area by physical vapor transport; the optical transmission was then measured and from which the energy band gap was derived between 304 and 1067 K. The band gaps of CdTe can be fit well as a function of temperature using the Varshini expression: Eg (e V) = 1.5860 - 5.9117xl0(exp -4) T(sup 2)/(T + 160). Using the band gap data, the high temperature electron-hole equilibrium was calculated numerically by assuming the Kane's conduction band structure and a heavy-hole parabolic valance band. The calculated intrinsic carrier concentrations agree well with the experimental data reported previously. The calculated intrinsic Fermi levels between 270 and 1200 K were also presented.

  17. 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.

  18. 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

  19. 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

  20. 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.

  1. Electroplating of CdTe Thin Films from Cadmium Sulphate Precursor and Comparison of Layers Grown by 3-Electrode and 2-Electrode Systems

    Directory of Open Access Journals (Sweden)

    Imyhamy M. Dharmadasa

    2017-01-01

    Full Text Available Electrodeposition of CdTe thin films was carried out from the late 1970s using the cadmium sulphate precursor. The solar energy group at Sheffield Hallam University has carried out a comprehensive study of CdTe thin films electroplated using cadmium sulfate, cadmium nitrate and cadmium chloride precursors, in order to select the best electrolyte. Some of these results have been published elsewhere, and this manuscript presents the summary of the results obtained on CdTe layers grown from cadmium sulphate precursor. In addition, this research program has been exploring the ways of eliminating the reference electrode, since this is a possible source of detrimental impurities, such as K+ and Ag+ for CdS/CdTe solar cells. This paper compares the results obtained from CdTe layers grown by three-electrode (3E and two-electrode (2E systems for their material properties and performance in CdS/CdTe devices. Thin films were characterized using a wide range of analytical techniques for their structural, morphological, optical and electrical properties. These layers have also been used in device structures; glass/FTO/CdS/CdTe/Au and CdTe from both methods have produced solar cells to date with efficiencies in the region of 5%–13%. Comprehensive work carried out to date produced comparable and superior devices fabricated from materials grown using 2E system.

  2. 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.

  3. Ellipsometry of rough CdTe(211)B-Ge(211) surfaces grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Badano, Giacomo; Ballet, Philippe; Zanatta, Jean-Paul; Baudry, Xavier; Million, Alain; Garland, James W.

    2006-01-01

    The effect of surface roughness on the ellipsometric response of semiconductor surfaces is investigated. CdTe(211)B layers were grown on Ge(211) by molecular beam epitaxy using less than optimal growth conditions to enhance the formation of surface roughness. Their optical properties, measured by rotating-compensator ellipsometry, showed small but significant sample-to-sample differences not explainable in terms of nanometer-scale roughness. A critical-point analysis established that the critical-point structure of the dielectric function was the same for all samples. This result suggested that the observed sample-to-sample variations were due to macroscopic roughness, which scatters off-specular light into the detector, thereby causing errors. We introduced tentative corrections for off-specular reflection that fitted the observed differences and thus supported the idea that off-specular reflection was responsible for the observed differences. These results were obtained using CdTe but are easily extensible to other rough opaque materials

  4. Automatic Control System for the High Pressure CdTe Crystal Growth Furnace

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    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.

  5. Investigation of MBE grown polycrystalline CdTe films on the Medipix readout chip

    Science.gov (United States)

    Schütt, S.; Vogt, A.; Frei, K.; Fischer, F.; Fiederle, M.

    2017-06-01

    Cadmium Telluride (CdTe) films are directly deposited on a CMOS (complementary metal-oxide-semiconductor) based readout chip as sensor layer for X-ray detection. This is performed by using a modified Molecular Beam Epitaxy (MBE) setup with a carbon collimator enabling growth rates up to 10 μm/h. To obtain a good contacting behaviour of the 25-50 μm thick CdTe films, Te and Sb2Te3 are additionally evaporated during the process. The investigation of polycrystalline sensor layers deposited at 400 °C with SEM (scanning electron microscopy) and XRD (X-ray diffraction) reveals a columnar growth of the individual grains oriented predominantly in (111). By PES (photoelectron spectroscopy) measurements the chemical composition of the different layers is identified in a depth profile and changes in work function along the contact structure are observed. Detector properties reveal a linear behaviour of the count rate with increasing radiation intensity as well as sensibility to holes and electrons. Spatial resolution measurements result in a resolution of 5 lp/mm, which is a mandatory requirement for medical applications.

  6. Improving surface smoothness and photoluminescence of CdTe(1 1 1)A on Si(1 1 1) substrates grown by molecular beam epitaxy using Mn atoms

    International Nuclear Information System (INIS)

    Wang, Jyh-Shyang; Tsai, Yu-Hsuan; Chen, Chang-Wei; Dai, Zi-Yuan; Tong, Shih-Chang; Yang, Chu-Shou; Wu, Chih-Hung; Yuan, Chi-Tsu; Shen, Ji-Lin

    2014-01-01

    Highlights: • CdTe(1 1 1)A epilayers were grown on Si(1 1 1) substrates by molecular beam epitaxy. • We report an enhanced growth using Mn atoms. • The significant improvements in surface quality and optical properties were found. - Abstract: This work demonstrates an improvement of the molecular beam epitaxial growth of CdTe(1 1 1)A epilayer on Si(1 1 1) substrates using Mn atoms. The reflection high-energy electron diffraction patterns show that the involvement of some Mn atoms in the growth of CdTe(1 1 1)A is even more effective than the use of a buffer layer with a smooth surface for forming good CdTe(1 1 1)A epilayers. 10 K Photoluminescence spectra show that the incorporation of only 2% Mn significantly reduced the intensity of defect-related emissions and considerably increased the integral intensity of exciton-related emissions by a large factor of about 400

  7. Preparation and photoluminescence characterization of high-purity CdTe single crystals: purification effect of normal freezing on tellurium and cadmium telluride

    Science.gov (United States)

    Song, S. H.; Wang, J.; Isshiki, M.

    2002-03-01

    Extremely high-purity CdTe single crystals have been obtained by the traditional vertical Bridgman technique, beginning with the refining of tellurium material by the normal freezing method. The purification effect of normal freezing on tellurium has been confirmed to be very effective. This effect was also used to prepare extremely high-purity CdTe single crystals. The crystals were characterized by low temperature high-resolution photoluminescence (PL) spectroscopy. Only a sharp peak at 1.5896 eV was detected in the PL spectrum. The full-width at half-maximum is prepared by the Bridgman method.

  8. Thermal behaviour of strontium tartrate single crystals grown in gel

    Indian Academy of Sciences (India)

    Thermal behaviour of strontium tartrate crystals grown with the aid of sodium metasilicate gel is investigated using thermogravimetry (TG) and differential thermal analysis (DTA). Effect of magnetic field and dopant (Pb)2+ on the crystal stability is also studied using thermal analysis. This study reveals that water molecules are ...

  9. Role of Precursor-Conversion Chemistry in the Crystal-Phase Control of Catalytically Grown Colloidal Semiconductor Quantum Wires.

    Science.gov (United States)

    Wang, Fudong; Buhro, William E

    2017-12-26

    Crystal-phase control is one of the most challenging problems in nanowire growth. We demonstrate that, in the solution-phase catalyzed growth of colloidal cadmium telluride (CdTe) quantum wires (QWs), the crystal phase can be controlled by manipulating the reaction chemistry of the Cd precursors and tri-n-octylphosphine telluride (TOPTe) to favor the production of either a CdTe solute or Te, which consequently determines the composition and (liquid or solid) state of the Bi x Cd y Te z catalyst nanoparticles. Growth of single-phase (e.g., wurtzite) QWs is achieved only from solid catalysts (y ≪ z) that enable the solution-solid-solid growth of the QWs, whereas the liquid catalysts (y ≈ z) fulfill the solution-liquid-solid growth of the polytypic QWs. Factors that affect the precursor-conversion chemistry are systematically accounted for, which are correlated with a kinetic study of the composition and state of the catalyst nanoparticles to understand the mechanism. This work reveals the role of the precursor-reaction chemistry in the crystal-phase control of catalytically grown colloidal QWs, opening the possibility of growing phase-pure QWs of other compositions.

  10. Single Crystals Grown Under Unconstrained Conditions

    Science.gov (United States)

    Sunagawa, Ichiro

    Based on detailed investigations on morphology (evolution and variation in external forms), surface microtopography of crystal faces (spirals and etch figures), internal morphology (growth sectors, growth banding and associated impurity partitioning) and perfection (dislocations and other lattice defects) in single crystals, we can deduce how and by what mechanism the crystal grew and experienced fluctuation in growth parameters through its growth and post-growth history under unconstrained condition. The information is useful not only in finding appropriate way to growing highly perfect and homogeneous single crystals, but also in deciphering letters sent from the depth of the Earth and the Space. It is also useful in discriminating synthetic from natural gemstones. In this chapter, available methods to obtain molecular information are briefly summarized, and actual examples to demonstrate the importance of this type of investigations are selected from both natural minerals (diamond, quartz, hematite, corundum, beryl, phlogopite) and synthetic crystals (SiC, diamond, corundum, beryl).

  11. 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.)

  12. 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)

  13. Electrical conductivity measurements on gel grown KDP crystals ...

    Indian Academy of Sciences (India)

    Unknown

    †Scott Christian College, Nagercoil 629 003, India. MS received 4 September 2000; revised 16 July 2001. Abstract. Pure and impurity added (with urea and thiourea) KDP single crystals were grown by the gel method using silica gels. Electrical conductivity measurements were carried out along both the unique axis and.

  14. Electrical conductivity measurements on gel grown KDP crystals ...

    Indian Academy of Sciences (India)

    2CO3 and (NH4)2SO4] KDP sin- gle crystals were grown by the gel method using silica gels. Electrical conductivity measurements were carried out along both the unique axis and perpendicular directions at various temperatures ranging from 28 ...

  15. Electrical conductivity measurements on gel grown KDP crystals ...

    Indian Academy of Sciences (India)

    Pure and impurity added (with urea and thiourea) KDP single crystals were grown by the gel method using silica gels. Electrical conductivity measurements were carried out along both the unique axis and perpendicular directions at various temperatures ranging from 30 to 140°C by the conventional two-probe method.

  16. 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.

  17. Lattice variation and thermal parameters of gel grown KDP crystals ...

    Indian Academy of Sciences (India)

    Pure and impurity added (with NH4Cl, NH4NO3, NH4H2PO4, and (NH4)2SO4) KDP single crystals were grown by the gel method using silica gels. X-ray diffraction data were collected for powder samples and used for the estimation of lattice variation and thermal parameters like Debye–Waller factor, mean-square ...

  18. Spectral response of THM grown CdZnTe crystals

    DEFF Research Database (Denmark)

    Chen, H.; Awadalla, S.A.; Harris, F.

    2008-01-01

    The spectral response of several crystals grown by the Traveling Heater Method (THM) were investigated. An energy resolution of 0.98% for a Pseudo Frisch-Grid of 4 × 4 × 9 mm3 and 2.1% FWHM for a coplanar-grid of size 11 × 11 × 5 mm3 were measured using 137Cs-662 keV. In addition a 4% FWHM at 122...

  19. Relaxor properties of barium titanate crystals grown by Remeika method

    Science.gov (United States)

    Roth, Michel; Tiagunov, Jenia; Dul'kin, Evgeniy; Mojaev, Evgeny

    2017-06-01

    Barium titanate (BaTiO3, BT) crystals have been grown by the Remeika method using both the regular KF and mixed KF-NaF (0.6-0.4) solvents. Typical acute angle "butterfly wing" BT crystals have been obtained, and they were characterized using x-ray diffraction, scanning electron microscopy (including energy dispersive spectroscopy), conventional dielectric and acoustic emission methods. A typical wing has a triangular plate shape which is up to 0.5 mm thick with a 10-15 mm2 area. The plate has a (001) habit and an atomically smooth outer surface. Both K+ and F- solvent ions are incorporated as dopants into the crystal lattice during growth substituting for Ba2+ and O2- ions respectively. The dopants' distribution is found to be inhomogeneous, their content being almost an order of magnitude higher (up to 2 mol%) at out surface of the plate relatively to the bulk. A few μm thick surface layer is formed where a multidomain ferroelectric net is confined between two≤1 μm thick dopant-rich surfaces. The layer as a whole possess relaxor ferroelectric properties, which is apparent from the appearance of additional broad maxima, Tm, in the temperature dependence of the dielectric permittivity around the ferroelectric phase transition. Intense acoustic emission responses detected at temperatures corresponding to the Tm values allow to observe the Tm shift to lower temperatures at higher frequencies, or dispersion, typical for relaxor ferroelectrics. The outer surface of the BT wing can thus serve as a relaxor thin film for various electronic application, such as capacitors, or as a substrate for BT-based multiferroic structure. Crystals grown from KF-NaF fluxes contain sodium atoms as an additional impurity, but the crystal yield is much smaller, and while the ferroelectric transition peak is diffuse it does not show any sign of dispersion typical for relaxor behavior.

  20. 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

  1. 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.

  2. Single crystal diamond detectors grown by chemical vapor deposition

    International Nuclear Information System (INIS)

    Tuve, C.; Angelone, M.; Bellini, V.; Balducci, A.; Donato, M.G.; Faggio, G.; Marinelli, M.; Messina, G.; Milani, E.; Morgada, M.E.; Pillon, M.; Potenza, R.; Pucella, G.; Russo, G.; Santangelo, S.; Scoccia, M.; Sutera, C.; Tucciarone, A.; Verona-Rinati, G.

    2007-01-01

    The detection properties of heteropitaxial (polycrystalline, pCVD) and homoepitaxial (single crystal, scCVD) diamond films grown by microwave chemical vapor deposition (CVD) in the Laboratories of Roma 'Tor Vergata' University are reported. The pCVD diamond detectors were tested with α-particles from different sources and 12 C ions produced by 15MV Tandem accelerator at Southern National Laboratories (LNS) in Catania (Italy). pCVDs were also used to monitor 14MeV neutrons produced by the D-T plasma at Joint European Torus (JET), Culham, U.K. The limit of pCVDs is the poor energy resolution. To overcome this problem, we developed scCVD diamonds using the same reactor parameters that optimized pCVD diamonds. scCVD were grown on a low cost (100) HPHT single crystal substrate. A detector 110μm thick was tested under α-particles and under 14MeV neutron irradiation. The charge collection efficiency spectrum measured under irradiation with a triple α-particle source shows three clearly resolved peaks, with an energy resolution of about 1.1%. The measured spectra under neutron irradiation show a well separated C(n,α 0 ) 9 Be12 reaction peak with an energy spread of 0.5MeV for 14.8MeV neutrons and 0.3MeV for 14.1MeV neutrons, which are fully compatible with the energy spread of the incident neutron beams

  3. Highly Luminescent Solution-Grown Thiophene-Phenylene Co-Oligomer Single Crystals

    NARCIS (Netherlands)

    Kudryashova, Lyudmila G.; Kazantsev, Maxim S.; Postnikov, Valery A.; Bruevich, Vladimir V.; Luponosov, Yuriy N.; Surin, Nikolay M.; Borshchev, Oleg V.; Ponomarenko, Sergei A.; Pshenichnikov, Maxim S.; Paraschuk, Dmitry Yu.

    2016-01-01

    Thiophene-phenylene co-oligomers (TPCOs) are among the most promising materials for organic light emitting devices. Here we report on record high among TPCO single crystals photoluminescence quantum yield reaching 60%. The solution-grown crystals are stronger luminescent than the vapor-grown ones,

  4. Surface studies on as-grown (111) faces of sodium bromate crystals

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Single crystals of sodium bromate are grown at various supersaturations ranging from 3% to 8%. Surface studies have been carried out on as-grown and etched (111) faces of these crystals. Typical and syste- matically oriented growth hillocks are observed almost on all the faces. Further dislocation studies are ...

  5. The performance studies of DKDP crystals grown by a rapid horizontal growth method

    Science.gov (United States)

    Xie, Xiaoyi; Qi, Hongji; Wang, Bin; Wang, Hu; Chen, Duanyang; Shao, Jianda

    2018-04-01

    A deuterated potassium dihydrogen phosphate (DKDP) crystal with about 70% deuterium level was grown by a rapid horizontal growth method with independent design equipment, which includes a continuous filtration system. The cooling program during crystal growth was designed according to a self-developed software to catch the size of growing crystal in real time. The crystal structure, optical performance and laser induced damage threshold (LIDT) of this DKDP crystal were investigated in this paper. The deuterium concentration of the crystal was confirmed by the neutron diffraction technique, which was effective and available in determining a complete range of deuteration level. The dielectric property was measured to evaluate the perfection of the lattice. The transmittance and LIDT were carried out further to evaluate the optical and functional properties of this DKDP crystal grown in the rapid horizontal growth technique. All of the detailed characterization for DKDP figured out that the 70% deuterated KDP crystal grown in this way had relatively good qualities.

  6. Diodes based on semi-insulating CdTe crystals with Mo/MoO{sub x} contacts for X- and γ-ray detectors

    Energy Technology Data Exchange (ETDEWEB)

    Maslyanchuk, O.; Kulchynsky, V.; Solovan, M. [Chernivtsi National University, Chernivtsi (Ukraine); Gnatyuk, V. [Institute of Semiconductor Physics, NAS of Ukraine, Kyiv (Ukraine); Potiriadis, C. [Greek Atomic Energy Commission, Attiki (Greece); Kaissas, I. [Greek Atomic Energy Commission, Attiki (Greece); Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki (Greece); Brus, V. [Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, Berlin (Germany)

    2017-03-15

    This paper reports on the possible applications of molybdenum oxide (Mo/MoO{sub x}) contacts in combination with semi-insulating CdTe crystals. The electrical contacts to p-type Cl-doped CdTe crystals were formed by the deposition of molybdenum oxide and pure molybdenum thin films by the DC reactive magnetron sputtering. Electrical properties of the prepared Mo-MoO{sub x}/p-CdTe/MoO{sub x}-Mo surface-barrier structures were investigated at different temperatures. It is shown that the rapid growth of the reverse current with increasing bias voltage higher than 10 V is caused by the space-charge limited currents. Spectrometric properties of the Mo-MoO{sub x}/p-CdTe/MoO{sub x}-Mo structures have been also analyzed. It is revealed that the developed heterojunction has shown promising characteristics for its practical application in X- and γ-ray radiation detector fabrication. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. FTIR Spectroscopic Study of Mn(II) Oxidizing Pseudomonas putida GB1 Biofilms on ZnSe, Ge, and CdTe Crystal Surfaces

    Science.gov (United States)

    Parikh, S. J.; Gilbert, H. L.; Conklin, M. H.; Chorover, J.

    2003-12-01

    Pseudomonas putida strain GB1 is an aerobic, gram-negative bacterium capable of gaining energy from the biological oxidation of Mn(II). The increased kinetics of Mn(II) oxidation resulting from this microbial catalysis is known to contribute to the formation of Mn(IV) oxides in natural waters. Environmental conditions, including aqueous and surface chemistry, greatly affect the macromolecular composition and surface adhesion behavior of bacteria. For example, the chemistry of GB1 biofilms forming on crystal surfaces is expected to vary with Mn(II) concentration in solution. We used Fourier transform infrared (FTIR) spectroscopy to probe the formation of GB1 biofilms on the surfaces of negatively-charged IR transparent ZnSe, Ge, and CdTe crystal windows. Bacterial adhesion experiments were carried out both in the presence and absence of Mn(II)(aq) with FTIR windows suspended in a bioreactor comprising GB1 cells in a mineral growth medium at pH 7.6 and 30° C. After 85 h, windows were removed from the reactor and IR spectra were collected. Oxidation of Mn(II) was confirmed via leucoberbelin blue (LBB) indicator and the appearance of Mn-O stretches in biofilm IR spectra. Transmission FTIR spectra do not reveal detectable effects of crystal type on biofilm composition, but do indicate changes in chemistry resulting from introduction of Mn(II). In the presence of Mn(II), spectra of biofilms show higher relative intensity in the carbohydrate region (specifically 1160, 1052 cm-1). A down frequency shift in the P=O absorbance was also observed (1240 to 1222 cm-1). These results indicate a modification of bacterial cell/biofilm composition resulting during biological oxidation of Mn(II). The CdTe transmission window permits measurements to low wavenumbers (treatment. Transmission electron microscopy (TEM) of the bioreactor suspension revealed needle-like clusters of Mn oxide crystals in association with GB1 biomass and extracellular materials.

  8. Shape Evolution of Detached Bridgman Crystals Grown in Microgravity

    Science.gov (United States)

    Volz, M. P.; Mazuruk, K.

    2015-01-01

    A theory describing the shape evolution of detached Bridgman crystals in microgravity has been developed. A starting crystal of initial radius r0 will evolve to one of the following states: Stable detached gap; Attachment to the crucible wall; Meniscus collapse. Only crystals where alpha plus omega is great than 180 degrees will achieve stable detached growth in microgravity. Results of the crystal shape evolution theory are consistent with predictions of the dynamic stability of crystallization (Tatarchenko, Shaped Crystal Growth, Kluwer, 1993). Tests of transient crystal evolution are planned for ICESAGE, a series of Ge and GeSi crystal growth experiments planned to be conducted on the International Space Station (ISS).

  9. Electrically active light-element complexes in silicon crystals grown by cast method

    Science.gov (United States)

    Sato, Kuniyuki; Ogura, Atsushi; Ono, Haruhiko

    2016-09-01

    Electrically active light-element complexes called thermal donors and shallow thermal donors in silicon crystals grown by the cast method were studied by low-temperature far-infrared absorption spectroscopy. The relationship between these complexes and either crystal defects or light-element impurities was investigated by comparing different types of silicon crystals, that is, conventional cast-grown multicrystalline Si, seed-cast monolike-Si, and Czochralski-grown Si. The dependence of thermal and the shallow thermal donors on the light-element impurity concentration and their annealing behaviors were examined to compare the crystals. It was found that crystal defects such as dislocations and grain boundaries did not affect the formation of thermal or shallow thermal donors. The formation of these complexes was dominantly affected by the concentration of light-element impurities, O and C, independent of the existence of crystal defects.

  10. Anisotropy of electrical resistivity in PVT grown WSe2-x crystals

    Science.gov (United States)

    Solanki, G. K.; Patel, Y. A.; Agarwal, M. K.

    2017-12-01

    Single crystals of p-type WSe2 and WSe1.9 were grown by a physical vapour transport technique. The anisotropy in d.c. electrical resistivity was investigated in these grown crystals. The off-stoichiometric WSe1.9 exhibited a higher anisotropy ratio as compared to WSe2 crystals. The electron microscopic examination revealed the presence of a large number of stacking faults in these crystals. The resistivity enhancement along the c-axis and anisotropic effective mass ratio explained on the basis of structural disorder introduced due to off-stoichiometry.

  11. Synthesis and characterization of gel-grown cobalt tartrate crystals

    Indian Academy of Sciences (India)

    Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) are done to find the thermal properties of the crystal which manifest the water of hydration in the crystal. The variation of dielectric constant with respect to the applied frequency shows the polarization property of the crystal. The AC conductivity is ...

  12. Properties of GaN-based nanopillar-shaped crystals grown on a multicrystalline Si substrate

    Science.gov (United States)

    Fujiwara, Atomu; Sato, Yuichi

    2018-01-01

    The growth of gallium nitride-based nanopillar-shaped crystals on the multicrystalline silicon substrate that is widely employed in solar cells is presented here for the first time. The nanopillar-shaped crystals are successfully grown on the multicrystalline substrate in a manner similar to the structures grown on other substrates. Structural variations and a highly enhanced band edge emission in the photoluminescence spectrum have been observed using germanium doping.

  13. 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.

  14. On the morphology of SrCO 3 crystals grown at the interface ...

    Indian Academy of Sciences (India)

    When fatty acid was used as an additive at the interface, the crystals grown were self-assembled needle shaped strontianite crystallites branching out from the seed crystal via secondary nucleation. Under identical conditions of supersaturation, the presence of fatty amine molecules at the liquid–liquid interface resulted in ...

  15. Growth and study of some gel grown group II single crystals of iodate

    Indian Academy of Sciences (India)

    Unknown

    Page 1 ... Abstract. Single crystals of calcium iodate and barium iodate were grown by simple gel technique by single diffusion method. The optimum conditions were established by varying various parameters such as pH of gel solution, gel concentration, gel setting time, concentration of the reactants etc. Crystals having ...

  16. Study of gel grown mixed crystals of Bax Ca ((IO3) 4

    Indian Academy of Sciences (India)

    The growth of mixed crystals of BaCa1–(IO3)4 were carried out with simple gel method. The effect of various parameters such as pH of gel solution, gel concentration, gel setting time, concentration of reactants on the growth was studied. Crystals having different morphologies and habits were obtained. The grown ...

  17. Fabrication of radiation detectors with HgI2 crystals grown from a solution

    International Nuclear Information System (INIS)

    Friant, Alain; Mellet, Jean; Saliou, Charles; Mohammed Brahim, Tayeb.

    1979-01-01

    Mercuric Iodide crystals grown from a solution of molecular complexes with dimethylsulfoxide have been evaluated as γ-ray and X-ray room temperature detectors. Compared with materials grown from the vapor phase these crystals are characterized by a larger size, a lower level of native defects, but a higher impurity level. Detector technology, X-ray and γ-ray (up to 662 keV) detection properties and characterization measurements (T.S.C., photoconductivity, photovoltaic effect) are described. The effect of light on crystal properties is briefly discussed [fr

  18. Characterization of potassium bromide crystals grown in the aqueous solution of picric acid

    Energy Technology Data Exchange (ETDEWEB)

    Maheswari, J. Uma, E-mail: umak.anand@gmail.com [Department of Physics, The M.D.T.Hindu College, Tirunelveli 627010, Tamilnadu (India); Krishnan, C. [Department of Physics, Arignar Anna College, Aralvoymoli 629301, Tamilnadu (India); Kalyanaraman, S. [Physics Research Centre, Sri Paramakalyani College, Alwarkurichi 627412, Tamilnadu (India); Selvarajan, P. [Department of Physics, Aditanar College of Arts and Science, Tiruchendur 628216, Tamilnadu (India)

    2016-12-01

    Potassium bromide crystals were grown in the aqueous solution of picric acid by slow evaporation technique at room temperature. X-ray Diffraction (XRD) analysis ensures that the grown sample is in Fm3m space group and FCC structure. Energy Dispersive X-ray Spectroscopy (EDX) reveals the presence of elements in the title compound. UV–Vis-NIR spectrum reveals that the grown sample is a promising nonlinear optical (NLO) material. FTIR analysis confirms the functional groups present in the sample. The thermogravimetric (TG) and differential thermogravimetric (DTA) analyses ensure that the sample material is thermally stable up to 160 °C. The second harmonic efficiency of the sample is 1.3 times greater than that of standard KDP. The mechanical strength of the grown sample is estimated by Vickers microhardness tester. The electrical properties were investigated by impedance analysis and the results of various studies of the grown crystals are discussed.

  19. Dramatic improvement of crystal quality for low-­temperature-grown rabbit muscle aldolase

    OpenAIRE

    Park, HaJeung; Rangarajan, Erumbi S.; Sygusch, Jurgen; Izard, Tina

    2010-01-01

    Rabbit muscle aldolase (RMA) was crystallized in complex with the low-complexity domain (LC4) of sorting nexin 9. Monoclinic crystals were obtained at room temperature that displayed large mosaicity and poor X-ray diffraction. However, orthorhombic RMA–LC4 crystals grown at 277 K under similar conditions exhibited low mosaicity, allowing data collection to 2.2 Å Bragg spacing and structure determination.

  20. 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

  1. Dewetted growth and characterisation of high-resistivity CdTe

    Science.gov (United States)

    Fiederle, M.; Duffar, T.; Garandet, J. P.; Babentsov, V.; Fauler, A.; Benz, K. W.; Dusserre, P.; Corregidor, V.; Dieguez, E.; Delaye, P.; Roosen, G.; Chevrier, V.; Launay, J. C.

    2004-07-01

    Undoped and Ge-doped CdTe crystals have been grown using the dewetting phenomenon on the earth. A gap effected by the dewetting between the crystal and ampoule was created with a thickness up to 60 μm, but it was not stable for the complete growth process. The dewetting was stable for the first 25 mm of the growth, but than it got unstable. The main deteriorating factor was a change of a liquid-solid interface shape from the convex to concave. Structural, electrical, photoelectrical and optical characteristics of the studied samples showed better material quality in dewetted areas.

  2. Sources of optical distortion in rapidly grown crystals of KH2PO4

    International Nuclear Information System (INIS)

    De Yoreo, J.J.; Zaitseva, N.P.; Woods, B.W.; Land, T.A.; Rek, Z.U.

    1995-01-01

    We report results of x-ray topographic and optical measurements on KH 2 PO 4 crystals grown at rates of 5 to 30mm/day. We show that optical distortion in these crystals is caused primarily by 3 sources: dislocations, differences in composition between adjacent growth sectors of the crystal, and differences in composition between adjacent sectors of vicinal growth hillocks within a single growth sector of the crystal. We find that the compositional heterogeneities cause spatial variations in the refractive index and induced distortion of the transmitted wave front while large groups of dislocations are responsible for strain induced birefringence which leads to beam depolarization

  3. Synthesis and characterization of gel-grown cobalt tartrate crystals

    Indian Academy of Sciences (India)

    3Department of Physics, Mongolian University of Science and Technology, Ulaanbaatar, Mongolia. ∗. Corresponding .... The indexed XRD data for cobalt tartrate crystals are shown in table 2. The indexing was .... Manimaran, Head, Marketing, Pricol Castings Ltd, Coimbatore for the support during the course of this work.

  4. Synthesis and characterization of gel-grown cobalt tartrate crystals

    Indian Academy of Sciences (India)

    rate, or for heating to acquire a constant mass loss with time. The TGA curve for cobalt tartrate crystals is shown in figure 5. There are four stages of decomposition starting from room temperature of 40. ◦. C. The first stage of decompo- sition starts from 40. ◦. C and continues up to 200. ◦. C where the weight loss is about 25%.

  5. Thermal behaviour of strontium tartrate single crystals grown in gel

    Indian Academy of Sciences (India)

    Unknown

    lengths of the diffusing ions increase which slow down the vertical displacement of the ions due to the increased resistance of the extra path which the ions have to travel. In effect this is equivalent to reducing the diffusion coeffi- cient of the medium. The observed delay in the time of formation of the crystal in magnetic field is ...

  6. Electrical conductivity measurements on gel grown KDP crystals ...

    Indian Academy of Sciences (India)

    Impurity added KDP crystals; gel method; electrical conductivity; activation energy. 1. Introduction. Potassium dihydrogen ... phate [(NH4)2SO4] along with double distilled water and ethyl alcohol were used. KDP was added with .... in the vicinity of electrodes or chemical changes in layers close to electrodes (Bunget and ...

  7. A novel structure of gel grown strontium cyanurate crystal and its structural, optical, electrical characterization

    Science.gov (United States)

    Divya, R.; Nair, Lekshmi P.; Bijini, B. R.; Nair, C. M. K.; Gopakumar, N.; Babu, K. Rajendra

    2017-12-01

    Strontium cyanurate crystals with novel structure and unique optical property like mechanoluminescence have been grown by conventional gel method. Transparent crystals were obtained. The single crystal X-ray diffraction analysis reveals the exquisite structure of the grown crystal. The crystal is centrosymmetric and has a three dimensional polymeric structure. The powder X ray diffraction analysis confirms its crystalline nature. The functional groups present in the crystal were identified by Fourier transform infrared spectroscopy. Elemental analysis confirmed the composition of the complex. A study of thermal properties was done by thermo gravimetric analysis and differential thermal analysis. The optical properties like band gap, refractive index and extinction coefficient were evaluated from the UV visible spectral analysis. The etching study was done to reveal the dislocations in the crystal which in turn explains mechanoluminescence emission. The mechanoluminescence property exhibited by the crystal makes it suitable for stress sensing applications. Besides being a centrosymmetric crystal, it also exhibits NLO behavior. Dielectric properties were studied and theoretical calculations of Fermi energy, valence electron plasma energy, penn gap and polarisability have been done.

  8. Dramatic improvement of crystal quality for low-temperature-grown rabbit muscle aldolase

    International Nuclear Information System (INIS)

    Park, HaJeung; Rangarajan, Erumbi S.; Sygusch, Jurgen; Izard, Tina

    2010-01-01

    Rabbit muscle aldolase (RMA) was crystallized in complex with the low-complexity domain (LC4) of sorting nexin 9. Monoclinic crystals were obtained at room temperature that displayed large mosaicity and poor X-ray diffraction. However, orthorhombic RMA–LC4 crystals grown at 277 K under similar conditions exhibited low mosaicity, allowing data collection to 2.2 Å Bragg spacing and structure determination. Rabbit muscle aldolase (RMA) was crystallized in complex with the low-complexity domain (LC4) of sorting nexin 9. Monoclinic crystals were obtained at room temperature that displayed large mosaicity and poor X-ray diffraction. However, orthorhombic RMA–LC4 crystals grown at 277 K under similar conditions exhibited low mosaicity, allowing data collection to 2.2 Å Bragg spacing and structure determination. It was concluded that the improvement of crystal quality as indicated by the higher resolution of the new RMA–LC4 complex crystals was a consequence of the introduction of new lattice contacts at lower temperature. The lattice contacts corresponded to an increased number of interactions between high-entropy side chains that mitigate the lattice strain incurred upon cryocooling and accompanying mosaic spread increases. The thermodynamically unfavorable immobilization of high-entropy side chains used in lattice formation was compensated by an entropic increase in the bulk-solvent content owing to the greater solvent content of the crystal lattice

  9. Glow curves and the emission of flux-grown BaFCl:Na crystals

    International Nuclear Information System (INIS)

    Somaiah, K.; Hari Babu, V.

    1984-01-01

    The thermoluminescence glow curves and the emission spectra of flux-grown BaFCl:Na crystals were recorded. An additional TL peak at 320 K, an optical absorption band at 570nm and an emission peak at 490 nm have been seen in X/γ-irradiated crystals. Bleaching, room-temperature annealing and high-temperature emission results led us to conclude that the sodium impurity is responsible for the additional glow peak optical absorption band and emission peak. (author)

  10. How grain boundaries affect the efficiency of poly-CdTe solar-cells: A fundamental atomic-scale study of grain boundary dislocation cores using CdTe bi-crystal thin films.

    Energy Technology Data Exchange (ETDEWEB)

    Klie, Robert [Univ. of Illinois, Chicago, IL (United States)

    2016-10-25

    It is now widely accepted that grain boundaries in poly-crystalline CdTe thin film devices have a detrimental effect on the minority carrier lifetimes, the open circuit voltage and therefore the overall solar-cell performance. The goal of this project was to develop a fundamental understanding of the role of grain boundaries in CdTe on the carrier life-time, open-circuit voltage, Voc, and the diffusion of impurities. To achieve this goal, i) CdTe bi-crystals were fabricated with various misorientation angels, ii) the atomic- and electronic structures of the grain boundaries were characterized using scanning transmission electron microscopy (STEM), and iii) first-principles density functional theory modeling was performed on the structures determined by STEM to predict the grain boundary potential. The transport properties and minority carrier lifetimes of the bi-crystal grain boundaries were measured using a variety of approaches, including TRPL, and provided feedback to the characterization and modeling effort about the effectiveness of the proposed models.

  11. EXAFS investigations on PbMoO4 single crystals grown under ...

    Indian Academy of Sciences (India)

    Abstract. Extended X-ray absorption fine structure (EXAFS) measurements on PbMoO4 (LMO) crystals have been performed at the recently-commissioned dispersive EXAFS beamline (BL-8) of INDUS-2 Synchrotron facility at Indore, India. The LMO samples were prepared under three different conditions viz. (i) grown from ...

  12. Optical characteristics of ZnO single crystal grown by the hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Chen, G. Z.; Yin, J. G., E-mail: gzhchen@siom.ac.cn, E-mail: yjg@siom.ac.cn; Zhang, L. H.; Zhang, P. X.; Wang, X. Y.; Liu, Y. C. [Chinese Academy of Sciences, Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics (China); Zhang, C. L. [Guilin Research Institute of Geology for Mineral Resources (China); Gu, S. L. [Nanjing University, Department of Physics (China); Hang, Y., E-mail: yhang@siom.ac.cn [Chinese Academy of Sciences, Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics (China)

    2015-12-15

    ZnO single crystals have been grown by the hydrothermal method. Raman scattering and Photoluminescence spectroscopy (PL) have been used to study samples of ZnO that were unannealed or annealed in different ambient gases. It is suggested that the green emission may originate from defects related to copper in our samples.

  13. Physical properties of lauric acid crystals grown with KBr in aqueous ...

    Indian Academy of Sciences (India)

    12

    The magnitude of nonlinear polarization increased by adding an electron donating group or an electron withdrawing group into the π – electron conjugated frame work [5] for sub-atomic outline. Recently, we have reported the NLO activity of lauric acid (LA) single crystal grown in ethanol solution [6].When NLO materials are ...

  14. Graphite crystals grown within electromagnetically levitated metallic droplets

    International Nuclear Information System (INIS)

    Amini, Shaahin; Kalaantari, Haamun; Mojgani, Sasan; Abbaschian, Reza

    2012-01-01

    Various graphite morphologies were observed to grow within the electromagnetically levitated nickel–carbon melts, including primary flakes and spheres, curved surface graphite and eutectic flakes, as well as engulfed and entrapped particles. As the supersaturated metallic solutions were cooled within the electromagnetic (EM) levitation coil, the primary graphite flakes and spheres formed and accumulated near the periphery of the droplet due to EM circulation. The primary graphite islands, moreover, nucleated and grew on the droplet surface which eventually formed a macroscopic curved graphite crystal covering the entire liquid. Upon further cooling, the liquid surrounding the primary graphite went under a coupled eutectic reaction while the liquid in the center formed a divorced eutectic due to EM mixing. This brought about the formation of graphite fine flakes and agglomerated particles close to the surface and in the center of the droplet, respectively. The graphite morphologies, growth mechanisms, defects, irregularities and growth instabilities were interpreted with detailed optical and scanning electron microscopies.

  15. 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

  16. Understanding arsenic incorporation in CdTe with atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Burton, G. L.; Diercks, D. R.; Ogedengbe, O. S.; Jayathilaka, P. A. R. D.; Edirisooriya, M.; Myers, T. H.; Zaunbrecher, K. N.; Moseley, J.; Barnes, T. M.; Gorman, B. P.

    2018-08-01

    Overcoming the open circuit voltage deficiency in Cadmium Telluride (CdTe) photovoltaics may be achieved by increasing p-type doping while maintaining or increasing minority carrier lifetimes. Here, routes to higher doping efficiency using arsenic are explored through an atomic scale understanding of dopant incorporation limits and activation in molecular beam epitaxy grown CdTe layers. Atom probe tomography reveals spatial segregation into nanometer scale clusters containing > 60 at% As for samples with arsenic incorporation levels greater than 7-8 x 10^17 cm-3. The presence of arsenic clusters was accompanied by crystal quality degradation, particularly the introduction of arsenic-enriched extended defects. Post-growth annealing treatments are shown to increase the size of the As precipitates and the amount of As within the precipitates.

  17. Long-term studies on tetragonal lysozyme crystals grown in quiescent and forced convection environments

    Science.gov (United States)

    Grant, M. L.; Saville, D. A.

    The growth of tetragonal hen lysozyme crystals in the size range 150-300 μm was studied using digital microscopy; the size and orientation of the growing crystals were estimated from the geometry of the ideal tetragonal lysozyme crystal. At a confidence level above 99%, statistical analyses indicate the (110) face growth rates of crystals grown in quiescent conditions are not inhibited by weak buoyancy-driven natural convection. Yet similar analyses of crystals subjected to a weak forced flow of the same magnitude indicate a statistically significant decrease in growth rate with time. This apparent paradox probably results from mass transport limitations within the crystal growth cell. Mathematical models of fluid mixing inside the growth chamber suggest that crystal growth is limited by the rate at which protein molecules are transported to crystals growing on the walls of the chamber. Our experiments also reveal a large variation in the growth rates of crystals within a nominally homogeneous population. The local environment of the crystal may account for some of the variation, but the mechanisms are not understood.

  18. Photoluminescence characteristics of Pb-doped, molecular-beam-epitaxy grown ZnSe crystal layers

    International Nuclear Information System (INIS)

    Mita, Yoh; Kuronuma, Ryoichi; Inoue, Masanori; Sasaki, Shoichiro; Miyamoto, Yoshinobu

    2004-01-01

    The characteristic green photoluminescence emission and related phenomena in Pb-doped, molecular-beam-epitaxy (MBE)-grown ZnSe crystal layers were investigated to explore the nature of the center responsible for the green emission. The intensity of the green emission showed a distinct nonlinear dependence on excitation intensity. Pb-diffused polycrystalline ZnSe was similarly examined for comparison. The characteristic green emission has been observed only in MBE-grown ZnSe crystal layers with moderate Pb doping. The results of the investigations on the growth conditions, luminescence, and related properties of the ZnSe crystal layers suggest that the green emission is due to isolated Pb replacing Zn and surrounded with regular ZnSe lattice with a high perfection

  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. Optical Properties of LiNbO3 Single Crystal Grown by Czochralski Method

    Science.gov (United States)

    Sahar, M. R.; Naim, N. M.; Hamzah, K.

    2011-03-01

    Pure LiNbO3 single crystal was grown by Czochralski method using Automatic Diameter Control—Crystal Growth System (ADC-CGS). The transmission spectrum was determined by using Infrared Spectroscopy while the refractive index was determined using UV-Vis spectroscopy via the Sellmeier equation. The density was also measured using the Archimedes principle. It was found that the peak for the absorption vibrational spectrum for LiNbO3 crystal occurs at 801 cm-1, 672 cm-1, 639 cm-1 and 435 cm-1. The refractive index, ne was found to be 2.480 and the crystal density was around 4.64 g/cm3.

  1. 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...

  2. X-ray diffraction in laser-irradiated epsomite crystals grown in presence of borax

    International Nuclear Information System (INIS)

    Zaitseva, E.V.; Portnov, V.N.; Faddeev, M.A.; Chuprunov, E.V.

    1997-01-01

    Relative changes in the intensities ΔI/I of the (220) and (440) X-ray diffraction reflection during laser irradiation of epsomite (MgSO 2 ·7H 2 O) crystals grown from an aqueous solution in the presence of borax (Na 2 B 4 O 7 ·10H 2 O) were measured using the CoK α , CuK α , MoK α radiations. The intensities measured depend on the real crystal structure dependent on the borax content in the solution. The dependence of ΔI/I is studied as a function of borax in the solution and X-ray-radiation wavelength

  3. Defects in Czochralski-grown silicon crystals investigated by positron annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Ikari, Atsushi; Kawakami, Kazuto; Haga, Hiroyo [Nippon Steel Corp., Sagamihara, Kanagawa (Japan). Electronics Research Labs.; Uedono, Akira; Wei, Long; Kawano, Takao; Tanigawa, Shoichiro

    1994-10-01

    Positron lifetime and Doppler broadening experiments were performed on Czochralski-grown silicon crystals. A monoenergetic positron beam was also used to measure the diffusion length of positrons in the wafer. From the measurements, it was observed that the value of diffusion length of positrons decreased at the region where microdefects were formed during the crystal growth process. It was also found that the line shape parameter S decreased and the lifetime of positrons increased at the region. These results can be attributed to the annihilation of positrons trapped by vacancy oxygen complexes which are formed in association with the microdefects. (author).

  4. Diffuse neutron scattering from an in situ grown α-AgI single crystal

    International Nuclear Information System (INIS)

    Keen, D.A.; Nield, V.M.; McGreevy, R.L.

    1994-01-01

    A large single crystal of α-AgI was grown in situ from the melt on the SXD single-crystal neutron time-of-flight Laue diffractometer using a specially designed furnace. A wide range of reciprocal space was accessed with minimal rotation of the arbitrarily aligned sample. Weak rings of diffuse scattering were observed together with strong scattering around some Bragg peaks. The results are discussed with reference to earlier powder diffraction data and indicate significant correlations between the motion of the silver ions and the vibrations of the iodide ions. (orig.)

  5. Characterization of large cadmium zinc telluride crystals grown by traveling heater method

    DEFF Research Database (Denmark)

    Chen, H.; Awadalla, S.A.; Iniewski, K.

    2008-01-01

    The focus of this paper is to evaluate thick, 20 X 20 X 10 and 10 X 10 X 10 mm(3), cadmium zinc telluride (CZT), Cd0.9Zn0.1Te, crystals grown using the traveling heater method (THIM). The phenomenal spectral performance and small size and low concentration of Te inclusions/precipitates of these c......The focus of this paper is to evaluate thick, 20 X 20 X 10 and 10 X 10 X 10 mm(3), cadmium zinc telluride (CZT), Cd0.9Zn0.1Te, crystals grown using the traveling heater method (THIM). The phenomenal spectral performance and small size and low concentration of Te inclusions...

  6. The investigation of stress in freestanding GaN crystals grown from Si substrates by HVPE.

    Science.gov (United States)

    Lee, Moonsang; Mikulik, Dmitry; Yang, Mino; Park, Sungsoo

    2017-08-17

    We investigate the stress evolution of 400 µm-thick freestanding GaN crystals grown from Si substrates by hydride vapour phase epitaxy (HVPE) and the in situ removal of Si substrates. The stress generated in growing GaN can be tuned by varying the thickness of the MOCVD AlGaN/AlN buffer layers. Micro Raman analysis shows the presence of slight tensile stress in the freestanding GaN crystals and no stress accumulation in HVPE GaN layers during the growth. Additionally, it is demonstrated that the residual tensile stress in HVPE GaN is caused only by elastic stress arising from the crystal quality difference between Ga- and N-face GaN. TEM analysis revealed that the dislocations in freestanding GaN crystals have high inclination angles that are attributed to the stress relaxation of the crystals. We believe that the understanding and characterization on the structural properties of the freestanding GaN crystals will help us to use these crystals for high-performance opto-electronic devices.

  7. Growth, structural, optical, mechanical and quantum chemical analysis of unidirectional grown bis(guanidinium) 5-sulfosalicylate (BGSSA) single crystal

    Science.gov (United States)

    Sreedevi, R.; Saravana Kumar, G.; Amarsingh Bhabu, K.; Balu, T.; Murugakoothan, P.; Rajasekaran, T. R.

    2018-02-01

    Bis(guanidinium) 5-sulfosalicylate single crystal was grown by using Sankaranarayanan-Ramasamy (SR) method from the solution of methanol and water in equimolar ratio. Good quality crystal with 50 mm length and 10 mm in diameter was grown. The grown crystal was subjected to single crystal X-ray diffraction analysis to confirm the crystal structure and it was found to be orthorhombic. UV-Vis-NIR spectroscopic study revealed that the SR method grown crystal had good optical transparency with wide optical band gap of 4.4 eV. The presence of the functional groups and modes of vibrations were identified by FTIR spectroscopy recorded in the range 4000-400 cm-1. The mechanical strength of the grown crystal was confirmed using Vickers microhardness tester by applying load from 25 g to 100 g. Density functional theory (DFT) method with B3LYP/6-31-G (d,p) level basis set was employed and hence the optimized molecular geometry, first order hyperpolarizability, dipole moment, thermodynamic functions, molecular electrostatic potential and frontier molecular orbital analysis of the grown BGSSA sample was computed and analysed.

  8. Optical characterization of single-crystal diamond grown by DC arc plasma jet CVD

    Science.gov (United States)

    Hei, Li-fu; Zhao, Yun; Wei, Jun-jun; Liu, Jin-long; Li, Cheng-ming; Lü, Fan-xiu

    2017-12-01

    Optical centers of single-crystal diamond grown by DC arc plasma jet chemical vapor deposition (CVD) were examined using a low-temperature photoluminescence (PL) technique. The results show that most of the nitrogen-vacancy (NV) complexes are present as NV- centers, although some H2 and H3 centers and B-aggregates are also present in the single-crystal diamond because of nitrogen aggregation resulting from high N2 incorporation and the high mobility of vacancies under growth temperatures of 950-1000°C. Furthermore, emissions of radiation-induced defects were also detected at 389, 467.5, 550, and 588.6 nm in the PL spectra. The reason for the formation of these radiation-induced defects is not clear. Although a Ni-based alloy was used during the diamond growth, Ni-related emissions were not detected in the PL spectra. In addition, the silicon-vacancy (Si-V)-related emission line at 737 nm, which has been observed in the spectra of many previously reported microwave plasma chemical vapor deposition (MPCVD) synthetic diamonds, was absent in the PL spectra of the single-crystal diamond prepared in this work. The high density of NV- centers, along with the absence of Ni-related defects and Si-V centers, makes the single-crystal diamond grown by DC arc plasma jet CVD a promising material for applications in quantum computing.

  9. Vickers microhardness studies on solution-grown single crystals of potassium boro-succinate

    Science.gov (United States)

    Lakshmipriya, M.; Rajan Babu, D.; Ezhil Vizhi, R.

    2015-02-01

    The semiorganic crystals of potassium boro-succinate (KBS) were grown by slow evaporation method. KBS crystallizes in monoclinic system which was confirmed by powder XRD analysis. Vickers microhardness study has been carried out over a load range of 25-100 g. The Vickers hardness numbers (Hv) of the material increases as the load increases so the material is suitable for device fabrication. The Meyer index 'n' is estimated to be greater than 1.6, the crystal system belongs to the soft material category. The elastic stiffness coefficient, c11, has also been calculated using Wooster's empirical relation from the hardness data. The fracture toughness values 'Kc', determined from measurements of crack lengths, were estimated to be 0.15166 MN/m3/2. The brittleness indices 'Bi' were estimated as 276 m-1/2.

  10. Dramatic improvement of crystal quality for low-­temperature-grown rabbit muscle aldolase

    Science.gov (United States)

    Park, HaJeung; Rangarajan, Erumbi S.; Sygusch, Jurgen; Izard, Tina

    2010-01-01

    Rabbit muscle aldolase (RMA) was crystallized in complex with the low-complexity domain (LC4) of sorting nexin 9. Monoclinic crystals were obtained at room temperature that displayed large mosaicity and poor X-ray diffraction. However, orthorhombic RMA–LC4 crystals grown at 277 K under similar conditions exhibited low mosaicity, allowing data collection to 2.2 Å Bragg spacing and structure determination. It was concluded that the improvement of crystal quality as indicated by the higher resolution of the new RMA–LC4 complex crystals was a consequence of the introduction of new lattice contacts at lower temperature. The lattice contacts corresponded to an increased number of interactions between high-entropy side chains that mitigate the lattice strain incurred upon cryocooling and accompanying mosaic spread increases. The thermodynamically unfavorable immobilization of high-entropy side chains used in lattice formation was compensated by an entropic increase in the bulk-solvent content owing to the greater solvent content of the crystal lattice. PMID:20445268

  11. Dramatic Improvement of Crystal Quality for Low-temperature-grown Rabbit Muscle Aldolase

    Energy Technology Data Exchange (ETDEWEB)

    Park, H.; Rangarajan, E; Sygusch, J; Izard, T

    2010-01-01

    Rabbit muscle aldolase (RMA) was crystallized in complex with the low-complexity domain (LC4) of sorting nexin 9. Monoclinic crystals were obtained at room temperature that displayed large mosaicity and poor X-ray diffraction. However, orthorhombic RMA-LC4 crystals grown at 277 K under similar conditions exhibited low mosaicity, allowing data collection to 2.2 {angstrom} Bragg spacing and structure determination. It was concluded that the improvement of crystal quality as indicated by the higher resolution of the new RMA-LC4 complex crystals was a consequence of the introduction of new lattice contacts at lower temperature. The lattice contacts corresponded to an increased number of interactions between high-entropy side chains that mitigate the lattice strain incurred upon cryocooling and accompanying mosaic spread increases. The thermodynamically unfavorable immobilization of high-entropy side chains used in lattice formation was compensated by an entropic increase in the bulk-solvent content owing to the greater solvent content of the crystal lattice.

  12. Dramatic improvement of crystal quality for low-temperature-grown rabbit muscle aldolase.

    Science.gov (United States)

    Park, Hajeung; Rangarajan, Erumbi S; Sygusch, Jurgen; Izard, Tina

    2010-05-01

    Rabbit muscle aldolase (RMA) was crystallized in complex with the low-complexity domain (LC4) of sorting nexin 9. Monoclinic crystals were obtained at room temperature that displayed large mosaicity and poor X-ray diffraction. However, orthorhombic RMA-LC4 crystals grown at 277 K under similar conditions exhibited low mosaicity, allowing data collection to 2.2 A Bragg spacing and structure determination. It was concluded that the improvement of crystal quality as indicated by the higher resolution of the new RMA-LC4 complex crystals was a consequence of the introduction of new lattice contacts at lower temperature. The lattice contacts corresponded to an increased number of interactions between high-entropy side chains that mitigate the lattice strain incurred upon cryocooling and accompanying mosaic spread increases. The thermodynamically unfavorable immobilization of high-entropy side chains used in lattice formation was compensated by an entropic increase in the bulk-solvent content owing to the greater solvent content of the crystal lattice.

  13. Crystal growth, physical properties and computational insights of semi-organic non-linear optical crystal diphenylguanidinium perchlorate grown by conventional solvent evaporation method

    Science.gov (United States)

    Kajamuhideen, M. S.; Sethuraman, K.; Ramamurthi, K.; Ramasamy, P.

    2018-02-01

    A splendid nonlinear optical single crystals diphenylguanidinium perchlorate (DPGP) was lucratively grown by low cost solvent evaporation method with the dimensions of 8 × 4 × 2 mm3. Structural and morphological studies of grown crystal were confirmed using X-ray diffraction studies. The presence of diverse functional groups was identified using FTIR and RAMAN studies. The molecular structure of a grown crystal was inveterate by NMR studies. The optical transmittance of DPGP crystal was analyzed using UV-vis-NIR studies. Photoluminescence spectrum shows sharp, well defined emission peak at 388 nm. Thermal studies assign that adduct is stable with the melting point of 164 °C. Microhardness studies declare that DPGP crystal belongs to the soft material class and their yield strength and elastic stiffness constant values were evaluated. Photoconductivity studies revealed the negative photoconductive nature of DPGP crystal. Second harmonic generation (SHG) efficiency of the DPGP crystal was 1.4 times that of potassium dihydrogen phosphate. Etching studies were carried out for different etching time. The dielectric studies were performed at different frequency. Laser damage threshold properties of DPGP crystal were examined using Nd:YAG laser system. The HOMO-LUMO energy gap evident the charge transfer interaction of the molecule. The calculated first order hyperpolarizability value is 5 times greater than that of urea. Thus, the grown DPGP single crystals are well suited for NLO device fabrications.

  14. A quality comparison of protein crystals grown under containerless conditions generated by diamagnetic levitation, silicone oil and agarose gel.

    Science.gov (United States)

    Cao, Hui-Ling; Sun, Li-Hua; Li, Jian; Tang, Lin; Lu, Hui-Meng; Guo, Yun-Zhu; He, Jin; Liu, Yong-Ming; Xie, Xu-Zhuo; Shen, He-Fang; Zhang, Chen-Yan; Guo, Wei-Hong; Huang, Lin-Jun; Shang, Peng; He, Jian-Hua; Yin, Da-Chuan

    2013-10-01

    High-quality crystals are key to obtaining accurate three-dimensional structures of proteins using X-ray diffraction techniques. However, obtaining such protein crystals is often a challenge. Several containerless crystallization techniques have been reported to have the ability to improve crystal quality, but it is unknown which is the most favourable way to grow high-quality protein crystals. In this paper, a quality comparison of protein crystals which were grown under three containerless conditions provided by diamagnetic levitation, silicone oil and agarose gel was conducted. A control experiment on a vessel wall was also simultaneously carried out. Seven different proteins were crystallized under the four conditions, and the crystal quality was assessed in terms of the resolution limit, the mosaicity and the Rmerge. It was found that the crystals grown under the three containerless conditions demonstrated better morphology than those of the control. X-ray diffraction data indicated that the quality of the crystals grown under the three containerless conditions was better than that of the control. Of the three containerless crystallization techniques, the diamagnetic levitation technique exhibited the best performance in enhancing crystal quality. This paper is to our knowledge the first report of improvement of crystal quality using a diamagnetic levitation technique. Crystals obtained from agarose gel demonstrated the second best improvement in crystal quality. The study indicated that the diamagnetic levitation technique is indeed a favourable method for growing high-quality protein crystals, and its utilization is thus potentially useful in practical efforts to obtain well diffracting protein crystals.

  15. 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.

  16. Ferromagnetism in CVT grown tungsten diselenide single crystals with nickel doping

    Science.gov (United States)

    Habib, Muhammad; Muhammad, Zahir; Khan, Rashid; Wu, Chuanqiang; Rehman, Zia ur; Zhou, Yu; Liu, Hengjie; Song, Li

    2018-03-01

    Two dimensional (2D) single crystal layered transition materials have had extensive consideration owing to their interesting magnetic properties, originating from their lattices and strong spin-orbit coupling, which make them of vital importance for spintronic applications. Herein, we present synthesis of a highly crystalline tungsten diselenide layered single crystal grown by chemical vapor transport technique and doped with nickel (Ni) to tailor its magnetic properties. The pristine WSe2 single crystal and Ni-doped crystal were characterized and analyzed for magnetic properties using both experimental and computational aspects. It was found that the magnetic behavior of the 2D layered WSe2 crystal changed from diamagnetic to ferromagnetic after Ni-doping at all tested temperatures. Moreover, first principle density functional theory (DFT) calculations further confirmed the origin of room temperature ferromagnetism of Ni-doped WSe2, where the d-orbitals of the doped Ni atom promoted the spin moment and thus largely contributed to the magnetism change in the 2D layered material.

  17. Prismatic dislocation loops and concentric dislocation loops in HPHT-grown diamond single crystals

    International Nuclear Information System (INIS)

    Yin, L.-W.; Li, M.-S.; Zou, Z.-D.; Gong, Z.-G.; Hao, Z.-Y.

    2003-01-01

    As-grown diamond single crystals grown from Fe-Ni-C system under high temperature-high pressure were examined by transmission electron microscopy. There exist prismatic dislocation loops and concentric dislocation loops in the diamond, which are related to the nonequilibrium nature of the diamond synthesis process. The prismatic dislocation loops may be formed by vacancy condensation during rapid cooling from high temperature, and the Burgers vector of the dislocation is determined by diffraction contrast as 1/2 . Moire fringes formed by two overlapping (1 1 1) close-packed planes were used to study concentric dislocation loops. The concentric dislocation loops may be derived from thermal stress caused by the inclusions in the diamond, which cause a strain field due to the thermal contraction difference between the inclusions and the diamond during cooling from high temperature

  18. 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.

  19. Intrinsic and extrinsic point-defects in vapor transport grown ZnO bulk crystals

    International Nuclear Information System (INIS)

    Pfisterer, D.; Hofmann, D.M.; Sann, J.; Meyer, B.K.; Tena-Zaera, R.; Munoz-Sanjose, V.; Frank, Th.; Pensl, G.

    2006-01-01

    Vapor transport grown ZnO bulk crystals were characterized by electrical, optical and magnetic resonance spectroscopy. The experiments show that the residual carrier concentration is caused by residual H, Al, Ga, and oxygen vacancies in the material. Annealing the samples in O 2 at about 1000 o C (2 atm, 20 h) reduces the H and V O donor concentration by typical one order of magnitude. The photoluminescence and DLTS results suggest a correlation between the broad unstructured emission at 2.45 eV (green band) and a donor level 530 meV below the conduction band (E4)

  20. Intrinsic and extrinsic point-defects in vapor transport grown ZnO bulk crystals

    Energy Technology Data Exchange (ETDEWEB)

    Pfisterer, D. [I. Physikalisches Institut, Justus-Liebig-Universitaet Giessen, Heinrich-Buff-Ring 16, Giessen D-35392 (Germany); Hofmann, D.M. [I. Physikalisches Institut, Justus-Liebig-Universitaet Giessen, Heinrich-Buff-Ring 16, Giessen D-35392 (Germany)]. E-mail: detlev.m.hofmann@exp1.physik.uni-giessen.de; Sann, J. [I. Physikalisches Institut, Justus-Liebig-Universitaet Giessen, Heinrich-Buff-Ring 16, Giessen D-35392 (Germany); Meyer, B.K. [I. Physikalisches Institut, Justus-Liebig-Universitaet Giessen, Heinrich-Buff-Ring 16, Giessen D-35392 (Germany); Tena-Zaera, R. [Dept. Fisica Aplicada I Electromagnetisme, Universitat de Valencia, C/Dr. Moliner 50, Burjassot 46100 (Spain); Munoz-Sanjose, V. [Dept. Fisica Aplicada I Electromagnetisme, Universitat de Valencia, C/Dr. Moliner 50, Burjassot 46100 (Spain); Frank, Th. [Institut fuer angewandte Physik, Universitaet Erlangen-Nuernberg, Staudtstr. 7/Gebaeude A3, Erlangen D-91058 (Germany); Pensl, G. [Institut fuer angewandte Physik, Universitaet Erlangen-Nuernberg, Staudtstr. 7/Gebaeude A3, Erlangen D-91058 (Germany)

    2006-04-01

    Vapor transport grown ZnO bulk crystals were characterized by electrical, optical and magnetic resonance spectroscopy. The experiments show that the residual carrier concentration is caused by residual H, Al, Ga, and oxygen vacancies in the material. Annealing the samples in O{sub 2} at about 1000 {sup o}C (2 atm, 20 h) reduces the H and V{sub O} donor concentration by typical one order of magnitude. The photoluminescence and DLTS results suggest a correlation between the broad unstructured emission at 2.45 eV (green band) and a donor level 530 meV below the conduction band (E4)

  1. Characterization of ZnO crystals grown by the vertical Bridgman method

    Energy Technology Data Exchange (ETDEWEB)

    Eisermann, Sebastian; Laufer, Andreas; Graubner, Swen; Pinnisch, Melanie; Stehr, Jan; Lautenschlaeger, Stefan; Hofmann, Detlev M.; Meyer, Bruno K. [I. Physics Institute, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 16, 35392 Giessen (Germany); Klimm, Detlev; Schulz, Detlev [Leibniz-Institut fuer Kristallzuechtung, Max-Born-Str. 2, 12489 Berlin (Germany)

    2011-01-15

    ZnO crystals grown by the vertical Bridgman technique were comprehensively characterized in view of the impurities and intrinsic defects in the material. It is shown that residual Al is the cause of the residual n-type conductivity and intrinsic defects play only a minor role in the samples. Annealing the samples at 1100 C for 1 h in oxygen atmosphere improves the surface properties of the samples without having negative effects on their optical and electrical properties. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. p-type doping efficiency in CdTe: Influence of second phase formation

    Science.gov (United States)

    McCoy, Jedidiah J.; Swain, Santosh K.; Sieber, John R.; Diercks, David R.; Gorman, Brian P.; Lynn, Kelvin G.

    2018-04-01

    Cadmium telluride (CdTe) high purity, bulk, crystal ingots doped with phosphorus were grown by the vertical Bridgman melt growth technique to understand and improve dopant solubility and activation. Large net carrier densities have been reproducibly obtained from as-grown ingots, indicating successful incorporation of dopants into the lattice. However, net carrier density values are orders of magnitude lower than the solubility of P in CdTe as reported in literature, 1018/cm3 to 1019/cm3 [J. H. Greenberg, J. Cryst. Growth 161, 1-11 (1996) and R. B. Hall and H. H. Woodbury, J. Appl. Phys. 39(12), 5361-5365 (1968)], despite comparable starting charge dopant densities. Growth conditions, such as melt stoichiometry and post growth cooling, are shown to have significant impacts on dopant solubility. This study demonstrates that a significant portion of the dopant becomes incorporated into second phase defects as compounds of cadmium and phosphorous, such as cadmium phosphide, which inhibits dopant incorporation into the lattice and limits maximum attainable net carrier density in bulk crystals. Here, we present an extensive study on the characteristics of these second phase defects in relation to their composition and formation kinetics while providing a pathway to minimize their formation and enhance solubility.

  3. Growth of single crystals of Hg(Br xI1-x)2 and their detection capability

    International Nuclear Information System (INIS)

    Gospodinov, M.M.; Petrova, D.; Yanchev, I.Y.; Daviti, M.; Manolopoulou, M.; Paraskevopoulos, K.M.; Anagnostopoulos, A.N.; Polychroniadis, E.K.

    2005-01-01

    Hg(Br x I 1-x ) 2 crystals were grown by the Bridgman method for 0.2 241 Am and 55 Fe were used as radioactive sources. From the corresponding energy spectra, it is evident that crystals with x = 0.2 show enhanced resolution at low energies (below 200 keV), competing those fabricated from HgI 2 and CdTe. Crystals with higher x's were of lower resolution

  4. 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.

  5. Improvement of dopant distribution in radial direction of single crystals grown by micro-pulling-down method

    Science.gov (United States)

    Yokota, Yuui; Kudo, Tetsuo; Chani, Valery; Ohashi, Yuji; Kurosawa, Shunsuke; Kamada, Kei; Zeng, Zhong; Kawazoe, Yoshiyuki; Yoshikawa, Akira

    2017-09-01

    Two iridium crucibles with one and five capillaries at a nozzle were developed for the growth of Ce-doped Y3Al5O12 [Ce:YAG] single crystals by the micro-pulling-down [μ-PD] method. The purpose of the study was to examine the effect of the capillary number on the Ce distribution in the radial direction of the crystals. The crystals grown from 2 mol% and 5 mol% Ce-doped YAG melts were then cut perpendicular to the growth direction and polished to produce specimens suitable for the measurement of Ce distribution. The Ce:YAG crystals grown using the crucible with one capillary [Ce:YAG(1 C)] had greater Ce content in the central portion of the crystal when compared to its peripheral parts. On the other hand, in the case of the Ce:YAG crystal grown using the crucible with five capillaries [Ce:YAG(5 C)], the increased Ce concentration was detected in five specimen sections positioned just below the capillaries. The results indicated that increase of the number of capillaries is effective practice that results in an improvement of the radial homogeneity of the single crystals grown by the μ-PD method.

  6. Optical properties of Ni-doped MgGa2O4 single crystals grown by floating zone method

    International Nuclear Information System (INIS)

    Suzuki, Takenobu; Hughes, Mark; Ohishi, Yasutake

    2010-01-01

    The single crystal growth conditions and spectroscopic characterization of Ni-doped MgGa 2 O 4 with inverse-spinel structure crystal family are described. Single crystals of this material have been grown by floating zone method. Ni-doped MgGa 2 O 4 single crystals have broadband fluorescence in the 1100-1600 nm wavelength range, 1.6 ms room temperature lifetime, 56% quantum efficiency and 1.05x10 -21 cm 2 stimulated emission cross section at the emission peak. This new material is very promising for tunable laser applications covering the important optical communication and eye safe wavelength region.

  7. Atomic force microscopy studies on growth mechanisms of LAP crystals grown in solution containing excessive amount of L-arginine

    International Nuclear Information System (INIS)

    Geng, Y.L.; Xu, D.; Sun, D.L.; Du, W.; Liu, H.Y.; Zhang, G.H.; Wang, X.Q.

    2005-01-01

    Atomic force microscopy (AFM) has been used to investigate the growth mechanisms of the L-arginine phosphate monohydrate (LAP) crystal grown from the aqueous solution containing excessive amount of L-arginine molecules. Under this condition, the LAP crystals grow by both 2D nucleation mechanism and spiral dislocation mechanism. 2D nucleation growth is the intrinsical growth mechanism owing to the crystal structure of LAP. The spiral growth mechanism probably results from the distortion of the crystal lattices produced by the LA n P unit or separated L-arginine molecule. Pinning points of impurities and curved step type induced by them are also explored

  8. Influences of the CdS nanoparticles grown strategies on CdTe nanorods array films: A comparison between successive ionic layer absorption and reaction and chemical bath deposition

    International Nuclear Information System (INIS)

    Wang, Jun; Zhou, Xiaoming; Lv, Pin; Yang, Lihua; Ding, Dong; Niu, Jiasheng; Liu, Li; Li, Xue; Fu, Wuyou; Yang, Haibin

    2016-01-01

    The cadmium sulfide (CdS) film is deposited on the surface of cadmium telluride (CdTe) nanorods (NRs) by two different methods, successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) techniques. The influence of the deposition parameters on the properties of the films is investigated. Compared to SILAR, CBD is a simple and time saving technique, which can ensure full coverage and better growth of CdS on the surface of CdTe NRs. The photovoltaic characteristics of CdS sensitized CdTe films are also investigated. It is found that the CdTe/CBD-CdS thin film demonstrates excellent photoelectrical properties, which is ascribed to the large absorption coefficient of the material, indicating the potential applications in solar cells.

  9. Vertically Conductive Single-Crystal SiC-Based Bragg Reflector Grown on Si Wafer

    Science.gov (United States)

    Massoubre, David; Wang, Li; Hold, Leonie; Fernandes, Alanna; Chai, Jessica; Dimitrijev, Sima; Iacopi, Alan

    2015-11-01

    Single-crystal silicon carbide (SiC) thin-films on silicon (Si) were used for the fabrication and characterization of electrically conductive distributed Bragg reflectors (DBRs) on 100 mm Si wafers. The DBRs, each composed of 3 alternating layers of SiC and Al(Ga)N grown on Si substrates, show high wafer uniformity with a typical maximum reflectance of 54% in the blue spectrum and a stopband (at 80% maximum reflectance) as large as 100 nm. Furthermore, high vertical electrical conduction is also demonstrated resulting to a density of current exceeding 70 A/cm2 above 1.5 V. Such SiC/III-N DBRs with high thermal and electrical conductivities could be used as pseudo-substrate to enhance the efficiency of SiC-based and GaN-based optoelectronic devices on large Si wafers.

  10. Ultra-fast scintillation properties of β-Ga2O3 single crystals grown by Floating Zone method

    Science.gov (United States)

    He, Nuotian; Tang, Huili; Liu, Bo; Zhu, Zhichao; Li, Qiu; Guo, Chao; Gu, Mu; Xu, Jun; Liu, Jinliang; Xu, Mengxuan; Chen, Liang; Ouyang, Xiaoping

    2018-04-01

    In this investigation, β-Ga2O3 single crystals were grown by the Floating Zone method. At room temperature, the X-ray excited emission spectrum includes ultraviolet and blue emission bands. The scintillation light output is comparable to the commercial BGO scintillator. The scintillation decay times are composed of the dominant ultra-fast component of 0.368 ns and a small amount of slightly slow components of 8.2 and 182 ns. Such fast component is superior to most commercial inorganic scintillators. In contrast to most semiconductor crystals prepared by solution method such as ZnO, β-Ga2O3 single crystals can be grown by traditional melt-growth method. Thus we can easily obtain large bulk crystals and mass production.

  11. Oxygen and zinc vacancies in as-grown ZnO single crystals

    International Nuclear Information System (INIS)

    Wang, X J; Vlasenko, L S; Chen, W M; Buyanova, I A; Pearton, S J

    2009-01-01

    Oxygen and zinc vacancies are unambiguously shown to be formed in as-grown ZnO bulk crystals grown from melt without being subjected to irradiation, from electron paramagnetic resonance (EPR) and optically detected magnetic resonance (ODMR) studies. Concentrations of the defects in their paramagnetic charge states V O + and V Zn - are estimated to be ∼2 x 10 14 cm -3 and ∼10 15 cm -3 , respectively. The V Zn - defect is concluded to act as a deep acceptor and to exhibit large Jahn-Teller distortion by 0.8 eV. The energy level of the defect corresponding to the (2-/-) transition is E v + 1.0 eV. The isolated Zn vacancy is found to be an important recombination centre and is concluded to be responsible for the red luminescence centred at around 1.6 eV. On the other hand, the oxygen vacancy seems to be less important in carrier recombination as it could be detected only in EPR but not in ODMR measurements. Neither isolated V Zn - nor V O + centres participate in the so-called 'green' emission. It is also shown that whereas the concentrations of both defects can be reduced by post-growth annealing, the Zn vacancy exhibits higher thermal stability. The important role of residual contaminants such as Li in the annealing process is underlined.

  12. Simulation of V/G During Φ450 mm Czochralski Grown Silicon Single Crystal Growth Under the Different Crystal and Crucible Rotation Rates

    Directory of Open Access Journals (Sweden)

    Guan X J

    2016-01-01

    Full Text Available For discovering the principle of processing parameter combination for the stable growth and better wafer quality of Φ450 mm Czochralski grown silicon single crystal (shortly called Cz silicon crystal, the effects of crystal rotation rate and crucible one on the V/G ratio were simulated by using CGSim software. The results show that their effect laws on the V/G ratio for Φ450 mm Cz silicon crystal growth are some different from that for Φ200 mm Cz silicon one, and the effects of crucible rotation rate are relatively smaller than that of crystal one and its increasing only makes the demarcation point between two regions with different V/G ratio variations outward move along radial direction, and it promotes the wafer quality to weaken crystal rotation rate and strengthen crucible one.

  13. Third-order NLO properties of solution grown methyl- p-hydroxy benzoate single crystals

    Science.gov (United States)

    Manikandan, S.; Sabari Girisun, T. C.; Mohandoss, R.; Dhanuskodi, S.; Manivannan, S.

    2014-09-01

    The third-order nonlinear optical properties of solution-grown methyl- p-hydroxy benzoate (MHB) single crystals were studied by Z-scan technique using a He-Ne (632.8 nm, 30 mW) laser. From the closed aperture Z-scan data, the valley followed by peak on the normalized transmittance indicates the sign of the nonlinear refractive index is positive and shows a self focusing nature. From the open aperture Z-scan curve, it is found that the nonlinear absorption is due to saturation. The order of magnitude of third order susceptibility was estimated to be 10-6 esu. UV-Vis-NIR spectrum of MHB single crystal reveals a very low cutoff wavelength (310 nm) and transparency in the entire visible region. Also the material has direct allowed transition and it possesses a band gap of 3.7 eV. The dissipation factor is low and SHG efficiency is high. The higher magnitudes of second and third order NLO parameters make the material suitable for photonic applications like frequency conversion and eye/sensor protection.

  14. Investigation of inorganic nonlinear optical potassium penta borate tetra hydrate (PPBTH) single crystals grown by slow evaporation method

    Science.gov (United States)

    Arivuselvi, R.; Babu, P. Ramesh

    2018-03-01

    Borates family crystals were plays vital role in the field of non linear optics (NLO) due to needs of wide range of applications. In this report, NLO crystals (potassium penta borate tetra hydrate (KB5H8O12) are grown by slow evaporation method at room temperature (28° C) and studied their physical properties. The harvested single crystals are transparent with the dimension of 12 × 10 × 6 mm3 and colourless. X-ray diffraction of single crystals reveals that the grown crystal belongs to orthorhombic system with non-centrosymmetric space group Pba2. All the absorbed functional groups are present in the order of inorganic compounds expect 1688 cm-1 because of water (Osbnd H sbnd O blending) molecule present in the pristine. Crystals show transparent in the entire visible region with 5.9 eV optical band gap and also it shows excellence in both second and third order nonlinear optical properties. Crystals can withstand upto 154 °C without any phase changes which is observed using thermal (TGA/DTA) analysis.

  15. Low temperature three-dimensional thermoluminescence spectra of undoped YVO{sub 4} single crystals grown by different techniques

    Energy Technology Data Exchange (ETDEWEB)

    Erdei, S. [Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Kovacs, L. [Research Laboratory for Crystal Physics, Hungarian Academy of Sciences, P.O. Box 132, H-1502 Budapest (Hungary)]|[School of Mathematical and Physical Sciences, University of Sussex, Brighton BN1 9QH (United Kingdom); Peto, A. [Institute of Isotopes, Hungarian Academy of Sciences, P.O. Box 77, H-1525 Budapest (Hungary)]|[School of Mathematical and Physical Sciences, University of Sussex, Brighton BN1 9QH (United Kingdom); Vandlik, J. [Research Institute of Materials Sciences, Hungarian Academy of Sciences, P.O. Box 49, Budapest (Hungary); Townsend, P.D. [School of Mathematical and Physical Sciences, University of Sussex, Brighton BN1 9QH (United Kingdom); Ainger, F.W. [Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    1997-09-01

    Three dimensional (3D) thermoluminescence (TL) spectra of two yttrium orthovanadate (YVO{sub 4}) single crystals grown from YVO{sub 4} melt by the Czochralski (CZ) technique and one additional YVO{sub 4} crystal pulled from lithium-metavanadate (LiVO{sub 3}) flux by the top seeded solution growth (TSSG) method were investigated after x-ray irradiation. The TL spectra were recorded in the 200{endash}800 nm wavelength and 20{endash}300 K temperature ranges before and after annealing of the crystals in an oxygen atmosphere. In spite of the different growth conditions the measured 3D TL spectra of the CZ samples show similar TL characteristics. The main TL emission appears around 450 nm, and between 200 and 250 K. Further weak emissions were also detected at 570, 600, 650, and 710 nm wavelengths, which might be attributed to unwanted impurities. The TL spectrum of the TSSG crystal markedly differs from that of the CZ crystals. On one hand the major TL appears at lower temperatures whereas on the other hand the emission spectrum exhibits a broader band around 500 nm, while the weak bands between 500 and 700 nm could not be detected. Based on these observations the different defect structures in YVO{sub 4} crystals are discussed in the article emphasizing that 3D TL measurement is a useful practical tool for the characterization and identification of YVO{sub 4} crystals grown by different methods. {copyright} {ital 1997 American Institute of Physics.}

  16. Effect of an external magnetic field on polytypism of CdI2 crystals grown from solutions

    International Nuclear Information System (INIS)

    Palosz, B.; Przedmojski, J.

    1982-01-01

    The effect of growth conditions on the polytypic structure of crystals of CdI 2 was analyzed for crystallization from solutions. Three solvents were used: H 2 O, 3 H 2 O + 1 C 2 H 5 OH and 1 H 2 O + 1 C 2 H 5 OH. Crystals were grown at two temperatures: 5 and 25 0 C with low and high growth rates; an external magnetic field of about 0.25 tesla was used. The effect of the above three parameters on the formation of the basic polytypes 2H and 4H and on the ordering of faults in disordered structures and in polytype cells was studied by X-ray analysis of crystal surfaces. Some distinct relations between the polytypic structure of crystals of CdI 2 and the magnetic field were found. (author)

  17. Sodium sulfanilate dihydrate (SSDH) single crystals grown by conventional slow evaporation and Sankaranarayanan–Ramasamy (SR) method and its comparative characterization analysis

    International Nuclear Information System (INIS)

    Senthil Pandian, M.; Ramasamy, P.

    2012-01-01

    Graphical abstract: (a) Unidirectional nonlinear optical sodium sulfanilate dihydrate (SSDH) single crystal grown by SR method and (b and c) cut and polished wafers of SR method grown SSDH single crystals. Highlights: ► Sodium sulfanilate dihydrate single crystal was grown by Sankaranarayanan–Ramasamy method which has the sizes of 100 mm length and 30 mm diameter for the first time. ► The conventional and SR-grown SSDH single crystals were characterized using etching, laser damage threshold, microhardness, UV–vis, birefringence and dielectric tensor analysis. ► The SR-grown SSDH crystal has higher LDT, microhardness, transparency, birefringence and lower dislocation density, dielectric loss than the crystal grown by conventional method. ► The dielectric tensor components were measured and found to be ε 11 = 12.2, ε 22 = 9.5, and ε 33 = 8.5. - Abstract: A transparent uniaxial sodium sulfanilate dihydrate (SSDH) single crystal having dimension of 30 mm diameter and 100 mm length was grown by Sankaranarayanan–Ramasamy (SR) method with a growth rate of 1 mm per day. Using an identical solution the conventional crystal grown to a dimension of 12 mm × 20 mm × 5 mm was obtained over a period of 20 days. The crystal structure has been confirmed by single crystal X-ray diffraction (XRD) measurement. The crystalline perfection of sodium sulfanilate dihydrate crystals grown by slow evaporation solution technique (SEST) and SR method were characterized using chemical etching, laser damage threshold, Vickers microhardness, UV–vis NIR, birefringence and dielectric analysis. The above study indicates that the crystal quality of the Sankaranarayanan–Ramasamy (SR) method grown sodium sulfanilate dihydrate is good compared to conventional solution method grown SSDH crystal. The growth features of inclusions, low angle grain boundaries, twins and micro-cracks have been observed in conventional method grown SSDH crystals. The dielectric tensor components for

  18. The effects of anode material type on the optoelectronic properties of electroplated CdTe thin films and the implications for photovoltaic application

    Science.gov (United States)

    Echendu, O. K.; Dejene, B. F.; Dharmadasa, I. M.

    2018-03-01

    The effects of the type of anode material on the properties of electrodeposited CdTe thin films for photovoltaic application have been studied. Cathodic electrodeposition of two sets of CdTe thin films on glass/fluorine-doped tin oxide (FTO) was carried out in two-electrode configuration using graphite and platinum anodes. Optical absorption spectra of films grown with graphite anode displayed significant spread across the deposition potentials compared to those grown with platinum anode. Photoelectrochemical cell result shows that the CdTe grown with graphite anode became p-type after post-deposition annealing with prior CdCl2 treatment, as a result of carbon incorporation into the films, while those grown with platinum anode remained n-type after annealing. A review of recent photoluminescence characterization of some of these CdTe films reveals the persistence of a defect level at (0.97-0.99) eV below the conduction band in the bandgap of CdTe grown with graphite anode after annealing while films grown with platinum anode showed the absence of this defect level. This confirms the impact of carbon incorporation into CdTe. Solar cell made with CdTe grown with platinum anode produced better conversion efficiency compared to that made with CdTe grown using graphite anode, underlining the impact of anode type in electrodeposition.

  19. Study of optical properties of bulk GaN crystals grown by HVPE

    International Nuclear Information System (INIS)

    Gu, Hong; Ren, Guoqiang; Zhou, Taofei; Tian, Feifei; Xu, Yu; Zhang, Yumin; Wang, Mingyue; Zhang, Zhiqiang; Cai, Demin; Wang, Jianfeng; Xu, Ke

    2016-01-01

    We investigated the optical properties of a series of GaN samples sliced from the same bulk crystal grown using hydride vapor phase epitaxy. The high crystalline quality of the samples was evaluated using cathodoluminescence measurements, and the dislocation density ranged from 2.4 × 10 6 to 2.3 × 10 5 cm −2 . The impurity concentration was determined using secondary-ion mass spectroscopy, and photoluminescence (PL) measurements were conducted in the range of 3–300 K. We did not find a correlation between the O or C impurities and the weak yellow luminescence (YL) band. As the dislocation density decreased, the intensity of the band edge emission increased and that of the YL band decreased. A competition between the two-electron satellite lines correlated to Si and the YL band was also observed in the low-temperature PL spectra, which demonstrated that the Si impurity also plays an important role in the weak YL band of these GaN samples. These results indicate that the Si donors around the dislocations, as reasonable sources of shallow donors, will recombine with possible deep acceptors and finally respond with the YL. - Highlights: • The investigated samples were sliced from the same bulk crystal. • No correlation between the O or C impurities and the weak YL band is observed. • A well-regulated relationship between the YL band and the dislocations is found. • A competition between the TES-Si lines and the YL band is discussed. • The dislocations trapping Si impurity is suggested to be responsible for YL band.

  20. Study of optical properties of bulk GaN crystals grown by HVPE

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Hong; Ren, Guoqiang; Zhou, Taofei; Tian, Feifei; Xu, Yu; Zhang, Yumin; Wang, Mingyue; Zhang, Zhiqiang [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Cai, Demin [Suzhou Nanowin Science and Technology Co., Ltd., Suzhou 215123 (China); Wang, Jianfeng [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Suzhou Nanowin Science and Technology Co., Ltd., Suzhou 215123 (China); Xu, Ke, E-mail: kxu2006@sinano.ac.cn [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Suzhou Nanowin Science and Technology Co., Ltd., Suzhou 215123 (China)

    2016-07-25

    We investigated the optical properties of a series of GaN samples sliced from the same bulk crystal grown using hydride vapor phase epitaxy. The high crystalline quality of the samples was evaluated using cathodoluminescence measurements, and the dislocation density ranged from 2.4 × 10{sup 6} to 2.3 × 10{sup 5} cm{sup −2}. The impurity concentration was determined using secondary-ion mass spectroscopy, and photoluminescence (PL) measurements were conducted in the range of 3–300 K. We did not find a correlation between the O or C impurities and the weak yellow luminescence (YL) band. As the dislocation density decreased, the intensity of the band edge emission increased and that of the YL band decreased. A competition between the two-electron satellite lines correlated to Si and the YL band was also observed in the low-temperature PL spectra, which demonstrated that the Si impurity also plays an important role in the weak YL band of these GaN samples. These results indicate that the Si donors around the dislocations, as reasonable sources of shallow donors, will recombine with possible deep acceptors and finally respond with the YL. - Highlights: • The investigated samples were sliced from the same bulk crystal. • No correlation between the O or C impurities and the weak YL band is observed. • A well-regulated relationship between the YL band and the dislocations is found. • A competition between the TES-Si lines and the YL band is discussed. • The dislocations trapping Si impurity is suggested to be responsible for YL band.

  1. Large-sized SmBCO single crystals with T sub c over 93 K grown in atmospheric ambient by crystal pulling

    CERN Document Server

    Yao Xin; Shiohara, Y

    2003-01-01

    Sm sub 1 sub + sub x Ba sub 2 sub - sub x Cu sub 3 O sub z (SmBCO) single crystals were grown under atmospheric ambient by the top-seeded solution growth method. Inductively coupled plasma results indicate that there is negligible Sm substitution for Ba sites in the grown SmBCO crystals, although they crystallized from different Ba-Cu-O solvents with a wide composition range (Ba/Cu ratio of 0.5-0.6). As a result, these crystals show high superconducting critical transition temperature values (T sub c) of over 93 K with a sharp transition width after oxygenation. A large-sized crystal with an a-b plane of 23 x 22 mm sup 2 and a c-axis of 19 mm was obtained at a high growth rate of nearly 0.13 mm h sup - sup 1. In short, with more controllable thermodynamic parameters, SmBCO single crystals can readily achieve both large size and high superconducting properties. (rapid communication)

  2. Solution-grown crystals for neutron radiation detectors, and methods of solution growth

    Science.gov (United States)

    Zaitseva, Natalia; Carman, M Leslie; Payne, Steve

    2014-10-28

    An organic crystal according to one embodiment includes an organic crystal comprising diphenylacetylene and stilbene or a stilbene derivative, the crystal having physical characteristics of formation from solution, the organic crystal exhibiting a signal response signature for neutrons from a radioactive source. A system according to one embodiment includes an organic crystal comprising diphenylacetylene and stilbene or a stilbene derivative, the crystal having physical characteristics of formation from solution, the organic crystal exhibiting a signal response signature for neutrons from a radioactive source; and a photodetector for detecting the signal response of the organic crystal. Methods of making such crystals are also provided.

  3. Studies on the growth aspects, structural, thermal, dielectric and third order nonlinear optical properties of solution grown 4-methylpyridinium p-nitrophenolate single crystal

    Science.gov (United States)

    Devi, S. Reena; Kalaiyarasi, S.; Zahid, I. MD.; Kumar, R. Mohan

    2016-11-01

    An ionic organic optical crystal of 4-methylpyridinium p-nitrophenolate was grown from methanol by slow evaporation method at ambient temperature. Powder and single crystal X-ray diffraction studies revealed the crystal system and its crystalline perfection. The rocking curve recorded from HRXRD study confirmed the crystal quality. FTIR spectral analysis confirmed the functional groups present in the title compound. UV-visible spectral study revealed the optical window and band gap of grown crystal. The thermal, electrical and surface laser damage threshold properties of harvested crystal were examined by using TGA/DTA, LCR/Impedance Analyzer and Nd:YAG laser system respectively. The third order nonlinear optical property of grown crystal was elucidated by Z-scan technique.

  4. The effect of radiation damage on optical and scintillation properties of BGO crystals grown by the LTG Cz technique

    CERN Document Server

    Gusev, V A; Kupriyanov, I N; Kuznecov, G N; Shlegel, V N; Antsygin, V D; Vasiliev, Y V

    2002-01-01

    BGO crystals grown by the low-thermal-gradient Czochralski technique (LTG Cz) exhibit two distinct types of behavior upon radiation damage and recovery. The crystals termed as of L-type remain colorless after gamma-radiation doses as high as 10 Mrad. As the irradiation dose increases the scintillation light output shows a weak monotonous degradation to 15-25%, saturating at around several hundreds krad doses. The crystals termed as of N-type attain yellow coloration after irradiation. The light output drops abruptly for 35-50% as early as after 1 krad and does not change further on. The present work is devoted to the study of radiation damage effects, self-recovery, optically stimulated recovery and thermo-stimulated current in the L- and N-type BGO crystals produced by LTG Cz.

  5. Analysis of CZT crystals and detectors grown in Russia and the Ukraine by high-pressure Bridgman methods

    Energy Technology Data Exchange (ETDEWEB)

    H. Hermon; M. Schieber; R. B. James; E. Y. Lee; N. Yang; A. J. Antolak; D. H. Morse; C. Hackett; E. Tarver; N. N. P. Kolesnikov; Yu N. Ivanov; V. Komar; M. S. Goorsky; H. Yoon

    2000-01-10

    Sandia National Laboratories (SNL) is leading an effort to evaluate vertical high pressure Bridgman (VHPB) Cd{sub 1-x}Zn{sub x}Te (CZT) crystals grown in the former Soviet Union (FSU) (Ukraine and Russia), in order to study the parameters limiting the crystal quality and the radiation detector performance. The stoichiometry of the CZT crystals, with 0.04 < x < 0.25, has been determined by methods such as proton-induced X-ray emission (PIXE), X-ray diffraction (XRD), microprobe analysis and laser ablation ICP mass spectroscopy (LA-ICP/MS). Other methods such as triaxial double crystal x-ray diffraction (TADXRD), infrared transmission spectroscopy (IR), atomic force microscopy (AFM), thermoelectric emission spectroscopy (TEES) and laser induced transient charge technique (TCT) were also used to evaluate the material properties. The authors have measured the zinc distribution in a CZT ingot along the axial direction and also its homogeneity. The (Cd+Zn)/Te average ratio measured on the Ukraine crystals was 1.2, compared to the ratio of 0.9-1.06 on the Russian ingots. The IR transmission showed highly decorated grain boundaries with precipitates and hollow bubbles. Microprobe elemental analysis and LA-ICP/MS showed carbon precipitates in the CZT bulk and carbon deposits along grain boundaries. The higher concentration of impurities and the imperfect crystallinity lead to shorter electron and hole lifetimes in the range of 0.5--2 {micro}s and 0.1 {micro}s respectively, compared to 3--20 {micro}s and 1--7 {micro}s measured on US spectrometer grade CZT detectors. These results are consistent with the lower resistivity and worse crystalline perfection of these crystals, compared to US grown CZT. However, recently grown CZT from FSU exhibited better detector performance and good response to alpha particles.

  6. Solution-grown crystals for neutron radiation detectors, and methods of solution growth

    Science.gov (United States)

    Zaitseva, Natalia P; Hull, Giulia; Cherepy, Nerine J; Payne, Stephen A; Stoeffl, Wolfgang

    2012-06-26

    A method according to one embodiment includes growing an organic crystal from solution, the organic crystal exhibiting a signal response signature for neutrons from a radioactive source. A system according to one embodiment includes an organic crystal having physical characteristics of formation from solution, the organic crystal exhibiting a signal response signature for neutrons from a radioactive source; and a photodetector for detecting the signal response of the organic crystal. A method according to another embodiment includes growing an organic crystal from solution, the organic crystal being large enough to exhibit a detectable signal response signature for neutrons from a radioactive source. An organic crystal according to another embodiment includes an organic crystal having physical characteristics of formation from solution, the organic crystal exhibiting a signal response signature for neutrons from a radioactive source, wherein the organic crystal has a length of greater than about 1 mm in one dimension.

  7. Experimental phasing for structure determination using membrane-protein crystals grown by the lipid cubic phase method

    Science.gov (United States)

    Li, Dianfan; Pye, Valerie E.; Caffrey, Martin

    2015-01-01

    Despite the marked increase in the number of membrane-protein structures solved using crystals grown by the lipid cubic phase or in meso method, only ten have been determined by SAD/MAD. This is likely to be a consequence of the technical difficulties associated with handling proteins and crystals in the sticky and viscous hosting mesophase that is usually incubated in glass sandwich plates for the purposes of crystallization. Here, a four-year campaign aimed at phasing the in meso structure of the integral membrane diacylglycerol kinase (DgkA) from Escherichia coli is reported. Heavy-atom labelling of this small hydrophobic enzyme was attempted by pre-labelling, co-crystallization, soaking, site-specific mercury binding to genetically engineered single-cysteine mutants and selenomethionine incorporation. Strategies and techniques for special handling are reported, as well as the typical results and the lessons learned for each of these approaches. In addition, an assay to assess the accessibility of cysteine residues in membrane proteins for mercury labelling is introduced. The various techniques and strategies described will provide a valuable reference for future experimental phasing of membrane proteins where crystals are grown by the lipid cubic phase method. PMID:25615865

  8. Factors affecting stress distribution and displacements in crystals III-V grown by Czochralski method with liquid encapsulation

    International Nuclear Information System (INIS)

    Schvezov, C.E.; Samarasekera, I.; Weinberg, F.

    1988-01-01

    A mathematical model based on the finite element method for calculating temperature and shear stress distributions in III-V crystals grown by LEC technique was developed. The calculated temperature are in good agreements with the experimental measurements. The shear stress distribution was calculated for several environmental conditions. The results showed that the magnitude and the distribution of shear stresses are highly sensitive to the crystal environment, including thickness and temperature distribution in boron oxides and the gas. The shear stress is also strongly influenced by interface curvature and cystals radius. (author) [pt

  9. Approaches to improve the Voc of CDTE devices: Device modeling and thinner devices, alternative back contacts

    Science.gov (United States)

    Walkons, Curtis J.

    An existing commercial process to develop thin film CdTe superstrate cells with a lifetime tau=1-3 ns results in Voc= 810-850 mV which is 350 mV lower than expected for CdTe with a bandgap EG = 1.5 eV. Voc is limited by 1.) SRH recombination in the space charge region; and 2.) the Cu2Te back contact to CdTe, which, assuming a 0.3 eV CdTe/Cu2Te barrier, exhibits a work function of phi Cu2Te= 5.5 eV compared to the CdTe valence band of Ev,CdTe=5.8 eV. Proposed solutions to develop CdTe devices with increased Voc are: 1.) reduce SRH recombination by thinning the CdTe layer to ≤ 1 mum; and 2.) develop an ohmic contact back contact using a material with phi BC≥5.8 eV. This is consistent with simulations using 1DSCAPS modeling of CdTe/CdS superstrate cells under AM 1.5 conditions. Two types of CdTe devices are presented. The first type of CdTe device utilizes a window/CdTe stack device with an initial 3-9 mum CdTe layer which is then chemically thinned resulting in regions of the CdTe film with thickness less than 1 mum. The CdTe surface was contacted with a liquid junction quinhydrone-Pt (QH-Pt) probe which enables rapid repeatable Voc measurements on CdTe before and after thinning. In four separate experiments, the window/CdTe stack devices with thinned CdTe exhibited a Voc increase of 30-170 mV, which if implemented using a solid state contact could cut the Voc deficit in half. The second type of CdTe device utilizes C61 PCBM as a back contact to the CdTe, selected since PCBM has a valence band maximum energy (VBM) of 5.8 eV. The PCBM films were grown by two different chemistries and the characterization of the film properties and device results are discussed. The device results show that PCBM exhibits a blocking contact with a 0.6 eV Schottky barrier and possible work function of phiPCBM = 5.2 eV.

  10. 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.

  11. Diode-pumped laser with Yb:YAG single-crystal fiber grown by the micro-pulling down technique

    Science.gov (United States)

    Sangla, D.; Aubry, N.; Didierjean, J.; Perrodin, D.; Balembois, F.; Lebbou, K.; Brenier, A.; Georges, P.; Tillement, O.; Fourmigué, J.-M.

    2009-02-01

    Laser emission obtained from an Yb:YAG single-crystal fiber directly grown by the micro-pulling down technique is demonstrated for the first time. We achieved 11.2 W of continuous wave (CW) output power at 1031 nm for 55 W of incident pump power at 940 nm. In the Q-switched regime, we obtained pulses as short as 17 ns, for an average power of 2.3 W at 2 kHz corresponding to an energy of 1.15 mJ. In both cases, the M 2 factor was 2.5. This single-crystal fiber showed performance similar to a standard rod elaborated by the Czochralski method. The potential of Yb3+-doped single-crystal fibers is presented for scalable high-average and high-peak-power laser systems.

  12. Distribution of Al and in impurities along homogeneous Ge-Si crystals grown by the Czochralski method using Si feeding rod

    Science.gov (United States)

    Kyazimova, V. K.; Alekperov, A. I.; Zakhrabekova, Z. M.; Azhdarov, G. Kh.

    2014-05-01

    A distribution of Al and In impurities in Ge1 - x Si x crystals (0 ≤ x ≤ 0.3) grown by a modified Czochralski method (with continuous feeding of melt using a Si rod) have been studied experimentally and theoretically. Experimental Al and In concentrations along homogeneous crystals have been determined from Hall measurements. The problem of Al and In impurity distribution in homogeneous Ge-Si single crystals grown in the same way is solved within the Pfann approximation. A set of dependences of Al and In concentrations on the crystal length obtained within this approximation demonstrates a good correspondence between the experimental and theoretical data.

  13. Growth, mechanical, and magnetic study of SmFeO{sub 3} single crystal grown by optical floating zone technique

    Energy Technology Data Exchange (ETDEWEB)

    Babu, P. Ramesh [Centre for Crystal Growth, VIT University, Vellore, Tamil Nadu (India); Bhaumik, Indranil [Crystal Growth Laboratory, Laser Materials Development and Devices Division, RRCAT, Indore (India); Ganesamoorthy, S. [Material Science Group, IGCAR, Kalpakkam, Tamil Nadu (India); Kalainathan, S., E-mail: kalainathan@yahoo.com [Centre for Crystal Growth, VIT University, Vellore, Tamil Nadu (India); Bhatt, R.; Karnal, A.K.; Gupta, P.K. [Crystal Growth Laboratory, Laser Materials Development and Devices Division, RRCAT, Indore (India)

    2016-08-15

    Single crystals of Samarium orthoferrite (SmFeO{sub 3}) have been grown by the optical floating zone technique. The growth parameters to yield good quality crystals are 5 mm/h for pulling and 30–40 rpm for rotation. The mechanical behavior of the grown crystal has been investigated. Rosette pattern has been observed around the indentation and the microhardness has been found to decreases non-linearly with the applied load. For load higher than 1.96 N there is a transition from palmqvist to median crack due to plastic deformation of the crystal. The hardness parameters like fracture toughness, brittleness index, and yield strength have also been calculated for palmqvist and median cracks occurring on the crystal surface. The magnetic investigations revealed that a magnetic transition in the range of 300–180 K. Above 180 K, the magnetization decreases as Sm and Fe sublattices have opposite spins. At high temperature, two anomalies are observed, one due to near spin reorientation (T{sub SR} = 480 K) and the other is AFM to paramagnetic transitions (T{sub N} = 670 K). The M–H curves exhibit a shape change with temperature due to the emergence and enlargement of multi-domain state of the SmFeO{sub 3} crystals. Bloch parameter (3.28 × 10{sup −5} K{sup −3/2}) has also been evaluated. - Highlights: • SmFeO{sub 3} single crystals have been grown by OFZ technique in air. • The microhardness has been found to decreases non-linearly with the applied load. • At 472 K, spin reorientation occurs in Fe sublattice. • The M–H curves exhibit a shape change with temperature due to the emergence and enlargement of multi-domain state. • Bloch 3/2-law holds good for SmFeO{sub 3} (B-parameter as 3.28 × 10{sup −5} K{sup −3/2}).

  14. 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.

  15. Growth and Characteristics of Bulk Single Crystals Grown from Solution on Earth and in Microgravity

    Science.gov (United States)

    Aggarwal, M. D.; Batra, A. K.; Lal, R. B.; Penn, Benjamin G.; Frazier, Donald O.

    2011-01-01

    The growth of crystals has been of interest to physicists and engineers for a long time because of their unique properties. Single crystals are utilized in such diverse applications as pharmaceuticals, computers, infrared detectors, frequency measurements, piezoelectric devices, a variety of high technology devices and sensors. Solution crystal growth is one of the important techniques to grow a variety of crystals when the material decomposes at the melting point and a suitable solvent is available to make a saturated solution at a desired temperature. In this chapter an attempt is made to give some fundamentals of growing crystals from solution including improved designs of various crystallizers. Since the same solution crystal growth technique could not be used in microgravity, authors had proposed a new cooled sting technique to grow crystals in space. Authors? experiences of conducting two space shuttle experiments relating to solution crystal growth are also detailed in this work. The complexity of these solution growth experiments to grow crystals in space are discussed. These happen to be some of the early experiments performed in space, and various lessons learned are described. A brief discussion of protein crystal growth that also shares basic principles of solution growth technique is given along with some flight hardware information for its growth in microgravity.

  16. 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)

  17. Ce-doped LuAG single-crystal fibers grown from the melt for high-energy physics

    CERN Document Server

    Xu, X; Moretti, F; Pauwels, K; Lecoq, P; Auffray, E; Dujardin, C

    2014-01-01

    Under a stationary stable regime undoped and Ce-doped LuAG (Lu3Al5O12) single-crystal fibers were grown by a micro-pulling-down technique. The meniscus length corresponding to the equilibrium state was <200 mu m. Fluctuations in the fiber composition and pulling rate were found to have a significant effect on the properties of the fibers grown. A great improvement in the performance was found in samples containing low Ce concentrations (<= 0.1 at.\\%) and produced using pulling rates <0.5 mm min(-1). Under such conditions a good lateral surface fiber quality was obtained and light propagation was significantly improved. Conversely, a high Ce concentration and a high pulling rate resulted in a strong degradation of the fiber surface quality causing defects to appear and a decrease in light output. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  18. Optimization and characterization of bulk hexagonal boron nitride single crystals grown by the nickel-chromium flux method

    Science.gov (United States)

    Hoffman, Tim

    Hexagonal boron nitride (hBN) is a wide bandgap III-V semiconductor that has seen new interest due to the development of other III-V LED devices and the advent of graphene and other 2-D materials. For device applications, high quality, low defect density materials are needed. Several applications for hBN crystals are being investigated, including as a neutron detector and interference-less infrared-absorbing material. Isotopically enriched crystals were utilized for enhanced propagation of phonon modes. These applications exploit the unique physical, electronic and nanophotonics applications for bulk hBN crystals. In this study, bulk hBN crystals were grown by the flux method using a molten Ni-Cr solvent at high temperatures (1500°C) and atmospheric pressures. The effects of growth parameters, source materials, and gas environment on the crystals size, morphology and purity were established and controlled, and the reliability of the process was greatly improved. Single-crystal domains exceeding 1mm in width and 200microm in thickness were produced and transferred to handle substrates for analysis. Grain size dependence with respect to dwell temperature, cooling rate and cooling temperature were analyzed and modeled using response surface morphology. Most significantly, crystal grain width was predicted to increase linearly with dwell temperature, with single-crystal domains exceeding 2mm in at 1700°C. Isotopically enriched 10B and 11B hBN crystal were produced using a Ni-Cr-B flux method, and their properties investigated. 10B concentration was evaluated using SIMS and correlated to the shift in the Raman peak of the E2g mode. Crystals with enrichment of 99% 10B and >99% 11B were achieved, with corresponding Raman shift peaks at 1392.0 cm-1 and 1356.6 cm-1, respectively. Peak FWHM also decreased as isotopic enrichment approached 100%, with widths as low as 3.5 cm-1 achieved, compared to 8.0 cm-1 for natural abundance samples. Defect selective etching was

  19. Surface structures of normal paraffins and cyclohexane monolayers and thin crystals grown on the (111) crystal face of platinum. A low-energy electron diffraction study

    International Nuclear Information System (INIS)

    Firment, L.E.; Somorjai, G.A.

    1977-01-01

    The surfaces of the normal paraffins (C 3 --C 8 ) and cyclohexane have been studied using low-energy electron diffraction (LEED). The samples were prepared by vapor deposition on the (111) face of a platinum single crystal in ultrahigh vacuum, and were studied both as thick films and as adsorbed monolayers. These molecules form ordered monolayers on the clean metal surface in the temperature range 100--220 K and at a vapor flux corresponding to 10 -7 Torr. In the adsorbed monolayers of the normal paraffins (C 4 --C 8 ), the molecules lie with their chain axes parallel to the Pt surface and Pt[110]. The paraffin monolayer structures undergo order--disorder transitions as a function of temperature. Multilayers condensed upon the ordered monolayers maintained the same orientation and packing as found in the monolayers. The surface structures of the growing organic crystals do not corresond to planes in their reported bulk crystal structures and are evidence for epitaxial growth of pseudomorphic crystal forms. Multilayers of n-octane and n-heptane condensed upon disordered monolayers have also grown with the (001) plane of the triclinic bulk crystal structures parallel to the surface. n-Butane has three monolayer structures on Pt(111) and one of the three is maintained during growth of the crystal. Cyclohexane forms an ordered monolayer, upon which a multilayer of cyclohexane grows exhibiting the (001) surface orientation of the monoclinic bulk crystal structure. Surface structures of saturated hydrocarbons are found to be very susceptible to electron beam induced damage. Surface charging interferes with LEED only at sample thicknesses greater than 200 A

  20. Growth, morphology, spectral and thermal studies of gel grown diclofenac acid crystals

    Science.gov (United States)

    Ramachandran, E.; Ramukutty, S.

    2014-03-01

    The crystal growth of diclofenac acid in silica gel is the first to be reported in literature. The growth parameters were varied to optimize the suitable growth condition. Single crystal X-ray diffraction method was used for the conformation of the crystal structure. Morphology studies showed that the growth is prominent along the b-axis and the prominent face is {002}. Fourier transform infrared spectral study was performed to identify the functional groups present in the crystal. Thermal stability and decomposition of the material were analyzed using thermo calorimetry in the temperature range 30-500 °C.

  1. Effects of tellurium concentration on the structure of melt-grown ZnSe crystals

    International Nuclear Information System (INIS)

    Atroshchenko, Lyubov V.; Galkin, Sergey N.; Rybalka, Irina A.; Voronkin, Evgeniy F.; Lalayants, Alexandr I.; Ryzhikov, Vladimir D.; Fedorov, Alexandr G.

    2005-01-01

    It has been shown that isovalent doping by tellurium positively affects the structural perfection of ZnSe crystals related to the completeness of the wurtzite-sphalerite phase transition. The optimum concentration range of tellurium in ZnSe crystals is 0.3-0.6 mass %. X-ray diffraction studies have shown that in ZnSe 1-x Te x crystals at tellurium concentrations below 0.3 mass % twinning and packing defects occur, while tellurium concentrations above 0.6 mass % lead to formation of tetragonal crystal lattice

  2. Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Joel Glenn [Univ. of California, Berkeley, CA (United States)

    2000-05-01

    The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby allowing the use of electron-based techniques to characterize the surface.

  3. Study of gel grown mixed crystals of Bax (IO3 )4

    Indian Academy of Sciences (India)

    Administrator

    Mixed iodate crystals of barium calcium iodate are used in medicine and production of other iodates. The purpose of the present paper is to report the growth and influence of various parameters such as pH of gel, gel reactants, gel concentrations, effect of neutral gel etc on the growth mechanism of mixed iodate crystals of.

  4. The twisting of LiNbO3 single crystals grown by the Czochralski method

    International Nuclear Information System (INIS)

    Erdei, S.; Gabrieljan, V.T.

    1989-01-01

    As a result of our experimental work of mainly practical importance we established that for LiNbO 3 single crystals the Mg and Fe dopants promote spirality whereas decreasing of the pulling velocity strongly reduces the propensity of the system to produce spiral-shaped crystals. (author)

  5. Flux-enhanced monochromator by ultrasound excitation of annealed Czochralski-grown silicon crystals

    CERN Document Server

    Koehler, S; Seitz, C; Magerl, A; Mashkina, E; Demin, A

    2003-01-01

    The neutron flux from monochromator crystals can be increased by ultrasound excitation or by strain fields. Rocking curves of both a perfect float-zone silicon crystal and an annealed Czochralski silicon crystal with oxygen precipitates were measured at various levels of ultrasound excitation on a cold-neutron backscattering spectrometer. We find that the effects of the dynamic strain field from the ultrasound and the static strain field from the defects are not additive. Rocking curves were also taken at different ultrasound frequencies near resonance of the crystal/ultrasound-transducer system with a time resolution of 1 min. Pronounced effects of crystal heating are observed, which render the conditions for maximum neutron reflectivity delicate. (orig.)

  6. GaN Schottky diodes with single-crystal aluminum barriers grown by plasma-assisted molecular beam epitaxy

    Science.gov (United States)

    Tseng, H. Y.; Yang, W. C.; Lee, P. Y.; Lin, C. W.; Cheng, Kai-Yuan; Hsieh, K. C.; Cheng, K. Y.; Hsu, C.-H.

    2016-08-01

    GaN-based Schottky barrier diodes (SBDs) with single-crystal Al barriers grown by plasma-assisted molecular beam epitaxy are fabricated. Examined using in-situ reflection high-energy electron diffractions, ex-situ high-resolution x-ray diffractions, and high-resolution transmission electron microscopy, it is determined that epitaxial Al grows with its [111] axis coincident with the [0001] axis of the GaN substrate without rotation. In fabricated SBDs, a 0.2 V barrier height enhancement and 2 orders of magnitude reduction in leakage current are observed in single crystal Al/GaN SBDs compared to conventional thermal deposited Al/GaN SBDs. The strain induced piezoelectric field is determined to be the major source of the observed device performance enhancements.

  7. GaN Schottky diodes with single-crystal aluminum barriers grown by plasma-assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Tseng, H. Y.; Yang, W. C.; Lee, P. Y.; Lin, C. W.; Cheng, Kai-Yuan; Hsieh, K. C.; Cheng, K. Y., E-mail: kycheng@ee.nthu.edu.tw [Department of Electrical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Hsu, C.-H. [Division of Scientific Research, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China)

    2016-08-22

    GaN-based Schottky barrier diodes (SBDs) with single-crystal Al barriers grown by plasma-assisted molecular beam epitaxy are fabricated. Examined using in-situ reflection high-energy electron diffractions, ex-situ high-resolution x-ray diffractions, and high-resolution transmission electron microscopy, it is determined that epitaxial Al grows with its [111] axis coincident with the [0001] axis of the GaN substrate without rotation. In fabricated SBDs, a 0.2 V barrier height enhancement and 2 orders of magnitude reduction in leakage current are observed in single crystal Al/GaN SBDs compared to conventional thermal deposited Al/GaN SBDs. The strain induced piezoelectric field is determined to be the major source of the observed device performance enhancements.

  8. 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.

  9. 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

  10. Superstructure studies in hydrothermal-grown RbBe{sub 2}BO{sub 3}F{sub 2} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tao [Beijing Center for Crystal Research and Development, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, P.O. Box 2711, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100039 (China); Liu, Lijuan, E-mail: llj@mail.ipc.ac.cn [Beijing Center for Crystal Research and Development, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, P.O. Box 2711, Beijing 100190 (China); Wang, Xiaoyang [Beijing Center for Crystal Research and Development, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, P.O. Box 2711, Beijing 100190 (China); Zhou, Haitao; He, Xiaoling; Zhang, Changlong [China Nonferrous Metal (Guilin) Geology and Mining Co., Ltd., No. 20 Tieshan Road, Guilin, GuangXi 541004 (China); Chen, Chuangtian [Beijing Center for Crystal Research and Development, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, P.O. Box 2711, Beijing 100190 (China)

    2015-03-15

    Highlights: • Three extra peaks were found in PXRD patterns of hydrothermal RBBF crystals. • A centrosymmetric structure of R3{sup ¯}c was obtained in hydrothermal RBBF crystals. • A stacking fault model of hydrothermal RBBF crystals was proposed. • R32 and R3{sup ¯}c structures co-exist with different weight fractions. - Abstract: Deep-UV nonlinear optical crystal RbBe{sub 2}BO{sub 3}F{sub 2} (RBBF) grown by the hydrothermal method was found to have a centrosymmetric structure of R3{sup ¯}c by powder X-ray diffraction. The structure of R3{sup ¯}c has cell parameters of a = 4.44223(11) Å and c = 39.6696(12) Å in the lattice where the (BO{sub 3}){sup 3−} groups turn 60° along each (Be{sub 2}BO{sub 3}F{sub 2}){sub ∞} layer in the a–b plane and it is double size along the c-axis compared with standard R32 structure. As the examined RBBF shows a very low second harmonic generation capability, a stacking fault model was proposed that the hydrothermal RBBF is nonuniform with a mixture of both R32 and R3{sup ¯}c structures using the DIFFaX program.

  11. 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.

  12. Compositional uniformity of a Si0.5Ge0.5 crystal grown on board the International Space Station

    Science.gov (United States)

    Kinoshita, K.; Arai, Y.; Inatomi, Y.; Tsukada, T.; Miyata, H.; Tanaka, R.; Yoshikawa, J.; Kihara, T.; Tomioka, H.; Shibayama, H.; Kubota, Y.; Warashina, Y.; Ishizuka, Y.; Harada, Y.; Wada, S.; Ito, T.; Nagai, N.; Abe, K.; Sumioka, S.; Takayanagi, M.; Yoda, S.

    2015-06-01

    A Si0.5Ge0.5 crystal was grown on board the International Space Station (ISS) using the traveling liquidus-zone method. Average Ge concentration was 49±2 at% for the growth length of 14.5 mm. Radial compositional uniformity was excellent especially between the growth length of 3 and 9 mm; concentration fluctuation was less than 1 at%. In this experiment, cartridge surface temperatures were monitored and heater temperatures were adjusted based on the monitored temperatures for improving compositional uniformity of a grown crystal. A step temperature change by 1 °C was imposed for adjusting heater temperatures. This procedure made it possible to observe growth interface shape; striations due to heater temperature change were observed by a backscattered electron image. Growth rates were precisely determined by the relation between interval of heater temperature change and the distance between striations. Based on the measured growth rates, two-dimensional growth model for the traveling liquidus-zone method was discussed.

  13. Determination of intrinsic polarization for K{sub 2}ZnCl{sub 4} single crystal grown by Czochralski technique for ferroelectric applications

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sonu [Crystal Lab, Department of Physics & Astrophysics, University of Delhi, Delhi-7 (India); Ray, Geeta [Crystal Lab, Department of Physics & Astrophysics, University of Delhi, Delhi-7 (India); Physics Department, Miranda House, University of Delhi, Delhi-7 (India); Sinha, Nidhi [Crystal Lab, Department of Physics & Astrophysics, University of Delhi, Delhi-7 (India); Department of Electronics, SGTB Khalsa College, University of Delhi, Delhi-7 (India); Kumar, Binay, E-mail: b3kumar69@yahoo.co.in [Crystal Lab, Department of Physics & Astrophysics, University of Delhi, Delhi-7 (India)

    2017-04-01

    Large sized single crystal of K{sub 2}ZnCl{sub 4} (KZC) was grown by Czochralski (Cz) technique. Structural parameters of KZC were determined by Single crystal X-ray diffraction (SCXRD). From DSC analysis and temperature dependent dielectric measurement, KZC crystal was found to show Curie phase transition at 151 °C. TG/DTA confirmed the melting point that was found to be 443 °C. The value of piezoelectric charge coefficient (d{sub 33}) for KZC crystal was found to be 32 pC/N demonstrating their applicability in transducers and piezoelectric devices. Ferroelectric P-E loop for the grown crystal was traced at room temperature and the intrinsic polarization obtained by PUND measurement was found to be 0.1398 μC/cm{sup 2} indicating its applicability in switching devices. The energy band gap for KZC single crystal was found to be 6.13 eV. Vickers micro-hardness test revealed soft nature of KZC single crystals. - Highlights: • Large sized K{sub 2}ZnCl{sub 4} (KZC) single crystal was grown by Czochralski technique. • It possesses high Curie temperature as 151 °C. • d{sub 33} coefficient was found to be 32 pC/N. • Intrinsic polarization measured by PUND. • Its direct band gap energy was calculated to be 6.13 eV.

  14. Characterization and inhibitive study of gel-grown hydroxyapatite crystals at physiological temperature

    Science.gov (United States)

    Parekh, Bharat; Joshi, Mihir; Vaidya, Ashok

    2008-04-01

    Hydroxyapatite is very useful for various biomedical applications, due to its chemical similarity with mineralized bone of human. Hydroxyapatite is also responsible for arthropathy (joint disease). In the present study, the growth of hydroxyapatite crystals was carried out by using single-diffusion gel growth technique in silica hydro gel media, at physiological temperature. The growth of hydroxyapatite crystals under slow and controlled environment in gel medium can be simulated in a simple manner to the growth in human body. The crystals, formed in the Liesegang rings, were characterized by powder XRD, FTIR and dielectric study. The diffusion study is also carried out for the hydroxyapatite crystals using the moving boundary model. The inhibitive influence of various Ayurvedic medicinal plant extracts such as Boswellia serrata gum resin , Tribulus terrestris fruits, Rotula aquatica roots, Boerhaavia diffusa roots and Commiphora wightii, on the growth of hydroxyapatite was studied. Roots of R. aquatica and B. diffusa show some inhibition of the hydroxyapatite crystals in vitro. This preclinical study will be helpful to design the therapy for prevention of hydroxyapatite-based ailments.

  15. Analysis of polytype stability in PVT grown silicon carbide single crystal using competitive lattice model Monte Carlo simulations

    Directory of Open Access Journals (Sweden)

    Hui-Jun Guo

    2014-09-01

    Full Text Available Polytype stability is very important for high quality SiC single crystal growth. However, the growth conditions for the 4H, 6H and 15R polytypes are similar, and the mechanism of polytype stability is not clear. The kinetics aspects, such as surface-step nucleation, are important. The kinetic Monte Carlo method is a common tool to study surface kinetics in crystal growth. However, the present lattice models for kinetic Monte Carlo simulations cannot solve the problem of the competitive growth of two or more lattice structures. In this study, a competitive lattice model was developed for kinetic Monte Carlo simulation of the competition growth of the 4H and 6H polytypes of SiC. The site positions are fixed at the perfect crystal lattice positions without any adjustment of the site positions. Surface steps on seeds and large ratios of diffusion/deposition have positive effects on the 4H polytype stability. The 3D polytype distribution in a physical vapor transport method grown SiC ingot showed that the facet preserved the 4H polytype even if the 6H polytype dominated the growth surface. The theoretical and experimental results of polytype growth in SiC suggest that retaining the step growth mode is an important factor to maintain a stable single 4H polytype during SiC growth.

  16. Anisotropy in Ba2Cu3O4Cl2 single crystals grown by the traveling solvent floating zone method

    International Nuclear Information System (INIS)

    Yamada, Shigeki; Iwagaki, Yohei; Noro, Sumiko

    2007-01-01

    Magnetic and electrical properties of layered copper oxychloride Ba 2 Cu 3 O 4 Cl 2 single crystals are measured. Single crystal growth of Ba 2 Cu 3 O 4 Cl 2 by the traveling solvent floating zone method is attempted using Ba 3 Cu 2 O 4 Cl 2 as solvent. By optimization of the growth conditions, large single crystals of (φ5mmx30mm) of Ba 2 Cu 3 O 4 Cl 2 are grown. The resistivity with the current parallel to the c-axis is 10 2 -10 3 times larger than that with the current perpendicular to the a-axis. The temperature dependence of the dielectric spectrum for each direction is measured and analyzed by using the Debye model. The spectrum width, which is related to the effective number of electrons (n/m), does not show an appreciable dependence on temperature. The characteristic frequencies at which the dielectric constant changes, which are related to the dissipation (γ), increase with warming. The temperature dependence is almost the same as the resistivity curve. This indicates that the hopping process dominates both DC- and AC-type electrical transport. The spectrum width with the electric field parallel to the a-axis is 30 times larger than that with the electric field parallel to the c-axis. On the other hand, the characteristic frequencies do not show an appreciable dependence on electric field direction

  17. Synthesis, structural, optical and thermal properties of N-methyl-N-aryl benzamide organic single crystals grown by a slow evaporation technique

    Science.gov (United States)

    Prabukanthan, P.; Lakshmi, R.; Harichandran, G.; Kumar, C. Sudarsana

    2018-03-01

    The organic materials, N-methyl-N-aryl benzamides were synthesized from benzoylation of N-methyl-4-nitrobenzenamine (MNBA) using suitably substituted benzoyl chlorides. The products were purified by recrystallization and their single crystal were grown by a slow evaporation technique. The crystals were characterized by FTIR, UV-Vis-NIR, 1H &13C NMR, and single & powder X-ray diffraction. Thermal stability of the crystals was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Dielectric and NLO properties of MNPB, FMNPB and MMNPB crystals were studied. The second harmonic generation (SHG) has been confirmed by the Kurtz powder test for all these crystals and the SHG efficiency of MMNPB crystal was found to be 2.25 times higher than that of KDP crystal.

  18. Growth and study of some gel grown group II single crystals of iodate

    Indian Academy of Sciences (India)

    Unknown

    The effect of doping was studied using IR spectroscopy and thermal analysis. Keywords. Silica gel; barium iodate; calcium iodate; XRD; FT-IR; TGA/DTA. 1. .... Table 2. Effect of concentration of reactants on habit quality and size of BaIO3 crystals. Conc. of reactant in gel. Conc. of reactant above gel. Habit. Quality. Size. (mm).

  19. Physical properties of lauric acid crystals grown with KBr in aqueous ...

    Indian Academy of Sciences (India)

    2018-03-28

    Mar 28, 2018 ... conversion, colour display, high-energy lasers for inertial confinement fusion research, etc. [3,4]. The characteristic limitation .... pound [10]. The existence of KBr causes disorder in crystal lattice and this disorder leads to changes in lattice parameter and optical properties nonlinearly [11]. 3.4 FTIR analysis.

  20. Defects of diamond single crystal grown under high temperature and high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Su, Qingcai, E-mail: suqc@sdu.edu.cn [Key Laboratory of Liquid Structure and Heredity of Materials (Ministry of Education), Shandong University, Jinan, P. R. China, 250061 (China); School of Materials Science and Engineering, Shandong University, Jinan, P. R. China, 250061 (China); Shandong Engineering Research Center for Superhard Materials, Zoucheng, P. R. China 273500 (China); Zhang, Jianhua [School of Mechanical Engineering, Shandong University, Jinan, P. R. China, 250061 (China); Li, Musen [Key Laboratory of Liquid Structure and Heredity of Materials (Ministry of Education), Shandong University, Jinan, P. R. China, 250061 (China); School of Materials Science and Engineering, Shandong University, Jinan, P. R. China, 250061 (China); Shandong Engineering Research Center for Superhard Materials, Zoucheng, P. R. China 273500 (China)

    2013-11-01

    The diamond single crystal, synthesized with Fe–Ni–C–B system of catalyst under high temperature and high pressure, had been observed by field emission scanning electron microscope and transmission electron microscope. The presence of a cellular structure suggested that the diamond grew from melted catalyst solution and there existed a zone of component supercooling zone in front of the solid–liquid interface. The main impurities in the diamond crystal was (FeNi){sub 23}C{sub 6}. The triangle screw pit revealed on the (111) plane was generated by the screw dislocation meeting the diamond (111) plane at the points of emergence of dislocations. A narrow twin plane was formed between the two (111) plane. - Highlights: • High pressure, high temperature synthesis of diamond single crystal. • Fe–Ni–C–B used as catalyst, graphite as carbon source. • The main impurity in the diamond crystal was (FeNi){sub 23}C{sub 6}. • Surface defects arose from screw dislocations and stacking faults.

  1. Surface studies on as-grown (111) faces of sodium bromate crystals

    Indian Academy of Sciences (India)

    Unknown

    facilitates to etch almost at the selective position. It consists of a small tube with pointed tip, after filling with ... the selective position by turning the socket. By pressing the tube gently the etchant is released drop by ... In the present study attention has also been focused to study the inclusions in the sodium bromate crystals. In.

  2. Optical and electrical properties of ZrSe3 single crystals grown by ...

    Indian Academy of Sciences (India)

    Unknown

    chalcogen atoms surround each metal atom forming dis- torted trigonal prisms. The crystal growth in the ... atomic distances, holds promise in the investigation of these materials to identify the novel properties and .... due to the localization of the electron states because of the presence of stacking faults. This will therefore ...

  3. 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

  4. Self-organized single crystal mixed magnetite/cobalt ferrite films grown by infrared pulsed-laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química Física “Rocasolano”, CSIC, Madrid E-28006 (Spain); Quesada, Adrián [Instituto de Cerámica y Vidrio, CSIC, Madrid E-28049 (Spain); Martín-García, Laura; Sanz, Mikel; Oujja, Mohamed; Rebollar, Esther; Castillejo, Marta [Instituto de Química Física “Rocasolano”, CSIC, Madrid E-28006 (Spain); Prieto, Pilar; Muñoz-Martín, Ángel [Universidad Autónoma de Madrid, E-28049 (Spain); Aballe, Lucía [Alba Synchrotron Light Facility, CELLS, Barcelona (Spain); Marco, José F. [Instituto de Química Física “Rocasolano”, CSIC, Madrid E-28006 (Spain)

    2015-12-30

    Highlights: • Infrared pulsed deposition is used to grow single crystal mixed magnetite-cobalt ferrite films. • Distinct topography with two mound types on the surface of the film. • Suggested origin of segregation into two phases is oxygen deficiency during growth. • Mössbauer is required to quantify the two components. - Abstract: We have grown mixed magnetite/cobalt ferrite epitaxial films on SrTiO{sub 3} by infrared pulsed-laser deposition. Diffraction experiments indicate epitaxial growth with a relaxed lattice spacing. The films are flat with two distinct island types: nanometric rectangular mounds in two perpendicular orientations, and larger square islands, attributed to the two main components of the film as determined by Mössbauer spectroscopy. The origin of the segregation is suggested to be the oxygen-deficiency during growth.

  5. Crystal orientations of InSb films grown on a Si(111) substrate by inserting AlSb buffer layer

    International Nuclear Information System (INIS)

    Murata, K.; Ahmad, N.B.; Mori, M.; Tambo, T.; Maezawa, K.

    2008-01-01

    The heteroepitaxial growth of InSb film via AlSb buffer layer on a Si(111) substrate was performed in an ultra high vacuum. The grown InSb films were characterized by X-ray diffraction and atomic force microscopy. XRD patterns (Φ-scan) of the samples showed different epitaxial relationship between InSb/Si and InSb/AlSb/Si. It is found that surface condition has a significant influence on the growth of InSb films and the surface of InSb films became rough due to the high mixture ratio of domains. The two-step growth procedure was also tried to further improve the crystal quality of the InSb films. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Radiation stability of protein crystals grown by nanostructured templates: synchrotron microfocus analysis

    International Nuclear Information System (INIS)

    Pechkova, Eugenia; Tropiano, Giuseppe; Riekel, Christian; Nicolini, Claudio

    2004-01-01

    X-ray radiation damage of lysozyme single crystals by an intense monochromatic beam from a focussed third-generation synchrotron radiation source has been studied. The preliminary results show a significantly higher resistance to synchrotron radiation of lysozyme microcrystals produced by means of nanotechnology-based template with respect to those prepared by classical methodology. The implications of this finding for protein crystallography are discussed

  7. EXAFS investigations on PbMoO4 single crystals grown under ...

    Indian Academy of Sciences (India)

    priately setting the Bragg angle and the radius of curvature of the crystal bender. The absorption edges of 99·99% pure. PbO and Bi2O3 samples were recorded at the same experi- mental setting to calibrate CCD channels in terms of energy. As can be seen from figure 1, the absorption edges of Pb and. Bi in these samples ...

  8. Growth rate anisotropy and absorption studies on β-BaB 2O 4 single crystals grown by the top-seeded solution growth technique

    Science.gov (United States)

    Bhatt, Rajeev; Ganesamoorthy, S.; Bhaumik, Indranil; Karnal, A. K.; Wadhawan, V. K.

    2007-03-01

    Beta barium borate (β-BaB2O4; BBO) single crystals have been grown from Na2O flux by the TSSG technique and the observed growth rate anisotropy is reported. The symmetrical conoscopic interference pattern on the c-cut plate confirmed strain-free and optical homogeneity of the crystals. The observed growth habits of as-grown crystals are explained using crystal growth theories. The relative growth rate along different crystallographic directions of BBO can be described by R[100] = R[010] > R[001]. The absorption measurements show a nearly 9 nm shift in fundamental absorption edges in X and Z cut samples. Band gap energies measured were 6.45 and 6.2 eV along the X and Z directions, respectively. The absorption spectra near the fundamental absorption edges (AE) follow Urbach's rule.

  9. 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.

  10. crystal

    Science.gov (United States)

    Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Sun, Shijia; Wang, Guofu

    2014-07-01

    A Nd3+:Na2La4(WO4)7 crystal with dimensions of ϕ 17 × 30 mm3 was grown by the Czochralski method. The thermal expansion coefficients of Nd3+:Na2La4(WO4)7 crystal are 1.32 × 10-5 K-1 along c-axis and 1.23 × 10-5 K-1 along a-axis, respectively. The spectroscopic characteristics of Nd3+:Na2La4(WO4)7 crystal were investigated. The Judd-Ofelt theory was applied to calculate the spectral parameters. The absorption cross sections at 805 nm are 2.17 × 10-20 cm2 with a full width at half maximum (FWHM) of 15 nm for π-polarization, and 2.29 × 10-20 cm2 with a FWHM of 14 nm for σ-polarization. The emission cross sections are 3.19 × 10-20 cm2 for σ-polarization and 2.67 × 10-20 cm2 for π-polarization at 1,064 nm. The fluorescence quantum efficiency is 67 %. The quasi-cw laser of Nd3+:Na2La4(WO4)7 crystal was performed. The maximum output power is 80 mW. The slope efficiency is 7.12 %. The results suggest Nd3+:Na2La4(WO4)7 crystal as a promising laser crystal fit for laser diode pumping.

  11. 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

  12. Growth and luminescent properties of the Ce, Pr doped NaCl single crystals grown by the modified micro-pulling-down method

    Energy Technology Data Exchange (ETDEWEB)

    Yokota, Yuui, E-mail: y-yokota@tagen.tohoku.ac.j [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University/2-1-1, Katahira, Aoba-ku, Sendai (Japan); Yanagida, Takayuki; Fujimoto, Yutaka [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University/2-1-1, Katahira, Aoba-ku, Sendai (Japan); Nikl, Martin [Institute of Physics, Academy of Sciences of the Czech Republic/6253, Prague (Czech Republic); Yoshikawa, Akira [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University/2-1-1, Katahira, Aoba-ku, Sendai (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University/2-1-1, Katahira, Aoba-ku, Sendai (Japan)

    2010-03-15

    We have investigated luminescent properties of nondope, Ce and Pr doped NaCl [nondope NaCl, Ce:NaCl, Pr:NaCl] single crystals grown by a modified micro-pulling-down method with a removable chamber system. Nondope, Ce 1% and Pr 1% doped NaCl crystals with a single phase of NaCl structure were obtained and the crystals indicated general crystal quality by the X-ray rocking curve measurement. For the nondope NaCl and Pr:NaCl crystals, the transmittance spectra indicated almost more than 60% in the wavelength from 200 to 800 nm and an absorption of Ce{sup 3+} ion was observed in the transmittance spectrum of Ce:NaCl crystal. The emission spectrum originated from Ce{sup 3+} 5d-4f transition appeared around 300 nm in the photoluminescence spectrum and the decay time was 19.7 ns.

  13. Growth and luminescent properties of the Ce, Pr doped NaCl single crystals grown by the modified micro-pulling-down method

    International Nuclear Information System (INIS)

    Yokota, Yuui; Yanagida, Takayuki; Fujimoto, Yutaka; Nikl, Martin; Yoshikawa, Akira

    2010-01-01

    We have investigated luminescent properties of nondope, Ce and Pr doped NaCl [nondope NaCl, Ce:NaCl, Pr:NaCl] single crystals grown by a modified micro-pulling-down method with a removable chamber system. Nondope, Ce 1% and Pr 1% doped NaCl crystals with a single phase of NaCl structure were obtained and the crystals indicated general crystal quality by the X-ray rocking curve measurement. For the nondope NaCl and Pr:NaCl crystals, the transmittance spectra indicated almost more than 60% in the wavelength from 200 to 800 nm and an absorption of Ce 3+ ion was observed in the transmittance spectrum of Ce:NaCl crystal. The emission spectrum originated from Ce 3+ 5d-4f transition appeared around 300 nm in the photoluminescence spectrum and the decay time was 19.7 ns.

  14. N and Si Implantation Effect on Structural and Electrical Properties of Bridgman grown GaSe Single Crystal

    International Nuclear Information System (INIS)

    Karabulut, O.

    2004-01-01

    N and Si implantation to GaSe single crystals were carried out parallel to c-axis with ion beam of about 10 1 6 ions/cm 2 dose having energy values 30, 60 and 100 keV. Ion implantation modifications on Bridgman grown GaSe single crystals have been investigated by means of XRD, electrical conductivity, absorption and photoconductivity measurements. XRD measurements revealed that annealing results in a complete recovery of the crystalline nature that was moderately reduced upon implantation. It was observed that both N- and Siimplantation followed by annealing process decreased the resistivity values from 10 7 to 10 3 .-cm. The analysis of temperature dependent conductivity showed that at high temperature region above 200 K, the transport mechanism is dominated by thermal excitation in the doped and undoped GaSe samples. At lower temperatures, the conduction of carriers is dominated by variable range hopping mechanism in the implanted samples. Absorption and spectral photoconductivity measurements showed that the band edge is shifted in the implanted sample. All these modifications were attributed to the structural modifications and continuous shallow trap levels introduced upon implantation and annealing

  15. Experiments in microgravity: a comparison of crystals of a carbohydrate-binding fab grown on the ground, on space shuttle Discovery and on space station Mir.

    Science.gov (United States)

    Borisova, S N; Birnbaum, G I; Rose, D R; Evans, S V

    1996-03-01

    The Fab fragment of the hybridoma antibody (YsT9.1) specific to Brucella abortus has been crystallized on earth using both Linbro plates and ground-based models of the flight hardware, as well as in microgravity on board the space shuttle Discovery and the space station Mir. Large-scale experiments using Linbro plates gave two different crystal morphologies, pyramidal and rhomboid, depending on conditions. The pyramidal crystals proved to scatter X-rays to higher resolution, and conditions within the ground-based flight hardware for both Discovery and Mir were adjusted to produce crystals with this morphology. The experiment on Discovery produced large crystals in each of ten chambers. The experiment on Mir produced crystals in only one of the five assigned chambers, despite the fact that the simultaneous ground-based experiment produced large crystals in every corresponding chamber. Data collection was attempted for crystals from both space and ground-based experiments. Higher resolution data was obtained from crystals grown on Discovery than from either Mir or ground-based crystals, even though the crystals obtained from Discovery were smaller and forced to grow over a much shorter period of time because of the shorter length of the shuttle mission.

  16. 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.

  17. Investigation of SR method grown <0 0 1> directed KDP single crystal and its characterization by high-resolution X-ray diffractometry (HRXRD), laser damage threshold, dielectric, thermal analysis, optical and hardness studies

    Energy Technology Data Exchange (ETDEWEB)

    Balamurugan, S. [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam, Chennai 603 110 (India); Ramasamy, P., E-mail: ramasamyp@ssn.edu.in [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam, Chennai 603 110 (India); Sharma, S.K. [LMDDD, RRCAT, Indore (India); Inkong, Yutthapong; Manyum, Prapun [School of Physics, Institute of Science, Suranaree University of Technology (Thailand)

    2009-10-15

    <0 0 1> directed potassium dihydrogen orthophosphate (KDP) single crystal was grown by Sankaranarayanan-Ramasamy (SR) method. The <0 0 1> oriented seed crystals were mounted at the bottom of the platform and the size of the crystals were 10 mm diameter, 110 mm height. Two different growths were tried, in one the crystal diameter was the ampoule's inner diameter and in the other the crystal thickness was less than the ampoule diameter. In the first case only the top four pyramidal faces were existing whereas in the second case the top four pyramidal faces and four prismatic faces were existing through out the growth. The crystals were grown using same stoichiometric solution. The results of the two growths are discussed in this paper. The grown crystals were characterized by high-resolution X-ray diffractometry (HRXRD), laser damage threshold, dielectric, thermal analysis, UV-vis spectroscopy and microhardness studies. The HRXRD analysis indicates that the crystalline perfection is excellent without having any very low angle internal structural grain boundaries. Laser damage threshold value has been determined using Nd:glass laser operating at 1054 nm. The damage threshold for the KDP crystal is greater than 4.55 GW cm{sup -2}. The dielectric constant was higher and the dielectric loss was less in SR method grown crystal as against conventional method grown crystal. In thermal analysis, the starting of decomposition nature is similar in SR method grown KDP crystal and conventional method grown crystal. The SR method grown KDP has higher transmittance and higher hardness value compared to conventional method grown crystals.

  18. Luminescence characteristics of the LPE-grown undoped and In-doped ZnO thin films and bulk single crystals

    Czech Academy of Sciences Publication Activity Database

    Pejchal, Jan; Kagamitani, Y.; Ehrentraut, D.; Sato, H.; Odaka, H.; Hatanaka, H.; Nikl, Martin; Yoshikawa, A.; Fukumura, H.; Fukuda, T.

    2007-01-01

    Roč. 4, č. 3 (2007), s. 942-945 ISSN 1862-6351 R&D Projects: GA MŠk ME 871 Grant - others:NEDO(JP) 03A26014a Institutional research plan: CEZ:AV0Z10100521 Keywords : luminescence * LPE-grown undoped * bulk single crystals Subject RIV: BM - Solid Matter Physics ; Magnetism

  19. Growth and Characterization of (211)B Cadmium Telluride Buffer Layer Grown by Metal-organic Vapor Phase Epitaxy on Nanopatterned Silicon for Mercury Cadmium Telluride Based Infrared Detector Applications

    Science.gov (United States)

    Shintri, Shashidhar S.

    Mercury cadmium telluride (MCT or Hg1-xCdxTe) grown by molecular beam epitaxy (MBE) is presently the material of choice for fabricating infrared (IR) detectors used in night vision based military applications. The focus of MCT epitaxy has gradually shifted since the last decade to using Si as the starting substrate since it offers several advantages. But the ˜19 % lattice mismatch between MCT and Si generates lots of crystal defects some of which degrade the performance of MCT devices. Hence thick CdTe films are used as buffer layers on Si to accommodate the defects. However, growth of high quality single crystal CdTe on Si is challenging and to date, the best MBE CdTe/Si reportedly has defects in the mid-105 cm -2 range. There is a critical need to reduce the defect levels by at least another order of magnitude, which is the main motivation behind the present work. The use of alternate growth technique called metal-organic vapor phase epitaxy (MOVPE) offers some advantages over MBE and in this work MOVPE has been employed to grow the various epitaxial films. In the first part of this work, conditions for obtaining high quality (211)B CdTe epitaxy on (211)Si were achieved, which also involved studying the effect of having additional intermediate buffer layers such as Ge and ZnTe and incorporation of in-situ thermal cyclic annealing (TCA) to reduce the dislocation density. A critical problem of Si cross-contamination due to 'memory effect' of different reactant species was minimized by introducing tertiarybutylArsine (TBAs) which resulted in As-passivation of (211)Si. The best 8-10 µm thick CdTe films on blanket (non-patterned) Si had dislocations around 3×105 cm-2, which are the best reported by MOVPE till date and comparable to the highest quality films available by MBE. In the second part of the work, nanopatterned (211)Si was used to study the effect of patterning on the crystal quality of epitaxial CdTe. In one such study, patterning of ˜20 nm holes in SiO2

  20. 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.

  1. 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.

  2. Growth of CdTe on Si(100) surface by ionized cluster beam technique: Experimental and molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Araghi, Houshang, E-mail: araghi@aut.ac.ir [Department of Physics, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Zabihi, Zabiholah [Department of Physics, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Nayebi, Payman [Department of Physics, College of Technical and Engineering, Saveh Branch, Islamic Azad University, Saveh (Iran, Islamic Republic of); Ehsani, Mohammad Mahdi [Department of Physics, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of)

    2016-10-15

    II–VI semiconductor CdTe was grown on the Si(100) substrate surface by the ionized cluster beam (ICB) technique. In the ICB method, when vapors of solid materials such as CdTe were ejected through a nozzle of a heated crucible into a vacuum region, nanoclusters were created by an adiabatic expansion phenomenon. The clusters thus obtained were partially ionized by electron bombardment and then accelerated onto the silicon substrate at 473 K by high potentials. The cluster size was determined using a retarding field energy analyzer. The results of X-ray diffraction measurements indicate the cubic zinc blende (ZB) crystalline structure of the CdTe thin film on the silicon substrate. The CdTe thin film prepared by the ICB method had high crystalline quality. The microscopic processes involved in the ICB deposition technique, such as impact and coalescence processes, have been studied in detail by molecular dynamics (MD) simulation.

  3. Characterization of the α-SN/CDTE(110) interface by angle-resolved X-ray photoemission

    International Nuclear Information System (INIS)

    Lin, T.S.; Partin, W.J.; Chung, Y.W.

    1987-01-01

    Stoichiometric and atomically clean CdTe(110) surfaces have been prepared by suitable chemical etching, followed by argon sputtering, and sample annealing in ultra-high vacuum. Cubic (α) -tin was grown on CdTe(110) by tin evaporation from a tungsten filament at a substrate temperature of 30 0 C. Angle-resolved X-ray photoelectron spectroscopy (ARXPS) was used to determine the α-Sn growth mechanism and the composition profile of this semiconductor heterostructure nondestructively. From their analyses, the authors conclude that α-Sn grows on CdTe(110) at 30 0 C by a layer by layer mechanism and forms an abrupt junction with CdTe(110)

  4. 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.

  5. Annealing and surface conduction on Hydrogen peroxide treated bulk melt-grown, single crystal ZnO

    International Nuclear Information System (INIS)

    Mtangi, W.; Nel, J.M.; Auret, F.D.; Chawanda, A.; Diale, M.; Nyamhere, C.

    2012-01-01

    We report on the studies carried out on hydrogen peroxide treated melt-grown, bulk single crystal ZnO samples. Results show the existence of two shallow donors in the as-received ZnO samples with energy levels (37.8±0.3) meV that has been suggested as Zn i related and possibly H-complex related and (54.5±0.9) meV, which has been assigned to an Al-related donor. Annealing studies performed on the hydrogen peroxide treated samples reveal the existence of a conductive channel in the samples in which new energy levels have been observed, Zn vacancies, related to the Group I elements, X Zn . The surface donor volume concentration of the conductive channel was calculated from a theory developed by Look (2007) . Results indicate an increase in the surface volume concentration with increasing annealing temperature from 60×10 17 cm −3 at 200 °C to 4.37×10 18 cm -3 at 800 °C.

  6. Annealing and surface conduction on Hydrogen peroxide treated bulk melt-grown, single crystal ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Mtangi, W., E-mail: wilbert.mtangi@up.ac.za [University of Pretoria, Physics Department, Pretoria 0002 (South Africa); Nel, J.M.; Auret, F.D.; Chawanda, A.; Diale, M. [University of Pretoria, Physics Department, Pretoria 0002 (South Africa); Nyamhere, C. [Nelson Mandela Metropolitan University, Physics Department, P.O. Box 77000, Port Elizabeth 6031 (South Africa)

    2012-05-15

    We report on the studies carried out on hydrogen peroxide treated melt-grown, bulk single crystal ZnO samples. Results show the existence of two shallow donors in the as-received ZnO samples with energy levels (37.8{+-}0.3) meV that has been suggested as Zn{sub i} related and possibly H-complex related and (54.5{+-}0.9) meV, which has been assigned to an Al-related donor. Annealing studies performed on the hydrogen peroxide treated samples reveal the existence of a conductive channel in the samples in which new energy levels have been observed, Zn vacancies, related to the Group I elements, X{sub Zn}. The surface donor volume concentration of the conductive channel was calculated from a theory developed by Look (2007) . Results indicate an increase in the surface volume concentration with increasing annealing temperature from 60 Multiplication-Sign 10{sup 17} cm{sup -3} at 200 Degree-Sign C to 4.37 Multiplication-Sign 10{sup 18} cm{sup -3} at 800 Degree-Sign C.

  7. Effect of crystal size on purity of uranyl nitrate hexahydrate crystalline particles grown in nitric acid medium (orig.)

    International Nuclear Information System (INIS)

    Nakahara, M.; Nomura, K.

    2012-01-01

    Crystal washing experiments were carried out using a uranyl nitrate solution in order to confirm the effect of uranyl nitrate hexahydrate (UNH) crystalline particle size on the removal of liquid impurities. The UNH crystal was immersed in a Ce solution and was washed for removing the mother liquor on the surface of the UNH crystals. Larger UNH crystals were advantageous for increasing the decontamination factors (DFs) of liquid impurities. The large crystal size reduced the specific surface area of the crystals which in turn decreased the adhesion of liquid impurities on the surface of the crystals. Therefore, high DFs of liquid impurities were achieved before and after washing. In the crystallization experiments, the DFs of metals for the UNH crystal were evaluated using a dissolver solution derived from irradiated fast neutron reactor core fuel. The UNH crystal size did not affect the decontamination of solid impurities such as Ba and Np even after crystal washing in the U crystallization experiments. (orig.)

  8. 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...

  9. Inclusions related to catalyst and medium for transmitting pressure in diamond single crystals grown at high temperature and high pressure from the Fe-C system

    International Nuclear Information System (INIS)

    Yin Longwei; Li Musen; Hao Zhaoyin; Zhang Jiongfa

    2001-01-01

    Inclusion entrapment in a crystal is one of the most important characteristics for the crystal growth technique from solution. Diamond single crystals grown from the Fe-C system at high temperature-high pressure usually contain inclusions related to the molten catalyst and the medium (pyrophyllite) for transmitting pressure. During the growth of the diamond, the inclusions are trapped by the growth front or are formed through reaction between the contaminants trapped in the diamond. In the present article, the inclusions related to the catalyst and pyrophyllite were systemically examined by transmission electron microscopy. The chemical composition and crystal structure of the inclusions were, for the first time, determined by selected area electron diffraction pattern combined with energy dispersive x-ray spectrometry. It was shown that the inclusions are mainly composed of orthorhombic Fe 3 C, orthorhombic FeSi 2 , hexagonal SiO 2 and face-centred cubic SiC. (author)

  10. Minimization of lattice parameter change in Czochralski grown (Gd sub 1-x Y sub x ) sub 3 Ga sub 5 O sub 12 garnet single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, Hideo; Numazawa, Takenori; Sato, Mitsunori; Maeda, Hiroshi (National Research Inst. for Metals, Ibaraki (Japan)); Sakamoto, Masaru (Nippon Mining Co. Ltd., Saitama (Japan))

    1992-05-01

    Single crystals of (Gd{sub 1-x}Y{sub x}){sub 3}Ga{sub 5}O{sub 12} rare-earth garnet solid solutions were grown by using the Czochralski technique and their lattice parameter change along the growth direction was minimized by means of the combination of a solid solution effect and a nonstoichiometry effect for the garnet. The single crystals are promising magnetic refrigerants for magnetic refrigerators to generate a low temperature atmosphere below 1 K. (orig.).

  11. Anodically-grown TiO{sub 2} nanotubes: Effect of the crystallization on the catalytic activity toward the oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Sacco, Adriano, E-mail: adriano.sacco@iit.it [Center for Sustainable Future Technologies @Polito, Istituto Italiano di Tecnologia, Corso Trento 21, 10129, Torino (Italy); Garino, Nadia [Center for Sustainable Future Technologies @Polito, Istituto Italiano di Tecnologia, Corso Trento 21, 10129, Torino (Italy); Applied Science and Technology Department, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino (Italy); Lamberti, Andrea, E-mail: andrea.lamberti@polito.it [Center for Sustainable Future Technologies @Polito, Istituto Italiano di Tecnologia, Corso Trento 21, 10129, Torino (Italy); Applied Science and Technology Department, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino (Italy); Pirri, Candido Fabrizio [Center for Sustainable Future Technologies @Polito, Istituto Italiano di Tecnologia, Corso Trento 21, 10129, Torino (Italy); Applied Science and Technology Department, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino (Italy); Quaglio, Marzia [Center for Sustainable Future Technologies @Polito, Istituto Italiano di Tecnologia, Corso Trento 21, 10129, Torino (Italy)

    2017-08-01

    Highlights: • Anodically-grown TiO{sub 2} nanotubes as catalysts for the oxygen reduction reaction. • Amorphous NTs compared to thermal- and vapor-treated crystalline nanostructures. • The selection of the crystallization conditions leads to performance similar to Pt. - Abstract: In this work we investigated the behavior of TiO{sub 2} nanotube (NT) arrays, grown by anodic oxidation of Ti foil, as catalysts for the oxygen reduction reaction (ORR) in alkaline water solution. In particular, as-grown amorphous NTs were compared to crystalline anatase nanostructures, obtained following two different procedures, namely thermal and vapor-induced crystallizations. The catalytic activity of these materials toward the ORR was evaluated by cyclic voltammetry measurements. ORR polarization curves, combined with the rotating disk technique, indicated a predominant four-electrons reduction path, especially for crystalline samples. The effect of the structural characteristics of the investigated materials on the catalytic activity was analyzed in details by electrochemical impedance spectroscopy. The catalytic performance of the crystalline NTs is only slightly lower with respect to the reference material for fuel cell applications, namely platinum, but is in line with other cost-effective catalysts recently proposed in the literature. However, if compared to the larger part of these low-cost catalysts, anodically-grown TiO{sub 2} NTs are characterized by a synthesis route which is highly reproducible and easily up-scalable.

  12. Crystal orientation, crystallinity, and thermoelectric properties of Bi0.9Sr0.1CuSeO epitaxial films grown by pulsed laser deposition

    Science.gov (United States)

    Ishizawa, Mamoru; Fujishiro, Hiroyuki; Naito, Tomoyuki; Ito, Akihiko; Goto, Takashi

    2018-02-01

    We have grown Bi0.9Sr0.1CuSeO epitaxial thin films on MgO and SrTiO3 (STO) single-crystal substrates by pulsed laser deposition (PLD) under various growth conditions, and investigated the crystal orientation, crystallinity, chemical composition, and thermoelectric properties of the films. The optimization of the growth conditions was realized in the film grown on MgO at the temperature T s = 573 K and Ar pressure P Ar = 0.01 Torr in this study, in which there was no misalignment apart from the c-axis and no impurity phase. It was clearly found that the higher crystal orientation of the epitaxial film grown at a higher temperature under a lower Ar pressure mainly enhanced the thermoelectric power factor P (= S 2/ρ), where S is the Seebeck coefficient and ρ is the electrical resistivity. However, the thermoelectric properties of the films were lower than those of polycrystalline bulk because of lattice distortion from lattice mismatch, a low crystallinity caused by a lower T s, and Bi and Cu deficiencies in the films.

  13. 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.

  14. Crystallography, magnetic susceptibility, heat capacity, and electrical resistivity of heavy-fermion LiV2O4 single crystals grown using a self-flux technique

    Science.gov (United States)

    Das, S.; Zong, X.; Niazi, A.; Ellern, A.; Yan, J. Q.; Johnston, D. C.

    2007-08-01

    Magnetically pure spinel compound LiV2O4 is a rare d -electron heavy fermion. Measurements on single crystals are needed to clarify the mechanism for the heavy-fermion behavior in the pure material. In addition, it is known that small concentrations (<1mol%) of magnetic defects in the structure strongly affect the properties, and measurements on single crystals containing magnetic defects would help to understand the latter behaviors. Herein, we report flux growth of LiV2O4 and preliminary measurements to help resolve these questions. The magnetic susceptibility of some as-grown crystals show a Curie-like upturn at low temperatures, showing the presence of magnetic defects within the spinel structure. The magnetic defects could be removed in some of the crystals by annealing them at 700°C . A very high specific heat coefficient γ=450mJ/molK2 was obtained at a temperature of 1.8K for a crystal containing a magnetic defect concentration ndefect=0.5mol% . A crystal with ndefect=0.01mol% showed a residual resistivity ratio of 50.

  15. Comparison of Sn-doped and nonstoichiometric vertical-Bridgman-grown crystals of the topological insulator Bi{sub 2}Te{sub 2}Se

    Energy Technology Data Exchange (ETDEWEB)

    Kushwaha, S. K., E-mail: kushwaha@princeton.edu; Gibson, Q. D.; Cava, R. J. [Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States); Xiong, J.; Ong, N. P. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Pletikosic, I. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Condensed Matter Physics and Materials Science Department, Brookhaven National Lab, Upton, New York 11973 (United States); Weber, A. P. [National Synchrotron Light Source, Brookhaven National Lab, Upton, New York 11973 (United States); Fedorov, A. V. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Valla, T. [Condensed Matter Physics and Materials Science Department, Brookhaven National Lab, Upton, New York 11973 (United States)

    2014-04-14

    A comparative study of the properties of topological insulator Bi{sub 2}Te{sub 2}Se (BTS) crystals grown by the vertical Bridgeman method is described. Two defect mechanisms that create acceptor impurities to compensate for the native n-type carriers are compared: Bi excess, and light Sn doping. Both methods yield low carrier concentrations and an n-p crossover over the length of the grown crystal boules, but lower carrier concentrations and higher resistivities are obtained for the Sn-doped crystals, which reach carrier concentrations as low as 8 × 10{sup 14} cm{sup −3}. Further, the temperature dependent resistivities for the Sn-doped crystals display strongly activated behavior at high temperatures, with a characteristic energy of half the bulk band gap. The (001) cleaved Sn-doped BTS crystals display high quality Shubnikov de Haas (SdH) quantum oscillations due to the topological surface state electrons. Angle resolved photoelectron spectroscopy (ARPES) characterization shows that the Fermi energy (E{sub F}) for the Sn-doped crystals falls cleanly in the surface states with no interference from the bulk bands, which the Dirac point for the surface states lies approximately 60 meV below the top of the bulk valence band maximum, and allows for a determination of the bulk and surface state carrier concentrations as a function of Energy near E{sub F}. Electronic structure calculations that compare Bi excess and Sn dopants in BTS demonstrate that Sn acts as a special impurity, with a localized impurity band that acts as a charge buffer occurring inside the bulk band gap. We propose that the special resonant level character of Sn in BTS gives rise to the exceptionally low carrier concentrations and activated resistivities observed.

  16. 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

  17. Structural Characterization of Lateral-grown 6H-SiC am-plane Seed Crystals by Hot Wall CVD Epitaxy

    Science.gov (United States)

    Goue, Ouloide Yannick; Raghothamachar, Balaji; Dudley, Michael; Trunek, Andrew J.; Neudeck, Philip G.; Woodworth, Andrew A.; Spry, David J.

    2014-01-01

    The performance of commercially available silicon carbide (SiC) power devices is limited due to inherently high density of screw dislocations (SD), which are necessary for maintaining polytype during boule growth and commercially viable growth rates. The NASA Glenn Research Center (GRC) has recently proposed a new bulk growth process based on axial fiber growth (parallel to the c-axis) followed by lateral expansion (perpendicular to the c-axis) for producing multi-faceted m-plane SiC boules that can potentially produce wafers with as few as one SD per wafer. In order to implement this novel growth technique, the lateral homoepitaxial growth expansion of a SiC fiber without introducing a significant number of additional defects is critical. Lateral expansion is being investigated by hot wall chemical vapor deposition (HWCVD) growth of 6H-SiC am-plane seed crystals (0.8mm x 0.5mm x 15mm) designed to replicate axially grown SiC single crystal fibers. The post-growth crystals exhibit hexagonal morphology with approximately 1500 m (1.5 mm) of total lateral expansion. Preliminary analysis by synchrotron white beam x-ray topography (SWBXT) confirms that the growth was homoepitaxial, matching the polytype of the respective underlying region of the seed crystal. Axial and transverse sections from the as grown crystal samples were characterized in detail by a combination of SWBXT, transmission electron microscopy (TEM) and Raman spectroscopy to map defect types and distribution. X-ray diffraction analysis indicates the seed crystal contained stacking disorders and this appears to have been reproduced in the lateral growth sections. Analysis of the relative intensity for folded transverse acoustic (FTA) and optical (FTO) modes on the Raman spectra indicate the existence of stacking faults. Further, the density of stacking faults is higher in the seed than in the grown crystal. Bundles of dislocations are observed propagating from the seed in m-axis lateral directions

  18. Structural and magnetoelectric properties of Ga2-xFexO3 single crystals grown by a floating-zone method

    International Nuclear Information System (INIS)

    Arima, T.; Higashiyama, D.; Goto, T.; Miyasaka, S.; Kimura, T.; Kaneko, Y.; He, J.P.; Oikawa, K.; Kamiyama, T.; Kumai, R.; Tokura, Y.

    2004-01-01

    Lattice-structural, magnetic, and magnetoelectric (ME) properties have been investigated for single crystals of prototypical polar ferrimagnet Ga 2-x Fe x O 3 (0.8≤x≤1.4) as melt-grown by a floating-zone (FZ) method. Magnetization measurements show that the saturated magnetization as well as the ferrimagnetic phase transition temperature (T C ) increases with as increase of Fe content x, while the coercive force decreases. A neutron powder diffraction study indicates fairly low ordering of Ga and Fe arrangement at cation sites, which is likely related to the lower T C in the FZ crystals than in the corresponding flux-grown crystals. Coefficients of linear and quadratic ME effects have been obtained with measurements of change in electric polarization induced by sweeping a magnetic field. Electric polarization was largely modulated in a magnetic field applied parallel to the direction of spontaneous magnetization, but not in a field parallel to that of the spontaneous polarization. A simple model to explain the sharp contrast is presented

  19. 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

  20. CDTE alloys and their application for increasing solar cell performance

    Science.gov (United States)

    Swanson, Drew E.

    Cadmium Telluride (CdTe) thin film solar is the largest manufactured solar cell technology in the United States and is responsible for one of the lowest costs of utility scale solar electricity at a purchase agreement of $0.0387/kWh. However, this cost could be further reduced by increasing the cell efficiency. To bridge the gap between the high efficiency technology and low cost manufacturing, a research and development tool and process was built and tested. This fully automated single vacuum PV manufacturing tool utilizes multiple inline close space sublimation (CSS) sources with automated substrate control. This maintains the proven scalability of the CSS technology and CSS source design but with the added versatility of independent substrate motion. This combination of a scalable deposition technology with increased cell fabrication flexibility has allowed for high efficiency cells to be manufactured and studied. The record efficiency of CdTe solar cells is lower than fundamental limitations due to a significant deficit in voltage. It has been modeled that there are two potential methods of decreasing this voltage deficiency. The first method is the incorporation of a high band gap film at the back contact to induce a conduction-band barrier that can reduce recombination by reflecting electrons from the back surface. The addition of a Cd1-x MgxTe (CMT) layer at the back of a CdTe solar cell should induce this desired offset and reflect both photoelectrons and forward-current electrons away from the rear surface. Higher collection of photoelectrons will increase the cells current and the reduction of forward current will increase the cells voltage. To have the optimal effect, CdTe must have reasonable carrier lifetimes and be fully depleted. To achieve this experimentally, CdTe layers have been grown sufficiently thin to help produce a fully depleted cell. A variety of measurements including performance curves, transmission electron microscopy, x

  1. Harvesting and cryo-cooling crystals of membrane proteins grown in lipidic mesophases for structure determination by macromolecular crystallography.

    Science.gov (United States)

    Li, Dianfan; Boland, Coilín; Aragao, David; Walsh, Kilian; Caffrey, Martin

    2012-09-02

    An important route to understanding how proteins function at a mechanistic level is to have the structure of the target protein available, ideally at atomic resolution. Presently, there is only one way to capture such information as applied to integral membrane proteins (Figure 1), and the complexes they form, and that method is macromolecular X-ray crystallography (MX). To do MX diffraction quality crystals are needed which, in the case of membrane proteins, do not form readily. A method for crystallizing membrane proteins that involves the use of lipidic mesophases, specifically the cubic and sponge phases(1-5), has gained considerable attention of late due to the successes it has had in the G protein-coupled receptor field(6-21) (www.mpdb.tcd.ie). However, the method, henceforth referred to as the in meso or lipidic cubic phase method, comes with its own technical challenges. These arise, in part, due to the generally viscous and sticky nature of the lipidic mesophase in which the crystals, which are often micro-crystals, grow. Manipulating crystals becomes difficult as a result and particularly so during harvesting(22,23). Problems arise too at the step that precedes harvesting which requires that the glass sandwich plates in which the crystals grow (Figure 2)(24,25) are opened to expose the mesophase bolus, and the crystals therein, for harvesting, cryo-cooling and eventual X-ray diffraction data collection. The cubic and sponge mesophase variants (Figure 3) from which crystals must be harvested have profoundly different rheologies(4,26). The cubic phase is viscous and sticky akin to a thick toothpaste. By contrast, the sponge phase is more fluid with a distinct tendency to flow. Accordingly, different approaches for opening crystallization wells containing crystals growing in the cubic and the sponge phase are called for as indeed different methods are required for harvesting crystals from the two mesophase types. Protocols for doing just that have been

  2. High pressure effect on MoS2 and MoSe2 single crystals grown by ...

    Indian Academy of Sciences (India)

    Unknown

    tetrahedral anvil apparatus up to 5 GPa. In this paper we report room temperature resistance mea- surements as a function of pressure on MoS2 and MoSe2 single crystals. In each case the resistance decreases un- der pressure due to an increase in the carrier concentration. 2. Experimental. Single crystals of MoS2 and ...

  3. X-ray Topographic Investigations of Domain Structure in Czochralski Grown PrxLa1-xAlO3 Crystals

    International Nuclear Information System (INIS)

    Wieteska, K.; Wierzchowski, W.; Malinowska, A.; Turczynski, S.; Pawlak, D.A.; Lukasiewicz, T.; Lefeld-Sosnowska, M.; Graeff, W.

    2010-01-01

    In the present paper X-ray diffraction topographic techniques were applied to a number of samples cut from Czochralski grown Pr x La 1-x AlO 3 crystals with different ratio of praseodymium and lanthanum. Conventional and synchrotron X-ray topographic investigations revealed differently developed domain structures dependent on the composition of mixed praseodymium lanthanum aluminium perovskites. Some large mosaic blocks were observed together with the domains. In the best crystals, X-ray topographs revealed striation fringes and individual dislocations inside large domains. Synchrotron topographs allowed us to indicate that the domains correspond to three different crystallographic planes, and to evaluate the lattice misorientation between domains in the range of 20-50 arc min (authors)

  4. Effects of glass elements on the structural evolution of in situ grown ferroelectric perovskite crystals in sol-gel derived glass-ceramics

    International Nuclear Information System (INIS)

    Yao, K.; Zhu, W.

    1997-01-01

    Several ABO 3 perovskite ferroelectric crystals, PbTiO 3 , Pb(Zr,Ti)O 3 , and BaTiO 3 have been in situ grown from amorphous gels with glass elements, and the structural evolution has been systematically investigated using x-ray diffraction (XRD), infrared spectra (IR), differential thermal analysis (DTA), thermogravimetric analysis (TGA), and dielectric measurements. It is found that in the Si-contained glass-ceramic systems, Si and B glass elements are incorporated into the crystalline structures, resulting in the variation of the crystallization process, change of lattice constant, and dielectric properties. Some metastable phases expressed by a general formula A x B y G z O w (A=Pb and Ba; B=Zr and Ti; G for glass elements, especially for Si) have been observed and discussed. copyright 1997 Materials Research Society

  5. Fabrication of radiation detector using PbI2 crystals

    International Nuclear Information System (INIS)

    Shoji, T.; Ohba, K.; Suehiro, T.; Hiratate, Y.

    1995-01-01

    Radiation detectors have been fabricated from lead iodide (PbI 2 ) crystals grown by two methods: zone melting and Bridgman methods. In response characteristics of the detector fabricated from crystals grown by the zone melting method, a photopeak for γ-rays from an 241 Am source (59.5 KeV) has been clearly observed with applied detector bias of 500 V at room temperature. The hole drift mobility is estimated to be about 5.5 cm 2 /Vs from measurement of pulse rise time for 5.48 MeV α-rays from 241 Am. By comparing the detector bias versus saturated peak position of the PbI 2 detector with that of CdTe detector, the average energy for producing electron-hole pairs is estimated to be about 8.4 eV for the PbI 2 crystal. A radiation detector fabricated from PbI 2 crystals grown by the Bridgman method, however, exhibited no response for γ-rays

  6. Luminescent properties of Cr-doped gallium garnet crystals grown by the micro-pulling-down method

    Czech Academy of Sciences Publication Activity Database

    Kurosawa, S.; Suzuki, A.; Yamaji, A.; Kamada, K.; Pejchal, Jan; Ohashi, Y.; Yokota, Y.; Chani, V.I.; Yoshikawa, A.

    2016-01-01

    Roč. 452, Oct (2016), s. 95-100 ISSN 0022-0248. [American Conference on Crystal Growth and Epitaxy /20./ (ACCGE) / 17th Biennial Workshop on Organometallic Vapor Phase Epitaxy (OMVPE) / 2nd 2D Electronic Materials Symposium. Big Sky, MT, 02.08.2015-07.08.2015] Institutional support: RVO:68378271 Keywords : scintillator materials * single crystal growth * gallium compounds Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.751, year: 2016

  7. Structural and magnetic ordering of CrNb3S6 single crystals grown by gas transport method

    Science.gov (United States)

    Borisenko, E. B.; Berezin, V. A.; Kolesnikov, N. N.; Gartman, V. K.; Matveev, D. V.; Shakhlevich, O. F.

    2017-07-01

    Paramagnetic layered semiconductor NbS2 doped with some transition metals can transform into ferromagnetic material. That is why such materials are promising candidates for spintronic devices. It is found that only at certain concentrations of a doping metal T crystallographic ordering is possible, which is essential for magnetic ordering of ternary compounds TNbS2. In particular, CrNb3S6 crystals are studied, which form almost completely ordered superstructure with intercalated Cr between NbS2 layers. The main difficulty in crystal growth is reaching stoichiometry of the compound. This problem is solved in the developed method of two-staged gas transport chemical reaction. This new approach provides growth of CrNb3S6 single crystals of several millimeters in diameter and 0.3-0.5 mm thickness. X-ray phase analysis (XRD) of powders is performed to identify all phases involved in synthesis and growth of the crystals. High frequency absorption in external periodic magnetic field as a function of temperature and intensity of magnetic field is used to estimate the temperature of ferromagnetic transition in CrNb3S6 single crystals. The Curie temperature is estimated as 115 K. Growth of CrNb3S6 crystals from vapor phase is studied in detail and full analysis of phase transitions during growth is given. It has been shown that using of high frequency absorption in the crystal provides reliable estimation of the point of ferromagnetic transition in this semiconductor. The authors are grateful to the Physical Science Department of Russian Academy of Sciences for financial support of the studies in the frameworks of the program "Physics of new materials and structures" (project no. 00-12-10).

  8. Process design and simulation for optimizing the oxygen concentration in Czochralski-grown single-crystal silicon

    International Nuclear Information System (INIS)

    Jung, Y. J.; Kim, W. K.; Jung, J. H.

    2014-01-01

    The highest-concentration impurity in a single-crystal silicon ingot is oxygen, which infiltrates the ingot during growth stage. This oxygen adversely affects the wafer is quality. This study was aimed at finding an optimal design for the Czochralski (Cz) process to enable high-quality and low cost (by reducing power consumption) wafer production by controlling the oxygen concentration in the silicon ingots. In the Cz process, the characteristics of silicon ingots during crystallization are greatly influenced by the design and the configuration of the hot zone, and by crystallization rate. In order to identify process conditions for obtaining an optimal oxygen concentration of 11 - 13 ppma (required for industrial-grade ingots), designed two shield shapes for the hot zone. Furthermore, oxygen concentrations corresponding to these two shapes were compared by evaluating each shape at five different production speeds. In addition, simulations were performed to identify the optimal shield design for industrial applications.

  9. Process design and simulation for optimizing the oxygen concentration in Czochralski-grown single-crystal silicon

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Y. J.; Kim, W. K.; Jung, J. H. [Yeungnam University, Gyeongsan (Korea, Republic of)

    2014-08-15

    The highest-concentration impurity in a single-crystal silicon ingot is oxygen, which infiltrates the ingot during growth stage. This oxygen adversely affects the wafer is quality. This study was aimed at finding an optimal design for the Czochralski (Cz) process to enable high-quality and low cost (by reducing power consumption) wafer production by controlling the oxygen concentration in the silicon ingots. In the Cz process, the characteristics of silicon ingots during crystallization are greatly influenced by the design and the configuration of the hot zone, and by crystallization rate. In order to identify process conditions for obtaining an optimal oxygen concentration of 11 - 13 ppma (required for industrial-grade ingots), designed two shield shapes for the hot zone. Furthermore, oxygen concentrations corresponding to these two shapes were compared by evaluating each shape at five different production speeds. In addition, simulations were performed to identify the optimal shield design for industrial applications.

  10. Strain relaxation in single crystal SrTiO3 grown on Si (001) by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Choi, Miri; Posadas, Agham; Dargis, Rytis; Shih, Chih-Kang; Demkov, Alexander A.; Triyoso, Dina H.; David Theodore, N.; Dubourdieu, Catherine; Bruley, John; Jordan-Sweet, Jean

    2012-01-01

    An epitaxial layer of SrTiO 3 grown directly on Si may be used as a pseudo-substrate for the integration of perovskite oxides onto silicon. When SrTiO 3 is initially grown on Si (001), it is nominally compressively strained. However, by subsequent annealing in oxygen at elevated temperature, an SiO x interlayer can be formed which alters the strain state of SrTiO 3 . We report a study of strain relaxation in SrTiO 3 films grown on Si by molecular beam epitaxy as a function of annealing time and oxygen partial pressure. Using a combination of x-ray diffraction, reflection high energy electron diffraction, and transmission electron microscopy, we describe the process of interfacial oxidation and strain relaxation of SrTiO 3 on Si (001). Understanding the process of strain relaxation of SrTiO 3 on silicon will be useful for controlling the SrTiO 3 lattice constant for lattice matching with functional oxide overlayers.

  11. Structural, electrical, and optical properties of polycrystalline NbO{sub 2} thin films grown on glass substrates by solid phase crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Nakao, Shoichiro [Kanagawa Academy of Science and Technology (KAST), Kawasaki (Japan); Kamisaka, Hideyuki [Department of Chemistry, The University of Tokyo (Japan); Hirose, Yasushi; Hasegawa, Tetsuya [Kanagawa Academy of Science and Technology (KAST), Kawasaki (Japan); Department of Chemistry, The University of Tokyo (Japan)

    2017-03-15

    We investigated the structural, electrical, and optical properties of polycrystalline NbO{sub 2} thin films on glass substrates. The NbO{sub 2} films were crystallized from amorphous precursor films grown by pulsed laser deposition at various oxygen partial pressures (P{sub O2}). The electrical and optical properties of the precursor films systematically changed with P{sub O2}, demonstrating that the oxygen content of the precursor films can be finely controlled with P{sub O2}. The precursors were crystallized into polycrystalline NbO{sub 2} films by annealing under vacuum at 600 C. The NbO{sub 2} films possessed extremely flat surfaces with branching patterns. Even optimized films showed a low resistivity (ρ) of 2 x 10{sup 2} Ω cm, which is much lower than the bulk value of 1 x 10{sup 4} Ω cm, probably because of the inferior crystallinity of the films compared with that of a bulk NbO{sub 2} crystal. Both oxygen-rich and -poor NbO{sub 2} films showed lower ρ than that of the stoichiometric film. The NbO{sub 2} film with the highest ρ showed an indirect bandgap of 0.7 eV. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. 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.

  13. High pressure effect on MoS2 and MoSe2 single crystals grown by ...

    Indian Academy of Sciences (India)

    Unknown

    The variation of electrical resistance under pressure was monitored in a Bridgman anvil set-up up to 6⋅5 GPa to identify occurrence of any structural transition. MoS2 and MoSe2 do not undergo any structural transitions under pressure. Keywords. Single crystals; chemical vapour transport technique; high pressure. 1.

  14. Laser MBE-grown CoFeB epitaxial layers on MgO: Surface morphology, crystal structure, and magnetic properties

    Science.gov (United States)

    Kaveev, Andrey K.; Bursian, Viktor E.; Krichevtsov, Boris B.; Mashkov, Konstantin V.; Suturin, Sergey M.; Volkov, Mikhail P.; Tabuchi, Masao; Sokolov, Nikolai S.

    2018-01-01

    Epitaxial layers of CoFeB were grown on MgO by means of laser molecular beam epitaxy using C o40F e40B20 target. The growth was combined with in situ structural characterization by three-dimensional reciprocal space mapping obtained from reflection high energy electron diffraction (RHEED) data. High-temperature single stage growth regime was adopted to fabricate CoFeB layers. As confirmed by the atomic force microscopy, the surface of CoFeB layers consists of closely spaced nanometer sized islands with dimensions dependent on the growth temperature. As shown by RHEED and XRD analysis, the CoFeB layers grown at high-temperature on MgO(001) possess body centered cubic (bcc) crystal structure with the lattice constant a =2.87 Å close to that of the C o75F e25 alloy. It was further shown that following the same high-temperature growth technique the MgO/CoFeB/MgO(001) heterostructures can be fabricated with top and bottom MgO layers of the same crystallographic orientation. The CoFeB layers were also grown on the GaN(0001) substrates using MgO(111) as a buffer layer. In this case, the CoFeB layers crystallize in bcc crystal structure with the (111) axis perpendicular to the substrate surface. The magnetic properties of the CoFeB/MgO (001) heterostructures have been investigated by measuring magnetization curves with a vibrating sample magnetometer as well as by performing magneto-optical Kerr effect (MOKE) and ferromagnetic resonance (FMR) studies. FMR spectra were obtained for the variety of the magnetic field directions and typically consisted of a single relatively narrow resonance line. The magnetization orientations and the resonance conditions were calculated in the framework of a standard magnetic energy minimization procedure involving a single K1 c cubic term for the magnetocrystalline anisotropy. This allows a fairly accurate description of the angular dependences of the resonance fields—both in-plane and out-of-plane. It was shown that CoFeB layers exhibit

  15. 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.

  16. Photoluminescence characteristics of ZnTe bulk crystal and ZnTe epilayer grown on GaAs substrate by MOVPE

    Science.gov (United States)

    Lü, Hai-Yan; Mu, Qi; Zhang, Lei; Lü, Yuan-Jie; Ji, Zi-Wu; Feng, Zhi-Hong; Xu, Xian-Gang; Guo, Qi-Xin

    2015-12-01

    Excitation power and temperature-dependent photoluminescence (PL) spectra of the ZnTe epilayer grown on (100) GaAs substrate and ZnTe bulk crystal are investigated. The measurement results show that both the structures are of good structural quality due to their sharp bound excitonic emissions and absence of the deep level structural defect-related emissions. Furthermore, in contrast to the ZnTe bulk crystal, although excitonic emissions for the ZnTe epilayer are somewhat weak, perhaps due to As atoms diffusing from the GaAs substrate into the ZnTe epilayer and/or because of the strain-induced degradation of the crystalline quality of the ZnTe epilayer, neither the donor-acceptor pair (DAP) nor conduction band-acceptor (e-A) emissions are observed in the ZnTe epilayer. This indicates that by further optimizing the growth process it is possible to obtain a high-crystalline quality ZnTe heteroepitaxial layer that is comparable to the ZnTe bulk crystal. Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120131110006), the Key Science and Technology Program of Shandong Province, China (Grant No. 2013GGX10221), the Key Laboratory of Functional Crystal Materials and Device (Shandong University, Ministry of Education), China (Grant No. JG1401), the National Natural Science Foundation of China (Grant No. 61306113), the Major Research Plan of the National Natural Science Foundation of China (Grant No. 91433112), and the Partnership Project for Fundamental Technology Researches of the Ministry of Education, Culture, Sports, Science and Technology, Japan.

  17. Development of surgical gamma probes with TlBr semiconductors and CsI(Tl) scintillators crystals

    International Nuclear Information System (INIS)

    Costa, Fabio Eduardo da

    2006-01-01

    Radio guided surgery, using probes with radiation detectors, has been prominence in the medical area in the last decade. This technique consists in injecting a radioactive substance to concentrate in tumour and assist the localization during the surgical procedure. The radio guided surgeries allowing the identification of lymph node has revolutioned the behavior of tumour in initial stadium when are being spread by lymphatic way. The conditions imposed to the surgery due the proximity between some lymph nodes, demands of the probes, a small diameters and capacity of individual identification of these lymph nodes radiolabelled by a specific tracer. The international market supplies these probes with CdTe semiconductors and scintillators, but there is some time lack a promptly technical assistance in the Brazilian market. This work developed probes with national technology, using CsI(Tl) scintillators crystals and, in substitution to CdTe crystals semiconductors, the TlBr crystal, that is a new semiconductor detector in a world-wide development, with advantages in relation to the CdTe. Both crystals have been grown in IPEN. All the necessary electronics, specially, the preamplifier, that was also a restrictive factor for development of these types of probe in the country, have been developed with components found in the national market. Systematic measures of spatial resolution, spatial selectivity, maximum sensitivity and quality of the shielding have been carried the probes development. The results have shown that the probes, one with the CsI(Tl) crystal and another with TlBr semiconductor presented the requested performance in the international literature for radio guided probes. (author)

  18. Single-crystal SrTiO3 fiber grown by laser heated pedestal growth method: influence of ceramic feed rod preparation in fiber quality

    Directory of Open Access Journals (Sweden)

    D. Reyes Ardila

    1998-10-01

    Full Text Available The rapidly spreading use of optical fiber as a transmission medium has created an interest in fiber-compatible optical devices and methods for growing them, such as the Laser Heated Pedestal Growth (LHPG. This paper reports on the influence of the ceramic feed rod treatment on fiber quality and optimization of ceramic pedestal processing that allows improvements to be made on the final quality in a simple manner. Using the LHPG technique, transparent crack-free colorless single crystal fibers of SrTiO3 (0.50 mm in diameter and 30-40 mm in length were grown directly from green-body feed rods, without using external oxygen atmosphere.

  19. Research Update: Point defects in CdTexSe1−x crystals grown from a Te-rich solution for applications in detecting radiation

    Directory of Open Access Journals (Sweden)

    R. Gul

    2015-04-01

    Full Text Available We investigated cadmium telluride selenide (CdTeSe crystals, newly grown by the Traveling Heater Method (THM, for the presence and abundance of point defects. Current Deep Level Transient spectroscopy (I-DLTS was used to determine the energies of the traps, their capture cross sections, and densities. The bias across the detectors was varied from 1 to 30 V. Four types of point defects were identified, ranging from 10 meV to 0.35 eV. Two dominant traps at energies of 0.18 eV and 0.14 eV were studied in depth. Cd vacancies are found at lower concentrations than other point defects present in the material.

  20. Microstructure and magnetic properties of FeCo epitaxial thin films grown on MgO single-crystal substrates

    International Nuclear Information System (INIS)

    Shikada, Kouhei; Ohtake, Mitsuru; Futamoto, Masaaki; Kirino, Fumiyoshi

    2009-01-01

    FeCo epitaxial films were prepared on MgO(100), MgO(110), and MgO(111) substrates by ultrahigh vacuum molecular beam epitaxy. FeCo thin films with (100), (211), and (110) planes parallel to the substrate surface grow on respective MgO substrates. FeCo/MgO interface structures are studied by high-resolution cross-sectional transmission electron microscopy and the epitaxial growth mechanism is discussed. Atomically sharp boundaries are recognized between the FeCo thin films and the MgO substrates where misfit dislocations are introduced in the FeCo thin films presumably to decrease the lattice misfits. Misfit dislocations are observed approximately every 9 and 1.4 nm in FeCo thin film at the FeCo/MgO(100) and the FeCo/MgO(110) interfaces, respectively. X-ray diffraction analysis indicates that the lattice spacing measured parallel to the single-crystal substrate surfaces are in agreement within 0.1% with those of the respective bulk values of Fe 50 Co 50 alloy crystal, showing that the FeCo film strain is very small. The magnetic anisotropies of these epitaxial films basically reflect the magnetocrystalline anisotropy of bulk FeCo alloy crystal

  1. Solution-grown small-molecule organic semiconductor with enhanced crystal alignment and areal coverage for organic thin film transistors

    Directory of Open Access Journals (Sweden)

    Sheng Bi

    2015-07-01

    Full Text Available Drop casting of small-molecule organic semiconductors typically forms crystals with random orientation and poor areal coverage, which leads to significant performance variations of organic thin-film transistors (OTFTs. In this study, we utilize the controlled evaporative self-assembly (CESA method combined with binary solvent system to control the crystal growth. A small-molecule organic semiconductor,2,5-Di-(2-ethylhexyl-3,6-bis(5″-n-hexyl-2,2′,5′,2″]terthiophen-5-yl-pyrrolo[3,4-c]pyrrole-1,4-dione (SMDPPEH, is used as an example to demonstrate the effectiveness of our approach. By optimizing the double solvent ratios, well-aligned SMDPPEH crystals with significantly improved areal coverage were achieved. As a result, the SMDPPEH based OTFTs exhibit a mobility of 1.6 × 10−2 cm2/V s, which is the highest mobility from SMDPPEH ever reported.

  2. 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.

  3. Optical anomalies and residual stresses in basal-plane-faceted ribbons of Stepanov-grown sapphire crystals

    Science.gov (United States)

    Denisov, A. V.; Krymov, V. M.; Punin, Yu. O.

    2007-03-01

    The effects of an anomalous biaxiality and a residual-stress field in basal-plane-faceted single-crystal sapphire ribbons were studied by an optical polarization method using a conoscopic light beam. Formulas that relate the difference between the principal stresses to the angle of optical-axis divergence are obtained. It is shown that the central regions of the ribbons undergo compressive stresses whereas their edges undergo tensile stresses. As compared to block-free ribbons, the stresses in block-containing ribbons increase more intensely with distance from the seed.

  4. Structural characterization of metastable hcp-Ni thin films epitaxially grown on Au(100) single-crystal underlayers

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    Ni(1120) epitaxial thin films with hcp structure were prepared on Au(100) single-crystal underlayers at 100 deg. C by ultra high vacuum molecular beam epitaxy. The detailed film structure is studied by in situ reflection high energy electron diffraction, x-ray diffraction, and transmission electron microscopy. The hcp-Ni film consists of two types of variants whose c-axes are rotated around the film normal by 90 deg. each other. An atomically sharp boundary is recognized between the film and the underlayer, where misfit dislocations are introduced. Presence of such dislocations seems to relieve the strain caused by the lattice mismatch between the film and the underlayer.

  5. Scintillation properties of μPD-grown Y{sub 4}Al{sub 2}O{sub 9}:Pr (YAM:Pr) crystals

    Energy Technology Data Exchange (ETDEWEB)

    Drozdowski, Winicjusz, E-mail: wind@fizyka.umk.pl [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun (Poland); Brylew, Kamil [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun (Poland); Malinowski, Michał [Institute of Microelectronics and Optoelectronics, Koszykowa 75, 00-662 Warsaw (Poland); Turczyński, Sebastian [Institute of Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw (Poland)

    2015-05-25

    Highlights: • YAM:Pr crystals do scintillate and as such deserve further interest. • Fast d–f luminescence of Pr{sup 3+} ions appears in X-ray excited spectra. • Two components (24 and 790 ns) constitute scintillation time profiles. - Abstract: Y{sub 4}Al{sub 2}O{sub 9}:Pr (YAM:Pr) crystals have been grown by the micro-pulling-down method and their scintillation properties have been investigated. YAM:0.1%Pr displays a light yield of about 2000 ph/MeV and its scintillation time profile contains a prompt component with a decay time of 23.5 ns and a contribution of 20%. Radioluminescence spectra show both fast d–f and slow f–f praseodymium emissions. Low temperature glow curves are complex, consisting of discrete peaks and broad bands related to quasi-continuous trap distributions. Overall scintillation performance of YAM:Pr deteriorates with increasing praseodymium concentration.

  6. High-Performance Flexible Thin-Film Transistors Based on Single-Crystal-like Silicon Epitaxially Grown on Metal Tape by Roll-to-Roll Continuous Deposition Process.

    Science.gov (United States)

    Gao, Ying; Asadirad, Mojtaba; Yao, Yao; Dutta, Pavel; Galstyan, Eduard; Shervin, Shahab; Lee, Keon-Hwa; Pouladi, Sara; Sun, Sicong; Li, Yongkuan; Rathi, Monika; Ryou, Jae-Hyun; Selvamanickam, Venkat

    2016-11-02

    Single-crystal-like silicon (Si) thin films on bendable and scalable substrates via direct deposition are a promising material platform for high-performance and cost-effective devices of flexible electronics. However, due to the thick and unintentionally highly doped semiconductor layer, the operation of transistors has been hampered. We report the first demonstration of high-performance flexible thin-film transistors (TFTs) using single-crystal-like Si thin films with a field-effect mobility of ∼200 cm 2 /V·s and saturation current, I/l W > 50 μA/μm, which are orders-of-magnitude higher than the device characteristics of conventional flexible TFTs. The Si thin films with a (001) plane grown on a metal tape by a "seed and epitaxy" technique show nearly single-crystalline properties characterized by X-ray diffraction, Raman spectroscopy, reflection high-energy electron diffraction, and transmission electron microscopy. The realization of flexible and high-performance Si TFTs can establish a new pathway for extended applications of flexible electronics such as amplification and digital circuits, more than currently dominant display switches.

  7. Analysis on volume fraction and crystal orientation relationship of monoclinic and tetragonal oxide grown on Zr-2.5Nb alloy

    Energy Technology Data Exchange (ETDEWEB)

    Lin Jianlong [Department of Metallurgical Engineering, McGill University, Montreal, H3A 2B2 (Canada)]. E-mail: jianlong.lin@mail.mcgill.ca; Li Hualong [Department of Metallurgical Engineering, McGill University, Montreal, H3A 2B2 (Canada); Nam, Cheol [Department of Metallurgical Engineering, McGill University, Montreal, H3A 2B2 (Canada); Szpunar, Jerzy A. [Department of Metallurgical Engineering, McGill University, Montreal, H3A 2B2 (Canada)

    2004-09-01

    Texture and phase volume fraction of the oxide grown on Zr-2.5Nb, in static autoclaves, at 623 K, with lithiated heavy water were investigated. It is found that both monoclinic and tetragonal zirconia are highly textured with {l_brace}100{r_brace}<100> preferred crystal orientation for the tetragonal phase, and (103-bar )[01-bar 0] and (104-bar)[401] texture for the monoclinic phase. No change in the texture for both phases was observed with the increase of thickness of the oxide layer. The crystal orientation relationship of both the monoclinic and tetragonal phases was found to be (103-bar )m-bar (100)t or (103-bar )m-bar (101)t and [100]t-bar [010]m. The integrated intensity over pole figures was used to calculate the volume fraction of the tetragonal phase in the oxide layer. The volume fraction of the tetragonal phase in the dense oxide layer near the metal-oxide interface was found to be about 8% and gradually decreases with an increase of the oxide thickness.

  8. Bioprecipitation of Calcium Carbonate Crystals by Bacteria Isolated from Saline Environments Grown in Culture Media Amended with Seawater and Real Brine

    Directory of Open Access Journals (Sweden)

    G. A. Silva-Castro

    2015-01-01

    Full Text Available The precipitation of calcium carbonate and calcium sulphate by isolated bacteria from seawater and real brine obtained in a desalination plant growth in culture media containing seawater and brine as mineral sources has been studied. However, only bioprecipitation was detected when the bacteria were grown in media with added organic matter. Biomineralization process started rapidly, crystal formation taking place in the beginning a few days after inoculation of media; roughly 90% of total cultivated bacteria showed. Six major colonies with carbonate precipitation capacity dominated bacterial community structure cultivated in heterotrophic platable bacteria medium. Taxonomic identification of these six strains through partial 16S rRNA gene sequences showed their affiliation with Gram-positive Bacillus and Virgibacillus genera. These strains were able to form calcium carbonate minerals, which precipitated as calcite and aragonite crystals and showed bacterial fingerprints or bacteria calcification. Also, carbonic anhydrase activity was observed in three of these isolated bacteria. The results of this research suggest that microbiota isolated from sea water and brine is capable of precipitation of carbonate biominerals, which can occur in situ with mediation of organic matter concentrations. Moreover, calcium carbonate precipitation ability of this microbiota could be of importance in bioremediation of CO2 and calcium in certain environments.

  9. Structural and luminescent properties of Fe3+ doped PVA capped CdTe nanoparticles

    Directory of Open Access Journals (Sweden)

    Ravindranadh K.

    2017-07-01

    Full Text Available During recent decades, magnetic and semiconductor nanoparticles have attracted significant attention of scientists in various fields of engineering, physics, chemistry, biology and medicine. Fe3+ doped PVA capped CdTe nanoparticles were prepared by co-precipitation method and characterized by powder X-ray diffraction, SEM, TEM, FT-IR, optical, EPR and PL techniques to collect the information about the crystal structure, coordination/local site symmetry of doped Fe3+ ions in the host lattice and the luminescent properties of prepared sample. Powder XRD data revealed that the crystal structure belongs to a cubic system and its lattice cell parameters were evaluated. The average crystallite size was estimated to be 8 nm. The morphology of prepared samples was analyzed by using SEM and TEM investigations. Functional groups of the prepared sample were observed in FT-IR spectra. Optical absorption and EPR studies have shown that on doping, Fe3+ ions enter the host lattice in octahedral site symmetry. PL studies of Fe3+ doped PVA capped CdTe nanoparticles revealed UV and blue emission bands. CIE chromaticity coordinates were also calculated from the emission spectrum of Fe3+ doped PVA capped CdTe nanoparticles.

  10. Structural properties, crystal quality and growth modes of MOCVD-grown AlN with TMAl pretreatment of sapphire substrate

    KAUST Repository

    Sun, Haiding

    2017-08-08

    The growth of high quality AlN epitaxial films relies on precise control of the initial growth stages. In this work, we examined the influence of the trimethylaluminum (TMAl) pretreatment of sapphire substrates on the structural properties, crystal quality and growth modes of heteroepitaxial AlN films on (0001) sapphire substrates. Without the pretreatment, the AlN films nucleated on the smooth surface but exhibited mixed crystallographic Al- (N-) polarity, resulting in rough AlN film surfaces. With increasing the pretreatment time from 1 to 5 s, the N-polarity started to be impeded. However, small islands were formed on sapphire surface due to the decompostion of TMAl. As a result, small voids became noticeable at the nucleation layer (NL) because the growth started as quasi three-dimensional (3D) but transformed to 2D mode as the film grew thicker and got coalesced, leading to smoother and Al-polar films. On the other hand, longer pretreatment time of 40 s formed large 3D islands on sapphire, and thus initiated a 3D-growth mode of the AlN film, generating Al-polar AlN nanocolumns with different facets, which resulted into rougher film surfaces. The epitaxial growth modes and their correlation with the AlN film crystal quality under different TMAl pretreatments are also discussed.

  11. Microstructure of Co(112-bar 0) epitaxial thin films, grown on MgO(100) single-crystal substrates

    International Nuclear Information System (INIS)

    Nukaga, Yuri; Ohtake, Mitsuru; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    Co(112-bar 0) epitaxial thin films with hcp structure were prepared on MgO(100) single-crystal substrates heated at 300 0 C by ultra high vacuum molecular beam epitaxy. The microstructure is investigated by employing X-ray diffraction and high-resolution transmission electron microscopy. The film consists of two types of domains whose c-axes are rotated around the film normal by 90 0 each other. Stacking faults are observed for the film along the Co[0001] direction. An atomically sharp boundary is recognized between the film and the substrate, where some misfit dislocations are introduced in the film at the Co/MgO interface. Dislocations are also observed in the film up to 15 nm thickness from the interface. Presence of such stacking faults and misfit dislocations seem to relieve the strain caused by the lattice mismatch between the film and the substrate. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of the film are in agreement within 0.5% and 0.1%, respectively, with those of the bulk hcp-Co crystal, suggesting the strain in the film is very small.

  12. Microneedle crystals of cyano-substituted thiophene/phenylene co-oligomer epitaxially grown on KCl surface

    Science.gov (United States)

    Torii, Kazuki; Dokiya, Shohei; Tanaka, Yosuke; Yoshinaga, Shohei; Yanagi, Hisao

    2017-06-01

    A cyno-substituted thiophene/phenylene co-oligomer (TPCO), 5,5‧-bis(4‧-cyanobiphenyl-4-yl)-2,2‧-bithiophene (BP2T-CN), is vapor-deposited on KCl (001) surface kept at 220 °C by the mask-shadowing method. Transmission electron microscopy and fluorescence microscopy reveal that the deposited BP2T-CN crystallizes in two types of morphologies: microneedles and thin film crystallites. In particular, the predominant microneedles epitaxially grow in four directions in the manner that the BP2T-CN molecules align along the [110]KCl or [-110]KCl. X-ray diffraction patterns indicate that the BP2T-CN molecules in the microneedle lie parallel while those in the thin film crystallite obliquely stand on the KCl surface.

  13. Thin yttrium iron garnet films grown by pulsed laser deposition: Crystal structure, static, and dynamic magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, N. S., E-mail: nsokolov@fl.ioffe.ru; Fedorov, V. V.; Korovin, A. M.; Suturin, S. M.; Baranov, D. A.; Gastev, S. V.; Krichevtsov, B. B.; Bursian, V. E.; Lutsev, L. V. [Ioffe Physical-Technical Institute of Russian Academy of Sciences, St. Petersburg 194021 (Russian Federation); Maksimova, K. Yu.; Grunin, A. I. [Immanuel Kant Baltic Federal University, Kaliningrad 236041 (Russian Federation); Tabuchi, M. [Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603 (Japan)

    2016-01-14

    Pulsed laser deposition has been used to grow thin (10–84 nm) epitaxial layers of Yttrium Iron Garnet Y{sub 3}Fe{sub 5}O{sub 12} (YIG) on (111)–oriented Gadolinium Gallium Garnet substrates at different growth conditions. Atomic force microscopy showed flat surface morphology both on micrometer and nanometer scales. X-ray diffraction measurements revealed that the films are coherent with the substrate in the interface plane. The interplane distance in the [111] direction was found to be by 1.2% larger than expected for YIG stoichiometric pseudomorphic film indicating presence of rhombohedral distortion in this direction. Polar Kerr effect and ferromagnetic resonance measurements showed existence of additional magnetic anisotropy, which adds to the demagnetizing field to keep magnetization vector in the film plane. The origin of the magnetic anisotropy is related to the strain in YIG films observed by XRD. Magneto-optical Kerr effect measurements revealed important role of magnetization rotation during magnetization reversal. An unusual fine structure of microwave magnetic resonance spectra has been observed in the film grown at reduced (0.5 mTorr) oxygen pressure. Surface spin wave propagation has been demonstrated in the in-plane magnetized films.

  14. Studies on the deep-level defects in CdZnTe crystals grown by travelling heater method

    International Nuclear Information System (INIS)

    Zhou, Boru; Jie, Wanqi; Wang, Tao; Xu, Lingyan; Yang, Fan; Yin, Liying; Fu, Xu; Nan, Ruihua

    2017-01-01

    The variation of deep level defects along the axis of CZT:In ingots grown by Travelling Heater Method was investigated by the means of thermally stimulated current (TSC) spectra. Models for the reaction among different defects In, Te i , and V Cd were used to analyze the variation of deep level defects along the growth direction. It was found that the density of In dopant-related defects is lower in the tip, but those of Te antisites and Te interstitials are higher in the tip. The density of cadmium vacancy exhibits an initial increase followed by a decrease from the tip to tail of the ingot. In PL spectra, the intensities of (D 0 , X), (DAP) and D complex peaks obviously increase from the tip to the tail, due to the increase of the density of In dopant-related defects (IN + CD ), Cd vacancies, and impurities. The low concentration of net free holes was found by Hall measurements, and high resistivity with p-type conduction was demonstrated from I-V analysis. The mobility for electrons was found to increase significantly from 634 ± 26 cm 2 V -1 s -1 in the tip to 860 ± 10 cm 2 V -1 s -1 in the tail, due to the decrease of the deep level defect densities. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Thin yttrium iron garnet films grown by pulsed laser deposition: Crystal structure, static, and dynamic magnetic properties

    International Nuclear Information System (INIS)

    Sokolov, N. S.; Fedorov, V. V.; Korovin, A. M.; Suturin, S. M.; Baranov, D. A.; Gastev, S. V.; Krichevtsov, B. B.; Bursian, V. E.; Lutsev, L. V.; Maksimova, K. Yu.; Grunin, A. I.; Tabuchi, M.

    2016-01-01

    Pulsed laser deposition has been used to grow thin (10–84 nm) epitaxial layers of Yttrium Iron Garnet Y 3 Fe 5 O 12 (YIG) on (111)–oriented Gadolinium Gallium Garnet substrates at different growth conditions. Atomic force microscopy showed flat surface morphology both on micrometer and nanometer scales. X-ray diffraction measurements revealed that the films are coherent with the substrate in the interface plane. The interplane distance in the [111] direction was found to be by 1.2% larger than expected for YIG stoichiometric pseudomorphic film indicating presence of rhombohedral distortion in this direction. Polar Kerr effect and ferromagnetic resonance measurements showed existence of additional magnetic anisotropy, which adds to the demagnetizing field to keep magnetization vector in the film plane. The origin of the magnetic anisotropy is related to the strain in YIG films observed by XRD. Magneto-optical Kerr effect measurements revealed important role of magnetization rotation during magnetization reversal. An unusual fine structure of microwave magnetic resonance spectra has been observed in the film grown at reduced (0.5 mTorr) oxygen pressure. Surface spin wave propagation has been demonstrated in the in-plane magnetized films

  16. Edge effects in a small pixel CdTe for X-ray imaging

    Science.gov (United States)

    Duarte, D. D.; Bell, S. J.; Lipp, J.; Schneider, A.; Seller, P.; Veale, M. C.; Wilson, M. D.; Baker, M. A.; Sellin, P. J.; Kachkanov, V.; Sawhney, K. J. S.

    2013-10-01

    Large area detectors capable of operating with high detection efficiency at energies above 30 keV are required in many contemporary X-ray imaging applications. The properties of high Z compound semiconductors, such as CdTe, make them ideally suitable to these applications. The STFC Rutherford Appleton Laboratory has developed a small pixel CdTe detector with 80 × 80 pixels on a 250 μm pitch. Historically, these detectors have included a 200 μm wide guard band around the pixelated anode to reduce the effect of defects in the crystal edge. The latest version of the detector ASIC is capable of four-side butting that allows the tiling of N × N flat panel arrays. To limit the dead space between modules to the width of one pixel, edgeless detector geometries have been developed where the active volume of the detector extends to the physical edge of the crystal. The spectroscopic performance of an edgeless CdTe detector bump bonded to the HEXITEC ASIC was tested with sealed radiation sources and compared with a monochromatic X-ray micro-beam mapping measurements made at the Diamond Light Source, U.K. The average energy resolution at 59.54 keV of bulk and edge pixels was 1.23 keV and 1.58 keV, respectively. 87% of the edge pixels present fully spectroscopic performance demonstrating that edgeless CdTe detectors are a promising technology for the production of large panel radiation detectors for X-ray imaging.

  17. 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.

  18. 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

    devices. We demonstrated the conduction mechanism by which CdTe polycrystals improve the performance of the devices relative to single crystal devices. The mechanism shows that grain boundaries are conduction pathways for photogenerated electrons and that the corresponding holes are confined to the grains and therefore do not contribute to recombination.

  19. 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.

  20. Mapping the 3D distribution of CdSe nanocrystals in highly oriented and nanostructured hybrid P3HT-CdSe films grown by directional epitaxial crystallization.

    Science.gov (United States)

    Roiban, L; Hartmann, L; Fiore, A; Djurado, D; Chandezon, F; Reiss, P; Legrand, J-F; Doyle, S; Brinkmann, M; Ersen, O

    2012-11-21

    Highly oriented and nanostructured hybrid thin films made of regioregular poly(3-hexylthiophene) and colloidal CdSe nanocrystals are prepared by a zone melting method using epitaxial growth on 1,3,5-trichlorobenzene oriented crystals. The structure of the films has been analyzed by X-ray diffraction using synchrotron radiation, electron diffraction and 3D electron tomography to afford a multi-scale structural and morphological description of the highly structured hybrid films. A quantitative analysis of the reconstructed volumes based on electron tomography is used to establish a 3D map of the distribution of the CdSe nanocrystals in the bulk of the films. In particular, the influence of the P3HT-CdSe ratio on the 3D structure of the hybrid layers has been analyzed. In all cases, a bi-layer structure was observed. It is made of a first layer of pure oriented semi-crystalline P3HT grown epitaxially on the TCB substrate and a second P3HT layer containing CdSe nanocrystals uniformly distributed in the amorphous interlamellar zones of the polymer. The thickness of the P3HT layer containing CdSe nanoparticles increases gradually with increasing content of NCs in the films. A growth model is proposed to explain this original transversal organization of CdSe NCs in the oriented matrix of P3HT.

  1. 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-.

  2. 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.

  3. 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 ...

  4. 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)

  5. Development of surgical gamma probes with TlBr semiconductors and CsI(Tl) scintillators crystals; Desenvolvimento de sondas cirurgicas radioguiadas com semicondutores de TlBr e com cristais cintiladores de CsI (Tl)

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Fabio Eduardo da

    2006-07-01

    Radio guided surgery, using probes with radiation detectors, has been prominence in the medical area in the last decade. This technique consists in injecting a radioactive substance to concentrate in tumour and assist the localization during the surgical procedure. The radio guided surgeries allowing the identification of lymph node has revolutioned the behavior of tumour in initial stadium when are being spread by lymphatic way. The conditions imposed to the surgery due the proximity between some lymph nodes, demands of the probes, a small diameters and capacity of individual identification of these lymph nodes radiolabelled by a specific tracer. The international market supplies these probes with CdTe semiconductors and scintillators, but there is some time lack a promptly technical assistance in the Brazilian market. This work developed probes with national technology, using CsI(Tl) scintillators crystals and, in substitution to CdTe crystals semiconductors, the TlBr crystal, that is a new semiconductor detector in a world-wide development, with advantages in relation to the CdTe. Both crystals have been grown in IPEN. All the necessary electronics, specially, the preamplifier, that was also a restrictive factor for development of these types of probe in the country, have been developed with components found in the national market. Systematic measures of spatial resolution, spatial selectivity, maximum sensitivity and quality of the shielding have been carried the probes development. The results have shown that the probes, one with the CsI(Tl) crystal and another with TlBr semiconductor presented the requested performance in the international literature for radio guided probes. (author)

  6. Observation of Hg-diffusion in CdTe using heavy ion (40MeV-O5+) backscattering

    International Nuclear Information System (INIS)

    Otake, H.; Takita, K.; Murakami, K.; Masuda, K.; Kudo, H.; Seki, S.

    1984-01-01

    Diffusion of Hg in the near-surface region of CdTe crystals was observed by means of 40MeV-O 5+ ion backscattering. CdTe crystals immersed in Hg were kept in furnace at 280 -- 340 0 C for 2 -- 240hours. The backscattering spectra of these crystals were measured. The concentration of the diffused Hg atoms in the surface reached to 4 x 10 20 cm -3 , and Hg distribution was observed up to 1.4 μm from surface. Temperature dependence of the diffusion coefficients was determined as D = 5 x 10 3 exp (-2.0 +- 0.3eV/kT) cm 2 /sec. Hg-diffusion was not observed in the case of CdTe kept in Hg with a small amount of Cd. These facts suggest that Hg diffusion is controlled by the diffusion of Cd-vacancy. A method of observing the Hg-atoms profile in the near-surface region of the semiconductor was established. (author)

  7. Study of CdTe surface by SIMS and RBS ellipsometry

    International Nuclear Information System (INIS)

    Stuck, R.; Hage-Ali, M.; Grob, A.; Siffert, P.

    1978-01-01

    For a better understanding of the mechanisms involved in the rectification of metal-cadmium telluride contacts, the surface of bromine-methanol etched CdTe crystals by means of ellipsometry, secondary ions mass spectroscopy (SIMS) and Rutherford backscattering of charged particles (RBS) has been investigated. The results show that these surfaces are contaminated with bromine and that a tellurium surface oxide layer grows, its thickness increasing with time. This surface layer composition has been analyzed at different steps of its evolution [fr

  8. 3d-impurity levels in CdTe and ZnSe

    International Nuclear Information System (INIS)

    Tovstyuk, K.D.; Deybuk, V.G.; Melnichuk, S.V.; Tovstyuk, N.K.

    1985-01-01

    Energy level calculations of deep levels of 3d impurities (Cr, Mn, Fe, Co, Ni, Sc, Ti, V) in CdTe and ZnSe were made using the molecular cluster method and the MO LCAO method solving the secular equation. A 17-atom cluster consisting of a central atom and two coordination spheres were employed. The depth of the impurity levels in the energy gap increases with the atomic number of the impurity atom. Sc, Ti, and V impurities do not give impurity levels in the energy gap. The change in the lattice constant due to doping of AIIBVI crystals has been evaluated

  9. Optical Absorption Enhancement in CdTe Thin Films by Microstructuration of the Silicon Substrate

    Directory of Open Access Journals (Sweden)

    Jesús Rangel-Cárdenas

    2017-06-01

    Full Text Available In this work, the reflectance, optical absorption, and band gap have been determined for CdTe thin films grown on planar and microstructured substrates. The treated surface was prepared by laser ablation of a silicon wafer, forming holes in a periodic arrangement. Thin films were grown by pulsed laser ablation on silicon samples kept at 200 °C inside a vacuum chamber. The presence of CdTe was verified with X-ray diffraction and Raman spectroscopy indicating a nanocrystalline zinc blended structure. The optical absorption of thin films was calculated by using the Fresnel laws and the experimental reflectance spectrum. Results show that reflectance of 245 nm films deposited on modified substrates is reduced by up to a factor of two than the obtained on unchanged silicon and the optical absorption is 16% higher at ~456 nm. Additionally, it was determined that the band gap energy for planar and microstructured films is about 1.44 eV for both cases.

  10. Electrochemical quartz crystal impedance study on immobilization of glucose oxidase in a polymer grown from dopamine oxidation at an Au electrode for glucose sensing

    International Nuclear Information System (INIS)

    Li Mingrui; Deng Chunyan; Xie Qingji; Yang Yang; Yao Shouzhuo

    2006-01-01

    Glucose oxidase (GOD) was codeposited into a polymer grown from oxidation of dopamine (DA) at an Au electrode in a neutral phosphate aqueous solution for the first time. The electrochemical quartz crystal impedance analysis (EQCIA) method was used to monitor the GOD-immobilization process. Effects of concentrations of phosphate buffer, DA and GOD were investigated, and the optimal concentrations were found to be 20.0mM phosphate buffer (pH 7.0), 30.0mM DA and 5.00mgml -1 GOD. A glucose biosensor was thus constructed, and effects of various experimental parameters on the sensor performance, including applied potential, solution pH and electroactive interferents, were examined. At an optimal potential of 0.6V versus the KCl-saturated calomel electrode (SCE), the current response of the biosensor in the selected phosphate buffer (pH 7.0) was linear with the concentration of glucose from 0.05 to 9mM, with a lower detection limit of 3μM (S/N=3), short response time (within 15s) and good anti-interferent ability. The Michaelis constant (K m app ) was estimated to be 9.6mM. The biosensor exhibited good storage stability, i.e. 96% of its initial response was retained after 7-day storage in the selected phosphate buffer at 4deg. C, and even after another 3 weeks the biosensor retained 86% of its initial response. In addition, the enzymatic specific activity and enzymatic relative activity of the GOD immobilized in the polymer from dopamine oxidation (PFDO) were estimated from the EQCIA method to be 1.43kUg -1 and 3.7%, respectively, which were larger than the relevant values obtained experimentally using poly(o-aminophenol) and poly(N-methylpyrrole) matrices, suggesting that the PFDO is a better matrix to immobilize GOD

  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. 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.

  13. 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

  14. Growth rate and surface morphology of 4H-SiC crystals grown from Si-Cr-C and Si-Cr-Al-C solutions under various temperature gradient conditions

    Science.gov (United States)

    Mitani, Takeshi; Komatsu, Naoyoshi; Takahashi, Tetsuo; Kato, Tomohisa; Fujii, Kuniharu; Ujihara, Toru; Matsumoto, Yuji; Kurashige, Kazuhisa; Okumura, Hajime

    2014-09-01

    The growth rate and surface morphology of 4H-SiC crystals prepared by solution growth with Si1-xCrx and Si1-x-yCrxAly (x=0.4, 0.5 and 0.6; y=0.04) solvents were investigated under various temperature conditions. The growth rate was examined as functions of the temperature difference between the growth surface and C source, the amount of supersaturated C and supersaturation at the growth surface. We found that generation of trench-like surface defects in 4H-SiC crystals was suppressed using Si1-x-yCrxAly solvents even under highly supersaturated conditions where the growth rate exceeded 760 μm/h. Conversely, trench-like defects were observed in crystals grown with Si1-xCrx solvents under all experimental conditions. Statistical observation of the macrostep structure showed that the macrostep height in crystals grown with Si1-x-yCrxAly solvents was maintained at lower levels than that obtained using Si1-xCrx solvents. Addition of Al prevents the macrosteps from developing into large steps, which are responsible for the generation of trench-like surface defects.

  15. 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.

  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. 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 ...

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. Electrical activity of In and Ga impurities in CdTe

    International Nuclear Information System (INIS)

    Fochuk, P.; Panchuk, O.; Korovyanko, O.

    2004-01-01

    The issue of modelling of point defect structure in In(Ga)-doped CdTe crystals has been analyzed. Contrary to previous papers, it has been shown that high-temperature point defect equilibrium modelling can be successfully achieved if sufficient experimental data are available and appropriate calculation methods are used. Room temperature free electron densities were computed for CdTe:In crystals and compared with experimental data. Since the density of point defects changes during cooling from the preparation to operational temperatures, it cannot be estimated. Therefore, a new approach, including calculation of a certain fitting Δ parameter, is proposed. Its determination allows preparation/cooling conditions necessary to prepare material with the desired electric properties to be defined

  3. 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.

  4. 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.)

  5. 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

  6. Virtual Crystallizer

    Energy Technology Data Exchange (ETDEWEB)

    Land, T A; Dylla-Spears, R; Thorsness, C B

    2006-08-29

    Large dihydrogen phosphate (KDP) crystals are grown in large crystallizers to provide raw material for the manufacture of optical components for large laser systems. It is a challenge to grow crystal with sufficient mass and geometric properties to allow large optical plates to be cut from them. In addition, KDP has long been the canonical solution crystal for study of growth processes. To assist in the production of the crystals and the understanding of crystal growth phenomena, analysis of growth habits of large KDP crystals has been studied, small scale kinetic experiments have been performed, mass transfer rates in model systems have been measured, and computational-fluid-mechanics tools have been used to develop an engineering model of the crystal growth process. The model has been tested by looking at its ability to simulate the growth of nine KDP boules that all weighed more than 200 kg.

  7. 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)

  8. Application of ZnO single-crystal wire grown by the thermal evaporation method as a chemical gas sensor for hydrogen sulfide.

    Science.gov (United States)

    Park, N K; Lee, S Y; Lee, T J

    2011-01-01

    A zinc oxide single-crystal wire was synthesized for application as a gas-sensing material for hydrogen sulfide, and its gas-sensing properties were investigated in this study. The gas sensor consisted of a ZnO thin film as the buffer layer and a ZnO single-crystal wire. The ZnO thin film was deposited over a patterning silicon substrate with a gold electrode by the CFR method. The ZnO single-crystal wire was synthesized over the ZnO thin film using zinc and activated carbon as the precursor for the thermal evaporation method at 800 degrees C. The electrical properties of the gas sensors that were prepared for the growth of ZnO single-crystal wire varied with the amount of zinc contained in the precursor. The charged current on the gas sensors increased with the increasing amount of zinc in the precursor. It was concluded that the charged current on the gas sensors was related to ZnO single-crystal wire growth on the silicon substrate area between the two electrodes. The charged current on the gas sensor was enhanced when the ZnO single-crystal wire was exposed to a H2S stream. The experimental results obtained in this study confirmed that a ZnO single-crystal wire can be used as a gas sensor for H2S.

  9. 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. 

  10. Hydrothermal synthesis of CdTe quantum dots–TiO2–graphene hybrid

    International Nuclear Information System (INIS)

    Liu, Jinghua; Li, Xin

    2014-01-01

    CdTe–TiO 2 –graphene nanocomposites were successfully synthesized via a simple and relatively general hydrothermal method. During the hydrothermal environment, GO was reduced to reduced graphene oxide (RGO), accompanying with the anchoring of TiO 2 nanoparticles on the surface of RGO. In the following process, CdTe quantum dots (QDs) were then in situ grown on the carbon basal planes. The morphologies and structural properties of the as-prepared composites were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy and fluorescent spectroscopy. It is hoped that our current work could pave a way towards the fabrication of QDs–TiO 2 –RGO hybrid materials.

  11. Structure and superconductivity of (Li1-x Fe x )OHFeSe single crystals grown using A x Fe2-y Se2 (A  =  K, Rb, and Cs) as precursors.

    Science.gov (United States)

    Yu, G; Zhang, G Y; Ryu, G H; Lin, C T

    2016-01-13

    We present results on the hydrothermal growth of ([Formula: see text])OHFeSe single crystals using floating-zone-grown [Formula: see text] (A  =  K, Rb, and Cs) as precursors. The growth proceeds by the hydrothermal ion exchange of Li/Fe-O-H for K, Rb, and Cs, resulting in a stacking layer of ([Formula: see text])OH sandwiched between the FeSe layers. Optimal growth parameters are achieved using high quality A 0.80Fe1.81Se2 single crystals added to the mixtures of LiOH, H2O, Fe and C(NH2)2Se in an autoclave and subsequently heated to 120 °C for 2 d, to obtain highest quality single crystals. The obtained crystals have lateral dimensions up to centimeters, with the final size related to that of the precursor crystal used. All ([Formula: see text])OHFeSe single crystals show a superconducting transition temperature T c  >  42 K, regardless of the phase of the precursor such as superconducting K0.80Fe1.81Se2 (T c  =  29.31 K) or non-superconducting Rb0.80Fe1.81Se2 or poor-superconducting Cs0.80Fe1.81Se2 (T c  =  28.67 K). The T c and transition width ΔT vary in the obtained single crystals, due to the inhomogeneity of the ionic exchange. X-ray diffraction analysis demonstrates that the 245 insulating phase is absent in the ion-exchanged single crystals, while it is observed in the [Formula: see text] precursors. Comparative studies of the structure, magnetization, and superconductivity on the parent A 0.80Fe1.81Se2 and the ion-exchanged ([Formula: see text])OHFeSe crystals are discussed. A phase diagram including antiferromagnetic spin density wave and superconducting phases is also proposed.

  12. Basic performance and stability of a CdTe solid-state detector panel.

    Science.gov (United States)

    Tsuchiya, Katsutoshi; Takahashi, Isao; Kawaguchi, Tsuneaki; Yokoi, Kazuma; Morimoto, Yuuichi; Ishitsu, Takafumi; Suzuki, Atsurou; Ueno, Yuuichirou; Kobashi, Keiji

    2010-05-01

    We have developed a prototype gamma camera system (R1-M) using a cadmium telluride (CdTe) detector panel and evaluated the basic performance and the spectral stability. The CdTe panel consists of 5-mm-thick crystals. The field of view is 134 x 268 mm comprising 18,432 pixels with a pixel pitch of 1.4 mm. Replaceable small CdTe modules are mounted on to the circuit board by dedicated zero insertion force connectors. To make the readout circuit compact, the matrix read out is processed by dedicated ASICs. The panel is equipped with a cold-air cooling system. The temperature and humidity in the panel were kept at 20 degrees C and below 70% relative humidity. CdTe polarization was suppressed by the bias refresh technique to stabilize the detector. We also produced three dedicated square pixel-matched collimators: LEGP (20 mm-thick), LEHR (27 mm-thick), and LEUHR (35 mm-thick). We evaluated their basic performance (energy resolution, system resolution, and sensitivity) and the spectral stability in terms of short-term (several hours of continuous acquisition) and long-term (infrequent measurements over more than a year) activity. The intrinsic energy resolution (FWHM) acquired with Tc-99m (140.5 keV) was 6.6%. The spatial resolutions (FWHM at a distance of 100 mm) with LEGP, LEHR, and LEUHR collimators were 5.7, 4.9, and 4.2 mm, and the sensitivities were 71, 39, and 23 cps/MBq, respectively. The energy peak position and the intrinsic energy resolution after several hours of operation were nearly the same as the values a few minutes after the system was powered on; the variation of the peak position was <0.2%, and that of the resolution was about 0.3%. Infrequent measurements conducted over a year showed that the variations of the energy peak position and the intrinsic energy resolution of the system were at a similar level to those described above. The basic performance of the CdTe-gamma camera system was evaluated, and its stability was verified. It was shown that the

  13. Epitaxial single-crystal thin films of MnxTi1-xO2-δ grown on (rutile)TiO2 substrates with pulsed laser deposition: Experiment and theory

    Energy Technology Data Exchange (ETDEWEB)

    Ilton, Eugene S.; Droubay, Timothy C.; Chaka, Anne M.; Kovarik, Libor; Varga, Tamas; Arey, Bruce W.; Kerisit, Sebastien N.

    2015-02-01

    Epitaxial rutile-structured single-crystal MnxTi1-xO2-δ films were synthesized on rutile- (110) and -(001) substrates using pulsed laser deposition. The films were characterized by reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and aberration-corrected transmission electron microscopy (ACTEM). Under the present conditions, 400oC and PO2 = 20 mTorr, single crystal epitaxial thin films were grown for x = 0.13, where x is the nominal average mole fraction of Mn. In fact, arbitrarily thick films could be grown with near invariant Mn/Ti concentration profiles from the substrate/film interface to the film surface. In contrast, at x = 0.25, Mn became enriched towards the surface and a secondary nano-scale phase formed which appeared to maintain the basic rutile structure but with enhanced z-contrast in the tunnels, or tetrahedral interstitial sites. Ab initio thermodynamic calculations provided quantitative estimates for the destabilizing effect of expanding the β-MnO2 lattice parameters to those of TiO2-rutile, the stabilizing effect of diluting Mn with increasing Ti concentration, and competing reaction pathways.

  14. Research on macro- and microsegregation in semiconductor crystals grown from the melt under the direction of August F. Witt at the Massachusetts Institute of Technology

    Science.gov (United States)

    Wang, C. A.; Carlson, D.; Motakef, S.; Wiegel, M.; Wargo, M. J.

    2004-03-01

    The birth of the modern age of semiconductor electronics in the 1950s required the production of single crystals from the melt. In the early years of this technology, crystals exhibited non-uniform distributions of chemical and structural defects, which directly affected devices produced from this material. Uniform distribution and control of dopants, unintentional impurities, and native defects were identified as critical requirements for continued advances in device technology. However, since at that time fundamental understanding of cause and effect relationships between crystal growth parameters and the ultimate properties of the materials produced was absent, such desirable properties were unattainable. Nevertheless, it was recognized that segregation plays a key role in the creation of non-uniformities. Macrosegregation, a consequence of the directional solidification process, is generally controlled by diffusion and convective melt flows. Microsegregation is governed by local perturbations at the crystal-melt interface. Time-dependent thermal and melt velocity fields at the crystal-melt interface impact the microscopic rate of growth and the solute diffusion boundary layer. Identification of the fundamental parameters that govern axial and radial macro- and microsegregation during bulk semiconductor crystal growth was the research focus during the early years. Key contributions were made by Prof. August F. Witt and his research group. One of the major contributions was the development of quantitative analytical tools for characterization of the crystal growth process. These tools provided the foundation for understanding the origin and nature of segregation phenomena during crystal growth from the melt. This paper is a brief review of his work.

  15. 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 ...

  16. Characterization of CdTe nuclear detectors for gamma radiation spectrometry

    International Nuclear Information System (INIS)

    Rebondy, Jacques.

    1977-01-01

    The crystallography of CdTe is presented. The characterization of CdTe crystals manufactured at LETI was studied using a spectrometry unit, and an experimental study of surface states and contacts was simultaneously undertaken. A manufacturing process was perfected for the detectors: hand polishing and deposit of a drop of conducting lac. Measurements mode on a great number of materials revealed the interest of chlore doping, the polarization phenomenon associated (the polarization is equivalent to a voltage drop and depends on temperature), the effect of surface states and contacts. It was shown that magnesium doping is a failure and the polarization time constant has a value of about 1 msec. An electron time-of-flight experiment was performed in order to measure the mobilities in the sample at normal temperature: the values obtained are: 70-90 cm 2 /v.sec for holes and 800-1000 cm 2 /v.sec for electrons. A trapping level was observed at 0.14eV in a Cl - doped sample; trapping parameters were estimated for a few samples [fr

  17. Characterization inconsistencies in CdTe and CZT gamma-ray detectors

    International Nuclear Information System (INIS)

    Lavietes, A.D.; McQuaid, J.H.

    1994-10-01

    In the past few years, significant developments in cadmium telluride (CdTe) and cadmium zinc telluride (CZT) semiconductor materials have taken place with respect to both quality and yield. Many of the more recent developments have occurred in the area of CZT crystal growth. This has resulted in an explosion of interest in the use of these materials in ambient temperature gamma-ray detectors. Most, if not all, of the manufacturers of CdTe and CZT have acquired government funding to continue research in development and applications, indicating the importance of these improvements in material quality. We have examined many detectors, along with the accompanying manufacturer's data, and it has become apparent that a clear standard does not exist by which each manufacturer characterizes the performance of their material. Result is a wide variety of performance claims that have no basis for comparison and normally cannot be readily reproduced. This paper first supports our observations and then proposes a standard that all manufacturers and users of these materials may use for characterization

  18. Atomic-resolution study of dislocation structures and interfaces in poly-crystalline thin film CdTe using aberration-corrected STEM

    Science.gov (United States)

    Paulauskas, Tadas; Colegrove, Eric; Buurma, Chris; Kim, Moon; Klie, Robert

    2014-03-01

    Commercial success of CdTe-based thin film photovoltaic devices stems from its nearly ideal direct band gap which very effectively couples to Sun's light spectrum as well as ease of manufacturing and low cost of these modules. However, to further improve the conversion efficiency beyond 20 percent, it is important to minimize the harmful effects of grain boundaries and lattice defects in CdTe. Direct atomic-scale characterization is needed in order identify the carrier recombination centers. Likewise, it is necessary to confirm that passivants in CdTe, such as Cl, are able to diffuse and bind to the target defects. In this study, we characterize dislocation structures and grain boundaries in poly-crystalline CdTe using aberration-corrected cold-field emission scanning transmission electron microscopy (STEM). The chemical composition of Shockley partial, Frank and Lomer-Cottrell dislocations is examined via atomic column-resolved X-ray energy dispersive (XEDS) and electron energy-loss spectroscopies (EELS). Segregation of Cl towards dislocation cores and grain boundaries is shown in CdCl2 treated samples. We also investigate interfaces in ultra-high-vacuum bonded CdTe bi-crystals with pre-defined misorientation angles which are intended to mimic grain boundaries. Funded by: DOE EERE Sunshot Award EE0005956.

  19. 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.

  20. Single-Crystal Thin Films of Cesium Lead Bromide Perovskite Epitaxially Grown on Metal Oxide Perovskite (SrTiO3).

    Science.gov (United States)

    Chen, Jie; Morrow, Darien J; Fu, Yongping; Zheng, Weihao; Zhao, Yuzhou; Dang, Lianna; Stolt, Matthew J; Kohler, Daniel D; Wang, Xiaoxia; Czech, Kyle J; Hautzinger, Matthew P; Shen, Shaohua; Guo, Liejin; Pan, Anlian; Wright, John C; Jin, Song

    2017-09-27

    High-quality metal halide perovskite single crystals have low defect densities and excellent photophysical properties, yet thin films are the most sought after material geometry for optoelectronic devices. Perovskite single-crystal thin films (SCTFs) would be highly desirable for high-performance devices, but their growth remains challenging, particularly for inorganic metal halide perovskites. Herein, we report the facile vapor-phase epitaxial growth of cesium lead bromide perovskite (CsPbBr 3 ) continuous SCTFs with controllable micrometer thickness, as well as nanoplate arrays, on traditional oxide perovskite SrTiO 3 (100) substrates. Heteroepitaxial single-crystal growth is enabled by the serendipitous incommensurate lattice match between these two perovskites, and overcoming the limitation of island-forming Volmer-Weber crystal growth is critical for growing large-area continuous thin films. Time-resolved photoluminescence, transient reflection spectroscopy, and electrical transport measurements show that the CsPbBr 3 epitaxial thin film has a slow charge carrier recombination rate, low surface recombination velocity (10 4 cm s -1 ), and low defect density of 10 12 cm -3 , which are comparable to those of CsPbBr 3 single crystals. This work suggests a general approach using oxide perovskites as substrates for heteroepitaxial growth of halide perovskites. The high-quality halide perovskite SCTFs epitaxially integrated with multifunctional oxide perovskites could open up opportunities for a variety of high-performance optoelectronics devices.

  1. Inclusion free cadmium zinc tellurium and cadmium tellurium crystals and associated growth method

    Science.gov (United States)

    Bolotnikov, Aleskey E [South Setauket, NY; James, Ralph B [Ridge, NY

    2010-07-20

    The present disclosure provides systems and methods for crystal growth of cadmium zinc tellurium (CZT) and cadmium tellurium (CdTe) crystals with an inverted growth reactor chamber. The inverted growth reactor chamber enables growth of single, large, high purity CZT and CdTe crystals that can be used, for example, in X-ray and gamma detection, substrates for infrared detectors, or the like. The inverted growth reactor chamber enables reductions in the presence of Te inclusions, which are recognized as an important limiting factor in using CZT or CdTe as radiation detectors. The inverted growth reactor chamber can be utilized with existing crystal growth techniques such as the Bridgman crystal growth mechanism and the like. In an exemplary embodiment, the inverted growth reactor chamber is a U-shaped ampoule.

  2. Crystal structure of (110) oriented La0.7Sr0.3MnO3 grown on (001) silicon

    International Nuclear Information System (INIS)

    Sinha, Umesh Kumar; Sahoo, Antarjami; Padhan, Prahallad

    2016-01-01

    The mixed valance perovskite manganites have attracted a considerable attention due to their colossal magnetoresistance behavior. In particular, La 0.7 Sr 0.3 MnO 3 (LSMO) show half metallicity and possess Curie temperature (T C ) above room temperature, which makes this material an attractive candidate for spintronic device application. Thin films of LSMO were grown on (001) oriented Silicon (Si) using sputtering technique

  3. Luminescence properties of pure and Eu-doped SrI{sub 2} crystals purified by a “Liquinert” process and grown by vertical Bridgman method

    Energy Technology Data Exchange (ETDEWEB)

    Kawai, Taketoshi, E-mail: buri@p.s.osakafu-u.ac.jp [Osaka Prefecture University, Gakuen-cho 1-1, Naka-ku, Sakai, Osaka 599-8531 (Japan); Sakuragi, Shiro; Hashimoto, Satoshi [Union Materials Inc. 1640 Oshido, Tone-machi, Ibaraki 300-1602 (Japan)

    2016-08-15

    We have prepared high quality crystals of pure SrI{sub 2} and Eu-doped SrI{sub 2} by our original “Liquinert” process and investigated their luminescence properties. Under the excitation with the 193 nm light of an ArF excimer laser, which corresponds to the wavelength above the bandgap of SrI{sub 2} bulk crystals, the pure and Eu doped SrI{sub 2} crystals exhibit no luminescence band related to defects or impurities around 560 nm. This fact indicates that the crystals prepared by the “Liquinert” process contain lower defects and/or impurities. When the Eu-doped SrI{sub 2} crystals are excited with the 325 nm light of a He–Cd laser, only the luminescence band due to the 5d→4f transition in the Eu{sup 2+} ions is observed around 425 nm. The 425 nm band observed at a forward configuration exhibits the shift to the longer wavelength side and the decrease of the luminescence intensity with increasing Eu concentration. The Eu concentration dependences of the peak wavelength and luminescence intensity are simulated on the basis of a simple self-absorption model. - Highlights: • Our original “Liquinert” process allows us to prepare high quality crystals of SrI{sub 2}. • No luminescence band related with impurities and/or defects is observed. • The 425 nm luminescence bands due to Eu{sup 2+} ions are affected by a self-absorption. • A simple self-absorption model reproduces the changes of the 425 nm bands.

  4. 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.

  5. Aragonite crystals grown on bones by reaction of CO2 with nanostructured Ca(OH)2 in the presence of collagen. Implications in archaeology and paleontology.

    Science.gov (United States)

    Natali, Irene; Tempesti, Paolo; Carretti, Emiliano; Potenza, Mariangela; Sansoni, Stefania; Baglioni, Piero; Dei, Luigi

    2014-01-21

    The loss of mechanical properties affecting archeological or paleontological bones is often caused by demineralization processes that are similar to those driving the mechanisms leading to osteoporosis. One simple way to harden and to strengthen demineralized bone remains could be the in situ growth of CaCO3 crystals in the aragonite polymorph - metastable at atmospheric pressure -which is known to have very strong mechanical strength in comparison with the stable calcite. In the present study the controlled growth of aragonite crystals was achieved by reaction between atmospheric CO2 and calcium hydroxide nanoparticles in the presence of collagen within the deteriorated bones. In a few days the carbonation of Ca(OH)2 particles led to a mixture of calcite and aragonite, increasing the strength of the mineral network of the bone. Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS) and Fourier transform infrared (FT-IR) spectrometry showed that aragonite crystallization was achieved. The effect of the aragonite crystal formation on the mechanical properties of the deteriorated bones was investigated by means of X-rays microtomography, helium porosimetry, atomic force microscopy (AFM), and Vickers microhardness techniques. All these data enabled to conclude that the strength of the bones increased of a factor of 50-70% with respect to the untreated bone. These results could have immediate impact for preserving archeological and paleontological bone remains.

  6. CoV2O6 single crystals grown in a closed crucible: unusual magnetic behaviors with large anisotropy and 1/3 magnetization plateau.

    Science.gov (United States)

    He, Zhangzhen; Yamaura, Jun-ichi; Ueda, Yutaka; Cheng, Wendan

    2009-06-10

    Single crystals of CoV(2)O(6) were obtained in a closed crucible using a flux method. Magnetic measurements showed that this material displays a large magnetic anisotropy and a 1/3 magnetization plateau under a magnetic field applied along the c axis.

  7. 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

  8. Magnetic properties of vanadium doped CdTe: Ab initio calculations

    Energy Technology Data Exchange (ETDEWEB)

    Goumrhar, F. [Laboratory of Physics of High Energy, Modeling & Simulations (LPHE-MS), Faculty of Sciences, Mohammed V University of Rabat, Av. Ibn Batouta, B.P. 1014 Rabat (Morocco); Bahmad, L., E-mail: bahmad@fsr.ac.ma [Laboratory of Magnetism and High Energy Physics (LMPHE-URAC12), Faculty of Sciences, Mohammed V University of Rabat, Av. Ibn Batouta, B.P. 1014 Rabat (Morocco); Mounkachi, O. [Material and Nanomaterial Center, MAScIR Fondation, Rabat (Morocco); Benyoussef, A. [Laboratory of Magnetism and High Energy Physics (LMPHE-URAC12), Faculty of Sciences, Mohammed V University of Rabat, Av. Ibn Batouta, B.P. 1014 Rabat (Morocco); Material and Nanomaterial Center, MAScIR Fondation, Rabat (Morocco); Hassan II Academy of Sciences and Technology, Rabat (Morocco)

    2017-04-15

    In this paper, we are applying the ab initio calculations to study the magnetic properties of vanadium doped CdTe. This study is based on the Korringa–Kohn–Rostoker method (KKR) combined with the coherent potential approximation (CPA), within the local density approximation (LDA). This method is called KKR-CPA-LDA. We have calculated and plotted the density of states (DOS) in the energy diagram for different concentrations of dopants. We have also investigated the magnetic and half-metallic properties of this compound and shown the mechanism of exchange interaction. Moreover, we have estimated the Curie temperature T{sub c} for different concentrations. Finally, we have shown how the crystal field and the exchange splittings vary as a function of the concentrations.

  9. Pulse electron beam-induced synthesis of CdTe printed films

    International Nuclear Information System (INIS)

    Houng, M.P.; Fu, S.L.; Wu, T.S.; Leu, J.T.; Cheng, K.Y.

    1987-01-01

    In an attempt to produce a high quality single crystal CdTe film with enhanced electrical properties, screen printed Cd + Te films were prepared on an aluminium oxide substrate and then irradiated with a pulsed electron beam over the energy range 12-15 KeV. Some samples were also vacuum annealed from 410-620 0 C after irradiation. The films were characterized by x-ray diffraction, scanning electron microscopy and photoluminescence. This showed that film quality and uniformity were limited by electron beam heating, although improvements can be made by vacuum annealing. Furthermore, only polycrystalline films were produced, possibly due to a too short pulse duration and the use of a polycrystalline substrate. (U.K.)

  10. 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.

  11. A multiple p-n junction structure obtained from as-grown Czochralski silicon crystals by heat treatment - Application to solar cells

    Science.gov (United States)

    Chi, J. Y.; Gatos, H. C.; Mao, B. Y.

    1980-01-01

    Multiple p-n junctions have been prepared in as-grown Czochralski p-type silicon through overcompensation near the oxygen periodic concentration maxima by oxygen thermal donors generated during heat treatment at 450 C. Application of the multiple p-n-junction configuration to photovoltaic energy conversion has been investigated. A new solar-cell structure based on multiple p-n-junctions was developed. Theoretical analysis showed that a significant increase in collection efficiency over the conventional solar cells can be achieved.

  12. Research Update: Point defects in CdTe{sub x}Se{sub 1−x} crystals grown from a Te-rich solution for applications in detecting radiation

    Energy Technology Data Exchange (ETDEWEB)

    Gul, R.; Roy, U. N.; Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; Hossain, A.; Yang, G.; James, R. B. [Brookhaven National Laboratory, Upton, New York 11973 (United States); Lee, W. [Korea University, Seoul 136-701 (Korea, Republic of); Cui, Y.; Burger, A. [Fisk University, Nashville, Tennessee 37208 (United States)

    2015-04-01

    We investigated cadmium telluride selenide (CdTeSe) crystals, newly grown by the Traveling Heater Method (THM), for the presence and abundance of point defects. Current Deep Level Transient spectroscopy (I-DLTS) was used to determine the energies of the traps, their capture cross sections, and densities. The bias across the detectors was varied from 1 to 30 V. Four types of point defects were identified, ranging from 10 meV to 0.35 eV. Two dominant traps at energies of 0.18 eV and 0.14 eV were studied in depth. Cd vacancies are found at lower concentrations than other point defects present in the material.

  13. 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.

  14. Pressure cryocooling protein crystals

    Science.gov (United States)

    Kim, Chae Un [Ithaca, NY; Gruner, Sol M [Ithaca, NY

    2011-10-04

    Preparation of cryocooled protein crystal is provided by use of helium pressurizing and cryocooling to obtain cryocooled protein crystal allowing collection of high resolution data and by heavier noble gas (krypton or xenon) binding followed by helium pressurizing and cryocooling to obtain cryocooled protein crystal for collection of high resolution data and SAD phasing simultaneously. The helium pressurizing is carried out on crystal coated to prevent dehydration or on crystal grown in aqueous solution in a capillary.

  15. Applicability of a portable CdTe and NaI (Tl) spectrometer for activity measure

    International Nuclear Information System (INIS)

    Fernandes, Jaquiel Salvi

    2005-02-01

    In this work it was studied the application of an in situ gamma spectrometer (ROVER) of Amptek Inc., composed by a Cadmium Telluride detector (CdTe) of 3 mm x 3 mm x 1 mm and a 30 mm x 30 mm Sodium Iodide detector doped with Thallium [NaI (Tl)). The radioactive sources used were type pastille, sealed in aluminum and polyethylene, of 241 Am, 133 Ba, 152 Eu, 3 sources of 137 Cs and soil samples contaminated with 137 Cs. It was performed a factorial planning 2 3 to optimize the in situ spectrometry system. This way it was determined that the best temperature for CdTe crystal operation is -22, deg C, with Shaping Time of 3 μS and Rise Time Discrimination (RTD) with value 3. With the help of the certified radioactive sources, we determined the efficiency curve of the two detectors. The CdTe detector was positioned at the standard distance of 1 meter of the sources and also at 4.15 cm. The NaI (Tl) detector was also positioned at the standard distance of 1 meter of the sources and at 2.8 cm. Measures were performed to determine the Minimum Detectable Activity (MDA) for both detectors. For the pastille type sources, the 137 Cs MDA for the CdTe detector at 4.15 cm, analyzing the energy line of 32 keV, was 6 kBq and at 1 meter of the 137 Cs source, analyzing the line of 661.65 keV, the MDA was 67 kBq. For soil samples, CdTe detector at 4.15 cm presented a MDA of 693 kBq.kg-l for the line of 32 keV, and for the soil sample 7 Be content the MDA found was 2867 Bq.kg -1 at 4.15 cm. For the NaI (Tl) detector, analyzing the line of 661.65 keV, the 137 Cs MDA for pastille type source at 1 meter of distance was 7 kBq, and for soil sample at 2.8 cm the measured 137 Cs MDA was 71 Bq.kg -1 . For the soil sample 7 Be content, at 2.8 cm of the Nal (Tl) detector, the obtained MDA was 91 Bq.kg -1 . Due to the minimum detectable activities found for the two detectors, we concluded that the employed in situ gamma ray spectrometer system allows the quantification of 137 Cs and 7 Be

  16. 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

  17. Protein Crystal Recombinant Human Insulin

    Science.gov (United States)

    1994-01-01

    The comparison of protein crystal, Recombiant Human Insulin; space-grown (left) and earth-grown (right). On STS-60, Spacehab II indicated that space-grown crystals are larger and of greater optical clarity than their earth-grown counterparts. Recombiant Human Insulin facilitates the incorporation of glucose into cells. In diabetics, there is either a decrease in or complete lack of insulin, thereby leading to several harmful complications. Principal Investigator is Larry DeLucas.

  18. Yb:Lu{sub 2}O{sub 3} hydrothermally-grown single-crystal and ceramic absorption spectra obtained between 298 and 80 K

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Cheryl A. [Snake Creek Lasers LLC, 26741 State Route 267, Friendsville, PA 18818 (United States); Department of Chemistry and Center for Optical Materials Science and Engineering Technologies, Clemson University, Clemson, SC 29634-0973 (United States); Brown, David C., E-mail: dbrown@snakecreeklasers.com [Snake Creek Lasers LLC, 26741 State Route 267, Friendsville, PA 18818 (United States); Sanjeewa, Liurukara D.; McMillen, Colin D.; Kolis, Joseph W. [Department of Chemistry and Center for Optical Materials Science and Engineering Technologies, Clemson University, Clemson, SC 29634-0973 (United States)

    2016-06-15

    The hydrothermal growth, doping, and low temperature spectral characterization of Yb doped Lu{sub 2}O{sub 3} was investigated. The absorption of the lutetia-based sesquioxide laser material Yb:Lu{sub 2}O{sub 3} at temperatures of 80, 150, 200, 250, and 298 K, in the wavelength range of 850–1100 nm are reported. Data for both single crystal and ceramic Yb:Lu{sub 2}O{sub 3} were obtained. The resulting absorption cross-section data will enable the further evaluation of Yb:Lu{sub 2}O{sub 3} as a very promising high power cryogenic laser material.

  19. 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

  20. Preparation and purification of L-cysteine capped CdTe quantum dots and its self-recovery of degenerate fluorescence

    International Nuclear Information System (INIS)

    Li Mengying; Zhou Huameng; Zhang Hongyan; Sun Pan; Yi Kuiyu; Wang Meng; Dong Zaizheng; Xu Shukun

    2010-01-01

    L-cysteine capped CdTe quantum dots (QDs) were prepared in aqueous solution by a simple and efficient method, showing many advantages such as short synthesis period, the broaden range of starting pH value and the wide fluorescence emission wavelength range. A novel purification process was designed to remove excess Cd 2+ which has potential cytotoxicity for bio-analysis. Three-dimensional fluorescence charts of pre- and post-purification showed that the purified QDs were of better luminescent performance. The prepared QDs were of cubic crystal structure with an average size of 2-6 nm, which were characterized by XRD and HRTEM. It is confirmed by IR spectra that the L-cysteine ligands were conjugated with CdTe cores via covalent bond. The degenerate fluorescence of QDs can be self-recovered in the presence of L-cysteine without other processing steps.

  1. Growth of 2-amino-5-chlorobenzophenone single crystal by ...

    Indian Academy of Sciences (India)

    Abstract. Organic single crystals of 2-amino-5-chlorobenzophenone (2A5CB) were grown by Microtube Czochral- ski method using Microtube as a seed. The grown crystals were characterized by single crystal and powder X-ray diffraction. The functional groups of the grown crystal were found using Fourier transform ...

  2. Enhanced light extraction of InGaN LEDs with photonic crystals grown on p-GaN using selective-area epitaxy and nanospherical-lens photolithography

    International Nuclear Information System (INIS)

    Zhao Linghui; Wei Tongbo; Wang Junxi; Zeng Yiping; Li Jinmin; Yan Qingfeng

    2013-01-01

    We report a new method for the fabrication of two-dimensional photonic crystal (PhC) hole arrays to improve the light extraction of GaN-based light-emitting diodes (LEDs). The PhC structures were realized using nanospherical-lens photolithography and the selective-area epitaxy method, which ensured the electrical properties of the LEDs through leaving the p-GaN damage-free. At a current of 350 mA, the light output power of LEDs with PhC hole arrays of 450 nm and 600 nm in diameter with the same lattice period of 900 nm were enhanced by 49.3% and 72.2%, respectively, compared to LEDs without a PhC. Furthermore, the LEDs with PhC hole structures showed an obviously smaller divergent angle compared with conventional LEDs, which is consistent with the results of finite-difference time-domain simulation. (semiconductor devices)

  3. 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.

  4. 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.

  5. Controlling of hydrogen and oxygen atoms in CdTe by means of far-infrared spectroscopy using synchrotron radiation

    International Nuclear Information System (INIS)

    Cebulski, J.; Sheregii, E.M.; Polit, J.; Marcelli, A.; Robouch, B.; Castelli Gudi, M.; Piccinini, M.; Kisiel, A.

    2007-01-01

    The work presents far-and middle-infrared reflectivity spectra collected with synchrotron radiation on specially prepared CdTe-monocrystals in the temperature region of 30-300 K. The investigated samples were of three different types characterized by the three different levels of hydrogenation - strong, middle and the low ones. In order to interpret the experimental data, the imaginary part of the dielectric function was evaluated by means of Kramers-Kronig transformation. To determine quantitatively the influence of hydrogen atoms on the phonon and vibrational spectra of hydrogenated CdTe crystals we used the special statistical model proposed in this paper. This model takes into account the tetrahedron as the basic structural unit and distinguishes the contribution of the hydrogen bearing tetrahedra from the contribution of the hydrogen free ones to the crystal phonon spectra. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Growth of ZnO nanowires through thermal oxidation of metallic zinc films on CdTe substrates

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, O., E-mail: oscar@fmc.uva.es [Optronlab Group, Dpto. Fisica Materia Condensada, Edificio I-D, Universidad de Valladolid, Paseo de Belen 1, 47011, Valladolid (Spain); Hortelano, V.; Jimenez, J. [Optronlab Group, Dpto. Fisica Materia Condensada, Edificio I-D, Universidad de Valladolid, Paseo de Belen 1, 47011, Valladolid (Spain); Plaza, J.L.; Dios, S. de; Olvera, J.; Dieguez, E. [Laboratorio de Crecimiento de Cristales, Departamento de Fisica de Materiales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Fath, R.; Lozano, J.G.; Ben, T.; Gonzalez, D. [Dpto. Ciencia de los Materiales e Ingenieria Metalurgica y Q.I., Facultad de Ciencias, Apdo. 40, 11510 Puerto Real, Cadiz (Spain); Mass, J. [Dpto. de Fisica, Universidad del Norte, Km.5 Via Puerto Colombia, Barranquilla (Colombia)

    2011-04-28

    Research highlights: > ZnO nanowires grown from thermal Zn oxidation. > TEM reveals high quality thin nanowires several microns long. > New phase formation at long oxidation time. > Good spectroscopic properties measured by Raman, Photo and Cathodoluminsecence spectroscopies. - Abstract: <112-bar 0> wurtzite ZnO nanowires (NWs) have been obtained by oxidizing in air at 500 deg. C thermally evaporated Zn metal films deposited onto CdTe substrates. The presence of Cd atoms from the substrate on the ZnO seeding layer and NWs seems to affect the growth of the NWs. The effects of the oxidation time on the structural and optical properties of the NWs are described in detail. It is shown that the NWs density decreases and their length increases when increasing the oxidation time. Thicker Zn layers result in thinner and longer ZnO NWs. Very long oxidation times also lead to the formation of a new CdO phase which is related to the partial destruction and quality reduction of the NWs. The possible process for ZnO NW formation on CdTe substrates is discussed.

  7. 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.

  8. Charge collection efficiency and space charge formation in CdTe gamma and X-ray detectors

    International Nuclear Information System (INIS)

    Matz, R.; Weidner, M.

    1998-01-01

    A new extended model for the charge collection efficiency in CdTe gamma and X ray detectors is presented which allows to derive from apparent experimental gamma spectra of a quasi-monochromatic source, an 241 Am source in the present case, not only the μτ products of electrons and holes individually but also the sign, spatial distribution, and temporal evolution of the net space charge accumulated in the detector. Resistive CdTe and CdZnTe as well as CdTe Schottky detectors are studied. While the resistive type is stable in time and exhibits higher μτ products, the Schottky type shows space charge accumulation which approaches saturation after about 1 h at several 10 11 cm -3 . This is attributed to efficient majority carrier depletion, Fermi level shift, and trap filling. Resistive detectors thus appear optimized to the needs of gamma spectroscopy even at low bias voltage, while Schottky types need higher bias to overcome the space charge. They are suited to both, gamma spectroscopy and X-ray detection in analog current mode, where they operate more stably due to the higher bias. From the point of view of materials characterization, gamma spectroscopy with Schottky detectors probes and reveals the trap density near the Fermi level (several 10 12 cm -3 eV -1 ). We find a basically homogeneous spatial distribution suggesting the trap origin being in crystal growth rather than surface processing. Capture of photogenerated charges in traps is detrimental for current-mode operation under high X-ray flux because delayed emission from traps limits the detector''s ability to respond to fast signal changes. (orig.)

  9. 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.

  10. Morphology of Diamond Layers Grown on Different Facets of Single Crystal Diamond Substrates by a Microwave Plasma CVD in CH4-H2-N2 Gas Mixtures

    Directory of Open Access Journals (Sweden)

    Evgeny E. Ashkinazi

    2017-06-01

    Full Text Available Epitaxial growth of diamond films on different facets of synthetic IIa-type single crystal (SC high-pressure high temperature (HPHT diamond substrate by a microwave plasma CVD in CH4-H2-N2 gas mixture with the high concentration (4% of nitrogen is studied. A beveled SC diamond embraced with low-index {100}, {110}, {111}, {211}, and {311} faces was used as the substrate. Only the {100} face is found to sustain homoepitaxial growth at the present experimental parameters, while nanocrystalline diamond (NCD films are produced on other planes. This observation is important for the choice of appropriate growth parameters, in particular, for the production of bi-layer or multilayer NCD-on-microcrystalline diamond (MCD superhard coatings on tools when the deposition of continuous conformal NCD film on all facet is required. The development of the film morphology with growth time is examined with SEM. The structure of hillocks, with or without polycrystalline aggregates, that appear on {100} face is analyzed, and the stress field (up to 0.4 GPa within the hillocks is evaluated based on high-resolution mapping of photoluminescence spectra of nitrogen-vacancy NV optical centers in the film.

  11. Infrared optical characterization and energy transfer of Na5Lu9F32 single crystals co-doped with Er3+/Tm3+ grown by Bridgman method

    Science.gov (United States)

    Tang, Qingyang; Xia, Haiping; He, Shinan; Sheng, Qiguo; Chen, Baojiu

    2017-11-01

    This paper reported on successful preparation of Na5Lu9F32 single crystals co-doped with ∼2 mol% Er3+ and various Tm3+ concentrations from 0.7 mol% to 3.2 mol% by Bridgman method. The J-O intensity parameters of Er3+ were calculated and analyzed according to the absorption spectra. The fluorescence decay curve at Er3+:4I13/2 level was measured to investigate the luminescent properties of the Er3+/Tm3+ co-doped Na5Lu9F32, and the energy transfer process between Er3+ and Tm3+. An intense 2.7 μm emission was achieved with Tm3+ ions sensitizing Er3+ ions under the 800 nm LD pumping. The maximum emission intensity at 2.7 μm was obtained at about 3.2 mol% doping concentration of Tm3+ when the concentration of Er3+ ions was fixed at ∼2 mol% in the current research. The calculated maximum value of emission cross section at 2.7 μm was 2.22 × 10-20 cm2, and energy transfer efficiency from Er3+:4I13/2 to Tm3+:3F4 was 78%. The electric dipole-dipole interaction was dominant for the energy transfer from Er3+ to Tm3+ ions by using Inokuti-Hirayama's model.

  12. 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

  13. Growth and characterisation of lead iodide single crystals

    International Nuclear Information System (INIS)

    Tonn, Justus

    2012-01-01

    The work in hand deals with the growth and characterisation of lead iodide (PbI 2 ) single crystals. PbI 2 is regarded as a promising candidate for low-noise X- and gamma ray detection at room temperature. Its benefits if compared to conventional materials like HgI 2 , CdTe, Si, or GaAs lie in a band gap energy of 2.32 eV, an excellent ability to absorb radiation, and a high electrical resistivity. For an application of PbI 2 as detector material the growth and characterisation of crystals with high chemical and structural quality is extremely challenging. In light of this, the effectiveness of zone purification of the PbI 2 used for crystal growth was confirmed by spectroscopic analysis. Furthermore, technological aspects during processing of purified PbI 2 were investigated. With the help of thermal analysis, a correlation was found between the degree of exposing the source material to oxygen from the air and the structural quality of the resulting crystals. A hydrogen treatment was applied to PbI 2 as an effective method for the removal of oxidic pollutions, which resulted in a significant reduction of structural defects like polytypic growth and stress-induced cracking. The growth of PbI 2 single crystals was, among others, carried out by the Bridgman-Stockbarger method. In this context, much effort was put on the investigation of influences resulting from the design and preparation of ampoules. For the first time, crystal growth of PbI 2 was also carried out by the Czochralski method. If compared to the Bridgman-Stockbarger method, the Czochralski technique allowed a significantly faster growth of nearly crack-free crystals with a reproducible predetermination of crystallographic orientation. By an optimised sample preparation of PbI 2 , surface orientations perpendicular to the usually cleaved (0001) plane were realised. It is now possible to determine the material properties along directions which were so far not accessible. Thus, for example, the ratio of

  14. Single-Crystal Bismuth Iodide Gamma-Ray Spectrometers

    Science.gov (United States)

    2012-02-01

    band gap of 1.730 ± 0.005 eV.52-53 Jellison eta/. used two- modulator generalized ellipsometry to determine ordinary and extraordinary band gaps of 1.991...quality is not comparable to the commercial CdTe and CZT crystals. While the material was observed to be sensitive to radiation (alphas, gamma-rays, and...simulation of CdTe vertical Bridgman growth," J. Cryst. Growth, 173 [3-4] 352-366 (1997). 50 16.A. Bachran, P. Reinshaus, and W. Seifert, "Influence

  15. Hard X-ray polarimetry with Caliste, a high performance CdTe based imaging spectrometer

    Science.gov (United States)

    Antier, S.; Ferrando, P.; Limousin, O.; Caroli, E.; Curado da Silva, R. M.; Blondel, C.; Chipaux, R.; Honkimaki, V.; Horeau, B.; Laurent, P.; Maia, J. M.; Meuris, A.; Del Sordo, S.; Stephen, J. B.

    2015-06-01

    Since the initial exploration of the X- and soft γ-ray sky in the 60's, high-energy celestial sources have been mainly characterized through imaging, spectroscopy and timing analysis. Despite tremendous progress in the field, the radiation mechanisms at work in sources such as neutrons stars, black holes, and Active Galactic Nuclei are still unclear. The polarization state of the radiation is an observational parameter which brings key additional information about the physical processes in these high energy sources, allowing the discrimination between competing models which may otherwise all be consistent with other types of measurement. This is why most of the projects for the next generation of space missions covering the few tens of keV to the MeV region require a polarization measurement capability. A key element enabling this capability, in this energy range, is a detector system allowing the identification and characterization of Compton interactions as they are the main process at play. The compact hard X-ray imaging spectrometer module, developed in CEA with the generic name of "Caliste" module, is such a detector. In this paper, we present experimental results for two types of Caliste-256 modules, one based on a CdTe crystal, the other one on a CdZnTe crystal, which have been exposed to linearly polarized beams at the European Synchrotron Radiation Facility (ESRF). These results, obtained at 200 and 300 keV, demonstrate the capability of these modules to detect Compton events and to give an accurate determination of the polarization parameters (polarization angle and fraction) of the incoming beam. For example, applying an optimized selection to our data set, equivalent to select 90° Compton scattered interactions in the detector plane, we find a modulation factor Q of 0.78 ± 0.06 in the 200-300 keV range. The polarization angle and fraction are derived with accuracies of approximately 1° and 5 % respectively for both CdZnTe and CdTe crystals. The

  16. Large-area single-crystal graphene grown on a recrystallized Cu(111) surface by using a hole-pocket method

    Science.gov (United States)

    Phan, Hoang Danh; Jung, Jaehyuck; Kim, Youngchan; Huynh, Van Ngoc; Lee, Changgu

    2016-07-01

    We describe an efficient chemical vapor deposition (CVD) method for synthesizing graphene with a single crystal orientation on the whole surface of a copper (Cu) foil. We specifically synthesized graphene on the inner surface of a folded Cu foil, on which small holes were made for regulating the permeation and adsorption of the gases used for the synthesis. We compared the results of this method, which we call a ``hole-pocket'' method, with previously developed methods involving traditional synthesis on an open Cu foil and a Cu ``pita-pocket''. From these comparisons, we found the orientation of recrystallized Cu to depend on the shape of the Cu foil. Our hole-pocket method did not require treatment of the Cu surface with a complicated process to reduce the density of nucleation seeds in order to synthesize large hexagonal graphene grains, nor did it require the use of a single-crystalline substrate because methane passing through holes on the upper side of the hole-pocket slowly decomposed into carbon atoms and the control of the evaporation of Cu inside the foil pocket helped induce a transformation of the Cu domains to Cu(111). The current hole-pocket method resulted in domains that were both large, ranging from 2-5 mm in size, and oriented in the same manner. By extending the synthesis time, we were able to obtain continuous large-area films of single-crystalline orientation on the whole surface with dimensions of several centimeters.We describe an efficient chemical vapor deposition (CVD) method for synthesizing graphene with a single crystal orientation on the whole surface of a copper (Cu) foil. We specifically synthesized graphene on the inner surface of a folded Cu foil, on which small holes were made for regulating the permeation and adsorption of the gases used for the synthesis. We compared the results of this method, which we call a ``hole-pocket'' method, with previously developed methods involving traditional synthesis on an open Cu foil and a Cu

  17. 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.

  18. 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.

  19. 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

  20. Imaging performance comparison between a LaBr3: Ce scintillator based and a CdTe semiconductor based photon counting compact gamma camera.

    Science.gov (United States)

    Russo, P; Mettivier, G; Pani, R; Pellegrini, R; Cinti, M N; Bennati, P

    2009-04-01

    The authors report on the performance of two small field of view, compact gamma cameras working in single photon counting in planar imaging tests at 122 and 140 keV. The first camera is based on a LaBr3: Ce scintillator continuous crystal (49 x 49 x 5 mm3) assembled with a flat panel multianode photomultiplier tube with parallel readout. The second one belongs to the class of semiconductor hybrid pixel detectors, specifically, a CdTe pixel detector (14 x 14 x 1 mm3) with 256 x 256 square pixels and a pitch of 55 microm, read out by a CMOS single photon counting integrated circuit of the Medipix2 series. The scintillation camera was operated with selectable energy window while the CdTe camera was operated with a single low-energy detection threshold of about 20 keV, i.e., without energy discrimination. The detectors were coupled to pinhole or parallel-hole high-resolution collimators. The evaluation of their overall performance in basic imaging tasks is presented through measurements of their detection efficiency, intrinsic spatial resolution, noise, image SNR, and contrast recovery. The scintillation and CdTe cameras showed, respectively, detection efficiencies at 122 keV of 83% and 45%, intrinsic spatial resolutions of 0.9 mm and 75 microm, and total background noises of 40.5 and 1.6 cps. Imaging tests with high-resolution parallel-hole and pinhole collimators are also reported.

  1. Synchrotron radiation photoemission study of Pb{sub 1−x}Cd{sub x}Te crystal with local structure

    Energy Technology Data Exchange (ETDEWEB)

    Orlowski, B.A.; Szczerbakow, A.; Dziawa, P.; Gas, K.; Reszka, A.; Kowalski, B.J. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Thiess, S.; Drube, W. [Hamburger Synchrotronstrahlungslabor HASYLAB am DESY, Notkestr. 85, D-22603 Hamburg (Germany)

    2015-12-01

    The paper presents photoemission study of core level binding energy shifts caused by local crystalline structure collapse in cubic Pb{sub 1−x}Cd{sub x}Te crystal. Photoemission spectra of two kinds of semiconductor samples are compared. The first one is ternary crystal of Pb{sub 0.94}Cd{sub 0.06}Te with the frozen rock salt structure where the crystalline local structure collapse is expected due to the difference of ion radii of Cd and Pb cations. The second sample was the CdTe(22 nm)/PbTe(6 nm)/CdTe(4 μm)/GaAs(1 1 1)B nanostructure grown by molecular beam epitaxy (MBE) method, where crystalline local structure is not expected to be created. The photoemission spectra show that for the crystal with local structure the electron binding energies of cations are higher (e.g. +0.2 eV) whereas for anions they are lower (e.g. −0.08 eV) than in the multilayer structure. A model is proposed to explain obtained results by the local crystalline structure collapse in Pb{sub 0.94}Cd{sub 0.06}Te crystal.

  2. Hard-X and gamma-ray imaging detector for astrophysics based on pixelated CdTe semiconductors

    Science.gov (United States)

    Gálvez, J.-L.; Hernanz, M.; Álvarez, L.; Artigues, B.; Ullán, M.; Lozano, M.; Pellegrini, G.; Cabruja, E.; Martínez, R.; Chmeissani, M.; Puigdengoles, C.

    2016-01-01

    Stellar explosions are astrophysical phenomena of great importance and interest. Instruments with high sensitivities are essential to perform detailed studies of cosmic explosions and cosmic accelerators. In order to achieve the needed performance, a hard-X and gamma-ray imaging detector with mm spatial resolution and large enough efficiency is required. We present a detector module which consists of a single CdTe crystal of 12.5 × 12.5mm 2 and 2mm thick with a planar cathode and with the anode segmented in an 11x11 pixel array with a pixel pitch of 1 mm attached to the readout chip. Two possible detector module configurations are considered: the so-called Planar Transverse Field (PTF) and the Parallel Planar Field (PPF). The combination of several modules in PTF or PPF configuration will achieve the desired performance of the imaging detector. The sum energy resolution of all pixels of the CdTe module measured at 122 keV and 356 keV is 3.8% and 2% respectively, in the following operating conditions: PPF irradiation, bias voltage -500 V and temperature -10̂ C.

  3. The effects of high temperature processing on the structural and optical properties of oxygenated CdS window layers in CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Paudel, Naba R.; Grice, Corey R.; Xiao, Chuanxiao; Yan, Yanfa [Department of Physics and Astronomy, and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo, Ohio 43606 (United States)

    2014-07-28

    High efficiency CdTe solar cells typically use oxygenated CdS (CdS:O) window layers. We synthesize CdS:O window layers at room temperature (RT) and 270 °C using reactive sputtering. The band gaps of CdS:O layers deposited at RT increase when O{sub 2}/(O{sub 2} + Ar) ratios in the deposition chamber increase. On the other hand, the band gaps of CdS:O layers deposited at 270 °C decrease as the O{sub 2}/(O{sub 2} + Ar) ratios increase. Interestingly, however, our high temperature closed-space sublimation (CSS) processed CdTe solar cells using CdS:O window layers deposited at RT and 270 °C exhibit very similar cell performance, including similar short-circuit current densities. To understand the underlying reasons, CdS:O thin films deposited at RT and 270 °C are annealed at temperatures that simulate the CSS process of CdTe deposition. X-ray diffraction, atomic force microscopy, and UV-visible light absorption spectroscopy characterization of the annealed films reveals that the CdS:O films deposited at RT undergo grain regrowth and/or crystallization and exhibit reduced band gaps after the annealing. Our results suggest that CdS:O thin films deposited at RT and 270 °C should exhibit similar optical properties after the deposition of CdTe layers, explaining the similar cell performance.

  4. Research and development of CdTe based thin film PV solar cells

    Science.gov (United States)

    Diso, Dahiru Garba

    The motivation behind this research is to bring cheap, low-cost and clean energy technologies to the society. Colossal use of fossil fuel has created noticeable pollution problems contributing to climate change and health hazards. Silicon based solar cells have dominated the market but it is cost is high due to the manufacturing process. Therefore, the way forward is to develop thin films solar cells using low-cost attractive materials, grown by cheaper, scalable and manufacturable techniques.The aim and objectives of this work is to develop low-cost, high efficiency solar cell using electrodeposition (ED) technique. The material layers include CdS and ZnTe as the window materials, while the absorber material is CdTe. Fabricating a suitable devices for solar energy conversion (i.e. glass/conducting glass/window material/absorber material/metal) structure. Traditional way of fabricating this structure is to grow window material (CdS) using chemical bath deposition (CBD) and absorber material (CdTe) using electrodeposition. However, CBD is a batch process and therefore creates large volumes of Cd-containing waste solutions each time adding high cost in manufacturing process. This research programme is therefore on development of an "All ED-solar cells" structure.Material studies were carried out using photoelectrochemical (PEC) studies, UV-Vis spectrophotometry, X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Furthermore, the electrical characterisation of fully fabricated devices was performed using current-voltage (I-V) and capacitance-voltage (C-V) measurements.This research programme has demonstrated that CdS and ZnTe window materials can be electrodeposited and used in thin film solar cell devices. The CdS electrolytic bath can be used for a period of 7 months without discarding it like in the CBD process which usually has life

  5. 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 ...

  6. 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.

  7. Synthesis and characterization of electrochemically deposited nanocrystalline CdTe thin films

    International Nuclear Information System (INIS)

    Singh, Ragini Raj; Painuly, Diksha; Pandey, R.K.

    2009-01-01

    Electrodeposition is emerging as a method for the synthesis of semiconductor thin films and nanostructures. In this work we prepared the nanocrystalline CdTe thin films on indium tin oxide coated glass substrate from aqueous acidic bath at the deposition temperature 50 ± 1 deg. C. The films were grown potentiostatically from -0.60 V to -0.82 V with respect to saturated calomel reference electrode. The structural, compositional, morphological and optical properties were investigated using X-ray diffraction (XRD), energy dispersive analysis by X-rays (EDAX), atomic force microscopy (AFM), and UV-vis spectroscopy respectively and cyclic voltammetery. The structural and optical studies revealed that films are nanocrystalline in nature and possess cubic phase, also the films are preferentially oriented along the cubic (1 1 1) plane. The effect of cadmium composition on the deposited morphology was also investigated. The size dependent blue shift in the experimentally determined absorption edge has been compared with the theoretical predictions based on the effective mass approximation and tight binding approximation. It is shown that the experimentally determined absorption edges depart from the theoretically calculated values.

  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. 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.).

  11. 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.

  12. 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

  13. Vibrational Spectral Studies of Pure and Doped TGSP Crystals

    OpenAIRE

    Kartheeswari, N.; Viswanathan, K.

    2013-01-01

    Triglycine sulfate crystals (TGS) are an important class of ferroelectric materials. TGS have attracted many researches because of thier room temperature ferroelectric nature. TGS found wide applications in electronic and optical fields. In present work, pure and ADP-, KDP- (0.2 mol) doped TGSP crystals are grown from solution growth method. Grown crystals are subjected to UV-Vis, IR, and Raman spectral studies. Crystal structure of grown crystals is obtained from powder XRD pattern. Ferroele...

  14. 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.

  15. 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.

  16. Growth and characterization of 4-chloro-3-nitrobenzophenone single crystals using vertical Bridgman technique

    Energy Technology Data Exchange (ETDEWEB)

    Aravinth, K., E-mail: anandcgc@gmail.com; Babu, G. Anandha, E-mail: anandcgc@gmail.com; Ramasamy, P., E-mail: anandcgc@gmail.com [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam -603110, Tamilnadu (India)

    2014-04-24

    4-chloro-3-nitrobenzophenone (4C3N) has been grown by using vertical Bridgman technique. The grown crystal was confirmed by Powder X-ray diffraction analysis. The crystalline perfection of the grown crystal was examined by high-resolution X-ray diffraction study. The fluorescence spectra of grown 4C3N single crystals exhibit emission peak at 575 nm. The micro hardness measurements were used to analyze the mechanical property of the grown crystal.

  17. The ISGRI CdTe gamma-ray camera: first steps

    CERN Document Server

    Limousin, O; Cretolle, J; Dzitko, H; Laurent, P; Lebrun, F; Leray, J P; Arques, M; Baffert, N; Mathy, F; Noca, A; Trystram, P; Villard, P; Baron, P; Delagnes, E; Rouger, M

    2000-01-01

    The gamma-ray telescope IBIS, on board the INTEGRAL satellite, features a coded-mask aperture, active and passive shields and two detector arrays. The first one (ISGRI) is an assembly of 16384 CdTe detectors (4x4 mm large, 2 mm thick) operating at room temperature. ISGRI covers the lower part (15 keV-1 MeV) of the IBIS energy range (15 keV-10 MeV). Detectors are arranged on polycells, each including 16 crystals, connected to their front-end electronics (ASICs). Each of the eight independent ISGRI modules are made of 128 polycells. The ASICs contain a low noise charge-sensitive preamplifier and feature pulse rise-time measurement in addition to the standard pulse height measurement. This permits to compute a charge loss correction based on the charge drift time. After application of this correction, a spectral resolution around 7.5% at 122 keV is obtained with the ASICs. Today, 16 polycells have been mounted on the first representative ISGRI module. This module has been interfaced with the entire ISGRI data-pr...

  18. Structure and dynamics of CdTe studied by X-ray and neutron scattering

    Science.gov (United States)

    Stone, Matthew; Niedziela, Jennifer

    2015-03-01

    We present x-ray diffraction and inelastic neutron scattering studies of the structure and lattice dynamics of commercially available cadmium telluride. We also present complementary density functional theory calculations. The x-ray data show a subtle structural transition is present near 80 K, which manifests also in the measured phonon density of states. Refinement of the structure above and below the transition temperature shows no change to the long-range ordered structure. The inelastic neutron scattering studies were performed using an isotopically un-enriched sample of CdTe, which possesses a high cross section for thermal neutron absorption. The neutron portion of the study was performed with a thin-plate geometry in the reflection condition at the ARCS instrument at the SNS, showing the high flux of the instrument makes possible lattice dynamics studies of materials with high thermal neutron absorption. Single crystal and powder inelastic neutron scattering measurements will be presented. Current interpretation of the nature of the transition and future studies will be discussed. This research at ORNL's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.

  19. Investigation of unidirectional growth and characterization of nonlinear optical L-alaninium p-toluenesulfonate crystal

    Science.gov (United States)

    Thayanithi, V.; Rajesh, K.; Praveen Kumar, P.

    2017-08-01

    An aminoacid nonlinear optical crystal of L-alaninium p-toluenesulfonate (LAPT) was grown by Sankaranarayanan and Ramasamy (SR) method. The seed crystal of LAPT was grown with the help of a conventional solution method. The size of the grown crystal is 50 mm length and 20 mm diameter for (0 1 0) plane. The solubility of LAPT was determined in deionized water. The grown LAPT crystal belongs to the orthorhombic crystal system with noncentrosymmetric space group P212121. The morphology of the grown LAPT crystal reveals a hexagonal shape with six facet. The lower cut-off wavelength of the grown crystal is found to be 285 nm. Optical transmittance of the crystal grown by SR method is increased by 20%, when compared with the conventionally grown crystal. The LDT value of the SR-grown LAPT crystal has increased by 0.57 GW cm-2, compared with LAPT crystal grown by conventional method. The emission spectra of the grown crystal was analysed by photoluminescence analysis. The mechanical strength of the grown LAPT crystal was analysed by using Vickers hardness test, and the work hardening coefficient (n) of the LAPT crystal grown by SR method is found to be 2.20. The second harmonic generation efficiency of the LAPT crystal is 2.1 times that of KDP.

  20. 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.

  1. 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.)

  2. 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.)

  3. 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

  4. Investigation on the bulk growth of α-LiIO3 single crystals and the ...

    Indian Academy of Sciences (India)

    Surface defects of the grown crystals were studied by etch patterns. The crystal grown at pH 10showed 10% optical transmission enhancement in comparison to the crystals grown at pH 2. The indirect optical bandgap ofthe crystal was reinvestigated using ultraviolet–Visible–near-infrared transmittance spectrum. The laser ...

  5. Crystal growth and structural analysis of zirconium sulphoselenide ...

    Indian Academy of Sciences (India)

    Wintec

    tion for the growth of these crystals is given. The stoichiometry of the grown crystals ... 646. Table 1. Growth parameters of zirconium sulphoselenide single crystal grown using chemical vapour transport technique. Physical .... The needle shaped, black or radish shining layered single crystals of zirconium sulphoselenide ...

  6. A pixellated γ-camera based on CdTe detectors clinical interests and performances

    Science.gov (United States)

    Chambron, J.; Arntz, Y.; Eclancher, B.; Scheiber, Ch; Siffert, P.; Hage Hali, M.; Regal, R.; Kazandjian, A.; Prat, V.; Thomas, S.; Warren, S.; Matz, R.; Jahnke, A.; Karman, M.; Pszota, A.; Nemeth, L.

    2000-07-01

    A mobile gamma camera dedicated to nuclear cardiology, based on a 15 cm×15 cm detection matrix of 2304 CdTe detector elements, 2.83 mm×2.83 mm×2 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 γ-camera performances. But their use as γ 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 of 256 detectors shared in 16 modules. Each module consists in a thin ceramic plate holding a line of 16 detectors, in four groups of four for an easy replacement, and holding a special 16 channels integrated circuit designed by CLRC (UK). A detection and acquisition logic based on a DSP card and a PC has been programmed by Eurorad for spectral and counting acquisition modes. Collimators LEAP and LEHR from commercial design, mobile gantry and clinical software were provided by Siemens (Germany). The γ-camera head housing, its general mounting and the electric connections were performed by Phase Laboratory (CNRS, France). The compactness of the γ-camera head, thin detectors matrix, electronic readout and collimator, facilitates the detection of close γ sources with the advantage of a high spatial resolution. Such an equipment is intended to bedside explorations. There is a growing clinical requirement in nuclear cardiology to early assess the extent of an

  7. A pixellated {gamma}-camera based on CdTe detectors clinical interests and performances

    Energy Technology Data Exchange (ETDEWEB)

    Chambron, J. E-mail: chambron@alsace.u-strasbg.fr; Arntz, Y.; Eclancher, B.; Scheiber, Ch.; Siffert, P.; Hage Hali, M.; Regal, R.; Kazandjian, A.; Prat, V.; Thomas, S.; Warren, S.; Matz, R.; Jahnke, A.; Karman, M.; Pszota, A.; Nemeth, L

    2000-07-01

    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 of 256 detectors shared in 16 modules. Each module consists in a thin ceramic plate holding a line of 16 detectors, in four groups of four for an easy replacement, and holding a special 16 channels integrated circuit designed by CLRC (UK). A detection and acquisition logic based on a DSP card and a PC has been programmed by Eurorad for spectral and counting acquisition modes. Collimators LEAP and LEHR from commercial design, mobile gantry and clinical software were provided by Siemens (Germany). The {gamma}-camera head housing, its general mounting and the electric connections were performed by Phase Laboratory (CNRS, France). The compactness of the {gamma}-camera head, thin detectors matrix, electronic readout and collimator, facilitates the detection of close {gamma} sources with the advantage of a high spatial resolution. Such an equipment is intended to bedside explorations. There is a growing clinical requirement in nuclear cardiology to early assess

  8. Growth of Ce-Doped LSO Single Crystals by Stockbarger-Bridgman Modified Crystallization Method

    International Nuclear Information System (INIS)

    Namtalishvili, M.; Sanadze, T.; Basharuli, N.; Magalashvili, P.; Mikaberidze, A.; Razmadze, Z.; Gabeskiria, M.

    2006-01-01

    The modified Stockbarger-Bridgman method was suggested for the growth of optically perfect LSO:Ce single crystals. Our investigations have shown that the most perfect crystals are grown by by the horizontally directed crystallization. In this case the elements of directional crystallyzation are combined with the zone melting. Crystallization is carried out in the conditions of sufficiently developed mirror of meltin. As a result in this case the chemical purity of grown crystals increases. (author)

  9. 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.

  10. 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.

  11. 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...

  12. 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.

  13. Growth and characterization of nonlinear optical single crystals: bis ...

    Indian Academy of Sciences (India)

    methoxy benzoate (C4MB) single crystals were successfully grown by the slow evaporation solution growth technique. The harvested crystals were subjected to single-crystal X-ray diffraction, spectral, optical, thermal and mechanical studies in ...

  14. Growth of dopamine crystals

    Energy Technology Data Exchange (ETDEWEB)

    Patil, Vidya, E-mail: vidya.patil@ruparel.edu; Patki, Mugdha, E-mail: mugdha.patki@ruparel.edu [D. G. Ruparel College, Senapati Bapat Marg, Mahim, Mumbai – 400 016 (India)

    2016-05-06

    Many nonlinear optical (NLO) crystals have been identified as potential candidates in optical and electro-optical devices. Use of NLO organic crystals is expected in photonic applications. Hence organic nonlinear optical materials have been intensely investigated due to their potentially high nonlinearities, and rapid response in electro-optic effect compared to inorganic NLO materials. There are many methods to grow organic crystals such as vapor growth method, melt growth method and solution growth method. Out of these methods, solution growth method is useful in providing constraint free crystal. Single crystals of Dopamine have been grown by evaporating the solvents from aqueous solution. Crystals obtained were of the size of orders of mm. The crystal structure of dopamine was determined using XRD technique. Images of crystals were obtained using FEG SEM Quanta Series under high vacuum and low KV.

  15. Recrystallization phenomena of solution grown paraffin dendrites

    NARCIS (Netherlands)

    Hollander, F.F.A.; Hollander, F.; Stasse, O.; van Suchtelen, J.; van Enckevort, W.J.P.

    2001-01-01

    Paraffin crystals were grown from decane solutions using a micro-Bridgman set up for in-situ observation of the morphology at the growth front. It is shown that for large imposed velocities, dendrites are obtained. After dendritic growth, aging or recrystallization processes set in rather quickly,

  16. Positron lifetime measurements in a II-VI compound: indium doped CdTe

    International Nuclear Information System (INIS)

    Gely, C.; Corbel, C.; Triboulet, R.

    1989-01-01

    Positron lifetime measurements in as-grown cadmium telluride crystals doped with indium give direct evidence of the presence of monovacancies. The average positron lifetime is measured as a function of temperature. Two different behaviours appear, depending on temperature: in the 5 to 80 K range, one single lifetime is measured, in the 80 to 300 K range, two lifetimes are detected. Positrons are trapped in a defect which may be attributed to a Cd monovacancy [fr

  17. Crystal growth, structure analysis and characterisation of 2 - (1, 3 - dioxoisoindolin - 2 - yl) acetic acid single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Sankari, R. Siva, E-mail: sivasankari.sh@act.edu.in [Department of Physics, Agni College of Technology, Thalambur, Chennai-603103 (India); Perumal, Rajesh Narayana [Department of Physics, SSN College of Engineering, Kalavakkam, Chennai-603110 (India)

    2014-04-24

    Single crystal of dielectric material 2 - (1, 3 - dioxoisoindolin - 2 - yl) acetic acid has been grown by slow evaporation solution growth method. The grown crystal was harvested in 25 days. The crystal structure was analyzed by Single crystal X - ray diffraction. UV-vis-NIR analysis was performed to examine the optical property of the grown crystal. The thermal property of the grown crystal was studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The dielectric measurements were carried out and the dielectric constant was calculated and plotted at all frequencies.

  18. 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...

  19. 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.

  20. 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%.

  1. 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.

  2. Influence of solvents on the habit modification of alpha lactose monohydrate single crystals

    Science.gov (United States)

    Parimaladevi, P.; Srinivasan, K.

    2013-02-01

    Restricted evaporation of solvent method was adopted for the growth of alpha lactose monohydrate single crystals from different solvents. The crystal habits of grown crystals were analysed. The form of crystallization was confirmed by powder x-ray diffraction analysis. Thermal behaviour of the grown crystals was studied by using differential scanning calorimetry.

  3. Solid state single crystal growth of three-dimensional faceted LaFeAsO crystals

    Science.gov (United States)

    Kappenberger, Rhea; Aswartham, Saicharan; Scaravaggi, Francesco; Blum, Christian G. F.; Sturza, Mihai I.; Wolter, Anja U. B.; Wurmehl, Sabine; Büchner, Bernd

    2018-02-01

    Solid state single crystal growth (SSCG) is a crystal growth technique where crystals are grown from a polycrystalline matrix. Here, we present single crystals of the iron pnictide LaFeAsO grown via SSCG using NaAs as a liquid phase to aid crystallization. The size of the as-grown crystals are up to 2 × 3 × 0.4 mm3. Typical for this method, but very uncommon for crystals of the pnictide superconductors and especially for the oxypnictides, the crystals show pronounced facets caused by considerable growth in c direction. The crystals were characterized regarding their composition, structure, magnetic, and thermodynamic properties. This sets the stage for further measurements for which single crystals are crucial such as any c axis and reciprocal space dependent measurements.

  4. Electronic states of germanium grown under micro-gravity condition

    Energy Technology Data Exchange (ETDEWEB)

    Sugahara, A. [Department of Physics, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan)]. E-mail: sugahara@tsurugi.phys.sci.osaka-u.ac.jp; Ogawa, T. [Department of Physics, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Fujii, K. [Department of Physics, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Ohyama, T. [Liberal Arts, Fukui University of Technology, 3-6-1 Gakuen, Fukui, Fukui 910-8505 (Japan); Nakata, J. [Kyoto Semiconductor Corp. 418-9 Yodo Saime-cho, Fushimi-ku, Kyoto 613-0915 (Japan)

    2006-04-01

    Magneto-optical absorption measurements of Sb-doped germaniums grown under micro-gravity condition were carried out to investigate the influence of the gravity on crystal growth, using far-infrared laser and microwave. For comparison, we prepared two germanium crystals grown in the same conditions except the gravity conditions. In spite of the quite short growth period, the germanium grown under micro-gravity has a quite good quality. The lineshape analysis of Zeeman absorption peaks due to donor electrons indicates the existence of residual thermal acceptors.

  5. Electric properties of semi-insulating crystals CdTe:Cl

    International Nuclear Information System (INIS)

    Arkadyeva, E.N.; Matveev, O.A.

    1977-01-01

    Hall effect and conductivity measurement were carried out on chlorine doped semi-insulating CdTe crystals, of p and n electric type. In p type crystals the depth of the dominating level was determined (+0.7eV) as well as the concentration of associated centres (10 13 -10 14 cm -3 ). The mobility values are limited by a process of diffusion on heterogeneities

  6. Growth and characterization of gel grown pure and mixed iron ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Several applications of iron tartrate and manganese tartrate compounds are reported in the literature. In the present investigation, we have grown pure and mixed iron (II)–manganese levo-tartrate crystals by single diffusion gel growth technique. Crystals with spherulitic morphology were harvested. The colouration ...

  7. Growth and characterization of gel grown pure and mixed iron ...

    Indian Academy of Sciences (India)

    Several applications of iron tartrate and manganese tartrate compounds are reported in the literature. In the present investigation, we have grown pure and mixed iron (II)–manganese levo-tartrate crystals by single diffusion gel growth technique. Crystals with spherulitic morphology were harvested. The colouration of the ...

  8. Studies on crystal growth and physical properties of 4-(dimethylamino)benzaldehyde-2,4-dinitroaniline single crystal

    Science.gov (United States)

    Jebin, R. P.; Suthan, T.; Rajesh, N. P.; Vinitha, G.; Dhas, S. A. Britto

    2016-07-01

    The organic material 4-(dimethylamino)benzaldehyde-2,4-dinitroaniline has been grown by slow evaporation technique. Single crystal and Powder X-ray diffraction studies have been carried out to conform the grown crystal. FTIR and FT-Raman spectra were recorded to identify the functional groups present in the crystal. The optical property of the grown crystal was analysed by UV-Vis-NIR measurement. The thermal property of the grown crystal was analysed by thermogravimetric (TG) and differential thermal analyses (DTA). Thermal diffusivity of the grown crystal was analysed by Photo acoustic spectroscopic (PAS) studies. The third order nonlinear optical properties of 4-(dimethylamino)benzaldehyde-2,4-dinitroaniline was measured by the Z-scan technique using 532 nm diode pumped continuous wave (CW) Nd:YAG laser. The mechanical property of the grown crystal was analysed by using microhardness studies.

  9. Growth of <001> TGCC crystals by Sankaranarayanan–Ramasamy (SR) method and its characterization

    Energy Technology Data Exchange (ETDEWEB)

    Boopathi, K.; Ramasamy, P., E-mail: ramasamyp@ssn.edu.in [Centre for Crystal Growth, SSN college of Engineering, Kalavakkam-603110 (India)

    2015-06-24

    Single crystals of tris (glycine) Calcium (II) dichloride (TGCC) were successfully grown by Sankaranarayanan-Ramasamy (SR) method and conventional slow evaporation solution technique which have the sizes of 40 mm in length, 20 mm in diameter and 10×10×3 mm{sup 3} respectively. The grown TGCC crystals have been subjected to single crystal X-ray diffraction, UV-Vis NIR studies, Vickers micro hardness analysis, laser damage and SHG analysis. The transmittance of the grown crystal was analyzed by recording UV-Vis-NIR analysis. Mechanical strength of the SR method grown crystals was higher than the conventional method grown crystal.

  10. Steering a crystallization process to reduce crystal polydispersity; case study of insulin crystallization

    Science.gov (United States)

    Nanev, Christo N.; Petrov, Kostadin P.

    2017-12-01

    The use of the classical nucleation-growth-separation principle (NGSP) was restricted hitherto to nucleation kinetics studies only. A novel application of the NGSP is proposed. To reduce crystal polydispersity internal seeding of equally-sized crystals is suggested, the advantage being avoidance of crystal grinding, sieving and any introduction of impurities. In the present study, size distributions of grown insulin crystals are interpreted retrospectively to select the proper nucleation stage parameters. The conclusion is that when steering a crystallization process aimed at reducing crystal polydispersity, the shortest possible nucleation stage duration has to be chosen because it renders the closest size distribution of the nucleated crystal seeds. Causes of inherent propensity to increasing crystal polydispersity during prolonged growth are also explored. Step sources of increased activity, present in some crystals while absent in others, are pointed as the major polydispersity cause. Insulin crystal morphology is also considered since it determines the dissolution rate of a crystalline medicine.

  11. Analysis on the structural, vibrational and defect states of chlorine treated polycrystalline cadmium telluride structures grown by e-beam evaporation

    International Nuclear Information System (INIS)

    Farid, Sidra; Mukherjee, Souvik; Jung, Hyeson; Stroscio, Michael A; Dutta, Mitra

    2015-01-01

    Temperature dependent photoluminescence (PL) measurements are performed in order to study the defect states in cadmium chloride treated polycrystalline cadmium telluride (CdTe) thin films grown by e-beam evaporation technique. Three luminescence bands are observed including a double peak emission at 1.577 eV and 1.573 eV corresponding to free electron-to- acceptor transition and a donor–acceptor pair (DAP) transition, respectively, along with a broad peak at 1.45 eV. This broad band emission is related to A-center chlorine based complex and also includes longitudinal (LO) phonon emission lines for CdTe spaced by ∼21 meV. Investigation into grain sizes revealed grains of 0.2 μm for as-grown films and ∼2–3 μm for chlorine activated films shown by atomic force microscopy (AFM). Raman analysis indicates that the films have been grown with excess of Te leading to p-type conductivity in the structure, whereas LO phonon mode of polycrystalline CdTe reveals quasi phonon modes nature. (paper)

  12. 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.

  13. Electronic stopping power of slow H{sup +} and He{sup 2+} ions in CdTe from first principle

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chang-kai [The Key Laboratory of Beam Technology and Material Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Mao, Fei [School of Nuclear Science and Technology, University of South China, Hengyang 421001 (China); Fu, Yan-long; Liao, Bin [The Key Laboratory of Beam Technology and Material Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Ouyang, Xiao-ping [Northwest Institute of Nuclear Technology, Xi’an 710024 (China); Zhang, Feng-Shou, E-mail: fszhang@bnu.edu.cn [The Key Laboratory of Beam Technology and Material Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator of Lanzhou, Lanzhou 730000 (China)

    2017-02-01

    We study through time-dependent density-functional theory (TDDFT) method the electronic stopping power of low-energy protons and helium ions moving through CdTe under the condition of channeling. The agreement between our calculated results and SRIM data roughly up to the stopping maximum for the proton along the 〈1 0 0〉 and 〈1 1 1〉 crystalline axes and for helium ions along 〈1 0 0〉 crystalline axis is satisfactory, which can be explained by the energy transfer mechanism that electron–hole excitation caused by ions in the solid. However, in the channel of 〈1 1 1〉 for helium ions, a transition between two velocities regimes is observed at about v = 0.4 a.u. This may be an indication of extra energy loss channel beyond the electron–hole excitation. To analyze it, we calculate the amount of electrons captured by the moving projectiles in real time. It is found that the soft transition between two velocities regimes can be attributed to the charge transfer and charge resonance between helium ion and host atoms of CdTe crystal, which are considered as additional energy loss channels.

  14. Growth, characterization and dielectric property studies of gel grown ...

    Indian Academy of Sciences (India)

    Single crystals of barium succinate (BaC4H4O4) were grown in silica gel medium using controlled chemical reaction method. Plate-like single crystals of size up to 3 × 2 × 0.2 mm3 was obtained. Single crystal X-ray diffraction (XRD) studies confirmed that structure of the title compound is tetragonal. Powder X-ray diffraction ...

  15. Influence of microgravity on Ce-doped Bi12 SiO20 crystal defect

    Indian Academy of Sciences (India)

    TECS

    Abstract. Space grown BSO crystal doped with Ce was characterized by means of X-ray fluorescence spectra,. X-ray topography, dislocation density etc. Influence of microgravity on Ce-doped BSO crystal defect was studied by comparing space grown BSO crystal with ground grown one. These results show that composi-.

  16. Influence of microgravity on Ce-doped Bi12 SiO20 crystal defect

    Indian Academy of Sciences (India)

    Space grown BSO crystal doped with Ce was characterized by means of X-ray fluorescence spectra, X-ray topography, dislocation density etc. Influence of microgravity on Ce-doped BSO crystal defect was studied by comparing space grown BSO crystal with ground grown one. These results show that compositional ...

  17. Crystal growth and structural analysis of zirconium sulphoselenide ...

    Indian Academy of Sciences (India)

    The grown crystals were examined under optical zoom microscope for their surface topography study. Hall effect measurements were carried out on grown crystals at room temperature. The negative value of Hall coefficient implies that these crystals are -type in nature. The conductivity is found to decrease with increase of ...

  18. Spectroscopic properties of Pr 3-doped erbium oxalate crystals

    Indian Academy of Sciences (India)

    The crystals were grown by hydro silica gel method under suitable pH conditions and by single diffusion method. The well-grown crystals are bright and transparent. The dark green colour of these crystals changes with the variation of the concentrations of the dopant ions. The absorption spectra have been measured in the ...

  19. Spectroscopic properties of Pr -doped erbium oxalate crystals

    Indian Academy of Sciences (India)

    Er2(C2O4)3 ·. nH2O) crystals have been investigated. The crystals were grown by hydro silica gel method under suitable pH conditions and by single diffusion method. The well-grown crystals are bright and trans- parent. The dark green colour ...

  20. Research on fabrication technology for thin film solar cells for practical use. Research on low-cost fabrication technology for large-area modules (CdS/CdTe solar cell modules); Usumaku taiyo denchi seizo gijutsu no jitsuyoka kenkyu. Daimenseki module no tei cost seizo gijutsu (CdTe taiyo denchi module seizo no gijutsu kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    Tatsuta, M. [New Energy and Industrial Technology Development Organization, Tokyo (Japan)

    1994-12-01

    This paper reports the study results on the fabrication technology of CdS/CdTe solar cell modules in fiscal 1994. (1) On the fabrication technology for high-efficiency large-area solar cells, high-quality CdTe active layer was studied. S content taken in the active layer at sintering of CdTe decreased with an increase in formed CdTe, resulting in improvement of Voc of cells. (2) On the window layer with wide band gap, the solar cell superior in collection efficiency and photoelectric characteristics could be obtained using the newly developed mixed crystal film of Cd(1-x)Zn(x)S. (3) On the forming technology of large-area coating/sintering films, improvement of CdS film quality was studied by pressurized processing of printed CdS films. As a result, improvement of film density and light transmissivity was confirmed. (4) On the leveling process technology of CdTe films, smooth surface films were obtained by experiment using an equipment simultaneously exciting samples in all directions as one of uniform coating methods of films. 7 figs.

  1. A Test of Macromolecular Crystallization in Microgravity: Large, Well-Ordered Insulin Crystals

    Science.gov (United States)

    Borgstahl, Gloria E. O.; Vahedi-Faridi, Ardeschir; Lovelace, Jeff; Bellamy, Henry D.; Snell, Edward H.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Crystals of insulin grown in microgravity on space shuttle mission STS-95 were extremely well-ordered and unusually large (many > 2 mm). The physical characteristics of six microgravity and six earth-grown crystals were examined by X-ray analysis employing superfine f slicing and unfocused synchrotron radiation. This experimental setup allowed hundreds of reflections to be precisely examined for each crystal in a short period of time. The microgravity crystals were on average 34 times larger, had 7 times lower mosaicity, had 54 times higher reflection peak heights and diffracted to significantly higher resolution than their earth grown counterparts. A single mosaic domain model could account for reflections in microgravity crystals whereas reflections from earth crystals required a model with multiple mosaic domains. This statistically significant and unbiased characterization indicates that the microgravity environment was useful for the improvement of crystal growth and resultant diffraction quality in insulin crystals and may be similarly useful for macromolecular crystals in general.

  2. Cz grown 2-in. size Ce:Gd.sub.3./sub.(Al,Ga).sub.5./sub.O.sub.12./sub. single crystal; relationship between Al, Ga site occupancy and scintillation properties

    Czech Academy of Sciences Publication Activity Database

    Kamada, K.; Kurosawa, S.; Průša, Petr; Nikl, Martin; Kochurikhin, V.V.; Endo, T.; Tsutumi, K.; Sato, H.; Yokota, Y.; Sugiyama, K.; Yoshikawa, A.

    2014-01-01

    Roč. 36, č. 12 (2014), 1942-1945 ISSN 0925- 3467 Institutional support: RVO:68378271 Keywords : scintillator * single crystal growth Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.981, year: 2014

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. Crystallization and crystal properties of squid rhodopsin

    International Nuclear Information System (INIS)

    Murakami, Midori; Kitahara, Rei; Gotoh, Toshiaki; Kouyama, Tsutomu

    2007-01-01

    Truncated rhodopsin from the retina of the squid Todarodes pacificus was extracted and crystallized by the sitting-drop vapour-diffusion method. Hexagonal crystals grown in the presence of octylglucoside and ammonium sulfate diffracted to 2.8 Å resolution. Rhodopsin, a photoreceptor membrane protein in the retina, is a prototypical member of the G-protein-coupled receptor family. In this study, rhodopsin from the retina of the squid Todarodes pacificus was treated with V8 protease to remove the C-terminal extension. Truncated rhodopsin was selectively extracted from the microvillar membranes using alkyl glucoside in the presence of zinc ions and was then crystallized by the sitting-drop vapour-diffusion method. Of the various crystals obtained, hexagonal crystals grown in the presence of octylglucoside and ammonium sulfate diffracted to 2.8 Å resolution. The diffraction data suggested that the crystal belongs to space group P6 2 , with unit-cell parameters a = b = 122.1, c = 158.6 Å. Preliminary crystallographic analysis, together with linear dichroism results, suggested that the rhodopsin dimers are packed in such a manner that their transmembrane helices are aligned nearly parallel to the c axis

  11. Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method

    Science.gov (United States)

    Mohanraj, K.; Balasubramanian, D.; Jhansi, N.

    2017-11-01

    A new non-linear optical (NLO) single crystal of lithium boro phthalate (LiBP) was grown by slow solvent evaporation technique. The powder sample was subjected to powder X-ray diffraction (PXRD) to find its crystalline nature and the crystal structure of the grown crystal was determined using single crystal X-ray (SXRD) diffraction analysis. The Fourier Transform Infrared (FTIR) spectrum was recorded for grown crystal to identify the various functional groups present in the compound. The mechanical property of the LiBP single crystal was studied using Vickers microhardness tester. The dielectric constant and dielectric loss measurements were carried out for the grown crystal at various temperatures. The grown crystal was subjected to UV-Visible Spectral Studies to analyze the linear optical behavior of the grown crystal. The Kurtz-Perry Powder technique was employed to measure the Second Harmonic Generation efficiency of the grown crystal.

  12. 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)

  13. 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.

  14. 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...

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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%.

  3. 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...

  4. 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.

  5. 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.

  6. 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.

  7. 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...

  8. 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.

  9. 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.

  10. Chromatic X-ray imaging with a fine pitch CdTe sensor coupled to a large area photon counting pixel ASIC

    Science.gov (United States)

    Bellazzini, R.; Spandre, G.; Brez, A.; Minuti, M.; Pinchera, M.; Mozzo, P.

    2013-02-01

    An innovative X-ray imaging sensor based on Chromatic Photon Counting technology with intrinsic digital characteristics is presented. The system counts individually the incident X-ray photons and selects them according to their energy to produce two color images per exposure. The energy selection occurs in real time and at radiographic imaging speed (GHz global counting rate). Photon counting, color mode and a very fine spatial resolution (more than 10 LP/mm at MTF50) allow to obtain a high ratio between image quality and absorbed dose. The individual building block of the imaging system is a two-side buttable semiconductor radiation detector made of a thin pixellated CdTe crystal coupled to a large area VLSI CMOS pixel ASIC. Modules with 1, 2, 4, and 8 block units have been built. The largest module has 25 × 2.5 cm2 sensitive area. Results and images obtained from testing different modules are presented.

  11. Stability issues of high-energy resolution diode type CdTe nuclear radiation detectors in a long-term operation

    CERN Document Server

    Niraula, M; Aoki, T; Tomita, Y; Hatanaka, Y

    2002-01-01

    High-energy resolution diode type CdTe detectors were fabricated by growing an n-type epitaxial layer on high resistivity p-like crystal wafers, and their stability issues during a long-term operation were studied. Room temperature stability of the detectors was not good at low operating biases of around 200 V. However, it could be improved significantly by operating them at higher biases under full depletion conditions. On the other hand, detectors exhibited excellent stability by cooling them slightly below room temperature down to 0 deg. C. The effect of this low level of cooling on detector stability was found to be more significant than that of applying high biases at room temperature. By using the detector type presented here, stable operation could be obtained at moderate operating voltages of around 400 V and with a modest degree of cooling.

  12. Spectral distribution of the efficiency of terahertz difference frequency generation upon collinear propagation of interacting waves in semiconductor crystals

    International Nuclear Information System (INIS)

    Orlov, Sergei N; Polivanov, Yurii N

    2007-01-01

    Dispersion phase matching curves and spectral distributions of the efficiency of difference frequency generation in the terahertz range are calculated for collinear propagation of interacting waves in zinc blende semiconductor crystals (ZnTe, CdTe, GaP, GaAs). The effect of the pump wavelength, the nonlinear crystal length and absorption in the terahertz range on the spectral distribution of the efficiency of difference frequency generation is analysed. (nonlinear optical phenomena)

  13. Scintillation properties of Ce doped Gd.sub.2./sub.Lu.sub.1./sub.(Ga,Al).sub.5./sub.O.sub.12./sub. single crystal grown by the micro-pulling-down method

    Czech Academy of Sciences Publication Activity Database

    Kamada, K.; Yanagida, T.; Pejchal, Jan; Nikl, Martin; Endo, T.; Tsutumi, K.; Usuki, Y.; Fujimoto, Y.; Fukabori, A.; Yoshikawa, A.

    2012-01-01

    Roč. 352, č. 1 (2012), s. 35-38 ISSN 0022-0248 Grant - others:AV ČR(CZ) M100100910 Institutional research plan: CEZ:AV0Z10100521 Keywords : single crystal growth * oxides * scintillator materials Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.552, year: 2012

  14. The growth of benzophenone crystals by Sankaranarayanan–Ramasamy (SR) method and slow evaporation solution technique (SEST): A comparative investigation

    International Nuclear Information System (INIS)

    Senthil Pandian, M.; Boopathi, K.; Ramasamy, P.; Bhagavannarayana, G.

    2012-01-01

    Highlights: ► Benzophenone single crystal was grown by Sankaranarayanan–Ramasamy method which has the sizes of 1060 mm length and 55 mm diameter for the first time. ► The conventional and SR-grown benzophenone crystals were characterized and compared using HRXRD, etching, laser damage threshold, microhardness, UV-transmittance, birefringence and dielectric analysis. ► The SR-grown benzophenone crystal has higher LDT, microhardness, transparency, dielectric permittivity, birefringence and lower FWHM, EPD, dielectric loss than the crystal grown by conventional method. ► The probable reason for higher crystalline perfection in SR-grown crystal was discussed. -- Abstract: Longest unidirectional〈1 0 0〉 benzophenone (BP) crystal having dimension of 1060 mm length and 55 mm diameter was grown by Sankaranarayanan–Ramasamy method. The growth rate was measured by monitoring the elevation of the crystal–solution interface at different temperatures. The high resolution X-ray diffraction and etching measurements indicate that the unidirectional grown benzophenone crystal has good crystalline perfection and less density of defects. The optical damage threshold of SEST and SR grown BP crystals has been investigated and found that the SR grown benzophenone crystal has higher laser damage threshold value than the conventional method grown crystal. Microhardness measurement shows that crystals grown by SR method have a higher mechanical stability than the crystals grown by SEST method. Dielectric permittivity and birefringence are high in SR grown crystal compared to SEST grown BP crystal. The UV–vis-NIR results show that SR method grown crystal exhibits 7% higher transmittance as against crystals grown by conventional method.

  15. Vertical Bridgman growth and characterization of Cd0.95-xMnxZn0.05Te (x=0.20, 0.30) single-crystal ingots

    Energy Technology Data Exchange (ETDEWEB)

    Bolotnikov, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Kopach, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Kopach, O. [Brookhaven National Lab. (BNL), Upton, NY (United States); Shcherbak, L. [Brookhaven National Lab. (BNL), Upton, NY (United States); Fochuk, P. [Brookhaven National Lab. (BNL), Upton, NY (United States); Filonenko, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); James, R. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2017-08-01

    Solid-liquid phase transitions in Cd0.95-xMnxZn0.05Te alloys with x = 0.20 and 0.30 were investigated by differential thermal analysis (DTA). The heating/cooling rates were 5 and 10 K/min with a melt dwell time of 10, 30 and 60 minutes. Cd0.95-xMnxZn0.05Te (x=0.20, 0.30) single-crystal ingots were grown by the vertical Bridgman method guided using the DTA results. Te inclusions (1-20 microns), typical for CdTe and Cd(Zn)Te crystals, were observed in the ingots by infrared transmission microscopy. The measured X-ray diffraction patterns showed that all compositions are found to be in a single phase. Using current-voltage (I-V) measurements, the resistivity of the samples from each ingot was estimated to be about 105 Ohm·cm. The optical transmission analysis demonstrated that the band-gap width of the investigated ingots increased from 1.77 to 1.88 eV with the increase of the MnTe content from 20 to 30 mol. %.

  16. 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)

  17. Growth, structural, optical, thermal and mechanical studies on 4-Aminopyridinium monophthalate: A novel nonlinear optical crystal

    Science.gov (United States)

    Marudhu, G.; Krishnan, S.; Palanichamy, M.

    2016-03-01

    A novel nonlinear optical crystal of 4-Aminopyridinium monophthalate (4-APMP) was grown by slow evaporation technique using methanol as solvent. Single crystal X-ray diffraction analysis confirms that the grown crystal belongs to orthorhombic system. The presence of functional groups was qualitatively determined by FTIR analysis. The optical absorption studies reveal very low absorption in the entire visible region. The fluorescence emission spectrum shows the emission is in blue region. The thermal stability of the grown crystal is found to be around 197.2 °C. The SHG efficiency of the grown crystal is found to be 1.1 times than that of KDP crystals.

  18. Thermal, FT–IR and dielectric studies of gel grown sodium oxalate ...

    Indian Academy of Sciences (India)

    WINTEC

    Abstract. Oxalic acid metabolism is important in humans, animals and plants. The effect of oxalic acid sodium salt is widely studied in living body. The growth of sodium oxalate single crystals by gel growth is reported, which can be used to mimic the growth of crystals in vivo. The grown single crystals are colourless, ...

  19. Growth and Characterization of ZnTe Crystal

    International Nuclear Information System (INIS)

    Nann Thazin

    2011-12-01

    High quality ZnTe crystals have been synthesized by vapor Transport method. The grown crystals were p-type. The concentration and mobility were 2.5 x 10 16 cm-3 and 23 cm2/Vs at 300K, according to Hall effect measurements. Surface morphology of the crystal was investigated by scanning electron microscope (SEM). Crystal orientation and lattice parameters of the crystals were also analysed by XRD. From X-ray diffraction studies the structure of the grown crystals were found to be zinc-blende. The crystal emitted light in the visible range at room temperature.

  20. (PCG) Protein Crystal Growth HIV Reverse Transcriptase

    Science.gov (United States)

    1992-01-01

    HIV Reverse Transcriptase crystals grown during the USML-1 (STS-50) mission using Commercial Refrigerator/Incubator Module (CR/IM) at 4 degrees C and the Vapor Diffusion Apparatus (VDA). Reverse transcriptase is an enzyme responsible for copying the nucleic acid genome of the AIDS virus from RNA to DNA. Studies indicated that the space-grown crystals were larger and better ordered (beyond 4 angstroms) than were comparable Earth-grown crystals. Principal Investigators were Charles Bugg and Larry DeLucas.

  1. Pulsed laser-induced phase transformations in CdTe single crystals

    Czech Academy of Sciences Publication Activity Database

    Gatskevich, E.; Ivlev, G.; Přikryl, Petr; Černý, R.; Cháb, Vladimír; Cibulka, O.

    2005-01-01

    Roč. 248, - (2005), s. 259-263 ISSN 0169-4332. [International Conference on Photo-Exeited Processes and Applications 4 - ICPEPA /4./. Lecce, 05.09.2004-09.09.2004] R&D Projects: GA ČR(CZ) GA201/04/1503 Institutional research plan: CEZ:AV0Z10190503 Keywords : II-VI semiconductor * laser irradiation * phase change Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.263, year: 2005

  2. Polytypism of Pb-doped single crystals of cadmium iodide

    International Nuclear Information System (INIS)

    Tyagi, U.P.; Trigunayat, G.C.

    1986-01-01

    The zone refining technique has been used both for the purification of cadmium iodide and for the growth of lead-doped single crystals of cadmium iodide. The as-grown crystals when studied by X-ray diffraction show exclusive presence of the most common polytype 4H. The hexagonal plate-shaped crystals of the doped material, grown from aqueous solution, shown polytypism, but of a different nature than the crystals of pure cadmium iodide. The results have been discussed. (author)

  3. 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 ...

  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. 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. 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

  7. 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.

  8. 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.

  9. 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

  10. 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) ...

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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 ...

  16. 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 ...

  17. Growth techniques used to develop CDS/CDTE thin film solar cells ...

    African Journals Online (AJOL)

    Growth techniques used to develop CDS/CDTE thin film solar cells: a review. ... Techniques such as molecular beam epitaxy (MBE), metal organic chemical vapour deposition (MOCVD) called melt growth or Bridgman are well known as high quality semiconductor growth techniques. One of the limitations of these ...

  18. 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.

  19. Improvement in the quality of hematopoietic prostaglandin D synthase crystals in a microgravity environment

    International Nuclear Information System (INIS)

    Tanaka, Hiroaki; Tsurumura, Toshiharu; Aritake, Kosuke; Furubayashi, Naoki; Takahashi, Sachiko; Yamanaka, Mari; Hirota, Erika; Sano, Satoshi; Sato, Masaru; Kobayashi, Tomoyuki; Tanaka, Tetsuo; Inaka, Koji; Urade, Yoshihiro

    2011-01-01

    Crystals of hematopoietic prostaglandin D synthase grown in microgravity show improved quality. Human hematopoietic prostaglandin synthase, one of the better therapeutic target enzymes for allergy and inflammation, was crystallized with 22 inhibitors and in three inhibitor-free conditions in microgravity. Most of the space-grown crystals showed better X-ray diffraction patterns than the terrestrially grown ones, indicating the advantage of a microgravity environment on protein crystallization, especially in the case of this protein

  20. Low-resistivity m-plane freestanding GaN substrate with very low point-defect concentrations grown by hydride vapor phase epitaxy on a GaN seed crystal synthesized by the ammonothermal method

    Science.gov (United States)

    Kojima, Kazunobu; Tsukada, Yusuke; Furukawa, Erika; Saito, Makoto; Mikawa, Yutaka; Kubo, Shuichi; Ikeda, Hirotaka; Fujito, Kenji; Uedono, Akira; Chichibu, Shigefusa F.

    2015-09-01

    An m-plane freestanding GaN substrate satisfying both low resistivity (ρ = 8.5 × 10-3 Ω·cm) and a low point-defect concentration, being applicable to vertically conducting power-switching devices, was grown by hydride vapor phase epitaxy on a nearly bowing-free bulk GaN seed wafer synthesized by the ammonothermal method in supercritical ammonia using an acidic mineralizer. Its threading dislocation and basal-plane staking-fault densities were approximately 104 cm-2 and lower than 100 cm-1, respectively. A record-long fast-component photoluminescence lifetime of 2.07 ns at room temperature was obtained for the near-band-edge emission, reflecting a significantly low concentration of nonradiative recombination centers composed of Ga vacancies.

  1. Schottky barrier and interface chemistry for Ni contacted to Al{sub 0.8}Ga{sub 0.2}N grown on c-oriented AlN single crystal substrates

    Energy Technology Data Exchange (ETDEWEB)

    Tweedie, James; Collazo, Ramon; Rice, Anthony; Akouala, Rajiv-Christer; Sitar, Zlatko [North Carolina State University, Raleigh, NC (United States); Mita, Seiji; Xie, Jinqiao [Hexatech Inc., Morrisville, NC (United States)

    2012-03-15

    We demonstrate electronic sequential tunneling transport through the ground-state subbands of GaN/Al{sub 0.15}Ga{sub 0.85}N quantum cascade structures grown on free-standing GaN substrates. A pronounced transition from a high- to a low-resistance state is observed as the applied voltage is increased. The measured current-voltage characteristics are found to vary with temperature, structure design, and polarity of the applied bias, in a way that is fully consistent with theoretical expectations. The dominant transport mechanism is determined to be scattering-assisted tunneling (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Further progress in lead tungstate crystals

    International Nuclear Information System (INIS)

    Fyodorov, A.; Korzhik, M.; Missevitch, O.; Pavlenko, V.; Kachanov, V.; Singovsky, A.; Annenkov, A.N.; Ligun, V.A.; Peigneux, J.P.; Vialle, J.P.

    1994-12-01

    Lead tungstate (PbWO 4 ) called PWO crystal is considered as a promising material for precise electromagnetic calorimetry. It is shown that the tuning of the growing conditions improved the uniformity of the stoichiometric PWO crystal. Crystals grown with Nb doping show improved transmission below 400 nm and, by controlling the occurrence of the defect in the crystal based on Pb 3+ ions, their radiation hardness is increased significantly. (K.A.). 10 refs., 10 figs., 2 tabs

  3. Fabrication and Crystal Structure of [REMO3/ABO3] (A =Ca, La, B =Fe, Mn, RE =Bi, La, M =Fe, Fe0.8Mn0.2) Superlattices Grown by Pulsed Laser Deposition Method

    Science.gov (United States)

    Takase, K.; Watabe, Y.; Iwata, N.; Oikawa, T.; Hashimoto, T.; Huijben, M.; Rijnders, G.; Yamamoto, H.

    2014-03-01

    The superlattices of [REMO3/ABO3] (RE =Bi, La, M =Fe, Fe0.8Mn0.2 A =Ca, La, B =Fe, Mn) were prepared by Pulsed laser deposition (PLD) method grown on SrTiO3(STO)(100) for the novel materials which show ferromagnetic and ferroelectric properties with giant magnetoelectric effect at room temperature. When the superlattices were prepared, seven units LaFeO3(LFO) film was deposited first, and the required pulses for other materials to grow seven units were calculated using the growth rate ratio and the growth rate of the last three units of LFO. One of the superlattices, [7 units - BiFe0.8Mn0.2O3(BFMO) / 7 units - CaMnO3(CMO)] stacking for 14 times, the satellite peaks from -2 to +1 were observed. From the fitting to the X-ray reflection spectra, thickness of BFMO and CMO in [BFMO/CMO] one cycle was 2.139nm (5.3 units) and 2.042nm (5.5 units). Although the deposited number of units was definitely less than seven, the satellite peaks are derived from the superstructure. Reciprocal space mapping shows the in-plain lattice constant of [BFMO/CMO] superlattices was not fitted to that of substrate. The calculated in-plain lattice parameter was 0.382 nm longer than the value of 0.3732 nm, which is the bulk CMO and in-plain lattice parameter of CMO thin film grown on STO(001) substrate. This study is supported by Grant-in-Aid for Scientific Research (C), KAKENHI 25420295, and Nihon University Multidisciplinary Research Grant for 2013.

  4. Second harmonic chalcone crystal: Synthesis, growth and characterization

    Energy Technology Data Exchange (ETDEWEB)

    D' Silva, E.D., E-mail: deepak.dsilva@gmail.co [Department of studies in Physics, Mangalore University, Mangalagangotri, Mangalore 574199 (India); Narayan Rao, D. [School of Physics, University of Hyderabad, Hyderabad 500046 (India); Philip, Reji [Light and Matter Physics Group, Raman Research Institute, Bangalore 560080 (India); Butcher, Ray J. [Department of Chemistry, Howard University, Washington, DC 20059 (United States); Rajnikant [Department of Physics and Electronics, University of Jammu, Jammu Tawi 180006 (India); Dharmaprakash, S.M. [Department of studies in Physics, Mangalore University, Mangalagangotri, Mangalore 574199 (India)

    2011-05-15

    The novel nonlinear optical chalcone derivative (2E)-3-[4-(methylsulfanyl)phenyl]-1-(3-bromophenyl)prop-2-en-1-one (3Br4MSP) crystals have been grown by slow evaporation technique at ambient temperature. The crystal was subjected to different types of characterization method in order to study its possible application in nonlinear optics. The structure determination of the grown crystal was done by single crystal X-ray diffraction study. The morphology of the crystal is studied. The crystal was subjected to thermal analysis to find its thermal stability. The grown crystals were characterized for their optical transmission and mechanical hardness. The second harmonic generation (SHG) efficiency of the crystal is obtained by classical powdered technique. The laser damage threshold for 3Br4MSP crystal was determined using Q-switched Nd:YAG laser.

  5. Macromolecule Crystal Quality Improvement in Microgravity: The Role of Impurities

    Science.gov (United States)

    Judge, Russell A.; Snell, Edward H.; Pusey, Marc L.; Sportiello, Michael G.; Todd, Paul; Bellamy, Henry; Borgstahl, Gloria E.; Pokros, Matt; Cassanto, John M.

    2000-01-01

    While macromolecule impurities may affect crystal size and morphology the over-riding question is; "How do macromolecule impurities effect crystal X-ray quality and diffraction resolution?" In the case of chicken egg white lysozyme, crystals can be grown in the presence of a number of impurities without affecting diffraction resolution. One impurity however, the lysozyme dimer, does negatively impact the X-ray crystal properties. Crystal quality improvement as a result of better partitioning of this impurity during crystallization in microgravity has been reported'. In our recent experimental work dimer partitioning was found to be not significantly different between the two environments. Mosaicity analysis of pure crystals showed a reduced mosaicity and increased signal to noise for the microgravity grown crystals. Dimer incorporation however, did greatly reduce the resolution limit in both ground and microgravity grown crystals. These results indicate that impurity effects in microgravity are complex and may rely on the conditions or techniques employed.

  6. Bridgman growth of large-aperture yttrium calcium oxyborate crystal

    International Nuclear Information System (INIS)

    Wu, Anhua; Jiang, Linwen; Qian, Guoxing; Zheng, Yanqing; Xu, Jun; Shi, Erwei

    2012-01-01

    Highlights: ► YCOB is a novel non-linear optical crystal possessing good thermal, mechanical and nonlinear optical properties. ► Large size crystal growth is key technology question for YCOB crystal. ► YCOB crystals 3 in. in diameter were grown with modified vertical Bridgman method. ► It is a more effective growth method to obtain large size and high quality YCOB crystal. -- Abstract: Large-aperture yttrium calcium oxyborate YCa 4 O(BO 3 ) 3 (YCOB) crystals with 3 in. in diameter were grown with modified vertical Bridgman method, and the large crystal plate (63 mm × 68 mm × 20 mm) was harvested for high-average power frequency conversion system. The crack, facet growth and spiral growth can be effectively controlled in the as-grown crystal, and Bridgman method displays more effective in obtain large size and high quality YCOB crystal plate than Czochralski technique.

  7. A facile and green preparation of high-quality CdTe semiconductor nanocrystals at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Liu Yan [Jilin Province Research Center for Engineering and Technology of Spectral Analytical Instruments, Jilin University, Changchun 130023 (China); Shen Qihui; Shi Weiguang; Li Jixue; Liu Xiaoyang [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Yu Dongdong [1st Hopstail affiliated to Jilin University, Jilin University, Changchun 130023 (China); Zhou Jianguang [Research Center for Analytical Instrumentation, Zhejiang University, Hangzhou 310058 (China)], E-mail: liuxy@jlu.edu.cn, E-mail: jgzhou70@126.com

    2008-06-18

    One chemical reagent, hydrazine hydrate, was discovered to accelerate the growth of semiconductor nanocrystals (cadmium telluride) instead of additional energy, which was applied to the synthesis of high-quality CdTe nanocrystals at room temperature and ambient conditions within several hours. Under this mild condition the mercapto stabilizers were not destroyed, and they guaranteed CdTe nanocrystal particle sizes with narrow and uniform distribution over the largest possible range. The CdTe nanocrystals (photoluminescence emission range of 530-660 nm) synthesized in this way had very good spectral properties; for instance, they showed high photoluminescence quantum yield of up to 60%. Furthermore, we have succeeded in detecting the living Borrelia burgdorferi of Lyme disease by its photoluminescence image using CdTe nanocrystals.

  8. Crystal growth and crystallography

    Science.gov (United States)

    Chernov, A. A.

    1998-01-01

    Selected topics that may be of interest for both crystal-structure and crystal-growth communities are overviewed. The growth of protein crystals, along with that of some other compounds, is one of the topics, and recent insights into related phenomena are considered as examples of applications of general principles. The relationship between crystal growth shape and structure is reviewed and an attempt to introduce semiquantitative characterization of binding for proteins is made. The concept of kinks for complex structures is briefly discussed. Even at sufficiently low supersaturations, the fluctuation of steps may not be sufficient to implement the Gibbs-Thomson law if the kink density is low enough. Subsurface ordering of liquids and growth of rough interfaces from melts is discussed. Crystals growing in microgravity from solution should be more perfect if they preferentially trap stress-inducing impurities, thus creating an impurity-depleted zone around themselves. Evidently, such a zone is developed only around the crystals growing in the absence of convection. Under terrestrial conditions, the self-purified depleted zone is destroyed by convection, the crystal traps more impurity and grows stressed. The stress relief causes mosaicity. In systems containing stress-inducing but poorly trapped impurities, the crystals grown in the absence of convection should be worse than those of their terrestrial counterparts.

  9. 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.

  10. Impedance analysis and high temperature conduction mechanism of flux grown Pb(Zn{sub 1/3}Nb{sub 2/3}){sub 0.91}Ti{sub 0.09}O{sub 3} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Singh, B.K.; Kumar, B. [Crystal Lab., Dept. of Physics and Astrophysics, University of Delhi (India)

    2010-10-15

    The electrical properties of Pb(Zn{sub 1/3} Nb{sub 2/3}){sub 0.91}Ti{sub 0.09}O{sub 3} single crystals over a wide range of frequencies (20 Hz to 2 MHz) and temperature (30 to 490 C) were studied using impedance spectroscopic technique. A strongly frequency dependant Debye type relaxation process in crystals was observed. The activation energy for relaxation was found to be 1.72 eV. The nature of Cole-Cole plot reveals the contribution of only grain (bulk) effect in the sample. The temperature dependant conductivity was found to different in different temperature regions, which shows the presence of different carrier for conduction. The activation energy for conduction in the order of 1.69 eV suggested that the conduction process in higher temperature region is governed by the presence of lead vacancy defect in the sample. Further, the negative temperature thermistor behaviour of the system was explored and various associated parameters were calculated. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Growth of L-Valinium Aluminium Chloride single crystal for OLED and super-capacitor applications

    Science.gov (United States)

    Kalaivani, D.; Vijayalakshmi, S.; Theras, J. Elberin Mary; Jayaraman, D.; Joseph, V.

    2015-12-01

    L-Valinium Aluminium Chloride (LVAC), a novel semi-organic material, was grown using slow evaporation under isothermal condition. The single crystal data reveal that the grown crystal belongs to monoclinic system. The SEM micrographs give clear picture about the surface morphology. Further, they confirm the inclusion of aluminium chloride into atomic sites of L-Valine. The compositional elements present in the crystal were identified through EDAX analysis. The mass spectral analysis was carried out to determine the molecular weight of the grown crystal. The optical transparency of the grown crystal was investigated by UV-vis-NIR spectrum. FTIR spectral study was used to identify the functional groups present in the grown material. The luminescence characteristics of grown material were analysed to confirm the effect of metal ion on the ligand. This property makes the material suitable for OLED application. The supercapacitive performance of the grown crystal was finally studied using cyclic voltammetry.

  12. Electrochemical preparation of CdTe semiconductor films from ammoniac-chloride solutions containing 2,2'-dipyridyl

    International Nuclear Information System (INIS)

    Dergacheva, M.B.; Statsyuk, V.N.; Fogel', L.A.

    2007-01-01

    Electrodeposition of CdTe films from ammoniac-chloride buffer electrolytes with 2,2'-dipyridyl additions is studied. Effect of film grains size on light volt-ampere characteristics of CdTe semiconductor compound is studied. Samples prepared from ammoniac-chloride buffer electrolytes with pH 9.2 in the presence of 1· -3 m. 2,2'-dipyridyl demonstrates the best characteristic [ru

  13. 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

  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. 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.

  16. On the growth of calcium tartrate tetrahydrate single crystals

    Indian Academy of Sciences (India)

    Unknown

    menon, especially those involved in the gel technique. With an aim of controlling nucleation and improving the size, in the present study, we have grown pure calcium tartrate tetrahydrate single crystals using calcium formate mixed with formic acid as the supernatant solution. The grown crystals have been characterized by ...

  17. Insights into the effect of N-acetyl-L-cysteine-capped CdTe quantum dots on the structure and activity of human serum albumin by spectroscopic techniques

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Haoyu; Yang, Xudan; Li, Meng; Han, Songlin; Liu, Yingxue [School of Environmental Science and Engineering, Shandong University, China-America CRC for Environment & Health, Shandong Province, 27# Shanda South Road, Jinan 250100 (China); Tan, Xuejie [School of Chemistry and Pharmaceutical Engineering, Qilu University of Technology, Jinan, Shandong Province 250353 (China); Liu, Chunguang, E-mail: chunguangliu2013@sdu.edu.cn [School of Environmental Science and Engineering, Shandong University, China-America CRC for Environment & Health, Shandong Province, 27# Shanda South Road, Jinan 250100 (China); Liu, Rutao [School of Environmental Science and Engineering, Shandong University, China-America CRC for Environment & Health, Shandong Province, 27# Shanda South Road, Jinan 250100 (China)

    2015-11-15

    Quantum dots (QDs) are a kind of nanostructured semiconductor crystals with the size range of 1–10 nm. Their unique photophysical properties and potential toxicity to human health have aroused wide concern of scientists and general public. However, the interaction mechanism of QDs on human serum albumin (HSA, the vital protein in human blood) from both structural and functional perspectives is rarely reported. In the present work, effects of N-acetyl-L-cysteine-capped CdTe quantum dots with fluorescence emission peak at 612 nm (QDs-612) on the conformation and function of HSA were investigated by spectroscopic methods, molecular docking study and esterase activity assay. The hydrophobic interaction between HSA and QDs-612 was spontaneous with the binding constants calculated to be 6.85×10{sup 5} L mol{sup −1} (298 K) and 8.89×10{sup 5} L mol{sup −1} (308 K). The binding of QDs-612 to HSA induced the static quenching of fluorescence and the changes of secondary structure and microenvironment of Tyr-411 residue, which resulted in serious decrease on the hydrolysis of substrate p-nitrophenylacetate in esterase activity assay of HSA. This work confirms the possibility on direct interaction of QDs-612 with HSA and obtains a possible mechanism of relationship between conformation and function of HSA. - Highlights: • The interaction between CdTe QDs (QDs-612) and HSA is spontaneous. • The predominant force of the binding is hydrophobic interaction. • The interaction changes the secondary structure of HSA. • Tyr-411 residue of HSA expose to a hydrophilic environment. • The esterase activity of HSA decreases by adding QDs-612.

  18. Preventing Crystal Agglomeration of Pharmaceutical Crystals Using Temperature Cycling and a Novel Membrane Crystallization Procedure for Seed Crystal Generation

    Directory of Open Access Journals (Sweden)

    Elena Simone

    2018-01-01

    Full Text Available In this work, a novel membrane crystallization system was used to crystallize micro-sized seeds of piroxicam monohydrate by reverse antisolvent addition. Membrane crystallization seeds were compared with seeds produced by conventional antisolvent addition and polymorphic transformation of a fine powdered sample of piroxicam form I in water. The membrane crystallization process allowed for a consistent production of pure monohydrate crystals with narrow size distribution and without significant agglomeration. The seeds were grown in 350 g of 20:80 w/w acetone-water mixture. Different seeding loads were tested and temperature cycling was applied in order to avoid agglomeration of the growing crystals during the process. Focused beam reflectance measurement (FBRM; and particle vision and measurement (PVM were used to monitor crystal growth; nucleation and agglomeration during the seeded experiments. Furthermore; Raman spectroscopy was used to monitor solute concentration and estimate the overall yield of the process. Membrane crystallization was proved to be the most convenient and consistent method to produce seeds of highly agglomerating compounds; which can be grown via cooling crystallization and temperature cycling.

  19. Matrix-Assisted Laser Desorption Ionization Mass Spectrometry of Compounds Containing Carboxyl Groups Using CdTe and CuO Nanoparticles

    OpenAIRE

    Megumi Sakurai; Taro Sato; Jiawei Xu; Soichi Sato; Tatsuya Fujino

    2018-01-01

    Matrix-assisted laser desorption ionization mass spectrometry of compounds containing carboxyl groups was carried out by using semiconductor nanoparticles (CdTe and CuO) as the matrix. Salicylic acid (Sal), glucuronic acid (Glu), ibuprofen (Ibu), and tyrosine (Tyr) were ionized as deprotonated species (carboxylate anions) by using electrons ejected from CdTe after the photoexcitation. When CuO was used as the matrix, the peak intensity of Tyr became high compared with that obtained with CdTe....

  20. Growth and microtopographic study of CuInSe{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Sanjaysinh M.; Chaki, Sunil, E-mail: sunilchaki@yahoo.co.in; Deshpande, M. P. [Department of Physics, Sardar Patel University, Vallabh Vidyanagar, Gujarat - 388120 (India); Tailor, J. P. [Applied Physics Department, S.V.N.I.T., Surat, Gujarat - 395007 (India)

    2016-05-23

    The CuInSe{sub 2} single crystals were grown by chemical vapour transport (CVT) technique using iodine as transporting agent. The elemental composition of the as-grown CuInSe{sub 2} single crystals was determined by energy dispersive analysis of X-ray (EDAX). The unit cell crystal structure and lattice parameters were determined by X-ray diffraction (XRD) technique. The surface microtopographic study of the as-grown CuInSe{sub 2} single crystals surfaces were done to study the defects, growth mechanism, etc. of the CVT grown crystals.

  1. Annihilation characteristics in as-grown and electron irradiated Zn II-VI semiconductors

    International Nuclear Information System (INIS)

    Moser, P.; La Cruz, R.M. de; Pareja, R.

    1991-01-01

    The temperature dependence of the positron lifetime has been investigated in as-grown crystals of Zns, ZnSe and ZnTe over the temperature range 8-320 K. Also, isochronal annealing experiments up to 1175 K have been performed on these crystals. Zns and ZnSe crystals have been electron irradiated at room temperature and at 77 K. From the results in as-grown and annealed crystals, the values of (230±3), (240±5) and (266±3) ps are attributed to the positron lifetime in the bulk of Zns, ZnSe and ZnTe, respectively. 8 refs., 3 figs

  2. Annihilation characteristics in As-grown and electron irradiated Zn II-VI semiconductors

    International Nuclear Information System (INIS)

    Cruz, R.M. de la; Pareja, R.; Moser, P.

    1992-01-01

    The temperature dependence of the positron lifetime has been investigated in as-grown crystals of ZnS, ZnSe and ZnTe over the temperature range 8-320 K. Also, isochronal annealing experiments up to 1175 K have been performed on these crystals. ZnS and ZnSe crystals have been electron irradiated at room temperature and at 77 K. From the results in as-grown and annealed crystals, the values of (230±3), (240±5) and (266±3) ps are attributed to the positron lifetime in the bulk of ZnS, ZnSe and ZnTe, respectively

  3. Graphic Grown Up

    Science.gov (United States)

    Kim, Ann

    2009-01-01

    It's no secret that children and YAs are clued in to graphic novels (GNs) and that comics-loving adults are positively giddy that this format is getting the recognition it deserves. Still, there is a whole swath of library card-carrying grown-up readers out there with no idea where to start. Splashy movies such as "300" and "Spider-Man" and their…

  4. Homogenization of zinc distribution in vertical Bridgman grown Cd0 ...

    Indian Academy of Sciences (India)

    Unknown

    adopting suitable growth parameters and sufficient post growth annealing it has been possible to grow. Cd0⋅96Zn0⋅04Te crystals, which have nearly 75% of their fraction within 1% Zn concentration variation. Keywords. Bridgman growth; CdZnTe; Zn distribution; solid state diffusion. 1. Introduction. Bridgman grown single ...

  5. CdTe and CdZnTe semiconductor gamma detectors equipped with ohmic contacts

    CERN Document Server

    Lachish, U

    1999-01-01

    Semiconductor gamma detectors, equipped with ohmic contacts, are uniform and fast response devices that are not sensitive to hole trapping. Gamma generated charges flow within the detector bulk towards the ohmic contacts, and induce additional charge flow from the contacts towards them. The additional flow stems from the fundamental principles of Poisson and the continuity equations. Electrons flow from the negative contacts towards the holes and recombine with them, therefore, they overcome hole trapping. The ohmic contact effect transforms the detector into a single carrier device. Good quality ohmic contact detectors are achieved from a crystal grown by standard methods, that initially has too many traps, by adjustment of the Fermi level position within the forbidden band. The device design and its principle of operation are discussed.

  6. Crystal growth and properties of novel organic nonlinear optical crystals of 4-Nitrophenol urea

    Energy Technology Data Exchange (ETDEWEB)

    Mohan, M. Krishna, E-mail: krishnamohan.m@ktr.srmuniv.ac.in; Ponnusamy, S.; Muthamizhchelvan, C.

    2017-07-01

    Single crystals of 4-Nitrophenol urea have been grown from water using slow evaporation technique at constant temperature, with the vision to improve the properties of the crystals. The unit cell parameters of the grown crystals were determined by single crystal and powder X-Ray diffraction. FTIR studies reveals the presence of different vibrational bands. The Optical studies confirmed that the crystal is transparent up to 360 nm .TGA and DSC studies were carried out to understand the thermal behavior of crystals. The SHG studies show the suitability of the crystals for NLO applications. The etching studies were carried out to study the behavior of the crystals under different conditions.These studies reveal that the crystals of 4-Nitrophenol urea are suitable for device applications. - Highlights: • 4-Nitrophenol urea crystals of dimensions 14 mm × 1 mm were grown. • UV–Visible studies indicate the crystal is transparent in the region of 370–800 nm. • Thermal studies show the crystal starts decomposing at 170 °C. • SHG studies indicate that the crystals have NLO efficiency 3.5 times that of KDP.

  7. CdTe quantum dots with daunorubicin induce apoptosis of multidrug-resistant human hepatoma HepG2/ADM cells: in vitro and in vivo evaluation

    Directory of Open Access Journals (Sweden)

    Shi Lixin

    2011-01-01

    Full Text Available Abstract Cadmium telluride quantum dots (Cdte QDs have received significant attention in biomedical research because of their potential in disease diagnosis and drug delivery. In this study, we have investigated the interaction mechanism and synergistic effect of 3-mercaptopropionic acid-capped Cdte QDs with the anti-cancer drug daunorubicin (DNR on the induction of apoptosis using drug-resistant human hepatoma HepG2/ADM cells. Electrochemical assay revealed that Cdte QDs readily facilitated the uptake of the DNR into HepG2/ADM cells. Apoptotic staining, DNA fragmentation, and flow cytometry analysis further demonstrated that compared with Cdte QDs or DNR treatment alone, the apoptosis rate increased after the treatment of Cdte QDs together with DNR in HepG2/ADM cells. We observed that Cdte QDs treatment could reduce the effect of P-glycoprotein while the treatment of Cdte QDs together with DNR can clearly activate apoptosis-related caspases protein expression in HepG2/ADM cells. Moreover, our in vivo study indicated that the treatment of Cdte QDs together with DNR effectively inhibited the human hepatoma HepG2/ADM nude mice tumor growth. The increased cell apoptosis rate was closely correlated with the enhanced inhibition of tumor growth in the studied animals. Thus, Cdte QDs combined with DNR may serve as a possible alternative for targeted therapeutic approaches for some cancer treatments.

  8. Applicability of a portable CdTe and NaI (Tl) spectrometer for activity measure; Aplicabilidade de um espectrometro portatil de CdTe e NaI (Tl) para a medida da atividade de Cesio-137 ({sup 137}Cs) e Berilio-7 ({sup 7}Be)

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, Jaquiel Salvi

    2005-02-15

    In this work it was studied the application of an in situ gamma spectrometer (ROVER) of Amptek Inc., composed by a Cadmium Telluride detector (CdTe) of 3 mm x 3 mm x 1 mm and a 30 mm x 30 mm Sodium Iodide detector doped with Thallium [NaI (Tl)). The radioactive sources used were type pastille, sealed in aluminum and polyethylene, of {sup 241}Am, {sup 133}Ba, {sup 152}Eu, 3 sources of {sup 137}Cs and soil samples contaminated with {sup 137}Cs. It was performed a factorial planning 2{sup 3} to optimize the in situ spectrometry system. This way it was determined that the best temperature for CdTe crystal operation is -22, deg C, with Shaping Time of 3 {mu}S and Rise Time Discrimination (RTD) with value 3. With the help of the certified radioactive sources, we determined the efficiency curve of the two detectors. The CdTe detector was positioned at the standard distance of 1 meter of the sources and also at 4.15 cm. The NaI (Tl) detector was also positioned at the standard distance of 1 meter of the sources and at 2.8 cm. Measures were performed to determine the Minimum Detectable Activity (MDA) for both detectors. For the pastille type sources, the {sup 137}Cs MDA for the CdTe detector at 4.15 cm, analyzing the energy line of 32 keV, was 6 kBq and at 1 meter of the {sup 137}Cs source, analyzing the line of 661.65 keV, the MDA was 67 kBq. For soil samples, CdTe detector at 4.15 cm presented a MDA of 693 kBq.kg-l for the line of 32 keV, and for the soil sample {sup 7}Be content the MDA found was 2867 Bq.kg{sup -1} at 4.15 cm. For the NaI (Tl) detector, analyzing the line of 661.65 keV, the {sup 137}Cs MDA for pastille type source at 1 meter of distance was 7 kBq, and for soil sample at 2.8 cm the measured {sup 137}Cs MDA was 71 Bq.kg{sup -1}. For the soil sample {sup 7}Be content, at 2.8 cm of the Nal (Tl) detector, the obtained MDA was 91 Bq.kg{sup -1}. Due to the minimum detectable activities found for the two detectors, we concluded that the employed in situ gamma

  9. Scientist prepare Lysozyme Protein Crystal

    Science.gov (United States)

    1996-01-01

    Dan Carter and Charles Sisk center a Lysozyme Protein crystal grown aboard the USML-2 shuttle mission. Protein isolated from hen egg-white and functions as a bacteriostatic enzyme by degrading bacterial cell walls. First enzyme ever characterized by protein crystallography. It is used as an excellent model system for better understanding parameters involved in microgravity crystal growth experiments. The goal is to compare kinetic data from microgravity experiments with data from laboratory experiments to study the equilibrium.

  10. 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.)

  11. 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%.

  12. 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.

  13. Deposition and properties of CdTe nanowires prepared by template replication

    International Nuclear Information System (INIS)

    Enculescu, Ionut; Sima, Marian; Enculescu, Monica; Enache, Mihaela; Ion, Lucian; Antohe, Stefan; Neumann, Reinhard

    2007-01-01

    We used the template method to prepare CdTe wires with diameters ranging from 80 nm to 1 μm. As templates we used polycarbonate and polyethilene terephtalate ion track membranes and as the method of filling the pores of such membranes we employed electrochemical deposition. The conditions (i.e. bath composition and deposition potential) necessary to obtain the stoichiometric composition of the semiconductor were found. Scanning and transmission electron microscopy were employed for morphological characterization of the nano and microwires. Energy dispersive X-ray analysis was employed for determining the Cd/Te ratio. Selected area electron diffraction was employed for structural measurements. Reflection spectroscopy measurements were performed on nanowire arrays for determining the band gap of the deposited nanostructures. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. 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.

  15. Photoinduced interaction between MPA capped CdTe QDs and certain anthraquinone dyes

    Energy Technology Data Exchange (ETDEWEB)

    Jagadeeswari, S.; Asha Jhonsi, M.; Kathiravan, A. [School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Renganathan, R., E-mail: rrengas@gmail.co [School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India)

    2011-04-15

    Photoinduced interaction of mercapto propionic acid (MPA) capped CdTe quantum dots (QDs) with certain anthraquinone dyes namely alizarin, alizarin red S, acid blue 129 and uniblue has been studied by steady state and time resolved fluorescence measurements. Addition of anthraquinone dyes to CdTe QDs results in the reduction of electron hole recombination has been observed (i.e., fluorescence quenching). The Stern-Volmer constant (K{sub SV}), quenching rate constant (k{sub q}) and association constants (K) were obtained from fluorescence quenching data. The interaction of anthraquinone dyes with QDs occurs through static quenching was confirmed by unaltered fluorescence lifetime. The occurrence of electron transfer quenching mechanism has been proved by the negative free energy change ({Delta}G{sub et}) obtained as per the Rehm-Weller equation.

  16. Optical Properties of Al- and Sb-Doped CdTe Thin Films

    Directory of Open Access Journals (Sweden)

    A. A. J. Al-Douri

    2010-01-01

    Full Text Available Nondoped and (Al, Sb-doped CdTe thin films with 0.5, 1.5, and 2.5  wt.%, respectively, were deposited by thermal evaporation technique under vacuum onto Corning 7059 glass at substrate temperatures ( of room temperature (RT and 423 K. The optical properties of deposited CdTe films such as band gap, refractive index (n, extinction coefficient (, and dielectric coefficients were investigated as function of Al and Sb wt.% doping, respectively. The results showed that films have direct optical transition. Increasing and the wt.% of both types of dopant, the band gap decrease but the optical is constant as n, and real and imaginary parts of the dielectric coefficient increase.

  17. Sputter-Deposited Oxides for Interface Passivation of CdTe Photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Kephart, Jason M.; Kindvall, Anna; Williams, Desiree; Kuciauskas, Darius; Dippo, Pat; Munshi, Amit; Sampath, W. S.

    2018-03-01

    Commercial CdTe PV modules have polycrystalline thin films deposited on glass, and devices made in this format have exceeded 22% efficiency. Devices made by the authors with a magnesium zinc oxide window layer and tellurium back contact have achieved efficiency over 18%, but these cells still suffer from an open-circuit voltage far below ideal values. Oxide passivation layers made by sputter deposition have the potential to increase voltage by reducing interface recombination. CdTe devices with these passivation layers were studied with photoluminescence (PL) emission spectroscopy and time-resolved photoluminescence (TRPL) to detect an increase in minority carrier lifetime. Because these oxide materials exhibit barriers to carrier collection, micropatterning was used to expose small point contacts while still allowing interface passivation. TRPL decay lifetimes have been greatly enhanced for thin polycrystalline absorber films with interface passivation. Device performance was measured and current collection was mapped spatially by light-beam-induced current.

  18. Fabrication of fluorescent composite with ultrafast aqueous synthesized high luminescent CdTe quantum dots

    International Nuclear Information System (INIS)

    Zhang, Lei; Chen, Haibin; Wu, Jingshen; Bi, Xianghong

    2014-01-01

    Without precursor preparation, inert gas protection and enormous amount of additives and reductants, CdTe quantum dots (QDs) can be rapidly synthesized with high quality. A 600 nm photoluminescence peak wavelength could be obtained within 1 hour's refluxing through minimal addition of 1,2-diaminoethane (DAE). The theoretical design for the experiments are illustrated and further proved by the characterization results with different concentrations and reagents. On the other hand, generation of CdTe QDs was found even under room temperature by applying droplet quantity of DAE. This indicates that QDs can be synthesized with simply a bottle and no enormous additives required. The QDs were mixed into the epoxy matrix through solution casting method with cetyltrimethylammonium (CTA) capping for phase transfer. The acquired epoxy based nanocomposite exhibits good transparency, compatibility and fluorescence

  19. Ion transport in Au doped/undoped KDP crystals with KI/NaI as ...

    Indian Academy of Sciences (India)

    Undoped KDP and KDP crystals containing KI/NaI with/without gold doping were grown by slow evaporation technique. All the grown crystals were -irradiated using 60Co source. Electrical conductivity measurements were carried out on all these crystals perpendicular to the unique direction before and after -irradiation.

  20. Towards true 3-dimensional BCC colloidal crystals with controlled lattice orientation

    NARCIS (Netherlands)

    Dziomkina, N.; Hempenius, Mark A.; Vancso, Gyula J.

    2009-01-01

    A fabrication method of colloidal crystals possessing the BCC crystal structure is described. BCC colloidal crystals with a thickness of up to seven colloidal layers were grown in the direction of the (100) crystal plane. Defect free colloidal crystals with a homogeneous surface coverage were

  1. Applications of CdTe to nuclear medicine. Annual report, February 1, 1979-January 31, 1980

    International Nuclear Information System (INIS)

    Entine, G.

    1980-01-01

    The application of CdTe gamma detectors in nuclear medicine is reported on. An internal probe was developed which can be inserted into the heart to measure the efficiency of various radiopharmaceuticals in the treatment of heart attacks. A second application is an array of detectors which is light enough to be worn by ambulatory patients and can measure the change in cardiac output over an eight hour period during heart attack treatment. The instrument includes an on board tape recorder

  2. Applications of CdTe to nuclear medicine. Annual report, February 1, 1979-January 31, 1980

    Energy Technology Data Exchange (ETDEWEB)

    Entine, G

    1980-01-01

    The application of CdTe gamma detectors in nuclear medicine is reported on. An internal probe was developed which can be inserted into the heart to measure the efficiency of various radiopharmaceuticals in the treatment of heart attacks. A second application is an array of detectors which is light enough to be worn by ambulatory patients and can measure the change in cardiac output over an eight hour period during heart attack treatment. The instrument includes an on board tape recorder. (ACR)

  3. High luminescent L-cysteine capped CdTe quantum dots prepared at different reaction times

    Science.gov (United States)

    Kiprotich, Sharon; Onani, Martin O.; Dejene, Francis B.

    2018-04-01

    This paper reports a facile synthesis route of high luminescent L-cysteine capped CdTe quantum dots (QDs). The effect of reaction time on the growth mechanism, optical and physical properties of the CdTe QDs was investigated in order to find the suitability of them towards optical and medical applications. The representative high-resolution transmission microscopy (HRTEM) analysis showed that the as-obtained CdTe QDs appeared as spherical particles with excellent monodispersity. The images exhibited clear lattice fringes which are indicative of good crystallinity. The X-ray diffraction (XRD) pattern displayed polycrystalline nature of the QDs which correspond well to zinc blende phase of bulk CdTe. The crystallite sizes calculated from the Scherrer equation were less than 10 nm for different reaction times which were in close agreement with the values estimated from HRTEM. An increase in reaction time improved crystallinity of the sample as explained by highest peak intensity of the XRD supported by the photoluminescence emission spectra which showed high intensity at a longer growth time. It was observed that for prolonged growth time the emission bands were red shifted from about 517-557 nm for 5-180 min of reaction time due to increase in particle sizes. Ultraviolet and visible analysis displayed well-resolved absorption bands which were red shifted upon an increase in reaction time. There was an inverse relation between the band gap and reaction time. Optical band gap decreases from 3.98 to 2.59 eV with the increase in reaction time from 15 to 180 min.

  4. 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

  5. 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

  6. Crystals in crystals

    DEFF Research Database (Denmark)

    Christensen, Claus H.; Schmidt, I.; Carlsson, A.

    2005-01-01

    A major factor governing the performance of catalytically active particles supported on a zeolite carrier is the degree of dispersion. It is shown that the introduction of noncrystallographic mesopores into zeolite single crystals (silicalite-1, ZSM-5) may increase the degree of particle dispersion...... of the zeolite particles, particularly after thermal treatment. When using mesoporous zeolites, the particles were evenly distributed throughout the mesopore system of the zeolitic support, even after calcination, leading to nanocrystals within mesoporous zeolite single crystals....

  7. Growth of single crystals of BaFe12O19 by solid state crystal growth

    International Nuclear Information System (INIS)

    Fisher, John G.; Sun, Hengyang; Kook, Young-Geun; Kim, Joon-Seong; Le, Phan Gia

    2016-01-01

    Single crystals of BaFe 12 O 19 are grown for the first time by solid state crystal growth. Seed crystals of BaFe 12 O 19 are buried in BaFe 12 O 19 +1 wt% BaCO 3 powder, which are then pressed into pellets containing the seed crystals. During sintering, single crystals of BaFe 12 O 19 up to ∼130 μm thick in the c-axis direction grow on the seed crystals by consuming grains from the surrounding polycrystalline matrix. Scanning electron microscopy-energy dispersive spectroscopy analysis shows that the single crystal and the surrounding polycrystalline matrix have the same chemical composition. Micro-Raman scattering shows the single crystal to have the BaFe 12 O 19 structure. The optimum growth temperature is found to be 1200 °C. The single crystal growth behavior is explained using the mixed control theory of grain growth. - Highlights: • Single crystals of BaFe 12 O 19 are grown by solid state crystal growth. • A single crystal up to ∼130 μm thick (c-axis direction) grows on the seed crystal. • The single crystal and surrounding ceramic matrix have similar composition. • Micro-Raman scattering shows the single crystal has the BaFe 12 O 19 structure.

  8. 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.

  9. 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.

  10. Comparison of structural properties of thermally evaporated CdTe thin films on different substrates

    International Nuclear Information System (INIS)

    Tariq, G.H.; Anis-ur-Rehman, M.

    2011-01-01

    The direct energy band gap in the range of 1.5 eV and the high absorption coefficient (105 cm/sup -1/) makes Cadmium Telluride (CdTe) a suitable material for fabrication of thin film solar cells. Thin film solar cells based on CdTe (1 cm area) achieved efficiency of 15.6% on a laboratory scale. CdTe thin films were deposited by thermal evaporation technique under vacuum 2 X 10/sup -5/mbar on glass and stainless steel (SS) substrates. During deposition substrates temperature was kept same at 200 deg. C for all samples. The structural properties were determined by the X-ray Diffraction (XRD) patterns. All samples exhibit polycrystalline nature. Dependence of different structural parameters such as lattice parameter, micro strain, and grain size and dislocation density on thickness was studied. Also the influence of the different substrates on these parameters was investigated. The analysis showed that the preferential orientation of films was dependent on the substrate type. (author)

  11. 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

  12. Prototype of high resolution PET using resistive electrode position sensitive CdTe detectors

    International Nuclear Information System (INIS)

    Kikuchi, Yohei; Ishii, Keizo; Matsuyama, Shigeo; Yamazaki, Hiromichi

    2008-01-01

    Downsizing detector elements makes it possible that spatial resolutions of positron emission tomography (PET) cameras are improved very much. From this point of view, semiconductor detectors are preferable. To obtain high resolution, the pixel type or the multi strip type of semiconductor detectors can be used. However, in this case, there is a low packing ratio problem, because a dead area between detector arrays cannot be neglected. Here, we propose the use of position sensitive semiconductor detectors with resistive electrode. The CdTe detector is promising as a detector for PET camera because of its high sensitivity. In this paper, we report development of prototype of high resolution PET using resistive electrode position sensitive CdTe detectors. We made 1-dimensional position sensitive CdTe detectors experimentally by changing the electrode thickness. We obtained 750 A as an appropriate thickness of position sensitive detectors, and evaluated the performance of the detector using a collimated 241 Am source. A good position resolution of 1.2 mm full width half maximum (FWHM) was obtained. On the basis of the fundamental development of resistive electrode position sensitive detectors, we constructed a prototype of high resolution PET which was a dual head type and was consisted of thirty-two 1-dimensional position sensitive detectors. In conclusion, we obtained high resolutions which are 0.75 mm (FWHM) in transaxial, and 1.5 mm (FWHM) in axial. (author)

  13. Spectral correction algorithm for multispectral CdTe x-ray detectors

    Science.gov (United States)

    Christensen, Erik D.; Kehres, Jan; Gu, Yun; Feidenhans'l, Robert; Olsen, Ulrik L.

    2017-09-01

    Compared to the dual energy scintillator detectors widely used today, pixelated multispectral X-ray detectors show the potential to improve material identification in various radiography and tomography applications used for industrial and security purposes. However, detector effects, such as charge sharing and photon pileup, distort the measured spectra in high flux pixelated multispectral detectors. These effects significantly reduce the detectors' capabilities to be used for material identification, which requires accurate spectral measurements. We have developed a semi analytical computational algorithm for multispectral CdTe X-ray detectors which corrects the measured spectra for severe spectral distortions caused by the detector. The algorithm is developed for the Multix ME100 CdTe X-ray detector, but could potentially be adapted for any pixelated multispectral CdTe detector. The calibration of the algorithm is based on simple attenuation measurements of commercially available materials using standard laboratory sources, making the algorithm applicable in any X-ray setup. The validation of the algorithm has been done using experimental data acquired with both standard lab equipment and synchrotron radiation. The experiments show that the algorithm is fast, reliable even at X-ray flux up to 5 Mph/s/mm2, and greatly improves the accuracy of the measured X-ray spectra, making the algorithm very useful for both security and industrial applications where multispectral detectors are used.

  14. Impacts of Temperature on the Performance of Cdte Based Thin-Film Solar Cell

    Science.gov (United States)

    Asaduzzaman, Md.; Newaz Bahar, Ali; Maksudur Rahman Bhuiyan, Mohammad; Habib, Md. Ahsan

    2017-08-01

    In this investigation, the effect of temperature on the performance of CdTe based thin film solar cells has been studied. The parameters such as open circuit voltage (Voc ), short circuit current density (Jsc ), fill factor and efficiency η determines the performance of solar cell. And an important diode parameter, reverse saturation current density, J 0 controls the impacts of temperature on the performance parameters. The reverse saturation current density of the CdTe photovoltaic cell, J 0 = CT 3exp(-qEg /kT) was determinedas optimum for C = 17.90 mAcm -2 K 3 yields CT 3 = 4.74 × 108 mAcm -2. In this case, 298 K is considered to be more suitable temperature to achieve optimized Voc, Jsc, FF, and η calculated for AM1.5G illumination spectra. The maximum attained values of performance parameters are compared with the experimental and theoretical results in the literature of CdTe solar cells. Moreover, the rate of change in performance parameters due to temperature are also measured and compared with the results available in the earlier published works.

  15. Spatially Resolved Cathodoluminescence of CdTe Thin Films and Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Romero, M. J.; Metzger, W.; Gessert, T. A.; Albin, D. S.; Al-Jassim, M. M.

    2003-05-01

    We have investigated the spatial distribution of different transitions identified in the emission spectra of CdTe thin films and solar cells by cathodoluminescence spectroscopic imaging (CLSI). Prior to back-contact deposition, the spectra are dominated by excitons (X) and donor-to-acceptor (DAP) transitions. After contacting, Cu acceptor states are found in addition to the X and DAP recombination processes. A very systematic behavior found in CdTe is that DAP transitions occur preferentially at grain boundaries (GBs). The distribution of these states responsible for the passivation of GBs is not affected by further processing, although additional levels participate in the recombination process. We believe that this stability is one of the reasons for the success of thin-film CdTe solar cells. Estimates of the densities of different donors and acceptors participating in the recombination process are possible from the analysis of the evolution of the emission spectra with the excitation level. It is found that the back contact suppresses some intrinsic acceptors (associated with the A center) near the back-contact interface and, therefore, Cu acceptor states should be responsible for the p-typeness of the back surface more than a reduction of compensation. CLSI measurements are shown to be helpful in understanding the physics of back-contact formation.

  16. 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.

  17. 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.

  18. 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.

  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. Phenomenon of ''self-cleaning'' of crystals

    International Nuclear Information System (INIS)

    Matveev, O.A.; Arkad'eva, E.N.; Goncharov, L.A.

    1975-01-01

    Crystals of germanium and cadmium telluride have been produced having the characteristics corresponding to the low content of electrically active impurities and crystal defects. The crystals have been grown under conditions of an equilibrium diffusion-concentration interaction of the impurities and crystal defects, with the donor alloying and controlling the acceptors concentration. These crystals have been studied with the help of the mass-spectral analysis, the Hall effect, photoelectroscopy, spectral photoconductivity and losses of collection of a charge from an ionizing particle on gamma-detectors fabricated of the crystals. Herein the doped composition of the crystals has been determined, the concentrations of the shallow and deep acceptors and donors have been measured separately, the life-times of the electrons and holes have been measured, the energetic position and the concentration of the carrier capture levels have been determined. The crystals grown possess all the characteristic features of rather pure crystals. The results of the mass-spectral analysis have shown that in the cadmium telluride crystals the impurities are present within 10 14 to 10 17 cm -3 . Therefore, a deep ''self-refining'' of the crystal takes place, which proceeds by means of deactivation of the electrically active centers with their associating into electrically inactive complexes. Thus a fact of the deep ''self-refining'' of germanium- and cadmium telluride crystals is stated. It is presumed that such a ''self-refining'' can actually proceed practically in all the crystals