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Sample records for n-type modulation doped

  1. Potassium-doped n-type bilayer graphene

    Science.gov (United States)

    Yamada, Takatoshi; Okigawa, Yuki; Hasegawa, Masataka

    2018-01-01

    Potassium-doped n-type bilayer graphene was obtained. Chemical vapor deposited bilayer and single layer graphene on copper (Cu) foils were used. After etching of Cu foils, graphene was dipped in potassium hydroxide aqueous solutions to dope potassium. Graphene on silicon oxide was characterized by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and Raman spectroscopy. Both XPS and EDX spectra indicated potassium incorporation into the bilayer graphene via intercalation between the graphene sheets. The downward shift of the 2D peak position of bilayer graphene after the potassium hydroxide (KOH) treatment was confirmed in Raman spectra, indicating that the KOH-treated bilayer graphene was doped with electrons. Electrical properties were measured using Hall bar structures. The Dirac points of bilayer graphene were shifted from positive to negative by the KOH treatment, indicating that the KOH-treated bilayer graphene was n-type conduction. For single layer graphene after the KOH treatment, although electron doping was confirmed from Raman spectra, the peak of potassium in the X-ray photoelectron spectroscopy (XPS) spectrum was not detected. The Dirac points of single layer graphene with and without the KOH treatment showed positive.

  2. Excitonic optical bistability in n-type doped semiconductors

    International Nuclear Information System (INIS)

    Nguyen Ba An; Le Thi Cat Tuong

    1991-07-01

    A resonant monochromatic pump laser generates coherent excitons in an n-type doped semiconductor. Both exciton-exciton and exciton-donor interactions come into play. The former interaction can give rise to the appearance of optical bistability which is heavily influenced by the latter one. When optical bistability occurs at a fixed laser frequency both its holding intensity and hysteresis loop size are shown to decrease with increasing donor concentration. Two possibilities are suggested for experimentally determining one of the two parameters of the system - the exciton-donor coupling constant and the donor concentration, if the other parameter is known beforehand. (author). 36 refs, 2 figs

  3. Origins of n -type doping difficulties in perovskite stannates

    Science.gov (United States)

    Weston, L.; Bjaalie, L.; Krishnaswamy, K.; Van de Walle, C. G.

    2018-02-01

    The perovskite stannates (A SnO3 ; A = Ba, Sr, Ca) are promising for oxide electronics, but control of n -type doping has proved challenging. Using first-principles hybrid density functional calculations, we investigate La dopants and explore the formation of compensating acceptor defects. We find that La on the A site always behaves as a shallow donor, but incorporation of La on the Sn site can lead to self-compensation. At low La concentrations and in O-poor conditions, oxygen vacancies form in BaSnO3. A -site cation vacancies are found to be dominant among the native compensating centers. Compared to BaSnO3, charge compensation is a larger problem for the wider-band-gap stannates, SrSnO3 and CaSnO3, a trend we can explain based on conduction-band alignments. The formation of compensating acceptor defects can be inhibited by choosing oxygen-poor (cation-rich) growth or annealing conditions, thus providing a pathway for improved n -type doping.

  4. Air-stable n-type doping of graphene from overlying Si3N4 film

    International Nuclear Information System (INIS)

    Wang, Zegao; Li, Pingjian; Chen, Yuanfu; Liu, Jingbo; Qi, Fei; Tian, Hongjun; Zheng, Binjie; Zhou, Jinhao

    2014-01-01

    In this study, we report a facile method to obtain air-stable n-type graphene by plasma-enhanced chemical vapor depositing Si 3 N 4 film on the surface of graphene. We have demonstrated that the overlying Si 3 N 4 film can not only act as the penetration-barrier against H 2 O and O 2 adsorbed on the graphene surface, but also cause an effective n-type doping due to the amine groups at the interface of graphene/Si 3 N 4 . Furthermore, the studies reveal that the Dirac point of graphene can be modulated by the thickness of Si 3 N 4 film, which is due to competing effects of Si 3 N 4 -induced doping (n-type) and penetrating H 2 O (O 2 )-induced doping (p-type). We expect this method to be used for obtaining stable n-type graphene field-effect transistors in air, which will be widely used in graphene electronic devices.

  5. Understanding the effect of n-type and p-type doping in the channel ...

    Indian Academy of Sciences (India)

    channel device remains unsaturated. On comparing figures 2–8, we observe larger variations in on and off-currents in n-type-doped structure in compari- son with p-type-doped and undoped channel structures. It is also possible to obtain the important saturation characteris- tics on introducing n-type-doping near drain side, ...

  6. Understanding the effect of n-type and p-type doping in the channel ...

    Indian Academy of Sciences (India)

    type doping in the channel is better with smaller supply voltage compared to higher supply voltage. On increasing the n -type doping concentration, we obtained better on-current and output characteristics in comparison with undoped and p ...

  7. Thermophotovoltaic energy conversion system having a heavily doped n-type region

    Science.gov (United States)

    DePoy, David M.; Charache, Greg W.; Baldasaro, Paul F.

    2000-01-01

    A thermophotovoltaic (TPV) energy conversion semiconductor device is provided which incorporates a heavily doped n-type region and which, as a consequence, has improved TPV conversion efficiency. The thermophotovoltaic energy conversion device includes an emitter layer having first and second opposed sides and a base layer in contact with the first side of the emitter layer. A highly doped n-type cap layer is formed on the second side of the emitter layer or, in another embodiment, a heavily doped n-type emitter layer takes the place of the cap layer.

  8. Scandium-doped zinc cadmium oxide as a new stable n-type oxide thermoelectric material

    DEFF Research Database (Denmark)

    Han, Li; Christensen, Dennis Valbjørn; Bhowmik, Arghya

    2016-01-01

    Scandium-doped zinc cadmium oxide (Sc-doped ZnCdO) is proposed as a new n-type oxide thermoelectric material. The material is sintered in air to maintain the oxygen stoichiometry and avoid instability issues. The successful alloying of CdO with ZnO at a molar ratio of 1 : 9 significantly reduced...

  9. n-Type phosphorus-doped nanocrystalline diamond: electrochemical and in situ Raman spectroelectrochemical study

    OpenAIRE

    Zivcova, Z. Vlckova; Frank, O.; Drijkoningen, Sien; Haenen, Ken; Mortet, Vincent; Kavan, L.

    2016-01-01

    Electrochemical and in situ Raman spectroelectrochemical characterization of n-type phosphorus-doped nanocrystalline diamond (P-NCD) is carried out. The P-NCD films are grown by microwave plasma enhanced chemical vapour deposition and doped with phosphorus at a concentration of 10 000 ppm in the gas phase. Micro-Raman spectroscopy determines the film quality (presence of graphitic or amorphous phases). All electrochemical measurements are performed in aqueous 0.5 M H2SO4 electrolyte solution....

  10. n-Type Doping of Vapor–Liquid–Solid Grown GaAs Nanowires

    Directory of Open Access Journals (Sweden)

    Gutsche Christoph

    2011-01-01

    Full Text Available Abstract In this letter, n-type doping of GaAs nanowires grown by metal–organic vapor phase epitaxy in the vapor–liquid–solid growth mode on (111B GaAs substrates is reported. A low growth temperature of 400°C is adjusted in order to exclude shell growth. The impact of doping precursors on the morphology of GaAs nanowires was investigated. Tetraethyl tin as doping precursor enables heavily n-type doped GaAs nanowires in a relatively small process window while no doping effect could be found for ditertiarybutylsilane. Electrical measurements carried out on single nanowires reveal an axially non-uniform doping profile. Within a number of wires from the same run, the donor concentrations ND of GaAs nanowires are found to vary from 7 × 1017 cm-3 to 2 × 1018 cm-3. The n-type conductivity is proven by the transfer characteristics of fabricated nanowire metal–insulator-semiconductor field-effect transistor devices.

  11. Complementary p- and n-type polymer doping for ambient stable graphene inverter.

    Science.gov (United States)

    Yun, Je Moon; Park, Seokhan; Hwang, Young Hwan; Lee, Eui-Sup; Maiti, Uday; Moon, Hanul; Kim, Bo-Hyun; Bae, Byeong-Soo; Kim, Yong-Hyun; Kim, Sang Ouk

    2014-01-28

    Graphene offers great promise to complement the inherent limitations of silicon electronics. To date, considerable research efforts have been devoted to complementary p- and n-type doping of graphene as a fundamental requirement for graphene-based electronics. Unfortunately, previous efforts suffer from undesired defect formation, poor controllability of doping level, and subtle environmental sensitivity. Here we present that graphene can be complementary p- and n-doped by simple polymer coating with different dipolar characteristics. Significantly, spontaneous vertical ordering of dipolar pyridine side groups of poly(4-vinylpyridine) at graphene surface can stabilize n-type doping at room-temperature ambient condition. The dipole field also enhances and balances the charge mobility by screening the impurity charge effect from the bottom substrate. We successfully demonstrate ambient stable inverters by integrating p- and n-type graphene transistors, which demonstrated clear voltage inversion with a gain of 0.17 at a 3.3 V input voltage. This straightforward polymer doping offers diverse opportunities for graphene-based electronics, including logic circuits, particularly in mechanically flexible form.

  12. n-type diamond growth by phosphorus doping on (0 0 1)-oriented surface

    International Nuclear Information System (INIS)

    Kato, Hiromitsu; Makino, Toshiharu; Yamasaki, Satoshi; Okushi, Hideyo

    2007-01-01

    The properties of phosphorus incorporation for n-type doping of diamond are discussed and summarized. Doping of (0 0 1)-oriented diamond is introduced and compared with results achieved on (1 1 1) diamond. This review describes detailed procedures and conditions of plasma-enhanced chemical vapour deposition (CVD) growth and characteristics of electrical properties of phosphorus-doped diamond. The phosphorus incorporation was characterized by SIMS analysis including mapping. n-type conductivity is evaluated by Hall-effect measurements over a temperature regime of 300-1000 K. The crystal perfection of (0 0 1)-oriented n-type diamond is also evaluated by x-ray diffraction, Raman spectroscopy, reflection high-energy electron diffraction and cathodoluminescence analyses. The results show that phosphorus atoms are incorporated into the diamond network during (0 0 1) CVD diamond growth and that phosphorus acts as a donor as in (1 1 1)-oriented diamond. This result eliminates the restriction on substrate orientation, which had previously created a bottleneck in the development of diamond electronic devices. (review article)

  13. Realization of N-Type Semiconducting of Phosphorene through Surface Metal Doping and Work Function Study

    Directory of Open Access Journals (Sweden)

    Haocheng Sun

    2018-01-01

    Full Text Available Phosphorene becomes an important member of the layered nanomaterials since its discovery for the fabrication of nanodevices. In the experiments, pristine phosphorene shows p-type semiconducting with no exception. To reach its full capability, n-type semiconducting is a necessity. Here, we report the electronic structure engineering of phosphorene by surface metal atom doping. Five metal elements, Cu, Ag, Au, Li, and Na, have been considered which could form stable adsorption on phosphorene. These elements show patterns in their electron configuration with one valence electron in their outermost s-orbital. Among three group 11 elements, Cu can induce n-type degenerate semiconducting, while Ag and Au can only introduce localized impurity states. The distinct ability of Cu, compared to Ag and Au, is mainly attributed to the electronegativity. Cu has smaller electronegativity and thus denotes its electron to phosphorene, upshifting the Fermi level towards conduction band, resulting in n-type semiconducting. Ag and Au have larger electronegativity and hardly transfer electrons to phosphorene. Parallel studies of Li and Na doping support these findings. In addition, Cu doping effectively regulates the work function of phosphorene, which gradually decreases upon increasing Cu concentration. It is also interesting that Au can hardly change the work function of phosphorene.

  14. Stability of alkali-metal hydrides: effects of n-type doping

    Science.gov (United States)

    Olea Amezcua, Monica Araceli; de La Peña Seaman, Omar; Rivas Silva, Juan Francisco; Heid, Rolf; Bohnen, Klaus-Peter

    Metal hydrides could be considered ideal solid-state hydrogen storage systems, they have light weight and high hydrogen volumetric densities, but the hydrogen desorption process requires excessively high temperatures due to their high stability. Efforts have been performed to improve their dehydrogenation properties, based on the introduction of defects, impurities and doping. We present a systematic study of the n-type (electronic) doping effects on the stability of two alkali-metal hydrides: Na1-xMgxH and Li1-xBexH. These systems have been studied within the framework of density functional perturbation theory, using a mixed-basis pseudopotential method and the self-consistent version of the virtual crystal approximation to model the doping. The full-phonon dispersions are analyzed for several doping content, paying special attention to the crystal stability. It is found a doping content threshold for each system, where they are close to dynamical instabilities, which are related to charge redistribution in interstitial zones. Applying the quasiharmonic approximation, the vibrational free energy, the linear thermal expansion and heat capacities are obtained for both hydrides systems and are analyzed as a function of the doping content. This work is partially supported by the VIEP-BUAP 2016 and CONACYT-México (No.221807) projects.

  15. Thick homoepitaxial (110)-oriented phosphorus-doped n-type diamond

    Energy Technology Data Exchange (ETDEWEB)

    Balasubramaniam, Y.; Pobedinskas, P., E-mail: paulius.pobedinskas@uhasselt.be; Janssens, S. D.; Nesládek, M.; Haenen, K., E-mail: ken.haenen@uhasselt.be [Institute for Materials Research (IMO), Hasselt University, Wetenschapspark 1, B-3590 Diepenbeek (Belgium); IMOMEC, IMEC vzw, Wetenschapspark 1, B-3590 Diepenbeek (Belgium); Sakr, G.; Jomard, F.; Barjon, J. [Groupe d' Etude de la Matière Condensée (GEMaC), Université de Versailles St. Quentin en Yvelines, CNRS, Université Paris Saclay, 45 ave. des Etats-Unis, F-78035 Versailles (France); Turner, S.; Lu, Y.-G.; Verbeeck, J. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Dexters, W. [Institute for Materials Research (IMO), Hasselt University, Wetenschapspark 1, B-3590 Diepenbeek (Belgium); Soltani, A. [Institut d' Electronique, Microélectronique et Nanotechnologie (IEMN/CNRS 8520), Université Lille, Ave. Poincaré-BP 60069, F-59652 Villeneuve d' Ascq (France)

    2016-08-08

    The fabrication of n-type diamond is essential for the realization of electronic components for extreme environments. We report on the growth of a 66 μm thick homoepitaxial phosphorus-doped diamond on a (110)-oriented diamond substrate, grown at a very high deposition rate of 33 μm h{sup −1}. A pristine diamond lattice is observed by high resolution transmission electron microscopy, which indicates the growth of high quality diamond. About 2.9 × 10{sup 16} cm{sup −3} phosphorus atoms are electrically active as substitutional donors, which is 60% of all incorporated dopant atoms. These results indicate that P-doped (110)-oriented diamond films deposited at high growth rates are promising candidates for future use in high-power electronic applications.

  16. Doping dependent crystal structures and optoelectronic properties of n-type CdSe:Ga nanowries.

    Science.gov (United States)

    Hu, Zhizhong; Zhang, Xiujuan; Xie, Chao; Wu, Chunyan; Zhang, Xiaozhen; Bian, Liang; Wu, Yiming; Wang, Li; Zhang, Yuping; Jie, Jiansheng

    2011-11-01

    Although CdSe nanostructures possess excellent electrical and optical properties, efforts to make nano-optoelectronic devices from CdSe nanostructures have been hampered by the lack of efficient methods to rationally control their structural and electrical characteristics. Here, we report CdSe nanowires (NWs) with doping dependent crystal structures and optoelectronic properties by using gallium (Ga) as the efficient n-type dopant via a simple thermal co-evaporation method. The phase change of CdSe NWs from wurtzite to zinc blende with increased doping level is observed. Systematical measurements on the transport properties of the CdSe:Ga NWs reveal that the NW conductivity could be tuned in a wide range of near nine orders of magnitude by adjusting the Ga doping level and a high electron concentration up to 4.5 × 10(19) cm(-3) is obtained. Moreover, high-performance top-gate field-effect transistors are constructed based on the individual CdSe:Ga NWs by using high-κ HfO(2) as the gate dielectric. The great potential of the CdSe:Ga NWs as high-sensitive photodetectors and nanoscale light emitters is also exploited, revealing the promising applications of the CdSe:Ga NWs in new-generation nano-optoelectronics.

  17. Spin relaxation through lateral spin transport in heavily doped n -type silicon

    Science.gov (United States)

    Ishikawa, M.; Oka, T.; Fujita, Y.; Sugiyama, H.; Saito, Y.; Hamaya, K.

    2017-03-01

    We experimentally study temperature-dependent spin relaxation including lateral spin diffusion in heavily doped n -type silicon (n+-Si ) layers by measuring nonlocal magnetoresistance in small-sized CoFe/MgO/Si lateral spin-valve (LSV) devices. Even at room temperature, we observe large spin signals, 50-fold the magnitude of those in previous works on n+-Si . By measuring spin signals in LSVs with various center-to-center distances between contacts, we reliably evaluate the temperature-dependent spin diffusion length (λSi) and spin lifetime (τSi). We find that the temperature dependence of τSi is affected by that of the diffusion constant in the n+-Si layers, meaning that it is important to understand the temperature dependence of the channel mobility. A possible origin of the temperature dependence of τSi is discussed in terms of the recent theories by Dery and co-workers.

  18. Solution-Processed n-Type Graphene Doping for Cathode in Inverted Polymer Light-Emitting Diodes.

    Science.gov (United States)

    Kwon, Sung-Joo; Han, Tae-Hee; Kim, Young-Hoon; Ahmed, Towfiq; Seo, Hong-Kyu; Kim, Hobeom; Kim, Dong Jin; Xu, Wentao; Hong, Byung Hee; Zhu, Jian-Xin; Lee, Tae-Woo

    2018-02-07

    n-Type doping with (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl) dimethylamine (N-DMBI) reduces a work function (WF) of graphene by ∼0.45 eV without significant reduction of optical transmittance. Solution process of N-DMBI on graphene provides effective n-type doping effect and air-stability at the same time. Although neutral N-DMBI act as an electron receptor leaving the graphene p-doped, radical N-DMBI acts as an electron donator leaving the graphene n-doped, which is demonstrated by density functional theory. We also verify the suitability of N-DMBI-doped n-type graphene for use as a cathode in inverted polymer light-emitting diodes (PLEDs) by using various analytical methods. Inverted PLEDs using a graphene cathode doped with N-DMBI radical showed dramatically improved device efficiency (∼13.8 cd/A) than did inverted PLEDs with pristine graphene (∼2.74 cd/A). N-DMBI-doped graphene can provide a practical way to produce graphene cathodes with low WF in various organic optoelectronics.

  19. Impedance and g-r noise of n-type gold-doped silicon under space-charge conditions

    NARCIS (Netherlands)

    Kleinpenning, Th.G.M.

    1972-01-01

    Impedance and current-noise measurements were made on n-type gold-doped silicon single crystals provided with electron-injecting contacts. The d.c. current is proportional to the applied voltage in the ohmic regime considered here. The capacitance is both frequency and d.c. bias dependent at

  20. Very Heavily Doped N-Type GaAs Obtained With Pulsed Laser Annealing

    Science.gov (United States)

    Rys, Andrzej; Chin, Tim; Compaan, Alvin; Bhat, Ajit

    1988-08-01

    A study of carrier activation and mobility was performed in pulsed laser annealed samples of GaAs implanted with doses of Si and Se from 2.2x1012 to 6.0x1014 cm-2. The samples were annealed using a pulsed XeCl excimer laser ( λ=308 nm) and a pulsed dye laser ( λ=728 nm) with energy densities from 0.1 to 0.9 J/cm2 and a 10 nsec pulse. Very high carrier concentrations of 3x1019 and 1.5x1019 cm-3 were obtained for best n-type GaAs samples annealed with the dye laser and excimer laser, respectively. Dye laser consistently produced higher activation than excimer laser annealing. A transient reflectivity experiment was performed to identify the GaAs melt threshold and the melt phase dynamics of the GaAs,under the nitride cap. The threshold energies for cap damage were 0.34 and 0.12 J/cm2 for excimer and dye lasers, respectively. High carrier activation, as measured by Van der Pauw method, was achieved even for lightly doped samples although the room temperature Hall mobility was low. Raman spectroscopy was used to identify the threshold energies for the GaAs implant layer recrystallization and for optimum carrier activation.

  1. High power n-type metal-wrap-through cells and modules using industrial processes

    Energy Technology Data Exchange (ETDEWEB)

    Guillevin, N.; Heurtault, B.J.B.; Geerligs, L.J.; Van Aken, B.B.; Bennett, I.J.; Jansen, M.J.; Weeber, A.W.; Bultman, J.H. [ECN Solar Energy, P.O. Box 1, NL-1755 ZG Petten (Netherlands); Jianming, Wang; Ziqian, Wang; Jinye, Zhai; Zhiliang, Wan; Shuquan, Tian; Wenchao, Zhao; Zhiyan, Hu; Gaofei, Li; Bo, Yu; Jingfeng, Xiong [Yingli Green Energy Holding Co.,Ltd. 3399 North Chaoyang Avenue, Baoding (China)

    2013-10-15

    This paper reviews our recent progress in the development of metal wrap through (MWT) cells and modules, produced from n-type Czochralski silicon wafers. The use of n-type silicon as base material allows for high efficiencies: for front emitter-contacted industrial cells, efficiencies above 20% have been reported. N-type MWT (nMWT) cells produced by industrial process technologies allow even higher efficiency due to reduced front metal coverage. Based on the same industrial technology, the efficiency of the bifacial n-MWT cells exceeds the efficiency of the n-type front-and-rear contact and bifacial 'Pasha' technology (n-Pasha) by 0.1-0.2% absolute, with a maximum nMWT efficiency of 20.1% so far. Additionally, full back-contacting of the MWT cells in a module results in reduced cell to module (CTM) fill factor losses. In a direct 60-cell module performance comparison, the n-MWT module, based on integrated backfoil, produced 3% higher power output than the comparable tabbed front emitter-contacted n-Pasha module. Thanks to reduced resistive losses in copper circuitry on the backfoil compared to traditional tabs, the CTM FF loss of the MWT module was reduced by about 2.2%abs. compared to the tabbed front emitter contact module. A full-size module made using MWT cells of 19.6% average efficiency resulted in a power output close to 280W. Latest results of the development of the n-MWT technology at cell and module level are discussed in this paper, including a recent direct comparison run between n-MWT and n-Pasha cells and results of n-MWT cells from 140{mu}m thin mono-crystalline wafers, with only very slight loss (1% of Isc) for the thin cells. Also reverse characteristics and effects of reverse bias for extended time at cell and module level are reported, where we find a higher tolerance of MWT modules than tabbed front contact modules for hotspots.

  2. Thermoelectric properties of rare earth-doped n-type Bi2Se0∙3Te2∙7 ...

    Indian Academy of Sciences (India)

    Administrator

    The thermoelectric property results show that Ce, Y and Sm doping not only help to decrease the electrical resistivity, but also help to ... of solid-state electronic cooling and power generation. The efficiency of TE devices is strongly ... Bi2Te3 and its related alloys, including p-type BixSb2–x. Te3 and n-type Bi2Te3–xSex, still ...

  3. Low temperature fabrication and doping concentration analysis of Au/Sb ohmic contacts to n-type Si

    Directory of Open Access Journals (Sweden)

    J. Q. Liu

    2015-11-01

    Full Text Available This paper investigates low temperature ohmic contact formation of Au/Sb to n-type Si substrates through AuSb/NiCr/Au metal stacks. Liquid epitaxy growth is utilized to incorporate Sb dopants into Si substrate in AuSi melt. The best specific contact resistivity achieved is 0.003 Ω ⋅ cm2 at 425 oC. Scanning electron microscopy (SEM reveals inverted pyramidal crater regions at the metal/semiconductor interface, indicating that AuSi alloying efficiently occurs at such sites. Secondary ion mass spectroscopy (SIMS shows that Sb atoms are successfully incorporated into Si as doping impurities during the anneal process, and the Sb doping concentration at the contact interface is found to be higher than the solid solubility limit in a Si crystal. This ohmic contacts formation method is suitable for semiconductor fabrication processes with limited thermal budget, such as post CMOS integration of MEMS.

  4. Low temperature fabrication and doping concentration analysis of Au/Sb ohmic contacts to n-type Si

    Energy Technology Data Exchange (ETDEWEB)

    Liu, J. Q.; Wang, C.; Zhu, T.; Wu, W. J. [MOE Key Laboratory of Fundamental Physical Quantities Measurement, School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Fan, J.; Tu, L. C., E-mail: tlc@hust.edu.cn [MOE Key Laboratory of Fundamental Physical Quantities Measurement, School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Institute of Geophysics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2015-11-15

    This paper investigates low temperature ohmic contact formation of Au/Sb to n-type Si substrates through AuSb/NiCr/Au metal stacks. Liquid epitaxy growth is utilized to incorporate Sb dopants into Si substrate in AuSi melt. The best specific contact resistivity achieved is 0.003 Ω ⋅ cm{sup 2} at 425 {sup o}C. Scanning electron microscopy (SEM) reveals inverted pyramidal crater regions at the metal/semiconductor interface, indicating that AuSi alloying efficiently occurs at such sites. Secondary ion mass spectroscopy (SIMS) shows that Sb atoms are successfully incorporated into Si as doping impurities during the anneal process, and the Sb doping concentration at the contact interface is found to be higher than the solid solubility limit in a Si crystal. This ohmic contacts formation method is suitable for semiconductor fabrication processes with limited thermal budget, such as post CMOS integration of MEMS.

  5. Photo-Hall measurements on phosphorus-doped n-type CVD diamond at low temperatures

    Czech Academy of Sciences Publication Activity Database

    Remeš, Zdeněk; Kalish, R.; Uzan-Saguy, C.; Baskin, E.; Nesládek, M.; Koizumi, S.

    2003-01-01

    Roč. 199, č. 1 (2003), s. 82-86 ISSN 0031-8965 EU Projects: European Commission(XE) HPRN-CT-1999-00139 Institutional research plan: CEZ:AV0Z1010914 Keywords : photo-Hall measurements * CVD diamonnd * phosphorus doped Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.950, year: 2003

  6. Nitrogen doped n-type CdS nanoribbons with tunable electrical and photoelectrical properties.

    Science.gov (United States)

    Wu, Bo; Jiang, Yang; Wu, Di; Li, Shanying; Wang, Li; Yu, Yongqing; Wang, Zhuangbing; Jie, Jiansheng

    2011-03-01

    Single-crystal nitrogen doped CdS nanoribbons (NRs) with wurtzite structure were synthesized in ammonia atmosphere via a thermal evaporation deposition route. X-ray diffraction patterns reveal a significant contraction of the lattice constants due to the incorporation of nitrogen. Temperature-varied photoluminescence spectra of CdS:N NRs exhibit spectral features near the band edge, which can be ascribed to free excition and neutral acceptor-bound excition emissions. Electrical and photoelectrical properties of the CdS:N NRs were systemically studied by constructing the field-effect transistors based on individual NRs. The conductivity of the NRs can be tuned by two orders of magnitude by controlling the N doping concentration. Moreover, by post-annealing, the device performance is remarkably improved, in particular, the mobility of the CdS:N NRs is increased by nearly three orders of magnitude from approximately 10(-1) to hundreds of cm2/Vs. I(on)I(off) ratio of the annealed device reaches over 10(4). Photoconductive properties of the CdS:N NRs were also studied. The doped NRs show high sensitivity to the light with energy larger than band-gap and the response amplitude and speed depend on the doping concentration.

  7. Understanding the effect of n-type and p-type doping in the channel ...

    Indian Academy of Sciences (India)

    Abstract. In this paper, device performance of graphene nanoribbon field effect transistor (GNRFET) with diffe- rent doping concentrations in different parts of the channel is reported. The study is performed by using atomistic simulations based on self-consistent solution of Schrodinger's and Poisson's equation within the ...

  8. Fabrication and characterization of n-type zinc oxide/p-type boron doped diamond heterojunction

    Czech Academy of Sciences Publication Activity Database

    Marton, M.; Mikolášek, M.; Bruncko, J.; Novotný, I.; Ižák, Tibor; Vojs, M.; Kozak, Halyna; Varga, Marián; Artemenko, Anna; Kromka, Alexander

    2015-01-01

    Roč. 66, č. 5 (2015), s. 277-281 ISSN 1335-3632 R&D Projects: GA ČR(CZ) GBP108/12/G108; GA MŠk(CZ) 7AMB14SK024 Institutional support: RVO:68378271 Keywords : boron doped diamond * zinc oxide * Raman spectroscopy * bipolar heterostructure * wide-bandgap Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.407, year: 2015

  9. n-type doping and passivation of CuInSe2 and CuGaSe2 by hydrogen

    Science.gov (United States)

    Kılıç, Çetin; Zunger, Alex

    2003-08-01

    An impurity in a semiconductor can have either amphoteric behavior (no net production of electron or holes), or be an energetically deep center (carriers produced only at high temperature), or a shallow center (carriers produced even at low temperature). In most semiconductors (e.g., Si, GaAs, GaP, InP, and ZnSe) hydrogen impurities do not produce free carriers, being instead an amphoretic center; yet hydrogen does dope n-type some oxides such as SnO2 and ZnO. We studied theoretically whether or not H could dope chalcopyrite I-III-VI2 compounds, CuInSe2 and CuGaSe2. Based on the first-principles calculations, we find that nonsubstitutionally incorporated hydrogen forms a deep donor in CuGaSe2, but a relatively shallow donor in CuInSe2. The interaction of hydrogen with the abundant defect complex (2VCu+InCu)0 yields an even shallower donor, making CuInSe2 n type. In addition, our results show that hydrogen passivates the acceptorlike copper vacancies in both CuInSe2 and CuGaSe2, thus eliminating p type behavior. These findings, in conjunction with typical conditions under which CuInSe2 and CuGaSe2 are grown, indicate that CuInSe2 could be doped n type via hydrogen incorporation, whereas CuGaSe2 could not. The reason for the different behavior of CuInSe2 and CuGaSe2 towards hydrogen is that in the latter case the conduction-band minimum is at a considerably higher energy than in the former case. Despite this difference in electrical properties, it is predicted that hydrogen can be stored in both CuInSe2 and CuGaSe2 via implantation since the implanted hydrogens decorate copper atoms as well as preexisting copper vacancies.

  10. Phosphorus and carrier density of heavily n-type doped germanium

    Energy Technology Data Exchange (ETDEWEB)

    Takinai, K.; Wada, K. [Department of Materials Engineering, University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-8656 (Japan)

    2016-05-14

    The threshold current density of n-type, tensile-strained Ge lasers strongly depends on the electron density. Although optical net gain analyses indicate that the optimum electron density should be on the order of 1 × 10{sup 20} cm{sup −3} to get the lowest threshold, it is not a simple task to increase the electron density beyond the mid range of 10{sup 19} cm{sup −3}. The present paper analyzes the phenomenon where electron density is not proportional to phosphorus donor density, i.e., “saturation” phenomenon, by applying the so-called amphoteric defect model. The analyses indicate that the saturation phenomenon can be well explained by the charge compensation between the phosphorus donors (P{sup +}) and doubly negative charged Ge vacancies (V{sup 2−}).

  11. Evolution of the Electronic Structure of n-Type BaSnO3 Films With Chemical Doping and Photodoping

    Science.gov (United States)

    Lochocki, Edward; Paik, Hanjong; Uchida, Masaki; Schlom, Darrell; Shen, Kyle

    Lanthanum-doped barium stannate (La:BaSnO3) is a transparent conducting oxide well known for its high mobility and its ability to host a surface electron gas. Here we present angle-resolved photoemission (ARPES) measurements of La:BaSnO3 thin films deposited on scandate substrates by molecular beam epitaxy. Increased bulk La content is found to reduce the surface carrier concentration via Fermi level pinning, in contrast to other n-type transparent conducting oxides. Subsequent ARPES measurements made over the course of hours show that photogenerated electron-hole pairs reduce the upward band bending, providing persistent but reversible surface photodoping. Chemical doping and photodoping both induce spectral changes typically associated with oxygen vacancy formation or electronic correlations, even though BaSnO3 exhibits extreme oxygen stability and its valence and conduction bands have no d character. These results establish BaSnO3 as a unique transparent conductor and demonstrate its potential for understanding the broader class of perovskite oxide materials.

  12. Selfsimilar and fractal analysis of n-type delta-doped quasiregular GaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    García-Cervantes, H.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad Esquina Con Paseo La Bufa S/N, 98060 Zacatecas, Zac. (Mexico)

    2014-05-15

    We study the electronic structure of n-type delta-doped quantum wells in GaAs in which the multiple well system is built according to the Fibonacci sequence. The building blocks A and B correspond to delta-doped wells with impurities densities n{sub 2DA} and n{sub 2DB}, and the same well width. The Thomas-Fermi approximation, the semi-empirical sp{sub 3}s* tight-binding model including spin, the Surface Green Function Matching method and the Transfer Matrix approach were implemented to obtain the confining potential, the electronic structure and the selfsimilarity of the spectrum. The fragmentation of the electronic spectra is observed whenever the building blocks A and B interact and it increases as the difference of impurities density between A and B increases as well. The wave function of the first sate of the fragmented bands presents critical characteristics, this is, it is not a localized state nor a extended one as well as it has selfsimilar features. So, the quasiregular characteristics are preserved irrespective of the complexity of the system and can affect the performance of devices based on these structures.

  13. Electron energy-loss spectroscopy on n-type doped high-temperature superconductors and related systems

    International Nuclear Information System (INIS)

    Alexander, M.

    1992-08-01

    Electron-enery loss spectroscopy measurements on n-type doped high temperature superconductors, their undoped parent compounds, Y-doped Bi 2 Sr 2 CaCu 2 O 8 and some rare earth oxides are presented. The undoped parent compounds Ln 2 CuO 4 (Ln = Pr, Nd, Sm) are charge transfer insulators with a charge transfer energy gap of 1.4 eV. The conduction band lies in the CuO 2 plane and has mainly Cu3d x 2 -y 2 character. O2p x,y states are slightly hybridized with this band. Upon partially substituting the trivalent Ln ions by tetravalent Ce or Th and monovalent F for the O ions, electron doping of the CuO 2 plane occurs with the electrons having mainly Cu3d character. A rigid band behaviour is proposed by several band structure calculations could be ruled out, as well as the occurence of so called 'mid-gap' states appearing inside the band gap between the valence and conduction bands. The position of the Fermi level was found to be at the bottom of the conduction bands. No measurable influence of the reduction process, necessary to obtain superconductivity, was detected in the unoccupied density of states. Characteristics shifts of the measured oxygen and copper edges were correlated with crossing the metal-insulator transition. These shifts are most probably caused by an improved screening capacity of the free charge carriers. A similar effect was also observed in Y-doped Bi 2 Sr 2 CaCu 2 O 8 . Thus, it was possible to show that the disappearance of the valence band hole states upon doping did not occur in a rigid-band-like manner. The low energy excitations in Nd 1.85 Ce 0.15 CuO 4-δ showed a plasmon like excitation at about 1 eV as well as a reduction and an energy shift of the charge transfer excitation. The dispersion of this plasmon excitation was determined. (orig.)

  14. Progress in N-type Si Solar Cell and Module Technology for High Efficiency and Low Cost

    Energy Technology Data Exchange (ETDEWEB)

    Song, Dengyuan; Xiong, Jingfeng; Hu, Zhiyan; Li, Gaofei; Wang, Hongfang; An, Haijiao; Yu, Bo; Grenko, Brian; Borden, Kevin; Sauer, Kenneth; Cui, Jianhua; Wang, Haitao [Yingli Green Energy Holding Co., LTD, 071051 Boading (China); Roessler, T. [Yingli Green Energy Europe GmbH, Heimeranstr. 37, 80339 Munich (Germany); Bultman, J. [ECN Solar Energy, P.O. Box 1, NL-1755 ZG Petten (Netherlands); Vlooswijk, A.H.G.; Venema, P.R. [Tempress Systems BV, Radeweg 31, 8171 Vaassen (Netherlands)

    2012-06-15

    A novel high efficiency solar cell and module technology, named PANDA, using crystalline n-type CZ Si wafers has moved into large-scale production at Yingli. The first commercial sales of the PANDA modules commenced in mid 2010. Up to 600MW of mass production capacity from crystal-Si growth, wafer slicing, cell processing and module assembly have been implemented by the end of 2011. The PANDA technology was developed specifically for high efficiency and low cost. In contrast to the existing n-type Si solar cell manufacturing methods in mass production, this new technology is largely compatible with a traditional p-type Si solar cell production line by conventional diffusion, SiNx coating and screen-printing technology. With optimizing all technologies, Yingli's PANDA solar cells on semi-square 6-inch n-type CZ wafers (cell size 239cm{sup 2}) have been improved to currently have an average efficiency on commercial production lines exceeding 19.0% and up to 20.0% in pilot production. The PANDA modules have been produced and were certified according to UL1703, IEC 61215 and IEC 61730 standards. Nearly two years of full production on scale-up lines show that the PANDA modules have a high efficiency and power density, superior high temperature performance, near zero initial light induced degradation, and excellent efficiency at low irradiance.

  15. Modulation of n-Type Units in Bipolar Host Materials toward High-Performance Phosphorescent OLEDs.

    Science.gov (United States)

    Wang, Fang; Liu, Di; Li, Jiuyan; Ma, Mengyao

    2017-11-01

    9'-Pyridinyl-9'H-9,3':6',9″-tercarbazole (PyCz) is a bipolar host material in phosphorescent organic light-emitting diodes (PhOLEDs). A second n-type unit, either pyridine or diphenylphosphine dioxide (DPPO), is introduced onto the pyridine ring of PyCz at para- or metasite to design and prepare four novel "dual n-type unit bipolar host" materials m-BPyCz, p-BPyCz, m-POPyCz, and p-POPyCz. The incorporation of the second n-type unit pulls down the lowest unoccupied molecular orbitals and facilitates electron injection and transportation, resulting in better charge-balancing ability. As a result, these dual n-type unit bipolar hosts exhibit higher efficiencies and slower efficiency roll-off in their blue and green PhOLEDs. In particular, m-POPyCz containing a bulky DPPO as the second n-type unit with a metalinking possesses the best charge-balancing state and generates a maximum external quantum efficiency (η ext ) of 27.0% (corresponding to a current efficiency of 51.9 cd A -1 and a power efficiency of 46.5 lm W -1 ) in its sky-blue device and still remained at a high η ext of 23.6% even at the practical brightness of 1000 cd m -2 . These results clearly demonstrate that the "dual n-type unit bipolar hosts" with an optimized substitution position and steric effect is a new and effective type of host materials for high-performance OLEDs.

  16. The n-type conduction of indium-doped Cu{sub 2}O thin films fabricated by direct current magnetron co-sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Xing-Min; Su, Xiao-Qiang; Ye, Fan, E-mail: yefan@szu.edu.cn; Wang, Huan; Tian, Xiao-Qing; Zhang, Dong-Ping; Fan, Ping; Luo, Jing-Ting; Zheng, Zhuang-Hao; Liang, Guang-Xing [Institute of Thin Film Physics and Applications, School of Physical Science and Technology and Shenzhen Key Laboratory of Sensor Technology, Shenzhen University, Shenzhen 518060 (China); Roy, V. A. L. [Center of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tong, Hong Kong (China)

    2015-08-24

    Indium-doped Cu{sub 2}O thin films were fabricated on K9 glass substrates by direct current magnetron co-sputtering in an atmosphere of Ar and O{sub 2}. Metallic copper and indium disks were used as the targets. X-ray diffraction showed that the diffraction peaks could only be indexed to simple cubic Cu{sub 2}O, with no other phases detected. Indium atoms exist as In{sup 3+} in Cu{sub 2}O. Ultraviolet-visible spectroscopy showed that the transmittance of the samples was relatively high and that indium doping increased the optical band gaps. The Hall effect measurement showed that the samples were n-type semiconductors at room temperature. The Seebeck effect test showed that the films were n-type semiconductors near or over room temperature (<400 K), changing to p-type at relatively high temperatures. The conduction by the samples in the temperature range of the n-type was due to thermal band conduction and the donor energy level was estimated to be 620.2–713.8 meV below the conduction band. The theoretical calculation showed that indium doping can raise the Fermi energy level of Cu{sub 2}O and, therefore, lead to n-type conduction.

  17. Progress on n-type doping of AlGaN alloys on AlN single crystal substrates for UV optoelectronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Collazo, Ramon; Rice, Anthony; Tweedie, James; Sitar, Zlatko [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC (United States); Mita, Seiji; Xie, Jinqiao; Dalmau, Rafael [HexaTech, Inc., Morrisville, NC (United States)

    2011-07-15

    As the building blocks of deep UV light emitting diode (LED) technology and high-power electronic devices, AlGaN alloys have attracted considerable attention. In this study, AlGaN films with varying compositions doped with Si were deposited on homoepitaxial AlN layers grown on AlN single crystal substrates. The room temperature resistivity of AlGaN alloys of different compositions grown on AlN and sapphire substrates with a constant Si doping level of 6x10{sup 18} cm{sup -3} was compared. AlGaN films grown on AlN substrates consistently exhibited a lower n-type resistivity than those grown on sapphire. An n-type resistivity of 0.1 {omega} cm was obtained for an AlGaN film with 80% Al content and a sheet resistance of 235 {omega}/sq. for an AlGaN film with 70% Al content. The carrier activation energy as a function of Al content in AlGaN for these n-type films was measured. For compositions below 80% Al, the activation energy was around 15 meV due to impurity potential screening. For higher Al compositions, the carrier concentration was limited by a high compensation ratio, except for AlN, which has activation energy of 250 meV. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Application of UV photoluminescence imaging spectroscopy for stacking faults identification on thick, lightly n-type doped, 4°-off 4H-SiC epilayers

    Directory of Open Access Journals (Sweden)

    N. Thierry-Jebali

    2015-03-01

    Full Text Available This paper deals with the description and the application of an original photoluminescence (PL imaging technique on thick, lighly n-type doped 4H-SiC epilayers for in-grown stacking fault (SF identification. This technique, call “photoluminescence imaging spectroscopy” (PLIS, compares different PL imaging pictures in order to create a new picture which displays the location and an approximation of the maximum photoemission wavelength of SFs at room temperature. Five types of SF have been detected and identified by PLIS on two different wafers. The origin of SF type modification during the growth is also discussed in this work.

  19. Doping of SnO2 with H atoms: An alternative way to attain n-type conductivity

    Directory of Open Access Journals (Sweden)

    Luis Villamagua

    2016-11-01

    Full Text Available We propose an explanation for the origin of n-type electrical conductivity in SnO2 based on the results obtained from the DFT+U simulations. Two competitive intrinsic point defects, namely oxygen vacancy and hydrogen impurity, have been considered at different positions within the crystalline lattice in order to find out the equilibrium configurations and to analyze corresponding density of states (DOS patterns along with the electron localization function (ELF. It has been demonstrated that hydrogen could be solely responsible for the n-type conductivity whereas the oxygen vacancy appears to have not a notable influence upon it. The computational analysis is backed up by some experimental data for undoped tin dioxide.

  20. Proposal of a neutron transmutation doping facility for n-type spherical silicon solar cell at high-temperature engineering test reactor.

    Science.gov (United States)

    Ho, Hai Quan; Honda, Yuki; Motoyama, Mizuki; Hamamoto, Shimpei; Ishii, Toshiaki; Ishitsuka, Etsuo

    2018-05-01

    The p-type spherical silicon solar cell is a candidate for future solar energy with low fabrication cost, however, its conversion efficiency is only about 10%. The conversion efficiency of a silicon solar cell can be increased by using n-type silicon semiconductor as a substrate. This study proposed a new method of neutron transmutation doping silicon (NTD-Si) for producing the n-type spherical solar cell, in which the Si-particles are irradiated directly instead of the cylinder Si-ingot as in the conventional NTD-Si. By using a 'screw', an identical resistivity could be achieved for the Si-particles without a complicated procedure as in the NTD with Si-ingot. Also, the reactivity and neutron flux swing could be kept to a minimum because of the continuous irradiation of the Si-particles. A high temperature engineering test reactor (HTTR), which is located in Japan, was used as a reference reactor in this study. Neutronic calculations showed that the HTTR has a capability to produce about 40t/EFPY of 10Ωcm resistivity Si-particles for fabrication of the n-type spherical solar cell. Copyright © 2018 Elsevier Ltd. All rights reserved.

  1. Modulation-Doped In2O3/ZnO Heterojunction Transistors Processed from Solution.

    Science.gov (United States)

    Khim, Dongyoon; Lin, Yen-Hung; Nam, Sungho; Faber, Hendrik; Tetzner, Kornelius; Li, Ruipeng; Zhang, Qiang; Li, Jun; Zhang, Xixiang; Anthopoulos, Thomas D

    2017-05-01

    This paper reports the controlled growth of atomically sharp In 2 O 3 /ZnO and In 2 O 3 /Li-doped ZnO (In 2 O 3 /Li-ZnO) heterojunctions via spin-coating at 200 °C and assesses their application in n-channel thin-film transistors (TFTs). It is shown that addition of Li in ZnO leads to n-type doping and allows for the accurate tuning of its Fermi energy. In the case of In 2 O 3 /ZnO heterojunctions, presence of the n-doped ZnO layer results in an increased amount of electrons being transferred from its conduction band minimum to that of In 2 O 3 over the interface, in a process similar to modulation doping. Electrical characterization reveals the profound impact of the presence of the n-doped ZnO layer on the charge transport properties of the isotype In 2 O 3 /Li-ZnO heterojunctions as well as on the operating characteristics of the resulting TFTs. By judicious optimization of the In 2 O 3 /Li-ZnO interface microstructure, and Li concentration, significant enhancement in both the electron mobility and TFT bias stability is demonstrated. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Modulation-Doped In2O3/ZnO Heterojunction Transistors Processed from Solution

    KAUST Repository

    Khim, Dongyoon

    2017-03-15

    This paper reports the controlled growth of atomically sharp In2 O3 /ZnO and In2 O3 /Li-doped ZnO (In2 O3 /Li-ZnO) heterojunctions via spin-coating at 200 °C and assesses their application in n-channel thin-film transistors (TFTs). It is shown that addition of Li in ZnO leads to n-type doping and allows for the accurate tuning of its Fermi energy. In the case of In2 O3 /ZnO heterojunctions, presence of the n-doped ZnO layer results in an increased amount of electrons being transferred from its conduction band minimum to that of In2 O3 over the interface, in a process similar to modulation doping. Electrical characterization reveals the profound impact of the presence of the n-doped ZnO layer on the charge transport properties of the isotype In2 O3 /Li-ZnO heterojunctions as well as on the operating characteristics of the resulting TFTs. By judicious optimization of the In2 O3 /Li-ZnO interface microstructure, and Li concentration, significant enhancement in both the electron mobility and TFT bias stability is demonstrated.

  3. Solar hydrogen generation by nanoscale p-n junction of p-type molybdenum disulfide/n-type nitrogen-doped reduced graphene oxide.

    Science.gov (United States)

    Meng, Fanke; Li, Jiangtian; Cushing, Scott K; Zhi, Mingjia; Wu, Nianqiang

    2013-07-17

    Molybdenum disulfide (MoS2) is a promising candidate for solar hydrogen generation but it alone has negligible photocatalytic activity. In this work, 5-20 nm sized p-type MoS2 nanoplatelets are deposited on the n-type nitrogen-doped reduced graphene oxide (n-rGO) nanosheets to form multiple nanoscale p-n junctions in each rGO nanosheet. The p-MoS2/n-rGO heterostructure shows significant photocatalytic activity toward the hydrogen evolution reaction (HER) in the wavelength range from the ultraviolet light through the near-infrared light. The photoelectrochemical measurement shows that the p-MoS2/n-rGO junction greatly enhances the charge generation and suppresses the charge recombination, which is responsible for enhancement of solar hydrogen generation. The p-MoS2/n-rGO is an earth-abundant and environmentally benign photocatalyst for solar hydrogen generation.

  4. Influence of doped-charge transport layers on the photovoltaic performance of donor-acceptor blend p-i-n type organic solar cells

    Directory of Open Access Journals (Sweden)

    D. Gebeyehu

    2004-06-01

    Full Text Available This report demonstrates external power conversion efficiencies of 2% under 100 mW/cm2 simulated AM1.5 illumination for organic thin-film photovoltaic cells using a phthalocyanine-fullerene (ZnPc/C60 bulk heterojunction as an active layer, embedded into a p-i-n type architecture with doped wide-gap charge transport layers. For an optically optimized device, we found internal quantum efficiency (IQE of above 80% under short circuit conditions. Such optically thin cells with high internal quantum efficiency are an important step towards high efficiency tandem cells. The p-i-n architecture allows for the design of solar cells with high internal quantum efficiency where only the photoactive region absorbs visible light and recombination losses at contacts are avoided. The I-V characteristics, power conversion efficiencies, the dependence of short circuit current on incident white light intensity, incident photon to collected electron efficiency (IPCE and absorption spectra of the active layer system are discussed.

  5. Parameters affecting light-induced excess conductivity in amorphous silicon doping-modulated multilayers

    International Nuclear Information System (INIS)

    Su, F.C.; Levine, S.; Vanier, P.E.

    1986-01-01

    The phenomenon of light-induced excess conductivity (LEC) which occurs in a-Si:H npnp doping-modulated multilayers is found experimentally to be dependent on several different factors. The concentrations of the dopants in n-type and p-type layers affect the Fermi level position, the height of the barriers, and also the density of defects. These parameters are altered by different choices of inert gas diluent (Ar or He) and substrate temperature T. For a given set of deposition conditions, the LEC effect can be maximized by varying the layer thickness. When T/sub s/ was varied, a minimum in LEC was found near 200-250 0 C. The influence of internal field was examined by using nini, pipi and npnp multilayers. The internal field is a necessary factor to observe a large LEC effect. A compensated film shows a small LEC effect

  6. Effect of 60Co γ-irradiation on the nature of electronic transport in heavily doped n-type GaN based Schottky photodetectors

    Science.gov (United States)

    Chatterjee, Abhishek; Khamari, Shailesh K.; Porwal, S.; Kher, S.; Sharma, T. K.

    2018-04-01

    GaN Schottky photodetectors are fabricated on heavily doped n-type GaN epitaxial layers grown by the hydride vapour phase epitaxy technique. The effect of 60Co γ-radiation on the electronic transport in GaN epilayers and Schottky detectors is studied. In contrast to earlier observations, a steady rise in the carrier concentration with increasing irradiation dose is clearly seen. By considering a two layer model, the contribution of interfacial dislocations in carrier transport is isolated from that of the bulk layer for both the pristine and irradiated samples. The bulk carrier concentration is fitted by using the charge balance equation which indicates that no new electrically active defects are generated by γ-radiation even at 500 kGy dose. The irradiation induced rise in the bulk carrier concentration is attributed to the activation of native Si impurities that are already present in an electrically inert form in the pristine sample. Further, the rise in interfacial contribution in the carrier concentration is governed by the enhanced rate of formation of nitrogen vacancies by irradiation, which leads to a larger diffusion of oxygen impurities. A large value of the characteristic tunnelling energy for both the pristine and irradiated Au/Ni/GaN Schottky devices confirms that the dislocation-assisted tunnelling dominates the low temperature current transport even after irradiation. The advantage of higher displacement energy and larger bandgap of GaN as compared to GaAs is evident from the change in leakage current after irradiation. Further, a fast recovery of the photoresponse of GaN photodetectors after irradiation signifies their compatibility to operate in high radiation zones. The results presented here are found to be crucial in understanding the interaction of 60Co γ-irradiation with n+-GaN epilayers.

  7. Modulation of electrical properties in Cu/n-type InP Schottky junctions using oxygen plasma treatment

    International Nuclear Information System (INIS)

    Kim, Hogyoung; Jung, Chan Yeong; Hyun Kim, Se; Cho, Yunae; Kim, Dong-Wook

    2015-01-01

    Using current–voltage (I–V) measurements, we investigated the effect of oxygen plasma treatment on the temperature-dependent electrical properties of Cu/n-type indium phosphide (InP) Schottky contacts at temperatures in the range 100–300 K. Changes in the electrical parameters were evident below 180 K for the low-plasma-power sample (100 W), which is indicative of the presence of a wider distribution of regions of low barrier height. Modified Richardson plots were used to obtain Richardson constants, which were similar to the theoretical value of 9.4 A cm −2 K −2 for n-type InP. This suggests that, for all the samples, a thermionic emission model including a spatially inhomogeneous Schottky barrier can be used to describe the charge transport phenomena at the metal/semiconductor interface. The voltage dependence of the reverse-bias current revealed that Schottky emission was dominant for the untreated and high-plasma-power (250 W) samples. For the low-plasma-power sample, Poole–Frenkel emission was dominant at low voltages, whereas Schottky emission dominated at higher voltages. Defect states and nonuniformity of the interfacial layer appear to be significant in the reverse-bias charge transport properties of the low-plasma-power sample. (paper)

  8. Asymmetric GaAs n-type double δ-doped quantum wells as a source of intersubband-related nonlinear optical response: Effects of an applied electric field

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez-Magdaleno, K.A.; Martínez-Orozco, J.C.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calz. Solidaridad Esq. Paseo a La Bufa S/N. C.P. 98060 Zacatecas (Mexico); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209 Cuernavaca, Morelos (Mexico); Física Teórica y Aplicada, Escuela de Ingeniería de Antioquia, AA 7516 Medellín (Colombia); Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia); Duque, C.A., E-mail: cduque@fisica.udea.edu.co [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia)

    2014-03-15

    In this work, the conduction band electron states and the associated intersubband-related linear and nonlinear optical absorption coefficient and relative refractive index change are calculated for an asymmetric double n-type δ-doped quantum well in a GaAs-matrix. The effects of an external applied static electric field are included. Values of the two-dimensional impurities density (N{sub 2d}) of each single δ-doped quantum well are taken to vary within the range of 1.0×10{sup 12} to 7.0×10{sup 12} cm{sup −2}, consistent with the experimental data growth regime. The optical responses are reported as a function of the δ-doped impurities density and the applied electric field. It is shown that single electron states and the related optical quantities are significantly affected by the structural asymmetry of the double δ-doped quantum well system. In addition, a brief comparison with the free-carrier-related optical response is presented. -- Highlights: • Nonlinear optics in asymmetric double n-type δ-doped quantum well in a GaAs-matrix. • The system is considered under external applied electric field in growth direction. • The 2D impurity density is consistent with the experimental data growth regime. • The optical quantities are significantly affected by the structural asymmetry of the system.

  9. Asymmetric GaAs n-type double δ-doped quantum wells as a source of intersubband-related nonlinear optical response: Effects of an applied electric field

    International Nuclear Information System (INIS)

    Rodríguez-Magdaleno, K.A.; Martínez-Orozco, J.C.; Rodríguez-Vargas, I.; Mora-Ramos, M.E.; Duque, C.A.

    2014-01-01

    In this work, the conduction band electron states and the associated intersubband-related linear and nonlinear optical absorption coefficient and relative refractive index change are calculated for an asymmetric double n-type δ-doped quantum well in a GaAs-matrix. The effects of an external applied static electric field are included. Values of the two-dimensional impurities density (N 2d ) of each single δ-doped quantum well are taken to vary within the range of 1.0×10 12 to 7.0×10 12 cm −2 , consistent with the experimental data growth regime. The optical responses are reported as a function of the δ-doped impurities density and the applied electric field. It is shown that single electron states and the related optical quantities are significantly affected by the structural asymmetry of the double δ-doped quantum well system. In addition, a brief comparison with the free-carrier-related optical response is presented. -- Highlights: • Nonlinear optics in asymmetric double n-type δ-doped quantum well in a GaAs-matrix. • The system is considered under external applied electric field in growth direction. • The 2D impurity density is consistent with the experimental data growth regime. • The optical quantities are significantly affected by the structural asymmetry of the system

  10. Differential Modulation of N-Type Calcium Channels by mu-Opioid Receptors in Oxytocinergic Versus Vasopressinergic Neurohypophysial Terminals

    Czech Academy of Sciences Publication Activity Database

    Ortiz-Miranda, S. I.; Dayanithi, Govindan; Velazquez-Marrero, C.; Custer, E. E.; Treistman, S. N.; Lemos, J. R.

    2010-01-01

    Roč. 225, č. 1 (2010), s. 276-288 ISSN 0021-9541 Institutional research plan: CEZ:AV0Z50390703 Keywords : magnocellular neurons * G-protein modulation * neurohypophysis Subject RIV: FH - Neurology Impact factor: 3.986, year: 2010

  11. Fragile X mental retardation protein controls synaptic vesicle exocytosis by modulating N-type calcium channel density

    Science.gov (United States)

    Ferron, Laurent; Nieto-Rostro, Manuela; Cassidy, John S.; Dolphin, Annette C.

    2014-04-01

    Fragile X syndrome (FXS), the most common heritable form of mental retardation, is characterized by synaptic dysfunction. Synaptic transmission depends critically on presynaptic calcium entry via voltage-gated calcium (CaV) channels. Here we show that the functional expression of neuronal N-type CaV channels (CaV2.2) is regulated by fragile X mental retardation protein (FMRP). We find that FMRP knockdown in dorsal root ganglion neurons increases CaV channel density in somata and in presynaptic terminals. We then show that FMRP controls CaV2.2 surface expression by targeting the channels to the proteasome for degradation. The interaction between FMRP and CaV2.2 occurs between the carboxy-terminal domain of FMRP and domains of CaV2.2 known to interact with the neurotransmitter release machinery. Finally, we show that FMRP controls synaptic exocytosis via CaV2.2 channels. Our data indicate that FMRP is a potent regulator of presynaptic activity, and its loss is likely to contribute to synaptic dysfunction in FXS.

  12. Thermoelectric properties of I-doped n-type Bi2Te3-based material prepared by hydrothermal and subsequent hot pressing

    Directory of Open Access Journals (Sweden)

    Fang Wu

    2017-04-01

    Full Text Available I-doped Bi2Te3−xIx (x=0, 0.05, 0.1, 0.2 flower-like nanoparticles were synthesized by a hydrothermal method through a careful adjustment of the amount of ethylenediamine tetraacetic acid surfactant. The nanopowders of flower-like nanoparticles were hot-pressed into bulk pellets and the thermoelectric properties of the pellets were investigated. The results showed that I-doping decreased the electrical resistivity effectively, and the thermal conductivitives of the Bi2Te3−xIx bulk samples was lower because of the closer atomic mass of I compared to Te. As a result, a ZT value of 1.1 was attained at 448 K for the Bi2Te2.9I0.1 sample.

  13. Design rules for modulation doped AlAs quantum wells

    Science.gov (United States)

    Chung, Yoon Jang; Baldwin, K. W.; West, K. W.; Kamburov, D.; Shayegan, M.; Pfeiffer, L. N.

    AlxGa1-xAs/AlAs/AlxGa1-xAs quantum wells were grown with various barrier compositions ranging from x =0.26 to x =0.8. We investigate the modulation doping characteristics of the samples by magneto-transport measurements. The carrier concentration in the well peaks near the barrier alloy fraction of x =0.26 in the dark and near x =0.38 after illumination with a red LED. This behavior is consistent with the results in a separate study for AlxGa1-xAs/GaAs/AlxGa1-xAs quantum wells in the range of x =0.26 to x =1.0. We show from a charge transfer model that the calculated energy difference between the conduction band offset at the well interface and the donor energy level, ΔEC-ED, coincides for the two types of wells. This implies that, despite the differing positions of the conduction band minimum for the GaAs and AlAs wells, the doping of either well is governed by the electronic properties of the barrier. Based on this knowledge we designed high quality AlAs quantum wells with low (1 x 1011 cm-2) and high (3 x 1011 cm-2) density, and the magneto-transport data show clear signals of the fractional quantum Hall effect (2/3, 3/5, 4/7 for low density and 5/3, 8/5 for high density). Work supported by the NSF (Grants DMR-1305691, ECCS-1508925, and MRSEC DMR-1420541), the DOE Basic Energy Sciences (Grant DE-FG02-00-ER45841), the Gordon and Betty Moore Foundation (Grant GBMF4420), and the Keck Foundation.

  14. New Insight on Tuning Electrical Transport Properties via Chalcogen Doping in n-type Mg3Sb2-Based Thermoelectric Materials

    DEFF Research Database (Denmark)

    Zhang, Jiawei; Song, Lirong; Borup, Kasper

    2018-01-01

    of different chalcogen dopants Q (Q = S, Se, and Te) on thermoelectric properties, it is found that the chalcogen dopants Q become more efficient with decreasing electronegativity difference between Q and Mg, which is mainly due to the increasing carrier concentration and mobility. Using density functional...... theory calculations, it is shown that the improving carrier concentration originates from the increasing doping limit induced by the stabilizing extrinsic defect. Moreover, the increasing electron mobility with decreasing electronegativity difference between Q and Mg is attributed to the smaller...

  15. Strong far-infrared intersubband absorption under normal incidence in heavily n-type doped nonalloy GaSb-AlSb superlattices

    Science.gov (United States)

    Samoska, L. A.; Brar, Berinder; Kroemer, H.

    1993-01-01

    We report on long-wavelength intersubband absorption under normal incidence in heavily doped binary-binary GaSb-AlSb superlattices. Due to a small energy difference between the ellipsoidal L valleys in GaSb and the low-density-of-states Gamma minimum, electrons spill over from the first Gamma subband into the higher-energy L subband in GaSb wells, where they are allowed to make an intersubband transition under normally incident radiation. A peak fractional absorption per quantum well of 6.8 x 10 exp 3 (absorption coefficient alpha of about 8500/cm) is observed at about 15 microns wavelength for a sheet concentration of 1.6 x 10 exp 12 sq cm/well.

  16. In-plane magneto-photoluminescence studies of modulation-doped GaAs/AlGaAs coupled double quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    KIM,YONGMIN; PERRY,C.H.; SIMMONS,JERRY A.; KLEM,JOHN F.

    2000-05-11

    In-plane magnetic field photoluminescence spectra from n series of n-type modulation doped GaAs/Al{sub 0.3}Ga{sub 0.7}As coupled double quantum wells show distinctive doublet structures related to the tunnel-split ground sub-level states. The magnetic field behavior of the upper transition from the antisymmetric state strongly depends on sample mobility. In a lower mobility sample, the transition energy displays an N-type kink with field (namely a maximum followed by a minimum), whereas higher mobility samples have a linear dependence. The former is attributed to a coupling mechanism due to homogeneous broadening of the electron and hole states. The results are in good agreement with recent theoretical calculations.

  17. New superjuction LDMOS with surface and bulk electric field modulation by buffered step doping and multi floating buried layers

    Science.gov (United States)

    Cao, Zhen; Duan, Baoxing; Yuan, Song; Shi, Tongtong; Yang, Yintang

    2017-11-01

    A new superjunction lateral double diffused MOSFET with surface and bulk electric field modulation (SBEFM SJ-LDMOS) by applying of multiple floating buried layers and buffered step doping is proposed in this paper. The Multiple N-type floating buried layers are embedded in P-substrate, to reduce the amount of field crowding at N+/N-buffer/P-substrate junction by spreading the vertical depletion layer, which effectively improves the bulk electric field distribution in SJ-LDMOS, and the N+/N-buffer/P-substrate junction and the auxiliary MFB layers/substrate junctions jointly sustain a high vertical breakdown voltage (BV). In addition, based on the buffered step doping layer under the SJ layer, a uniform lateral electric field at the drift region surface of the device is obtained. Therefore, the bulk and surface electric field are both optimized simultaneously in SBEFM SJ-LDMOS. Simulated results show that compared with the conventional Buffered SJ-LDMOS and BSD SJ-LDMOS, the proposed SBEFM SJ-LDMOS improves BV by 131.7% and 80.4%, respectively, at the same drift region length and with low specific ON-resistance (RON,sp). SBEFM SJ-LDMOS exhibits excellent performance with the power figure-of-merit (FOM=BV2/RON,sp) of 13.07 MW/cm2.

  18. Improved organic p-i-n type solar cells with n-doped fluorinated hexaazatrinaphthylene derivatives HATNA-F{sub 6} and HATNA-F{sub 12} as transparent electron transport material

    Energy Technology Data Exchange (ETDEWEB)

    Selzer, Franz, E-mail: franz.selzer@iapp.de; Falkenberg, Christiane, E-mail: Christiane.Falkenberg@heliatek.com; Leo, Karl, E-mail: karl.leo@iapp.de; Riede, Moritz, E-mail: moritz.riede@physics.ox.ac.uk [Institut für Angewandte Photophysik (IAPP), Technische Universität Dresden, D-01062 Dresden (Germany); Hamburger, Manuel, E-mail: M.Hamburger@oci.uni-heidelberg.de; Baumgarten, Martin, E-mail: baumgart@mpip-mainz.mpg.de; Müllen, Klaus, E-mail: muellen@mpip-mainz.mpg.de [Max Planck Institute for Polymer Research (MPIP), D-55128 Mainz (Germany)

    2014-02-07

    We study new electron transport materials (ETM) to replace the reference material C{sub 60} in p-i-n type organic solar cells. A comprehensive material characterization is performed on two fluorinated hexaazatrinaphthylene derivatives, HATNA-F{sub 6} and HATNA-F{sub 12}, to identify the most promising material for the application in devices. We find that both HATNA derivatives are equally able to substitute C{sub 60} as ETM as they exhibit large optical energy gaps, low surface roughness, and sufficiently high electron mobilities. Furthermore, large electron conductivities of 3.5×10{sup −5} S/cm and 2.0×10{sup −4} S/cm are achieved by n-doping with 4 wt. % W{sub 2}(hpp){sub 4}. HOMO levels of (7.72 ± 0.05) eV and (7.73 ± 0.05) eV are measured by ultraviolet photoelectron spectroscopy and subsequently used for estimating LUMO values of (4.2 ± 0.8) eV and (4.3 ± 0.8) eV. Both fluorinated HATNA derivatives are successfully applied in p-i-n type solar cells. Compared to identical reference devices comprising the standard material C{sub 60}, the power conversion efficiency (PCE) can be increased from 2.1 % to 2.4 % by using the new fluorinated HATNA derivatives.

  19. Thermoelectric properties and chemical potential tuning by Cu-doping in n-type ionic conductors CuxAg2-xSe0.5Te0.5

    Science.gov (United States)

    Lee, Min Ho; Yun, Jae Hyun; Ahn, Kyunghan; Rhyee, Jong-Soo

    2017-12-01

    Copper and silver chalcogenides with superionic conduction behavior have shown impressively high ZT values, but there has been no intensive effort to optimize their carrier density to further improve their ZT values. Here, we prepared polycrystalline CuxAg2-xSe0.5Te0.5 (x = 0.01, 0.05, 0.1) samples using high temperature melting followed by hot-press sintering, and characterized their thermoelectric properties. We demonstrated that Cu substitution for Ag was achieved with electrical conductivity with increasing Cu content was greater than the decrease in absolute value of the Seebeck coefficient in the superionic conduction state. This led to relatively high power factors for Cu0.1Ag1.99Se0.5Te0.5, ranging between 1.10 and 1.30 mW m-1 K-2 over the broad temperature range of 400-560 K, and resulted in the highest ZT of 0.85 at 560 K. Furthermore, ZT values approached >0.7 over a wide temperature range of 460-560 K for x > 0.05. We suggest that the unusual Cu doping effect in Ag2Se0.5Te0.5 can be attributed to the creation of Cu ion conduction in addition to Ag ion conduction, and the optimization of the compound's n-type carrier density.

  20. Tunable graphene doping by modulating the nanopore geometry on a SiO2/Si substrate

    KAUST Repository

    Lim, Namsoo

    2018-02-28

    A tunable graphene doping method utilizing a SiO2/Si substrate with nanopores (NP) was introduced. Laser interference lithography (LIL) using a He–Cd laser (λ = 325 nm) was used to prepare pore size- and pitch-controllable NP SiO2/Si substrates. Then, bottom-contact graphene field effect transistors (G-FETs) were fabricated on the NP SiO2/Si substrate to measure the transfer curves. The graphene transferred onto the NP SiO2/Si substrate showed relatively n-doped behavior compared to the graphene transferred onto a flat SiO2/Si substrate, as evidenced by the blue-shift of the 2D peak position (∼2700 cm−1) in the Raman spectra due to contact doping. As the porosity increased within the substrate, the Dirac voltage shifted to a more positive or negative value, depending on the initial doping type (p- or n-type, respectively) of the contact doping. The Dirac voltage shifts with porosity were ascribed mainly to the compensation for the reduced capacitance owing to the SiO2–air hetero-structured dielectric layer within the periodically aligned nanopores capped by the suspended graphene (electrostatic doping). The hysteresis (Dirac voltage difference during the forward and backward scans) was reduced when utilizing an NP SiO2/Si substrate with smaller pores and/or a low porosity because fewer H2O or O2 molecules could be trapped inside the smaller pores.

  1. Modulation Doping of Silicon using Aluminium-induced Acceptor States in Silicon Dioxide

    Science.gov (United States)

    König, Dirk; Hiller, Daniel; Gutsch, Sebastian; Zacharias, Margit; Smith, Sean

    2017-01-01

    All electronic, optoelectronic or photovoltaic applications of silicon depend on controlling majority charge carriers via doping with impurity atoms. Nanoscale silicon is omnipresent in fundamental research (quantum dots, nanowires) but also approached in future technology nodes of the microelectronics industry. In general, silicon nanovolumes, irrespective of their intended purpose, suffer from effects that impede conventional doping due to fundamental physical principles such as out-diffusion, statistics of small numbers, quantum- or dielectric confinement. In analogy to the concept of modulation doping, originally invented for III-V semiconductors, we demonstrate a heterostructure modulation doping method for silicon. Our approach utilizes a specific acceptor state of aluminium atoms in silicon dioxide to generate holes as majority carriers in adjacent silicon. By relocating the dopants from silicon to silicon dioxide, Si nanoscale doping problems are circumvented. In addition, the concept of aluminium-induced acceptor states for passivating hole selective tunnelling contacts as required for high-efficiency photovoltaics is presented and corroborated by first carrier lifetime and tunnelling current measurements. PMID:28425460

  2. Intensity-dependent nonlinear optical properties in a modulation-doped single quantum well

    International Nuclear Information System (INIS)

    Ungan, F.

    2011-01-01

    In the present work, the changes in the intersubband optical absorption coefficients and the refractive index in a modulation-doped quantum well have been investigated theoretically. Within the envelope function approach and the effective mass approximation, the electronic structure of the quantum well is calculated from the self-consistent numerical solution of the coupled Schroedinger-Poisson equations. The analytical expressions of optical properties are obtained by using the compact density-matrix approach. The numerical results GaAs/Al x Ga 1-x As are presented for typical modulation-doped quantum well system. The linear, third-order nonlinear and total absorption and refractive index changes depending on the doping concentration are investigated as a function of the incident optical intensity and structure parameters, such as quantum well width and stoichiometric ratio. The results show that the doping concentration, the structure parameters and the incident optical intensity have a great effect on the optical characteristics of these structures. - Highlights: → The doping concentration has a great effect on the optical characteristics of these structures. → The structure parameters have a great effect on the optical properties of these structures. → The total absorption coefficients reduced as the incident optical intensity increases. → The RICs reduced as the incident optical intensity increases.

  3. Modulation Doping of Silicon using Aluminium-induced Acceptor States in Silicon Dioxide

    Science.gov (United States)

    König, Dirk; Hiller, Daniel; Gutsch, Sebastian; Zacharias, Margit; Smith, Sean

    2017-04-01

    All electronic, optoelectronic or photovoltaic applications of silicon depend on controlling majority charge carriers via doping with impurity atoms. Nanoscale silicon is omnipresent in fundamental research (quantum dots, nanowires) but also approached in future technology nodes of the microelectronics industry. In general, silicon nanovolumes, irrespective of their intended purpose, suffer from effects that impede conventional doping due to fundamental physical principles such as out-diffusion, statistics of small numbers, quantum- or dielectric confinement. In analogy to the concept of modulation doping, originally invented for III-V semiconductors, we demonstrate a heterostructure modulation doping method for silicon. Our approach utilizes a specific acceptor state of aluminium atoms in silicon dioxide to generate holes as majority carriers in adjacent silicon. By relocating the dopants from silicon to silicon dioxide, Si nanoscale doping problems are circumvented. In addition, the concept of aluminium-induced acceptor states for passivating hole selective tunnelling contacts as required for high-efficiency photovoltaics is presented and corroborated by first carrier lifetime and tunnelling current measurements.

  4. Pump-induced refractive index modulation and dispersions in Er3+-doped fibers

    DEFF Research Database (Denmark)

    Thirstrup, Carsten; Shi, Yuan

    1996-01-01

    to experimental results apart from a wavelength independent offset. The offset is interpreted to originate from high energetic optical transitions. The results show that for a large refractive index modulation, a short and highly doped fiber should be used with limited amplified spontaneous emission effect....... The analysis contains measurements of pump induced refractive index changes as function of wavelength, pump power, and doping concentration. A model taking account of the contribution to the refractive index changes from optical transitions between 4 I15/2 states and 4I13/2 states in Er3+ yields good agreement...

  5. Correlation between modulation structure and electronic inhomogeneity on Pb-doped Bi-2212 single crystals

    International Nuclear Information System (INIS)

    Sugimoto, A.; Kashiwaya, S.; Eisaki, H.; Yamaguchi, H.; Oka, K.; Kashiwaya, H.; Tsuchiura, H.; Tanaka, Y.

    2005-01-01

    The correlation between nanometer-size electronic states and surface structure is investigated by scanning tunneling microscopy/spectroscopy (STM/S) on Pb-doped Bi 2-x Pb x Sr 2 CaCu2O 8+y (Pb-Bi-2212) single crystals. The advantage of the Pb-Bi-2212 samples is that the modulation structure can be totally or locally suppressed depending on the Pb contents and annealing conditions. The superconducting gap (Δ) distribution on modulated Pb-Bi-2212 samples showed the lack of correlation with modulation structure except a slight reduction of superconducting island size for the b-axis direction. On the other hand, the optimal doped Pb-Bi-2212 (x = 0.6) samples obtained by reduced-annealing showed totally non-modulated structure in topography, however, the spatial distribution of Δ still showed inhomogeneity of which features were quite similar to those of modulated samples. These results suggest that the modulation structure is not the dominant origin of inhomogeneity although it modifies the streaky Δ structure sub-dominantly. From the gap structure variation around the border of narrow gap and broad gap regions, a trend of the coexistence of two separated phases i.e., superconducting phase and pseudogap like phase, is detected

  6. Large Modulation of Charge Carrier Mobility in Doped Nanoporous Organic Transistors

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Fengjiao [Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, 600 S. Mathews Ave. Urbana IL 61801 USA; Dai, Xiaojuan [Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 P. R. China; Zhu, Weikun [Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, 600 S. Mathews Ave. Urbana IL 61801 USA; Chung, Hyunjoong [Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, 600 S. Mathews Ave. Urbana IL 61801 USA; Diao, Ying [Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, 600 S. Mathews Ave. Urbana IL 61801 USA

    2017-05-10

    Molecular doping of organic electronics has shown promise to sensitively modulate important device metrics. One critical challenge is the disruption of structure order upon doping of highly crystalline organic semiconductors, which significantly reduces the charge carrier mobility. This paper demonstrates a new method to achieve large modulation of charge carrier mobility via channel doping without disrupting the molecular ordering. Central to the method is the introduction of nanopores into the organic semiconductor thin films via a simple and robust templated meniscus-guided coating method. Using this method, the charge carrier mobility of C8-benzothieno[3,2-b]benzothiophene transistors is boosted by almost sevenfold. This paper further demonstrates enhanced electron transport by close to an order of magnitude in a diketopyrrolopyrrole-based donor–acceptor polymer. Combining spectroscopic measurements, density functional theory calculations, and electrical characterizations, the doping mechanism is identified as partial-charge-transfer induced trap filling. The nanopores serve to enhance the dopant/organic semiconductor charge transfer reaction by exposing the π-electrons to the pore wall.

  7. Impurity modulated excitation profile of doped quantum dot subject to oscillatory magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Datta, Nirmal Kumar [Department of Physics, Suri Vidyasagar College, Suri, Birbhum 731101, West Bengal (India); Ghosh, Manas, E-mail: pcmg77@rediffmail.com [Department of Chemistry, Physical Chemistry Section, Visva Bharati University, Santiniketan, Birbhum 731 235, West Bengal (India)

    2011-04-15

    Research highlights: {yields} The excitation profile of quantum dot subject to periodically fluctuating magnetic field has been investigated. {yields} The quantum dot is doped with a repulsive Gaussian impurity. {yields} The impurity domain and impurity location delicately modulate the excitation profile. {yields} The ratio of cyclotron frequency and harmonic confinement potential has important impact on excitation rate. {yields} The findings could have important engineering applications. - Abstract: We explore the excitation profile of a repulsive impurity doped quantum dot under periodically fluctuating magnetic field. We have considered Gaussian impurity centers. The investigation reveals the roles subtly played by the dopant coordinate and the region of influence of the dopant to modulate the excitation pattern. The rate of transition to the excited states has been invoked to analyze the interplay between the above two impurity parameters in influencing the excitation process. The ratio of cyclotron frequency and harmonic confinement potential has important impact on excitation rate.

  8. Experimental Performance of a Single-Mode Ytterbium-doped Fiber Ring Laser with Intracavity Modulator

    Science.gov (United States)

    Numata, Kenji; Camp, Jordan

    2012-01-01

    We have developed a linearly polarized Ytterbium-doped fiber ring laser with a single longitudinal mode output at 1064 run. A fiber-coupled intracavity phase modulator ensured mode-hop free operation and allowed fast frequency tuning. The fiber laser was locked with high stability to an iodine-stabilized laser, showing a frequency noise suppression of a factor approx 10 (exp 5) at 1 mHz

  9. A simple and controlled single electron transistor based on doping modulation in silicon nanowires

    OpenAIRE

    Hofheinz, M.; Jehl, X.; Sanquer, M.; Molas, G.; Vinet, M.; Deleonibus, S.

    2006-01-01

    A simple and highly reproducible single electron transistor (SET) has been fabricated using gated silicon nanowires. The structure is a metal-oxide-semiconductor field-effect transistor made on silicon-on-insulator thin films. The channel of the transistor is the Coulomb island at low temperature. Two silicon nitride spacers deposited on each side of the gate create a modulation of doping along the nanowire that creates tunnel barriers. Such barriers are fixed and controlled, like in metallic...

  10. Design rules for modulation-doped AlAs quantum wells

    Science.gov (United States)

    Chung, Yoon Jang; Baldwin, K. W.; West, K. W.; Kamburov, D.; Shayegan, M.; Pfeiffer, L. N.

    2017-07-01

    Owing to their multivalley, anisotropic, energy band structure, two-dimensional electron systems (2DESs) in modulation-doped AlAs quantum wells (QWs) provide a unique platform to investigate electron interaction physics and ballistic transport. Indeed, a plethora of phenomena unseen in other 2DESs have been observed over the past decade. However, a foundation for sample design is still lacking for AlAs 2DESs, limiting the means to achieve optimal quality samples. Here, we present a systematic study on the fabrication of modulation-doped AlAs and GaAs QWs over a wide range of AlxGa1 -xAs barrier alloy compositions. Our data indicate clear similarities in modulation doping mechanisms for AlAs and GaAs, and provide guidelines for the fabrication of very high quality AlAs 2DESs. We highlight the unprecedented quality of the fabricated AlAs samples by presenting the magnetotransport data for low-density (≃1 ×1011cm-2 ) AlAs 2DESs that exhibit high-order fractional quantum Hall signatures.

  11. Electrical and optical properties of modulation-doped p-AlGaN/GaN superlattices

    Science.gov (United States)

    Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Osinsky, A. V.; Norris, P. E.; Pearton, S. J.; Van Hove, J.; Wowchak, A.; Chow, P.

    2001-12-01

    Electrical and optical properties of modulation-doped p-AlGaN/GaN superlattices are compared to those of similarly doped p-GaN films. It is shown that modulation doping increases the sheet hole concentration by several times. In p-AlGaN/GaN superlattices grown on GaN underlayers, this increase is accompanied by a significant increase in hole mobility which results in a remarkable decrease in sheet resistivity of the structure compared to p-GaN films and this decrease in sheet resistivity should hold up to temperatures exceeding 350 °C. For superlattices prepared on AlGaN underlayers, the mobility decreases compared to p-GaN. In such superlattices, one also observes a strong redshift and a strong broadening of the band edge luminescence peak coming most probably from increased mosaicity and strain which would also explain the observed deterioration of mobility. The magnitude of the redshift in the position of the band edge luminescence band slightly increased upon application of reverse bias which is interpreted as a manifestation of quantum-confined Stark effect.

  12. All-optical modulation in dye-doped nematic liquid crystal photonic bandgap fibers

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Lægsgaard, Jesper; Bjarklev, Anders Overgaard

    2004-01-01

    Photonic crystal fibers (PCFs) have attracted significant attention during the last years and much research has been devoted to develop fiber designs for various applications, hereunder tunable fiber devices. Recently, thermally and electrically tunable PCF devices based on liquid crystals (LCs......) have been demonstrated. However, optical tuning of the LC PCF has until now not been demonstrated. Here we demonstrate an all-optical modulator, which utilizes a pulsed 532nm laser to modulate the spectral position of the bandgaps in a photonic crystal fiber infiltrated with a dye-doped nematic liquid...... crystal. We demonstrate a modulation frequency of 2kHz for a moderate pump power of 2-3mW and describe two pump pulse regimes in which there is an order of magnitude difference between the decay times....

  13. Dielectric Spectroscopy of Metal Nanoparticle Doped Liquid Crystal Displays ExhibitingFrequency Modulation Response

    Science.gov (United States)

    Kobayashi, Shunsuke; Miyama, Tomohiro; Nishida, Naoto; Sakai, Yoshio; Shiraki, Hiroyuki; Shiraishi, Yukihide; Toshima, Naoki

    2006-06-01

    Twisted nematic liquid crystal displays (TN-LCDs), doped with the nanoparticles of metal, such as Pd, Ag, or Ag-Pd, which are protected with ligand molecules, such as nematic liquid crystal, exhibit a frequency modulation (FM) electro-optical (EO) response with short response time of milliseconds (ms) or sub-ms order together with the ordinary rms voltage response. These devices are called FM/AM-TN-LCDs; they are distinct from the ordinary LCDs featured by the amplitude modulation (AM) response. The phenomena of the FM/AM LCDs may be attributed to the dielectric dispersion of a heterogeneous dielectric medium known as the Maxwell-Wagner effect. It is experimentally shown that the frequency range spreads from several tens hertz to several tens kilohertz and the spectrum is more or less centered about the dielectric relaxation frequency. We formulated a theory based on an equivalent circuit model to evaluate the dielectric relaxation frequency and the dielectric strengths; and we succeeded in explaining the dependence of the dielectric relaxation frequency on the concentration of nanoparticles and the their dielectric and electrical properties, whereas conventional theories based on electromagnetic theory are unable to explain this concentration dependence. This paper reports on the experimental results of the EO effects and the dielectric spectroscopy including the dielectric relaxation times and the dielectric strengths of nematic liquid crystal, 5CB (4-pentyl-4'-cyanobiphenyl), doped with the metal nanoparticles of Pd alone and Ag-Pd composite; and discusses how the observed dielectric relaxation frequency or dielectric relaxation time depend on the concentration of the doped nanoparticles and also their electrical and dielectric properties.

  14. Modulation doping at BaSnO3LaInO3

    Science.gov (United States)

    Char, Kookrin; Shin, Juyeon; Kim, Young Mo; Kim, Youjung

    We recently reported on the conductance enhancement at the interface between two band insulators: LaInO3 (LIO) and BaSnO3 (BSO). These two-dimensional electron gas-like (2DEG) states at the LIO/Ba1-xLaxSnO3 (BLSO) polar interface display the stability, the controllability of the local carrier concentration, and the high electron mobility of BLSO. Search for the origin of enhanced conductance at the interface has been carried out, and one of the findings is that the doping level of BSO is a critical parameter for the polar charge contribution . We have also investigated a new modulated heterostructure by inserting an undoped BSO spacer layer at the LIO/BLSO interface. As increasing the thickness of the spacer layer, the carrier concentration and the mobility continually decreased. We attribute the results to the modified band bending as the thickness of the spacer layer varies and to the dislocation-limited transport. However, when we controlled the band bending by field effect, improved mobility was observed in these modulated heterostructures. This new modulated heterostructures of the LIO/BSO polar interface look promising not only for higher electron mobility devices but also for elucidating the mechanism of the 2DEG-like behavior. Samsung science and technology foundation.

  15. Gibbs–Thomson Effect in Planar Nanowires: Orientation and Doping Modulated Growth

    KAUST Repository

    Shen, Youde

    2016-06-02

    Epitaxy-enabled bottom-up synthesis of self-assembled planar nanowires via the vapor-liquid-solid mechanism is an emerging and promising approach toward large-scale direct integration of nanowire-based devices without postgrowth alignment. Here, by examining large assemblies of indium tin oxide nanowires on yttria-stabilized zirconia substrate, we demonstrate for the first time that the growth dynamics of planar nanowires follows a modified version of the Gibbs-Thomson mechanism, which has been known for the past decades to govern the correlations between thermodynamic supersaturation, growth speed, and nanowire morphology. Furthermore, the substrate orientation strongly influences the growth characteristics of epitaxial planar nanowires as opposed to impact at only the initial nucleation stage in the growth of vertical nanowires. The rich nanowire morphology can be described by a surface-energy-dependent growth model within the Gibbs-Thomson framework, which is further modulated by the tin doping concentration. Our experiments also reveal that the cutoff nanowire diameter depends on the substrate orientation and decreases with increasing tin doping concentration. These results enable a deeper understanding and control over the growth of planar nanowires, and the insights will help advance the fabrication of self-assembled nanowire devices. © 2016 American Chemical Society.

  16. Finite-temperature effects on conductance modulation by local doping in graphene with multiple magnetic barriers

    Science.gov (United States)

    Myoung, Nojoon; Lidorikis, Elefterios

    2015-12-01

    The electronic and transport properties of graphene modulated by magnetic barrier arrays are derived at finite temperatures. Prominent conductance gaps, originating from quantum interference effects are found in the periodic array case. When a structural defect is inserted in the array, sharp defect modes of high conductance appear within the conductance gaps. These modes are shifted by local doping in the defect region, resulting in large contrast in the ballistic conductance of graphene sheet. In general it is found that sensitivity is strongly dependent on temperature due to smoothing out of the defect-induced peaks and transport gaps. This temperature dependence, however, offers the added capability for sub-mK temperature sensing resolution, and thus an opportunity towards ultra-sensitive combined electrochemical-calorimetric sensing.

  17. Simple and controlled single electron transistor based on doping modulation in silicon nanowires

    Science.gov (United States)

    Hofheinz, M.; Jehl, X.; Sanquer, M.; Molas, G.; Vinet, M.; Deleonibus, S.

    2006-10-01

    A simple and highly reproducible single electron transistor (SET) has been fabricated using gated silicon nanowires. The structure is a metal-oxide-semiconductor field-effect transistor made on silicon-on-insulator thin films. The channel of the transistor is the Coulomb island at low temperature. Two silicon nitride spacers deposited on each side of the gate create a modulation of doping along the nanowire that creates tunnel barriers. Such barriers are fixed and controlled, like in metallic SETs. The period of the Coulomb oscillations is set by the gate capacitance of the transistor and therefore controlled by lithography. The source and drain capacitances have also been characterized. This design could be used to build more complex SET devices.

  18. Impact of compound doping on hole and electron balance in p-i-n organic light-emitting diodes

    Directory of Open Access Journals (Sweden)

    Xin-Xin Wang

    2013-10-01

    Full Text Available The fluorescent and phosphorescent p-i-n organic light-emitting diodes (OLEDs with well controllable compound doping have been systematically investigated, where MoO3 and LiF are the effective p-type and n-type dopants, respectively. For both the bulk and interfacial doping, the hole and electron balance in the devices is found to be strongly dependent on the doping configuration, which could either facilitate or compromise the device power efficiency. The impact of the compound doping on the charge balance is further confirmed by the change of the emission region with different doping configuration. The modulation of p-type and n-type doping densities and position is thus essential for optimizing hole and electron balance in p-i-n OLEDs.

  19. Intrinsically High Thermoelectric Performance in AgInSe2 n-Type Diamond-Like Compounds.

    Science.gov (United States)

    Qiu, Pengfei; Qin, Yuting; Zhang, Qihao; Li, Ruoxi; Yang, Jiong; Song, Qingfeng; Tang, Yunshan; Bai, Shengqiang; Shi, Xun; Chen, Lidong

    2018-03-01

    Diamond-like compounds are a promising class of thermoelectric materials, very suitable for real applications. However, almost all high-performance diamond-like thermoelectric materials are p-type semiconductors. The lack of high-performance n-type diamond-like thermoelectric materials greatly restricts the fabrication of diamond-like material-based modules and their real applications. In this work, it is revealed that n-type AgInSe 2 diamond-like compound has intrinsically high thermoelectric performance with a figure of merit ( zT ) of 1.1 at 900 K, comparable to the best p-type diamond-like thermoelectric materials reported before. Such high zT is mainly due to the ultralow lattice thermal conductivity, which is fundamentally limited by the low-frequency Ag-Se "cluster vibrations," as confirmed by ab initio lattice dynamic calculations. Doping Cd at Ag sites significantly improves the thermoelectric performance in the low and medium temperature ranges. By using such high-performance n-type AgInSe 2 -based compounds, the diamond-like thermoelectric module has been fabricated for the first time. An output power of 0.06 W under a temperature difference of 520 K between the two ends of the module is obtained. This work opens a new window for the applications using the diamond-like thermoelectric materials.

  20. Effect of Sr-doping of LaMnO3 spacer on modulation-doped two-dimensional electron gases at oxide interfaces

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Gan, Yulin; Christensen, Dennis Valbjørn

    2017-01-01

    Modulation-doped oxide two-dimensional electron gas formed at the LaMnO3 (LMO) buffered disorderd-LaAlO3/SrTiO3 (d-LAO/LMO/STO) heterointerface provides new opportunities for electronics as well as quantum physics. Herein, we studied the dependence of Sr-doping of La1-xSrxMnO3 (LSMO, x = 0, 1/8, ...... of LSMO during the deposition of disordered LAO or that the energy levels of Mn 3d electrons at the interface of LSMO/STO are hardly varied even when changing the LSMO composition from LMO to SrMnO3....

  1. Exploring High-Performance n-Type Thermoelectric Composites Using Amino-Substituted Rylene Dimides and Carbon Nanotubes.

    Science.gov (United States)

    Wu, Guangbao; Zhang, Zhi-Guo; Li, Yongfang; Gao, Caiyan; Wang, Xin; Chen, Guangming

    2017-06-27

    Taking advantage of the high electrical conductivity of a single-walled carbon nanotube (SWCNT) and the large Seebeck coefficient of rylene diimide, a convenient strategy is proposed to achieve high-performance n-type thermoelectric (TE) composites containing a SWCNT and amino-substituted perylene diimide (PDINE) or naphthalene diimide (NDINE). The obtained n-type composites display greatly enhanced TE performance with maximum power factors of 112 ± 8 (PDINE/SWCNT) and 135 ± 14 (NDINE/SWCNT) μW m -1 K -2 . A short doping time of 0.5 h can ensure high TE performance. The corresponding TE module consisting of five p-n junctions reaches a large output power of 3.3 μW under a 50 °C temperature gradient. In addition, the n-type composites exhibit high air stability and excellent thermal stability. This design strategy benefits the future fabricating of high-performance n-type TE materials and devices.

  2. Electronic states in modulation doped p-AlGaN/GaN superlattices

    Science.gov (United States)

    Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Osinsky, A. V.; Norris, P. E.; Pearton, S. J.; Van Hove, J.; Wowchack, A. M.; Chow, P. P.

    2001-10-01

    The properties of p-AlGaN/GaN modulation doped superlattices (SLs) prepared by molecular beam epitaxy were studied by means of conductivity versus temperature, admittance spectroscopy, photoinduced current spectroscopy, microcathodoluminescence (MCL) spectra measurements, and measurements of effective diffusion lengths. It is shown that in SLs grown on GaN underlayers the sheet resistivity is about two orders of magnitude lower than for reference p-GaN films and the resistivity of SLs remains lower up to temperatures of about 350 °C. For SLs grown on AlGaN underlayers the gain in resistivity is much more moderate and certain advantages in using such SLs are envisaged only for temperatures below room temperature. The reason for this lower gain is a considerable decrease in hole mobility compared to p-GaN. The effect is somewhat tentatively attributed to worse crystalline perfection of these SLs. It is also shown that such SLs are characterized by a strongly broadened MCL peak and the presence of additional hole traps with activation energy of about 0.4 eV. Despite that, the photosensitivity and MCL intensity of these SLs are much better than for reference p-GaN samples.

  3. Structural elucidation of major selective androgen receptor modulator (SARM) metabolites for doping control.

    Science.gov (United States)

    Garg, Neeraj; Hansson, Annelie; Knych, Heather K; Stanley, Scott D; Thevis, Mario; Bondesson, Ulf; Hedeland, Mikael; Globisch, Daniel

    2018-01-31

    Selective androgen receptor modulators (SARMs) are a class of androgen receptor drugs, which have a high potential to be performance enhancers in human and animal sports. Arylpropionamides are one of the major SARM classes and get rapidly metabolized significantly complicating simple detection of misconduct in blood or urine sample analysis. Specific drug-derived metabolites are required as references due to a short half-life of the parent compound but are generally lacking. The difficulty in metabolism studies is the determination of the correct regio and stereoselectivity during metabolic conversion processes. In this study, we have elucidated and verified the chemical structure of two major equine arylpropionamide-based SARM metabolites using a combination of chemical synthesis and liquid chromatography-mass spectrometry (LC-MS) analysis. These synthesized SARM-derived metabolites can readily be utilized as reference standards for routine mass spectrometry-based doping control analysis of at least three commonly used performance-enhancing drugs to unambigously identify misconduct.

  4. Ce3+-Doping to Modulate Photoluminescence Kinetics for Efficient CsPbBr3 Nanocrystals Based Light-Emitting Diodes.

    Science.gov (United States)

    Yao, Ji-Song; Ge, Jing; Han, Bo-Ning; Wang, Kun-Hua; Yao, Hong-Bin; Yu, Hao-Lei; Li, Jian-Hai; Zhu, Bai-Sheng; Song, Ji-Zhong; Chen, Chen; Zhang, Qun; Zeng, Hai-Bo; Luo, Yi; Yu, Shu-Hong

    2018-03-14

    Inorganic perovskite CsPbBr 3 nanocrystals (NCs) are emerging, highly attractive light emitters with high color purity and good thermal stability for light-emitting diodes (LEDs). Their high photo/electroluminescence efficiencies are very important for fabricating efficient LEDs. Here, we propose a novel strategy to enhance the photo/electroluminescence efficiency of CsPbBr 3 NCs through doping of heterovalent Ce 3+ ions via a facile hot-injection method. The Ce 3+ cation was chosen as the dopant for CsPbBr 3 NCs by virtue of its similar ion radius and formation of higher energy level of conduction band with bromine in comparison with the Pb 2+ cation to maintain the integrity of perovskite structure without introducing additional trap states. It was found that by increasing the doping amount of Ce 3+ in CsPbBr 3 NCs to 2.88% (atomic percentage of Ce compared to Pb) the photoluminescence quantum yield (PLQY) of CsPbBr 3 NCs reached up to 89%, a factor of 2 increase in comparison with the native, undoped ones. The ultrafast transient absorption and time-resolved photoluminescence (PL) spectroscopy revealed that Ce 3+ -doping can significantly modulate the PL kinetics to enhance the PL efficiency of doped CsPbBr 3 NCs. As a result, the LED device fabricated by adopting Ce 3+ -doped CsPbBr 3 NCs as the emitting layers exhibited a pronounced improvement of electroluminescence with external quantum efficiency (EQE) from 1.6 to 4.4% via Ce 3+ -doping.

  5. Mass spectrometric characterization of the selective androgen receptor modulator (SARM) YK-11 for doping control purposes.

    Science.gov (United States)

    Thevis, Mario; Piper, Thomas; Dib, Josef; Lagojda, Andreas; Kühne, Dirk; Packschies, Lars; Geyer, Hans; Schänzer, Wilhelm

    2017-07-30

    Selective androgen receptor modulators (SARMs) represent an emerging class of therapeutics targeting inter alia conditions referred to as cachexia and sarcopenia. Due to their anabolic properties, the use of SARMs is prohibited in sports as regulated by the World Anti-Doping Agency (WADA), and doping control laboratories test for these anabolic agents in blood and urine. In order to accomplish and maintain comprehensive test methods, the characterization of new drug candidates is critical for efficient sports drug testing. Hence, in the present study the mass spectrometric properties of the SARM YK-11 were investigated. YK-11 was synthesized according to literature data and three different stable-isotope-labeled analogs were prepared to support the mass spectrometric studies. Using high-resolution/high-accuracy mass spectrometry following electrospray ionization as well as electron ionization, the dissociation pathways of YK-11 were investigated, and characteristic features of its (product ion) mass spectra were elucidated. These studies were flanked by density functional theory (DFT) computation providing information on proton affinities of selected functional groups of the analyte. The steroidal SARM YK-11 was found to readily protonate under ESI conditions followed by substantial in-source dissociation processes eliminating methanol, acetic acid methyl ester, and/or ketene. DFT computation yielded energetically favored structures of the protonated species resulting from the aforementioned elimination processes particularly following protonation of the steroidal D-ring substituent. Underlying dissociation pathways were suggested, supported by stable-isotope labeling of the analyte, and diagnostic product ions for the steroidal nucleus and the D-ring substituent were identified. Further, trimethylsilylated YK-11 and its deuterated analogs were subjected to electron ionization high-resolution/high-accuracy mass spectrometry, complementing the dataset characterizing

  6. Improved performance of quantum dot light emitting diode by modulating electron injection with yttrium-doped ZnO nanoparticles

    Science.gov (United States)

    Li, Jingling; Guo, Qiling; Jin, Hu; Wang, Kelai; Xu, Dehua; Xu, Yongjun; Xu, Gang; Xu, Xueqing

    2017-10-01

    In a typical light emitting diode (QD-LED), with ZnO nanoparticles (NPs) serving as the electron transport layer (ETL) material, excessive electron injection driven by the matching conduction band maximum (CBM) between the QD and this oxide layer usually causes charge imbalance and degrades the device performance. To address this issue, the electronic structure of ZnO NPs is modified by the yttrium (Y) doping method. We demonstrate that the CBM of ZnO NPs has a strong dependence on the Y-doping concentration, which can be tuned from 3.55 to 2.77 eV as the Y doping content increases from 0% to 9.6%. This CBM variation generates an enlarged barrier between the cathode and this ZnO ETL benefits from the modulation of electron injection. By optimizing electron injection with the use of a low Y-doped (2%) ZnO to achieve charge balance in the QD-LED, device performance is significantly improved with maximum luminance, peak current efficiency, and maximal external quantum efficiency increase from 4918 cd/m2, 11.3 cd/A, and 4.5% to 11,171 cd/m2, 18.3 cd/A, and 7.3%, respectively. This facile strategy based on the ETL modification enriches the methodology of promoting QD-LED performance.

  7. Enhanced electrical transport by texture modulation and co-doping for Ca3Co4O9+δ materials

    Directory of Open Access Journals (Sweden)

    Z.Y. Liu

    Full Text Available The powders as well as the texture modulated Ca2.8BaxPryCo4O9+δ (x, y = 0, 0.05, 0.1, 0.15 and 0.2 bulk materials are prepared via solid state reaction, sol–gel and spark plasma sintering method. The powder and bulk materials are analyzed with regard to their phase composition and microscopic character by X-ray diffraction (XRD and scanning electron microscope (SEM. The thermoelectric transport properties of the bulk materials are measured and investigated. The results show that the plate-like powders with uniform particle size tend to align regularly rather than the powders with anomaly shape and particle size distribution by spark plasma sintering method. The bulk materials co-doped by elements with lower electronegativity tend to form better texture rather than that of the bulk materials co-doped by elements with higher electronegativity via spark plasma sintering method. The resistivities and Seebeck coefficients are in negative accordance to the bulk material texture as a whole, and the carrier transport mechanism is not influenced. The electrical performance is tuned with optimized power factor 462 μW m−1 K−2 at 973 K for Ca2.8BaxPryCo4O9+δ (x = y = 0.1 bulk materials. Keywords: Ca3Co4O9+δ, Texture modulation, Co-doping, Thermoelectric properties

  8. Ferromagnetism modulation by phase change in Mn-doped GeTe chalcogenide magnetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Adam, Adam Abdalla Elbashir [Huazhong University of Science and Technology, School of Optical and Electronic Information, Wuhan (China); Wuhan National Laboratory for Optoelectronics, Wuhan (China); Alneelain University, Faculty of Science and Technology, Khartoum (Sudan); Cheng, Xiaomin; Guan, Xiawei; Miao, Xiangshui [Huazhong University of Science and Technology, School of Optical and Electronic Information, Wuhan (China); Wuhan National Laboratory for Optoelectronics, Wuhan (China)

    2014-12-15

    In this work, an effective method to modulate the ferromagnetic properties of Mn-doped GeTe chalcogenide-based phase change materials is presented. The microstructure of the phase change magnetic material Ge{sub 1-x} Mn{sub x} Te thin films was studied. The X-ray diffraction results demonstrate that the as-deposited films are amorphous, and the crystalline films are formed after annealing at 350 C for 10 min. Crystallographic structure investigation shows the existence of some secondary magnetic phases. The lattice parameters of Ge{sub 1-x} Mn{sub x} Te (x = 0.04, 0.12 and 0.15) thin films are found to be slightly different with changes of Mn compositions. The structural analysis clearly indicates that all the films have a stable rhombohedral face-centered cubic polycrystalline structure. The magnetic properties of the amorphous and crystalline Ge{sub 0.96}Mn{sub 0.04}Te were investigated. The measurements of magnetization (M) as a function of the magnetic field (H) show that both amorphous and crystalline phases of Ge{sub 0.96}Mn{sub 0.04}Te thin film are ferromagnetic and there is drastic variation between amorphous and crystalline states. The temperature (T) dependence of magnetizations at zero field cooling (ZFC) and field cooling (FC) conditions of the crystalline Ge{sub 0.96}Mn{sub 0.04}Te thin film under different applied magnetic fields were performed. The measured data at 100 and 300 Oe applied magnetic fields show large bifurcations in the ZFC and FC curves while on the 5,000 Oe magnetic field there is no deviation. (orig.)

  9. Dynamics of graded-composition and graded-doping semiconductor nanowires under local carrier modulation.

    Science.gov (United States)

    Deng, Wenjuan; Zou, Jijun; Peng, Xincun; Zhang, Jianbing; Wang, Weilu; Zhang, Yijun; Zhang, Daoli

    2016-10-17

    Scanning photocurrent microscopy is a powerful tool for investigating charge transfer and internal fields, which strongly influence carrier statics and dynamics in semiconductor nanowires. We performed comprehensive numerical modeling of the carrier dynamics of graded-composition and graded-doping AlGaAs nanowires to achieve a greater understanding of these nanowires. The simulation results indicated that the built-in electric field changes the shape of the scanning photocurrent microscopy profiles, which helped us to judge the dopant level, Al composition range and doping type of the material. The simulation results also assess the potential of the scanning photocurrent techniques in graded-doping and graded-composition nanowire properties.

  10. Intrinsic and doped coupled quantum dots created by local modulation of implantation in a silicon nanowire

    Science.gov (United States)

    Pierre, M.; Roche, B.; Wacquez, R.; Jehl, X.; Sanquer, M.; Vinet, M.

    2011-04-01

    We present a systematic study of various ways (top gates, local doping, substrate bias) to fabricate and tune multi-dot structures in silicon nanowire multigate metal-oxide-semiconductor field-effect transistors. The carrier concentration profile of the silicon nanowire is a key parameter to control the formation of tunnel barriers and single-electron islands. It is determined both by the doping profile of the nanowire and by the voltages applied to the top gates and to the substrate. Local doping is achieved with the realization of up to two arsenic implantation steps in combination with gates and nitride spacers acting as a mask. We compare nominally identical devices with different implantations and different voltages applied to the substrate, leading to the realization of both intrinsic and doped coupled dot structures. We demonstrate devices in which all the tunnel resistances toward the electrodes and between the dots can be independently tuned with the control top gates wrapping the silicon nanowire.

  11. Modulation Doping of Silicon using Aluminium-induced Acceptor States in Silicon Dioxide

    OpenAIRE

    K?nig, Dirk; Hiller, Daniel; Gutsch, Sebastian; Zacharias, Margit; Smith, Sean

    2017-01-01

    All electronic, optoelectronic or photovoltaic applications of silicon depend on controlling majority charge carriers via doping with impurity atoms. Nanoscale silicon is omnipresent in fundamental research (quantum dots, nanowires) but also approached in future technology nodes of the microelectronics industry. In general, silicon nanovolumes, irrespective of their intended purpose, suffer from effects that impede conventional doping due to fundamental physical principles such as out-diffusi...

  12. Fast switching of frequency modulation twisted nematic liquid crystal display fabricated by doping nanoparticles and its mechanism (Invited Paper)

    Science.gov (United States)

    Kobayashi, Shunsuke; Miyama, Tomohiro; Sakai, Yoshio; Shiraki, Hiroyuki; Shiraishi, Yukihide; Toshima, Naoki

    2005-04-01

    TN-LCDs fabricated by doping metal nanoparticles of such as Pd, Ag, Au, or Ag-Pd composite are shown to exhibit a frequency modulation electro-optic response with short response time of ms or sub-ms order. These devices are called FM-LCDs. The frequency range spreads from 40 Hz to 2 KHz around a dielectric relaxation frequency that increases with increasing the concentration of metal nanoparticles. This behavior is explained by the equivalent circuit model of heterogeneous dielectrics, for the first time, formulated by the present authors. Further, we discuss the origin of the fast response and the value of electrical conductivity of metal nanoparticles.

  13. The degrees of tri-axial orientation in RE-doped Bi2212 powders aligned in a modulated rotation magnetic field

    International Nuclear Information System (INIS)

    Nagai, R.; Horii, S.; Maeda, T.; Haruta, M.; Shimoyama, J.

    2013-01-01

    Highlights: •Tri-axial magnetic alignment of Bi2212 with rare-earth (RE) doping was attempted. •Magnetization axes depended on the type of doped RE ions. •RE-doping increased degrees of inplane orientation and inplane magnetic anisotropy. -- Abstract: We report relationship between the degrees of tri-axial orientation and doping level of rare earth (RE) ions in Bi 2 Sr 2 (Ca 1−x RE x )Cu 2 O y (RE-doped Bi2212; RE = Dy, Ho, Er and Tm) powder samples aligned under a modulated rotation magnetic field (MRF) of 10 T. Tri-axial magnetic alignment of the RE-doped Bi2212 with x = 0–0.5 was achieved by single-ion magnetic anisotropy of RE 3+ and tri-axial magnetic anisotropy induced by modulation microstructure in a grain level. The degrees of in-plane and c-axis orientation with ∼3° were achieved for the case of the Tm-doped Bi2212 with x = 0.5. The findings in the present study give us important information for the fabrication of triaxially oriented Bi-based cuprate superconductor materials by the magneto-scientific process

  14. N-Type Colloidal-Quantum-Dot Solids for Photovoltaics

    KAUST Repository

    Zhitomirsky, David

    2012-09-12

    N-type PbS colloidal-quantum-dot (CQD) films are fabricated using a controlled halide chemical treatment, applied in an inert processing ambient environment. The new materials exhibit a mobility of 0.1 cm2 V -1 s-1. The halogen ions serve both as a passivating agent and n-dope the films via substitution at surface chalcogen sites. The majority electron concentration across the range 1016 to 1018 cm-3 is varied systematically. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. N-type organic electrochemical transistors with stability in water

    KAUST Repository

    Giovannitti, Alexander

    2016-10-07

    Organic electrochemical transistors (OECTs) are receiving significant attention due to their ability to efficiently transduce biological signals. A major limitation of this technology is that only p-type materials have been reported, which precludes the development of complementary circuits, and limits sensor technologies. Here, we report the first ever n-type OECT, with relatively balanced ambipolar charge transport characteristics based on a polymer that supports both hole and electron transport along its backbone when doped through an aqueous electrolyte and in the presence of oxygen. This new semiconducting polymer is designed specifically to facilitate ion transport and promote electrochemical doping. Stability measurements in water show no degradation when tested for 2 h under continuous cycling. This demonstration opens the possibility to develop complementary circuits based on OECTs and to improve the sophistication of bioelectronic devices.

  16. Preparation of ohmic n-type cubic boron nitride contacts

    CERN Document Server

    Wang Cheng Xin; Li Xun; Zhang Tie Chen; Han Yong; Luo Ji Feng; Shen Cai Xia; Gao Chun Xi; Zou Guang Tian

    2002-01-01

    Ohmic electrodes in the form of n-type (Si-doped) cubic boron nitride (c-BN) bulk crystals were fabricated by utilizing a covering technique, depositing Ti(10 nm)/Mo/(20 nm)/Pt-Au(200 nm) ohmic contact metal on both the sides of the c-BN substrate. The size of the specimen electrode was 100 x 100 mu m sup 2 on one side and 300 x 300 mu m sup 2 on the other side. Measurements on the specimen were made using a specially made device. Linear current-voltage characteristics were obtained. It is considered that the contact between the Ti-and Si-doped c-BN was ohmic.

  17. Electron transport properties of degenerate n-type GaN prepared by pulsed sputtering

    Science.gov (United States)

    Ueno, Kohei; Fudetani, Taiga; Arakawa, Yasuaki; Kobayashi, Atsushi; Ohta, Jitsuo; Fujioka, Hiroshi

    2017-12-01

    We report a systematic investigation of the transport properties of highly degenerate electrons in Ge-doped and Si-doped GaN epilayers prepared using the pulsed sputtering deposition (PSD) technique. Secondary-ion mass spectrometry and Hall-effect measurements revealed that the doping efficiency of PSD n-type GaN is close to unity at electron concentrations as high as 5.1 × 1020 cm-3. A record low resistivity for n-type GaN of 0.16 mΩ cm was achieved with an electron mobility of 100 cm2 V-1 s-1 at a carrier concentration of 3.9 × 1020 cm-3. We explain this unusually high electron mobility of PSD n-type GaN within the framework of conventional scattering theory by modifying a parameter related to nonparabolicity of the conduction band. The Ge-doped GaN films show a slightly lower electron mobility compared with Si-doped films with the same carrier concentrations, which is likely a consequence of the formation of a small number of compensation centers. The excellent electrical properties presented in this letter clearly demonstrate the striking advantages of the low-temperature PSD technique for growing high-quality and highly conductive n-type GaN.

  18. Ion-doping as a strategy to modulate hydroxyapatite nanoparticle internalization.

    Science.gov (United States)

    Zhao, Z; Espanol, M; Guillem-Marti, J; Kempf, D; Diez-Escudero, A; Ginebra, M-P

    2016-01-21

    Although it is widely acknowledged that ionic substitutions on bulk hydroxyapatite substrates have a strong impact on their biological performance, little is known of their effect on nanoparticles (NPs) especially when used for gene transfection or drug delivery. The fact that NPs would be internalized poses many questions but also opens up many new possibilities. The objective of the present work is to synthesize and assess the effect of a series of hydroxyapatite-like (HA) NPs doped with various ions on cell behavior, i.e. carbonate, magnesium and co-addition. We synthesized NPs under similar conditions to allow comparison of results and different aspects in addition to assessing the effect of the doping ion(s) were investigated: (1) the effect of performing the cell culture study on citrate-dispersed NPs and on agglomerated NPs, (2) the effect of adding/excluding 10% of foetal bovine serum (FBS) in the cell culture media and (3) the type of cell, i.e. MG-63 versus rat mesenchymal stem cells (rMSCs). The results clearly demonstrated that Mg-doping had a major effect on MG-63 cells with high cytotoxicity but not to rMSCs. This was a very important finding because it proved that doping could be a tool to modify NP internalization. The results also suggest that NP surface charge had a large impact on MG-63 cells and prevents their internalization if it is too negative-this effect was less critical for rMSCs.

  19. Real-time measurement of photo-induced effects in 9,10-phenanthrenequinone-doped poly(methyl methacrylate) photopolymer by phase-modulated ellipsometry

    Science.gov (United States)

    Chuang, Chun-I.; Hsiao, Yi-Nan; Lin, Shiuan-Huei; Chao, Yu-Faye

    2010-09-01

    The photo-induced effects in 9,10-phenanthrenequinone-doped (PQ-doped) poly(methyl methacrylate) (PMMA) photopolymer were studied by phase-modulated ellipsometry and polarimetry in real time. The PQ-doped PMMA was exposed to an Ar/Kr tunable laser at the wavelength of 488 nm and measured by a HeNe laser (632.8 nm). We measured the induced birefringence and the variation of the refractive index separately during exposure; there was a difference of three orders of magnitude between these two effects. This suggested that the physical mechanism of holographic recording in PQ-doped PMMA is mainly due to the photo-induced variation in the refractive index.

  20. Uniaxial stress influence on lattice, band gap and optical properties of n-type ZnO: first-principles calculations

    International Nuclear Information System (INIS)

    Yang Ping; Li Pei; Zhang Li-Qiang; Wang Xiao-Liang; Wang Huan; Song Xi-Fu; Xie Fang-Wei

    2012-01-01

    The lattice, the band gap and the optical properties of n-type ZnO under uniaxial stress are investigated by first-principles calculations. The results show that the lattice constants change linearly with stress. Band gaps are broadened linearly as the uniaxial compressive stress increases. The change of band gap for n-type ZnO comes mainly from the contribution of stress in the c-axis direction, and the reason for band gap of n-type ZnO changing with stress is also explained. The calculated results of optical properties reveal that the imaginary part of the dielectric function decreases with the increase of uniaxial compressive stress at low energy. However, when the energy is higher than 4.0 eV, the imaginary part of the dielectric function increases with the increase of stress and a blueshift appears. There are two peaks in the absorption spectrum in an energy range of 4.0–13.0 eV. The stress coefficient of the band gap of n-type ZnO is larger than that of pure ZnO, which supplies the theoretical reference value for the modulation of the band gap of doped ZnO. (condensed matter: structural, mechanical, and thermal properties)

  1. Modulation of the electron transport properties in graphene nanoribbons doped with BN chains

    Directory of Open Access Journals (Sweden)

    Wu Liu

    2014-06-01

    Full Text Available Using density-functional theory and the non-equilibrium Green's function method, the electron transport properties of zigzag graphene nanoribbons (ZGNRs doped with BN chains are studied by systematically calculating the energy band structure, density of states and the transmission spectra for the systems. The BN chains destroyed the electronic transport properties of the ZGNRs, and an energy gap appeared for the ZGNRs, and displayed variations from a metal to a wide-gap semiconductor. With an increase in the number of BN chains, the band gap increased gradually in the band structure and the transmission coefficient decreased near the Fermi surface. Additionally, the doping position had a significant effect on the electronic properties of the ZGNRs.

  2. Complex quantum transport in a modulation doped strained Ge quantum well heterostructure with a high mobility 2D hole gas

    Science.gov (United States)

    Morrison, C.; Casteleiro, C.; Leadley, D. R.; Myronov, M.

    2016-09-01

    The complex quantum transport of a strained Ge quantum well (QW) modulation doped heterostructure with two types of mobile carriers has been observed. The two dimensional hole gas (2DHG) in the Ge QW exhibits an exceptionally high mobility of 780 000 cm2/Vs at temperatures below 10 K. Through analysis of Shubnikov de-Haas oscillations in the magnetoresistance of this 2DHG below 2 K, the hole effective mass is found to be 0.065 m0. Anomalous conductance peaks are observed at higher fields which deviate from standard Shubnikov de-Haas and quantum Hall effect behaviour due to conduction via multiple carrier types. Despite this complex behaviour, analysis using a transport model with two conductive channels explains this behaviour and allows key physical parameters such as the carrier effective mass, transport, and quantum lifetimes and conductivity of the electrically active layers to be extracted. This finding is important for electronic device applications, since inclusion of highly doped interlayers which are electrically active, for enhancement of, for example, room temperature carrier mobility, does not prevent analysis of quantum transport in a QW.

  3. Mass spectrometric characterization of urinary metabolites of the selective androgen receptor modulator andarine (S-4) for routine doping control purposes.

    Science.gov (United States)

    Thevis, Mario; Thomas, Andreas; Fusshöller, Gregor; Beuck, Simon; Geyer, Hans; Schänzer, Wilhelm

    2010-08-15

    Selective androgen receptor modulators (SARMs) are potent anabolic agents with tissue-selective properties. Due to their potential misuse in elite sport, the World Anti-Doping Agency (WADA) has prohibited SARMs since 2008, and although no representative drug candidate has yet received full clinical approval, recent findings of SARMs illegally sold via the internet have further supported the need to efficiently test for these compounds in doping controls. In the present communication, the mass spectrometric characterization of urinary metabolites of the SARM Andarine (also referred to as S-4) compared with earlier in vitro and animal studies is reported. Liquid chromatography interfaced to high-resolution/high-accuracy (tandem) mass spectrometry was used to identify phase I and II metabolites, confirming the predicted target analytes for sports drug testing purposes including the glucuronic acid conjugates of the active drug, its monohydroxylated and/or deacetylated product, the hydrolysis product resulting from the removal of the compound's B-ring, as well as the sulfate of the monohydroxylated and the deacetylated phase I metabolite. The obtained data will support future efforts to effectively screen for and confirm the misuse of the non-approved drug candidate Andarine. Copyright (c) 2010 John Wiley & Sons, Ltd.

  4. Screening for two selective androgen receptor modulators using gas chromatography-mass spectrometry in doping control analysis.

    Science.gov (United States)

    Thevis, Mario; Kohler, Maxie; Schlörer, Nils; Fusshöller, Gregor; Schänzer, Wilhelm

    2008-01-01

    Selective androgen receptor modulators (SARMs) have become a major field of clinical research enabling the tissue-selective stimulation of androgen receptors. The treatment of debilitating diseases, osteoporosis and frailty are primary goals and promising results have been obtained from clinical trials. However, the potential for misuse of SARMs in sport is great and drug testing methods based on liquid chromatography were established for different classes including arylpropionamide-, 2-quinolinone- and bicyclic hydantoin-derived compounds. As gas chromatography and mass spectrometry (GC-MS) are still important analytical tools in sports drug testing, a method to determine 2-quinolinone- and bicyclic hydantoin-derived SARMs established. Spiked urine samples were subjected to routine doping control protocols including enzymatic hydrolysis, liquid-liquid extraction, concentration and derivatisation to trimethylsilylated analogues followed by GC-MS analysis. The method was validated for the items specificity, lower limit of detection (0.2-10 ng mL(-1)), recovery (83-85%), intraday and interday precision (9-15% and 13-18%, respectively), which demonstrates the suitability of conventional GC-MS systems to determine representatives of an emerging class of compounds in doping control specimens.

  5. Field control of anisotropic spin transport and spin helix dynamics in a modulation-doped GaAs quantum well

    Science.gov (United States)

    Anghel, S.; Passmann, F.; Singh, A.; Ruppert, C.; Poshakinskiy, A. V.; Tarasenko, S. A.; Moore, J. N.; Yusa, G.; Mano, T.; Noda, T.; Li, X.; Bristow, A. D.; Betz, M.

    2018-03-01

    Electron spin transport and dynamics are investigated in a single, high-mobility, modulation-doped, GaAs quantum well using ultrafast two-color Kerr-rotation microspectroscopy, supported by qualitative kinetic theory simulations of spin diffusion and transport. Evolution of the spins is governed by the Dresselhaus bulk and Rashba structural inversion asymmetries, which manifest as an effective magnetic field that can be extracted directly from the experimental coherent spin precession. A spin-precession length λSOI is defined as one complete precession in the effective magnetic field. It is observed that application of (i) an out-of-plane electric field changes the spin decay time and λSOI through the Rashba component of the spin-orbit coupling, (ii) an in-plane magnetic field allows for extraction of the Dresselhaus and Rashba parameters, and (iii) an in-plane electric field markedly modifies both the λSOI and diffusion coefficient.

  6. Low-temperature radiation damage in silicon - 1: Annealing studies on N-type material

    International Nuclear Information System (INIS)

    Awadelkarim, O.O.

    1986-07-01

    The presence of electrically active defects in electron-irradiated P-doped n-type silicon was monitored using capacitance and loss factor measurements. Irradiations were performed at temperatures c - 0.14) eV and (E c - 0.24) eV in the gap are ascribed to the carbon interstitial and the divacancy, respectively. (author)

  7. Space-charge solitary waves and double layers in n-type ...

    Indian Academy of Sciences (India)

    S BANERJEE

    2018-02-20

    Feb 20, 2018 ... Abstract. Using quantum hydrodynamic (QHD) model and standard reductive perturbation method, we have investigated the formation and characteristics of space-charge solitary waves and double layers in n-type compen- sated drifting semiconductor plasma with varying doping profiles. Through ...

  8. Compositionally modulated multilayer diamond-like carbon coatings with AlTiSi multi-doping by reactive high power impulse magnetron sputtering

    Science.gov (United States)

    Dai, Wei; Gao, Xiang; Liu, Jingmao; Kwon, Se-Hun; Wang, Qimin

    2017-12-01

    Diamond-like carbon (DLC) coatings with AlTiSi multi-doping were prepared by a reactive high power impulse magnetron sputtering with using a gas mixture of Ar and C2H2 as precursor. The composition, microstructure, compressive stress, and mechanical property of the as-deposited DLC coatings were studied systemically by using SEM, XPS, TEM, Raman spectrum, stress-tester, and nanoindentation as a function of the Ar fraction. The results show that the doping concentrations of the Al, Ti and Si atoms increased as the Ar fraction increased. The doped Ti and Si preferred to bond with C while the doped Al mainly existed in oxidation state without bonding with C. As the doping concentrations increased, TiC carbide nanocrystals were formed in the DLC matrix. The microstructure of coatings changed from an amorphous feature dominant AlTiSi-DLC to a carbide nanocomposite AlTiSi-DLC with TiC nanoparticles embedding. In addition, the coatings exhibited the compositionally modulated multilayer consisting of alternate Al-rich layer and Al-poor layer due to the rotation of the substrate holder and the diffusion behavior of the doped Al which tended to separate from C and diffuse towards the DLC matrix surface owing to its weak interactions with C. The periodic Al-rich layer can effectively release the compressive stress of the coatings. On the other hand, the hard TiC nanoparticles were conducive to the hardness of the coatings. Consequently, the DLC coatings with relatively low residual stress and high hardness could be acquired successfully through AlTiSi multi-doping. It is believed that the AlCrSi multi-doping may be a good way for improving the comprehensive properties of the DLC coatings. In addition, we believe that the DLC coatings with Al-rich multilayered structure have a high oxidation resistance, which allows the DLC coatings application in high temperature environment.

  9. Modulating the electronic and optical properties of monolayer arsenene phases by organic molecular doping

    Science.gov (United States)

    Singh, Deobrat; Gupta, Sanjeev K.; Sonvane, Yogesh; Sahoo, Satyaprakash

    2017-12-01

    Recently, arsenene monolayer structure of the arsenic with two phases has displayed semiconducting behavior. We have systematically investigated the electronic and optical properties of single-layer arsenene with two types of functionalized organic molecules; an electrophilic molecule [tetracyanoquinodimethane (TCNQ)] and a nucleophilic molecule [tetrathiafulvalene (TTF)], as an electron acceptor and electron donor, respectively. The interfacial charge transfer between the arsenene monolayer and TCNQ/TTF molecules extensively reduces the band gap of arsenene and accordingly resulted in a p- or n-type semiconducting behavior, respectively. We have also performed the interfacial charge transfer from organic molecules to monolayer arsenene and vice versa. The interfacial surface molecular modification has established an efficient way to develop the light harvesting of arsenene in different polarization directions. Our theoretical investigation suggests that such n- and p-type arsenene semiconductors would broaden the applications in the field of nanoelectronic and optoelectronic devices such as photodiodes and it is also useful for constructing functional electronic systems.

  10. Simulation design of P–I–N-type all-perovskite solar cells with high efficiency

    International Nuclear Information System (INIS)

    Du Hui-Jing; Wang Wei-Chao; Gu Yi-Fan

    2017-01-01

    According to the good charge transporting property of perovskite, we design and simulate a p–i–n-type all-perovskite solar cell by using one-dimensional device simulator. The perovskite charge transporting layers and the perovskite absorber constitute the all-perovskite cell. By modulating the cell parameters, such as layer thickness values, doping concentrations and energy bands of n-, i-, and p-type perovskite layers, the all-perovskite solar cell obtains a high power conversion efficiency of 25.84%. The band matched cell shows appreciably improved performance with widen absorption spectrum and lowered recombination rate, so weobtain a high J _s_c of 32.47 mA/cm"2. The small series resistance of the all-perovskite solar cell also benefits the high J _s_c. The simulation provides a novel thought of designing perovskite solar cells with simple producing process, low production cost and high efficient structure to solve the energy problem. (paper)

  11. Samarium Doped Cerium Oxide Clusters: a Study on the Modulation of Electronic Structure

    Science.gov (United States)

    Topolski, Josey E.; Kafader, Jared O.; Marrero-Colon, Vicmarie; Chick Jarrold, Caroline

    2017-06-01

    Cerium oxide is known for its use in solid oxide fuel cells due to its high ionic conductivity. The doping of trivalent samarium atoms into cerium oxide is known to enhance the ionic conductivity through the generation of additional oxygen vacancies. This study probes the electronic structure of Sm_{x}Ce_{y}O_{z} (x+y=3, z=2-4) anion and neutral clusters. Anion photoelectron spectra of these mixed metal clusters exhibit additional spectral features not present in the previously studied cerium oxide clusters. Density functional theory calculations have been used to aid interpretation of collected spectra. The results of this work can be used to inform the design of materials used for solid oxide fuel cells.

  12. Trench process and structure for backside contact solar cells with polysilicon doped regions

    Science.gov (United States)

    De Ceuster, Denis; Cousins, Peter John; Smith, David D.

    2010-12-14

    A solar cell includes polysilicon P-type and N-type doped regions on a backside of a substrate, such as a silicon wafer. An interrupted trench structure separates the P-type doped region from the N-type doped region in some locations but allows the P-type doped region and the N-type doped region to touch in other locations. Each of the P-type and N-type doped regions may be formed over a thin dielectric layer. Among other advantages, the resulting solar cell structure allows for increased efficiency while having a relatively low reverse breakdown voltage.

  13. Trench process and structure for backside contact solar cells with polysilicon doped regions

    Science.gov (United States)

    De Ceuster, Denis; Cousins, Peter John; Smith, David D

    2013-05-28

    A solar cell includes polysilicon P-type and N-type doped regions on a backside of a substrate, such as a silicon wafer. An interrupted trench structure separates the P-type doped region from the N-type doped region in some locations but allows the P-type doped region and the N-type doped region to touch in other locations. Each of the P-type and N-type doped regions may be formed over a thin dielectric layer. Among other advantages, the resulting solar cell structure allows for increased efficiency while having a relatively low reverse breakdown voltage.

  14. Extrinsic doping in silicon revisited

    KAUST Repository

    Schwingenschlögl, Udo

    2010-06-17

    Both n-type and p-type doping of silicon is at odds with the charge transfer predicted by Pauling electronegativities and can only be reconciled if we no longer regarding dopant species as isolated atoms but rather consider them as clusters consisting of the dopant and its four nearest neighbor silicon atoms. The process that gives rise to n-type and p-type effects is the charge redistribution that occurs between the dopant and its neighbors, as we illustrate here using electronic structure calculations. This view point is able to explain why conventional substitutional n-type doping of carbon has been so difficult.

  15. Modulating indium doped tin oxide electrode properties for laccase electron transfer enhancement

    International Nuclear Information System (INIS)

    Diaconu, Mirela; Chira, Ana; Radu, Lucian

    2014-01-01

    Indium doped tin oxide (ITO) electrodes were functionalized with gold nanoparticles (GNPs) and cysteamine monolayer to enhance the heterogeneous electron transfer process of laccase from Trametes versicolor. The assembly of GNP on ITO support was performed through generation of H + species at the electrode surface by hydroquinone electrooxidation at 0.9 V vs Ag/AgCl. Uniform distribution of gold nanoparticle aggregates on electrode surfaces was confirmed by atomic force microscopy. The size of GNP aggregates was in the range of 200–500 nm. The enhanced charge transfer at the GNP functionalized ITO electrodes was observed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy. Electrocatalytic behavior of laccase immobilized on ITO modified electrode toward oxygen reduction reaction was evaluated using CV in the presence of 2,2′-azino-bis 3-ethylbenzothiazoline-6-sulfuric acid (ABTS). The obtained sigmoidal-shaped voltammograms for ABTS reduction in oxygen saturated buffer solution are characteristic for a catalytic process. The intensity of catalytic current increased linearly with mediator concentration up to 6.2 × 10 −4 M. The registered voltammogram in the absence of ABTS mediator clearly showed a significant faradaic current which is the evidence of the interfacial oxygen reduction. - Highlights: • Assembly of gold nanoparticles on indium tin oxide support at positive potentials • Electrochemical and morphological evaluation of the gold nanoparticle layer assembly • Bioelectrocatalytic oxygen reduction on laccase modified electrode

  16. Modulating indium doped tin oxide electrode properties for laccase electron transfer enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Diaconu, Mirela [National Institute for Biological Sciences, Centre of Bioanalysis, 296 Spl. Independentei, Bucharest 060031 (Romania); Chira, Ana [National Institute for Biological Sciences, Centre of Bioanalysis, 296 Spl. Independentei, Bucharest 060031 (Romania); Politehnica University of Bucharest, Faculty of Applied Chemistry and Materials Science, 1-7 Polizu Str., 011061 (Romania); Radu, Lucian, E-mail: gl_radu@chim.upb.ro [Politehnica University of Bucharest, Faculty of Applied Chemistry and Materials Science, 1-7 Polizu Str., 011061 (Romania)

    2014-08-28

    Indium doped tin oxide (ITO) electrodes were functionalized with gold nanoparticles (GNPs) and cysteamine monolayer to enhance the heterogeneous electron transfer process of laccase from Trametes versicolor. The assembly of GNP on ITO support was performed through generation of H{sup +} species at the electrode surface by hydroquinone electrooxidation at 0.9 V vs Ag/AgCl. Uniform distribution of gold nanoparticle aggregates on electrode surfaces was confirmed by atomic force microscopy. The size of GNP aggregates was in the range of 200–500 nm. The enhanced charge transfer at the GNP functionalized ITO electrodes was observed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy. Electrocatalytic behavior of laccase immobilized on ITO modified electrode toward oxygen reduction reaction was evaluated using CV in the presence of 2,2′-azino-bis 3-ethylbenzothiazoline-6-sulfuric acid (ABTS). The obtained sigmoidal-shaped voltammograms for ABTS reduction in oxygen saturated buffer solution are characteristic for a catalytic process. The intensity of catalytic current increased linearly with mediator concentration up to 6.2 × 10{sup −4} M. The registered voltammogram in the absence of ABTS mediator clearly showed a significant faradaic current which is the evidence of the interfacial oxygen reduction. - Highlights: • Assembly of gold nanoparticles on indium tin oxide support at positive potentials • Electrochemical and morphological evaluation of the gold nanoparticle layer assembly • Bioelectrocatalytic oxygen reduction on laccase modified electrode.

  17. Control of p-type and n-type thermoelectric properties of bismuth telluride thin films by combinatorial sputter coating technology

    Energy Technology Data Exchange (ETDEWEB)

    Goto, Masahiro, E-mail: goto.masahiro@nims.go.jp [Thermoelectric Materials Group, Center for Green Research on Energy and Environmental Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Thermal Management and Thermoelectric Materials Group, Center for Materials Research by Information Integration (CMI2), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Sasaki, Michiko [Thermal Management and Thermoelectric Materials Group, Center for Materials Research by Information Integration (CMI2), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Xu, Yibin [Thermal Management and Thermoelectric Materials Group, Center for Materials Research by Information Integration (CMI2), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Materials Database Group, Center for Materials Research by Information Integration (CMI2), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Zhan, Tianzhuo [Thermal Management and Thermoelectric Materials Group, Center for Materials Research by Information Integration (CMI2), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Isoda, Yukihiro [Thermoelectric Materials Group, Center for Green Research on Energy and Environmental Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Shinohara, Yoshikazu [Thermoelectric Materials Group, Center for Green Research on Energy and Environmental Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Thermal Management and Thermoelectric Materials Group, Center for Materials Research by Information Integration (CMI2), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

    2017-06-15

    Highlights: • p- and n-type bismuth telluride thin films have been synthesized using a combinatorial sputter coating system (COSCOS) while changing only one of the experimental conditions, the RF power. • The dimensionless figure of merit (ZT) was optimized by the technique. • The fabrication of a Π-structured TE device was demonstrated. - Abstract: p- and n-type bismuth telluride thin films have been synthesized by using a combinatorial sputter coating system (COSCOS). The crystal structure and crystal preferred orientation of the thin films were changed by controlling the coating condition of the radio frequency (RF) power during the sputter coating. As a result, the p- and n-type films and their dimensionless figure of merit (ZT) were optimized by the technique. The properties of the thin films such as the crystal structure, crystal preferred orientation, material composition and surface morphology were analyzed by X-ray diffraction, energy-dispersive X-ray spectroscopy and atomic force microscopy. Also, the thermoelectric properties of the Seebeck coefficient, electrical conductivity and thermal conductivity were measured. ZT for n- and p-type bismuth telluride thin films was found to be 0.27 and 0.40 at RF powers of 90 and 120 W, respectively. The proposed technology can be used to fabricate thermoelectric p–n modules of bismuth telluride without any doping process.

  18. Chemical redox modulated fluorescence of nitrogen-doped graphene quantum dots for probing the activity of alkaline phosphatase.

    Science.gov (United States)

    Liu, JingJing; Tang, Duosi; Chen, Zhitao; Yan, Xiaomei; Zhong, Zhou; Kang, Longtian; Yao, Jiannian

    2017-08-15

    Alkaline phosphatase (ALP) as an essential enzyme plays an important role in clinical diagnoses and biomedical researches. Hence, the development of convenient and sensitivity assay for monitoring ALP is extremely important. In this work, on the basis of chemical redox strategy to modulate the fluorescence of nitrogen-doped graphene quantum dots (NGQDs), a novel label-free fluorescent sensing system for the detection of alkaline phosphatase (ALP) activity has been developed. The fluorescence of NGQDs is firstly quenched by ultrathin cobalt oxyhydroxide (CoOOH) nanosheets, and then restored by ascorbic acid (AA), which can reduce CoOOH to Co 2+ , thus the ALP can be monitored based on the enzymatic hydrolysis of L-ascorbic acid-2-phosphate (AAP) by ALP to generate AA. Quantitative evaluation of ALP activity in a range from 0.1 to 5U/L with the detection limit of 0.07U/L can be realized in this sensing system. Endowed with high sensitivity and selectivity, the proposed assay is capable of detecting ALP in biological system with satisfactory results. Meanwhile, this sensing system can be easily extended to the detection of various AA-involved analytes. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Comparative analysis of full-gate and short-gate dielectric modulated electrically doped Tunnel-FET based biosensors

    Science.gov (United States)

    Sharma, Dheeraj; Singh, Deepika; Pandey, Sunil; Yadav, Shivendra; Kondekar, P. N.

    2017-11-01

    In this work, we have done a comprehensive study between full-gate and short-gate dielectrically modulated (DM) electrically doped tunnel field-effect transistor (SGDM-EDTFET) based biosensors of equivalent dimensions. However, in both the structures, dielectric constant and charge density are considered as a sensing parameter for sensing the charged and non-charged biomolecules in the given solution. In SGDM-EDTFET architecture, the reduction in gate length results a significant improvement in the tunneling current due to occurrence of strong coupling between gate and channel region which ensures higher drain current sensitivity for detection of the biomolecules. Moreover, the sensitivity of dual metal SGDM-EDTFET is compared with the single metal SGDM-EDTFET to analyze the better sensing capability of both the devices for the biosensor application. Further, the effect of sensing parameter i.e., ON-current (ION), and ION/IOFF ratio is analysed for dual metal SGDM-EDTFET in comparison with dual metal SGDM-EDFET. From the comparison, it is found that dual metal SGDM-EDTFET based biosensor attains relatively better sensitivity and can be utilized as a suitable candidate for biosensing applications.

  20. Quantitative analyses of enhanced thermoelectric properties of modulation-doped PEDOT:PSS/undoped Si (001) nanoscale heterostructures.

    Science.gov (United States)

    Lee, Dongwook; Sayed, Sayed Youssef; Lee, Sangyeop; Kuryak, Chris Adam; Zhou, Jiawei; Chen, Gang; Shao-Horn, Yang

    2016-12-01

    Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) has high electrical conductivity (∼10 3 S cm -1 ) but it exhibits a low Seebeck coefficient (PEDOT:PSS with nanostructured semiconductors can enhance the Seebeck coefficient and achieve an improved thermoelectric power factor. However, underlying mechanisms for those composite thermoelectric systems are scarcely understood so far. In this study, quantitative analyses on the electrical conductivity and Seebeck coefficient for the heterostructures of nanometer-thick PEDOT:PSS on single-crystal Si (001) on sapphire (SOS) are reported. The heterostructures have larger Seebeck coefficients up to 7.3 fold and power factors up to 17.5 fold relative to PEDOT:PSS. The electrical conductivity increased with decreasing combined thicknesses of PEDOT:PSS and Si, and the Seebeck coefficient increased with decreasing PEDOT:PSS thickness, which can be attributed to modulation doping caused by diffusion of holes from PEDOT:PSS into undoped Si. This hypothesis is supported by simulation per band alignment. The valence band offset between Si and PEDOT:PSS dominantly controls the electrical conductivity and Seebeck coefficient of the heterostructures. This study not only suggests mechanistic insights to increase the power factors of PEDOT:PSS-based composites but also opens the door for new strategies to enhance the thermoelectric efficiencies of heterostructured nanocomposite materials.

  1. Interface modulated currents in periodically proton exchanged Mg doped lithium niobate

    Energy Technology Data Exchange (ETDEWEB)

    Neumayer, Sabine M.; Rodriguez, Brian J., E-mail: brian.rodriguez@ucd.ie, E-mail: gallo@kth.se [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4 (Ireland); Manzo, Michele; Gallo, Katia, E-mail: brian.rodriguez@ucd.ie, E-mail: gallo@kth.se [Department of Applied Physics, KTH-Royal Institute of Technology, Roslagstullbacken 21, 10691 Stockholm (Sweden); Kholkin, Andrei L. [Department of Physics and CICECO-Aveiro Institute of Materials, 3810-193 Aveiro, Portugal and Institute of Natural Sciences, Ural Federal University, 620000 Ekaterinburg (Russian Federation)

    2016-03-21

    Conductivity in Mg doped lithium niobate (Mg:LN) plays a key role in the reduction of photorefraction and is therefore widely exploited in optical devices. However, charge transport through Mg:LN and across interfaces such as electrodes also yields potential electronic applications in devices with switchable conductivity states. Furthermore, the introduction of proton exchanged (PE) phases in Mg:LN enhances ionic conductivity, thus providing tailorability of conduction mechanisms and functionality dependent on sample composition. To facilitate the construction and design of such multifunctional electronic devices based on periodically PE Mg:LN or similar ferroelectric semiconductors, fundamental understanding of charge transport in these materials, as well as the impact of internal and external interfaces, is essential. In order to gain insight into polarization and interface dependent conductivity due to band bending, UV illumination, and chemical reactivity, wedge shaped samples consisting of polar oriented Mg:LN and PE phases were investigated using conductive atomic force microscopy. In Mg:LN, three conductivity states (on/off/transient) were observed under UV illumination, controllable by the polarity of the sample and the externally applied electric field. Measurements of currents originating from electrochemical reactions at the metal electrode–PE phase interfaces demonstrate a memresistive and rectifying capability of the PE phase. Furthermore, internal interfaces such as domain walls and Mg:LN–PE phase boundaries were found to play a major role in the accumulation of charge carriers due to polarization gradients, which can lead to increased currents. The insight gained from these findings yield the potential for multifunctional applications such as switchable UV sensitive micro- and nanoelectronic devices and bistable memristors.

  2. Nitrogen-doped carbon nanotubes and graphene composite structures for energy and catalytic applications.

    Science.gov (United States)

    Lee, Won Jun; Maiti, Uday Narayan; Lee, Ju Min; Lim, Joonwon; Han, Tae Hee; Kim, Sang Ouk

    2014-07-04

    Substitutional heteroatom doping is a promising route to modulate the outstanding material properties of carbon nanotubes and graphene for customized applications. Recently, (nitrogen-) N-doping has been introduced to ensure tunable work-function, enhanced n-type carrier concentration, diminished surface energy, and manageable polarization. Along with the promising assessment of N-doping effects, research on the N-doped carbon based composite structures is emerging for the synergistic integration with various functional materials. This invited feature article reviews the current research progress, emerging trends, and opening opportunities in N-doped carbon based composite structures. Underlying basic principles are introduced for the effective modulation of material properties of graphitic carbons by N-doping. Composite structures of N-doped graphitic carbons with various functional materials, including (i) polymers, (ii) transition metals, (iii) metal oxides, nitrides, sulphides, and (iv) semiconducting quantum dots are highlighted. Practical benefits of the synergistic composite structures are investigated in energy and catalytic applications, such as organic photovoltaics, photo/electro-catalysts, lithium ion batteries and supercapacitors, with a particular emphasis on the optimized interfacial structures and properties.

  3. Space-charge solitary waves and double layers in n-type compensated semiconductor quantum plasma

    Science.gov (United States)

    Banerjee, S.; Ghosh, B.

    2018-03-01

    Using quantum hydrodynamic (QHD) model and standard reductive perturbation method, we have investigated the formation and characteristics of space-charge solitary waves and double layers in n-type compensated drifting semiconductor plasma with varying doping profiles. Through numerical analysis, it is shown that the structures of space-charge solitary waves and double layers depend significantly on electron drift and compensation parameter which measures a comparative proportion of the donor, acceptor and intrinsic ion concentrations.

  4. A light-driven modulation of electric conductance through the adsorption of azobenzene onto silicon-doped- and pyridine-like N3-vacancy graphene.

    Science.gov (United States)

    Zhao, Jun; Liu, Chunyan; Ma, Jing

    2017-12-14

    The ability to modulate the conductance of an electronic device under light irradiation is crucial to the practical applications of nanoscale electronics. Density functional theory calculations predict that the conductance of the photo-responsive graphene-based nanocomposites can be tuned through the noncovalent adsorption of an azobenzene (AB) derivative onto pristine, Si-doped, and pyridine-like N 3 -vacancy graphene. AB@graphene systems were found to exhibit a visible-light response within the low-frequency region, rendering the trans-to-cis isomerizations of these nanocomposites under the irradiation of solar light. The excellent solar light absorption performances of these hybrids can then be used to modulate the conductance of both N 3 -vacancy- and Si-doped-graphene AB hybrids effectively through the reversible change of the effective conjugate length of the AB molecule in the photoisomerization. In addition, the solar thermal energy up to 1.53 eV per AB molecule can be stored in the designed nanocomposites with the doped graphene. These findings provide clues for making multifunctional materials with potential applications as both optically controlled nanoelectronics and solar energy storage devices.

  5. Bi2O2Se nanosheet: An excellent high-temperature n-type thermoelectric material

    Science.gov (United States)

    Yu, Jiabing; Sun, Qiang

    2018-01-01

    Motivated by the recent synthesis of an ultrathin film of layered Bi2O2Se [Wu et al., Nat. Nanotechnol. 12, 530 (2017); Wu et al., Nano Lett. 17, 3021 (2017)], we have systematically studied the thermoelectric properties of a Bi2O2Se nanosheet using first principles density functional theory combined with semiclassical Boltzmann transport theory. The calculated results indicate that the Bi2O2Se nanosheet exhibits a figure of merit (ZT) of 3.35 for optimal n-type doping at 800 K, which is much larger than the ZT value of 2.6 at 923 K in SnSe known as the most efficient thermoelectric material [Zhao et al., Nature 508, 373 (2014)]. Equally important, the high ZT in the n-type doped Bi2O2Se nanosheet highlights the efficiency of the reduced dimension on improving thermoelectric performance as compared with strain engineering by which the ZT of n-type doped bulk Bi2O2Se cannot be effectively enhanced.

  6. Thin-film metallic glass: an effective diffusion barrier for Se-doped AgSbTe2 thermoelectric modules

    Science.gov (United States)

    Yu, Chia-Chi; Wu, Hsin-Jay; Deng, Ping-Yuan; Agne, Matthias T.; Snyder, G. Jeffrey; Chu, Jinn P.

    2017-03-01

    The thermal stability of joints in thermoelectric (TE) modules, which are degraded during interdiffusion between the TE material and the contacting metal, needs to be addressed in order to utilize TE technology for competitive, sustainable energy applications. Herein, we deposit a 200 nm-thick Zr-based thin-film metallic glass (TFMG), which acts as an effective diffusion barrier layer with low electrical contact resistivity, on a high-zT Se-doped AgSbTe2 substrate. The reaction couples structured with TFMG/TE are annealed at 673 K for 8-360 hours and analyzed by electron microscopy. No observable IMCs (intermetallic compounds) are formed at the TFMG/TE interface, suggesting the effective inhibition of atomic diffusion that may be attributed to the grain-boundary-free structure of TFMG. The minor amount of Se acts as a tracer species, and a homogeneous Se-rich region is found nearing the TFMG/TE interface, which guarantees satisfactory bonding at the joint. The diffusion of Se, which has the smallest atomic volume of all the elements from the TE substrate, is found to follow Fick’s second law. The calculated diffusivity (D) of Se in TFMG falls in the range of D~10-20-10-23(m2/s), which is 106~107 and 1012~1013 times smaller than those of Ni [10-14-10-17(m2/s)] and Cu [10-8-10-11(m2/s)] in Bi2Te3, respectively.

  7. Novel electro-optical phase modulator based on GaInAs/InP modulation-doped quantum-well structures

    DEFF Research Database (Denmark)

    Thirstrup, C.

    1992-01-01

    A novel electro-optical phase modulator working at 1.55 µm is analyzed and proposed. It is shown by a numerical model that in a GaInAs/InP pn-nin-pn multiple-quantum-well waveguide structure, large optical phase modulation can be obtained at small intensity modulation and with improved performance...... compared to what is achieved in quantum confined Stark effect modulators of the same material system. The device proposed is based on a modulation of the quasi-Fermi energies of the electrons in the GaInAs quantum wells. This operational principle allows GHz modulation frequencies. Applied Physics Letters...

  8. Identification of selected in vitro generated phase-I metabolites of the steroidal selective androgen receptor modulator MK-0773 for doping control purposes.

    Science.gov (United States)

    Lagojda, Andreas; Kuehne, Dirk; Krug, Oliver; Thomas, Andreas; Wigger, Tina; Karst, Uwe; Schänzer, Wilhelm; Thevis, Mario

    2016-01-01

    Research into developing anabolic agents for various therapeutic purposes has been pursued for decades. As the clinical utility of anabolic-androgenic steroids has been found to be limited because of their lack of tissue selectivity and associated off-target effects, alternative drug entities have been designed and are commonly referred to as selective androgen receptor modulators (SARMs). While most of these SARMs are of nonsteroidal structure, the drug candidate MK-0773 comprises a 4-aza-steroidal nucleus. Besides the intended therapeutic use, SARMs have been found to be illicitly distributed and misused as doping agents in sport, necessitating frequently updated doping control analytical assays. As steroidal compounds reportedly undergo considerable metabolic transformations, the phase-I metabolism of MK-0773 was simulated using human liver microsomal (HLM) preparations and electrochemical conversion. Subsequently, major metabolic products were identified and characterized employing liquid chromatography-high-resolution/high- accuracy tandem mass spectrometry with electrospray (ESI) and atmospheric pressure chemical ionization (APCI) as well as nuclear magnetic resonance (NMR) spectroscopy. MK-0773 produced numerous phase-I metabolites under the chosen in vitro incubation reactions, mostly resulting from mono- and bisoxygenation of the steroid. HLM yielded at least 10 monooxygenated species, while electrochemistry-based experiments resulted predominantly in three monohydroxylated metabolites. Elemental composition data and product ion mass spectra were generated for these analytes, ESI/APCI measurements corroborated the formation of at least two N-oxygenated metabolites, and NMR data obtained from electrochemistry-derived products supported structures suggested for three monohydroxylated compounds. Hereby, the hydroxylation of the A-ring located N- bound methyl group was found to be of particular intensity. In the absence of controlled elimination studies, the

  9. Characterization of equine urinary metabolites of selective androgen receptor modulators (SARMs) S1, S4 and S22 for doping control purposes.

    Science.gov (United States)

    Hansson, Annelie; Knych, Heather; Stanley, Scott; Thevis, Mario; Bondesson, Ulf; Hedeland, Mikael

    2015-08-01

    Selective androgen receptor modulators, SARMs, constitute a class of compounds with anabolic properties but with few androgenic side-effects. This makes them possible substances of abuse and the World Anti-Doping Agency (WADA) has banned the entire class of substances. There have been several cases of illicit use of aryl propionamide SARMs in human sports and in 2013, 13 cases were reported. These substances have been found to be extensively metabolized in humans, making detection of metabolites necessary for doping control. SARMs are also of great interest to equine doping control, but the in vivo metabolite pattern and thus possible analytical targets have not been previously studied in this species. In this study, the urinary metabolites of the SARMs S1, S4, and S22 in horses were studied after intravenous injection, using ultra high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC-QToF-MS). Eight different metabolites were found for SARM S1, nine for SARM S4, and seven for SARM S22. The equine urinary metabolite profiles differed significantly from those of humans. The parent compounds were only detected for SARMs S4 and S22 and only at the first sampling time point at 3 h post administration, making them unsuitable as target compounds. For all three SARMs tested, the metabolite yielding the highest response had undergone amide hydrolysis, hydroxylation and sulfonation. The resulting phase II metabolites (4-nitro-3-trifluoro-methyl-phenylamine sulfate for SARMs S1 and S4 and 4-cyano-3-trifluoro-methyl-phenylamine sulfate for SARM S22) are proposed as analytical targets for use in equine doping control. Copyright © 2015 John Wiley & Sons, Ltd.

  10. Some aspects of hydrogen plasma treatment of anti-modulation doped near surface GaAs/AlGaAs single quantum well structures

    International Nuclear Information System (INIS)

    Bumai, Yu.A.; Gobsch, G.; Goldhahn, R.; Stein, N.; Golombek, A.; Nakov, V.; Cheng, T.S.

    1999-01-01

    The MBE grown anti-modulation doped GaAs/AlGaAs structures with near surface single quantum wells were exposed to a DC hydrogen plasma (∼400 eV) and investigated using PL, PLE and PR spectroscopy at 5 K. Strong acceptor related free to bound transition (FB) dominates for quantum well related PL but excitonic features are still observed in PLE spectra. After hydrogen plasma treatment the PL intensity of FB transition from quantum well was strongly increased for above AlGaAs band gap excitation and was unchanged for below AlGaAs one. These results are consistent with atomic hydrogen passivation of deep defects in AlGaAs barriers. At the same time radiative excitonic recombination was quenched by hydrogenation. PLE and PR spectra indicate on a strong increase of electric field in subsurface region of the structure after hydrogenation. The increase of electric field in anti-modulation doped structure after hydrogen plasma treatment is supposed to be due to passivation by atomic hydrogen of surface states that leads to unpinning of Fermi level from mid gap to carbon acceptor level position in GaAs cap layer. It causes the further band bending and surface electric field increase that strongly suppress excitonic recombination in near surface quantum wells

  11. Nonlinear THz spectroscopy on n-type GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Gaal, Peter

    2008-06-23

    In this thesis, the ultrafast dynamics of conduction band electrons in semiconductors are investigated by nonlinear terahertz (THz) spectroscopy. In particular, n-doped gallium arsenide samples with doping concentrations in the range of 10{sup 16} cm{sup -3} to 10{sup 17} cm{sup -3} are studied. A novel source for the generation of intense THz radiation is developed which yields single-cycle THz transients with field amplitudes of more then 400 kV/cm. The THz source uses ultrashort optical laser pulses provided by a Ti:sapphire oscillator. In addition, a two-color THz-pump mid-infrared-probe setup is implemented, which allows for two-dimensional time-resolved experiments in the far-infrared wavelength range. Field ionization of neutral shallow donors in gallium arsenide with intense, ultrashort THz pulses and subsequent coherent radiative recombination of electrons to impurity ground states is observed at room temperature. The superradiant decay of the nonlinear polarization results in the emission of a coherent signal with picosecond lifetimes. Such nonlinear signals, which exhibit a lifetime ten times longer than in the linear regime are observed for the first time. At low temperatures and THz field strengths below 5 kV/cm, Rabi flopping on shallow donor transitions is demonstrated. For the first time, the polar electron-LO phonon interaction is directly measured in the quantum kinetic transport regime. Quasi-instantaneous acceleration of conduction band electrons in the polar gallium arsenide lattice by the electric field of intense THz pulses and subsequent probing of the mid-infrared transmission reveals a modulation of the transmission along the THz-mid-infrared delay coordinate with the frequency of the LO phonon. These modulations directly display the relative phase between the electron motion and its surrounding virtual phonon cloud. Quantum kinetic model calculations fully account for the observed phenomena. (orig.)

  12. In vitro metabolism studies on the selective androgen receptor modulator (SARM) LG121071 and its implementation into human doping controls using liquid chromatography-mass spectrometry.

    Science.gov (United States)

    Knoop, Andre; Krug, Oliver; Vincenti, Marco; Schänzer, Wilhelm; Thevis, Mario

    2015-01-01

    LG121071 is a member of the tetrahydroquinolinone-based class of selective androgen receptor modulator (SARM) drug candidates. These nonsteroidal compounds are supposed to act as full anabolic agents with reduced androgenic properties. As SARMs provide an alternative to anabolic androgenic steroids, they represent an emerging class of potential doping substances abused by athletes for illicit performance enhancement. According to the World Anti-Doping Agency's regulations, SARMs are banned substances and part of the Prohibited List since 2008. In consideration of the increasing number of adverse analytical findings in doping controls caused by SARMs abuse, potential drug candidates such as LG121071 have been proactively investigated to enable a timely integration into routine testing procedures even though clinical trials are not yet complete. In the present approach, the collision-induced dissociation (CID) of LG121071 was characterized by means of electrospray ionization-high resolution/high accuracy mass spectrometry, MS(n), and isotope labeling experiments. Interestingly, the even-electron precursor ion [M + H](+) at m/z 297 was found to produce a radical cation at m/z 268 under CID conditions, violating the even-electron rule that commonly applies. For doping control purposes, metabolites were generated in vitro and a detection method for urine samples based on liquid chromatography-tandem mass spectrometry was established. The overall metabolic conversion of LG121071 was modest, yielding primarily mono-, bis- and trishydroxylated species. Notable, however, was the identification of a glucuronic acid conjugate of the intact drug, attributed to an N-glucuronide structure. The sample preparation procedure included the enzymatic hydrolysis of glucuronides prior to liquid-liquid extraction, allowing intact LG121071 to be measured, as well as the corresponding phase-I metabolites. The method was characterized concerning inter alia lower limit of detection (0

  13. Formation of photoluminescent n-type macroporous silicon: Effect of magnetic field and lateral electric potential

    Energy Technology Data Exchange (ETDEWEB)

    Antunez, E.E. [Centro de Investigación en Ingeniería y Ciencias Aplicadas, UAEM, Av. Universidad 1001, Col. Chamilpa, Cuernavaca, Morelos, CP 62210 (Mexico); Estevez, J.O. [Instituto de Física, B. Universidad Autónoma de Puebla, A.P. J-48, Puebla 72570 (Mexico); Campos, J. [Instituto de Energías Renovables, UNAM, Priv. Xochicalco S/N, Temixco, Morelos, CP 62580 (Mexico); Basurto-Pensado, M.A. [Centro de Investigación en Ingeniería y Ciencias Aplicadas, UAEM, Av. Universidad 1001, Col. Chamilpa, Cuernavaca, Morelos, CP 62210 (Mexico); Agarwal, V., E-mail: vagarwal@uaem.mx [Centro de Investigación en Ingeniería y Ciencias Aplicadas, UAEM, Av. Universidad 1001, Col. Chamilpa, Cuernavaca, Morelos, CP 62210 (Mexico)

    2014-11-15

    Metal electrode-free electrochemical etching of low doped n-type silicon substrates, under the combined effect of magnetic and lateral electric field, is used to fabricate photoluminescent n-type porous silicon structures in dark conditions. A lateral gradient in terms of structural characteristics (i.e. thickness and pore dimensions) along the electric field direction is formed. Enhancement of electric and magnetic field resulted in the increase of pore density and a change in the shape of the macropore structure, from circular to square morphology. Broad photoluminescence (PL) emission from 500 to 800 nm, with a PL peak wavelength ranging from 571 to 642 nm, is attributed to the wide range of microporous features present on the porous silicon layer.

  14. The Effect of SbI3 Doping on the Structure and Electrical Properties of n-Type Bi1.8Sb0.2Te2.85Se0.15 Alloy Prepared by the Free Growth Method

    Science.gov (United States)

    Wang, Xiaoyu; Yu, Yuan; Zhu, Bin; Gao, Na; Huang, Zhongyue; Xiang, Bo; Zu, Fangqiu

    2018-02-01

    Thermoelectric technology is regarded as one of the most promising direct power generation techniques via thermoelectric materials. However, the batch production and scale-up application are hindered because of the high-cost and poor performance. In this work, we adopt the free growth method to synthesize a series of the bulk materials of SbI3-doped Bi1.8Sb0.2Te2.85Se0.15 alloys. The structural and component investigations as well as the electrical properties characterization are carried out. The results show that SbI3 promotes the formation of Te-rich regions in the matrix. In addition, the synergistically optimized electrical conductivity and Seebeck coefficient are attained by controlling the SbI3 doping concentration. Thus, the sample with 0.30 wt.% SbI3 displays a highly increased power factor of ˜ 13.57 μW cm-1 K-2, which is nearly 21 times higher than that of the undoped one. Moreover, the free growth method is reproducible, convenient and economical. Therefore, it has great potential as a promising technology for the batch synthesis.

  15. In situ growth of p and n-type graphene thin films and diodes by pulsed laser deposition

    KAUST Repository

    Sarath Kumar, S. R.

    2013-11-07

    We report the in situ growth of p and n-type graphene thin films by ultraviolet pulsed laser deposition in the presence of argon and nitrogen, respectively. Electron microscopy and Raman studies confirmed the growth, while temperature dependent electrical conductivity and Seebeck coefficient studies confirmed the polarity type of graphene films. Nitrogen doping at different sites of the honeycomb structure, responsible for n-type conduction, is identified using X-ray photoelectron spectroscopy, for films grown in nitrogen. A diode-like rectifying behavior is exhibited by p-n junction diodes fabricated using the graphene films.

  16. New Method for Determination of Electrically Inactive Phosphorus in n-type Emitters

    OpenAIRE

    Steyer, Michael; Dastgheib-Shirazi, Amir; Hahn, Giso; Terheiden, Barbara

    2015-01-01

    The precise knowledge of the amount and the location in depth of inactive phosphorus in an n-type emitter is still a challenge. As a new approach, we determine the total amount of phosphorus (P dose) in the emitter stepwise in dependence of etching depth with the characterization tool ICP-OES. A comparison of the data with the electrically active P concentration profile measured by ECV allows to determine in which depths electrically inactive phosphorus is present. For a highly doped emitter,...

  17. Diffusion of acceptors in n-type and semi-insulating InP

    Science.gov (United States)

    Tuck, Brian

    2000-01-01

    When acceptors diffuse into an n-type semiconductor, both the surface concentration and the diffusion depth of the diffusant are influenced by the initial donor concentration. Similar interaction is observed between shallow acceptors and deep acceptors. Previous work describing the diffusion of zinc during MOCVD growth of InP is reviewed and compared to the diffusion of both zinc and cadmium into InP from the vapour phase. Interdiffusion between iron- and zinc-doped MOCVD layers is also considered. It is shown that these experiments can all be explained by a simple model involving Fermi level effects.

  18. Regulating Mid-infrared to Visible Fluorescence in Monodispersed Er3+-doped La2O2S (La2O2SO4) Nanocrystals by Phase Modulation

    Science.gov (United States)

    Pan, Qiwen; Yang, Dandan; Kang, Shiliang; Qiu, Jianrong; Dong, Guoping

    2016-11-01

    Rare earth doped mid-infrared (MIR) fluorescent sources have been widely investigated due to their various potential applications in the fields of communication, chemical detecting, medical surgery and so forth. However, with emission wavelength extended to MIR, multiphonon relaxation process that strongly quenched the MIR emission is one of the greatest challenges for such practical applications. In our design, we have described a controllable gas-aided annealing strategy to modulate the phase, crystal size, morphology and fluorescent performance of a material simultaneously. Uniform and monodispersed Er3+-doped La2O2S and La2O2SO4 nanocrystals with a similar lattice structure, crystallinity, diameter and morphology have been introduced to investigate the impact of multiphonon relaxation on luminescence performance. Detailed spectroscopic evolutions in the region of MIR, near-infrared (NIR), visible upconversion (UC) and their corresponding decay times provide insight investigation into the fluorescent mechanism caused by multiphonon relaxation. A possible energy transfer model has also been established. Our results present direct observation and mechanistic investigation of fluorescent evolution in multiphonon relaxation process, which is conductive to design MIR fluorescent materials in the future. To the best of our knowledge, it is the first investigation on MIR fluorescent performance of La2O2S nanocrystals, which may find various applications in many photoelectronic fields.

  19. Bulk oxides: asymmetry between p-and n-type transport properties

    Science.gov (United States)

    Maignan, Antioine

    2015-03-01

    The thermoelectric power (TEP) of transition metal oxides shows large difference depending on the sign of the charge carriers. In electron-doped oxides, the best TEs in terms of the figure of merit are heavily doped transparent conductors (as doped ZnO). The physics is very similar to that of semiconductors, though the defects chemistry differs: the existence of planar defects created by the doping elements, is far from the random distribution in semiconductors. In contrast the best p-types are layered cobaltites (CdI2 -type layers with edge-shared CoO6 octahedras). The Co cations adopt a low spin state. Both electronic correlations and spin entropy have to be considered to explain the S(T) curve for T 150K, the spin/orbital configurations and the doping level in the generalized Heikes formula are dominating. This description supported by the results obtained for perovskite ruthenates was recently unvalidated for the quadruple perovskite ACu3Ru4O12, showing very different S(T) without S saturation up to ~ 900K. Their Pauli paramagnetism enlights the role of the spins upon thermopower. Similarly, searching for other n-types, interesting TE properties have been found in Ba1.2Mn8O16: the S(T) evidences a charge/orbital ordering in this manganite (vMn = 3.7) coupled to an abrupt change in the unit-cell volume. Ba1.2Mn8O16, although of n-type, exhibits a cst. | S | ~ 92 μV.K-1 for T>400K, explained by the generalized Heikes formula rather used for p-type. This difference with other n-type oxides is related to the Mn3+/Mn4+ magnetism and the contribution of eg orbitals for the transport properties. In this presentation, the richness of the TE properties of metal transition oxides will be emphasized focusing on the important role of the spins.

  20. Quantum oscillations and interference effects in strained n- and p-type modulation doped GaInNAs/GaAs quantum wells

    Science.gov (United States)

    Sarcan, F.; Nutku, F.; Donmez, O.; Kuruoglu, F.; Mutlu, S.; Erol, A.; Yildirim, S.; Arikan, M. C.

    2015-08-01

    We have performed magnetoresistance measurements on n- and p-type modulation doped GaInNAs/GaAs quantum well (QW) structures in both the weak (B  magnetoresistance traces are used to extract the spin coherence, phase coherence and elastic scattering times as well Rashba parameters and spin-splitting energy. The calculated Rashba parameters for nitrogen containing samples reveal that the nitrogen composition is a significant parameter to determine the degree of the spin-orbit interactions. Consequently, GaInNAs-based QW structures with various nitrogen compositions can be beneficial to adjust the spin-orbit coupling strength and may be used as a candidate for spintronics applications.

  1. The Impact of Metallic Impurities on Minority Carrier Lifetime in High Purity N-type Silicon

    Science.gov (United States)

    Yoon, Yohan

    Boron-doped p-type silicon is the industry standard silicon solar cell substrate. However, it has serious limitations: iron boron (Fe-B) pairs and light induced degradation (LID). To suppress LID, the replacement of boron by gallium as a p-type dopant has been proposed. Although this eliminates B-O related defects, gallium-related pairing with iron, oxygen, and carbon can reduce lifetime in this material. In addition resistivity variations are more pronounced in gallium doped ingots, however Continuous-Czochralski (c-Cz) growth technologies are being developed to overcome this problem. In this work lifetime limiting factors and resistivity variations have been investigated in this material. The radial and axial variations of electrically active defects were observed using deep level transient spectroscopy (DLTS) these have been correlated to lifetime and resistivity variations. The DLTS measurements demonstrated that iron-related pairs are responsible for the lifetime variations. Specifically, Fe-Ga pairs were found to be important recombination sites and are more detrimental to lifetime than Fei. Typically n-type silicon has a higher minority carrier lifetime than p-type silicon with similar levels of contamination. That is because n-type silicon is more tolerant to metallic impurities, especially Fe. Also, it has no serious issues in relation to lifetime degradation, such as FeB pairs and light-induced degradation (LID). However, surface passivation of the p + region in p+n solar cells is much more problematic than the n+p case where silicon nitride provides very effective passivation of the cell. SiO2 is the most effective passivation for n type surfaces, but it does not work well on B-doped surfaces, resulting in inadequate performance. Al2O3 passivation layer suggested for B-doped emitters. With this surface passivation layer a 23.2 % conversion efficiency has been achieved. After this discovery n-type silicon is now being seriously considered for

  2. Attempting to realize n-type BiCuSeO

    Science.gov (United States)

    Zhang, Xiaoxuan; Feng, Dan; He, Jiaqing; Zhao, Li-Dong

    2018-02-01

    As an intrinsic p-type semiconductor, BiCuSeO has been widely researched in the thermoelectric community, however, n-type BiCuSeO has not been reported so far. In this work, we successfully realized n-type BiCuSeO through carrying out several successive efforts. Seebeck coefficient of BiCuSeO was increased through introducing extra Bi/Cu to fill the Bi/Cu vacancies that may produce holes, and the maximum Seebeck coefficient was increase from +447 μVK-1 for undoped BiCuSeO to +638 μVK-1 for Bi1.04Cu1.05SeO. The Seebeck coefficient of Bi1.04Cu1.05SeO was changed from p-type to n-type through electron doping through introducing Br/I in Se sites, the maximum negative Seebeck coefficient can reach ∼ -465 μVK-1 and -543 μVK-1 for Bi1.04Cu1.05Se1-xIxO and Bi1.04Cu1.05Se1-xBrxO, respectively. Then, after compositing Bi1.04Cu1.05Se0.99Br0.01O with Ag, n-type BiCuSeO can be absolutely obtained in the whole temperature range of 300-873 K, the maximum ZT 0.05 was achieved at 475 K in the Bi1.04Cu1.05Se0.99Br0.01O+15% Ag. Our report indicates that it is possible to realize n-type conducting behaviors in BiCuSeO system.

  3. N-type solar cells: advantages, issues, and current scenarios

    Science.gov (United States)

    Singha, Bandana; Solanki, Chetan S.

    2017-07-01

    Crystalline silicon, including p-type czochralski (CZ) mono-crystalline and multi-crystalline (mc) silicon, has been the workhorse for solar cell production for decades. In recent years, there has been many developments in n-type c-Si solar cells basically due to the advantages of n-type c-Si wafers over p-type wafers. However, there are some limitations in making n-type solar cells considering the technologies involved to fabricate p-type cells. In this paper, different advantages of n-types wafers, their limitations in solar cell production, and an analysis of total market coverage are discussed.

  4. Unintentional high-density p-type modulation doping of a GaAs/AlAs core-multishell nanowire.

    Science.gov (United States)

    Jadczak, J; Plochocka, P; Mitioglu, A; Breslavetz, I; Royo, M; Bertoni, A; Goldoni, G; Smolenski, T; Kossacki, P; Kretinin, A; Shtrikman, Hadas; Maude, D K

    2014-05-14

    Achieving significant doping in GaAs/AlAs core/shell nanowires (NWs) is of considerable technological importance but remains a challenge due to the amphoteric behavior of the dopant atoms. Here we show that placing a narrow GaAs quantum well in the AlAs shell effectively getters residual carbon acceptors leading to an unintentional p-type doping. Magneto-optical studies of such a GaAs/AlAs core-multishell NW reveal quantum confined emission. Theoretical calculations of NW electronic structure confirm quantum confinement of carriers at the core/shell interface due to the presence of ionized carbon acceptors in the 1 nm GaAs layer in the shell. Microphotoluminescence in high magnetic field shows a clear signature of avoided crossings of the n = 0 Landau level emission line with the n = 2 Landau level TO phonon replica. The coupling is caused by the resonant hole-phonon interaction, which points to a large two-dimensional hole density in the structure.

  5. Controlling mode instabilities at 628 W average output power in an Yb-doped rod-type fiber amplifier by active modulation of the pump power

    Science.gov (United States)

    Stihler, Christoph; Jauregui, Cesar; Otto, Hans-Jürgen; Limpert, Jens; Tünnermann, Andreas

    2017-02-01

    The phenomenon of transverse mode instabilities (TMI) is currently the most limiting effect for the scaling of the average output power of fiber laser systems with nearly diffraction-limited beam quality. Thus, it is of high interest to develop efficient mitigation strategies to further enhance the performance of fiber laser systems. By actively modulating the pump power of an Yb-doped rod-type fiber amplifier, it was possible to weaken the thermally-induced refractive index grating along the fiber and, thus, to mitigate TMI to a large extent. A significant advantage of this approach is that it can be easily integrated in any existing fiber-laser system since no further optical components are needed. A function generator connected to the pump diode driver was used to achieve the modulation. With this setup we were able to extract a fully stabilized beam at 1.5 times above the TMI threshold. Furthermore, a stabilization of the beam was still feasible at an average output power of 628 W, which is more than three times higher than the free-running TMI threshold of that particular fiber under identical conditions (e.g. seed power). This is the highest average output power reported from a single-channel rod-type fiber amplifier with a high-quality stabilized beam, to the best of our knowledge.

  6. Borazino-Doped Polyphenylenes.

    Science.gov (United States)

    Marinelli, Davide; Fasano, Francesco; Najjari, Btissam; Demitri, Nicola; Bonifazi, Davide

    2017-04-19

    The divergent synthesis of two series of borazino-doped polyphenylenes, in which one or more aryl units are replaced by borazine rings, is reported for the first time, taking advantage of the decarbonylative [4 + 2] Diels-Alder cycloaddition reaction between ethynyl and tetraphenylcyclopentadienone derivatives. Because of the possibility of functionalizing the borazine core with different groups on the aryl substituents at the N and B atoms of the borazino core, we have prepared borazino-doped polyphenylenes featuring different doping dosages and orientations. To achieve this, two molecular modules were prepared: a core and a branching unit. Depending on the chemical natures of the central aromatic module and the reactive group, each covalent combination of the modules yields one exclusive doping pattern. By means of this approach, three- and hexa-branched hybrid polyphenylenes featuring controlled orientations and dosages of the doping B 3 N 3 rings have been prepared. Detailed photophysical investigations showed that as the doping dosage is increased, the strong luminescent signal is progressively reduced. This suggests that the presence of the B 3 N 3 rings engages additional deactivation pathways, possibly involving excited states with an increasing charge-separated character that are restricted in the full-carbon analogues. Notably, a strong effect of the orientational doping on the fluorescence quantum yield was observed for those hybrid polyphenylene structures featuring low doping dosages. Finally, we showed that Cu-catalyzed 1,3-dipolar cycloaddition is also chemically compatible with the BN core, further endorsing the inorganic benzene as a versatile aromatic scaffold for engineering of molecular materials with tailored and exploitable optoelectronic properties.

  7. Aptameric Recognition-Modulated Electroactivity of Poly(4-Styrenesolfonic Acid)-Doped Polyaniline Films for Single-Shot Detection of Tetrodotoxin

    Science.gov (United States)

    Fomo, Gertrude; Waryo, Tesfaye T.; Sunday, Christopher E.; Baleg, Abd A.; Baker, Priscilla G.; Iwuoha, Emmanuel I.

    2015-01-01

    The work being reported is the first electrochemical sensor for tetrodotoxin (TTX). It was developed on a glassy carbon electrodes (C) that was modified with poly(4-styrenesolfonic acid)-doped polyaniline film (PANI/PSSA). An amine-end functionalized TTX-binding aptamer, 5′-NH2-AAAAATTTCACACGGGTGCCTCGGCTGTCC-3′ (NH2-Apt), was grafted via covalent glutaraldehyde (glu) cross-linking. The resulting aptasensor (C//PANI+/PSSA-glu-NH2-Apt) was interrogated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in sodium acetate buffer (NaOAc, pH 4.8) before and after 30 min incubation in standard TTX solutions. Both CV and EIS results confirmed that the binding of the analyte to the immobilized aptamer modulated the electrochemical properties of the sensor: particularly the charge transfer resistance (Rct) of the PANI+/PSSA film, which served as a signal reporter. Based on the Rct calibration curve of the TTX aptasensor, the values of the dynamic linear range (DLR), sensitivity and limit of detection (LOD) of the sensor were determined to be 0.23–1.07 ng·mL−1 TTX, 134.88 ± 11.42 Ω·ng·mL−1 and 0.199 ng·mL−1, respectively. Further studies are being planned to improve the DLR as well as to evaluate selectivity and matrix effects in real samples. PMID:26370994

  8. Electronegativity and doping in semiconductors

    KAUST Repository

    Schwingenschlögl, Udo

    2012-08-23

    Charge transfer predicted by standard models is at odds with Pauling’s electronegativities but can be reconciled by the introduction of a cluster formation model [Schwingenschlögl et al., Appl. Phys. Lett. 96, 242107 (2010)]. Using electronic structure calculations, we investigate p- and n-type doping in silicon and diamond in order to facilitate comparison as C has a higher electronegativity compared to Si. All doping conditions considered can be explained in the framework of the cluster formation model. The implications for codoping strategies and dopant-defect interactions are discussed.

  9. Mass spectrometric characterization of urinary metabolites of the selective androgen receptor modulator S-22 to identify potential targets for routine doping controls.

    Science.gov (United States)

    Thevis, Mario; Thomas, Andreas; Möller, Ines; Geyer, Hans; Dalton, James T; Schänzer, Wilhelm

    2011-08-15

    Drugs that promote anabolic processes with limited undesirable effects are of considerable therapeutic interest; some notable examples include those for the treatment of cancer cachexia and muscle-wasting diseases. Anabolic properties are not only therapeutically beneficial to critically ill and debilitated patients, but are also desirable to athletes seeking artificial enhancements in endurance, strength and accelerated recovery. The use of anabolic agents in the clinical setting is being reconsidered with the emergence of a new class of drugs referred to as SARMs (selective androgen receptor modulators). SARMs have the potential to complement or even replace anabolic androgenic steroidal use with the benefit of a reduction of the undesirable side effects associated with steroid administration alone. Arylpropionamide-based SARMs such as andarine (S-4) and S-22 have shown promising therapeutic properties and have attracted the interest of elite and amateur athletes despite the absence of clinical approval, and evidence for trafficking and misuse in sport has been obtained by doping control authorities. In this communication, the elucidation of urinary metabolites of the SARM drug candidate S-22 is compared with earlier in vitro metabolism studies. Following oral administration of illicit S-22, urine samples were collected after 62 and 135 h and analyzed for the active drug and its major metabolic products. Liquid chromatography interfaced with high-resolution/high-accuracy (tandem) mass spectrometry was used to identify and/or confirm the predicted target analytes for sports drug testing purposes. S-22 was detected in both specimens accompanied by its glucuronic acid conjugate. This was the B-ring hydroxylated derivative of S-22 plus the corresponding glucuronide (with the phase-II metabolites being the more abundant analytes). In addition, the samples collected 62 h post-administration also contained the phase-I metabolite hydroxylated at the methyl residue (C-20

  10. Ge-intercalated graphene: The origin of the p-type to n-type transition

    KAUST Repository

    Kaloni, Thaneshwor P.

    2012-09-01

    Recently huge interest has been focussed on Ge-intercalated graphene. In order to address the effect of Ge on the electronic structure, we study Ge-intercalated free-standing C 6 and C 8 bilayer graphene, bulk C 6Ge and C 8Ge, as well as Ge-intercalated graphene on a SiC(0001) substrate, by density functional theory. In the presence of SiC(0001), there are three ways to obtain n-type graphene: i) intercalation between C layers; ii) intercalation at the interface to the substrate in combination with Ge deposition on the surface; and iii) cluster intercalation. All other configurations under study result in p-type states irrespective of the Ge coverage. We explain the origin of the different doping states and establish the conditions under which a transition occurs. © Copyright EPLA, 2012.

  11. N-type thermoelectric performance of functionalized carbon nanotube-filled polymer composites.

    Directory of Open Access Journals (Sweden)

    Dallas D Freeman

    Full Text Available Carbon nanotubes (CNTs were functionalized with polyethyleneimine (PEI and made into composites with polyvinyl acetate (PVAc. CNTs were dispersed with different amounts of sodium dodecylbenzenesulfonate (SDBS prior to the PEI functionalization. The resulting samples exhibit air-stable n-type characteristics with electrical conductivities as great as 1500 S/m and thermopowers as large as -100 µV/K. Electrical conductivity and thermopower were strongly affected by CNT dispersion, improving the properties with better dispersion with high concentrations of SDBS. This improvement is believed to be due to the increase in the number of tubes that are evenly coated with PEI in a better-dispersed sample. Increasing the amount of PEI relative to the other constituents positively affects thermopower but not conductivity. Air exposure reduces both thermopower and conductivity presumably due to oxygen doping (which makes CNTs p-type, but stable values were reached within seven days following sample fabrication.

  12. Capacitance spectroscopy on n-type GaNAs/GaAs embedded quantum structure solar cells

    Science.gov (United States)

    Venter, Danielle; Bollmann, Joachim; Elborg, Martin; Botha, J. R.; Venter, André

    2018-04-01

    In this study, both deep level transient spectroscopy (DLTS) and admittance spectroscopy (AS) have been used to study the properties of electrically active deep level centers present in GaNAs/GaAs quantum wells (QWs) embedded in p-i-n solar cells. The structures were grown by molecular beam epitaxy (MBE). In particular, the electrical properties of samples with Si (n-type) doping of the QWs were investigated. DLTS revealed four deep level centers in the material, whereas only three were detected by AS. NextNano++ simulation software was used to model the sample band-diagrams to provide reasoning for the origin of the signals produced by both techniques.

  13. Air-stable n-type colloidal quantum dot solids

    KAUST Repository

    Ning, Zhijun

    2014-06-08

    Colloidal quantum dots (CQDs) offer promise in flexible electronics, light sensing and energy conversion. These applications rely on rectifying junctions that require the creation of high-quality CQD solids that are controllably n-type (electron-rich) or p-type (hole-rich). Unfortunately, n-type semiconductors made using soft matter are notoriously prone to oxidation within minutes of air exposure. Here we report high-performance, air-stable n-type CQD solids. Using density functional theory we identify inorganic passivants that bind strongly to the CQD surface and repel oxidative attack. A materials processing strategy that wards off strong protic attack by polar solvents enabled the synthesis of an air-stable n-type PbS CQD solid. This material was used to build an air-processed inverted quantum junction device, which shows the highest current density from any CQD solar cell and a solar power conversion efficiency as high as 8%. We also feature the n-type CQD solid in the rapid, sensitive, and specific detection of atmospheric NO2. This work paves the way for new families of electronic devices that leverage air-stable quantum-tuned materials. © 2014 Macmillan Publishers Limited. All rights reserved.

  14. n-Type Azaacenes Containing B←N Units.

    Science.gov (United States)

    Min, Yang; Dou, Chuandong; Tian, Hongkun; Geng, Yanhou; Liu, Jun; Wang, Lixiang

    2018-02-12

    We disclose a novel strategy to design n-type acenes through the introduction of boron-nitrogen coordination bonds (B←N). We synthesized two azaacenes composed of two B←N units and six/eight linearly annelated rings. The B←N unit significantly perturbed the electronic structures of the azaacenes: Unique LUMOs delocalized over the entire acene skeletons and decreased aromaticity of the B←N-adjacent rings. Most importantly, these B←N-containing azaacenes exhibited low-lying LUMO energy levels and high electron affinities, thus leading to n-type character. The solution-processed organic field-effect transistor based on one such azaacene exhibited unipolar n-type characteristics with an electron mobility of 0.21 cm 2  V -1  s -1 . © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Graded Doping for Enhanced Colloidal Quantum Dot Photovoltaics

    KAUST Repository

    Ning, Zhijun

    2013-02-05

    A novel approach to improving all-inorganic colloidal quantum dot (CQD) homojunction solar cells by engineering the doping spatial profile to produce a doping gradient within the n-type absorber is presented. The doping gradient greatly improves carrier collection and enhances the voltages attainable by the device, leading to a 1 power point power conversion efficiency (PCE) improvement over previous inorganic CQD solar cells. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Impact of dopant concentrations on emitter formation with spin on dopant source in n-type crystalline silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Singha, Bandana; Solanki, Chetan Singh [Department of Energy Science and Technology, Indian Institute of Technology, Bombay Mumbai-400076, Maharashtra (India)

    2016-05-06

    Use of a suitable dopant source for emitter formation is an essential requirement in n-type crystalline silicon solar cells. Boron spin on dopant source, used as alternative to mostly used BBr{sub 3} liquid source, can yield an emitter with less diffusion induced defects under controlled conditions. Different concentrations of commercially available spin on dopant source is used and optimized in this work for sheet resistance values of the emitter ranging from 30 Ω/□ to 70 Ω/□ with emitter doping concentrations suitable for ohmic contacts. The dopant concentrations diluted with different ratios improves the carrier lifetime and thus improves the emitter performance. Hence use of suitable dopant source is essential in forming emitters in n-type crystalline silicon solar cells.

  17. Validation of a GC/MS method for the detection of two quinolinone-derived selective androgen receptor modulators in doping control analysis.

    Science.gov (United States)

    Gerace, E; Salomone, A; Fasano, F; Costa, R; Boschi, D; Di Stilo, A; Vincenti, M

    2011-04-01

    Selective androgen receptor modulators (SARMs) represent an emerging class of drugs likely to be abused in sport. For clinical applications, these substances provide a promising alternative to testosterone-replacement therapies and their advantages include oral bioavailability, androgen receptor specificity, tissue selectivity, and the absence of steroid-related side effects. Although not yet commercially available, since January 2008 SARMs have been included on the prohibited list issued yearly by the World Anti-Doping Agency (WADA), so control laboratories need to update their procedures to detect either the parent drugs or their metabolites. Within this context, two quinolinone SARM models were synthesized and automatically characterized to update the existing routine screening procedures. The conditions for the new target analytes are compatible with the existing laboratory protocols used for both in-competition and out-of-competition controls and can be included in them. Validation parameters according to ISO 17025 and WADA guidelines were successfully determined. For analytical determinations, spiked urine samples were hydrolyzed and extracted at pH 9.6 with 10 mL of tert-butyl methyl ether. Then, the analytes were subsequently converted into trimethylsilyl derivatives and detected by gas chromatography-mass spectrometry. The absence of interferents, together with excellent repeatability of both retention times and the relative abundances of diagnostic ions, allowed proper identification of all SARM analytes. The analytes' quantification was linear up to 500 ng/mL and precision criteria were satisfied (coefficient of variation less than 25% at 10 ng/mL). The limits of detection were 1 ng/mL for both SARMs, whereas recovery values were between 95.5 and 99.3%. The validated method can be efficiently used for urine screening of the 2-quinolinone-derived SARMs tested.

  18. n-Type phosphorus-doped nanocrystalline diamond: electrochemical and in situ Raman spectroelectrochemical study

    Czech Academy of Sciences Publication Activity Database

    Vlčková Živcová, Zuzana; Frank, Otakar; Drijkoningen, S.; Haenen, K.; Mortet, Vincent; Kavan, Ladislav

    2016-01-01

    Roč. 6, č. 56 (2016), s. 51387-51393 ISSN 2046-2069 R&D Projects: GA ČR GA13-31783S Grant - others:AV ČR(CZ) G.0456.1 Institutional support: RVO:61388955 ; RVO:68378271 Keywords : Amorphous films * Cyclic voltammetry * Diamond films Subject RIV: CG - Electrochemistry; BM - Solid Matter Physics ; Magnetism (FZU-D) Impact factor: 3.108, year: 2016

  19. Microwave Faraday effect in n-type germanium

    NARCIS (Netherlands)

    Bouwknegt, A.; Volger, J.

    The Faraday rotation, ellipticity and the accompanying magneto-absorption were determined from measurements with the crossed wave guide coupler device, at room temperature, at 24.9 GHz. The complex conductivity tensor elements of n-type germanium were deduced from this complete Faraday effect, with

  20. Electric transport in N-type Fe2O3

    NARCIS (Netherlands)

    Acket, G.A.; Volger, J.

    Resistivity, Seebeck-coefficient, Hall-coefficient and magneto-resistance of n-type single crystal ferric oxide (hematite), containing Sn4+ as an impurity, are reported. The resistivity does not show important anisotropy. The Hall- and magneto-resistance effects are probably related to the parasitic

  1. Blocking contacts for N-type cadmium zinc telluride

    Science.gov (United States)

    Stahle, Carl M. (Inventor); Parker, Bradford H. (Inventor); Babu, Sachidananda R. (Inventor)

    2012-01-01

    A process for applying blocking contacts on an n-type CdZnTe specimen includes cleaning the CdZnTe specimen; etching the CdZnTe specimen; chemically surface treating the CdZnTe specimen; and depositing blocking metal on at least one of a cathode surface and an anode surface of the CdZnTe specimen.

  2. Synthesis and electrical characterization of intrinsic and in situ doped Si nanowires using a novel precursor

    Directory of Open Access Journals (Sweden)

    Wolfgang Molnar

    2012-07-01

    Full Text Available Perchlorinated polysilanes were synthesized by polymerization of tetrachlorosilane under cold plasma conditions with hydrogen as a reducing agent. Subsequent selective cleavage of the resulting polymer yielded oligochlorosilanes SinCl2n+2 (n = 2, 3 from which the octachlorotrisilane (n = 3, Cl8Si3, OCTS was used as a novel precursor for the synthesis of single-crystalline Si nanowires (NW by the well-established vapor–liquid–solid (VLS mechanism. By adding doping agents, specifically BBr3 and PCl3, we achieved highly p- and n-type doped Si-NWs by means of atmospheric-pressure chemical vapor deposition (APCVD. These as grown NWs were investigated by means of scanning electron microscopy (SEM and transmission electron microscopy (TEM, as well as electrical measurements of the NWs integrated in four-terminal and back-gated MOSFET modules. The intrinsic NWs appeared to be highly crystalline, with a preferred growth direction of [111] and a specific resistivity of ρ = 6 kΩ·cm. The doped NWs appeared to be [112] oriented with a specific resistivity of ρ = 198 mΩ·cm for p-type Si-NWs and ρ = 2.7 mΩ·cm for n-doped Si-NWs, revealing excellent dopant activation.

  3. Visible light-induced electronic structure modulation of Nb- and Ta-doped α-Fe2O3 nanorods for effective photoelectrochemical water splitting

    Science.gov (United States)

    Chang, Han-Wei; Fu, Yanming; Lee, Wan-Yi; Lu, Ying-Rui; Huang, Yu-Cheng; Chen, Jeng-Lung; Chen, Chi-Liang; Chou, Wu Ching; Chen, Jin-Ming; Lee, Jyh-Fu; Shen, Shaohua; Dong, Chung-Li

    2018-02-01

    The photoelectrochemical (PEC) water splitting activity of Nb and Ta-doped hematite (α-Fe2O3) nanorods was investigated with reference to electronic structures by in situ synchrotron x-ray absorption spectroscopy (XAS). Current density-potential measurements demonstrate that the PEC activity of α-Fe2O3 nanorods depends strongly on the species and concentrations of dopants. The doping of α-Fe2O3 nanorods with a low level of Nb or Ta can improve their electrical conductivity and thereby facilitate charge transport and reduced electron-hole recombination therein. The photoconversion effects of Nb and Ta-doped α-Fe2O3 by in situ XAS in the dark and under illumination revealed opposite evolutions of the spectral intensities of the Fe L-edge and Nb/Ta L-edge, indicating that charge transfer and a conduction pathway are involved in the photoconversion. Analytic in situ XAS results reveal that the α-Fe2O3 that is doped with a low level of Nb has a greater photoconversion efficiency than that doped with Ta because Nb sites are more active than Ta sites in α-Fe2O3. The correlation between PEC activity and the electronic structure of Nb/Ta-doped α-Fe2O3 is examined in detail using in situ XAS and helps to elucidate the mechanism of PEC water splitting in terms of the electronic structure.

  4. Characterisation of the hole-acoustic phonon interaction in modulation doped Si/Si1-xGex (0.085<=x<=0.28) heterostructures

    International Nuclear Information System (INIS)

    Braithwaite, G.

    1999-06-01

    The work presented in this Thesis describes the author's experimental investigation of the two dimensional hole gas - acoustic phonon interaction in non-inverted modulation doped strained Si 1-x Ge x heterostructures. This covers a range of Ge content (0.085≤x≤0.28) and carrier temperature range 0.35K ≤ T C ≤ 4.2K. Using the technique of carrier temperature mapping, the present author has measured the energy loss rate characteristics of the two dimensional hole gas as a function of carrier temperature. The carrier temperature thermometers used are, the zero magnetic field resistivity, the low magnetic field magnetoresistance, and, the thermal damping of the amplitude of the Shubnikov - de Haas oscillations. The present author has also used an exact numerical calculation to determine the theoretical energy loss rates over the range of Ge contents and found consistently that the deformation potential interaction is best described as being weakly screened. Also, it is found, that by including an additional piezoelectric-like acoustic phonon coupled interaction, it is possible to achieve improved agreement between the theoretical energy loss rates and the experimental data over the range of carrier temperatures 0.35K≤T C ≤4.2K. The present author suggests that a possible source of this interaction is linked to the correlated interface roughness that may be expected at the upper Si/Si 1-x Ge x heterointerface. From analysis of the low magnetic field magnetoresistance measurements, the author has determined the carrier temperature dependence of the hole-hole scattering rate. It will be shown that by considering the fully self consistent nature of carrier-carrier scattering in the weak localisation regime ('dirty limit'), and by including the effect of carrier-carrier scattering in the 'clean limit', it is possible to calculate the dephasing rates for this system and obtain agreement with the measured experimental data to within an accuracy of ±10%. This is a

  5. Dual-donor (Zn(i) and V(O)) mediated ferromagnetism in copper-doped ZnO micron-scale polycrystalline films: a thermally driven defect modulation process.

    Science.gov (United States)

    Hu, Liang; Huang, Jun; He, Haiping; Zhu, Liping; Liu, Shijiang; Jin, Yizheng; Sun, Luwei; Ye, Zhizhen

    2013-05-07

    The paper reports robust ferromagnetic Cu-doped ZnO micron-scale polycrystalline films via spin-coating using high-quality doped nanocrystals. A reliable magnetic response is observed in the 900 °C vacuum annealed film without any ferromagnetic contribution from other sources. Post-annealing treatment in terms of atmosphere and temperature can control the proportion of oxygen vacancies (V(O)) and zinc interstitials (Zn(i)) defects and further help to precisely regulate defect-related ferromagnetic behavior. Complex charge transfer processes derived from dual-donor (Zn(i) and V(O)) to Cu acceptor are revealed by photoluminescence (PL) and electron paramagnetic resonance (EPR) spectra. Based on the above, specific charge transfer (CT)-type Stoner splitting and indirect double-exchange mechanisms are proposed to understand the ferromagnetic origin. The improvable FM performance and annealing-specific modulation further indicate that a thermal driven process can delicately tailor the magnetic property of the transition metal ion-doped ZnO system.

  6. Airplane dopes and doping

    Science.gov (United States)

    Smith, W H

    1919-01-01

    Cellulose acetate and cellulose nitrate are the important constituents of airplane dopes in use at the present time, but planes were treated with other materials in the experimental stages of flying. The above compounds belong to the class of colloids and are of value because they produce a shrinking action on the fabric when drying out of solution, rendering it drum tight. Other colloids possessing the same property have been proposed and tried. In the first stages of the development of dope, however, shrinkage was not considered. The fabric was treated merely to render it waterproof. The first airplanes constructed were covered with cotton fabric stretched as tightly as possible over the winds, fuselage, etc., and flying was possible only in fine weather. The necessity of an airplane which would fly under all weather conditions at once became apparent. Then followed experiments with rubberized fabrics, fabrics treated with glue rendered insoluble by formaldehyde or bichromate, fabrics treated with drying and nondrying oils, shellac, casein, etc. It was found that fabrics treated as above lost their tension in damp weather, and the oil from the motor penetrated the proofing material and weakened the fabric. For the most part the film of material lacked durability. Cellulose nitrate lacquers, however were found to be more satisfactory under varying weather conditions, added less weight to the planes, and were easily applied. On the other hand, they were highly inflammable, and oil from the motor penetrated the film of cellulose nitrate, causing the tension of the fabric to be relaxed.

  7. Road to Grid Parity through Deployment of Low-Cost 21.5% N-Type Si Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Velundur, Vijay [Suniva, Norcross, GA (United States)

    2017-04-19

    This project seeks to develop and deploy differentiated 21.5% efficient n-type Si solar cells while reaching the SunShot module cost goal of ≤ $0.50/W. This objective hinges on development of enabling low cost technologies that simplify the manufacturing process and reduce overall processing costs. These comprise of (1) Boron emitter formation and passivation; (2) Simplified processing process for emitter and BSF layers; and (3) Advanced metallization for the front and back contacts.

  8. Cu doped AlSb polycrystalline thin films

    International Nuclear Information System (INIS)

    Wu Lili; Jin Shuo; Zeng Guanggen; Zhang Jingquan; Li Wei; Feng Lianghuan; Li Bing; Wang Wenwu

    2013-01-01

    Cu-doped AlSb polycrystalline films were grown on quartz glass by magnetron co-sputtering. The structural, morphological and electrical properties of the films were studied. The incorporation of copper atoms can result in the increase of lattice constants, and annealing is helpful to eliminate this deformation. Cu-doped AlSb films exhibit weak n-type conductivity. The results show that the doping effect has a close relationship with the annealing process, meaning that the position of Cu atom in AlSb polycrystalline films might influence the doping effect. (semiconductor materials)

  9. Label-free room-temperature phosphorescence turn-on detection of tiopronin based on Cu{sup 2+}-modulated homocysteine-capped manganese doped zinc sulfide quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Yan; Fan, Zhefeng, E-mail: crush_bc@163.com

    2015-04-15

    A label-free turn-on room-temperature phosphorescence (RTP) sensor for tiopronin based on Cu{sup 2+}-modulated homocysteine (Hcy)-capped Mn-doped ZnS quantum dots (QDs) was described in this paper. The RTP of Hcy-capped Mn-doped ZnS QDs can be effectively quenched by Cu{sup 2+} due to the binding of Cu{sup 2+} to the Hcy on the surface of the QDs and the electron transfer generated from the photoexcited QDs to Cu{sup 2+}. The high affinity of tiopronin to Cu{sup 2+} enables the dissociation of the ion from the surface of the QDs, thereby forming a stable complex with tiopronin in the solution, and recovering the RTP of the QDs. The Cu{sup 2+}-induced RTP quenching and subsequent tiopronin-induced RTP recovery for MPA-capped ZnS QDs provide a solid basis for the present RTP sensor based on QDs for the detection of tiopronin. The detection limit for tiopronin is 0.18 ng mL{sup −1}, the relative standard deviations is 1.9%, and the recovery of urine and serum samples with tiopronin addition range from 96% to 106% under optimal conditions. The proposed method was successfully applied to biological fluids and obtained satisfactory results. - Highlights: • The high water-solubility Mn-doped-QDs with good RTP property was synthesized. • The RTP intensity of the QDs could be effectively quenched by Cu{sup 2+} ions. • Cu{sup 2+} ions were selectively separated from the QDs by tiopronin. • The RTP of the Cu{sup 2+}-modulated QDs was restored by tiopronin. • The tiopronin sensor was applied to biological fluids with satisfactory results.

  10. Improving the radiation hardness properties of silicon detectors using oxygenated n-type and p-type silicon

    CERN Document Server

    Casse, G L; Hanlon, M

    2000-01-01

    The degradation of the electrical properties of silicon detectors exposed to 24 GeV/c protons were studied using pad diodes made from different silicon materials. Standard high-grade p-type and n-type substrates and oxygenated n-type substrates have been used. The diodes were studied in terms of reverse current (I/sub r/) and full depletion voltage (V/sub fd/) as a function of fluence. The oxygenated devices from different suppliers with a variety of starting materials and techniques, all show a consistent improvement of the degradation rate of V/sub fd/ and CCE compared to un- oxygenated substrate devices. Radiation damage of n-type detectors introduces stable defects acting as effective p-type doping and leads to the change of the conductivity type of the silicon bulk (type inversion) at a neutron equivalent fluence of a few 10/sup 13/ cm/sup -2/. The diode junction after inversion migrates from the original side to the back plane of the detector. The migration of the junction is avoided using silicon detec...

  11. Predictable quantum efficient detector based on n-type silicon photodiodes

    Science.gov (United States)

    Dönsberg, Timo; Manoocheri, Farshid; Sildoja, Meelis; Juntunen, Mikko; Savin, Hele; Tuovinen, Esa; Ronkainen, Hannu; Prunnila, Mika; Merimaa, Mikko; Tang, Chi Kwong; Gran, Jarle; Müller, Ingmar; Werner, Lutz; Rougié, Bernard; Pons, Alicia; Smîd, Marek; Gál, Péter; Lolli, Lapo; Brida, Giorgio; Rastello, Maria Luisa; Ikonen, Erkki

    2017-12-01

    The predictable quantum efficient detector (PQED) consists of two custom-made induced junction photodiodes that are mounted in a wedged trap configuration for the reduction of reflectance losses. Until now, all manufactured PQED photodiodes have been based on a structure where a SiO2 layer is thermally grown on top of p-type silicon substrate. In this paper, we present the design, manufacturing, modelling and characterization of a new type of PQED, where the photodiodes have an Al2O3 layer on top of n-type silicon substrate. Atomic layer deposition is used to deposit the layer to the desired thickness. Two sets of photodiodes with varying oxide thicknesses and substrate doping concentrations were fabricated. In order to predict recombination losses of charge carriers, a 3D model of the photodiode was built into Cogenda Genius semiconductor simulation software. It is important to note that a novel experimental method was developed to obtain values for the 3D model parameters. This makes the prediction of the PQED responsivity a completely autonomous process. Detectors were characterized for temperature dependence of dark current, spatial uniformity of responsivity, reflectance, linearity and absolute responsivity at the wavelengths of 488 nm and 532 nm. For both sets of photodiodes, the modelled and measured responsivities were generally in agreement within the measurement and modelling uncertainties of around 100 parts per million (ppm). There is, however, an indication that the modelled internal quantum deficiency may be underestimated by a similar amount. Moreover, the responsivities of the detectors were spatially uniform within 30 ppm peak-to-peak variation. The results obtained in this research indicate that the n-type induced junction photodiode is a very promising alternative to the existing p-type detectors, and thus give additional credibility to the concept of modelled quantum detector serving as a primary standard. Furthermore, the manufacturing of

  12. Spin injection in n-type resonant tunneling diodes.

    Science.gov (United States)

    Orsi Gordo, Vanessa; Herval, Leonilson Ks; Galeti, Helder Va; Gobato, Yara Galvão; Brasil, Maria Jsp; Marques, Gilmar E; Henini, Mohamed; Airey, Robert J

    2012-10-25

    We have studied the polarized resolved photoluminescence of n-type GaAs/AlAs/GaAlAs resonant tunneling diodes under magnetic field parallel to the tunnel current. Under resonant tunneling conditions, we have observed two emission lines attributed to neutral (X) and negatively charged excitons (X-). We have observed a voltage-controlled circular polarization degree from the quantum well emission for both lines, with values up to -88% at 15 T at low voltages which are ascribed to an efficient spin injection from the 2D gases formed at the accumulation layers.

  13. Nitrogen-Doped Graphene Sheets Grown by Chemical Vapor Deposition: Synthesis and Influence of Nitrogen Impurities on Carrier Transport

    OpenAIRE

    Lu, Yu-Fen; Lo, Shun-Tsung; Lin, Jheng-Cyuan; Zhang, Wenjing; Lu, Jing-Yu; Liu, Fan-Hung; Tseng, Chuan-Ming; Lee, Yi-Hsien; Liang, Chi-Te; Li, Lain-Jong

    2013-01-01

    A significant advance toward achieving practical applications of graphene as a two-dimensional material in nanoelectronics would be provided by successful synthesis of both n-type and p-type doped graphene. However reliable doping and a thorough understanding of carrier transport in the presence of charged impurities governed by ionized donors or acceptors in the graphene lattice are still lacking. Here we report experimental realization of few-layer nitrogen-doped (N-doped) graphene sheets b...

  14. Lifetime degradation of n-type Czochralski silicon after hydrogenation

    Science.gov (United States)

    Vaqueiro-Contreras, M.; Markevich, V. P.; Mullins, J.; Halsall, M. P.; Murin, L. I.; Falster, R.; Binns, J.; Coutinho, J.; Peaker, A. R.

    2018-04-01

    Hydrogen plays an important role in the passivation of interface states in silicon-based metal-oxide semiconductor technologies and passivation of surface and interface states in solar silicon. We have shown recently [Vaqueiro-Contreras et al., Phys. Status Solidi RRL 11, 1700133 (2017)] that hydrogenation of n-type silicon slices containing relatively large concentrations of carbon and oxygen impurity atoms {[Cs] ≥ 1 × 1016 cm-3 and [Oi] ≥ 1017 cm-3} can produce a family of C-O-H defects, which act as powerful recombination centres reducing the minority carrier lifetime. In this work, evidence of the silicon's lifetime deterioration after hydrogen injection from SiNx coating, which is widely used in solar cell manufacturing, has been obtained from microwave photoconductance decay measurements. We have characterised the hydrogenation induced deep level defects in n-type Czochralski-grown Si samples through a series of deep level transient spectroscopy (DLTS), minority carrier transient spectroscopy (MCTS), and high-resolution Laplace DLTS/MCTS measurements. It has been found that along with the hydrogen-related hole traps, H1 and H2, in the lower half of the gap reported by us previously, hydrogenation gives rise to two electron traps, E1 and E2, in the upper half of the gap. The activation energies for electron emission from the E1 and E2 trap levels have been determined as 0.12, and 0.14 eV, respectively. We argue that the E1/H1 and E2/H2 pairs of electron/hole traps are related to two energy levels of two complexes, each incorporating carbon, oxygen, and hydrogen atoms. Our results show that the detrimental effect of the C-O-H defects on the minority carrier lifetime in n-type Si:O + C materials can be very significant, and the carbon concentration in Czochralski-grown silicon is a key parameter in the formation of the recombination centers.

  15. Control of conduction type in ferromagnetic (Zn,Sn,Mn)As2 thin films by changing Mn content and effect of annealing on thin films with n-type conduction

    Science.gov (United States)

    Minamizawa, Yuto; Kitazawa, Tomohiro; Hidaka, Shiro; Toyota, Hideyuki; Nakamura, Shin-ichi; Uchitomi, Naotaka

    2018-04-01

    The conduction type in (Zn,Sn,Mn)As2 thin films grown by molecular beam epitaxy (MBE) on InP substrates was found to be controllable from p-type to n-type as a function of Mn content. n-type (Zn,Sn,Mn)As2 thin films were obtained by Mn doping of more than approximately 11 cat.%. It is likely that Mn interstitials (MnI) incorporated by excess Mn doping are located at tetrahedral hollow spaces surrounded by Zn and Sn cation atoms and four As atoms, which are expected to act as donors in (Zn,Sn,Mn)As2, resulting in n-type conduction. The effect of annealing on the structural, electrical and magnetic properties of n-type (Zn,Sn,Mn)As2 thin films was investigated as functions of annealing temperature and time. It was revealed that even if the annealing temperature is considerably higher than the growth temperature of 320 °C, the magnetic properties of the thin films remain stable. This suggests that a MnI complex surrounded by Zn and Sn atoms is thermally stable during high-temperature annealing. The n-type (Zn,Sn,Mn)As2 thin films may be suitable for application as n-type spin-polarized injectors.

  16. Rhenium-doped MoS2 films

    Science.gov (United States)

    Hallam, Toby; Monaghan, Scott; Gity, Farzan; Ansari, Lida; Schmidt, Michael; Downing, Clive; Cullen, Conor P.; Nicolosi, Valeria; Hurley, Paul K.; Duesberg, Georg S.

    2017-11-01

    Tailoring the electrical properties of transition metal dichalcogenides by doping is one of the biggest challenges for the application of 2D materials in future electronic devices. Here, we report on a straightforward approach to the n-type doping of molybdenum disulfide (MoS2) films with rhenium (Re). High-Resolution Scanning Transmission Electron Microscopy and Energy-Dispersive X-ray spectroscopy are used to identify Re in interstitial and lattice sites of the MoS2 structure. Hall-effect measurements confirm the electron donating influence of Re in MoS2, while the nominally undoped films exhibit a net p-type doping. Density functional theory (DFT) modelling indicates that Re on Mo sites is the origin of the n-type doping, whereas S-vacancies have a p-type nature, providing an explanation for the p-type behaviour of nominally undoped MoS2 films.

  17. Liquid chromatography-high resolution/ high accuracy (tandem) mass spectrometry-based identification of in vivo generated metabolites of the selective androgen receptor modulator ACP-105 for doping control purposes.

    Science.gov (United States)

    Thevis, Mario; Thomas, Andreas; Piper, Thomas; Krug, Oliver; Delahaut, Philippe; Schänzer, Wilhelm

    2014-01-01

    Selective androgen receptor modulators (SARMs) represent an emerging class of therapeutics which have been prohibited in sport as anabolic agents according to the regulations of the World Anti-Doping Agency (WADA) since 2008. Within the past three years, numerous adverse analytical findings with SARMs in routine doping control samples have been reported despite missing clinical approval of these substances. Hence, preventive doping research concerning the metabolism and elimination of new therapeutic entities of the class of SARMs are vital for efficient and timely sports drug testing programs as banned compounds are most efficiently screened when viable targets (for example, characteristic metabolites) are identified. In the present study, the metabolism of ACP-105, a novel SARM drug candidate, was studied in vivo in rats. Following oral administration, urine samples were collected over a period of seven days and analyzed for metabolic products by Liquid chromatography-high resolution/high accuracy (tandem) mass spectrometry. Samples were subjected to enzymatic hydrolysis prior to liquid-liquid extraction and a total of seven major phase-I metabolites were detected, three of which were attributed to monohydroxylated and four to bishydroxylated ACP-105. The hydroxylation sites were assigned by means of diagnostic product ions and respective dissociation pathways of the analytes following positive or negative ionization and collisional activation as well as selective chemical derivatization. The identified metabolites were used as target compounds to investigate their traceability in a rat elimination urine samples study and monohydroxylated and bishydroxylated species were detectable for up to four and six days post-administration, respectively.

  18. Electronic Modulation of Electrocatalytically Active Center of Cu7S4 Nanodisks by Cobalt-Doping for Highly Efficient Oxygen Evolution Reaction.

    Science.gov (United States)

    Li, Qun; Wang, Xianfu; Tang, Kai; Wang, Mengfan; Wang, Chao; Yan, Chenglin

    2017-12-26

    Cu-based electrocatalysts have seldom been studied for water oxidation because of their inferior activity and poor stability regardless of their low cost and environmentally benign nature. Therefore, exploring an efficient way to improve the activity of Cu-based electrocatalysts is very important for their practical application. Modifying electronic structure of the electrocatalytically active center of electrocatalysts by metal doping to favor the electron transfer between catalyst active sites and electrode is an important approach to optimize hydrogen and oxygen species adsorption energy, thus leading to the enhanced intrinsic electrocatalytic activity. Herein, Co-doped Cu 7 S 4 nanodisks were synthesized and investigated as highly efficient electrocatalyst for oxygen evolution reaction (OER) due to the optimized electronic structure of the active center. Density-functional theory (DFT) calculations reveal that Co-engineered Cu 7 S 4 could accelerate electron transfer between Co and Cu sites, thus decrease the energy barriers of intermediates and products during OER, which are crucial for enhanced catalytic properties. As expected, Co-engineered Cu 7 S 4 nanodisks exhibit a low overpotential of 270 mV to achieve current density of 10 mA cm -2 as well as decreased Tafel slope and enhanced turnover frequencies as compared to bare Cu 7 S 4 . This discovery not only provides low-cost and efficient Cu-based electrocatalyst by Co doping, but also exhibits an in-depth insight into the mechanism of the enhanced OER properties.

  19. Real-time polarization mode dispersion monitoring system for a multiple-erbium-doped fiber amplifier, dense wavelength division multiplexing optical fiber transmission by amplified spontaneous emission modulation and acousto-optic tunable fiber scanning techniques.

    Science.gov (United States)

    Tseng, Bao-Jang; Tarn, Chen-Wen

    2009-03-01

    Without interruption or affecting the transmission of ordinary payload channels, we propose a real time polarization mode dispersion (PMD) monitoring system for long-haul, multiple erbium-doped fiber amplifier (EDFA), dense wavelength division multiplexing (DWDM) optical fiber transmission using modulated amplified spontaneous emission (ASE) of one of the EDFAs as the supervisory (SV) signal source. An acousto-optic tunable filter (AOTF) at the receiver side is adopted to scan the spectrum of the transmitted ASE SV signal. Using the fixed-analyzer method, PMDs of different wavelength bands that range from 1545 to 1580 nm of a DWDM fiber-optic communication system can be found by adaptively changing the radio frequency of the AOTF. The resolution and the measuring range of the proposed monitoring system can be significantly improved by cascading the AOTFs at the receiver side.

  20. Characterisation of the hole-acoustic phonon interaction in modulation doped Si/Si sub 1 sub - sub x Ge sub x (0.085<=x<=0.28) heterostructures

    CERN Document Server

    Braithwaite, G

    1999-01-01

    magnetoresistance measurements, the has determined the carrier temperature dependence of the hole-hole scattering rate. It will be shown that by considering the fully self consistent nature of carrier-carrier scattering in the weak localisation regime ('dirty limit'), and by including the effect of carrier-carrier scattering in the 'clean limit', it is possible to calculate the dephasing rates for this system and obtain agreement with the measured experimental data to within an accuracy of +-10%. This is a significant improvement on some of the previous calculations for other 2D systems that have been observed in the literature. This Thesis will also report the preliminary results and analysis of pulsed high electric field measurements where the two dimensional hole gas is expected to interact with optical phonons. The work presented in this Thesis describes the experimental investigation of the two dimensional hole gas - acoustic phonon interaction in non-inverted modulation doped strained Si sub 1 sub - sub...

  1. Epitaxy-stabilized n-type superconducting cuprates

    CERN Document Server

    Naito, M; Tsukada, A

    2002-01-01

    We report the growth of n-type superconducting T'-(La,Ce) sub 2 CuO sub 4 and infinite-layer (IL) (Sr,La)CuO sub 2 thin films by means of molecular beam epitaxy (MBE). The bulk synthesis of T'-(La,Ce) sub 2 CuO sub 4 and IL-(Sr,La)CuO sub 2 requires complicated techniques: synthesis at low temperatures below 600 deg C for the former and at high pressures above 3 GPa for the latter. This makes it difficult to grow bulk single crystals. We have found, however, that high-quality single-crystalline films of both compounds can be rather easily prepared by thin-film processes. Single-phase T'-(La,Ce) sub 2 CuO sub 4 films can be obtained for a wide range of x (0.0 <= x <= approx 0.4). The best T sub c sup e sup n sup d is over 30 K, which is the highest in the T' family. For IL-(Sr,La)CuO sub 2 , by using KTaO sub 3 substrates, high T sub c sup e sup n sup d over 39 K and also metallic resistivity were achieved for the first time to our knowledge. We describe the key parameters in the growth and the propertie...

  2. Performance and stress analysis of oxide thermoelectric module architecture designed for maximum power output

    DEFF Research Database (Denmark)

    Wijesekara, Waruna; Rosendahl, Lasse; Wu, NingYu

    Oxide thermoelectric materials are promising candidates for energy harvesting from mid to high temperature heat sources. In this work, the oxide thermoelectric materials and the final design of the high temperature thermoelectric module were developed. Also, prototypes of oxide thermoelectric gen...... and simulation results were validated. In addition, the thermal stress and the thermal expansion of the thermoelectric uni-couple were studied in this work....... generator were built for high temperature applications. This paper specifically discusses the thermoelectric module design and the prototype validations of the design. Here p type calcium cobalt oxide and n type aluminum doped ZnO were developed as the oxide thermoelectric materials. Hot side and cold side...

  3. Highly n-Type Titanium Oxide as an Electronically Active Support for Platinum in the Catalytic Oxidation of Carbon Monoxide

    KAUST Repository

    Baker, L. Robert

    2011-08-18

    The role of the oxide-metal interface in determining the activity and selectivity of chemical reactions catalyzed by metal particles on an oxide support is an important topic in science and industry. A proposed mechanism for this strong metal-support interaction is electronic activation of surface adsorbates by charge carriers. Motivated by the goal of using electronic activation to drive nonthermal chemistry, we investigated the ability of the oxide support to mediate charge transfer. We report an approximately 2-fold increase in the turnover rate of catalytic carbon monoxide oxidation on platinum nanoparticles supported on stoichiometric titanium dioxide (TiO2) when the TiO2 is made highly n-type by fluorine (F) doping. However, for nonstoichiometric titanium oxide (TiOX<2) the effect of F on the turnover rate is negligible. Studies of the titanium oxide electronic structure show that the energy of free electrons in the oxide determines the rate of reaction. These results suggest that highly n-type TiO2 electronically activates adsorbed oxygen (O) by electron spillover to form an active O- intermediate. © 2011 American Chemical Society.

  4. Structural studies of n-type nc-Si-QD thin films for nc-Si solar cells

    Science.gov (United States)

    Das, Debajyoti; Kar, Debjit

    2017-12-01

    A wide optical gap nanocrystalline silicon (nc-Si) dielectric material is a basic requirement at the n-type window layer of nc-Si solar cells in thin film n-i-p structure on glass substrates. Taking advantage of the high atomic-H density inherent to the planar inductively coupled low-pressure (SiH4 + CH4)-plasma, development of an analogous material in P-doped nc-Si-QD/a-SiC:H network has been tried. Incorporation of C in the Si-network extracted from the CH4 widens the optical band gap; however, at enhanced PH3-dilution of the plasma spontaneous miniaturization of the nc-Si-QDs below the dimension of Bohr radius (∼4.5 nm) further enhances the band gap by virtue of the quantum size effect. At increased flow rate of PH3, dopant induced continuous amorphization of the intrinsic crystalline network is counterbalanced by the further crystallization promoted by the supplementary atomic-H extracted from PH3 (1% in H2) in the plasma, eventually holding a moderately high degree of crystallinity. The n-type wide band gap (∼1.93 eV) window layer with nc-Si-QDs in adequate volume fraction (∼52%) could furthermore be instrumental as an effective seed layer for advancing sequential crystallization in the i-layer of nc-Si solar cells with n-i-p structure in superstrate configuration.

  5. Thermoelectric Properties Prediction of n-Type Mg2Si1- x Sn x Compounds by First Principles Calculation

    Science.gov (United States)

    Li, Xin; Li, Shuangming; Feng, Songke; Zhong, Hong

    2018-02-01

    A comprehensive analysis has been made of the n-type Mg2Si1 - x Sn x (0.25 ≤ x ≤ 0.75) compounds by the first principles calculation method. The calculated band structures in n-type Mg2Si1 - x Sn x show the conduction band convergence directly. This convergence in energy at x = 0.625 can enhance the Seebeck coefficient of the solid solution in comparison with other Sn contents. The Seebeck coefficient of Mg2Si0.375Sn0.625 could reach - 246 μV K-1 at the optimal doping density of 3 × 1020 cm-3. The enhancement of the Seebeck coefficient in the Mg2Si0.375Sn0.625 alloy results in a higher power factor of 6.2 mW m-1 K-2 at T = 550 K, and the predicted figure of merit is 1.53 at T = 700 K. Additionally, the ZT values can be maintained larger than 1.4 in a wide temperature range from 550 K to 800 K.

  6. Naphthalene Diimide Based n-Type Conjugated Polymers as Efficient Cathode Interfacial Materials for Polymer and Perovskite Solar Cells.

    Science.gov (United States)

    Jia, Tao; Sun, Chen; Xu, Rongguo; Chen, Zhiming; Yin, Qingwu; Jin, Yaocheng; Yip, Hin-Lap; Huang, Fei; Cao, Yong

    2017-10-18

    A series of naphthalene diimide (NDI) based n-type conjugated polymers with amino-functionalized side groups and backbones were synthesized and used as cathode interlayers (CILs) in polymer and perovskite solar cells. Because of controllable amine side groups, all the resulting polymers exhibited distinct electronic properties such as oxidation potential of side chains, charge carrier mobilities, self-doping behaviors, and interfacial dipoles. The influences of the chemical variation of amine groups on the cathode interfacial effects were further investigated in both polymer and perovskite solar cells. We found that the decreased electron-donating property and enhanced steric hindrance of amine side groups substantially weaken the capacities of altering the work function of the cathode and trap passivation of the perovskite film, which induced ineffective interfacial modifications and declining device performance. Moreover, with further improvement of the backbone design through the incorporation of a rigid acetylene spacer, the resulting polymers substantially exhibited an enhanced electron-transporting property. Upon use as CILs, high power conversion efficiencies (PCEs) of 10.1% and 15.2% were, respectively, achieved in polymer and perovskite solar cells. Importantly, these newly developed n-type polymers were allowed to be processed over a broad thickness range of CILs in photovoltaic devices, and a prominent PCE of over 8% for polymer solar cells and 13.5% for perovskite solar cells can be achieved with the thick interlayers over 100 nm, which is beneficial for roll-to-roll coating processes. Our findings contribute toward a better understanding of the structure-performance relationship between CIL material design and solar cell performance, and provide important insights and guidelines for the design of high-performance n-type CIL materials for organic and perovskite optoelectronic devices.

  7. Impurity strength and impurity domain modulated frequency-dependent linear and second non-linear response properties of doped quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Datta, Nirmal Kumar [Department of Physics, Suri Vidyasagar College, Suri, Birbhum 731 101, West Bengal (India); Ghosh, Manas [Department of Chemistry, Physical Chemistry Section, Visva Bharati University, Santiniketan, Birbhum 731 235, West Bengal (India)

    2011-08-15

    We explore the pattern of frequency-dependent linear and second non-linear optical responses of repulsive impurity doped quantum dots harmonically confined in two dimensions. The dopant impurity potential chosen assumes a Gaussian form and it is doped into an on-center location. The quantum dot is subject to a periodically oscillating external electric field. For some fixed values of transverse magnetic field strength ({omega}{sub c}) and harmonic confinement potential ({omega}{sub 0}), the influence of impurity strength (V{sub 0}) and impurity domain ({xi}) on the diagonal components of the frequency-dependent linear ({alpha}{sub xx} and {alpha}{sub yy}) and second non-linear ({gamma}{sub xxxx} and {gamma}{sub yyyy}) responses of the dot are computed through a linear variational route. The investigations reveal that the optical responses undergo enhancement with increase in both V{sub 0} and {xi} values. However, in the limitingly small dopant strength regime one observes a drop in the optical responses with increase in V{sub 0}. A time-average rate of energy transfer to the system is often invoked to support the findings. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Silicon doping techniques using chemical vapor dopant deposition

    NARCIS (Netherlands)

    Popadic, M.

    2009-01-01

    Ultrashallow junctions are essential for the achievement of superior transistor performance, both in MOSFET and bipolar transistors. The stringent demands require state-of-the-art fabrication techniques. At the same time, in a different context, the accurate fabrication of various n type doping

  9. Thermoelectric material comprising scandium doped zinc cadmium oxide

    DEFF Research Database (Denmark)

    2016-01-01

    There is presented a composition of scandium doped Zinc Cadmium Oxide with the general formula ZnzCdxScyO which the inventors have prepared, and for which material the inventors have made the insight that it is particularly advantageous as an n-type oxide material, such as particularly advantageous...

  10. Three dimensional-stacked complementary thin-film transistors using n-type Al:ZnO and p-type NiO thin-film transistors.

    Science.gov (United States)

    Lee, Ching-Ting; Chen, Chia-Chi; Lee, Hsin-Ying

    2018-03-05

    The three dimensional inverters were fabricated using novel complementary structure of stacked bottom n-type aluminum-doped zinc oxide (Al:ZnO) thin-film transistor and top p-type nickel oxide (NiO) thin-film transistor. When the inverter operated at the direct voltage (V DD ) of 10 V and the input voltage from 0 V to 10 V, the obtained high performances included the output swing of 9.9 V, the high noise margin of 2.7 V, and the low noise margin of 2.2 V. Furthermore, the high performances of unskenwed inverter were demonstrated by using the novel complementary structure of the stacked n-type Al:ZnO thin-film transistor and p-type nickel oxide (NiO) thin-film transistor.

  11. Tunnel oxide passivated rear contact for large area n-type front junction silicon solar cells providing excellent carrier selectivity

    Directory of Open Access Journals (Sweden)

    Yuguo Tao

    2016-01-01

    Full Text Available Carrier-selective contact with low minority carrier recombination and efficient majority carrier transport is mandatory to eliminate metal-induced recombination for higher energy conversion efficiency for silicon (Si solar cells. In the present study, the carrier-selective contact consists of an ultra-thin tunnel oxide and a phosphorus-doped polycrystalline Si (poly-Si thin film formed by plasma enhanced chemical vapor deposition (PECVD and subsequent thermal crystallization. It is shown that the poly-Si film properties (doping level, crystallization and dopant activation anneal temperature are crucial for achieving excellent contact passivation quality. It is also demonstrated quantitatively that the tunnel oxide plays a critical role in this tunnel oxide passivated contact (TOPCON scheme to realize desired carrier selectivity. Presence of tunnel oxide increases the implied Voc (iVoc by ~ 125 mV. The iVoc value as high as 728 mV is achieved on symmetric structure with TOPCON on both sides. Large area (239 cm2 n-type Czochralski (Cz Si solar cells are fabricated with homogeneous implanted boron emitter and screen-printed contact on the front and TOPCON on the back, achieving 21.2% cell efficiency. Detailed analysis shows that the performance of these cells is mainly limited by boron emitter recombination on the front side.

  12. Annealing of the Sb-vacancy and a closely related radiation induced defect in n-type germanium

    Science.gov (United States)

    Barnard, Abraham W.; Auret, F. D.; Meyer, W. E.

    2018-04-01

    Deep level transient spectroscopy was used to study the defects induced by alpha-particle irradiation from an Am241 source in antimony doped n-type germanium. Previous investigations of the well know Sb-vacancy defect have led to the discovery of a second defect with very similar emission properties, referred to as the E‧. Although both defects have similar emission rates, they have very different annealing properties. In this study we further investigated these properties of the E‧ in Sb doped samples irradiated at 270 K with alpha particles from an Am241 source. Laplace deep level transient spectroscopy was used to determine the concentration of each defect. An isothermal annealing study of the E‧ was carried out in the temperature range 300 K to 325 K in 5 K increments, while the Sb-vacancy was annealed out completely at 410 K onwards, long after the E‧ was completely annealed out. The annealing activation energy was determined through isothermal annealing profiles for both the Sb-Vacancy and the E‧ as 1.05 eV and 0.73 eV respectively with a prefactor of 2.05 × 109 s-1 and 2.7 × 108 s-1.

  13. Doping of silicon carbide by ion implantation

    International Nuclear Information System (INIS)

    Gimbert, J.

    1999-01-01

    It appeared that in some fields, as the hostile environments (high temperature or irradiation), the silicon compounds showed limitations resulting from the electrical and mechanical properties. Doping of 4H and 6H silicon carbide by ion implantation is studied from a physicochemical and electrical point of view. It is necessary to obtain n-type and p-type material to realize high power and/or high frequency devices, such as MESFETs and Schottky diodes. First, physical and electrical properties of silicon carbide are presented and the interest of developing a process technology on this material is emphasised. Then, physical characteristics of ion implantation and particularly classical dopant implantation, such as nitrogen, for n-type doping, and aluminium and boron, for p-type doping are described. Results with these dopants are presented and analysed. Optimal conditions are extracted from these experiences so as to obtain a good crystal quality and a surface state allowing device fabrication. Electrical conduction is then described in the 4H and 6H-SiC polytypes. Freezing of free carriers and scattering processes are described. Electrical measurements are carried out using Hall effect on Van der Panw test patterns, and 4 point probe method are used to draw the type of the material, free carrier concentrations, resistivity and mobility of the implanted doped layers. These results are commented and compared to the theoretical analysis. The influence of the technological process on electrical conduction is studied in view of fabricating implanted silicon carbide devices. (author)

  14. Electron nonelastic scattering by confined and interface polar optical phonons in a modulation-doped AlGaAs/GaAs/AlGaAs quantum well

    CERN Document Server

    Pozela, K

    2001-01-01

    The calculations of electron scattering rates by polar optical (PO) phonons in an AlGaAs/GaAs/AlGaAs quantum well (QW) with a different width and doping level are performed. The electron-PO-phonon scattering mechanisms which are responsible for the alternate dependence of electron mobility on a QW width, as well as for the decrease of conductivity in the QW with increasing electron concentration are determined. It is shown that the degeneration of electron gas decreases the electron scattering rate by PO-phonon emission and increases the scattering rate by phonon absorption. The competition between the decrease of the intrasubband scattering and the increase of the intersubband scattering by PO-phonon absorption is responsible for the alternate changes of the mobility with a QW width

  15. Controllable electrical properties of metal-doped In2O3 nanowires for high-performance enhancement-mode transistors.

    Science.gov (United States)

    Zou, Xuming; Liu, Xingqiang; Wang, Chunlan; Jiang, Ying; Wang, Yong; Xiao, Xiangheng; Ho, Johnny C; Li, Jinchai; Jiang, Changzhong; Xiong, Qihua; Liao, Lei

    2013-01-22

    In recent years, In(2)O(3) nanowires (NWs) have been widely explored in many technological areas due to their excellent electrical and optical properties; however, most of these devices are based on In(2)O(3) NW field-effect transistors (FETs) operating in the depletion mode, which induces relatively higher power consumption and fancier circuit integration design. Here, n-type enhancement-mode In(2)O(3) NW FETs are successfully fabricated by doping different metal elements (Mg, Al, and Ga) in the NW channels. Importantly, the resulting threshold voltage can be effectively modulated through varying the metal (Mg, Ga, and Al) content in the NWs. A series of scaling effects in the mobility, transconductance, threshold voltage, and source-drain current with respect to the device channel length are also observed. Specifically, a small gate delay time (0.01 ns) and high on-current density (0.9 mA/μm) are obtained at 300 nm channel length. Furthermore, Mg-doped In(2)O(3) NWs are then employed to fabricate NW parallel array FETs with a high saturation current (0.5 mA), on/off ratio (>10(9)), and field-effect mobility (110 cm(2)/V·s), while the subthreshold slope and threshold voltage do not show any significant changes. All of these results indicate the great potency for metal-doped In(2)O(3) NWs used in the low-power, high-performance thin-film transistors.

  16. Discovery of high-performance low-cost n-type Mg3Sb2-based thermoelectric materials with multi-valley conduction bands

    DEFF Research Database (Denmark)

    Zhang, Jiawei; Song, Lirong; Pedersen, Steffen Hindborg

    2017-01-01

    -cost n-type material, Te-doped Mg3Sb1.5Bi0.5, that exhibits a very high figure of merit zT ranging from 0.56 to 1.65 at 300-725 K. Using combined theoretical prediction and experimental validation, we show that the high thermoelectric performance originates from the significantly enhanced power factor...... because of the multi-valley band behaviour dominated by a unique near-edge conduction band with a sixfold valley degeneracy. This makes Te-doped Mg3Sb1.5Bi0.5 a promising candidate for the low- and intermediate-temperature thermoelectric applications....

  17. Concurrent La and A-Site Vacancy Doping Modulates the Thermoelectric Response of SrTiO3: Experimental and Computational Evidence.

    Science.gov (United States)

    Azough, Feridoon; Jackson, Samuel S; Ekren, Dursun; Freer, Robert; Molinari, Marco; Yeandel, Stephen R; Panchmatia, Pooja M; Parker, Stephen C; Maldonado, David Hernandez; Kepaptsoglou, Demie M; Ramasse, Quentin M

    2017-12-06

    To help understand the factors controlling the performance of one of the most promising n-type oxide thermoelectric SrTiO 3 , we need to explore structural control at the atomic level. In Sr 1-x La 2x/3 TiO 3 ceramics (0.0 ≤ x ≤ 0.9), we determined that the thermal conductivity can be reduced and controlled through an interplay of La-substitution and A-site vacancies and the formation of a layered structure. The decrease in thermal conductivity with La and A-site vacancy substitution dominates the trend in the overall thermoelectric response. The maximum dimensionless figure of merit is 0.27 at 1070 K for composition x = 0.50 where half of the A-sites are occupied with La and vacancies. Atomic resolution Z-contrast imaging and atomic scale chemical analysis show that as the La content increases, A-site vacancies initially distribute randomly (x thermal conductivity, an important route to enhancement of the thermoelectric performance. A computational study confirmed that the thermal conductivity of SrTiO 3 is lowered by the introduction of La and A-site vacancies as shown by the experiments. The modeling supports that a critical mass of A-site vacancies is needed to reduce thermal conductivity and that the arrangement of La, Sr, and A-site vacancies has a significant impact on thermal conductivity only at high La concentration.

  18. Breakdown mechanism in AlGaN/GaN high-electron mobility transistor structure on free-standing n-type GaN substrate

    Science.gov (United States)

    Tanabe, Shinichi; Watanabe, Noriyuki; Matsuzaki, Hideaki

    2016-05-01

    The breakdown mechanism in a high-electron mobility transistor structure on free-standing n-type GaN substrates consisting of a C-doped GaN layer as a high-resistivity buffer was investigated with a two-terminal vertical device that has a C-doped GaN buffer between electrodes. Initially, current density increases with the square of bias voltage. This is then followed by an abrupt increase by several orders of magnitude within ten volts, which results in breakdown. These behaviors are consistent with the theory of the space-charge limited current. In this theory, current density increases steeply when trap sites at a certain energy level are completely filled with injected carriers. These results indicate that the existence of trap levels in the C-doped GaN layer is one of the possible factors that determine the breakdown. The trap density and trap level of the C-doped GaN layer were also evaluated.

  19. Comparison of high-power diode pumped actively Q-switched double-clad flower shape co-doped-Er3+:Yb3+fiber laser using acousto-optic and mechanical (optical) modulators

    Science.gov (United States)

    El-Sherif, Ashraf F.; Harfosh, Amr

    2015-09-01

    A diode-pumped acousto-optic Q-switching Er3+:Yb3+ co-doped high-power fiber laser is reported, laser output average power in excess of 1.65 W was achieved for Q-switching at relatively high repetition rates from 10 to 100 kHz. The shortest pulse duration obtained was 10 ns, giving a highest peak power of 9.8 kW and 98 μJ energy per pulse, this is the highest power yet reported from any type of actively Q-switched flower double-clad Er3+:Yb3+ fiber laser operating in low order mode at 1550 nm. The pulse train with high pulse-to-pulse stability of 95% occurred at a range of repetition rates up to 100 kHz with peak power of 0.4 kW, 40 ns pulse width and 16 μJ energy per pulse at 1550 nm for a launched pump power of 5 W. With the mechanical modulation Q-switching of the Er3+:Yb3+ co-doped fiber laser, it was found that the narrowest pulse width of 35 ns was obtained with peak power of 15.5 kW and energy per pulse 0.5 mJ at pulse repetition frequency of 1 kHz. A moderate pulse-to-pulse stability of 75% occurred over a range of high repetition rates. A comparison between mechanical modulation and acousto-optic Q-switching has been made at a repetition rate of 20 kHz. The energy per pulse, pulse width, and the average power of a mechanical optical Q-switching laser were greater than for the acousto-optic Q-switching, but the pulse width is narrower and so the high peak power of an acousto-optic Q-switching pulse is greater than for the mechanical (optical) Q-switching laser at repetition rates of up to 100 kHz.

  20. Modulation of electromagnetic and absorption properties in 18-26.5 GHz frequency range of strontium hexaferrites with doping of cobalt-zirconium

    Energy Technology Data Exchange (ETDEWEB)

    Pubby, Kunal; Narang, Sukhleen Bindra [Guru Nanak Dev University, Department of Electronics Technology, Amritsar (India); Kaur, Prabhjyot; Chawla, S.K. [Guru Nanak Dev University, Department of Chemistry, Centre for Advanced Studies-I, Amritsar (India)

    2017-05-15

    Hexaferrite nano-particles of stoichiometric composition Sr(CoZr){sub x}Fe{sub 12-2x}O{sub 19}, with x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 were prepared using sol-gel auto-combustion route owing to its advantages such as low sintering temperature requirement, homogeneity and uniformity of grains. Tartaric acid as a fuel was utilized to complete the chemical reaction. The goal of this study is to analyse the effect of co-substitution of cobalt and zirconium on the electromagnetic and absorption properties of pure SrFe{sub 12}O{sub 19} hexaferrite. The properties were measured on the rectangular pellets of thickness 2.5 mm for K-frequency band using Vector Network Analyzer. The doping of Co-Zr has resulted in increase in real as well as imaginary parts of permittivity. The values of real permittivity lie in the range 3.6-7.0 for all the composition. The real part of permeability remains in range 0.7-1.6 in the studied frequency band for all the samples and shows slightly increasing trend with frequency. The maximum values of dielectric loss tangent peak (3.04) and magnetic loss tangent peak (2.34), among all the prepared compositions, have been observed for composition x = 0.2. Compositions with x = 0.6 and x = 0.0 also have high dielectric and magnetic loss peaks. Dielectric loss peaks are attributed to dielectric resonance and magnetic loss peaks are attributed to natural resonance. Experimentally determined reflection loss results show that all six compositions of prepared series have high values of absorption to propose them as single-layer absorbers in 18-26.5 GHz frequency range. The composition with x = 0.2 has maximum absorption capacity with reflection loss peak of -37.2 dB at 24.3 GHz frequency. The undoped composition also has high absorption peak (-25.46 dB), but -10 dB absorption bandwidth is minimum (2.2 GHz) out of the present series. Maximum absorption bandwidth is obtained for x = 1.0 (4.1 GHz). Other doped compositions also have high absorption bandwidth

  1. Modulation of electromagnetic and absorption properties in 18-26.5 GHz frequency range of strontium hexaferrites with doping of cobalt-zirconium

    Science.gov (United States)

    Pubby, Kunal; Narang, Sukhleen Bindra; Kaur, Prabhjyot; Chawla, S. K.

    2017-05-01

    Hexaferrite nano-particles of stoichiometric composition {{Sr}}{({{CoZr}})_x}{{F}}{{{e}}_{12 - 2x}}{{{O}}_{19}}, with x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 were prepared using sol-gel auto-combustion route owing to its advantages such as low sintering temperature requirement, homogeneity and uniformity of grains. Tartaric acid as a fuel was utilized to complete the chemical reaction. The goal of this study is to analyse the effect of co-substitution of cobalt and zirconium on the electromagnetic and absorption properties of pure {{SrF}}{{{e}}_{12}}{{{O}}_{19}} hexaferrite. The properties were measured on the rectangular pellets of thickness 2.5 mm for K-frequency band using Vector Network Analyzer. The doping of Co-Zr has resulted in increase in real as well as imaginary parts of permittivity. The values of real permittivity lie in the range 3.6-7.0 for all the composition. The real part of permeability remains in range 0.7-1.6 in the studied frequency band for all the samples and shows slightly increasing trend with frequency. The maximum values of dielectric loss tangent peak (3.04) and magnetic loss tangent peak (2.34), among all the prepared compositions, have been observed for composition x = 0.2. Compositions with x = 0.6 and x = 0.0 also have high dielectric and magnetic loss peaks. Dielectric loss peaks are attributed to dielectric resonance and magnetic loss peaks are attributed to natural resonance. Experimentally determined reflection loss results show that all six compositions of prepared series have high values of absorption to propose them as single-layer absorbers in 18-26.5 GHz frequency range. The composition with x = 0.2 has maximum absorption capacity with reflection loss peak of -37.2 dB at 24.3 GHz frequency. The undoped composition also has high absorption peak (-25.46 dB), but -10 dB absorption bandwidth is minimum (2.2 GHz) out of the present series. Maximum absorption bandwidth is obtained for x = 1.0 (4.1 GHz). Other doped compositions also

  2. Towards the next generation 23% efficient n-type cells with low cost manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Yelundur, Vijay [Suniva Inc., Norcross, GA (United States)

    2017-04-19

    Suniva, Inc., in collaboration with the University Center for Excellence in Photovoltaics (UCEP) at the Georgia Institute of Technology (GIT) proposed this comprehensive three year program to enable the development of an advanced high performance product that will help the US regain its competitive edge in PV. This project was designed to overcome cost and efficiency barriers through advances in PV science, technology innovation, low-cost manufacturing and full production of ~22.5% efficient n-type Si cells in Norcross, GA. At the heart of the project is the desire to complement the technology being developed concurrently under the Solarmat and ARPAe initiatives to develop a differentiated product superior in both performance and cost effectiveness to the competing alternatives available on the market, and push towards achieving SunShot objectives while ensuring a sustainable business model based on US manufacturing. A significant reduction of the costs in modules produced today will need to combine reductions in wafer costs, cell processing costs as well as module fabrication costs while delivering a product that is not only more efficient under test conditions but also increases the energy yield in outdoor operations. This project will result in a differentiated high performance product and technology that is consistent with sustaining PV manufacturing in the US for a longer term and further highlights the need for continued support for developing the next generation concepts that can keep US manufacturing thriving to support the growing demand for PV in the US and consistent with the US government’s mandates for energy independence.

  3. Study of Si-Ge interdiffusion with phosphorus doping

    KAUST Repository

    Cai, Feiyang

    2016-10-28

    Si-Ge interdiffusion with phosphorus doping was investigated by both experiments and modeling. Ge/Si1-x Ge x/Ge multi-layer structures with 0.75doping, and a dislocation density of 108 to 109 cm−2 range were studied. The P-doped sample shows an accelerated Si-Ge interdiffusivity, which is 2–8 times of that of the undoped sample. The doping dependence of the Si-Ge interdiffusion was modelled by a Fermi-enhancement factor. The results show that the Si-Ge interdiffusion coefficient is proportional to n2/n2i for the conditions studied, which indicates that the interdiffusion in a high Ge fraction range with n-type doping is dominated by V2− defects. The Fermi-enhancement factor was shown to have a relatively weak dependence on the temperature and the Ge fraction. The results are relevant to the structure and thermal processing condition design of n-type doped Ge/Si and Ge/SiGe based devices such as Ge/Si lasers.

  4. Low-noise behavior of InGaAs quantum-well-structured modulation-doped FET's from 10 to the -2nd to 10 to the 8 Hz

    Science.gov (United States)

    Liu, Shih-Ming J.; Das, Mukunda B.; Peng, Chin-Kun; Klem, John; Henderson, Timothy S.

    1986-01-01

    Equivalent gate noise voltage spectra of 1-micron gate-length modulation-doped FET's with pseudomorphic InGaAs quantum-well structure have been measured for the frequency range of 0.01 Hz to 100 MHz and commpared with the noise spectra of conventional AlGaAs/GaAs MODFET's and GaAs MESFET's. The prominent generation-recombination (g-r) noise bulge commonly observed in the vicinity of 10 kHz in conventional MODFET's at 300 K does not appear in the case of the new InGaAs quantum-well MODFET. Instead, its noise spectra indicate the presence of low-intensity multiple g-r noise components superimposed on a reduced 1/f noise. The LF noise intensity in the new device appears to be the lowest among those observed in any MODFET or MESFET. The noise spectra at 82 K in the new device represent nearly true 1/f noise. This unusual low-noise behavior of the new structure suggests the effectiveness of electron confinement in the quantum well that significantaly reduces electron trapping in the n-AlGaAs, and thus eliminates the g-r noise bulge observed in conventional MODFET's.

  5. Effects of KrF excimer laser irradiation on metal contacts to n-type and p-type GaN

    International Nuclear Information System (INIS)

    Jang, Ho Won; Sands, T.; Lee, Jong-Lam

    2003-01-01

    Electrical properties of metal contacts on laser-irradiated n-type and p-type GaN surfaces were investigated using current-voltage, capacitance-voltage, and synchrotron radiation photoemission spectroscopy. After the irradiation of a KrF excimer laser pulse (600 mJ/cm 2 at 248 nm for 38 ns) onto Si-doped GaN, a nonalloyed Ti/Al metallization formed an ohmic contact with the specific contact resistivity of 1.7x10 -6 Ω cm 2 . The laser irradiation decomposed GaN into metallic Ga and nitrogen gas. The decomposed metallic Ga reacted with oxygen in air to form a Ga oxide layer with the thickness of ∼40 Aa, producing a large number of N vacancies near the surface. The formation of a degenerated n-type GaN layer resulted in the low contact resistivity. For Mg-doped GaN, the laser irradiation increased the effective acceptor concentration. Simultaneously, the activation efficiency of Mg dopants was enhanced by the photon-assisted breaking of Mg-H bonds and/or the removal of hydrogen atoms in the presence of oxygen, producing the p-type GaN with an increased hole concentration. As a result, the contact resistivity of an oxidized Ni/Au contact could be reduced from 1.3x10 -3 to 3.6x10 -4 Ω cm 2

  6. P-type sp3-bonded BN/n-type Si heterodiode solar cell fabricated by laser-plasma synchronous CVD method

    International Nuclear Information System (INIS)

    Komatsu, Shojiro; Nagata, Takahiro; Chikyo, Toyohiro; Sato, Yuhei; Watanabe, Takayuki; Hirano, Daisuke; Takizawa, Takeo; Nakamura, Katsumitsu; Hashimoto, Takuya; Nakamura, Takuya; Koga, Kazunori; Shiratani, Masaharu; Yamamoto, Atsushi

    2009-01-01

    A heterojunction of p-type sp 3 -bonded boron nitride (BN) and n-type Si fabricated by laser-plasma synchronous chemical vapour deposition (CVD) showed excellent rectifying properties and proved to work as a solar cell with photovoltaic conversion efficiency of 1.76%. The BN film was deposited on an n-type Si (1 0 0) substrate by plasma CVD from B 2 H 6 + NH 3 + Ar while doping of Si into the BN film was induced by the simultaneous irradiation of an intense excimer laser with a pulse power of 490 mJ cm -2 , at a wavelength of 193 nm and at a repetition rate of 20 Hz. The source of dopant Si was supposed to be the Si substrate ablated at the initial stage of the film growth. The laser enhanced the doping (and/or diffusion) of Si into BN as well as the growth of sp 3 -bonded BN simultaneously in this method. P-type conduction of BN films was determined by the hot (thermoelectric) probe method. The BN/Si heterodiode with an essentially transparent p-type BN as a front layer is supposed to efficiently absorb light reaching the active region so as to potentially result in high efficiency.

  7. Calcium decorated and doped phosphorene for gas adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Lalitha, Murugan; Nataraj, Yuvarani; Lakshmipathi, Senthilkumar, E-mail: lsenthilkumar@buc.edu.in

    2016-07-30

    Highlights: • Phosphorene exhibits n-type/p-type nature on decorating/doping calcium respectively. • Gas molecules (CH{sub 4}, CO{sub 2}, H{sub 2} and NH{sub 3}) are physisorbed on phosphorene. • Ca decorated Phosphorene is recommended for high density hydrogen storage applications. • Calcium doping on zigzag and armchair sites makes phosphorene more reactive. • CH{sub 4}, CO{sub 2}, H{sub 2} prefer Ca-doped on zigzag1 site, whereas ammonia prefers Ca-doped on armchair. - Abstract: In this paper, we present the results from first-principles study based on the electronic structure and adsorption characteristics of CH{sub 4}, CO{sub 2}, H{sub 2} and NH{sub 3} adsorbed on Ca decorated/doped phosphorene. Our study finds that phosphorene exhibits n-type behaviour on decorating calcium, and p-type on doping calcium. Gas molecules are physisorbed on both pristine and calcium-mediated phosphorene, visible through their lower binding energy and charge transfer values. Ca decorated phosphorene is suitable for hydrogen storage due to its higher binding energy for H{sub 2}. Ca doped structures shows increased binding affinity towards CH{sub 4} and NH{sub 3} in zigzag1 direction and armchair directions respectively. The extracts of our study implies that Ca doped phosphorene possess increased binding affinity towards gas molecules, and the results are highly helpful for gas adsorption and to design gas sensors based on calcium doped or decorated phosphorene.

  8. Origin of n-type conductivity in two-dimensional InSe: In atoms from surface adsorption and van der Waals gap

    Science.gov (United States)

    Wang, Hui; Shi, Jun-jie; Huang, Pu; Ding, Yi-min; Wu, Meng; Cen, Yu-lang; Yu, Tongjun

    2018-04-01

    Recently, two-dimensional (2D) InSe nanosheet becomes a promising material for electronic and optoelectronic nano-devices due to its excellent electron transport, wide bandgap tunability and good metal contact. The inevitable native point defects are essential in determining its characteristics and device performance. Here we investigate the defect formation energy and thermodynamic transition levels for the most important native defects and clarify the physical origin of n-type conductivity in unintentionally doped 2D InSe by using the powerful first-principles calculations. We find that both surface In adatom and Se vacancy are the key defects, and the In adatom, donated 0.65 electrons to the host, causes the n-type conductivity in monolayer InSe under In-rich conditions. For bilayer or few-layer InSe, the In interstitial within the van der Waals gap, transferred 0.68 electrons to InSe, is found to be the most stable donor defect, which dominates the n-type character. Our results are significant for understanding the defect nature of 2D InSe and improving the related nano-device performance.

  9. Enhanced thermoelectric performance of n-type Bi2O2Se ceramics induced by Ge doping

    Czech Academy of Sciences Publication Activity Database

    Ruleová, P.; Plecháček, T.; Kašparová, J.; Vlček, Milan; Beneš, L.; Lostak, P.; Drašar, Č.

    2018-01-01

    Roč. 47, č. 2 (2018), s. 1459-1466 ISSN 0361-5235 R&D Projects: GA ČR(CZ) GA16-07711S Institutional support: RVO:61389013 Keywords : semiconductors * chalcogenides * x-ray diffraction Subject RIV: CA - Inorganic Chemistry OBOR OECD: Inorganic and nuclear chemistry Impact factor: 1.579, year: 2016

  10. Thermoelectric properties of rare earth-doped n-type Bi2Se0∙3Te2∙7 ...

    Indian Academy of Sciences (India)

    Administrator

    of solid-state electronic cooling and power generation. The efficiency of TE devices is strongly associated with the dimensionless figure of merit (ZT) of TE materials, defined as ZT = (S2σ /κ )T, where S, σ, κ and T are the. Seebeck coefficient, electrical conductivity, thermal con- ductivity and absolute temperature, respectively ...

  11. Extrinsic doping of CuGaSe2 single crystals

    Science.gov (United States)

    Schön, J. H.

    2000-02-01

    Technological applications of semiconductors depend critically on the ability to dope them. Single crystals of CuGaSe2 were doped during crystal growth either by a post-growth diffusion step or by ion-implantation, in order to study the limits of extrinsic doping. The electrical and optical properties of the doped samples are analysed by Hall effect and photoluminescence (PL) measurements. The carrier concentration at room temperature can be adjusted between 2 × 1019 cm-3 (p-type) and 1017 cm-3 (n-type). Various donor and acceptor levels are identified and ascribed to dopant-induced point defects taking into account the dopant concentration and/or the post-growth treatment of the single crystals.

  12. Controlling the optical bistability via quantum interference in a four-level N-type atomic system

    International Nuclear Information System (INIS)

    Sahrai, M.; Asadpour, S.H.; Mahrami, H.; Sadighi-Bonabi, R.

    2011-01-01

    We investigate the optical bistability (OB) and optical multi-stability (OM) in a four-level N-type atomic system. The effect of spontaneously generated coherence (SGC) on OB and OM is then discussed. It is found that SGC makes the medium phase dependent, so the optical bistability and multi-stability threshold can be controlled via relative phase between applied fields. We realize that the frequency detuning of probe and coupling fields with the corresponding atomic transition plays an important role in creation OB and OM. Moreover, the effect of laser coupling fields and an incoherent pumping field on reduction of OB and OM threshold is then discussed. - Highlights: → We modulate the optical bistability (OB) in a four-level N-type atomic system. The effect of spontaneously generated coherence on OB is discussed. → Spontaneously generated coherence makes the medium phase dependent. → The frequency of coupling field can reduce OB threshold. → We discuss the effect of an incoherent pumping field on reduction of OB threshold.

  13. Comparison on mechanical properties of heavily phosphorus- and arsenic-doped Czochralski silicon wafers

    Science.gov (United States)

    Yuan, Kang; Sun, Yuxin; Lu, Yunhao; Liang, Xingbo; Tian, Daxi; Ma, Xiangyang; Yang, Deren

    2018-04-01

    Heavily phosphorus (P)- and arsenic (As)-doped Czochralski silicon (CZ-Si) wafers generally act as the substrates for the epitaxial silicon wafers used to fabricate power and communication devices. The mechanical properties of such two kinds of n-type heavily doped CZ silicon wafers are vital to ensure the quality of epitaxial silicon wafers and the manufacturing yields of devices. In this work, the mechanical properties including the hardness, Young's modulus, indentation fracture toughness and the resistance to dislocation motion have been comparatively investigated for heavily P- and As-doped CZ-Si wafers. It is found that heavily P-doped CZ-Si possesses somewhat higher hardness, lower Young's modulus, larger indentation fracture toughness and stronger resistance to dislocation motion than heavily As-doped CZ-Si. The mechanisms underlying this finding have been tentatively elucidated by considering the differences in the doping effects of P and As in silicon.

  14. Radiation hardness of n-type SiC Schottky barrier diodes irradiated with MeV He ion microbeam

    Energy Technology Data Exchange (ETDEWEB)

    Pastuović, Željko, E-mail: zkp@ansto.gov.au [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Capan, Ivana [Material Physics Division, Institute Rudjer Boskovic, PO Box 180, 10000 Zagreb (Croatia); Cohen, David D. [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Forneris, Jacopo [Physics Department and NIS Excellence Centre, University of Torino, via P. Giuria 1, 10125 Torino (Italy); Iwamoto, Naoya; Ohshima, Takeshi [Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Siegele, Rainer [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Hoshino, Norihiro; Tsuchida, Hidekazu [Central Research Institute of Electric Power Industry, 2-6-1 Nagasaka, Yokosuka, Kanagawa 240-0196 (Japan)

    2015-04-01

    We studied the radiation hardness of 4H-SiC Schottky barrier diodes (SBD) for the light ion detection and spectroscopy in harsh radiation environments. n-Type SBD prepared on nitrogen-doped (∼4 × 10{sup 14} cm{sup −3}) epitaxial grown 4H-SiC thin wafers have been irradiated by a raster scanning alpha particle microbeam (2 and 4 MeV He{sup 2+} ions separately) in order to create patterned damage structures at different depths within a sensitive volume of tested diodes. Deep Level Transient Spectroscopy (DLTS) analysis revealed the formation of two deep electron traps in the irradiated and not thermally treated 4H-SiC within the ion implantation range (E1 and E2). The E2 state resembles the well-known Z{sub 1/2} center, while the E1 state could not be assigned to any particular defect reported in the literature. Ion Beam Induced Charge (IBIC) microscopy with multiple He ion probe microbeams (1–6 MeV) having different penetration depths in tested partly damaged 4H-SiC SBD has been used to determine the degradation of the charge collection efficiency (CCE) over a wide fluence range of damaging alpha particle. A non-linear behavior of the CCE decrease and a significant degradation of the spectroscopic performance with increasing He ion fluence were observed above the value of 10{sup 11} cm{sup −2}.

  15. A simulation-based proposed high-k heterostructure AlGaAs/Si junctionless n-type tunnel FET

    International Nuclear Information System (INIS)

    Rahi Shiromani Balmukund; Asthana Pranav; Ghosh Bahniman

    2014-01-01

    We propose a heterostructure junctionless tunnel field effect transistor (HJL-TFET) using AlGaAs/Si. In the proposed HJL-TFET, low band gap silicon is used in the source side and higher band gap AlGaAs in the drain side. The whole AlGaAs/Si region is heavily doped n-type. The proposed HJL-TFET uses two isolated gates (named gate, gate1) with two different work functions (gate = 4.2 eV, gate1 = 5.2 eV respectively). The 2-D nature of HJL-TFET current flow is studied. The proposed structure is simulated in Silvaco with different gate dielectric materials. This structure exhibits a high on current in the range of 1.4 × 10 −6 A/μm, the off current remains as low as 9.1 × 10 −14 A/μm. So I ON /I OFF ratio of ≃ 10 8 is achieved. Point subthreshold swing has also been reduced to a value of ≃ 41 mV/decade for TiO 2 gate material. (semiconductor devices)

  16. Doping and cluster formation in diamond

    KAUST Repository

    Schwingenschlögl, Udo

    2011-09-09

    Introducing a cluster formation model, we provide a rational fundamental viewpoint for the difficulty to achieve n-type dopeddiamond. We argue that codoping is the way forward to form appropriately doped shallow regions in diamond and other forms of carbon such as graphene. The electronegativities of the codopants are an important design criterion for the donor atom to efficiently donate its electron. We propose that the nearest neighbour codopants should be of a considerably higher electronegativity compared to the donor atom. Codoping strategies should focus on phosphorous for which there are a number of appropriate codopants.

  17. Doping Cu{sub 2}O in Electrolyte Solution: Dopant Incorporation, Atomic Structures and Electrical Properties

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Meng; Zhang, Qiming

    2013-11-24

    We have pursued a number of research activities between April 2010 and April 2011: A detailed study on n-type doping in Cu2O by Br; An analysis of natural resource limitations to terawatt-scale solar cells; Attempt to achieve a 1.4-eV direct band gap in Ni sulfides (NiSx); First-principles studies of doping in Cu2O and electronic structures of NiSx.

  18. Enhanced thermoelectric properties of bismuth telluride-organic hybrid films via graphene doping

    International Nuclear Information System (INIS)

    Rahman, Airul Azha Abd; Umar, Akrajas Ali; Salleh, Muhamad Mat; Chen, Xiaomei; Oyama, Munetaka

    2016-01-01

    The thermoelectric properties of graphene-doped bismuth telluride-PEDOT:PSS-glycerol (hybrid) films were investigated. Prior to the study, p-type and n-type hybrid films were prepared by doping the PEDOT:PSS-glycerol with the p- and n-type bismuth telluride. Graphene-doped hybrid films were prepared by adding graphene particles of concentration ranging from 0.02 to 0.1 wt% into the hybrid films. Films of graphene-doped hybrid system were then prepared on a glass substrate using a spin-coating technique. It was found that the electrical conductivity of the hybrid films increases with the increasing of the graphene-dopant concentration and optimum at 0.08 wt% for both p- and n-type films, namely 400 and 195 S/cm, respectively. Further increasing in the concentration caused a decreasing in the electrical conductivity. Analysis of the thermoelectric properties of the films obtained that the p-type film exhibited significant improvement in its thermoelectric properties, where the thermoelectric properties increased with the increasing of the doping concentration. Meanwhile, for the case of n-type film, graphene doping showed a negative effect to the thermoelectrical properties, where the thermoelectric properties decreased with the increasing of doping concentration. Seebeck coefficient (and power factor) for optimum p-type and n-type hybrid thin films, i.e., doped with 0.08 wt% of graphene, is 20 μV/K (and 160 μW m -1 K -2 ) and 10 μV/K (and 19.5 μW m -1 K -2 ), respectively. The obtained electrical conductivity and thermoelectric properties of graphene-doped hybrid film are interestingly several orders higher than the pristine hybrid films. A thermocouple device fabricated utilizing the p- and n-type graphene-doped hybrid films can generate an electric voltage as high as 2.2 mV under a temperature difference between the hot-side and the cold-side terminal as only low as 55 K. This is equivalent to the output power as high as 24.2 nW (for output load as high as 50

  19. Enhanced thermoelectric properties of bismuth telluride-organic hybrid films via graphene doping

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, Airul Azha Abd [Universiti Kebangsaan Malaysia UKM, Institute of Microengineering and Nanoelectronics, Bangi, Selangor (Malaysia); Technology Park Malaysia, Malaysia Institute of Microelectronics and System, Kuala Lumpur (Malaysia); Umar, Akrajas Ali; Salleh, Muhamad Mat [Universiti Kebangsaan Malaysia UKM, Institute of Microengineering and Nanoelectronics, Bangi, Selangor (Malaysia); Chen, Xiaomei [Jimei University, College of Food and Biological Engineering, Jimei, Xiamen (China); Oyama, Munetaka [Kyoto University, Graduate School of Engineering, Nishikyoku, Kyoto (Japan)

    2016-02-15

    The thermoelectric properties of graphene-doped bismuth telluride-PEDOT:PSS-glycerol (hybrid) films were investigated. Prior to the study, p-type and n-type hybrid films were prepared by doping the PEDOT:PSS-glycerol with the p- and n-type bismuth telluride. Graphene-doped hybrid films were prepared by adding graphene particles of concentration ranging from 0.02 to 0.1 wt% into the hybrid films. Films of graphene-doped hybrid system were then prepared on a glass substrate using a spin-coating technique. It was found that the electrical conductivity of the hybrid films increases with the increasing of the graphene-dopant concentration and optimum at 0.08 wt% for both p- and n-type films, namely 400 and 195 S/cm, respectively. Further increasing in the concentration caused a decreasing in the electrical conductivity. Analysis of the thermoelectric properties of the films obtained that the p-type film exhibited significant improvement in its thermoelectric properties, where the thermoelectric properties increased with the increasing of the doping concentration. Meanwhile, for the case of n-type film, graphene doping showed a negative effect to the thermoelectrical properties, where the thermoelectric properties decreased with the increasing of doping concentration. Seebeck coefficient (and power factor) for optimum p-type and n-type hybrid thin films, i.e., doped with 0.08 wt% of graphene, is 20 μV/K (and 160 μW m{sup -1} K{sup -2}) and 10 μV/K (and 19.5 μW m{sup -1} K{sup -2}), respectively. The obtained electrical conductivity and thermoelectric properties of graphene-doped hybrid film are interestingly several orders higher than the pristine hybrid films. A thermocouple device fabricated utilizing the p- and n-type graphene-doped hybrid films can generate an electric voltage as high as 2.2 mV under a temperature difference between the hot-side and the cold-side terminal as only low as 55 K. This is equivalent to the output power as high as 24.2 nW (for output

  20. The electrical and optical properties of Cu-doped In{sub 2}O{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Fan [School of Physical Science and Technology and Shenzhen Key Laboratory of Sensor Technology, Shenzhen University, Shenzhen, 518060 (China); Cai, Xing-Min, E-mail: caixm@graduate.hku.hk [School of Physical Science and Technology and Shenzhen Key Laboratory of Sensor Technology, Shenzhen University, Shenzhen, 518060 (China); Zhong, Xue; Tian, Xiao-Qing [School of Physical Science and Technology and Shenzhen Key Laboratory of Sensor Technology, Shenzhen University, Shenzhen, 518060 (China); Jing, Shou-Yong [The Institute of Optoelectronics, Shenzhen University, Shenzhen, 518060 (China); Huang, Long-Biao; Roy, V.A.L. [Center of Super-Diamond and Advanced Films (COSDAF)and Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tong, Hong Kong (China); Zhang, Dong-Ping; Fan, Ping; Luo, Jing-Tin; Zheng, Zhuang-Hao; Liang, Guang-Xing [School of Physical Science and Technology and Shenzhen Key Laboratory of Sensor Technology, Shenzhen University, Shenzhen, 518060 (China)

    2014-04-01

    To study the effect of Cu doping, In{sub 2}O{sub 3} and Cu-doped In{sub 2}O{sub 3} films were deposited on K9 glass and Si substrates with the same experimental parameters. All the films were found to be body centered cubic and have the same preferred orientation. No secondary phases were detected in Cu-doped In{sub 2}O{sub 3}. The atomic ratio of Cu to Cu plus In was approximately 18% in Cu-doped In{sub 2}O{sub 3} films which were found to be n-type. After Cu doping, the resistivity of the films increased by 3 to 4 orders of magnitude and the film with higher Cu content had larger resistivity, due to compensation. Cu doping is found to widen the optical band gap of In{sub 2}O{sub 3} films, possibly due to a metal–insulator transition. - Highlights: • Cu doping changes neither the structure nor the preferred orientation of the films. • Cu doped In{sub 2}O{sub 3} are n-type. • Cu doped In{sub 2}O{sub 3} films have much larger resistivity than undoped In{sub 2}O{sub 3}. • Cu doped In{sub 2}O{sub 3} films have larger optical band gaps than undoped In{sub 2}O{sub 3}.

  1. Doping and musculoskeletal system: short-term and long-lasting effects of doping agents.

    Science.gov (United States)

    Nikolopoulos, Dimitrios D; Spiliopoulou, Chara; Theocharis, Stamatios E

    2011-10-01

    Doping is a problem that has plagued the world of competition and sports for ages. Even before the dawn of Olympic history in ancient Greece, competitors have looked for artificial means to improve athletic performance. Since ancient times, athletes have attempted to gain an unfair competitive advantage through the use of doping substances. A Prohibited List of doping substances and methods banned in sports is published yearly by the World Anti-Doping Agency. Among the substances included are steroidal and peptide hormones and their modulators, stimulants, glucocorticosteroids, β₂-agonists, diuretics and masking agents, narcotics, and cannabinoids. Blood doping, tampering, infusions, and gene doping are examples of prohibited methods indicated on the List. Apart from the unethical aspect of doping, as it abrogates fair-play's principle, it is extremely important to consider the hazards it presents to the health and well-being of athletes. The referred negative effects for the athlete's health have to do, on the one hand, by the high doses of the performance-enhancing agents and on the other hand, by the relentless, superhuman strict training that the elite or amateur athletes put their muscles, bones, and joints. The purpose of this article is to highlight the early and the long-lasting consequences of the doping abuse on bone and muscle metabolism. © 2010 The Authors Fundamental and Clinical Pharmacology © 2010 Société Française de Pharmacologie et de Thérapeutique.

  2. Highly Efficient p-i-n Type Organic Light-emitting Diodes Using ...

    African Journals Online (AJOL)

    Both predominantly hole transporting material (TCTA) and an exclusively electron transporting host material (TAZ) are doped with the green phosphorescent dye tris(phenylpyridine)iridium [Ir(ppy)3]. The intrinsic and doped transport and emission layers are formed using a high vacuum controlled co-evaporation deposition ...

  3. Simultaneous nitrogen doping and reduction of graphene oxide.

    Science.gov (United States)

    Li, Xiaolin; Wang, Hailiang; Robinson, Joshua T; Sanchez, Hernan; Diankov, Georgi; Dai, Hongjie

    2009-11-04

    We developed a simple chemical method to obtain bulk quantities of N-doped, reduced graphene oxide (GO) sheets through thermal annealing of GO in ammonia. X-ray photoelectron spectroscopy (XPS) study of GO sheets annealed at various reaction temperatures reveals that N-doping occurs at a temperature as low as 300 degrees C, while the highest doping level of approximately 5% N is achieved at 500 degrees C. N-doping is accompanied by the reduction of GO with decreases in oxygen levels from approximately 28% in as-made GO down to approximately 2% in 1100 degrees C NH(3) reacted GO. XPS analysis of the N binding configurations of doped GO finds pyridinic N in the doped samples, with increased quaternary N (N that replaced the carbon atoms in the graphene plane) in GO annealed at higher temperatures (> or = 900 degrees C). Oxygen groups in GO were found responsible for reactions with NH(3) and C-N bond formation. Prereduced GO with fewer oxygen groups by thermal annealing in H(2) exhibits greatly reduced reactivity with NH(3) and a lower N-doping level. Electrical measurements of individual GO sheet devices demonstrate that GO annealed in NH(3) exhibits higher conductivity than those annealed in H(2), suggesting more effective reduction of GO by annealing in NH(3) than in H(2), consistent with XPS data. The N-doped reduced GO shows clearly n-type electron doping behavior with the Dirac point (DP) at negative gate voltages in three terminal devices. Our method could lead to the synthesis of bulk amounts of N-doped, reduced GO sheets useful for various practical applications.

  4. Preparation of n-type Bi{sub 2}Te{sub 3} thermoelectric materials by non-contact dispenser printing combined with selective laser melting

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Keping; Yan, Yonggao; Zhang, Jian; Mao, Yu; Xie, Hongyao; Zhang, Qingjie; Tang, Xinfeng [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, Hubei (China); Yang, Jihui [Department of Materials Science and Engineering, University of Washington, Seattle, WA (United States); Uher, Ctirad [Department of Physics, University of Michigan, Ann Arbor, MI (United States)

    2017-06-15

    The manufacturing cost has been a bottle neck for broader applications of thermoelectric (TE) modules. We have developed a rapid, facile, and low cost method that combines non-contact dispenser printing with selective laser melting (SLM) and we demonstrate it on n-type Bi{sub 2}Te{sub 3}-based materials. Using this approach, single phase n-type Bi{sub 2}Te{sub 2.7}Se{sub 0.3} thin layers with the Seebeck coefficient of -152 μV K{sup -1} at 300 K have been prepared. Assembling such thin layers on top of each other, the performance of thus prepared bulk sample is comparable to Bi{sub 2}Te{sub 3}-based materials fabricated by the conventional techniques. Dispenser printing combined with SLM is a promising manufacturing process for TE materials. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Impurity binding energy for δ-doped quantum well structures

    Indian Academy of Sciences (India)

    Administrator

    Abstract. The binding energy of an impurity delta layer situated either in the centre or at the edge of a quantum well (QW) is theoretically considered for the example of n-type Si0∙8Ge0∙2/Si/Si0∙8Ge0∙2 QW doped with phosphorus. Calculations are made for the case of not so big impurity concentrations, when impurity.

  6. New Conotoxin SO-3 Targeting N-type Voltage-Sensitive Calcium Channels

    Directory of Open Access Journals (Sweden)

    Lei Wen

    2006-04-01

    Full Text Available Selective blockers of the N-type voltage-sensitive calcium (CaV channels are useful in the management of severe chronic pain. Here, the structure and function characteristics of a novel N-type CaV channel blocker, SO-3, are reviewed. SO-3 is a 25-amino acid conopeptide originally derived from the venom of Conus striatus, and contains the same 4-loop, 6-cysteine framework (C-C-CC-C-C as O-superfamily conotoxins. The synthetic SO-3 has high analgesic activity similar to ω-conotoxin MVIIA (MVIIA, a selective N-type CaV channel blocker approved in the USA and Europe for the alleviation of persistent pain states. In electrophysiological studies, SO-3 shows more selectivity towards the N-type CaV channels than MVIIA. The dissimilarity between SO-3 and MVIIA in the primary and tertiary structures is further discussed in an attempt to illustrate the difference in selectivity of SO-3 and MVIIA towards N-type CaV channels.

  7. Doping GaP core-shell nanowire pn-junctions

    DEFF Research Database (Denmark)

    Yazdi, Sadegh; Berg, Alexander; Borgström, Magnus T.

    2015-01-01

    The doping process in GaP core-shell nanowire pn-junctions using different precursors is evaluated by mapping the nanowires' electrostatic potential distribution by means of off-axis electron holography. Three precursors, triethyltin (TESn), ditertiarybutylselenide, and silane are investigated......, ditertiarybutylselenide and silane for n-type doping of the shell and that the concentration of p-type dopants is higher in the region of core grown parasitically by vapor-solid mechanism due to unintentional carbon doping from trimethylgallium precursor....

  8. The doping concentration and physical properties measurement of silicon water using tera hertz wave

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sung Hyeon; Oh, Gyung Hwan; Kim, Hak Sung [Dept. of Mechanical Convergence Engineering, Hanyang University, Seoul(Korea, Republic of)

    2017-02-15

    In this study, a tera hertz time domain spectroscopy (THz-TDS) imaging technique was used to measure doping concentration and physical properties (such as refractive index and permittivity) of the doped silicon (Si) wafers. The transmission and reflection modes with an incidence angle of 30° were employed to determine the physical properties of the doped Si wafers. The doping concentrations of the prepared Si wafers were varied from 10{sup 14} to 10{sup 18} in both N-type and P-type cases. Finally, the correlation between the doping concentration and the power of the THz wave was determined by measuring the powers of the transmitted and reflected THz waves of the doped Si wafers. Additionally, the doped thickness, the refractive index, and permittivity of each doped Si wafer were calculated using the THz time domain waveform. The results indicate that the THz-TDS imaging technique is potentially a promising technique to measure the doping concentration as well as other optical properties (such as the refractive index and permittivity) of the doped Si wafer.

  9. Electrical properties of undoped and doped MOVPE-grown InAsSb

    CSIR Research Space (South Africa)

    Krug, T

    2006-01-01

    Full Text Available Strong surface inversion usually leads to deceptive Hall measurements by reflecting typical n-type behaviour for p-type samples, especially at very low doping concentrations. A two-layer model is presented which can potentially be used to extract...

  10. Inhibitory effect of aniracetam on N-type calcium current in acutely isolated rat neuronal cells.

    Science.gov (United States)

    Koike, H; Saito, H; Matsuki, N

    1993-04-01

    Effects of aniracetam on whole-cell calcium currents were studied in acutely isolated neuronal cells from postnatal rat ventromedial hypothalamus. There were three types of inward calcium currents, one low-threshold transient current and two high-threshold sustained currents. The nicardipine sensitive L-type current was activated at -20 mV or more depolarized potentials, and the omega-conotoxin sensitive N-type current was recorded at more positive potentials than the L-type. Aniracetam inhibited the N-type current in a dose-dependent manner without affecting the other two types of calcium currents. The effect appeared soon after the addition and lasted for several minutes during washing. Since the N-type current is thought to regulate the release of transmitters, the inhibitory effect may contribute to the nootropic property of aniracetam by modifying the neurotransmission.

  11. Magnéli oxides as promising n-type thermoelectrics

    Directory of Open Access Journals (Sweden)

    Gregor Kieslich

    2014-10-01

    Full Text Available The discovery of a large thermopower in cobalt oxides in 1997 lead to a surge of interest in oxides for thermoelectric application. Whereas conversion efficiencies of p-type oxides can compete with non-oxide materials, n-type oxides show significantly lower thermoelectric performances. In this context so-called Magnéli oxides have recently gained attention as promising n-type thermoelectrics. A combination of crystallographic shear and intrinsic disorder lead to relatively low thermal conductivities and metallic-like electrical conductivities in Magnéli oxides. Current peak-zT values of 0.3 around 1100 K for titanium and tungsten Magnéli oxides are encouraging for future research. Here, we put Magnéli oxides into context of n-type oxide thermoelectrics and give a perspective where future research can bring us.

  12. Electrical tuning of the band alignment and magnetoconductance in an n-type ferromagnetic semiconductor (In,Fe)As-based spin-Esaki diode

    Science.gov (United States)

    Anh, Le Duc; Hai, Pham Nam; Tanaka, Masaaki

    2018-03-01

    We report a strong bias dependence of the magnetoconductance (MC) of a spin-Esaki diode composed of n+-type ferromagnetic semiconductor (FMS) (In,Fe)As and p+-type Be doped InAs grown on a p+-InAs (001) substrate by molecular beam epitaxy. When the bias voltage V is increased above 450 mV in the forward bias, we found that the MC, measured at 3.5 K under a magnetic field H of 1 T in the in-plane [110] direction, changes its sign from positive to negative and its magnitude rises rapidly from 0.5% at V fluid model, we explain both the magnitude and the anisotropy of the MC based on the evolution of the spin-Esaki diode's band profile with V. This analysis provides insights into the density of states and spin-polarization of the conduction band and the Fe-related impurity band in n-type FMS (In,Fe)As.

  13. Colossal change in thermopower with temperature-driven p-n-type conduction switching in La x Sr2-x TiFeO6 double perovskites

    Science.gov (United States)

    Roy, Pinku; Maiti, Tanmoy

    2018-02-01

    Double perovskite materials have been studied in detail by many researchers, as their magnetic and electronic properties can be controlled by the substitution of alkaline earth metals or lanthanides in the A site and transition metals in the B site. Here we report the temperature-driven, p-n-type conduction switching assisted, large change in thermopower in La3+-doped Sr2TiFeO6-based double perovskites. Stoichiometric compositions of La x Sr2-x TiFeO6 (LSTF) with 0  ⩽  x  ⩽  0.25 were synthesized by the solid-state reaction method. Rietveld refinement of room-temperature XRD data confirmed a single-phase solid solution with cubic crystal structure and Pm\\bar{3}m space group. From temperature-dependent electrical conductivity and Seebeck coefficient (S) studies it is evident that all the compositions underwent an intermediate semiconductor-to-metal transition before the semiconductor phase reappeared at higher temperature. In the process of semiconductor-metal-semiconductor transition, LSTF compositions demonstrated temperature-driven p-n-type conduction switching behavior. The electronic restructuring which occurs due to the intermediate metallic phase between semiconductor phases leads to the colossal change in S for LSTF oxides. The maximum drop in thermopower (ΔS ~ 2516 µV K-1) was observed for LSTF with x  =  0.1 composition. Owing to their enormous change in thermopower of the order of millivolts per kelvin, integrated with p-n-type resistance switching, these double perovskites can be used for various high-temperature multifunctional device applications such as diodes, sensors, switches, thermistors, thyristors, thermal runaway monitors etc. Furthermore, the conduction mechanisms of these oxides were explained by the small polaron hopping model.

  14. Doping the Copper-Oxygen Planes with Electrons: The View with Photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Armitage, Norman P.

    2002-03-07

    The undoped parent compounds of high-temperature cuprate superconductors are known to be antiferromagnetic Mott insulators. As the CuO{sub 2} planes are doped with charge carriers, the antiferromagnetic phase subsides and superconductivity emerges. The symmetry, or the lack thereof, between doping with electrons (n-type) or holes (p-type) has important theoretical implications as most models implicitly assume symmetry. However, most of what we know about these superconductors comes from experiments performed on p-type materials. The much fewer number of measurements from n-type compounds suggest that there may be both commonalities and differences between the two sides of the phase diagram. This issue of electron/hole symmetry has not been seriously discussed, perhaps, because the experimental database of n-type results is very limited.

  15. Doped nanostructured zinc oxide films grown by electrodeposition.

    Science.gov (United States)

    Donderis, V; Orozco, J; Cembrero, J; Curiel-Esparza, J; Damonte, L C; Hernández-Fenollosa, M A

    2010-02-01

    ZnO thin films doped with either In or Al are n-type oxide materials of interest for application in electronic devices and thin-film solar cells. In this work, the doped ZnO films were electrodeposited at 80 degrees C from an aqueous solution on polycrystalline conductive Indium Tin Oxide covered glass substrates. The incorporation of the dopants into the ZnO film has been verified by energy dispersive X-ray spectrum, X-Ray diffraction and optical transmission analysis. The optical and surface structure properties of the ZnO doped films are strongly affected by the In and Al concentrations in the electrodeposition solution as evidenced by optical transmission and reflection measurements, and scanning electron microscopy.

  16. The investigation of Ce doped ZnO crystal: The electronic, optical and magnetic properties

    Science.gov (United States)

    Wen, Jun-Qing; Zhang, Jian-Min; Qiu, Ze-Gang; Yang, Xu; Li, Zhi-Qin

    2018-04-01

    The electronic, optical and magnetic properties of Ce doped ZnO crystal have been studied by using first principles method. The research of formation energies show that Ce doped ZnO is energetically stable, and the formation energies reduce from 6.25% to 12.5% for Ce molar percentage. The energy band is still direct band gap after Ce doped, and band gap increases with the increase of Cesbnd Ce distance. The Fermi level moves upward into conduction band and the DOS moves to lower energy with the increase of Ce concentration, which showing the properties of n-type semiconductor. The calculated optical properties imply that Ce doped causes a red-shift of absorption peaks, and enhances the absorption of the visible light. The transition from ferromagnetic to antiferromagnetic has been found in Ce doped ZnO.

  17. Study of Nitrogen terminated doped zigzag GNR FET exhibiting negative differential resistance

    Science.gov (United States)

    Gupta, Santosh Kumar; Jaiswal, Girija Nandan

    2015-10-01

    This paper presents the study of Gallium and Aluminum doped Nitrogen terminated zigzag Graphene Nano Ribbon (GNR) FET with high-k dielectric. The GNR FET structure has been designed and simulated using Quantumwise Atomistix Toolkit software package. The presented GNR FET with n-type (Nitrogen doped) electrodes and p-type (Gallium or Aluminum doped) scattering region are simulated and analyzed using Density Functional Theory combined with NEGF formalism and Device Density of States (DDOS). The device shows a negative differential resistance phenomenon which can be controlled by the gate of the zigzag GNR FET. It is found that doping of Gallium and Aluminum in scattering region provides higher drain current, higher ION/IOFF and IP/IV ratios as compared to that of Boron doped zigzag GNR FET. The potential applications of the device are in logical, high frequency, and memory devices.

  18. Structural, morphological, optical and electrical properties of spray deposited lithium doped CdO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Velusamy, P.; Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in [Crystal Growth and Thin Films Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli-620 024, Tamil Nadu (India); Ramamurthi, K. [Crystal Growth and Thin Films Laboratory, Department of Physics and Nanotechnology, Faculty of Engineering and Technology, SRM University, Kattankulathur – 603 203, Tamil Nadu (India)

    2016-05-23

    In the present work, CdO and Li doped CdO thin films were deposited on microscopic glass substrates at 300°C by a spray pyrolysis experimental setup. The deposited CdO and Li doped CdO thin films were subjected to XRD, SEM, UV-VIS spectroscopy and Hall measurement analyses. XRD studies revealed the polycrystalline nature of the deposited films and confirmed that the deposited CdO and Li doped CdO thin films belong to cubic crystal system. The Scanning electron microscopy analysis revealed the information on shape of CdO and Li doped CdO films. Electrical study reveals the n-type semiconducting nature of CdO and the optical band gap is varied between 2.38 and 2.44 eV, depending on the Li doping concentrations.

  19. Simulation study on single event burnout in linear doping buffer layer engineered power VDMOSFET

    International Nuclear Information System (INIS)

    Jia Yunpeng; Su Hongyuan; Hu Dongqing; Wu Yu; Jin Rui

    2016-01-01

    The addition of a buffer layer can improve the device's secondary breakdown voltage, thus, improving the single event burnout (SEB) threshold voltage. In this paper, an N type linear doping buffer layer is proposed. According to quasi-stationary avalanche simulation and heavy ion beam simulation, the results show that an optimized linear doping buffer layer is critical. As SEB is induced by heavy ions impacting, the electric field of an optimized linear doping buffer device is much lower than that with an optimized constant doping buffer layer at a given buffer layer thickness and the same biasing voltages. Secondary breakdown voltage and the parasitic bipolar turn-on current are much higher than those with the optimized constant doping buffer layer. So the linear buffer layer is more advantageous to improving the device's SEB performance. (paper)

  20. Acceptor-modulated optical enhancements and band-gap narrowing in ZnO thin films

    Directory of Open Access Journals (Sweden)

    Ali Hassan

    2018-03-01

    Full Text Available Fermi-Dirac distribution for doped semiconductors and Burstein-Moss effect have been correlated first time to figure out the conductivity type of ZnO. Hall Effect in the Van der Pauw configuration has been applied to reconcile our theoretical estimations which evince our assumption. Band-gap narrowing has been found in all p-type samples, whereas blue Burstein-Moss shift has been recorded in the n-type films. Atomic Force Microscopic (AFM analysis shows that both p-type and n-type films have almost same granular-like structure with minor change in average grain size (∼ 6 nm to 10 nm and surface roughness rms value 3 nm for thickness ∼315 nm which points that grain size and surface roughness did not play any significant role in order to modulate the conductivity type of ZnO. X-ray diffraction (XRD, Energy Dispersive X-ray Spectroscopy (EDS and X-ray Photoelectron Spectroscopy (XPS have been employed to perform the structural, chemical and elemental analysis. Hexagonal wurtzite structure has been observed in all samples. The introduction of nitrogen reduces the crystallinity of host lattice. 97% transmittance in the visible range with 1.4 × 107 Ω-1cm-1 optical conductivity have been detected. High absorption value in the ultra-violet (UV region reveals that NZOs thin films can be used to fabricate next-generation high-performance UV detectors.

  1. Acceptor-modulated optical enhancements and band-gap narrowing in ZnO thin films

    Science.gov (United States)

    Hassan, Ali; Jin, Yuhua; Irfan, Muhammad; Jiang, Yijian

    2018-03-01

    Fermi-Dirac distribution for doped semiconductors and Burstein-Moss effect have been correlated first time to figure out the conductivity type of ZnO. Hall Effect in the Van der Pauw configuration has been applied to reconcile our theoretical estimations which evince our assumption. Band-gap narrowing has been found in all p-type samples, whereas blue Burstein-Moss shift has been recorded in the n-type films. Atomic Force Microscopic (AFM) analysis shows that both p-type and n-type films have almost same granular-like structure with minor change in average grain size (˜ 6 nm to 10 nm) and surface roughness rms value 3 nm for thickness ˜315 nm which points that grain size and surface roughness did not play any significant role in order to modulate the conductivity type of ZnO. X-ray diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS) have been employed to perform the structural, chemical and elemental analysis. Hexagonal wurtzite structure has been observed in all samples. The introduction of nitrogen reduces the crystallinity of host lattice. 97% transmittance in the visible range with 1.4 × 107 Ω-1cm-1 optical conductivity have been detected. High absorption value in the ultra-violet (UV) region reveals that NZOs thin films can be used to fabricate next-generation high-performance UV detectors.

  2. Fabrication of n-type Si nanostructures by direct nanoimprinting with liquid-Si ink

    Science.gov (United States)

    Takagishi, Hideyuki; Masuda, Takashi; Yamazaki, Ken; Shimoda, Tatsuya

    2018-01-01

    Nanostructures of n-type amorphous silicon (a-Si) and polycrystalline silicon (poly-Si) with a height of 270 nm and line widths of 110-165 nm were fabricated directly onto a substrate through a simple imprinting process that does not require vacuum conditions or photolithography. The n-type Liquid-Si ink was synthesized via photopolymerization of cyclopentasilane (Si5H10) and white phosphorus (P4). By raising the temperature from 160 °C to 200 °C during the nanoimprinting process, well-defined angular patterns were fabricated without any cracking, peeling, or deflections. After the nanoimprinting process, a-Si was produced by heating the nanostructures at 400°C-700 °C, and poly-Si was produced by heating at 800 °C. The dopant P diffuses uniformly in the Si films, and its concentration can be controlled by varying the concentration of P4 in the ink. The specific resistance of the n-type poly-Si pattern was 7.0 × 10-3Ω ṡ cm, which is comparable to the specific resistance of flat n-type poly-Si films.

  3. N-type self-assembled monolayer field-effect transistors

    NARCIS (Netherlands)

    Ringk, A.; Li, X.; Gholamrezaie, F.; Smits, E.C.P.; Neuhold, A.; Moser, A.; Gelinck, G.H.; Resel, R.; Leeuw, D.M. de; Strohriegl, P.

    2012-01-01

    Within this work we present the synthesis and applications of a novel material designed for n-type self-assembled monolayer field-effect transistors (SAMFETs). Our novel perylene bisimide based molecule was obtained in six steps and is functionalized with a phosphonic acid linker which enables a

  4. Morphological and optical properties of n-type porous silicon: effect ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 39; Issue 7. Morphological and optical properties of n-type porous silicon: effect of etching current density. M DAS D SARKAR. Volume 39 Issue 7 ... Calculated crystallite size shows decreasing trend with increasing J value. The optical properties of these samples have ...

  5. Nitrogen-doped graphene sheets grown by chemical vapor deposition: synthesis and influence of nitrogen impurities on carrier transport.

    Science.gov (United States)

    Lu, Yu-Fen; Lo, Shun-Tsung; Lin, Jheng-Cyuan; Zhang, Wenjing; Lu, Jing-Yu; Liu, Fan-Hung; Tseng, Chuan-Ming; Lee, Yi-Hsien; Liang, Chi-Te; Li, Lain-Jong

    2013-08-27

    A significant advance toward achieving practical applications of graphene as a two-dimensional material in nanoelectronics would be provided by successful synthesis of both n-type and p-type doped graphene. However, reliable doping and a thorough understanding of carrier transport in the presence of charged impurities governed by ionized donors or acceptors in the graphene lattice are still lacking. Here we report experimental realization of few-layer nitrogen-doped (N-doped) graphene sheets by chemical vapor deposition of organic molecule 1,3,5-triazine on Cu metal catalyst. When reducing the growth temperature, the atomic percentage of nitrogen doping is raised from 2.1% to 5.6%. With increasing doping concentration, N-doped graphene sheet exhibits a crossover from p-type to n-type behavior accompanied by a strong enhancement of electron-hole transport asymmetry, manifesting the influence of incorporated nitrogen impurities. In addition, by analyzing the data of X-ray photoelectron spectroscopy, Raman spectroscopy, and electrical measurements, we show that pyridinic and pyrrolic N impurities play an important role in determining the transport behavior of carriers in our N-doped graphene sheets.

  6. Doped carbon nanostructure field emitter arrays for infrared imaging

    Science.gov (United States)

    Korsah, Kofi [Knoxville, TN; Baylor, Larry R [Farragut, TN; Caughman, John B [Oak Ridge, TN; Kisner, Roger A [Knoxville, TN; Rack, Philip D [Knoxville, TN; Ivanov, Ilia N [Knoxville, TN

    2009-10-27

    An infrared imaging device and method for making infrared detector(s) having at least one anode, at least one cathode with a substrate electrically connected to a plurality of doped carbon nanostructures; and bias circuitry for applying an electric field between the anode and the cathode such that when infrared photons are adsorbed by the nanostructures the emitted field current is modulated. The detectors can be doped with cesium to lower the work function.

  7. A first principle study of phosphorous doped graphyne

    Science.gov (United States)

    Deb, Jyotirmoy; Paul, Debolina; Sarkar, Utpal

    2017-05-01

    Based on density functional theory (DFT) calculation with generalized gradient approximation (GGA), we have investigated the effect of doping by phosphorous (P) atom at ring and chain position on the electronic properties of graphyne. The stability of the P-doped graphyne system has been determined on the basis of cohesive energy. Doping at chain position shows the possibility of modulating its band gap which might be useful for nano-electronics application. The surprising change from semiconducting to metallic behavior when P atom is placed at ring position of graphyne might be utilized in electronics for the fabrication of metal-semiconductor interfaces and also as an electrode in batteries.

  8. Intrinsic and extrinsic doping of ZnO and ZnO alloys

    Science.gov (United States)

    Ellmer, Klaus; Bikowski, André

    2016-10-01

    In this article the doping of the oxidic compound semiconductor ZnO is reviewed with special emphasis on n-type doping. ZnO naturally exhibits n-type conductivity, which is used in the application of highly doped n-type ZnO as a transparent electrode, for instance in thin film solar cells. For prospective application of ZnO in other electronic devices (LEDs, UV photodetectors or power devices) p-type doping is required, which has been reported only minimally. Highly n-type doped ZnO can be prepared by doping with the group IIIB elements B, Al, Ga, and In, which act as shallow donors according to the simple hydrogen-like substitutional donor model of Bethe (1942 Theory of the Boundary Layer of Crystal Rectifiers (Boston, MA: MIT Rad Lab.)). Group IIIA elements (Sc, Y, La etc) are also known to act as shallow donors in ZnO, similarly explainable by the shallow donor model of Bethe. Some reports showed that even group IVA (Ti, Zr, Hf) and IVB (Si, Ge) elements can be used to prepare highly doped ZnO films—which, however, can no longer be explained by the simple hydrogen-like substitutional donor model. More probably, these elements form defect complexes that act as shallow donors in ZnO. On the other hand, group V elements on oxygen lattice sites (N, P, As, and Sb), which were viewed for a long time as typical shallow acceptors, behave instead as deep acceptors, preventing high hole concentrations in ZnO at room temperature. Also, ‘self’-compensation, i.e. the formation of a large number of intrinsic donors at high acceptor concentrations seems to counteract the p-type doping of ZnO. At donor concentrations above about 1020 cm-3, the electrical activation of the dopant elements is often less than 100%, especially in polycrystalline thin films. Reasons for the electrical deactivation of the dopant atoms are (i) the formation of dopant-defect complexes, (ii) the compensation of the electrons by acceptors (Oi, VZn) or (iii) the formation of secondary phases, for

  9. Strain engineering of magnetic state in vacancy-doped phosphorene

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Jie [Hunan Provincial Key Laboratory of Micro–Nano Energy Materials and Devices, Xiangtan University, Xiangtan 411105, Hunan (China); Zhang, Chunxiao, E-mail: zhangchunxiao@xtu.edu.cn [Hunan Provincial Key Laboratory of Micro–Nano Energy Materials and Devices, Xiangtan University, Xiangtan 411105, Hunan (China); Li, Jin [Hunan Provincial Key Laboratory of Micro–Nano Energy Materials and Devices, Xiangtan University, Xiangtan 411105, Hunan (China); Guo, Zhixin [Department of Physics, Xiangtan University, Xiangtan 411105, Hunan (China); Xiao, Huaping, E-mail: hpxiao@xtu.edu.cn [Hunan Provincial Key Laboratory of Micro–Nano Energy Materials and Devices, Xiangtan University, Xiangtan 411105, Hunan (China); Zhong, Jianxin [Hunan Provincial Key Laboratory of Micro–Nano Energy Materials and Devices, Xiangtan University, Xiangtan 411105, Hunan (China)

    2016-09-23

    Inducing and manipulating the magnetism in two-dimensional materials play an important role for the development of the next-generation spintronics. In this letter, the effects of the biaxial strain on magnetic properties of vacancy-doped phosphorene are investigated using first-principles calculation. We find although only SV956 doping induces magnetism for unstrained phosphorene, the biaxial strain induces nonzero magnetic moment for SV5566 and DVa doped phosphorene. The biaxial strain also modulates the magnetic state for SV956, SV5566 and DVa doped phosphorene. The local magnetic moment derives from the spin polarization of the dangling bonds near the vacancy. The biaxial strain influences the local bonding configuration near the vacancy which determines the presence of dangling bonds, and then modulates the magnetic state. Our findings promise the synergistic effect of strain engineering and vacancy decoration is an effective method for the operation of phosphorene-based spintronic devices. - Highlights: • Investigation of the magnetic moment of vacancy-doped phosphorene by DFT calculation. • The modulation of the magnetic moment by the biaxial strain. • The analysis of the bonding configuration with the biaxial strain. • The analysis of the electronic structures to explain the evolution of the magnetic moment. • The effects of the biaxial strain on the band gap and doping levels.

  10. Doping control in sport

    DEFF Research Database (Denmark)

    Overbye, Marie Birch

    2016-01-01

    Doping testing is a key component enforced by anti-doping authorities to detect and deter doping in sport. Policy is developed to protect athletes' right to participate in doping-free sport; and testing is a key tool to secure this right. Accordingly, athletes' responses to anti-doping efforts.......e., the efforts of stakeholders involved in testing) in their own sport both nationally and worldwide. Moreover, it seeks to identify whether specific factors such as previous experience of testing and perceived proximity of doping have an impact on athletes' perceptions of the testing system. The study comprises...... a web-based questionnaire (N = 645; response rate 43%) and uses qualitative findings to elaborate on and explain quantitative results. Results showed that two-thirds of the athletes reported the national testing programme in their sport to be appropriate. A majority of the athletes who had an opinion...

  11. Raman and X-Ray photoelectron spectroscopic studies of graphene devices for identification of doping

    Science.gov (United States)

    Aydogan Gokturk, Pinar; Kakenov, Nurbek; Kocabas, Coskun; Suzer, Sefik

    2017-12-01

    Tunability of electronic properties of graphene is one of the most promising properties to integrate it to high efficiency devices in the field of electronics. Here we demonstrate the substrate induced doping of CVD graphene devices using polymers with different functional groups. Both X-Ray secondary electron cut-off and Raman spectra confirm p-type doping of a PVC-Graphene film when compared to a PMMA-Graphene one. We also systematically analyzed the reversible doping effect of acid-base exposure and UV illumination to further dope/undope the polymer supported graphene devices. The shifts in the Raman 2D band towards lower and then to higher wavenumbers, with sequential exposure to ammonia and hydrochloric acid vapors, suggest n-type doing and restoration of graphene to its original state. Finally, the n-type doping with UV irradiation on half-covered samples was utilized and shown by both XPS and Raman to create two regions with different electronic properties and resistances. These type of controlled and reversible doping routes offer new paths for electronic devices especially towards fabricating graphene p-n junctions.

  12. Polarization induced doped transistor

    Science.gov (United States)

    Xing, Huili; Jena, Debdeep; Nomoto, Kazuki; Song, Bo; Zhu, Mingda; Hu, Zongyang

    2016-06-07

    A nitride-based field effect transistor (FET) comprises a compositionally graded and polarization induced doped p-layer underlying at least one gate contact and a compositionally graded and doped n-channel underlying a source contact. The n-channel is converted from the p-layer to the n-channel by ion implantation, a buffer underlies the doped p-layer and the n-channel, and a drain underlies the buffer.

  13. Asymmetric electron and hole transport in a high-mobility n-type conjugated polymer

    NARCIS (Netherlands)

    Wetzelaer, Gert-Jan A. H.; Kuik, Martijn; Olivier, Yoann; Lemaur, Vincent; Cornil, Jerome; Fabiano, Simone; Loi, Maria Antonietta; Blom, Paul W. M.; Cornil, Jérôme

    2012-01-01

    Electron-and hole-transport properties of the n-type copolymer poly{[N, N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-dithiophene)} [P(NDI2OD-T2), PolyeraActivInk (TM) N2200] are investigated. Electron- and hole-only devices with Ohmic contacts are

  14. Characterization and Reliability of Vertical N-Type Gallium Nitride Schottky Contacts

    Science.gov (United States)

    2016-09-01

    aluminum / gallium arsenide Schottky diodes,” J. Appl. Phys., vol. 69, no. 10, pp. 7142–7145, May, 1991. 80 THIS PAGE INTENTIONALLY LEFT BLANK...EECP equilibrium of electrochemical potential GaAs gallium arsenide GaN gallium nitride HEMT high-electron mobility transistor HF hydrofluoric acid...only one of the mechanisms [8]-[11]. For high mobility n-type Schottky contacts like Si, gallium arsenide (GaAs), and GaN, thermionic emission is

  15. Propagation of surface acoustic waves in n-type GaAs films

    Science.gov (United States)

    Wu, Chhi-Chong; Tsai, Jensan

    1983-05-01

    The effect of nonparabolicity on the amplification of surface acoustic waves in n-type GaAs films is investigated quantum mechanically in the GHz frequency region. Numerical results show that the amplification coefficient for the nonparabolic band structure is enhanced due to the nonlinear nature of the energy band in semiconductors. Moreover, the amplification coefficients in semiconductors depend on the temperature, the electronic screening effect, the frequency of sound waves, the applied electric field, and the thickness of the semiconductor film.

  16. Study of polarization phenomena in n-type CdZnTe

    Czech Academy of Sciences Publication Activity Database

    Elhadidy, Hassan; Dědic, V.; Franc, J.; Grill, R.

    2014-01-01

    Roč. 47, č. 5 (2014), Art. number 055104 ISSN 0022-3727 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068; GA MŠk(CZ) EE2.3.20.0214 Institutional support: RVO:68081723 Keywords : n-type CZT * polarization * electron de-trapping * Pockels effect Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.721, year: 2014

  17. Radiation Effects of n-type, Low Resistivity, Spiral Silicon Drift Detector Hybrid Systems

    International Nuclear Information System (INIS)

    Chen, W.; De Geronimo, G.; Carini, G.A.; Gaskin, J.A.; Keister, J.W.; Li, S.; Li, Z.; Ramsey, B.D.; Siddons, D.P.; Smith, G.C.; Verbitskaya, E.

    2011-01-01

    We have developed a new thin-window, n-type, low-resistivity, spiral silicon drift detector (SDD) array - to be used as an extraterrestrial X-ray spectrometer (in varying environments) for NASA. To achieve low-energy response, a thin SDD entrance window was produced using a previously developed method. These thin-window devices were also produced on lower resistivity, thinner, n-type, silicon material, effectively ensuring their radiation hardness in anticipation of operation in potentially harsh radiation environments (such as found around the Jupiter system). Using the Indiana University Cyclotron Facility beam line RERS1, we irradiated a set of suitable diodes up to 5 Mrad and the latest iteration of our ASICs up to 12 Mrad. Then we irradiated two hybrid detectors consisting of newly, such-produced in-house (BNL) SDD chips bonded with ASICs with doses of 0.25 Mrad and 1 Mrad. Also we irradiated another hybrid detector consisting of previously produced (by KETEK) on n-type, high-resistivity SDD chip bonded with BNL's ASICs with a dose of 1 Mrad. The measurement results of radiated diodes (up to 5 Mrad), ASICs (up to 12 Mrad) and hybrid detectors (up to 1 Mrad) are presented here.

  18. High Mobility of Graphene-Based Flexible Transparent Field Effect Transistors Doped with TiO2 and Nitrogen-Doped TiO2.

    Science.gov (United States)

    Wu, Yu-Hsien; Tseng, Po-Yuan; Hsieh, Ping-Yen; Chou, Hung-Tao; Tai, Nyan-Hwa

    2015-05-13

    Graphene with carbon atoms bonded in a honeycomb lattice can be tailored by doping various species to alter the electrical properties of the graphene for fabricating p-type or n-type field-effect transistors (FETs). In this study, large-area and single-layer graphene was grown on electropolished Cu foil using the thermal chemical vapor deposition method; the graphene was then transferred onto a poly(ethylene terephthalate) (PET) substrate to produce flexible, transparent FETs. TiO2 and nitrogen-doped TiO2 (N-TiO2) nanoparticles were doped on the graphene to alter its electrical properties, thereby enhancing the carrier mobility and enabling the transistors to sense UV and visible light optically. The results indicated that the electron mobility of the graphene was 1900 cm(2)/(V·s). Dopings of TiO2 and N-doped TiO2 (1.4 at. % N) lead to n-type doping effects demonstrating extremely high carrier mobilities of 53000 and 31000 cm(2)/(V·s), respectively. Through UV and visible light irradiation, TiO2 and N-TiO2 generated electrons and holes; the generated electrons transferred to graphene channels, causing the FETs to exhibit n-type electric behavior. In addition, the Dirac points of the graphene recovered to their original state within 5 min, confirming that the graphene-based FETs were photosensitive to UV and visible light. In a bending state with a radius of curvature greater than 2.0 cm, the carrier mobilities of the FETs did not substantially change, demonstrating the application possibility of the fabricated graphene-based FETs in photosensors.

  19. Phonon-electron interactions in the two-dimensional electron gas in InGaAs-InAlAs modulation-doped field-effect transistor structures studied by Raman scattering

    Science.gov (United States)

    Maslar, J. E.; Dorsten, J. F.; Bohn, P. W.; Agarwala, S.; Adesida, I.; Caneau, C.; Bhat, R.

    1993-10-01

    Raman scattering by coupled longitudinal optic phonons and two-dimensional electron gas electrons in In0.53Ga0.47As-In0.52Al0.48As δ-doped heterostructures provides a powerful probe of electronic properties in these In-based structures. The two highest frequency modes, of the three coupled electron-phonon modes expected in this system, were observed, with the highest frequency mode being identified in InGaAs-based systems. The large dispersion of this mode makes it a particularly sensitive probe for changes in such properties as carrier concentration and subband energy. For structures with higher carrier concentrations coupling of the longitudinal optic phonon to multiple electron intersubband transitions is resolved. These measurements are particularly useful for heavily doped structures for which room-temperature Hall measurements cannot distinguish channel electrons from those in parallel conduction paths.

  20. VLSI-compatible carbon nanotube doping technique with low work-function metal oxides.

    Science.gov (United States)

    Suriyasena Liyanage, Luckshitha; Xu, Xiaoqing; Pitner, Greg; Bao, Zhenan; Wong, H-S Philip

    2014-01-01

    Single-wall carbon nanotubes (SWCNTs) have great potential to become the channel material for future high-speed transistor technology. However, as-made carbon nanotube field effect transistors (CNFETs) are p-type in ambient, and a consistent and reproducible n-type carbon nanotube (CNT) doping technique has yet to be realized. In addition, for very large scale integration (VLSI) of CNT transistors, it is imperative to use a solid-state method that can be applied on the wafer scale. Herein we present a novel, VLSI-compatible doping technique to fabricate n-type CNT transistors using low work-function metal oxides as gate dielectrics. Using this technique we demonstrate wafer-scale, aligned CNT transistors with yttrium oxide (Y2Ox) gate dielectrics that exhibit n-type behavior with Ion/Ioff of 10(6) and inverse subthreshold slope of 95 mV/dec. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) analyses confirm that slow (∼1 Å/s) evaporation of yttrium on the CNTs can form a smooth surface that provides excellent wetting to CNTs. Further analysis of the yttrium oxide gate dielectric using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques revealed that partially oxidized elemental yttrium content increases underneath the surface where it acts as a reducing agent on nanotubes by donating electrons that gives rise to n-type doping in CNTs. We further confirm the mechanism for this technique with other low work-function metals such as lanthanum (La), erbium (Er), and scandium (Sc) which also provide similar CNT NFET behavior after transistor fabrication. This study paves the way to exploiting a wide range of materials for an effective n-type carbon nanotube transistor for a complementary (p- and n-type) transistor technology.

  1. Material properties of LPCVD processed n-type polysilicon passivating contacts and its application in PERPoly industrial bifacial solar cells

    NARCIS (Netherlands)

    Stodolny, Maciej K.; Anker, John; Geerligs, Bart L.J.; Janssen, Gaby J.M.; van de Loo, Bas W.H.; Melskens, Jimmy; Santbergen, Rudi; Isabella, Olindo; Schmitz, Jurriaan; Lenes, Martijn; Luchies, Jan Marc; Kessels, Wilhelmus M.M.; Romijn, Ingrid

    2017-01-01

    We present a detailed material study of n+-type polysilicon (polySi) and its application as a carrier selective rear contact in a bifacial n-type solar cell comprising fire-through screen-printed metallization and 6" Cz wafers. The cells were manufactured with low-cost industrial process steps

  2. [Doping and sports].

    Science.gov (United States)

    Lippi, G; Guidi, G

    1999-09-01

    Doping is widely known as the use of banned substances and practices by athletes in an attempt to improve sporting performances. The term doping likely derives from "dope", an ancient expression referred to a primitive alcoholic drink that was used as a stimulant in South African ceremonial dances; gradually, the term was extended and finally adopted his current significance. There are at least two essential reasons to support the fight against doping: the potential harmful effects on athletes and the depth corruption of the fair competition. An exhaustive list of banned substances and methods has been drawn by the International Olympic Committee and further accepted by other International Sport Authorities and Federations. This list, regularly updated, is basically divided into doping substances (stimulants, narcotic analgesics, anabolic agents, diuretics, peptide and glycoprotein hormones and analogues), doping methods (blood doping, pharmacological, chemical and physical manipulation) and drugs subjected to certain restrictions (alcohol, marijuana, local anesthetics, corticosteroids and beta-blockers). Although there might be some medical conditions, which could legitimate the need of these substances or methods, there is no place for their use in sport. Thus, an athlete's consume of any of these substances or methods will result in disqualification. Aim of the present review is to provide a synthetic description of both the desirable effects and the potentially harmful consequences of the use of some of the major doping substances and methods.

  3. Doped graphene supercapacitors

    Science.gov (United States)

    Ashok Kumar, Nanjundan; Baek, Jong-Beom

    2015-12-01

    Heteroatom-doped graphitic frameworks have received great attention in energy research, since doping endows graphitic structures with a wide spectrum of properties, especially critical for electrochemical supercapacitors, which tend to complement or compete with the current lithium-ion battery technology/devices. This article reviews the latest developments in the chemical modification/doping strategies of graphene and highlights the versatility of such heteroatom-doped graphitic structures. Their role as supercapacitor electrodes is discussed in detail. This review is specifically focused on the concept of material synthesis, techniques for electrode fabrication and metrics of performance, predominantly covering the last four years. Challenges and insights into the future research and perspectives on the development of novel electrode architectures for electrochemical supercapacitors based on doped graphene are also discussed.

  4. To dope or not to dope

    DEFF Research Database (Denmark)

    Overbye, Marie Birch; Knudsen, Mette Lykke; Pfister, Gertrud Ursula

    2013-01-01

    tAim: This study aims to examine the circumstances which athletes say affect their (hypothetical) consid-erations of whether to dope or not and explore the differences between athletes of different gender, ageand sport type.Methods: 645 elite athletes (mean age: 22.12; response rate: 43%) represe......tAim: This study aims to examine the circumstances which athletes say affect their (hypothetical) consid-erations of whether to dope or not and explore the differences between athletes of different gender, ageand sport type.Methods: 645 elite athletes (mean age: 22.12; response rate: 43...... a more decisive factor. Top incentives were related toqualified medical assistance, improved health or faster recovery from injury, the low risk of being caughtand the threat posed to an elite career.Conclusions: Our results reveal that numerous circumstances affect athletes’ thoughts on doping...

  5. High rate performance of virus enabled 3D n-type Si anodes for lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Chen Xilin [Department of Chemical and Biomolecular Engineering, University of Maryland College Park, MD 20742 (United States); Gerasopoulos, Konstantinos [Department of Materials Science and Engineering, Institute for Systems Research, Department of Electrical and Computer Engineering, University of Maryland College Park, MD 20742 (United States); Guo Juchen [Department of Chemical and Biomolecular Engineering, University of Maryland College Park, MD 20742 (United States); Brown, Adam [Institute for Bioscience and Biotechology Research, Department of Plant Science and Landscape Architecture, University of Maryland College Park, MD 20742 (United States); Ghodssi, Reza [Department of Materials Science and Engineering, Institute for Systems Research, Department of Electrical and Computer Engineering, University of Maryland College Park, MD 20742 (United States); Culver, James N. [Institute for Bioscience and Biotechology Research, Department of Plant Science and Landscape Architecture, University of Maryland College Park, MD 20742 (United States); Wang Chunsheng, E-mail: cswang@umd.edu [Department of Chemical and Biomolecular Engineering, University of Maryland College Park, MD 20742 (United States)

    2011-05-30

    Research highlights: > A novel three-dimensional Tobacco mosaic virus (TMV) assembled n-type silicon anode is reported for the first time. > The combination of the large surface area conferred by the virus-enabled 3D Ni/TMV1cys current collector with the high electric conductivity of n-type Si rods results in excellent cyclic stability and rate capability for the core-shell n-type Si/Ni/TMV1cys anodes. > Electrochemical impedance spectroscopy reveals that the high electronic conductivity of n-type Si significantly reduces charge transfer resistance, thus even at high C-rates the capacity of the n-type Si is increased to almost 1000 mAh/g compared to undoped Si. - Abstract: A patterned 3D Si anode is fabricated by physical vapor deposition of n-type Si on a self-assembled TMV1cys-structured nickel current collector. The combination of the large surface area conferred by the virus-enabled 3D Ni/TMV1cys current collector with the high electric conductivity of n-type Si rods results in excellent cyclic stability and rate capability for the core-shell n-type Si/Ni/TMV1cys anodes. Electrochemical impedance spectroscopy reveals that the high electronic conductivity of n-type Si significantly reduces charge transfer resistance, thus even at high current densities the capacity of the n-type Si is increased to almost 630 mAh/g compared to undoped Si.

  6. Subband structure comparison between n- and p- type double delta-doped Ga As quantum wells

    International Nuclear Information System (INIS)

    Rodriguez V, I.; Gaggero S, L.M.

    2004-01-01

    We compute the electron level structure (n-type) and the hole subband structure (p-type) of double -doped GaAs (DDD) quantum wells, considering exchange effects. The Thomas-Fermi (TF), and Thomas-Fermi-Dirac (TFD) approximations have been applied in order to describe the bending of the conduction and valence band, respectively. The electron and the hole subband structure study indicates that exchange effects are more important in p-type DDD quantum wells than in n-type DDD Also our results agree with the experimental data available. (Author) 33 refs., 2 tabs., 5 figs

  7. N-Doped Hybrid Graphene and Boron Nitride Armchair Nanoribbons As Nonmagnetic Semiconductors with Widely Tunable Electronic Properties

    Science.gov (United States)

    Habibpour, Razieh; Kashi, Eslam; Vazirib, Raheleh

    2018-03-01

    The electronic and chemical properties of N-doped hybrid graphene and boron nitride armchair nanoribbons (N-doped a-GBNNRs) in comparison with graphene armchair nanoribbon (pristine a-GNR) and hybrid graphene and boron nitride armchair nanoribbon (C-3BN) are investigated using the density functional theory method. The results show that all the mentioned nanoribbons are nonmagnetic direct semiconductors and all the graphitic N-doped a-GBNNRs are n-type semiconductors while the rest are p-type semiconductors. The N-doped graphitic 2 and N-doped graphitic 3 structures have the lowest work function and the highest number of valence electrons (Lowdin charges) which confirms that they are effective for use in electronic device applications.

  8. The effect of doping on the energetics and quantum conductance in graphene nanoribbons with a metallocene adsorbate

    Science.gov (United States)

    Kang, Hong Seok; Pramanik, Anup

    2011-09-01

    Based on a PBE-D2 calculation that empirically includes van der Waals interactions to the standard GGA approximation of Perdew, Berke, and Ernzerhof, we have investigated the adsorption of ferrocene or ruthenocene on pristine and X-doped graphene (GrS) or graphene nanoribbons (GNRs), where X (=B or N) is a p-type or n-type heteroatom. First, we find that van der Waals interactions play a dominant role in the adsorption. Second, we find that metallocene adsorption on doped GNRs introduces different effects in the low-bias conductance, not far from the linear response regime, of GNRs depending upon the doping type. Adsorption on undoped or p-type GNRs brings about a slight reduction in conductance due to an introduction of quasi-bound states just below the Fermi level. No appreciable reduction is expected in n-type GNRs because those states are introduced far below the Fermi level.

  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. Tunable electronic properties of graphene through controlling bonding configurations of doped nitrogen atoms

    Science.gov (United States)

    Zhang, Jia; Zhao, Chao; Liu, Na; Zhang, Huanxi; Liu, Jingjing; Fu, Yong Qing; Guo, Bin; Wang, Zhenlong; Lei, Shengbin; Hu, Pingan

    2016-06-01

    Single-layer and mono-component doped graphene is a crucial platform for a better understanding of the relationship between its intrinsic electronic properties and atomic bonding configurations. Large-scale doped graphene films dominated with graphitic nitrogen (GG) or pyrrolic nitrogen (PG) were synthesized on Cu foils via a free radical reaction at growth temperatures of 230-300 °C and 400-600 °C, respectively. The bonding configurations of N atoms in the graphene lattices were controlled through reaction temperature, and characterized using Raman spectroscopy, X-ray photoelectron spectroscopy and scanning tunneling microscope. The GG exhibited a strong n-type doping behavior, whereas the PG showed a weak n-type doping behavior. Electron mobilities of the GG and PG were in the range of 80.1-340 cm2 V-1·s-1 and 59.3-160.6 cm2 V-1·s-1, respectively. The enhanced doping effect caused by graphitic nitrogen in the GG produced an asymmetry electron-hole transport characteristic, indicating that the long-range scattering (ionized impurities) plays an important role in determining the carrier transport behavior. Analysis of temperature dependent conductance showed that the carrier transport mechanism in the GG was thermal excitation, whereas that in the PG, was a combination of thermal excitation and variable range hopping.

  11. Designing small molecule polyaromatic p- and n-type semiconductor materials for organic electronics

    KAUST Repository

    Collis, Gavin E.

    2015-12-22

    By combining computational aided design with synthetic chemistry, we are able to identify core 2D polyaromatic small molecule templates with the necessary optoelectronic properties for p- and n-type materials. By judicious selection of the functional groups, we can tune the physical properties of the material making them amenable to solution and vacuum deposition. In addition to solubility, we observe that the functional group can influence the thin film molecular packing. By developing structure-property relationships (SPRs) for these families of compounds we observe that some compounds are better suited for use in organic solar cells, while others, varying only slightly in structure, are favoured in organic field effect transistor devices. We also find that the processing conditions can have a dramatic impact on molecular packing (i.e. 1D vs 2D polymorphism) and charge mobility; this has implications for material and device long term stability. We have developed small molecule p- and n-type materials for organic solar cells with efficiencies exceeding 2%. Subtle variations in the functional groups of these materials produces p- and ntype materials with mobilities higher than 0.3 cm2/Vs. We are also interested in using our SPR approach to develop materials for sensor and bioelectronic applications.

  12. Molecular architecture of the N-type ATPase rotor ring from Burkholderia pseudomallei.

    Science.gov (United States)

    Schulz, Sarah; Wilkes, Martin; Mills, Deryck J; Kühlbrandt, Werner; Meier, Thomas

    2017-04-01

    The genome of the highly infectious bacterium Burkholderia pseudomallei harbors an atp operon that encodes an N-type rotary ATPase, in addition to an operon for a regular F-type rotary ATPase. The molecular architecture of N-type ATPases is unknown and their biochemical properties and cellular functions are largely unexplored. We studied the B. pseudomallei N 1 N o -type ATPase and investigated the structure and ion specificity of its membrane-embedded c-ring rotor by single-particle electron cryo-microscopy. Of several amphiphilic compounds tested for solubilizing the complex, the choice of the low-density, low-CMC detergent LDAO was optimal in terms of map quality and resolution. The cryoEM map of the c-ring at 6.1 Å resolution reveals a heptadecameric oligomer with a molecular mass of ~141 kDa. Biochemical measurements indicate that the c 17 ring is H + specific, demonstrating that the ATPase is proton-coupled. The c 17 ring stoichiometry results in a very high ion-to-ATP ratio of 5.7. We propose that this N-ATPase is a highly efficient proton pump that helps these melioidosis-causing bacteria to survive in the hostile, acidic environment of phagosomes. © 2017 The Authors. Published under the terms of the CC BY 4.0 license.

  13. Unsymmetrically substituted n-type perylene bisimides with liquid crystalline properties

    Energy Technology Data Exchange (ETDEWEB)

    Wicklein, Andre; Thelakkat, Mukundan [Universitaet Bayreuth (Germany). Applied Functional Polymers

    2009-07-01

    Perylene bisimides (PBIs) represent an important class of organic n-type semiconductors exhibiting a relatively high electron affinity among large-band-gap materials. Herein synthesis and characterization of several unsymmetrical N-substituted PBI dyes is presented and the thermotropic behavior, which is strongly affected by the respective N-substituents was investigated. Two different series of highly soluble and fluorescent derivatives have been synthesized: (1) PBIs bearing swallow-tailed alkyl chains, different in size or (2) one swallow-tailed alkyl chain and one branched oligoethylenglycolether. Synthesis of these PBIs is generally feasible by two distinct divergent synthesis approaches. Thermotropic behavior was studied by DSC, POM and XRD measurements. Inherent {pi}-{pi} interactions between cofacially orientated perylene molecules and the elliptic shape of the molecule favor the ordering in columns and self-organized architectures. Among them hexagonal columnar CoIh mesophases, large spherulitic crystals or formation of stable amorphous phases upon rapid cooling from the isotropic phase can be observed. Due to high solubility in organic solvents, film preparation by solution processing is readily feasible. The interesting optical and thermal properties of these compounds allow these organic n-type semiconductors as potential materials for application in organic electronic devices, such as photovoltaics or OFETS.

  14. N-type calcium channel antibody-mediated paraneoplastic limbic encephalitis: a diagnostic challenge.

    Science.gov (United States)

    Kamiya-Matsuoka, Carlos; Blas-Boria, David; Williams, Michelle D; Garciarena, Pedro; Tummala, Sudhakar; Tremont-Lukats, Ivo W

    2014-03-15

    The etiology of encephalitis presents a diagnostic challenge and often remains a mystery. However, current technological advances using antibodies can enable a definitive diagnosis in cases that would previously have been suspected to be idiopathic or viral encephalitis. Our objective is to show that tonsil neuroendocrine carcinoma can present initially as limbic encephalitis mediated by N-type calcium channel antibodies and to highlight the diagnostic confusion before cancer detection. We report a rare case of neuroendocrine cancer presenting as limbic encephalopathy, Lambert-Eaton myasthenic syndrome and neuropathy. The patient was diagnosed and treated at The University of Texas MD Anderson Cancer Center in November 2011. Paraneoplastic limbic encephalitis was diagnosed based on clinical presentation of seizures, short-term memory loss, retrograde amnesia, disorientation, distractibility, and abulia; on the exclusion of brain metastases, CNS infection, stroke, metabolic or nutritional deficits, or medication-related events; and on CSF results with inflammatory findings and an abnormal electroencephalography study that showed seizure activity in the left temporal lobe. Serum paraneoplastic panel was positive for P/Q-type calcium channel antibody and N-type calcium channel antibody. Magnetic resonance imaging of brain was unremarkable. This case highlights limbic encephalitis as an atypical presentation of neuroendocrine cancer. It also illustrates how treatment of the underlying cancer can reverse limbic encephalitis and Lambert-Eaton myasthenic syndrome in a neuroendocrine carcinoma patient even before the paraneoplastic panel becomes negative. Published by Elsevier B.V.

  15. Development of high resolution N-type HPGe coaxial detectors and their applications

    International Nuclear Information System (INIS)

    Wu Shaoyun

    1995-10-01

    The development results of the high resolution N-type HPGe coaxial detectors are reported. The dependence of the reverse V-I L characteristic on the implantation dose of detector outside P + N junction was investigated under the condition of the fixed ion energy, beam intensity, and implantation angle. The experimental results indicate that a good detector can be steadily obtained at the higher implantation dose. When the implantation dose reaches 1.8 x 10 15 B + /cm 2 , the detectors have the ideal reverse V-I L characteristic. The detectors with good shock-proof performance are obtained by means of a fine mounting technology for N-type coaxial detectors. The detectors NCGL-1 and NCGL-2 have been successfully applied to the neutron capture gamma ray spectrum logging over ten drill wells at the coal field and the detector N49TB is used to the measuring system of the radioactive calibration well at the oil field. (10 refs., 6 figs., 2 tabs.)

  16. Transmutation doping and lattice defects in degenerate InSb

    International Nuclear Information System (INIS)

    Gerstenberg, H.; Glaeser, W.

    1990-01-01

    n-type InSb single crystals were irradiated with thermal neutrons below T = 6 K. The Shubnikov-de Haas effect and the resistivity ρ(T = 4.6 K) were measured as a function of the neutron dose and the holding temperature of a subsequent annealing program. The results are discussed in terms of the transport scattering rate and the lifetime of the Landau-levels. They have to be interpreted by means of n-doping due to nuclear reactions and irradiation induced negatively charged defects. Almost complete annealing of the transport parameters can be achieved by heating the samples to T A = 400 K. (author)

  17. Co-doping with antimony to control phosphorous diffusion in germanium

    KAUST Repository

    Tahini, H. A.

    2013-02-15

    In germanium, phosphorous and antimony diffuse quickly and as such their transport must be controlled in order to design efficient n-typed doped regions. Here, density functional theory based calculations are used to predict the influence of double donor co-doping on the migration activation energies of vacancy-mediated diffusion processes. The migration energy barriers for phosphorous and antimony were found to be increased significantly when larger clusters involving two donor atoms and a vacancy were formed. These clusters are energetically stable and can lead to the formation of even larger clusters involving a number of donor atoms around a vacancy, thereby affecting the properties of devices.

  18. Germanium-doped gallium phosphide obtained by neutron irradiation

    Science.gov (United States)

    Goldys, E. M.; Barczynska, J.; Godlewski, M.; Sienkiewicz, A.; Heijmink Liesert, B. J.

    1993-08-01

    Results of electrical, optical, electron spin resonance and optically detected magnetic resonance studies of thermal neutron irradiated and annealed at 800 °C n-type GaP are presented. Evidence is found to support the view that the main dopant introduced via transmutation of GaP, germanium, occupies cation sites and forms neutral donors. This confirms the possibility of neutron transmutation doping of GaP. Simultaneously, it is shown that germanium is absent at cation sites. Presence of other forms of Ge-related defects is deduced from luminescence and absorption data. Some of them are tentatively identified as VGa-GeGa acceptors leading to the self-compensation process. This observation means that the neutron transmutation as a doping method in application to GaP is not as efficient as for Si.

  19. n-type dopants in (001) β-Ga2O3 grown on (001) β-Ga2O3 substrates by plasma-assisted molecular beam epitaxy

    Science.gov (United States)

    Han, Sang-Heon; Mauze, Akhil; Ahmadi, Elaheh; Mates, Tom; Oshima, Yuichi; Speck, James S.

    2018-04-01

    Ge and Sn as n-type dopants in (001) β-Ga2O3 films were investigated using plasma-assisted molecular beam epitaxy. The Ge concentration showed a strong dependence on the growth temperature, whereas the Sn concentration remains independent of the growth temperature. The maximum growth temperature at which a wide range of Ge concentrations (from 1017 to 1020 cm-3) could be achieved was 675 °C while the same range of Sn concentration could be achieved at growth temperature of 750 °C. Atomic force microscopy results revealed that higher growth temperature shows better surface morphology. Therefore, our study reveals a tradeoff between higher Ge doping concentration and high quality surface morphology on (001) β-Ga2O3 films grown by plasma-assisted molecular beam epitaxy. The Ge doped films had an electron mobility of 26.3 cm2 V-1 s-1 at the electron concentration of 6.7 × 1017 cm-3 whereas the Sn doped films had an electron mobility of 25.3 cm2 V-1 s-1 at the electron concentration of 1.1 × 1018 cm-3.

  20. Mechanistic Study on the Solution-Phase n-Doping of 1,3-Dimethyl-2-aryl-2,3-dihydro-1H-benzoimidazole Derivatives

    Science.gov (United States)

    Naab, Benjamin D.; Guo, Song; Olthof, Selina; Evans, Eric G. B.; Wei, Peng; Millhauser, Glenn L.; Kahn, Antoine; Barlow, Stephen; Marder, Seth R.; Bao, Zhenan

    2014-01-01

    The discovery of air-stable n-dopants for organic semiconductor materials has been hindered by the necessity of high-energy HOMOs and the air sensitivity of compounds that satisfy this requirement. One strategy for circumventing this problem is to utilize stable precursor molecules that form the active doping complex in situ during the doping process or in a postdeposition thermal- or photo-activation step. Some of us have reported on the use of 1H-benzimidazole (DMBI) and benzimidazolium (DMBI-I) salts as solution- and vacuum-processable n-type dopant precursors, respectively. It was initially suggested that DMBI dopants function as single-electron radical donors wherein the active doping species, the imidazoline radical, is generated in a postdeposition thermal annealing step. Herein we report the results of extensive mechanistic studies on DMBI-doped fullerenes, the results of which suggest a more complicated doping mechanism is operative. Specifically, a reaction between the dopant and host that begins with either hydride or hydrogen atom transfer and which ultimately leads to the formation of host radical anions is responsible for the doping effect. The results of this research will be useful for identifying applications of current organic n-doping technology and will drive the design of next-generation n-type dopants that are air stable and capable of doping low-electron-affinity host materials in organic devices. PMID:24011269

  1. Phonon mechanism in the most dilute superconductor n-type SrTiO3.

    Science.gov (United States)

    Gor'kov, Lev P

    2016-04-26

    Superconductivity of n-doped SrTiO3, which remained enigmatic for half a century, is treated as a particular case of nonadiabatic phonon pairing. Motivated by experiment, we suggest the existence of the mobility edge at some dopant concentration. The itinerant part of the spectrum consists of three conduction bands filling by electrons successively. Each subband contributes to the superconducting instability and exhibits a gap in its energy spectrum at low temperatures. We argue that superconductivity of n-doped SrTiO3 results from the interaction of electrons with several longitudinal (LO) optical phonons with frequencies much larger than the Fermi energy. Immobile charges under the mobility edge threshold increase the "optical" dielectric constant far above that in clean SrTiO3 placing control on the electron-LO phonon interaction. TC initially grows as density of states at the Fermi surface increases with doping, but the accumulating charges reduce the electrons-polar-phonon interaction by screening the longitudinal electric fields. The theory predicts maxima in the TC-concentration dependence indeed observed experimentally. Having reached a maximum in the third band, the transition temperature finally decreases, rounding out the TC (n) dome, the three maxima with accompanying superconducting gaps emerging consecutively as electrons fill successive bands. This arises from attributes of the LO optical phonon pairing of electrons. The mechanism of LO phonons opens the path to increasing superconducting transition temperature in bulk transition-metal oxides and other polar crystals, and in charged 2D layers at the LaAaO3/SrTiO3 interfaces and on the SrTiO3 substrates.

  2. Application of highly silicon-doped marker layers in the investigation of unintentional doping in GaN on sapphire.

    Science.gov (United States)

    Oliver, R A

    2010-12-01

    To provide a route to the assessment of the impact of inclined facets on unintentional n-type doping during the growth of c-plane GaN on sapphire, thin (100 nm), highly Si-doped (at 10¹⁹ cm⁻³) marker layers have been incorporated into a GaN epitaxial layer grown by a method involving a transition from initial three-dimensional island growth to later, two-dimensional, planar growth. Imaging of the completed epitaxial layer in cross-section by scanning capacitance microscopy reveals the shapes of the islands, which were present during the early stages of growth and the relationship between the facets present and the incorporation of unintentional dopants. The results show that unintentional dopants are mostly incorporated on facets inclined to the [0001] direction, and suggest that gaseous impurities present in the MOVPE reactor are one source of dopant species. Copyright © 2010 Elsevier B.V. All rights reserved.

  3. Metal contacts in nanocrystalline n-type GaN: Schottky diodes.

    Science.gov (United States)

    Das, S N; Sarangi, S; Sahu, S N; Pal, A K

    2009-04-01

    Contact properties in nanocrystalline n-GaN in thin film form were studied by depositing nanocrystalline films onto aluminium coated fused silica substrates by high pressure sputtering of Si (1 at%) doped GaN target. Schottky diodes were realized with Au, Ni and Pd as top contacts on the nanocrystalline n-GaN films to examine the contact properties of the diodes thus formed. Variation of current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the Schottky diodes were recorded at different temperatures and analyzed in the light of the existing theories.

  4. n-type In2S3 films deposited by pulsed laser deposition: effect of laser power on the properties of the films

    Science.gov (United States)

    Wu, Chunyan; Mao, Dun; Liu, Zhu; Liang, Qi; Chen, Shirong; Yu, Yongqiang; Wang, Li; Luo, Linbao; Xu, Jun

    2015-05-01

    Pulsed laser deposition (PLD) with different levels of laser power was first used to deposit In2S3 films from homemade, high-purity In2S3 targets. This process was followed by post-annealing in an N2 atmosphere to improve the films’ crystallinity and conductivity. The annealed films were verified to be stoichiometric, body-centered, tetragonal In2S3 with the preferred orientation (103). The bandgap of the films decreased from 2.8 to 2.2 eV with an increase in the laser power, which was believed to be the result of the grain growth caused by the higher laser power. The electrical transport property of the bottom-gate field-effect transistor revealed the n-type conduction of the annealed In2S3 films, and the heterojunction p+-Si/annealed In2S3 film showed remarkable photovoltaic behavior upon light illumination, indicating that PLD-deposited In2S3 films may have great potential as a buffer layer in thin-film solar cells. What’s more, doped In2S3 films can be easily realized due to the fairly stoichiometric transfer of the PLD method.

  5. Thermoelectric properties of n-type 95%Bi2Te3–5%Bi2Se3 compounds fabricated by gas-atomization and spark plasma sintering

    International Nuclear Information System (INIS)

    Kim, Hyo-Seob; Hong, Soon-Jik

    2014-01-01

    Highlights: • Gas Atomization process was used to fabricate 95%Bi 2 Te 3 –5%Bi 2 Se 3 powders. • Characterization of gas atomized powders were conducted. • SPS process was used to sinter the atomized powders at different sintering temp. • Thermoelectric properties, density and hardness of SPS-ed bulks were analyzed. -- Abstract: In this study, n-type 95%Bi 2 Te 3 –5%Bi 2 Se 3 doped with 0.04% SbI 3 thermoelectric materials was fabricated by gas-atomization and spark plasma sintering (SPS) at a temperature range of 623–723 K. The microstructure of the gas atomized powder shows spherical shape, fine particle size and homogeneously distributed grains. The density of the sintered bulk reached nearly 100% of the theoretical density, where micro Vickers Hardness was found around 54–57 Hv. The Seebeck coefficient (α) of the sintered bulk decreased while electrical resistivity and thermal conductivity (κ) increased with increasing sintering temperature to 723 K, resulting in a decrease in figure of merit. The maximum figure of merit (ZT) was 0.76, which was obtained in the sintered bulk at 623 K

  6. Electrical transport characterization of Al and Sn doped Mg 2 Si thin films

    KAUST Repository

    Zhang, Bo

    2017-05-22

    Thin-film Mg2Si was deposited using radio frequency (RF) magnetron sputtering. Al and Sn were incorporated as n-type dopants using co-sputtering to tune the thin-film electrical properties. X-ray diffraction (XRD) analysis confirmed that the deposited films are polycrystalline Mg2Si. The Sn and Al doping concentrations were measured using Rutherford backscattering spectroscopy (RBS) and energy dispersive X-ray spectroscopy (EDS). The charge carrier concentration and the charge carrier type of the Mg2Si films were measured using a Hall bar structure. Hall measurements show that as the doping concentration increases, the carrier concentration of the Al-doped films increases, whereas the carrier concentration of the Sn-doped films decreases. Combined with the resistivity measurements, the mobility of the Al-doped Mg2Si films is found to decrease with increasing doping concentration, whereas the mobility of the Sn-doped Mg2Si films is found to increase.

  7. Optical and Electrical Properties of Sn-Doped Zinc Oxide Single Crystals

    Science.gov (United States)

    Haseman, M. S.; Saadatkia, Pooneh; Warfield, J. T.; Lawrence, J.; Hernandez, A.; Jellison, G. E.; Boatner, L. A.; Selim, F. A.

    2018-02-01

    Sn dopant in ZnO may significantly improve the n-type conductivity of ZnO through a characteristic double effect. However, studies on bulk Sn-doped ZnO are rare, and the effect of Sn doping on the optoelectronic properties of bulk ZnO is not well understood. In this work, the effect of Sn doping on the optical and electrical properties of ZnO bulk single crystals was investigated through optical absorption spectroscopy, Hall-effect measurements, and thermoluminescence (TL) spectroscopy. Undoped and Sn-doped ZnO single crystals were grown by chemical vapor transport method and characterized by x-ray diffraction analysis. The Sn doping level in the crystals was evaluated by inductively coupled plasma mass spectroscopy measurements. Hall-effect measurements revealed an increase in conductivity and carrier concentration with increasing Sn doping, while TL measurements identified a few donor species in the crystals with donor ionization energy ranging from 35 meV to 118 meV. Increasing Sn doping was also associated with a color change of single crystals from colorless to dark blue.

  8. Phosphorus-doped bismuth telluride films by electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Jian, E-mail: jzhou@xmu.edu.cn [Department of Materials Science and Engineering, College of Materials, Xiamen 361005 (China); Lin, Qinghan; Li, Hengyi [Department of Materials Science and Engineering, College of Materials, Xiamen 361005 (China); Cheng, Xuan [Department of Materials Science and Engineering, College of Materials, Xiamen 361005 (China); Fujian Key Laboratory of Advanced Materials, Xiamen University, Xiamen 361005 (China)

    2013-08-15

    Phosphorus-doped Bi{sub 2}Te{sub 3} films were synthesized on a stainless-steel electrode by electrochemical deposition. X-ray diffraction, scanning electron microscopy and transmission electron microscopy confirmed that the films are single-phased Bi{sub 2}Te{sub 3} solid solutions with a rhombohedral structure. The as-prepared films exhibit n-type characteristics with the Hall coefficient −1.76E−2 m{sup 3} C{sup −1} and the electrical conductivity 280 S cm{sup −1}. The thermal conductivity is 0.47 W m{sup −1} K{sup −1}, which is as low as one-third of the value observed in the bulk material. The doped P atoms occupy the interstitial positions between the two adjacent Te(1) layers connected by Van der Waals interaction in Bi{sub 2}Te{sub 3}. - Graphical abstract: Display Omitted - Highlights: • Phosphorus-doped Bi{sub 2}Te{sub 3} films were synthesized on a stainless-steel electrode by electrochemical deposition. • The thermal conductivity of the film is 0.47 W m{sup −1} K{sup −1}, which is one-third of the value observed in the bulk material. • The doped P atoms occupy the interstitial positions in Bi{sub 2}Te{sub 3}.

  9. Nitrogen-Doped Graphene for Photocatalytic Hydrogen Generation.

    Science.gov (United States)

    Chang, Dong Wook; Baek, Jong-Beom

    2016-04-20

    Photocatalytic hydrogen (H2 ) generation in a water splitting process has recently attracted tremendous interest because it allows the direct conversion of clean and unlimited solar energy into the ideal energy resource of H2 . For efficient photocatalytic H2 generation, the role of the photocatalyst is critical. With increasing demand for more efficient, sustainable, and cost-effective photocatalysts, various types of semiconductor photocatalysts have been intensively developed. In particular, on the basis of its superior catalytic and tunable electronic properties, nitrogen-doped graphene is a potential candidate for a high-performance photocatalyst. Nitrogen-doped graphene also offers additional advantages originating from its unique two-dimensional sp(2) -hybridized carbon network including a large specific surface area and exceptional charge transport properties. It has been reported that nitrogen-doped graphene can play diverse but positive functions including photo-induced charge acceptor/meditator, light absorber from UV to visible light, n-type semiconductor, and giant molecular photocatalyst. Herein, we summarize the recent progress and general aspects of nitrogen-doped graphene as a photocatalyst for photocatalytic H2 generation. In addition, challenges and future perspectives in this field are also discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Ambipolar Organic Phototransistors with p-Type/n-Type Conjugated Polymer Bulk Heterojunction Light-Sensing Layers

    KAUST Repository

    Nam, Sungho

    2016-11-18

    Ambipolar organic phototransistors with sensing channel layers, featuring p-type and n-type conjugated polymer bulk heterojunctions, exhibit outstanding light-sensing characteristics in both p-channel and n-channel sensing operation modes.

  11. Surface study of gallium- and aluminum- doped graphenes upon adsorption of cytosine: DFT calculations

    Energy Technology Data Exchange (ETDEWEB)

    Shokuhi Rad, Ali, E-mail: a.shokuhi@gmail.com [Department of Chemical Engineering, Qaemshahr Branch, Islamic Azad University, Qaemshahr (Iran, Islamic Republic of); Zareyee, Daryoush [Department of Chemistry, Qaemshahr Branch, Islamic Azad University, Qaemshahr (Iran, Islamic Republic of); Peyravi, Majid; Jahanshahi, Mohsen [Faculty of Chemical Engineering, Babol University of Technology, Babol (Iran, Islamic Republic of)

    2016-12-30

    Highlights: • P1 and P4 are the most stable adsorption configurations for cytosine. • NBO analysis show n-type semiconductor property for both Al- and Ga-doped graphenes. • Important changes in the HOMO and LUMO of doped graphene upon adsorption of cytosine. • Increase in the conductivity of system when cytosine is adsorbed on doped graphenes. - Abstract: The adsorption of cytosine molecule on Al- and Ga- doped graphenes is studied using first-principles density functional theory (DFT) calculations. The energetically most stable geometries of cytosine on both Al- and Ga- doped graphenes are determined and the adsorption energies are calculated. The net charge of transfer as well as local charge of doped atoms upon adsorption of cytosine are studied by natural bond orbitals (NBO) analysis. Orbital hybridizing of complexes was searched by frontier molecular orbital theory (FMO), and density of states (DOS). Depending on the side of cytosine, there are four possible sites for its adsorption on doped graphene; denoted as P1, P2, P3, and P4, respectively. The order of binding energy in the case of Al-doped graphene is found as P1 > P4 > P3 > P2. Interestingly, the order in the case of Ga-doped graphene changes to: P4 ∼ P1 > P3 > P2. Both surfaces show superior adsorbent property, resulting chemisorption of cytosine, especially at P1 and P4 position configurations. The NBO charge analysis reveals that the charge transfers from Al- and Ga- doped graphene sheets to cytosine. The electronic properties of both surfaces undertake important changes after cytosine adsorption, which indicates notable change in its electrical conductivity.

  12. Surface study of gallium- and aluminum- doped graphenes upon adsorption of cytosine: DFT calculations

    International Nuclear Information System (INIS)

    Shokuhi Rad, Ali; Zareyee, Daryoush; Peyravi, Majid; Jahanshahi, Mohsen

    2016-01-01

    Highlights: • P1 and P4 are the most stable adsorption configurations for cytosine. • NBO analysis show n-type semiconductor property for both Al- and Ga-doped graphenes. • Important changes in the HOMO and LUMO of doped graphene upon adsorption of cytosine. • Increase in the conductivity of system when cytosine is adsorbed on doped graphenes. - Abstract: The adsorption of cytosine molecule on Al- and Ga- doped graphenes is studied using first-principles density functional theory (DFT) calculations. The energetically most stable geometries of cytosine on both Al- and Ga- doped graphenes are determined and the adsorption energies are calculated. The net charge of transfer as well as local charge of doped atoms upon adsorption of cytosine are studied by natural bond orbitals (NBO) analysis. Orbital hybridizing of complexes was searched by frontier molecular orbital theory (FMO), and density of states (DOS). Depending on the side of cytosine, there are four possible sites for its adsorption on doped graphene; denoted as P1, P2, P3, and P4, respectively. The order of binding energy in the case of Al-doped graphene is found as P1 > P4 > P3 > P2. Interestingly, the order in the case of Ga-doped graphene changes to: P4 ∼ P1 > P3 > P2. Both surfaces show superior adsorbent property, resulting chemisorption of cytosine, especially at P1 and P4 position configurations. The NBO charge analysis reveals that the charge transfers from Al- and Ga- doped graphene sheets to cytosine. The electronic properties of both surfaces undertake important changes after cytosine adsorption, which indicates notable change in its electrical conductivity.

  13. N-type compensated silicon: resistivity, crystal growth, carrier lifetime, and relevant application for HIT solar cells

    Science.gov (United States)

    Li, Shuai; Gao, Wenxiu; Li, Zhen; Cheng, Haoran; Lin, Jinxia; Cheng, Qijin

    2017-05-01

    N-type compensated silicon shows unusual distribution of resistivity as crystal grows compared to the n-type uncompensated silicon. In this paper, evolutions of resistivities with varied concentrations of boron and varied starting resistivities of the n-type silicon are intensively calculated. Moreover, reduction of carrier mobility is taken into account by Schindler’s modified model of carrier mobility for the calculation of resistivity of the compensated silicon. As for substrates of solar cells, optimized starting resistivity and corresponding concentration of boron are suggested for better uniformity of resistivity and higher yield (fraction with ρ >0.5 ~ Ω \\centerdot \\text{cm} ) of the n-type compensated Cz crystal rod. A two-step growth method is investigated to obtain better uniformity of resistivity of crystal rod, and this method is very practical especially for the n-type compensated silicon. Regarding the carrier lifetime, the recombination by shallow energy-level dopants is taken into account for the compensated silicon, and evolution of carrier lifetime is simulated by considering all main recombination centers which agrees well with our measured carrier lifetimes as crystal grows. The n-type compensated silicon shows a larger reduction of carrier lifetime compared to the uncompensated silicon at the beginning of crystal growth, and recombination with a oxygen-related deep defect is sufficient to describe the reduction of degraded lifetime. Finally, standard heterojunction with intrinsic thin-layer (HIT) solar cells are made with substrates from the n-type compensated silicon rod, and a high efficiency of 22.1% is obtained with a high concentration (0.8× {{10}16}~\\text{c}{{\\text{m}}-3} ) of boron in the n-type compensated silicon feedstock. However, experimental efficiencies of HIT solar cells based on the n-type compensated silicon show an average reduction of 4% along with the crystal length compared to the uncompensated silicon. The

  14. Thin-film amorphous silicon germanium solar cells with p-and n-type hydrogenated silicon oxide layers

    NARCIS (Netherlands)

    Si, F.T.; Isabella, O.; Zeman, M.

    2017-01-01

    Mixed-phase hydrogenated silicon oxide (SiOx:H) is applied to thin-film hydrogenated amorphous silicon germanium (a-SiGe:H) solar cells serving as both p-doped and n-doped layers. The bandgap of p-SiOx:H is adjusted to achieve a highly-transparent window layer while also providing a strong electric

  15. Mobility variation calculation in n type PbTe between 50 and 300 K

    International Nuclear Information System (INIS)

    Lasbley, A.; Granger, R.; Pelletier, C.M.; Rolland, S.

    1985-01-01

    The mobility calculation, with an iterative method, in n type lead telluride is developed. Results are presented in the temperature range 50-300 K where the mobility is mainly limited by diffusion by acoustical and optical phonons. The detailed form of the wave functions in the six-band model has been taken into account and also the variations, with temperature, of all the physical parameters necessary for the electronic distribution calculation under low electric field. Only the acoustic deformation potential and the temperature coefficient of the conduction band edge effective mass which are not well known have been taken as adjustable parameters. The agreement between calculated and experimental mobility values is very good. The calculations fit the detailed variations of mobility which are experimentally found in the temperature range 50-300 K and for electronic concentrations varying from 10 17 cm -3 to 10 19 cm -3 [fr

  16. Beryllium implant activation and damage recovery study in n-type GaSb

    Science.gov (United States)

    Rahimi, N.; Behzadirad, M.; Renteria, Emma J.; Shima, D. M.; Muniz, Ayse J.; Busani, T.; Lavrova, Olga; Balakrishnan, G.; Lester, L. F.

    2014-03-01

    Damage induced by the implantation of beryllium in n-type GaSb and its removal by Rapid Thermal Annealing (RTA) are studied in detail by Atomic Force Microscopy (AFM), Cross Sectional Transmission Electron Microscopy (XTEM) and Energy Dispersive X-ray Spectroscopy (EDS). RTA has been implemented with different times and temperatures in order to optimize ion activation and to avoid Sb outdiffusion during the process. Results indicate a lattice quality that is close to pristine GaSb for samples annealed at 600 °C for 10s using a thick Si3N4 capping layer. Electrical response of the implanted diodes is measured and characterized as function of different annealing conditions.

  17. Solar Cells Based on Inks of n-Type Colloidal Quantum Dots

    KAUST Repository

    Ning, Zhijun

    2014-10-28

    © 2014 American Chemical Society. New inorganic ligands including halide anions have significantly accelerated progress in colloidal quantum dot (CQD) photovoltaics in recent years. All such device reports to date have relied on halide treatment during solid-state ligand exchanges or on co-treatment of long-aliphatic-ligand-capped nanoparticles in the solution phase. Here we report solar cells based on a colloidal quantum dot ink that is capped using halide-based ligands alone. By judicious choice of solvents and ligands, we developed a CQD ink from which a homogeneous and thick colloidal quantum dot solid is applied in a single step. The resultant films display an n-type character, making it suitable as a key component in a solar-converting device. We demonstrate two types of quantum junction devices that exploit these iodide-ligand-based inks. We achieve solar power conversion efficiencies of 6% using this class of colloids.

  18. Monte Carlo based geometrical model for efficiency calculation of an n-type HPGe detector

    Energy Technology Data Exchange (ETDEWEB)

    Padilla Cabal, Fatima, E-mail: fpadilla@instec.c [Instituto Superior de Tecnologias y Ciencias Aplicadas, ' Quinta de los Molinos' Ave. Salvador Allende, esq. Luaces, Plaza de la Revolucion, Ciudad de la Habana, CP 10400 (Cuba); Lopez-Pino, Neivy; Luis Bernal-Castillo, Jose; Martinez-Palenzuela, Yisel; Aguilar-Mena, Jimmy; D' Alessandro, Katia; Arbelo, Yuniesky; Corrales, Yasser; Diaz, Oscar [Instituto Superior de Tecnologias y Ciencias Aplicadas, ' Quinta de los Molinos' Ave. Salvador Allende, esq. Luaces, Plaza de la Revolucion, Ciudad de la Habana, CP 10400 (Cuba)

    2010-12-15

    A procedure to optimize the geometrical model of an n-type detector is described. Sixteen lines from seven point sources ({sup 241}Am, {sup 133}Ba, {sup 22}Na, {sup 60}Co, {sup 57}Co, {sup 137}Cs and {sup 152}Eu) placed at three different source-to-detector distances (10, 20 and 30 cm) were used to calibrate a low-background gamma spectrometer between 26 and 1408 keV. Direct Monte Carlo techniques using the MCNPX 2.6 and GEANT 4 9.2 codes, and a semi-empirical procedure were performed to obtain theoretical efficiency curves. Since discrepancies were found between experimental and calculated data using the manufacturer parameters of the detector, a detail study of the crystal dimensions and the geometrical configuration is carried out. The relative deviation with experimental data decreases from a mean value of 18-4%, after the parameters were optimized.

  19. Two stream instability in n-type gallium arsenide semiconductor quantum plasma

    Science.gov (United States)

    Ghosh, S.; Muley, Apurva

    2018-01-01

    By using quantum hydrodynamic model, we derive a generalized dielectric response function for two stream instability (convective only) in n-type gallium arsenide semiconductor plasma. We investigate the phase and amplification profiles of two stream instability with externally applied electric field ranging from 2600 to 4000 kV m-1 in presence of non-dimensional quantum parameter- H. In this range, a significant number of electrons in satellite valley become comparable to the number of electrons in central valley. The presence of quantum corrections in plasma medium induces two novel modes; one of it has amplifying nature and propagates in forward direction. It also modifies the spectral profile of four pre-existing modes in classical plasma. The existence of two stream instability is also established analytically by deriving the real part of longitudinal electrokinetic power flow density.

  20. Neutron transmutation doping of silicon for the production of radiation detectors

    International Nuclear Information System (INIS)

    Alexiev, D.

    1987-11-01

    P-type silicon was doped by neutron transmutation (NTD-Si) to produce high resistivity n-type silicon suitable for the production of surface barrier radiation detectors. Deep level transient spectroscopy (DLTS) analysis showed no remnant traps following annealing (850 deg C) of the NTD-Si in the presence of a phosphosilicate glass getter. Surface barrier radiation detectors constructed from this material showed no significant charge trapping and compare favourably with those constructed of float-zone (FZ) Si

  1. Dual-bath electrodeposition of n-type Bi–Te/Bi–Se multilayer thin films

    Energy Technology Data Exchange (ETDEWEB)

    Matsuoka, Ken; Okuhata, Mitsuaki; Takashiri, Masayuki, E-mail: takashiri@tokai-u.jp

    2015-11-15

    N-type Bi–Te/Bi–Se multilayer thin films were prepared by dual-bath electrodeposition. We varied the number of layers from 2 to 10 while the total film thickness was maintained at approximately 1 μm. All the multilayer films displayed the X-ray diffraction peaks normally observed from individual Bi{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3} crystal structures, indicating that both phases coexist in the multilayer. The cross-section of the 10-layer Bi–Te/Bi–Se film was composed of stacked layers with nano-sized grains but the boundaries between the layers were not planar. The Seebeck coefficient was almost constant throughout the entire range of our experiment, but the electrical conductivity of the multilayer thin films increased significantly as the number of layers was increased. This may be because the electron mobility increases as the thickness of each layer is decreased. As a result of the increased electrical conductivity, the power factor also increased with the number of layers. The maximum power factor was 1.44 μW/(cm K{sup 2}) for the 10-layer Bi–Te/Bi–Se film, this was approximately 3 times higher than that of the 2-layer sample. - Highlights: • N-type Bi–Te/Bi–Se multilayer thin films were deposited by electrodeposition. • We employed a dual-bath electrodeposition process for preparing the multilayers. • The Bi–Te/Bi–Se film was composed of stacked layers with nano-sized grains. • The electrical conductivity increased as the number of layers was increased. • The power factor improved by 3 times as the number of layers was increased.

  2. Electron paramagnetic resonance study on n-type electron-irradiated 3C-SiC

    Energy Technology Data Exchange (ETDEWEB)

    Carlsson, P; Rabia, K; Son, N T; Janzen, E [Department of Physics, Chemistry and Biology, Linkoeping University, SE-581 83 Linkoeping (Sweden); Ohshima, T; Morishita, N; Itoh, H [Japan Atomic Energy Research Institute, Takasaki 370-1292 (Japan); Isoya, J [University of Tsukuba, Tsukuba 305-8550 (Japan)], E-mail: paca@ifm.liu.se

    2008-03-15

    Electron Paramagnetic Resonance (EPR) was used to study defects in n-type 3C-SiC films irradiated by 3-MeV electrons at room temperature with a dose of 2x10{sup 18} cm{sup -2}. After electron irradiation, two new EPR spectra with an effective spin S = 1, labeled L5 and L6, were observed. The L5 center has C{sub 3v} symmetry with g = 2.004 and a fine-structure parameter D = 436.5x10{sup -4} cm{sup -1}. The L5 spectrum was only detected under light illumination and it could not be detected after annealing at {approx}550{sup 0}C. The principal z-axis of the D tensor is parallel to the <111>-directions, indicating the location of spins along the Si-C bonds. Judging from the symmetry and the fact that the signal was detected under illumination in n-type material, the L5 center may be related to the divacancy in the neutral charge state. The L6 center has a C{sub 2v}-symmetry with an isotropic g-value of g = 2.003 and the fine structure parameters D = 547.7x10{sup -4} cm{sup -1} and E = 56.2x10{sup -4} cm{sup -1}. The L6 center disappeared after annealing at a rather low temperature ({approx}200 deg. C), which is substantially lower than the known annealing temperatures for vacancy-related defects in 3C-SiC. This highly mobile defect may be related to carbon interstitials.

  3. Scanning tunneling spectroscopy to probe site-selection in heterovalent doping: Zn(II)-doped Cu(I)In(III)S2 as a case study

    Science.gov (United States)

    Kundu, Biswajit; Pal, Amlan J.

    2017-08-01

    We report scanning tunneling spectroscopy (STS) of a heterovalent-doped ternary compound semiconductors and their binary counterparts. The effect of dopants in the semiconductors that yielded a shift in Fermi energy has been found to be manifested in the density of states (DOS) spectrum. The shift infers the nature of doping, which the heterovalent dopants induce, and hence the site of the ternary system that the dopants occupy. For example, in the present case with Zn(II)-doped Cu(I)In(III)S2, the DOS spectra showed a shift in Fermi energy towards the conduction band and hence a n-type doping due to the introduction of electrons. Such a shift inferred that the bivalent dopants occupied the cuprous site. The results have been substantiated by STS studies of doped binary components, namely, Cu2S and In2S3 and shift in Fermi energy thereof. With the tuning in the Fermi energy, the homojunctions between undoped and doped semiconductors have a type-II band-alignment at the interface resulting in current rectification through the junctions. The band-diagram of the homojunctions formed through STS substantiated the direction of current-rectification in the junctions.

  4. Application of highly silicon-doped marker layers in the investigation of unintentional doping in GaN on sapphire

    International Nuclear Information System (INIS)

    Oliver, R.A.

    2010-01-01

    To provide a route to the assessment of the impact of inclined facets on unintentional n-type doping during the growth of c-plane GaN on sapphire, thin (100 nm), highly Si-doped (at 10 19 cm -3 ) marker layers have been incorporated into a GaN epitaxial layer grown by a method involving a transition from initial three-dimensional island growth to later, two-dimensional, planar growth. Imaging of the completed epitaxial layer in cross-section by scanning capacitance microscopy reveals the shapes of the islands, which were present during the early stages of growth and the relationship between the facets present and the incorporation of unintentional dopants. The results show that unintentional dopants are mostly incorporated on facets inclined to the [0 0 0 1] direction, and suggest that gaseous impurities present in the MOVPE reactor are one source of dopant species. -- Research highlights: →Scanning capacitance microscopy has been used to study unintentional doping in GaN epilayers. →Highly doped marker layers provide the means to track the growth and coalescence of the islands, which form the epilayer, and how this relates to the incorporation of unintentional dopants. →The results suggest that the presence of facets inclined to (0 0 0 1) is important in the incorporation of unintentional dopants.

  5. Doping effects on the electronic properties of armchair phosphorene nanoribbons: A first-principles study

    Science.gov (United States)

    Zhou, Wenzhe; Zou, Hui; Xiong, Xiang; Zhou, Yu; Liu, Rutie; Ouyang, Fangping

    2017-10-01

    On the basis of first-principles density functional theory, the different electronic structures of marginal or central doped armchair phosphorene nanoribbons with various species were calculated. It was found that the bonds between the foreign atoms and the adjacent P atoms are energetically more stable for central doping. The electronic properties of the doped ribbons are strongly related to the valence electron number of foreign atoms. B-, N-, F-, Al-doped (type Ⅰ) armchair phosphorene nanoribbons remain nonmagnetic semiconductors. The bandgap of the central doped nanoribbons is larger than that of the marginal doped nanoribbons. C, O, Si, S doping (type Ⅱ) at the edge introduce about 1 μB delocalized magnetic moment, while significantly decreasing for central doping, which is associated with electron transferring from foreign atoms to neighboring P atoms. The magnetism introduced by type Ⅱ dopants is provided by multiple orbits between the foreign atoms and the adjacent P atoms and delocalized on the edge for marginal doping. These results prove that the presence and the location of isolated electrons are both important factors for modulation of magnetic properties of armchair phosphorene nanoribbons through substitutional doping.

  6. Comparison of resolution characteristics between exponential-doping and uniform-doping GaN photocathodes

    Science.gov (United States)

    Wang, Hong-gang; Qian, Yun-sheng; Lu, Liu-bing; Cheng, Hong-chang; Chang, Ben-kang

    2013-08-01

    The studies of quantum efficiency, electronic energy distribution and stability are highly concerned in the application of Negative electron affinity (NEA) gallium nitride (GaN) photocathodes while the resolution of photocathodes are concerned rarely. The resolutions of some image intensifiers are smaller than computational value partly because of ignoring the resolution of photocathodes. To a certain extent, the resolutions of image intensifiers are influenced by photocathodes. Electronic transverse diffusion is the main cause of decreasing the resolution of photocathodes whereas the exponential-doping structure can reduce its influence. In this paper, the resolution characteristics of photocathodes have been studied by using the modulation transfer function (MTF) method. The MTF expressions of transmission-mode exponential-doping photocathodes have been obtained by solving the two-dimensional continuity equations. According to the MTF expressions, the resolution characteristics between exponential-doping and uniform-doping GaN photocathodes are calculated theoretically and analyzed comparatively. At the same time, the relationships between resolution and thickness of the emission layer Te, electron diffusion length LD are researched in detail. The calculated results show that, compared with the uniform-doping photocathode, the exponential-doping structure can increase the resolution of photocathode evidently. The resolution of exponential-doping GaN photocathode is improved distinctly when the spatial frequency varies from 400 to 800 lp/mm. The MTF characteristics approach gradually when f increases or decreases. Let f =600 lp/mm, the resolution increases by 20%-48% approximately. The constant built-in electric field for exponential-doping GaN photocathode can increase the resolution of photocathode. The improvement of resolution is different from decreasing Te, LD or increasing the recombination velocity of back-interface which are at the cost of reducing the

  7. Nitrogen doping in atomic layer deposition grown titanium dioxide films by using ammonium hydroxide

    Energy Technology Data Exchange (ETDEWEB)

    Kaeaeriaeinen, M.-L., E-mail: marja-leena.kaariainen@lut.fi; Cameron, D.C.

    2012-12-30

    Titanium dioxide films have been created by atomic layer deposition using titanium chloride as the metal source and a solution of ammonium hydroxide in water as oxidant. Ammonium hydroxide has been used as a source of nitrogen for doping and three thickness series have been deposited at 350 Degree-Sign C. A 15 nm anatase dominated film was found to possess the highest photocatalytic activity in all film series. Furthermore almost three times better photocatalytic activity was discovered in the doped series compared to undoped films. The doped films also had lower resistivity. The results from X-ray photoemission spectroscopy showed evidence for interstitial nitrogen in the titanium dioxide structure. Besides, there was a minor red shift observable in the thickest samples. In addition the film conductivity was discovered to increase with the feeding pressure of ammonium hydroxide in the oxidant precursor. This may indicate that nitrogen doping has caused the decrease in the resistivity and therefore has an impact as an enhanced photocatalytic activity. The hot probe test showed that all the anatase or anatase dominant films were p-type and all the rutile dominant films were n-type. The best photocatalytic activity was shown by anatase-dominant films containing a small amount of rutile. It may be that p-n-junctions are formed between p-type anatase and n-type rutile which cause carrier separation and slow down the recombination rate. The combination of nitrogen doping and p-n junction formation results in superior photocatalytic performance. - Highlights: Black-Right-Pointing-Pointer We found all N-doped and undoped anatase dominating films p-type. Black-Right-Pointing-Pointer We found all N-doped and undoped rutile dominating films n-type. Black-Right-Pointing-Pointer We propose that p-n junctions are formed in anatase-rutile mixture films. Black-Right-Pointing-Pointer We found that low level N-doping has increased TiO{sub 2} conductivity. Black

  8. Emitter formation using laser doping technique on n- and p-type c-Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    López, G., E-mail: gema.lopez@upc.edu; Ortega, P.; Colina, M.; Voz, C.; Martín, I.; Morales-Vilches, A.; Orpella, A.; Alcubilla, R.

    2015-05-01

    Highlights: • We use laser doping technique to create highly-doped regions. • Dielectric layers are used as both passivating layer and dopant source. • The high quality of the junctions makes laser doping technique using dielectric layers as dopant source suitable for solar cells applications. - Abstract: In this work laser doping technique is used to create highly-doped regions defined in a point-like structure to form n+/p and p+/n junctions applying a pulsed Nd-YAG 1064 nm laser in the nanosecond regime. In particular, phosphorous-doped silicon carbide stacks (a-SiC{sub x}/a-Si:H (n-type)) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) and aluminum oxide (Al{sub 2}O{sub 3}) layers deposited by atomic layer deposition (ALD) on 2 ± 0.5 Ω cm p- and n-type FZ c-Si substrates respectively are used as dopant sources. Laser power and number of pulses per spot are explored to obtain the optimal electrical behavior of the formed junctions. To assess the quality of the p+ and n+ regions, the junctions are electrically contacted and characterized by means of dark J–V measurements. Additionally, a diluted HF treatment previous to front metallization has been explored in order to know its impact on the junction quality. The results show that fine tuning of the energy pulse is critical while the number of pulses has minor effect. In general the different HF treatments have no impact in the diode electrical behavior except for an increase of the leakage current in n+/p junctions. The high electrical quality of the junctions makes laser doping, using dielectric layers as dopant source, suitable for solar cell applications. Particularly, a potential open circuit voltage of 0.64 V (1 sun) is expected for a finished solar cell.

  9. Sanctions for doping in sport

    Directory of Open Access Journals (Sweden)

    Mandarić Sanja

    2014-01-01

    Full Text Available Top-level sport imposes new and more demanding physical and psychological pressures, and the desire for competing, winning and selfassertion leads athletes into temptation to use prohibited substances in order to achieve the best possible results. Regardless of the fact that the adverse consequences of prohibited substances are well-known, prestige and the need to dominate sports arenas have led to their use in sports. Doping is one of the biggest issues in sport today, and the fight against it is a strategic objective on both global and national levels. World Anti-Doping Agency, the International Olympic Committee, international sports federations, national anti-doping agencies, national sports federations, as well as governments and their repressive apparatuses are all involved in the fight against doping in sport. This paper points to a different etymology and phenomenology of doping, the beginnings of doping in sport, sports doping scandals as well as the most important international instruments regulating this issue. Also, there is a special reference in this paper to the criminal and misdemeanor sanctions for doping in sport. In Serbia doping in sport is prohibited by the Law on Prevention of Doping in Sports which came into force in 2005 and which prescribes the measures and activities aimed at prevention of doping in sport. In this context, the law provides for the following three criminal offenses: use of doping substances, facilitating the use of doping substances, and unauthorized production and putting on traffic of doping substances. In addition, aiming at curbing the abuse of doping this law also provides for two violations. More frequent and repetitive doping scandals indicate that doping despite long-standing sanctions is still present in sports, which suggests that sanctions alone have not given satisfactory results so far.

  10. Tunable doping of graphene nanoribbon arrays by chemical functionalization

    Science.gov (United States)

    Solís-Fernández, Pablo; Bissett, Mark A.; Tsuji, Masaharu; Ago, Hiroki

    2015-02-01

    We demonstrate the controlled tuning of the electronic band structure of large-arrays of graphene nanoribbons (GNRs) by chemical functionalization. The GNR arrays are synthesized by substrate-controlled metal-assisted etching of graphene in H2 at high temperature, and functionalized with different molecules. From Raman spectroscopy and carrier transport measurements, we found that 4-nitrobenzenediazonium (4-NBD) and diethylene triamine (DETA) molecules can tune the doping level of the GNR arrays to p- and n-type, respectively. In both cases, the doping effects induced in the GNRs were found to be higher than for a pristine graphene sheet, due to the presence of a large quantity of edges. Effects of chemical doping on the Raman spectrum of sp2 carbon materials are also discussed. Our findings offer an effective way to control the electronic structure of GNRs by chemical functionalization, and are expected to facilitate the production of nanoribbon-based p-n junctions for future implementation into electronic circuits.We demonstrate the controlled tuning of the electronic band structure of large-arrays of graphene nanoribbons (GNRs) by chemical functionalization. The GNR arrays are synthesized by substrate-controlled metal-assisted etching of graphene in H2 at high temperature, and functionalized with different molecules. From Raman spectroscopy and carrier transport measurements, we found that 4-nitrobenzenediazonium (4-NBD) and diethylene triamine (DETA) molecules can tune the doping level of the GNR arrays to p- and n-type, respectively. In both cases, the doping effects induced in the GNRs were found to be higher than for a pristine graphene sheet, due to the presence of a large quantity of edges. Effects of chemical doping on the Raman spectrum of sp2 carbon materials are also discussed. Our findings offer an effective way to control the electronic structure of GNRs by chemical functionalization, and are expected to facilitate the production of nanoribbon

  11. Fitness Doping and Body Management

    DEFF Research Database (Denmark)

    Thualagant, Nicole

    This PhD thesis examines in a first paper the conceptualization of fitness doping and its current limitations. Based on a review of studies on bodywork and fitness doping it is emphasised that the definition of doping does not provide insights into bodywork of both men and women. Moreover...... for body control and thus a management of the body....

  12. Optical tuning of photonic bandgaps in dye-doped nematic liquid crystal photonic crystal fibers

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Bjarklev, Anders Overgaard; Hermann, David Sparre

    2005-01-01

    An all-optical modulator is demonstrated, which utilizes a pulsed 532 nm laser to modulate the spectral position of the bandgaps in a photonic crystal fiber infiltrated with a dye-doped nematic liquid crystal. In order to investigate the time response of the LCPBG fiber device, a low-power CW probe...

  13. Effect of Gallium Doping on the Characteristic Properties of Polycrystalline Cadmium Telluride Thin Film

    Science.gov (United States)

    Ojo, A. A.; Dharmadasa, I. M.

    2017-08-01

    Ga-doped CdTe polycrystalline thin films were successfully electrodeposited on glass/fluorine doped tin oxide substrates from aqueous electrolytes containing cadmium nitrate (Cd(NO3)2·4H2O) and tellurium oxide (TeO2). The effects of different Ga-doping concentrations on the CdTe:Ga coupled with different post-growth treatments were studied by analysing the structural, optical, morphological and electronic properties of the deposited layers using x-ray diffraction (XRD), ultraviolet-visible spectrophotometry, scanning electron microscopy, photoelectrochemical cell measurement and direct-current conductivity test respectively. XRD results show diminishing (111)C CdTe peak above 20 ppm Ga-doping and the appearance of (301)M GaTe diffraction above 50 ppm Ga-doping indicating the formation of two phases; CdTe and GaTe. Although, reductions in the absorption edge slopes were observed above 20 ppm Ga-doping for the as-deposited CdTe:Ga layer, no obvious influence on the energy gap of CdTe films with Ga-doping were detected. Morphologically, reductions in grain size were observed at 50 ppm Ga-doping and above with high pinhole density within the layer. For the as-deposited CdTe:Ga layers, conduction type change from n- to p- were observed at 50 ppm, while the n-type conductivity were retained after post-growth treatment. Highest conductivity was observed at 20 ppm Ga-doping of CdTe. These results are systematically reported in this paper.

  14. All-Solid-State Drivers for High Power Excimer Lasers Used in Projection Gas Immersion Laser Doping

    National Research Council Canada - National Science Library

    Jacob, Jonah

    2001-01-01

    The objective of this SBIR program is to develop all-solid-state pulsed modulators to drive the high power excimer lasers required to commercialize the Projection Gas Immersion Laser Doping (P-GILD) process...

  15. N-type high-performance multicrystalline and mono-like silicon wafers with lifetimes above 2 ms

    Science.gov (United States)

    Pheng Phang, Sieu; Cheong Sio, Hang; Yang, Chia-Fu; Lan, Chung-Wen; Yang, Yu-Min; Wen-Huai Yu, Andy; Sung-Lin Hsu, Bruce; Wen-Ching Hsu, Chuck; Macdonald, Daniel

    2017-08-01

    Combined with advanced crystal growth technology and reduced dislocation densities, the higher tolerance to metal contamination of n-type silicon makes n-type cast-grown silicon a potential option for low cost high quality substrates for solar cells. Using a combination of photoconductance based lifetime testing and photoluminescence imaging, we have investigated the carrier lifetime in wafers from the bottom, middle, and top parts of a n-type high-performance multicrystalline (HPM) silicon ingot, and wafers from n-type mono-like silicon ingots after each high temperature solar cell processes, including after boron diffusion, phosphorus diffusion, and hydrogenation. Although boron diffusion leads to a degradation of the sample lifetime, phosphorus diffusion and hydrogenation is effective at recovering the lifetime in the intra-grain region and at the grain boundaries respectively. Quasi-steady-state photoconductance (QSSPC) measurements show that the arithmetic average lifetime of HPM silicon wafers and mono-like silicon wafers can reach up to 1.8 and 3.3 ms respectively for a process sequence including a boron diffusion, with corresponding implied open circuit voltage of about 720 mV. If the boron diffusion can be avoided, average lifetimes up to 3.0 and 6.6 ms can be achieved respectively, highlighting the excellent potential of n-type cast-grown materials.

  16. Doping of silicon carbide by ion implantation; Dopage du carbure de silicium par implantation ionique

    Energy Technology Data Exchange (ETDEWEB)

    Gimbert, J

    1999-03-04

    It appeared that in some fields, as the hostile environments (high temperature or irradiation), the silicon compounds showed limitations resulting from the electrical and mechanical properties. Doping of 4H and 6H silicon carbide by ion implantation is studied from a physicochemical and electrical point of view. It is necessary to obtain n-type and p-type material to realize high power and/or high frequency devices, such as MESFETs and Schottky diodes. First, physical and electrical properties of silicon carbide are presented and the interest of developing a process technology on this material is emphasised. Then, physical characteristics of ion implantation and particularly classical dopant implantation, such as nitrogen, for n-type doping, and aluminium and boron, for p-type doping are described. Results with these dopants are presented and analysed. Optimal conditions are extracted from these experiences so as to obtain a good crystal quality and a surface state allowing device fabrication. Electrical conduction is then described in the 4H and 6H-SiC polytypes. Freezing of free carriers and scattering processes are described. Electrical measurements are carried out using Hall effect on Van der Panw test patterns, and 4 point probe method are used to draw the type of the material, free carrier concentrations, resistivity and mobility of the implanted doped layers. These results are commented and compared to the theoretical analysis. The influence of the technological process on electrical conduction is studied in view of fabricating implanted silicon carbide devices. (author)

  17. A Charge-Orbital Balance Picture of Doping in Colloidal Quantum Dot Solids

    KAUST Repository

    Voznyy, Oleksandr

    2012-09-25

    We present a framework-validated using both modeling and experiment-to predict doping in CQD films. In the ionic semiconductors widely deployed in CQD films, the framework reduces to a simple accounting of the contributions of the oxidation state of each constituent, including both inorganic species and organic ligands. We use density functional theory simulations to confirm that the type of doping can be reliably predicted based on the overall stoichiometry of the CQDs, largely independent of microscopic geometrical bonding configurations. Studies employing field-effect transistors constructed from CQDs that have undergone various chemical treatments, coupled with Rutherford backscattering and X-ray photoelectron spectroscopy to provide compositional analysis, allow us to test and confirm the proposed model in an experimental framework. We investigate both p- and n-type electronic doping spanning a wide range of carrier concentrations from 10 16 cm -3 to over 10 18 cm -3, and demonstrate reversible switching between p- and n-type doping by changing the CQD stoichiometry. We show that the summation of the contributions from all cations and anions within the film can be used to predict accurately the majority carrier type. The findings enable predictable control over majority carrier concentration via tuning of the overall stoichiometry. © 2012 American Chemical Society.

  18. Passivation of Molecular n-Doping: Exploring the Limits of Air Stability

    KAUST Repository

    Tietze, Max Lutz

    2016-03-03

    © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Molecular doping is a key technique for flexible and low-cost organic complementary semiconductor technologies that requires both efficient and stable p- and n-type doping. However, in contrast to molecular p-dopants, highly efficient n-type dopants are commonly sensitive to rapid degradation in air due to their low ionization energies (IEs) required for electron donation, e.g., IE = 2.4 eV for tetrakis(1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinato)ditungsten(II) (W2(hpp)4). Here, the air stability of various host:W2(hpp)4 combinations is compared by conductivity measurements and photoemission spectroscopy. A partial passivation of the n-doping against degradation is found, with this effect identified to depend on the specific energy levels of the host material. Since host-W2(hpp)4 electronic wavefunction hybridization is unlikely due to confinement of the dopant highest occupied molecular orbital (HOMO) to its molecular center, this finding is explained via stabilization of the dopant by single-electron transfer to a host material whose energy levels are sufficiently low for avoiding further charge transfer to oxygen-water complexes. Our results show the feasibility of temporarily handling n-doped organic thin films in air, e.g., during structuring of organic field effect transistors (OFETs) by lithography.

  19. Anion-induced N-doping of naphthalenediimide polymer semiconductor in organic thin-film transistors

    KAUST Repository

    Han, Yang

    2018-03-13

    Molecular doping is an important strategy to improve the charge transport properties of organic semiconductors in various electronic devices. Compared to p-type dopants, the development of n-type dopants is especially challenging due to poor dopant stability against atmospheric conditions. In this article, we report the n-doping of the milestone naphthalenediimide-based conjugated polymer P(NDI2OD-T2) in organic thin film transistor devices by soluble anion dopants. The addition of the dopants resulted in the formation of stable radical anions in thin films, as confirmed by EPR spectroscopy. By tuning the dopant concentration via simple solution mixing, the transistor parameters could be readily controlled. Hence the contact resistance between the electrodes and the semiconducting polymer could be significantly reduced, which resulted in the transistor behaviour approaching the desirable gate voltage-independent model. Reduced hysteresis was also observed, thanks to the trap filling by the dopant. Under optimal doping concentrations the channel on-current was increased several fold whilst the on/off ratio was simultaneously increased by around one order of magnitude. Hence doping with soluble organic salts appears to be a promising route to improve the charge transport properties of n-type organic semiconductors.

  20. Electrical characterization of deep levels in n-type GaAs after hydrogen plasma treatment

    International Nuclear Information System (INIS)

    Nyamhere, C.; Botha, J.R.; Venter, A.

    2011-01-01

    Deep level transient spectroscopy (DLTS) and Laplace-DLTS (L-DLTS) have been used to investigate defects in an n-type GaAs before and after exposure to a dc hydrogen plasma (hydrogenation). DLTS revealed the presence of three prominent electron traps in the material in the temperature range 20-300 K. However, L-DLTS with its higher resolution enabled the splitting of two narrowly spaced emission rates. Consequently four electron traps at, E C -0.33 eV, E C -0.36 eV, E C -0.38 eV and E C -0.56 eV were observed in the control sample. Following hydrogenation, all these traps were passivated with a new complex (presumably the M3), emerging at E C -0.58 eV. Isochronal annealing of the passivated material between 50 and 300 o C, revealed the emergence of a secondary defect, not previously observed, at E C -0.37 eV. Finally, the effect of hydrogen passivation is completely reversed upon annealing at 300 o C, as all the defects originally observed in the reference sample were recovered.

  1. Electrical characterization of deep levels in n-type GaAs after hydrogen plasma treatment

    Energy Technology Data Exchange (ETDEWEB)

    Nyamhere, C., E-mail: s210239522@live.nmmu.ac.z [Department of Physics, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); Botha, J.R.; Venter, A. [Department of Physics, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa)

    2011-05-15

    Deep level transient spectroscopy (DLTS) and Laplace-DLTS (L-DLTS) have been used to investigate defects in an n-type GaAs before and after exposure to a dc hydrogen plasma (hydrogenation). DLTS revealed the presence of three prominent electron traps in the material in the temperature range 20-300 K. However, L-DLTS with its higher resolution enabled the splitting of two narrowly spaced emission rates. Consequently four electron traps at, E{sub C}-0.33 eV, E{sub C}-0.36 eV, E{sub C}-0.38 eV and E{sub C}-0.56 eV were observed in the control sample. Following hydrogenation, all these traps were passivated with a new complex (presumably the M3), emerging at E{sub C}-0.58 eV. Isochronal annealing of the passivated material between 50 and 300 {sup o}C, revealed the emergence of a secondary defect, not previously observed, at E{sub C}-0.37 eV. Finally, the effect of hydrogen passivation is completely reversed upon annealing at 300 {sup o}C, as all the defects originally observed in the reference sample were recovered.

  2. Ti/Al Ohmic Contacts to n-Type GaN Nanowires

    Directory of Open Access Journals (Sweden)

    Gangfeng Ye

    2011-01-01

    Full Text Available Titanium/aluminum ohmic contacts to tapered n-type GaN nanowires with triangular cross-sections were studied. To extract the specific contact resistance, the commonly used transmission line model was adapted to the particular nanowire geometry. The most Al-rich composition of the contact provided a low specific contact resistance (mid 10−8 Ωcm2 upon annealing at 600 °C for 15 s, but it exhibited poor thermal stability due to oxidation of excess elemental Al remaining after annealing, as revealed by transmission electron microscopy. On the other hand, less Al-rich contacts required higher annealing temperatures (850 or 900 °C to reach a minimum specific contact resistance but exhibited better thermal stability. A spread in the specific contact resistance from contact to contact was tentatively attributed to the different facets that were contacted on the GaN nanowires with a triangular cross-section.

  3. Optimization of the n-type HPGe detector parameters to theoretical determination of efficiency curves

    International Nuclear Information System (INIS)

    Rodriguez-Rodriguez, A.; Correa-Alfonso, C.M.; Lopez-Pino, N.; Padilla-Cabal, F.; D'Alessandro, K.; Corrales, Y.; Garcia-Alvarez, J. A.; Perez-Mellor, A.; Baly-Gil, L.; Machado, A.

    2011-01-01

    A highly detailed characterization of a 130 cm 3 n-type HPGe detector, employed in low - background gamma spectrometry measurements, was done. Precise measured data and several Monte Carlo (MC) calculations have been combined to optimize the detector parameters. HPGe crystal location inside the Aluminum end-cap as well as its dimensions, including the borehole radius and height, were determined from frontal and lateral scans. Additionally, X-ray radiography and Computed Axial Tomography (CT) studies were carried out to complement the information about detector features. Using seven calibrated point sources ( 241 Am, 133 Ba, 57,60 Co, 137 Cs, 22 Na and 152 Eu), photo-peak efficiency curves at three different source - detector distances (SDD) were obtained. Taking into account the experimental values, an optimization procedure by means of MC simulations (MCNPX 2.6 code) were performed. MC efficiency curves were calculated specifying the optimized detector parameters in the MCNPX input files. Efficiency calculation results agree with empirical data, showing relative deviations lesser 10%. (Author)

  4. Carbon-hydrogen defects with a neighboring oxygen atom in n-type Si

    Science.gov (United States)

    Gwozdz, K.; Stübner, R.; Kolkovsky, Vl.; Weber, J.

    2017-07-01

    We report on the electrical activation of neutral carbon-oxygen complexes in Si by wet-chemical etching at room temperature. Two deep levels, E65 and E75, are observed by deep level transient spectroscopy in n-type Czochralski Si. The activation enthalpies of E65 and E75 are obtained as EC-0.11 eV (E65) and EC-0.13 eV (E75). The electric field dependence of their emission rates relates both levels to single acceptor states. From the analysis of the depth profiles, we conclude that the levels belong to two different defects, which contain only one hydrogen atom. A configuration is proposed, where the CH1BC defect, with hydrogen in the bond-centered position between neighboring C and Si atoms, is disturbed by interstitial oxygen in the second nearest neighbor position to substitutional carbon. The significant reduction of the CH1BC concentration in samples with high oxygen concentrations limits the use of this defect for the determination of low concentrations of substitutional carbon in Si samples.

  5. Enhanced performance of dispenser printed MA n-type Bi₂Te₃ composite thermoelectric generators.

    Science.gov (United States)

    Madan, Deepa; Wang, Zuoqian; Chen, Alic; Juang, Rei-Cheng; Keist, Jay; Wright, Paul K; Evans, Jim W

    2012-11-01

    This work presents performance advancements of dispenser printed composite thermoelectric materials and devices. Dispenser printed thick films allow for low-cost and scalable manufacturing of microscale energy harvesting devices. A maximum ZT value of 0.31 has been achieved for mechanically alloyed (MA) n-type Bi₂Te₃-epoxy composite films with 1 wt % Se cured at 350 °C. The enhancement of ZT is a result of increase in the electrical conductivity through the addition of Se, which ultimately lowers the sintering temperature (350 °C). A 62 single-leg thermoelectric generator (TEG) prototype with 5 mm ×700 μm × 120 μm printed element dimensions was fabricated on a custom designed polyimide substrate with thick metal contacts. The prototype device produced a power output of 25 μW at 0.23 mA current and 109 mV voltage for a temperature difference of 20 °C, which is sufficient for low power generation for autonomous microsystem applications.

  6. Advantages of N-Type Hydrogenated Microcrystalline Silicon Oxide Films for Micromorph Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    Amornrat Limmanee

    2013-01-01

    Full Text Available We report on the development and application of n-type hydrogenated microcrystalline silicon oxide films (n μc-SiO:H in hydrogenated amorphous silicon oxide/hydrogenated microcrystalline silicon (a-SiO:H/μc-Si:H micromorph solar cells. The n μc-SiO:H films with high optical bandgap and low refractive index could be obtained when a ratio of carbon dioxide (CO2 to silane (SiH4 flow rate was raised; however, a trade-off against electrical property was observed. We applied the n μc-SiO:H films in the top a-SiO:H cell and investigated the changes in cell performance with respect to the electrical and optical properties of the films. It was found that all photovoltaic parameters of the micromorph silicon solar cells using the n top μc-SiO:H layer enhanced with increasing the CO2/SiH4 ratio up to 0.23, where the highest initial cell efficiency of 10.7% was achieved. The enhancement of the open circuit voltage (Voc was likely to be due to a reduction of reverse bias at subcell connection—n top/p bottom interface—and a better tunnel recombination junction contributed to the improvement in the fill factor (FF. Furthermore, the quantum efficiency (QE results also have demonstrated intermediate-reflector function of the n μc-SiO:H films.

  7. P/Q- and N-type calcium-channel antibodies: Oncological, neurological, and serological accompaniments.

    Science.gov (United States)

    Zalewski, Nicholas L; Lennon, Vanda A; Lachance, Daniel H; Klein, Christopher J; Pittock, Sean J; Mckeon, Andrew

    2016-08-01

    Voltage-gated calcium-channel autoimmunity (VGCC-P/Q and VGCC-N types) occurs beyond Lambert-Eaton syndrome and lung cancer. We reviewed records for 236 Mayo Clinic patients with VGCC antibodies found in evaluation for paraneoplastic neurological autoimmunity (generally without myasthenic syndromes). VGCC autoantibodies were detected in 3.4% of neurological patients, 1.7% of healthy controls, and 4% of neurologically asymptomatic lung cancer controls. Fifty neurological patients (21%) had ≥ 1 neoplasm, historically (46) or detected prospectively [small-cell lung carcinoma (2), breast adenocarcinoma (2), lymphoma (1), and suspected tonsillar carcinoma (1)]. Autoimmune neurological diagnosis frequencies (encephalopathy, ataxia, myelopathy, neuropathy, neuromuscular junction disorder, and myopathy) among patients with medium values (24%; 0.10-0.99 nmol/L) or low values (19%; 0.03-0.10 nmol/L) were fewer than among patients with antibody values exceeding 1.00 nmol/L (71%; P = 0.02 and 0.004, respectively). Among neuronal VGCC-autoantibody-seropositive patients, autoimmune neurological phenotypes and cancer types are diverse. Cautious interpretation of results (particularly medium and low values) is advised. Muscle Nerve, 2016 Muscle Nerve 54: 220-227, 2016. © 2016 Wiley Periodicals, Inc.

  8. A clinical implementation of in vivo dosimetry with n-type Isorad semiconductor diodes

    Directory of Open Access Journals (Sweden)

    Rutonjski Laza M.

    2014-01-01

    Full Text Available The study was aimed to check the radiotherapy treatment accuracy and definition of action levels during implementation of in vivo dosimetry as a part of quality assurance program. The calibration and correction factors for in vivo entrance dose measurements for six n-type Isorad semiconductor diodes were determined as recommended by the European Society for Radiotherapy and Oncology Booklet No. 5. The patients for in vivo measurements have been divided in groups, according to the treatment site/techique, in order to investigate and detect the groups where the uncertainty was larger or where a systematic error occurred. The tolerance/action levels for all groups were also defined and checked. In this study, the entrance dose measurements were performed for total of 451 treatment fields, and 338 patients over one year period. The mean value and the standard deviation for different groups were: breast +1.0% ± 2.89%(1 SD, brain, and head and neck - +0.74% ± 2.04%(1 SD, and isocentric pelvis and abdomen - +0.1% ± 2.86%(1 SD. All measurements - +0.72% ± 2.64%(1 SD. In our experience, systematic in vivo dosimetry proved to be a very useful tool for quality assurance of patient's plan and treatment, both in detecting systematic errors and for estimating the accuracy of radiotherapy treatment delivery.

  9. Positron annihilation measurements in high-energy alpha-irradiated n-type gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Sandip; Mandal, Arunava; SenGupta, Asmita [Visva-Bharati, Department of Physics, Santiniketan, West Bengal (India); Roychowdhury, Anirban [UGC-DAE Consortium for Scientific Research, Kolkata Centre, Kolkata, West Bengal (India)

    2015-07-15

    Positron annihilation lifetime spectroscopy and Doppler broadening annihilation line-shape measurements have been carried out in 40-MeV alpha-irradiated n-type GaAs. After irradiation, the sample has been subjected to an isochronal annealing over temperature region of 25-800 C with an annealing time of 30 min at each set temperature. After each annealing, the positron measurements are taken at room temperature. Formation of radiation-induced defects and their recovery with annealing temperature are investigated. The lifetime spectra of the irradiated sample have been fitted with two lifetimes. The average positron lifetime τ{sub avg} = 244 ps at room temperature after irradiation indicates the presence of defects, and the value of τ{sub 2} (262 ps) at room temperature suggests that the probable defects are mono-vacancies. Two distinct annealing stages in τ{sub avg} at 400-600 C and at 650-800 C are observed. The variations in line-shape parameter (S) and defect-specific parameter (R) during annealing in the temperature region 25-800 C resemble the behaviour of τ{sub avg} indicating the migration of vacancies, formation of vacancy clusters and the disappearance of defects between 400 and 800 C. (orig.)

  10. Effect of Sm doping on the physical properties of ZnO thin films deposited by spray pyrolysis technique

    Science.gov (United States)

    Velusamy, P.; Babu, R. Ramesh; Aparna, K. T.

    2017-05-01

    Undoped and Sm doped ZnO thin films have been prepared by chemical spray pyrolysis method on a glass substrate at 430°C. The physical properties of undoped and Sm doped ZnO thin films are characterized by XRD, FE-SEM, UV-VIS spectroscopy, Hall measurement and PL analysis. XRD pattern reveals that all the films are polycrystalline nature. The FE-SEM study of CdO shows the smooth and uniform surface with the spherical shaped particle. The electrical study reveals the n-type semiconductor and the optical study shows that Sm doped ZnO thin films about 92% transparency and optical band gap vary between 3.266-3.276 eV. Sm doped ZnO thin films have strong green emission behavior.

  11. Temperature-dependent thermal and thermoelectric properties of n -type and p -type S c1 -xM gxN

    Science.gov (United States)

    Saha, Bivas; Perez-Taborda, Jaime Andres; Bahk, Je-Hyeong; Koh, Yee Rui; Shakouri, Ali; Martin-Gonzalez, Marisol; Sands, Timothy D.

    2018-02-01

    Scandium Nitride (ScN) is an emerging rocksalt semiconductor with octahedral coordination and an indirect bandgap. ScN has attracted significant attention in recent years for its potential thermoelectric applications, as a component material in epitaxial metal/semiconductor superlattices, and as a substrate for defect-free GaN growth. Sputter-deposited ScN thin films are highly degenerate n -type semiconductors and exhibit a large thermoelectric power factor of ˜3.5 ×10-3W /m -K2 at 600-800 K. Since practical thermoelectric devices require both n- and p-type materials with high thermoelectric figures-of-merit, development and demonstration of highly efficient p-type ScN is extremely important. Recently, the authors have demonstrated p-type S c1 -xM gxN thin film alloys with low M gxNy mole-fractions within the ScN matrix. In this article, we demonstrate temperature dependent thermal and thermoelectric transport properties, including large thermoelectric power factors in both n- and p-type S c1 -xM gxN thin film alloys at high temperatures (up to 850 K). Employing a combination of temperature-dependent Seebeck coefficient, electrical conductivity, and thermal conductivity measurements, as well as detailed Boltzmann transport-based modeling analyses of the transport properties, we demonstrate that p-type S c1 -xM gxN thin film alloys exhibit a maximum thermoelectric power factor of ˜0.8 ×10-3W /m -K2 at 850 K. The thermoelectric properties are tunable by adjusting the M gxNy mole-fraction inside the ScN matrix, thereby shifting the Fermi energy in the alloy films from inside the conduction band in case of undoped n -type ScN to inside the valence band in highly hole-doped p -type S c1 -xM gxN thin film alloys. The thermal conductivities of both the n- and p-type films were found to be undesirably large for thermoelectric applications. Thus, future work should address strategies to reduce the thermal conductivity of S c1 -xM gxN thin-film alloys, without affecting

  12. Nitrogen-doped graphene oxide quantum dots as photocatalysts for overall water-splitting under visible light illumination.

    Science.gov (United States)

    Yeh, Te-Fu; Teng, Chiao-Yi; Chen, Shean-Jen; Teng, Hsisheng

    2014-05-28

    Nitrogen-doped graphene oxide quantum dots exhibit both p- and n-type conductivities and catalyze overall water-splitting under visible-light irradiation. The quantum dots contain p-n type photochemical diodes, in which the carbon sp(2) clusters serve as the interfacial junction. The active sites for H2 and O2 evolution are the p- and n-domains, respectively, and the reaction mimics biological photosynthesis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Tetrahidrokanabinol kao doping

    OpenAIRE

    Milošević, Marcela

    2015-01-01

    Doping je jedan od glavnih problema suvremenog sporta. Definira se kao kršenje jednog ili više antidopinških pravila definiranih odredbama Svjetskog antidopinškog kodeksa. Prema tri WADA-ina kriterija među doping sredstva spada i tetrahidrokarabinol, porijeklom iz biljke Cannabis sativa, Cannabinaceae. To je spoj iz skupine kanabinoida s najjačim psihoaktivnim djelovanjem. Za njegovo djelovanje zaslužni su mehanizmi farmakokinetike i farmakodinamike. Ovisno o načinu primjene apsorpcija mu var...

  14. Investigation of the optoelectronic behavior of Pb-doped CdO nanostructures

    Science.gov (United States)

    Eskandari, Abdollah; Jamali-Sheini, Farid; Cheraghizade, Mohsen; Yousefi, Ramin

    2018-03-01

    Un- and lead (Pb)-doped cadmium oxide (CdO) semiconductor nanostructures were synthesized by a sonochemical method to study their physical properties. The obtained X-ray diffraction (XRD) patterns indicated cubic CdO crystalline structures for all samples and showed that the crystallite size of CdO increases with Pb addition. Scanning electron microscopy (SEM) images of the nanostructures illustrated agglomerated oak-like particles for the Pb-doped CdO nanostructures. Furthermore, optical studies suggested that the emission band gap energy of the CdO nanostructures lies in the range of 2.27-2.38 eV and crystalline defects increase by incorporation of Pb atoms in the CdO crystalline lattice. In addition, electrical experiments declared that the n-type electrical nature of the un- and Pb-doped CdO nanostructures and the minimum of Pb atoms lead to a high carrier concentration.

  15. Enhancing the thermopower and tuning the resistivity in Bi2Se3 with Fe-doping

    Science.gov (United States)

    Sk, Rejaul; Shirolkar, Mandar M.; Dhara, Barun; Kulkarni, Sulabha; Deshpande, Aparna

    2015-10-01

    We report the synthesis of undoped bismuth selenide (Bi2Se3) and iron (Fe) doped (upto 30%) bismuth selenide (Bi2Se3) powder samples by polyol method. The samples consist of submicron size platelets with thickness ranging between 5 and 10 nm. The temperature dependent thermopower measurements reveal all these materials to be n-type in nature and the room temperature thermopower increases with Fe concentration. The electrical resistivity of undoped Bi2Se3 shows metallic behavior in 5-300 K range, but the Fe-doped samples show semiconducting behavior. Thus we find Fe-doping of Bi2Se3 to be a promising route for tuning the properties of Bi2Se3 for applications.

  16. Itinerant magnetism in doped semiconducting β-FeSi₂ and CrSi₂.

    Science.gov (United States)

    Singh, David J; Parker, David

    2013-12-17

    Novel or unusual magnetism is a subject of considerable interest, particularly in metals and degenerate semiconductors. In such materials the interplay of magnetism, transport and other Fermi liquid properties can lead to fascinating physical behavior. One example is in magnetic semiconductors, where spin polarized currents may be controlled and used. We report density functional calculations predicting magnetism in doped semiconducting β-FeSi₂ and CrSi₂ at relatively low doping levels particularly for n-type. In this case, there is a rapid cross-over to a half-metallic state as a function of doping level. The results are discussed in relation to the electronic structure and other properties of these compounds.

  17. Effect of Sr doping on LaTiO3 thin films

    International Nuclear Information System (INIS)

    Vilquin, B.; Kanki, T.; Yanagida, T.; Tanaka, H.; Kawai, T.

    2005-01-01

    We report on the electric properties of La 1-x Sr x TiO 3 (0 ≤ x ≤ 0.5) thin films fabricated by pulsed laser deposition method. Crystallographic measurement of the thin films showed the epitaxial c-axis perovskite structure. The electric property of LaTiO 3 thin film, which is a typical Mott insulative material in bulk, showed insulative behaviour, while the Sr-doped films showed metallic conduction suffering electron-electron scattering. Below x = 0.1, the major carrier type was identified to be hole, and switched to electron with further increasing Sr-doping above x = 0.15. In fact, the switching from p-type to n-type for La 1-x Sr x TiO 3 thin films is first demonstrated in this study. The transition suggests that effective Coulomb gap vanishes due to over-additional Sr doping

  18. Nanofabrication of structures for the study of nanowire doping

    Science.gov (United States)

    Eichfeld, Chad

    A variety of techniques were developed for the characterization of nanowires and applied to the study of nanowire growth and dopant incorporation. A technique to selectively plate gold on the n-type regions of modulation-doped silicon nanowires for junction delineation was developed. The ability to electrolessly deposit metal on segments of nanowires could also facilitate electrical contact formation. More complicated structures such as controlled placement of forks along the nanowire could be made by placement of the gold catalyst at predetermined locations along a nanowire followed by a second growth. Additionally, a process was developed that focuses on using this plating ability to grow silicon nanowires horizontally from pre-determined locations. The processing was worked out and nanowires were grown horizontally from plated gold, but the selectivity of gold limited the ability to grow wires in only the desired locations. A silicon nanowire local electrode atom probe test structure is discussed from the initial design steps to successfully using the test structure to analyze silicon nanowires. Initial results using laser pulsed assisted local electrode atom probe indicated that the thermal properties of the nanowire prevent the tip from cooling fast enough and resulted in large thermal tails in the mass spectra. Thermal modeling was used to identify what nanowire diameters and metal coatings would allow the nanowire tip to cool sufficiently fast. A silver catalyzed silicon nanowire with a diameter large enough to allow for sufficient cooling was analyzed, and the concentration of silver in the silicon nanowire was below the detection limit of 10 ppm or 5 x 10 17 cm-3. The growth and characterization of Al catalyzed silicon nanowires is also discussed. Nanowires were grown at higher pressures and using H 2 as a carrier gas resulting in much higher growth rates than previously observed for Al catalyzed nanowires in the literature. The nanowires were

  19. Study of fully-depleted Ge double-gate n-type Tunneling Field-Effect Transistors for improvement in on-state current and sub-threshold swing

    Science.gov (United States)

    Liu, Xiangyu; Hu, Huiyong; Wang, Meng; Zhang, Heming; Cui, Shimin; Shu, Bin; Wang, Bin

    2018-01-01

    In this paper, a fully-depleted (FD) Ge double-gate (DG) n-type Tunneling Field-Effect Transistors (TFET) structure is studied in detail by two-dimensional numerical simulation. The simulation results indicated that the on-state current Ion and on-off ratio of the FD Ge DG-TFET increases about 1 order of magnitude comparing with the Conventional Ge DG-TFET, and Ion=3.95×10-5 A/μm and the below 60 mV/decade subthreshold swing S=26.4 mV/decade are achieved with the length of gate LD=20 nm, the workfuntion of metal gate Φm=0.2 eV and the doping concentration of n+-type-channel ND=1×1018 cm-3. Moreover, the impacts of Φm, ND and LD are investigated. The simulation results indicated that the off-state current Ioff includes the tunneling current at the middle of channel IB the gated-induced drain leakage (GIDL) current IGIDL. With optimized Φm and ND, Ioff is reduced about 2 orders of magnitude to 2.5×10-13 A/μm with LD increasing from 40 nm to 100 nm, and on-off ratio is increased to 1.58×107.

  20. Solution-processed, molecular photovoltaics that exploit hole transfer from non-fullerene, n-type materials

    KAUST Repository

    Douglas, Jessica D.

    2014-05-12

    Solution-processed organic photovoltaic devices containing p-type and non-fullerene n-type small molecules obtain power conversion efficiencies as high as 2.4%. The optoelectronic properties of the n-type material BT(TTI-n12)2 allow these devices to display high open-circuit voltages (>0.85 V) and generate significant charge carriers through hole transfer in addition to the electron-transfer pathway, which is common in fullerene-based devices. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Identification of VanN-type vancomycin resistance in an Enterococcus faecium isolate from chicken meat in Japan.

    Science.gov (United States)

    Nomura, Takahiro; Tanimoto, Koichi; Shibayama, Keigo; Arakawa, Yoshichika; Fujimoto, Shuhei; Ike, Yasuyoshi; Tomita, Haruyoshi

    2012-12-01

    Five VanN-type vancomycin-resistant Enterococcus faecium strains were isolated from a sample of domestic chicken meat in Japan. All isolates showed low-level resistance to vancomycin (MIC, 12 mg/liter) and had the same pulsed-field gel electrophoresis profile. The vancomycin resistance was encoded on a large plasmid (160 kbp) and was expressed constitutively. The VanN-type resistance operon was identical to the first resistance operon to be reported, with the exception of a 1-bp deletion in vanT(N) and a 1-bp substitution in vanS(N).

  2. Thermoelectric n-type silicon germanium synthesized by unidirectional solidification in microgravity

    Energy Technology Data Exchange (ETDEWEB)

    Okutani, Takeshi, E-mail: okutani@ynu.ac.jp [Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya-Ku, Yokohama 240-8501 (Japan); Kabeya, Yuto [Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya-Ku, Yokohama 240-8501 (Japan); Nagai, Hideaki [National Institute of Advanced Industrial Science and Technology,1-1-1 Higashi, Tsukuba 305-8565 (Japan)

    2013-02-25

    Highlights: Black-Right-Pointing-Pointer Thermoelectric n-type SiGe was synthesized by unidirectional solidification. Black-Right-Pointing-Pointer SiGe had dendrite structure aligned along the solidification direction. Black-Right-Pointing-Pointer SiGe solidified unidirectionally in microgravity had crystalline orientation. Black-Right-Pointing-Pointer Anisotropy of electric conductivity was seen in orthogonal solidification directions. Black-Right-Pointing-Pointer ZT of Si{sub 0.7}Ge{sub 0.3}-1at%P solidified in microgravity at 1000 K was 1.19. - Abstract: Thermoelectric n-type Si{sub 0.2}Ge{sub 0.8} and Si{sub 0.7}Ge{sub 0.3} added 1at%P for Si-Ge were synthesized by unidirectional solidification in microgravity. Microgravity with {+-}10{sup -2} g for 0.46 s was obtained in free fall using a 2 m-drop tower. The microstructure of the sample solidified in microgravity and 1 g was dendrite on the surface that contacted a Cu chill block. The microstructure of the cross section along the cooling direction was dendrite and the columnar dendrite structure was mainly aligned along the solidification direction. The dendrite became larger with depth from the surface that contacted the Cu chill block, and the width of the primary dendrite arm solidified in microgravity exceeded that in 1 g. Ge was segregated to the secondary arm of columnar dendrite. The Si/Ge atomic ratio in the primary and secondary arm of Si{sub 0.7}Ge{sub 0.3}-1at%P solidified in 1 g and microgravity was slightly higher than that of solidified Si{sub 0.8}Ge{sub 0.2}-1at%P in 1 g and microgravity. The secondary arm of solidified Si{sub 0.7}Ge{sub 0.3}-1at%P was wider than that of solidified Si{sub 0.8}Ge{sub 0.2}-1at%P. P was distributed uniformly in Si-Ge solidified in microgravity. The electrical conductivities of Si{sub 0.8}Ge{sub 0.2}-1at%P and Si{sub 0.7}Ge{sub 0.3}-1at%P were anisotropic in directions along and perpendicular to the solidification direction. The dimensionless Figure of Merit, ZT, of

  3. Electronic properties and morphology of copper oxide/n-type silicon heterostructures

    Science.gov (United States)

    Lindberg, P. F.; Gorantla, S. M.; Gunnæs, A. E.; Svensson, B. G.; Monakhov, E. V.

    2017-08-01

    Silicon-based tandem heterojunction solar cells utilizing cuprous oxide (Cu2O) as the top absorber layer show promise for high-efficiency conversion and low production cost. In the present study, single phase Cu2O films have been realized on n-type Si substrates by reactive magnetron sputtering at 400 °C. The obtained Cu2O/Si heterostructures have subsequently been heat treated at temperatures in the 400-700 °C range in Ar flow and extensively characterized by x-ray diffraction (XRD) measurements, transmission electron microscopy (TEM) imaging and electrical techniques. The Cu2O/Si heterojunction exhibits a current rectification of ~5 orders of magnitude between forward and reverse bias voltages. High resolution cross-sectional TEM-images show the presence of a ~2 nm thick interfacial SiO2 layer between Cu2O and the Si substrate. Heat treatments below 550 °C result in gradual improvement of crystallinity, indicated by XRD. At and above 550 °C, partial phase transition to cupric oxide (CuO) occurs followed by a complete transition at 700 °C. No increase or decrease of the SiO2 layer is observed after the heat treatment at 550 °C. Finally, a thin Cu-silicide layer (Cu3Si) emerges below the SiO2 layer upon annealing at 550 °C. This silicide layer influences the lateral current and voltage distributions, as evidenced by an increasing effective area of the heterojunction diodes.

  4. Doping in sport

    African Journals Online (AJOL)

    Objective. To determine the attitudes, beliefs and knowledge of talented young athletes residing in Gauteng regarding prohibited performance-enhancing drugs (PEDs) and anti-doping rules and regulations. Methods. This was a survey study using a quantitative research approach. South African TuksSport academy ...

  5. Doped barium titanate nanoparticles

    Indian Academy of Sciences (India)

    We have synthesized nickel (Ni) and iron (Fe) ion doped BaTiO3 nanoparticles through a chemical route using polyvinyl alcohol (PVA). The concentration of dopant varies from 0 to 2 mole% in the specimens. The results from X-ray diffractograms and transmission electron micrographs show that the particle diameters in the ...

  6. Doped barium titanate nanoparticles

    Indian Academy of Sciences (India)

    Wintec

    Abstract. We have synthesized nickel (Ni) and iron (Fe) ion doped BaTiO3 nanoparticles through a chemical route using polyvinyl alcohol (PVA). The concentration of dopant varies from 0 to 2 mole% in the specimens. The results from X-ray diffractograms and transmission electron micrographs show that the particle ...

  7. Role Models on Dope

    DEFF Research Database (Denmark)

    Christiansen, Ask Vest; Gleaves, John

    2014-01-01

    Compared to football-players cyclists are virtuous role models. Yes, Lance Armstrong, Michael Rasmussen and other riders have doped, and because of this they have received the predicate as the most immoral athletes in the sporting world. But if morality is not only a question of whether a person...

  8. BLOOD DOPING AND RISKS

    Directory of Open Access Journals (Sweden)

    Goran Vasić

    2015-05-01

    Full Text Available Doping is the way in which athletes misuse of chemicals and other types of medical interventions (eg, blood replacement, try to get ahead in the results of other athletes or their performance at the expense of their own health. The aim of this work is the analysis of blood doping and the display of negative consequences that this way of increasing capabilities brings. Method: The methodological work is done descriptively. Results: Even in 1972 at the Stockholm Institute for gymnastics and sport, first Dr. Bjorn Ekblom started having blood doping. Taken from the blood, athletes through centifuge separating red blood cells from blood plasma, which is after a month of storage in the fridge, every athlete back into the bloodstream. Tests aerobic capacity thereafter showed that the concerned athletes can run longer on average for 25% of the treadmill than before. Discussion: Blood doping carries with it serious risks, excessive amount of red cells “thickens the blood,” increased hematocrit, which reduces the heart’s ability to pump blood to the periphery. All this makes it difficult for blood to flow through blood vessels, and there is a great danger that comes to a halt in the circulation, which can cause cardiac arrest, stroke, pulmonary edema, and other complications that can be fatal.

  9. Inhomogeneous Si-doping of gold-seeded InAs nanowires grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Rolland, Chloe; Coinon, Christophe; Wallart, Xavier; Leturcq, Renaud [Institute of Electronics Microelectronics and Nanotechnology, UMR CNRS 8520, ISEN Department, Avenue Poincare, CS60069, 59652 Villeneuve d' Ascq Cedex (France); Caroff, Philippe [Institute of Electronics Microelectronics and Nanotechnology, UMR CNRS 8520, ISEN Department, Avenue Poincare, CS60069, 59652 Villeneuve d' Ascq Cedex (France); Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia)

    2013-06-03

    We have investigated in situ Si doping of InAs nanowires grown by molecular beam epitaxy from gold seeds. The effectiveness of n-type doping is confirmed by electrical measurements showing an increase of the electron density with the Si flux. We also observe an increase of the electron density along the nanowires from the tip to the base, attributed to the dopant incorporation on the nanowire facets whereas no detectable incorporation occurs through the seed. Furthermore, the Si incorporation strongly influences the lateral growth of the nanowires without giving rise to significant tapering, revealing the complex interplay between axial and lateral growth.

  10. Electrical properties of MOS structures on nitrogen-doped Czochralski-grown silicon: A positron annihilation study

    International Nuclear Information System (INIS)

    Slugen, V.; Harmatha, L.; Tapajna, M.; Ballo, P.; Pisecny, P.; Sik, J.; Koegel, G.; Krsjak, V.

    2006-01-01

    Measurements of interface trap density, effective generation lifetime (GL) and effective surface generation velocity have been performed using different methods on selected MOS structures prepared on nitrogen-doped Czochralski-grown (NCz) silicon. The application of the positron annihilation technique using a pulsed low energy positron system (PLEPS) focused on the detection of nitrogen-related defects in NCz silicon in the near surface region. In the case of p-type Cz silicon, all the results could be used for the testing of homogeneity. In n-type Cz silicon, positron annihilation was found insensitive to nitrogen doping

  11. Cubic to tetragonal phase transition of Tm3+ doped nanocrystals in oxyfluoride glass ceramics

    International Nuclear Information System (INIS)

    Li, Yiming; Fu, Yuting; Shi, Yahui; Zhang, Xiaoyu; Yu, Hua; Zhao, Lijuan

    2016-01-01

    Tm 3+ ions doped β-PbF 2 nanocrystals in oxyfluoride glass ceramics with different doping concentrations and thermal temperatures are prepared by a traditional melt-quenching and thermal treatment method to investigate the structure and the phase transition of Tm 3+ doped nanocrystals. The structures are characterized by X-ray diffraction Rietveld analysis and confirmed with numerical simulation. The phase transitions are proved further by the emission spectra. Both of the doping concentration and thermal temperature can induce an O h to D 4h site symmetry distortion and a cubic to tetragonal phase transition. The luminescence of Tm 3+ doped nanocrystals at 800 nm was modulated by the phase transition of the surrounding crystal field

  12. Highly n -doped graphene generated through intercalated terbium atoms

    Science.gov (United States)

    Daukiya, L.; Nair, M. N.; Hajjar-Garreau, S.; Vonau, F.; Aubel, D.; Bubendorff, J. L.; Cranney, M.; Denys, E.; Florentin, A.; Reiter, G.; Simon, L.

    2018-01-01

    We obtained highly n -type doped graphene by intercalating terbium atoms between graphene and SiC(0001) through appropriate annealing in ultrahigh vacuum. After terbium intercalation angle-resolved-photoelectron spectroscopy (ARPES) showed a drastic change in the band structure around the K points of the Brillouin zone: the well-known conical dispersion band of a graphene monolayer was superposed by a second conical dispersion band of a graphene monolayer with an electron density reaching 1015cm-2 . In addition, we demonstrate that atom intercalation proceeds either below the buffer layer or between the buffer layer and the monolayer graphene. The intercalation of terbium below a pure buffer layer led to the formation of a highly n -doped graphene monolayer decoupled from the SiC substrate, as evidenced by ARPES and x-ray photoelectron spectroscopy measurements. The band structure of this highly n -doped monolayer graphene showed a kink (a deviation from the linear dispersion of the Dirac cone), which has been associated with an electron-phonon coupling constant one order of magnitude larger than those usually obtained for graphene with intercalated alkali metals.

  13. Diffusion in Intrinsic and Highly Doped III-V Semiconductors

    CERN Multimedia

    Stolwijk, N

    2002-01-01

    %title\\\\ \\\\Diffusion plays a key role in the fabrication of semiconductor devices. The diffusion of atoms in crystals is mediated by intrinsic point defects. Investigations of the diffusion behaviour of self- and solute atoms on the Ga sublattice of gallium arsenide led to the conclusion that in intrinsic and n-type material charged Ga vacancies are involved in diffusion processes whereas in p-type material diffusion if governed by charged Ga self-interstitials. Concerning the As sublattice of gallium arsenide there is a severe lack of reliable diffusion data. The few available literature data on intrinsic GaAs are not mutually consistent. A systematic study of the doping dependence of diffusion is completely missing. The most basic diffusion process - self-diffusion of As and its temperature and doping dependence - is practically not known. For GaP a similar statement holds.\\\\ \\\\The aim of the present project is to perform a systematic diffusion study of As diffusion in intrinsic and doped GaAs and in GaP. P...

  14. Formation energy and photoelectrochemical properties of BiVO4 after doping at Bi3+ or V5+ sites with higher valence metal ions.

    Science.gov (United States)

    Luo, Wenjun; Wang, Jiajia; Zhao, Xin; Zhao, Zongyan; Li, Zhaosheng; Zou, Zhigang

    2013-01-21

    Photoelectrochemical water splitting is an attractive method to produce H(2) fuel from solar energy and water. Ion doping with higher valence states was used widely to enhance the photocurrent of an n-type oxide semiconductor. In this study, the different doping sites and the photoelectrochemical properties of Mo(6+), W(6+) and Sn(4+)-doped BiVO(4) were studied systematically. The results suggested that Mo(6+) or W(6+)-doped BiVO(4) had a much higher photocurrent while the photocurrent of Sn(4+)-doped BiVO(4) did not change obviously. Raman and XPS were used to identify the doping sites in the BiVO(4) crystal lattice. It was found that Mo or W substituted V sites but Sn did not substitute Bi sites. Results of theoretical calculation indicated that a higher formation energy and lower solubility of impurity ions led to serious SnO(2) segregation on the surface of the Sn(4+)-doped BiVO(4) thin film, which was the main reason for the poor performance of Sn-doped BiVO(4). The higher formation energy of Sn(4+) came from the large mismatch of ion radius and different outer shell electron distribution. These results can offer guidance in choosing suitable doping ions for other semiconductor photoelectrodes.

  15. Electron-phonon interactions in n-type In0.53Ga0.47As and In0.52Al0.48As studied by inelastic light scattering

    Science.gov (United States)

    Maslar, J. E.; Dorsten, J. F.; Bohn, P. W.; Agarwala, S.; Adesida, I.; Caneau, C.; Bhat, R.

    1994-12-01

    Room-temperature Raman spectroscopy was used to characterize n-type-doped In0.53Ga0.47As and In0.52Al0.48As layers by observing coupled longitudinal-optical (LO) -phonon-plasmon mode spectra as a function of carrier density. Carrier densities determined from the high-frequency L+ coupled mode shift in the Raman spectra were compared to carrier densities determined from electrochemical capacitance-voltage profiling measurements. In In0.53Ga0.47As with carrier densities n<=8×1017 cm-3 accurate determination of carrier densities from the Raman spectra was hindered by Landau damping and small L+ mode dispersion. Better agreement between the two techniques was observed in In0.53Ga0.47As and In0.52Al0.48As for carrier densities of about 8×1017 cm-3 and higher, doping levels at which Landau damping is less pronounced. Surface band bending was evaluated from changes in Raman intensity as a function of carrier density of dipole-allowed LO-phonon modes originating in the surface space-charge region. Values for the surface built-in potential determined from the Raman spectra were found to be smaller than those obtained from electrical measurements. The discrepancy is attributed to screening of the surface dipole by photogenerated carriers.

  16. Characterization of epitaxial GaAs MOS capacitors using atomic layer-deposited TiO2/Al2O3 gate stack: study of Ge auto-doping and p-type Zn doping

    Science.gov (United States)

    2012-01-01

    Electrical and physical properties of a metal-oxide-semiconductor [MOS] structure using atomic layer-deposited high-k dielectrics (TiO2/Al2O3) and epitaxial GaAs [epi-GaAs] grown on Ge(100) substrates have been investigated. The epi-GaAs, either undoped or Zn-doped, was grown using metal-organic chemical vapor deposition method at 620°C to 650°C. The diffusion of Ge atoms into epi-GaAs resulted in auto-doping, and therefore, an n-MOS behavior was observed for undoped and Zn-doped epi-GaAs with the doping concentration up to approximately 1017 cm-3. This is attributed to the diffusion of a significant amount of Ge atoms from the Ge substrate as confirmed by the simulation using SILVACO software and also from the secondary ion mass spectrometry analyses. The Zn-doped epi-GaAs with a doping concentration of approximately 1018 cm-3 converts the epi-GaAs layer into p-type since the Zn doping is relatively higher than the out-diffused Ge concentration. The capacitance-voltage characteristics show similar frequency dispersion and leakage current for n-type and p-type epi-GaAs layers with very low hysteresis voltage (approximately 10 mV). PACS: 81.15.Gh. PMID:22297193

  17. Characterization of epitaxial GaAs MOS capacitors using atomic layer-deposited TiO2/Al2O3 gate stack: study of Ge auto-doping and p-type Zn doping.

    Science.gov (United States)

    Dalapati, Goutam Kumar; Shun Wong, Terence Kin; Li, Yang; Chia, Ching Kean; Das, Anindita; Mahata, Chandreswar; Gao, Han; Chattopadhyay, Sanatan; Kumar, Manippady Krishna; Seng, Hwee Leng; Maiti, Chinmay Kumar; Chi, Dong Zhi

    2012-02-02

    Electrical and physical properties of a metal-oxide-semiconductor [MOS] structure using atomic layer-deposited high-k dielectrics (TiO2/Al2O3) and epitaxial GaAs [epi-GaAs] grown on Ge(100) substrates have been investigated. The epi-GaAs, either undoped or Zn-doped, was grown using metal-organic chemical vapor deposition method at 620°C to 650°C. The diffusion of Ge atoms into epi-GaAs resulted in auto-doping, and therefore, an n-MOS behavior was observed for undoped and Zn-doped epi-GaAs with the doping concentration up to approximately 1017 cm-3. This is attributed to the diffusion of a significant amount of Ge atoms from the Ge substrate as confirmed by the simulation using SILVACO software and also from the secondary ion mass spectrometry analyses. The Zn-doped epi-GaAs with a doping concentration of approximately 1018 cm-3 converts the epi-GaAs layer into p-type since the Zn doping is relatively higher than the out-diffused Ge concentration. The capacitance-voltage characteristics show similar frequency dispersion and leakage current for n-type and p-type epi-GaAs layers with very low hysteresis voltage (approximately 10 mV).PACS: 81.15.Gh.

  18. Turán type inequalities for the partial sums of the generating functions of Bernoulli and Euler numbers

    DEFF Research Database (Denmark)

    Koumandos, Stamatis; Pedersen, Henrik Laurberg

    2012-01-01

    Turán type inequalities for the partial sums of the generating functions of the Bernoulli and Euler numbers are established. They are shown to follow from a general result relating Turán inequalities of partial sums with Turán inequalities of the corresponding remainders in any Maclaurin expansion...

  19. Phonon-limited mobility in n-type single-layer MoS2 from first principles

    DEFF Research Database (Denmark)

    Kaasbjerg, Kristen; Thygesen, Kristian S.; Jacobsen, Karsten W.

    2012-01-01

    We study the phonon-limited mobility in intrinsic n-type single-layer MoS2 for temperatures T > 100 K. The materials properties including the electron-phonon interaction are calculated from first principles and the deformation potentials and Frohlich interaction in single-layer MoS2 are establish...

  20. High-Performance Near-Infrared Phototransistor Based on n-Type Small-Molecular Organic Semiconductor

    KAUST Repository

    Li, Feng

    2016-12-13

    A solution-processed near-infrared (NIR) organic phototransistor (OPT) based on n-type organic small molecular material BODIPY-BF2 has been successfully fabricated. Its unprecedented performance, as well as its easy fabrication and good stability, mark this BODIPY-BF2 based OPT device as a very promising candidate for optoelectronic applications in the NIR regime.

  1. Electrical Behavior on N-Type Dopants in AlGaAs Alloys: Shallow Levels and DX Centers

    Science.gov (United States)

    1990-11-01

    FORCE OFFICE OF SCIENTIFIC RESEARCH GRANT AFOSR-88-0316 EOSRD-LONDON DEPARTAMENTO DE INGENIERIA ELECTRONICA E.T.S. INGENIEROS DE TELECOMUNICACION ...INGENIEROS DE TELECOMUNICACION . MADRID OCTOBER 1990 2 ABSTRACT The electrical properties of n- type AlxGaixAs, for x > 0.2, are governed by deep donor

  2. N-type polymers as electron extraction layers in hybrid perovskite solar cells with improved ambient stability

    NARCIS (Netherlands)

    Shao, S.; Chen, Z.; Fang, H. -H.; ten Brink, G. H.; Bartesaghi, D.; Adjokatse, S.; Koster, L. J. A.; Kooi, B. J.; Facchetti, A.; Loi, M. A.

    2016-01-01

    We studied three n-type polymers of the naphthalenediimide-bithiophene family as electron extraction layers (EELs) in hybrid perovskite solar cells. The recombination mechanism in these devices is found to be heavily influenced by the EEL transport properties. The maximum efficiency of the devices

  3. Fluorinated copper-phthalocyanine-based n-type organic field-effect transistors with a polycarbonate gate insulator

    International Nuclear Information System (INIS)

    Sethuraman, Kunjithapatham; Kumar, Palanisamy; Santhakumar, Kannappan; Ochiai, Shizuyasu; Shin, Paikkyun

    2012-01-01

    Fluorinated copper-phthalocyanine (F 16 CuPc) thin films were prepared by using a vacuum evaporation technique and were applied to n-type organic field-effect transistors (OFETs) as active channel layers combined with a spin-coated polycarbonate thin-film gate insulator. The output characteristics of the resulting n-type OFET devices with bottom-gate/bottom-contact structures were investigated to evaluate the performances such as the field effect mobility (μ FE ), the on/off current ratio (I on/off ), and the threshold voltage (V th ). A relatively high field effect mobility of 6.0 x 10 -3 cm 2 /Vs was obtained for the n-type semiconductor under atmospheric conditions with an on/off current ratio of 1 x 10 4 and a threshold voltage of 5 V. The electron mobility of the n-type semiconductor was found to depend strongly on the growth temperature of the F 16 CuPc thin films. X-ray diffraction profiles showed that the crystallinity and the orientation of the F 16 CuPc on a polycarbonate thin film were enhanced with increasing growth temperature. Atomic force microscopy studies revealed various surface morphologies of the active layer. The field effect mobility of the F 16 CuPc-OFET was closely related to the crystallinity and the orientation of the F 16 CuPc thin film.

  4. A highly conducting graphene film with dual-side molecular n-doping

    Science.gov (United States)

    Kim, Youngsoo; Park, Jaesung; Kang, Junmo; Yoo, Je Min; Choi, Kyoungjun; Kim, Eun Sun; Choi, Jae-Boong; Hwang, Chanyong; Novoselov, K. S.; Hong, Byung Hee

    2014-07-01

    Doping is an efficient way to engineer the conductivity and the work function of graphene, which is, however, limited to wet-chemical doping or metal deposition particularly for n-doping, Here, we report a simple method of modulating the electrical conductivity of graphene by dual-side molecular n-doping with diethylenetriamine (DETA) on the top and amine-functionalized self-assembled monolayers (SAMs) at the bottom. The resulting charge carrier density of graphene is as high as -1.7 × 1013 cm-2, and the sheet resistance is as low as ~86 +/- 39 Ω sq-1, which is believed to be the lowest sheet resistance of monolayer graphene reported so far. This facile dual-side n-doping strategy would be very useful to optimize the performance of various graphene-based electronic devices.Doping is an efficient way to engineer the conductivity and the work function of graphene, which is, however, limited to wet-chemical doping or metal deposition particularly for n-doping, Here, we report a simple method of modulating the electrical conductivity of graphene by dual-side molecular n-doping with diethylenetriamine (DETA) on the top and amine-functionalized self-assembled monolayers (SAMs) at the bottom. The resulting charge carrier density of graphene is as high as -1.7 × 1013 cm-2, and the sheet resistance is as low as ~86 +/- 39 Ω sq-1, which is believed to be the lowest sheet resistance of monolayer graphene reported so far. This facile dual-side n-doping strategy would be very useful to optimize the performance of various graphene-based electronic devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00479e

  5. 279 Watt Metal-Wrap-Through module using industrial processes

    Energy Technology Data Exchange (ETDEWEB)

    Guillevin, N.; Heurtault, B.; Geerligs, L.J.; Anker, J.; Van Aken, B.B.; Bennett, I.J.; Jansen, M.J.; Berkeveld, L.D.; Weeber, A.W.; Bultman, J.H. [ECN Solar Energy, PO Box 1, 1755 ZG Petten (Netherlands); Wenchao, Zhao; Jianming, Wang; Ziqian, Wang; Yingle, Chen; Yanlong, Shen; Zhiyan, Hu; Gaofei, Li; Jianhui, Chen; Bo, Yu; Shuquan, Tian; Jingfeng, Xiong [Yingli Solar, 3399 Chaoyang North Street, Baoding (China)

    2012-09-15

    This paper describes results of metal wrap through (MWT) cells produced from n-type Czochralski silicon wafers, and modules produced from those cells. The use of n-type silicon as base material allows for high efficiencies: for front emitter contacted industrial cells, efficiencies up to 20% have been reported. MWT cells allow even higher cell efficiency due to reduced front metal coverage, and additionally full back-contacting of the MWT cells in a module results in reduced cell to module (CTM) fill factor losses. MWT cells were produced by industrial process technologies. The efficiency of the MWT cells reproducibly exceeds the efficiency of front contact cells based on the same technology by about 0.2-0.3%, and routes for further improvement are analyzed. 60-cell modules were produced from both types of cells (MWT and H-pattern front emitter). In a direct module performance comparison, the MWT module, based on integrated backfoil, produced 3% higher power output than the comparable tabbed front emitter contact module. CTM current differences arise from the higher packing density, and in this experiment from a lower reflectance of the backfoil, in MWT modules. CTM FF differences are related to resistive losses in copper circuitry on the backfoil versus tabs. The CTM FF loss of the MWT module was reduced by 2.2%abs compared to the tabbed front emitter contact module. Finally, simple process optimizations were tested to improve the n-type MWT cell and module efficiency. A module made using MWT cells of 19.6% average efficiency resulted in a power output of 279W. The cell and module results are analyzed and routes for improvements are discussed.

  6. Ultralow power complementary inverter circuits using axially doped p- and n-channel Si nanowire field effect transistors.

    Science.gov (United States)

    Van, Ngoc Huynh; Lee, Jae-Hyun; Whang, Dongmok; Kang, Dae Joon

    2016-06-09

    We have successfully synthesized axially doped p- and n-type regions on a single Si nanowire (NW). Diodes and complementary metal-oxide-semiconductor (CMOS) inverter devices using single axial p- and n-channel Si NW field-effect transistors (FETs) were fabricated. We show that the threshold voltages of both p- and n-channel Si NW FETs can be lowered to nearly zero by effectively controlling the doping concentration. Because of the high performance of the p- and n-type Si NW channel FETs, especially with regard to the low threshold voltage, the fabricated NW CMOS inverters have a low operating voltage (power dissipation (≤0.3 pW) at an input voltage of ±3 V. This result offers a viable way for the fabrication of a high-performance high-density logic circuit using a low-temperature fabrication process, which makes it suitable for flexible electronics.

  7. Perovskite Sr-doped LaCrO3 as a new p-type transparent conducting oxide

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hongliang; Du, Yingge; Papadogianni, Alexandra; Bierwagen, Oliver; Sallis, Shawn; Piper, Louis F. J.; Bowden, Mark E.; Shutthanandan, V.; Sushko, Petr; Chambers, Scott A.

    2015-09-16

    Transparent conducting oxides (TCOs) constitute a unique class of materials which combine the seemingly mutually exclusive properties of electrical conductivity and optical transparency in a single material. TCOs are useful for a wide range of applications including solar cells, displays, light emitting diodes and transparent electronics. Simple post-transition metal oxides such as ZnO, In2O3 and SnO2 are wide gap insulators in which the ionic character generates an oxygen 2p-derived valence band (VB) and a metal s-derived conduction band (CB), resulting in large optical band gaps (>3.0 eV) and excellent n-type conductivity when donor doped. In contrast, the development of efficient p-type TCOs remains a global materials challenge. Converting n-type oxides to p-type analogs by acceptor doping is extremely difficult and these materials display poor conductivity.

  8. Versatile and Tunable Transparent Conducting Electrodes Based on Doped Graphene

    KAUST Repository

    Mansour, Ahmed E.

    2016-11-25

    The continued growth of the optoelectronics industry and the emergence of wearable and flexible electronics will continue to place an ever increasing pressure on replacing ITO, the most widely used transparent conducting electrode (TCE). Among the various candidates, graphene shows the highest optical transmittance in addition to promising electrical transport properties. The currently available large-scale synthesis routes of graphene result in polycrystalline samples rife with grain boundaries and other defects which limit its transport properties. Chemical doping of graphene is a viable route towards increasing its conductivity and tuning its work function. However, dopants are typically present at the surface of the graphene sheet, making them highly susceptible to degradation in environmental conditions. Few-layers graphene (FLG) is a more resilient form of graphene exhibiting higher conductivity and performance stability under stretching and bending as contrasted to single-layer graphene. In addition FLG presents the advantage of being amenable bulk doping by intercalation. Herein, we explore non-covalent doping routes of CVD FLG, such as surface doping, intercalation and combination thereof, through in-depth and systematic characterization of the electrical transport properties and energy levels shifts. The intercalation of FLG with Br2 and FeCl3 is demonstrated, showing the highest improvements of the figure of merit of TCEs of any doping scheme, which results from up to a five-fold increase in conductivity while maintaining the transmittance within 3% of that for the pristine value. Importantly the intercalation yields TCEs that are air-stable, due to encapsulation of the intercalant in the bulk of FLG. Surface doping with novel solution-processed metal-organic molecular species (n- and p-type) is demonstrated with an unprecedented range of work function modulation, resulting from electron transfer and the formation of molecular surface dipoles. However

  9. Fitness Doping and Body Management

    DEFF Research Database (Denmark)

    Thualagant, Nicole

    This PhD thesis examines in a first paper the conceptualization of fitness doping and its current limitations. Based on a review of studies on bodywork and fitness doping it is emphasised that the definition of doping does not provide insights into bodywork of both men and women. Moreover......, it is argued that the social and a cultural context are missing in the many epidemiological studies on the prevalence of doping. The second paper explores the difficulties of implementing an anti-doping policy, which was originally formulated in an elite sport context, in a fitness context and more...... specifically in a sport-for-all context. It is questioned whether the anti-doping policy contradicts some of the national sport-for-all organisation, DGI’s values of fostering fellowship, challenge and health. Last but not least, this thesis examines in a third paper the bodywork of the users’ of the club...

  10. CdS-based p-i-n diodes using indium and copper doped CdS films by pulsed laser deposition

    International Nuclear Information System (INIS)

    Hernandez-Como, N; Berrellez-Reyes, F; Mizquez-Corona, R; Ramirez-Esquivel, O; Mejia, I; Quevedo-Lopez, M

    2015-01-01

    In this work we report a method to dope cadmium sulfide (CdS) thin films using pulsed laser deposition. Doping is achieved during film growth at substrate temperatures of 100 °C by sequential deposition of the CdS and the dopant material. Indium sulfide and copper disulfide targets were used as the dopant sources for n-type and p-type doping, respectively. Film resistivities as low as 0.2 and 1 Ω cm were achieved for indium and copper doped films, respectively. Hall effect measurements demonstrated the change in conductivity type from n-type to p-type when the copper dopants are incorporated into the film. The controlled incorporation of indium or copper, in the undoped CdS film, results in substitutional defects in the CdS, which increases the electron and hole concentration up to 4 × 10 18 cm −3 and 3 × 10 20 cm −3 , respectively. The results observed with CdS doping can be expanded to other chalcogenides material compounds by just selecting different targets. With the optimized doped films, CdS-based p-i-n diodes were fabricated yielding an ideality factor of 4, a saturation current density of 2 × 10 −6 A cm −2 and a rectification ratio of three orders of magnitude at ±3 V. (paper)

  11. ERYTHROPOIETIN AS DOPING AGENT

    Directory of Open Access Journals (Sweden)

    Nina Đukanović

    2012-09-01

    Full Text Available Doping is the use of prohibited substances and/or methods that improve the abilities of athletes. Erythropoietin (EPO, the kidney hormone, belongs to a group of substances that are classified as blood doping, and it can be found on the list of banned substances from 1990. year. Its application leads to an increase in the number of red blood cells, which enables better supply of oxygen, and thus improve the aerobic performance of athletes. Because of that, EPO is very popular in sports where the endurance is predominantly required like a marathon, cycling, triathlon, nordic skiing. Erythropoietin can cause some adverse events, primarily to increase blood viscosity, which is associated with a higher risk of various thromboembolic complications. In detection of EPO use two groups of tests are available, through a urine sample (direct method and blood sample (indirect method.

  12. Doping and Public Health

    DEFF Research Database (Denmark)

    Christiansen, Ask Vest

    rad av världens främsta idrottsvetare och dopningsexperter hade mött upp för att presentera papers till en intresserad och engagerad publik. Temat för konferensen var "Doping and Public Health", och den aspekten behandlades också; dock tolkade flera presentatörer temat på sina egna vis, och hela...

  13. Doped Chiral Polymer Metamaterials Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Doped Chiral Polymer Metamaterials (DCPM) with tunable resonance frequencies have been developed by adding plasmonic inclusions into chiral polymers with variable...

  14. Qualitative and Semiquantitative Analysis of Doping Products Seized at the Swiss Border.

    Science.gov (United States)

    Weber, Christina; Krug, Oliver; Kamber, Matthias; Thevis, Mario

    2017-05-12

    Substances developed for therapeutic use are also known to be misused by athletes as doping agents and, outside of regulated sport, for image-enhancement. This has generated a market for counterfeit doping substances. Counterfeit doping agents may be of poor pharmaceutical quality and therefore constitute health risks to consumers. This study aims to investigate the pharmaceutical quality of 1,190 doping products seized at the Swiss border. Swiss customs authorities seize incoming shipments potentially containing doping agents. Qualitative and semiquantitative analyses were performed in order to test for prohibited doping substances. The main analytical methods utilized for characterizing confiscated compounds were liquid chromatography-high resolution mass spectrometry, polyacrylamide gel electrophoresis with subsequent in-gel tryptic digestion and identification of peptidic compounds using nanoliquid chromatography-tandem mass spectrometry, and electrochemiluminescence immuno assay. For 889 (75%) of the analyzed products, the label suggested the content of anabolic agents, for 146 samples (12%) peptide hormones or growth factors, and for 113 items (9%) antiestrogens, aromatase inhibitors or other metabolic modulators. For the majority of the investigated products, the pharmaceutical quality was an unsatisfactory standard: nonapproved substances were detected and less than 20% of the products contained the claimed substance in the respective amount. A comprehensive sample of confiscated doping products was analyzed, allowing for monitoring of developments regarding the use of doping substances in Switzerland and for anticipating future trends and challenges in sports drug testing. An alarming number of tested products was of substandard pharmaceutical quality.

  15. Decoupling the Lattice Distortion and Charge Doping Effects on the Phase Transition Behavior of VO2 by Titanium (Ti4+) Doping

    Science.gov (United States)

    Wu, Yanfei; Fan, Lele; Liu, Qinghua; Chen, Shi; Huang, Weifeng; Chen, Feihu; Liao, Guangming; Zou, Chongwen; Wu, Ziyu

    2015-01-01

    The mechanism for regulating the critical temperature (TC) of metal-insulator transition (MIT) in ions-doped VO2 systems is still a matter of debate, in particular, the unclear roles of lattice distortion and charge doping effects. To rule out the charge doping effect on the regulation of TC, we investigated Ti4+-doped VO2 (TixV1-xO2) system. It was observed that the TC of TixV1-xO2 samples first slightly decreased and then increased with increasing Ti concentration. X-ray absorption fine structure (XAFS) spectroscopy was used to explore the electronic states and local lattice structures around both Ti and V atoms in TixV1-xO2 samples. Our results revealed the local structure evolution from the initial anatase to the rutile-like structure around the Ti dopants. Furthermore, the host monoclinic VO2 lattice, specifically, the VO6 octahedra would be subtly distorted by Ti doping. The distortion of VO6 octahedra and the variation of TC showed almost the similar trend, confirming the direct effect of local structural perturbations on the phase transition behavior. By comparing other ion-doping systems, we point out that the charge doping is more effective than the lattice distortion in modulating the MIT behavior of VO2 materials. PMID:25950809

  16. Grain Size and Interface Dependence of Bias Stress Stability of n-Type Organic Field Effect Transistors.

    Science.gov (United States)

    Ahmed, Rizwan; Simbrunner, Clemens; Baig, M A; Sitter, H

    2015-10-14

    The effect of grain size and interface dependence of bias stress stability of C60-based n-type organic field effect transistors (OFETs) has been studied. It has been realized that, with increasing grain size of C60, the bias stress induced threshold voltage shift can be controlled and this effect is mainly attributed to the mechanism of charge trapping at grain boundaries. It is further studied that the growth of C60 on the surface of parylene at elevated substrate temperature leads to the creation of radicals at the interface between the active layer and the gate dielectric. These radicals help to improve the bias stress stability of C60-based n-type OFETs. For achieving the bias stress stability, we have presented a procedure of creation of radicals at the interface between C60 and parylene in single gate OFETs instead of dual gate OFETs.

  17. Correlation between the electron-phonon coupling and rectifying performance for poly(3-hexylthiophene)/n-type Si devices

    International Nuclear Information System (INIS)

    Lin, Yow-Jon; Chin, Yi-Min

    2014-01-01

    A correlation between the electron-phonon coupling and rectifying performance is identified for poly(3-hexylthiophene) (P3HT)/n-type Si devices and an analysis using the temperature-dependent Hall-effect characteristics is presented. The carrier mobility in the P3HT film exhibits strong temperature dependence, indicating the dominance of tunneling. However, the incorporation of titanium oxide (TiO 2 ) nanoparticles into P3HT leads to the dominance of hopping. The results demonstrate that the incorporation of TiO 2 nanoparticles into P3HT influences the electrical property of P3HT/n-type Si devices by the electron-phonon coupling modification and the increased spacing between molecules that serve to enhance the carrier mobility in P3HT

  18. High efficiency heterojunction solar cells on n-type kerfless mono crystalline silicon wafers by epitaxial growth

    Science.gov (United States)

    Kobayashi, Eiji; Watabe, Yoshimi; Hao, Ruiying; Ravi, T. S.

    2015-06-01

    We present a heterojunction (HJ) solar cell on n-type epitaxially grown kerfless crystalline-silicon (c-Si) with a conversion efficiency of 22.5%. The total cell area is 243.4 cm2. The cell has a short-circuit current density of 38.6 mA/cm2, an open-circuit voltage of 735 mV, and a fill factor of 0.791. The key advantages and technological tasks of epitaxial wafers for HJ solar cells are discussed, in comparison with conventional n-type Czockralski c-Si wafers. The combination of HJ and kerfless technology can lead to high conversion efficiency with a potential at low cost.

  19. Fluorinated copper-phthalocyanine-based n-type organic field-effect transistors with a polycarbonate gate insulator

    Energy Technology Data Exchange (ETDEWEB)

    Sethuraman, Kunjithapatham [Madurai Kamaraj University, Madurai (India); Kumar, Palanisamy; Santhakumar, Kannappan; Ochiai, Shizuyasu [Aichi Institute of Technology, Toyota City (Japan); Shin, Paikkyun [Inha University, Incheon (Korea, Republic of)

    2012-07-15

    Fluorinated copper-phthalocyanine (F{sub 16}CuPc) thin films were prepared by using a vacuum evaporation technique and were applied to n-type organic field-effect transistors (OFETs) as active channel layers combined with a spin-coated polycarbonate thin-film gate insulator. The output characteristics of the resulting n-type OFET devices with bottom-gate/bottom-contact structures were investigated to evaluate the performances such as the field effect mobility (μ{sub FE}), the on/off current ratio (I{sub on/off}), and the threshold voltage (V{sub th}). A relatively high field effect mobility of 6.0 x 10{sup -3} cm{sup 2}/Vs was obtained for the n-type semiconductor under atmospheric conditions with an on/off current ratio of 1 x 10{sup 4} and a threshold voltage of 5 V. The electron mobility of the n-type semiconductor was found to depend strongly on the growth temperature of the F{sub 16}CuPc thin films. X-ray diffraction profiles showed that the crystallinity and the orientation of the F{sub 16}CuPc on a polycarbonate thin film were enhanced with increasing growth temperature. Atomic force microscopy studies revealed various surface morphologies of the active layer. The field effect mobility of the F{sub 16}CuPc-OFET was closely related to the crystallinity and the orientation of the F{sub 16}CuPc thin film.

  20. Huwentoxin-XVI, an analgesic, highly reversible mammalian N-type calcium channel antagonist from Chinese tarantula Ornithoctonus huwena.

    Science.gov (United States)

    Deng, Meichun; Luo, Xuan; Xiao, Yucheng; Sun, Zhenghua; Jiang, Liping; Liu, Zhonghua; Zeng, Xiongzhi; Chen, Hanchun; Tang, Jianhua; Zeng, Weimin; Songping Liang

    2014-04-01

    N-type calcium channels play important roles in the control of neurotransmission release and transmission of pain signals to the central nervous system. Their selective inhibitors are believed to be potential drugs for treating chronic pain. In this study, a novel neurotoxin named Huwentoxin-XVI (HWTX-XVI) specific for N-type calcium channels was purified and characterized from the venom of Chinese tarantula Ornithoctonus huwena. HWTX-XVI is composed of 39 amino acid residues including six cysteines that constitute three disulfide bridges. HWTX-XVI could almost completely block the twitch response of rat vas deferens to low-frequency electrical stimulation. Electrophysiological assay indicated that HWTX-XVI specifically inhibited N-type calcium channels in rat dorsal root ganglion cells (IC50 ∼60 nM). The inhibitory effect of HWTX-XVI on N-type calcium channel currents was dose-dependent and similar to that of CTx-GVIA and CTx-MVIIA. However, the three peptides exhibited markedly different degrees of reversibility after block. The toxin had no effect on voltage-gated T-type calcium channels, potassium channels or sodium channels. Intraperitoneal injection of the toxin HWTX-XVI to rats elicited significant analgesic responses to formalin-induced inflammation pain. Toxin treatment also changed withdrawal latency in hot plate tests. Intriguingly, we found that intramuscular injection of the toxin reduced mechanical allodynia induced by incisional injury in Von Frey test. Thus, our findings suggest that the analgesic potency of HWTX-XVI and its greater reversibility could contribute to the design of a novel potential analgesic agent with high potency and low side effects. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. N-type thermoelectric recycled carbon fibre sheet with electrochemically deposited Bi{sub 2}Te{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Pang, E.J.X. [Division of Materials, Mechanics and Structures, The University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Pickering, S.J., E-mail: stephen.pickering@nottingham.ac.uk [Division of Materials, Mechanics and Structures, The University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Chan, A. [Division of Materials, Mechanics and Structures, The University of Nottingham Malaysia Campus, Jalan Broga, 43500 Semenyih, Selangor Darul Ehsan (Malaysia); Wong, K.H. [Division of Materials, Mechanics and Structures, The University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Lau, P.L. [Division of Materials, Mechanics and Structures, The University of Nottingham Malaysia Campus, Jalan Broga, 43500 Semenyih, Selangor Darul Ehsan (Malaysia)

    2012-09-15

    An N-type thermoelectric recycled carbon fibre sheet with bismuth telluride coating has been successfully synthesised through an electro-deposition technique. The Seebeck coefficient and electrical properties of the combined recycled carbon fibre sheet and bismuth telluride films are reported. Classification of the crystal structure, surface morphology and the elemental composition of the resulting deposits are methodically characterised by XRD, SEM and EDX. Cyclic voltammetry is also carried out in nitric acid solutions to investigate the right range of deposition potential. The synthesis N-type thermoelectric sheet has a highest attainable Seebeck coefficient of -54 {mu}V K{sup -1} and an electrical resistivity of 8.9 Multiplication-Sign 10{sup -5} Ohm-Sign m. The results show slight differences in morphologies and thermoelectric properties for the films deposited at varying deposition potential. The increase in thermoelectrical properties of the recycled carbon fibre is in line with the development of using coated recycled fibre for thermoelectrical applications. - Graphical abstract: SEM image of an N-type thermoelectric recycled carbon fibre sheet with Bi{sub 2}Te{sub 3} coatings. Highlights: Black-Right-Pointing-Pointer N-type thermoelectric sheet is synthesis through the electrodeposition of Bi{sub 2}Te{sub 3}. Black-Right-Pointing-Pointer Bi{sub 2}Te{sub 3} composition can be controlled by varying the deposition voltage. Black-Right-Pointing-Pointer Seebeck coefficient and electrical properties of the combined sheet were reported. Black-Right-Pointing-Pointer Material characterisations of the deposits are done using XRD, SEM and EDX.

  2. Nonlinear Elasticity of Doped Semiconductors

    Science.gov (United States)

    2017-02-01

    AFRL-RY-WP-TR-2016-0206 NONLINEAR ELASTICITY OF DOPED SEMICONDUCTORS Mark Dykman and Kirill Moskovtsev Michigan State University...2016 4. TITLE AND SUBTITLE NONLINEAR ELASTICITY OF DOPED SEMICONDUCTORS 5a. CONTRACT NUMBER FA8650-16-1-7600 5b. GRANT NUMBER 5c. PROGRAM...vibration amplitude. 15. SUBJECT TERMS semiconductors , microresonators, microelectromechanical 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

  3. Electrostatic Doping in Semiconductor Devices

    NARCIS (Netherlands)

    Gupta, Gaurav; Rajasekharan, Bijoy; Hueting, Raymond J.E.

    2017-01-01

    To overcome the limitations of chemical doping in nanometer-scale semiconductor devices, electrostatic doping (ED) is emerging as a broadly investigated alternative to provide regions with a high electron or hole density in a semiconductor device. In this paper, we review various reported ED

  4. The effect of cadmium doping of Pbsub(1-x)Snsub(x)Te crystals and thin layers on the electrical properties of the system

    International Nuclear Information System (INIS)

    Silberg, E.

    1982-06-01

    In the present work the doping characteristics and electrical properties of Cd-doped bulk crystals (as-grown and annealed) and LPE layers of Pbsub(1-x)Snsub(x)Te, 0<=x<=0.25, were studied using Hall effect, resistivity and Cd-solubility measurements. The bulk crystals were doped by Cd-diffusion in a two-temperature-zone furnace and the LPE layers by adding Cd to the growth solution. Cd doping was used to produce uniform n-type LPE layers of Pbsub(1-x)Snsub(x)Te and the process proved to be a controllable and reproducible method for the production of good quality material with low electron concentration and high electron mobility. These qualities are very important in obtaining improved electrooptical devices. (H.K.)

  5. Doped beryllium lanthanate crystals

    International Nuclear Information System (INIS)

    1974-01-01

    Monocrystals of doped beryllium lanthanate, Be 2 Lasub(2-2x)Zsub(2x)O 5 --where Z may be any rare earth, but preferably neodymium, and x may have values between 0.001 and 0.2, but preferably between 0.007 and 0.015-- are recommended as laser hosts. They are softer and may be grown at a lower temperature than Y 3 A1 5 O 12 :Nd (YAG:Nd). Their chemical composition and preparation are described. An example of an optically pumped laser apparatus with this type of monocrystal as laser host is presented

  6. Detection of SARMs in doping control analysis.

    Science.gov (United States)

    Thevis, Mario; Schänzer, Wilhelm

    2018-03-15

    The class of selective androgen receptor modulators (SARMs) has been the subject of intense and dedicated clinical research over the past two decades. Potential therapeutic applications of SARMs are manifold and focus particularly on the treatment of conditions manifesting in muscle loss such as general sarcopenia, cancer-associated cachexia, muscular dystrophy, etc. Consequently, based on the substantial muscle- and bone-anabolic properties of SARMs, these agents constitute substances with significant potential for misuse in sport and have therefore been added to the Word Anti-Doping Agency's (WADA's) Prohibited List in 2008. Since then, numerous adverse analytical findings have been reported for various different SARMs, which has underlined the importance of proactive and preventive anti-doping measures concerning emerging drugs such as these anabolic agents, which have evidently been misused in sport despite the fact that none of these SARMs has yet received full clinical approval. In this review, analytical data on SARMs generated in the context of research conducted for sports drug testing purposes are summarized and state-of-the-art test methods aiming at intact drugs as well as diagnostic urinary metabolites are discussed. Doping control analytical approaches predominantly rely on chromatography hyphenated to mass spectrometry, which have allowed for appropriately covering the considerable variety of pharmacophores present in SARMs such as the non-steroidal representatives ACP-105, BMS-564929, GLPG0492 (DT-200), LG-121071, LGD-2226, LGD-4033/VK 5211, ostarine/enobosarm, RAD-140, S-40503, etc. as well as steroidal compounds such as MK-0773 and YK-11. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Mode-locked Tm-doped fiber laser based on iron-doped carbon nitride nanosheets

    Science.gov (United States)

    Luo, Yongfeng; Zhou, Yan; Tang, Yulong; Xu, Jianqiu; Hu, Chenxia; Gao, Linfeng; Zhang, Haoli; Wang, Qiang

    2017-11-01

    Solution based nanosheets of iron-doped graphitic carbon nitrides (Fe-g-CN) have been prepared and their optical properties (both linear and nonlinear) are studied. These two-dimensional (2D) nanosheets show an absorption spectrum extending to over 2 µm, and in particular they possess strong nonlinear (saturable) absorption in the 2 µm spectral region. A saturable absorber (SA) manufactured from 2D Fe-g-CN nanosheets gives a modulation depth and saturation intensity of 12.9% and 8.9 MW cm‑2, respectively. This SA is further used to mode-lock thulium-doped fiber lasers, producing 2 µm laser pulses with a duration of 16.6 ps (dechirped to 2.2 ps), an average power of 96.4 mW, a pulse energy of 6.3 nJ, and a repetition rate of 15.3 MHz. As a new type of 2D nonlinear material with strong modulation capabilities, solution-based Fe-g-CN nanosheets can be potentially integrated into photonic and optoelectrionic devices, particuarly in the 2 µm spectral region.

  8. High precision trace neutron transmutation doping of detector-grade high resistance zone-refined silicon mono-crystal

    International Nuclear Information System (INIS)

    Chen Bingxian; Gao Jijin; Gao Xiuqing; Dong Heqin; Li Shiling

    1993-08-01

    The technique of high precision trace neutron transmutation doping of detector grade high resistance zone-refined Si mono-crystal is introduced. The key technique is to precisely control the doping element. It includes the determination of ρ 0 value according to theoretical calculation and experimental results, the selection of irradiation channel and improvement of irradiation devices, the regulation of doping coefficient K, the simulation experiment of silicon crystal, strict control of irradiation time and the study on mechanism of radiation damage and its elimination. The developed N-type (10 ∼ 100) kΩcm NTD FZ Si has excellent uniformity of specific resistance, long life of minority carrier and high-purity of the crystal

  9. Characterization of patterns of Localized Doping Using Stamping technique for Selective n-Emitter Solar Cell Structure

    Science.gov (United States)

    Mangkornkaew, A.; Fangsuwannarak, T.

    2017-10-01

    In the present, a novel cost-effective process scheme for single step selective emitter diffusion was implemented. It is based on the fabrication of acid-resist pattern using a stamping technique with collaboration of a spin on dopant (SOD) and chemical etched-back emitter methods. The SOD diffusion process provided heavily doping n-emitter. Acid-resist pattern without exploitation of a complex method as a photolithography, was stamped as a metal contact pattern for prevention of a localized heavy-dope region from etching back. Phosphorus doping profiles were controlled by etching back time to provide the formation of n-type selective emitter. Sheet resistance is tunable from 10 to 180 Ohm/Sq on localized n-layer. After removal of the patterned acid-resist, the selective n-emitter solar cell structure was obtained under one-step diffusion to achieve a better blue-light response and low contact resistance.

  10. Improved Electron Transport with Reduced Contact Resistance in N-Doped Polymer Field-Effect Transistors with a Dimeric Dopant.

    Science.gov (United States)

    Wang, Rong; Guo, Yikun; Zhang, Di; Zhou, Huiqiong; Zhao, Dahui; Zhang, Yuan

    2018-01-15

    Attaining control on charge injection properties is significant for meaningful applications of organic field-effect transistors (OFETs). Here, molecular electron-doping is applied with an air-stable dimer dopant for n-type OFETs based on (naphthalene diimide-diketopyrrolopyrrole) polymer hosts. Through investigating the doping effect on contact and transport properties, it is found that the electron transport increases in n-doped OFETs at low doping regime with remaining large on/off ratios. These favorable meliorations are reconciled by the mitigated impacts of contact resistance and interfacial traps, as well as the surface morphology exhibiting features of increased ordering. The occurrence of doping in the presence of dimer dopants is evidenced by the observed shift of Fermi level toward vacuum level coupled with compositional analysis. Without applying vacuum-deposition-based contact doping, charge injection efficiencies are gained without losing OFET characteristics using the solution-based methodology. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. The structural, electronic and optical properties of Nd doped ZnO using first-principles calculations

    Science.gov (United States)

    Wen, Jun-Qing; Zhang, Jian-Min; Chen, Guo-Xiang; Wu, Hua; Yang, Xu

    2018-04-01

    The density functional theory calculations using general gradient approximation (GGA) applying Perdew-Burke-Ernzerhof (PBE) as correlation functional have been systematically performed to research the formation energy, the electronic structures, band structures, total and partial DOS, and optical properties of Nd doping ZnO with the content from 6.25% to 12.5%. The formation energies are negative for both models, which show that two structures are energetically stable. Nd doping ZnO crystal is found to be a direct band gap semiconductor and Fermi level shifts upward into conduction band, which show the properties of n-type semiconductor. Band structures are more compact after Nd doping ZnO, implying that Nd doping induces the strong interaction between different atoms. Nd doping ZnO crystal presents occupied states at near Fermi level, which mainly comes from the Nd 4f orbital. The calculated optical properties imply that Nd doping causes a red-shift of absorption peaks, and enhances the absorption of the visible light.

  12. Transmission electron microscopy and electrical properties measurements of laser doped silicon and GaAs

    International Nuclear Information System (INIS)

    Young, R.T.; Narayan, J.; Westbrook, R.D.; Wood, R.F.

    1978-12-01

    High quality silicon p-n junctions have been prepared by alloying a vacuum evaporated Al film into n-type Si and by epitaxial regrowth of an As doped Si amorphous layer onto p-type (100) Si by a single short pulse of ruby laser radiation. Transmission electron microscopy investigations indicated that a defect-free epitaxial layer was grown on the (100) Si surface; however, some polycrystalline structure in the very near-surface region was observed, which does not seem to affect the junction characteristics. Laser assisted junction formation in GaAs was demonstrated by alloying Mg films into n-type GaAs; however, diode characteristics show a large leakage current which may have been caused by the surface damage

  13. Doped semiconductor nanocrystal junctions

    Energy Technology Data Exchange (ETDEWEB)

    Borowik, Ł.; Mélin, T., E-mail: thierry.melin@isen.iemn.univ-lille1.fr [Institut d’Electronique, de Microélectronique et de Nanotechnologie, CNRS-UMR8520, Avenue Poincaré, F-59652 Villeneuve d’Ascq (France); Nguyen-Tran, T.; Roca i Cabarrocas, P. [Laboratoire de Physique des Interfaces et des Couches Minces, CNRS-UMR7647, Ecole Polytechnique, F-91128 Palaiseau (France)

    2013-11-28

    Semiconductor junctions are the basis of electronic and photovoltaic devices. Here, we investigate junctions formed from highly doped (N{sub D}≈10{sup 20}−10{sup 21}cm{sup −3}) silicon nanocrystals (NCs) in the 2–50 nm size range, using Kelvin probe force microscopy experiments with single charge sensitivity. We show that the charge transfer from doped NCs towards a two-dimensional layer experimentally follows a simple phenomenological law, corresponding to formation of an interface dipole linearly increasing with the NC diameter. This feature leads to analytically predictable junction properties down to quantum size regimes: NC depletion width independent of the NC size and varying as N{sub D}{sup −1/3}, and depleted charge linearly increasing with the NC diameter and varying as N{sub D}{sup 1/3}. We thus establish a “nanocrystal counterpart” of conventional semiconductor planar junctions, here however valid in regimes of strong electrostatic and quantum confinements.

  14. Passively Q-switched and mode-locked Nd:GGG laser with a Bi-doped GaAs saturable absorber.

    Science.gov (United States)

    Cong, Wen; Li, Dechun; Zhao, Shengzhi; Yang, Kejian; Li, Xiangyang; Qiao, Hui; Liu, Ji

    2014-06-16

    A simultaneously passively Q-switched and mode-locked (QML) Nd:GGG laser using a Bi-doped GaAs wafer as saturable absorber is accomplished for the first time. The Bi-doped GaAs wafer is fabricated by ion implantation and subsequent annealing. In comparison to the passively QML laser with GaAs, the QML laser with Bi-doped GaAs can generate more stable pulses with 99% modulation depth. The experiment results indicate that the Bi-doped GaAs could be an excellent saturable absorber for diode-pumped QML lasers.

  15. Origin of the n -type and p -type conductivity of MoS 2 monolayers on a SiO 2 substrate

    KAUST Repository

    Dolui, Kapildeb

    2013-04-02

    Ab initio density functional theory calculations are performed to study the electronic properties of a MoS2 monolayer deposited over a SiO 2 substrate in the presence of interface impurities and defects. When MoS2 is placed on a defect-free substrate, the oxide plays an insignificant role since the conduction band top and the valence band minimum of MoS2 are located approximately in the middle of the SiO2 band gap. However, if Na impurities and O dangling bonds are introduced at the SiO2 surface, these lead to localized states, which modulate the conductivity of the MoS2 monolayer from n- to p-type. Our results show that the conductive properties of MoS2 deposited on SiO 2 are mainly determined by the detailed structure of the MoS 2/SiO2 interface, and suggest that doping the substrate can represent a viable strategy for engineering MoS2-based devices. © 2013 American Physical Society.

  16. Resolution characteristics for reflection-mode exponential-doping GaN photocathode.

    Science.gov (United States)

    Wang, Honggang; Qian, Yunsheng; Du, Yujie; Xu, Yuan; Lu, Liubing; Chang, Benkang

    2014-01-20

    According to the expression for modulation transfer function obtained by solving the established 2D continuity equation, the resolution characteristics for reflection-mode exponential-doping and uniform-doping GaN photocathodes have been calculated and comparatively analyzed. These calculated results show that the exponential-doping structure can upgrade not only the resolution capability but also the quantum efficiency for a GaN photocathode. The improvement mechanism is different from the approach for high resolution applied by reducing Te and L(D) or increasing S(V), which leads to low quantum efficiency. The main contribution factor of this improvement is that the mechanism that transports electrons toward the NEA surface is facilitated by the built-in electric field formed by this exponential-doping structure, and the corresponding lateral diffusion is reduced.

  17. Improving Luttinger-liquid plasmons in carbon nanotubes by chemical doping.

    Science.gov (United States)

    Tian, Xiaoling; Gu, Qingyuan; Duan, Jiahua; Chen, Runkun; Liu, Huaping; Hou, Yanxue; Chen, Jianing

    2018-04-05

    We realized the real-space imaging of Luttinger-liquid plasmons in semiconducting single-walled carbon nanotubes (s-SWCNTs) and studied the effects of chemical-doping-induced charge carrier density modulation on plasmons. Using scattering-type scanning near-field optical microscopy (s-SNOM), we compared the Luttinger-liquid plasmonic behavior in pre- and post-HNO3-doped SWCNTs. Raman measurements revealed that the physical mechanism is P-type doping. Through HNO3 doping, we effectively increased the charge carrier density in s-SWCNTs and achieved quantum plasmons simultaneously with strong confinement (λ0/λp ≈ 70) and high quality factor (Q ≈ 20). The combination of high quality factor and strong subwavelength confinement in Luttinger-liquid plasmons is critical to the future application of plasmonic devices.

  18. Research Update: Doping ZnO and TiO2 for solar cells

    Directory of Open Access Journals (Sweden)

    Robert L. Z. Hoye

    2013-12-01

    Full Text Available ZnO and TiO2 are two of the most commonly used n-type metal oxide semiconductors in new generation solar cells due to their abundance, low-cost, and stability. ZnO and TiO2 can be used as active layers, photoanodes, buffer layers, transparent conducting oxides, hole-blocking layers, and intermediate layers. Doping is essential to tailor the materials properties for each application. The dopants used and their impact in solar cells are reviewed. In addition, the advantages, disadvantages, and commercial potential of the various fabrication methods of these oxides are presented.

  19. Stable respiratory activity requires both P/Q-type and N-type voltage-gated calcium channels.

    Science.gov (United States)

    Koch, Henner; Zanella, Sebastien; Elsen, Gina E; Smith, Lincoln; Doi, Atsushi; Garcia, Alfredo J; Wei, Aguan D; Xun, Randy; Kirsch, Sarah; Gomez, Christopher M; Hevner, Robert F; Ramirez, Jan-Marino

    2013-02-20

    P/Q-type voltage-gated calcium channels (Ca(v)2.1) play critical presynaptic and postsynaptic roles throughout the nervous system and have been implicated in a variety of neurological disorders. Here we report that mice with a genetic ablation of the Ca(v)2.1 pore-forming α(1A) subunit (α(1A)⁻/⁻) encoded by CACNA1a (Jun et al., 1999) suffer during postnatal development from increasing breathing disturbances that lead ultimately to death. Breathing abnormalities include decreased minute ventilation and a specific loss of sighs, which was associated with lung atelectasis. Similar respiratory alterations were preserved in the isolated in vitro brainstem slice preparation containing the pre-Bötzinger complex. The loss of Ca(v)2.1 was associated with an alteration in the functional dependency on N-type calcium channels (Ca(v)2.2). Blocking N-type calcium channels with conotoxin GVIA had only minor effects on respiratory activity in slices from control (CT) littermates, but abolished respiratory activity in all slices from α(1A)⁻/⁻ mice. The amplitude of evoked EPSPs was smaller in inspiratory neurons from α(1A)⁻/⁻ mice compared with CTs. Conotoxin GVIA abolished all EPSPs in inspiratory neurons from α(1A)⁻/⁻ mice, while the EPSP amplitude was reduced by only 30% in CT mice. Moreover, neuromodulation was significantly altered as muscarine abolished respiratory network activity in α(1A)⁻/⁻ mice but not in CT mice. We conclude that excitatory synaptic transmission dependent on N-type and P/Q-type calcium channels is required for stable breathing and sighing. In the absence of P/Q-type calcium channels, breathing, sighing, and neuromodulation are severely compromised, leading to early mortality.

  20. The Ethics of Doping and Anti-Doping

    DEFF Research Database (Denmark)

    Møller, Verner

    With every positive drugs test the credibility and veracity of modern elite sport is diminished. In this radical and provocative critique of current anti-doping policy and practice, Verner Møller argues that the fight against doping – promoted as an initiative to cleanse sport of cheats – is at h......With every positive drugs test the credibility and veracity of modern elite sport is diminished. In this radical and provocative critique of current anti-doping policy and practice, Verner Møller argues that the fight against doping – promoted as an initiative to cleanse sport of cheats....... It is important reading for all serious students and scholars of the ethics, sociology and politics of sport....

  1. Noticeable positive Doppler effect on optical bistability in an N-type active Raman gain atomic system

    International Nuclear Information System (INIS)

    Chang Zeng-Guang; Zhang Jing-Tao; Niu Yue-Ping; Gong Shang-Qing

    2012-01-01

    We theoretically investigate the Doppler effect on optical bistability in an N-type active Raman gain atomic system inside an optical ring cavity. It is shown that the Doppler effect can greatly enhance the dispersion and thus create the bistable behaviour or greatly increase the bistable region, which has been known as the positive Doppler effect on optical bistability. In addition, we find that a positive Doppler effect can change optical bistability from the hybrid dispersion-gain type to a dispersive type

  2. Unconventional Face-On Texture and Exceptional In-Plane Order of a High Mobility n-Type Polymer

    KAUST Repository

    Rivnay, Jonathan

    2010-07-09

    Substantial in-plane crystallinity and dominant face-on stacking are observed in thin films of a high-mobility n-type rylene-thiophene copolymer. Spun films of the polymer, previously thought to have little or no order are found to exhibit an ordered microstructure at both interfaces, and in the bulk. The implications of this type of packing and crystalline morphology are discussed as they relate to thin-film transistors. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Germanium doping of GaN by metalorganic chemical vapor deposition for polarization screening applications

    KAUST Repository

    Young, N.G.

    2016-10-01

    We demonstrate n-type doping of GaN with Ge by MOCVD at high concentrations that are necessary to fully screen the polarization fields in c-plane InGaN/GaN quantum wells. Hall measurements show linear Ge incorporation with dopant flow rate and carrier concentrations exceeding 1×10 cm. GaN:Ge layers exhibit excellent electron mobility, high conductivity, and contact resistivity comparable to the best unannealed contacts to Si-doped GaN. However, the surface morphology begins to degrade with Ge concentrations above 1×10 cm, resulting in severe step bunching and a network of plateaus and trenches, even in layers as thin as 10 nm.

  4. Effects of aluminium doping on zinc oxide transparent thin films grown by filtered vacuum arc deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gontijo, L.C., E-mail: pleooog@gmail.com [Instituto Federal do Espirito Santo, Programa de Pos-Graduacao em Engenharia Metalurgica e de Materiais, Av. Vitoria, 1729, Jucutuquara, 29040-780, Vitoria, ES (Brazil); Machado, R., E-mail: rogerio.machado.2l@gmail.com [Universidade Federal de Sergipe, Departamento de Fisica, Rod. Mal Rondon S/N, Jd Rosa Elze, CEP 49.100-000, Sao Cristovao, SE (Brazil); Nascimento, V.P., E-mail: valberpn@yahoo.com.br [Universidade Federal do Espirito Santo, Departamento de Fisica, Av. Fernando Ferrari, 514 Goiabeiras, CEP 29075-910, Vitoria, ES (Brazil)

    2012-06-25

    Highlights: Black-Right-Pointing-Pointer AZO films prepared by filtered vacuum arc deposition. Black-Right-Pointing-Pointer Systematic variation of Al concentration. Black-Right-Pointing-Pointer Structural, electrical and optical properties analyzed. Black-Right-Pointing-Pointer Optimized system for Al concentration between 4% and 6%. - Abstract: Thin n-type ZnO films doped with different atomic concentrations of aluminium were grown by filtered vacuum arc deposition (FVAD) on glass substrates. The films were deposited using an oxygen working pressure of 2.0 mTorr with an arc current running at two 100 ms pulses s{sup -1}. Structural, optical and electrical properties were investigated to understand the effect of Al doping on ZnO films. The best values were found for an ideal aluminium percentage between 4 and 6 at.%.

  5. Defect reaction network in Si-doped InAs. Numerical predictions.

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, Peter A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-05-01

    This Report characterizes the defects in the def ect reaction network in silicon - doped, n - type InAs predicted with first principles density functional theory. The reaction network is deduced by following exothermic defect reactions starting with the initially mobile interstitial defects reacting with common displacement damage defects in Si - doped InAs , until culminating in immobile reaction p roducts. The defect reactions and reaction energies are tabulated, along with the properties of all the silicon - related defects in the reaction network. This Report serves to extend the results for the properties of intrinsic defects in bulk InAs as colla ted in SAND 2013 - 2477 : Simple intrinsic defects in InAs : Numerical predictions to include Si - containing simple defects likely to be present in a radiation - induced defect reaction sequence . This page intentionally left blank

  6. Infrared absorption and visible transparency in heavily doped p-type BaSnO3

    Science.gov (United States)

    Li, Yuwei; Sun, Jifeng; Singh, David J.

    2017-01-01

    The recent experimental work shows that perovskite BaSnO3 can be heavily doped by K to become a stable p-type semiconductor. Here, we find that p-type perovskite BaSnO3 retains transparency for visible light while absorbing strongly in the infrared below 1.5 eV. The origin of the remarkable optical transparency even with heavy doping is that the interband transitions that are enabled by empty states at the top of the valence band are concentrated mainly in the energy range from 0.5 to 1.5 eV, i.e., not extending past the near IR. In contrast to n-type, the Burstein-Moss shift is slightly negative, but very small reflecting the heavier valence bands relative to the conduction bands.

  7. Understanding the Room Temperature Ferromagnetism in GaN Nanowires with Pd Doping

    Energy Technology Data Exchange (ETDEWEB)

    Manna, S; De, S K, E-mail: mannaju@gmail [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India)

    2011-04-01

    We report the first synthesis and characterization of 4d transition metal palladium-doped GaN nanowires (NWs). Room temperature ferromagnetism has been observed in high quality Vapor Liquid Solid (VLS) epitaxy grown undoped n-type GaN nanowires. It was proposed that this type of magnetism is due to defects which are not observed in Bulk GaN because of large formation energy of defects in bulk GaN. Here we have successfully doped 4d transition metal Pd in GaN NWs. We find fairly strong and long-range ferromagnetic coupling between Pd substituted for Ga in GaN . The results suggest that 4d metals such as Pd may also be considered as candidates for ferromagnetic dopants in semiconductors.

  8. Electrical characterisation of Sn doped InAs grown by MOVPE

    Energy Technology Data Exchange (ETDEWEB)

    Shamba, P.; Botha, L.; Krug, T.; Venter, A.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth (South Africa)

    2008-07-01

    The feasibility of tetraethyl tin (TESn) as an n-type dopant for InAs is investigated. The electrical properties of Sn doped InAs films grown on semi-insulating GaAs substrates by MOVPE are extensively studied as a function of substrate temperature, V/III ratio, substrate orientation and TESn flow rate. Results from this study show that Sn concentrations can be controlled over 2 orders of magnitude. The Sn doped InAs layers exhibit carrier concentrations between 2.7 x 10{sup 17} and 4.7 x 10{sup 19} cm{sup -3} with 77 K mobilities ranging from 12 000 to 1300 cm{sup 2}/Vs. Furthermore, the influence of the variation of these parameters on the structural properties of InAs are also reported. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Elaboration and Characterization of Sprayed Tb-Doped ZnO Thin Films

    Directory of Open Access Journals (Sweden)

    Amina ELFAKIR

    2014-05-01

    Full Text Available ZnO and Tb-doped ZnO (TZO thin films were deposited on glass substrate at 350 °C by spray pyrolysis technique. Structural, optical and electrical properties of the films were investigated as a function of dopant concentration, which was varied between 0 and 5 at % of terbium. TZO films were polycrystalline and exhibit hexagonal quartzite crystal structure with a preferential orientation along 2 direction. The AFM measurements show that the roughness of the films increased with Tb doping. All the TZO films exhibit a transmittance between 70 and 80 % in the visible range. The TZO films were n-type degenerate semiconductor with a lowest electrical resistivity of about 6.0´10- 2 W.cm.

  10. Influence of the doping on the lattice sites of Fe in Si

    CERN Document Server

    Silva, Daniel; Wahl, Ulrich; Martins Correia, Joao; Esteves De Araujo, Araujo Joao Pedro

    2014-01-01

    We report on the lattice location and thermal stability of Fe in n+- and p+-type silicon. By means of emission channeling we have observed Fe on ideal substitutional sites, sites located in between bond-centered (BC) and substitutional sites, and sites displaced from tetrahedral towards anti-bonding sites. Here, we focus our analysis on the identification of Fe displaced 0.4-0.6 Å from BC sites and the influence of the doping on the stability of these sites. Fe on near-BC sites is found to be more thermally stable in n+-type Si than in low doped or p+-type Si, and seems to be related to multiple vacancy defects. We suggest that the complexes which trap Fe near BC sites, as well as the formation of substitutional Fe, may play a crucial role in P-diffusion gettering.

  11. Impurity-related nonlinear optical properties in delta-doped quantum rings: Electric field effects

    International Nuclear Information System (INIS)

    Restrepo, R.L.; Morales, A.L.; Martínez-Orozco, J.C.; Baghramyan, H.M.; Barseghyan, M.G.; Mora-Ramos, M.E.; Duque, C.A.

    2014-01-01

    Using a variational procedure within the effective mass approximation, we have calculated the donor impurity binding energy for the ground (1s-like) and the excited (2p z -like) states as well as the impurity-related nonlinear optical absorption and relative changes in the refraction index in a GaAs single quantum ring with axial n-type delta-doping. The delta-like potential along the z-direction is an approximate model analytically described using a Lorentzian function with two parameters. Additionally we consider the application of an electric field along the z-direction. It is found that the changes in the geometry of the quantum ring, the change in the 2D impurity density of the delta-like doping, and different values of the electric field lead to a shifting of the resonant peaks of the optical responses spectrum

  12. Phosphorus Doped Zn 1- x Mg x O Nanowire Arrays

    KAUST Repository

    Lin, S. S.

    2009-11-11

    We demonstrate the growth of phosphorus doped Zn 1-xMg xO nanowire (NW) using pulsed laser deposition. For the first time, p-type Zn 0.92Mg 0.08O:P NWs are likely obtained In reference to atomic force microscopy based piezoelectric output measurements, X-ray photoelectron spectroscopy, and the transport property between the NWs and a n-type ZnO film. A shallow acceptor level of ∼140 meV Is identified by temperaturedependent photoluminescence. A piezoelectric output of 60 mV on average has been received using the doped NWs. Besides a control on NW aspect ratio and density, band gap engineering has also been achieved by alloying with Mg to a content of x = 0.23. The alloyed NWs with controllable conductivity type have potential application In high-efficiency all-ZnO NWs based LED, high-output ZnO nanogenerator, and other optical or electrical devices. © 2009 American Chemical Society.

  13. The novel N-type calcium channel blocker, AM336, produces potent dose-dependent antinociception after intrathecal dosing in rats and inhibits substance P release in rat spinal cord slices.

    Science.gov (United States)

    Smith, Maree T; Cabot, Peter J; Ross, Fraser B; Robertson, Alan D; Lewis, Richard J

    2002-03-01

    N-type calcium channels modulate the release of key pro-nociceptive neurotransmitters such as glutamate and substance P (SP) in the central nervous system. Considerable research interest has focused on the therapeutic potential of the peptidic omega-conopeptides, GVIA and MVIIA as novel analgesic agents, due to their potent inhibition of N-type calcium channels. Recently, the novel peptidic N-type calcium channel blocker, AM336, was isolated from the venom of the cone snail, Conus catus. Thus, the aims of this study were to (i) document the antinociceptive effects of AM336 (also known as CVID) relative to MVIIA following intrathecal (i.t.) bolus dosing in rats with adjuvant-induced chronic inflammatory pain of the right hindpaw and to (ii) quantify the inhibitory effects of AM336 relative to MVIIA on K+-evoked SP release from slices of rat spinal cord. Both AM336 and MVIIA inhibited the K+-evoked release of the pro-nociceptive neurotransmitter, SP, from rat spinal cord slices in a concentration-dependent manner (EC50 values=21.1 and 62.9 nM, respectively), consistent with the antinociceptive actions of omega-conopeptides. Following acute i.t. dosing, AM336 evoked dose-dependent antinociception (ED50 approximately 0.110 nmol) but the doses required to produce side-effects were an order of magnitude larger than the doses required to produce antinociception. For i.t. doses of MVIIA0.07 nmol, produced a dose-dependent decrease in antinociception but the incidence and severity of the side-effects continued to increase for all doses of MVIIA investigated, suggesting that dose-titration with MVIIA in the clinical setting, may be difficult.

  14. Low-voltage operation of ZrO2-gated n-type thin-film transistors based on a channel formed by hybrid phases of SnO and SnO2.

    Science.gov (United States)

    Chu, Hsin-Chueh; Shen, Yung-Shao; Hsieh, Ching-Heng; Huang, Jia-Hong; Wu, Yung-Hsien

    2015-07-22

    With SnO typically regarded as a p-type oxide semiconductor, an oxide semiconductor formed by hybrid phases of mainly SnO and a small amount of SnO2 with an average [O]/[Sn] ratio of 1.1 was investigated as a channel material for n-type thin-film transistors (TFTs). Furthermore, an appropriate number of oxygen vacancies were introduced into the oxide during annealing at 400 °C in ambient N2, making both SnO and SnO2 favorable for current conduction. By using high-κ ZrO2 with a capacitance equivalent thickness of 13.5 nm as the gate dielectric, the TFTs processed at 400 °C demonstrated a steep subthreshold swing (SS) of 0.21 V/dec, and this can be ascribed to the large gate capacitance along with a low interface trap density (Dit) value of 5.16 × 10(11) cm(-2) eV(-1). In addition, the TFTs exhibit a relatively high electron mobility of 7.84 cm(2)/V·s, high ON/OFF current ratios of up to 2.5 × 10(5), and a low gate leakage current at a low operation voltage of 3 V. The TFTs also prove its high reliability performance by showing negligible degradation of SS and threshold voltage (VT) against high field stress (-10 MV/cm). When 3% oxygen annealing is combined with a thinner channel thickness, TFTs with even higher ION/IOFF ratios exceeding 10(7) can also be obtained. With these promising characteristics, the overall performance of the TFTs displays competitive advantages compared with other n-type TFTs formed on binary or even some multicomponent oxide semiconductors and paves a promising and economic avenue to implement an n-type oxide semiconductor without doping for production-worthy TFT technology. Most importantly, when combined with the typical SnO-based p-type oxide semiconductor, it would usher in a new era in achieving high-performance complementary metal oxide semiconductor circuits by using the same SnO-based oxide semiconductor.

  15. Control of electrical conduction in DNA using hole doping

    Science.gov (United States)

    Lee, Hea-Yeon; Taniguchi, Masateru; Yoo, K. H.; Otsuka, Youichi; Tanaka, Hidekazu; Kawai, Tomoji

    2002-03-01

    Control of electrical conduction in DNA using hole doping H.Y.Lee1, M.Taniguchi1, K.H.Yoo2, Y.Otsuka1 H.Tanaka1 and T.Kawai1 1The Institute of Scientific and Industrial Research(ISIR), Osaka University, Osaka, Japan. 2Department of Physics, Younsei University, Seoul, Korea Possible applications of DNA molecules in electronic devices and biosensors were suggested almost ten years ago A DNA structure containing a single type of base pair appears to be a good candidate for conduction along the \\x81E-electron clouds of the stacked bases. There have been lots of investigations on conduction mechanisms of the DNA molecules. However, it is not still clear whether the observed conductions of some DNA molecules come from motions of either ionic charges or other carriers. Although the basic mechanism for DNA-mediated charge transport should be understood for electronic applications, there have been divergent reports on its nature. And I will be present the research for the charge carrier conduction of DNA film under oxygen and iodine gas by using 10¡V100 nm gap. The doping studies using oxygen and iodine gas can provide a definite answer for the carrier conduction mechanism and also a possible method to control the carrier concentration in DNA molecules. Using oxygen and iodine adsorption experiments on the poly (dG)-poly (dC) DNA molecules, we will show that their conductance becomes increased easily by several orders of magnitudes due to the hole doping, which is a characteristic behavior of a p-type semiconductor. On the other hand, we will also show that the poly (dA) - poly (dT) DNA molecules behave as an n-type semiconductor. Our works indicate that the concentration and the type of carriers in the DNA molecules could be controlled using proper doping methods. We expect that this would be a major breakthrough in DNA-based nano-electronics, similar to the fact that the doped conductive has polyacetylene opened up a new field of electronics with exciting implications

  16. Emitter formation using laser doping technique on n- and p-type c-Si substrates

    Science.gov (United States)

    López, G.; Ortega, P.; Colina, M.; Voz, C.; Martín, I.; Morales-Vilches, A.; Orpella, A.; Alcubilla, R.

    2015-05-01

    In this work laser doping technique is used to create highly-doped regions defined in a point-like structure to form n+/p and p+/n junctions applying a pulsed Nd-YAG 1064 nm laser in the nanosecond regime. In particular, phosphorous-doped silicon carbide stacks (a-SiCx/a-Si:H (n-type)) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) and aluminum oxide (Al2O3) layers deposited by atomic layer deposition (ALD) on 2 ± 0.5 Ω cm p- and n-type FZ c-Si substrates respectively are used as dopant sources. Laser power and number of pulses per spot are explored to obtain the optimal electrical behavior of the formed junctions. To assess the quality of the p+ and n+ regions, the junctions are electrically contacted and characterized by means of dark J-V measurements. Additionally, a diluted HF treatment previous to front metallization has been explored in order to know its impact on the junction quality. The results show that fine tuning of the energy pulse is critical while the number of pulses has minor effect. In general the different HF treatments have no impact in the diode electrical behavior except for an increase of the leakage current in n+/p junctions. The high electrical quality of the junctions makes laser doping, using dielectric layers as dopant source, suitable for solar cell applications. Particularly, a potential open circuit voltage of 0.64 V (1 sun) is expected for a finished solar cell.

  17. Myostatin: genetic variants, therapy and gene doping

    Directory of Open Access Journals (Sweden)

    André Katayama Yamada

    2012-09-01

    Full Text Available Since its discovery, myostatin (MSTN has been at the forefront of muscle therapy research because intrinsic mutations or inhibition of this protein, by either pharmacological or genetic means, result in muscle hypertrophy and hyperplasia. In addition to muscle growth, MSTN inhibition potentially disturbs connective tissue, leads to strength modulation, facilitates myoblast transplantation, promotes tissue regeneration, induces adipose tissue thermogenesis and increases muscle oxidative phenotype. It is also known that current advances in gene therapy have an impact on sports because of the illicit use of such methods. However, the adverse effects of these methods, their impact on athletic performance in humans and the means of detecting gene doping are as yet unknown. The aim of the present review is to discuss biosynthesis, genetic variants, pharmacological/genetic manipulation, doping and athletic performance in relation to the MSTN pathway. As will be concluded from the manuscript, MSTN emerges as a promising molecule for combating muscle wasting diseases and for triggering wide-ranging discussion in view of its possible use in gene doping.Desde sua descoberta, a miostatina (MSTN entrou na linha de frente em pesquisas relacionadas às terapias musculares porque mutações intrínsecas ou inibição desta proteína tanto por abordagens farmacológicas como genéticas resultam em hipertrofia muscular e hiperplasia. Além do aumento da massa muscular, a inibição de MSTN potencialmente prejudica o tecido conectivo, modula a força muscular, facilita o transplante de mioblastos, promove regeneração tecidual, induz termogênese no tecido adiposo e aumenta a oxidação na musculatura esquelética. É também sabido que os atuais avanços em terapia gênica têm uma relação com o esporte devido ao uso ilícito de tal método. Os efeitos adversos de tal abordagem, seus efeitos no desempenho de atletas e métodos para detectar doping genético s

  18. Investigation of pentacene growth on SiO2 gate insulator after photolithography for nitrogen-doped LaB6 bottom-contact electrode formation

    Science.gov (United States)

    Maeda, Yasutaka; Hiroki, Mizuha; Ohmi, Shun-ichiro

    2018-04-01

    Nitrogen-doped (N-doped) LaB6 is a candidate material for the bottom-contact electrode of n-type organic field-effect transistors (OFETs). However, the formation of a N-doped LaB6 electrode affects the surface morphology of a pentacene film. In this study, the effects of surface treatments and a N-doped LaB6 interfacial layer (IL) were investigated to improve the pentacene film quality after N-doped LaB6 electrode patterning with diluted HNO3, followed by resist stripping with acetone and methanol. It was found that the sputtering damage during N-doped LaB6 deposition on a SiO2 gate insulator degraded the crystallinity of pentacene. The H2SO4 and H2O2 (SPM) and diluted HF treatments removed the damaged layer on the SiO2 gate insulator surface. Furthermore, the N-doped LaB6 IL improved the crystallinity of pentacene and realized dendritic grain growth. Owing to these surface treatments, the hole mobility improved from 2.8 × 10‑3 to 0.11 cm2/(V·s), and a steep subthreshold swing of 78 mV/dec for the OFET with top-contact configuration was realized in air even after bottom-contact electrode patterning.

  19. Funneling effect of alpha particles on the charge collection efficiency in N type silicon surface barrier detector

    International Nuclear Information System (INIS)

    Boorboor, S.; Feghhi, S.A.H.; Jafari, H.

    2014-01-01

    Highlights: • Field funneling due to SEE in microelectronic device affects the charge collection efficiency. • Charge collection efficiency from alpha particles in a N type SSB device was calculated. • GEANT4, a Monte Carlo code and ATLAS, a numerical code have been used. • The simulation results have been validated through comparison with the experimental results. - Abstract: There are three different mechanisms of charge collection in a semiconductor charge particle detector, such as the drift of carriers in depletion zone, the drift of carriers in an extended electrical field along the ion track or funneling effect and the diffusion of carriers. In this work, the funneling effect on charge collection efficiency due to alpha particle track in a N type silicon surface barrier detector has been investigated. GEANT4, as Monte Carlo code, has been used for estimation of the deposit energy distribution in the component. In addition, the semiconductor device simulator, ATLAS, has been used in calculation of charge collection efficiency. The simulation results have been validated through comparison with the available experimental results. The calculated charge collection efficiency has good agreement with experiment. Without considering the funneling effect and diffusion, the calculation results underestimate the charge collection efficiency within 60%. Our overall results were indicative of the fact that considering funneling effect, considerably improves the accuracy of the charge collection efficiency estimation

  20. Cyclopentadithiophene–naphthalenediimide polymers; synthesis, characterisation, and n-type semiconducting properties in field-effect transistors and photovoltaic devices

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chun-Han [Department of Chemical Engineering, Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing-Hua University, 101, Sec. 2, Kuang-Fu Road, Hsin-Chu 30013, Taiwan (China); Kettle, Jeff [School of Electronics, Bangor University, Dean st., Bangor, Gwynedd, LL57 1UT Wales (United Kingdom); Horie, Masaki, E-mail: mhorie@mx.nthu.edu.tw [Department of Chemical Engineering, Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing-Hua University, 101, Sec. 2, Kuang-Fu Road, Hsin-Chu 30013, Taiwan (China)

    2014-04-01

    The synthesis, characterisation, and device performance of a series of cyclopentadithiophene (CPDT)-naphthalenediimide (NDI) donor-acceptor-donor (D-A-D) polymers is reported. The monomers with various alkyl chains are synthesised via direct arylation using palladium complex catalyst. The monomers are then polymerised by oxidative polymerisation using FeCl{sub 3} to provide high molecular weight polymers (M{sub n} = 21,800–76,000). The polymer films show deep-red absorption including near-infrared region up to 1100 nm to give optical bandgap of approximately 1.16 eV. The polymers exhibit only n-type semiconducting properties giving the highest electron mobility of 9 × 10{sup -3} cm{sup 2} V{sup −1} s{sup −1} in organic field-effect transistors (OFETs). Organic photovoltaic (OPV) devices are fabricated from solutions of the polymers as acceptors and poly(3-hexylthiophene) (P3HT) as a donor. - Highlights: • Cyclopentadithiophene–naphthalenediimide oligomers were prepared by direct arylation. • The oligomers were polymerised by oxidative reaction using iron(III)chloride. • The polymer films show deep-red absorption up to 1100 nm with a bandgap of 1.1 eV. • The polymers exhibit only n-type semiconducting properties in OFETs and OPVs.

  1. Clinical features of neuromuscular disorders in patients with N-type voltage-gated calcium channel antibodies

    Directory of Open Access Journals (Sweden)

    Andreas Totzeck

    2016-09-01

    Full Text Available Neuromuscular junction disorders affect the pre- or postsynaptic nerve to muscle transmission due to autoimmune antibodies. Members of the group like myasthenia gravis and Lambert-Eaton syndrome have pathophysiologically distinct characteristics. However, in practice, distinction may be difficult. We present a series of three patients with a myasthenic syndrome, dropped-head syndrome, bulbar and respiratory muscle weakness and positive testing for anti-N-type voltage-gated calcium channel antibodies. In two cases anti-acetylcholin receptor antibodies were elevated, anti-P/Q-type voltage-gated calcium channel antibodies were negative. All patients initially responded to pyridostigmine with a non-response in the course of the disease. While one patient recovered well after treatment with intravenous immunoglobulins, 3,4-diaminopyridine, steroids and later on immunosuppression with mycophenolate mofetil, a second died after restriction of treatment due to unfavorable cancer diagnosis, the third patient declined treatment. Although new antibodies causing neuromuscular disorders were discovered, clinical distinction has not yet been made. Our patients showed features of pre- and postsynaptic myasthenic syndrome as well as severe dropped-head syndrome and bulbar and axial muscle weakness, but only anti-N-type voltage-gated calcium channel antibodies were positive. When administered, one patient benefited from 3,4-diaminopyridine. We suggest that this overlap-syndrome should be considered especially in patients with assumed seronegative myasthenia gravis and lack of improvement under standard therapy.

  2. Linear and nonlinear resonance features of an erbium-doped fibre ...

    Indian Academy of Sciences (India)

    2014-07-01

    Jul 1, 2014 ... 147–159. Linear and nonlinear resonance features of an erbium-doped fibre ring laser under cavity-loss modulation. ADITI GHOSH1 and R VIJAYA2,∗. 1Fibre Optics and Photonics Division, Central Glass and Ceramic Research Institute,. Council of Scientific and Industrial Research, Kolkata 700 032, India.

  3. Superconductor-semiconductor-superconductor planar junctions of aluminium on DELTA-doped gallium arsenide

    DEFF Research Database (Denmark)

    Taboryski, Rafael Jozef; Clausen, Thomas; Kutchinsky, jonatan

    1997-01-01

    We have fabricated and characterized planar superconductor-semiconductor-superconductor (S-Sm-S) junctions with a high quality (i.e. low barrier) interface between an n++ modulation doped conduction layer in MBE grown GaAs and in situ deposited Al electrodes. The Schottky barrier at the S-Sm inte...

  4. Andreev reflections at interfaces between delta-doped GaAs and superconducting Al films

    DEFF Research Database (Denmark)

    Taboryski, Rafael Jozef; Clausen, Thomas; Hansen, Jørn Bindslev

    1996-01-01

    By placing several Si delta-doped layers close to the surface of a GaAs molecular beam epitaxy-grown crystal, we achieve a compensation of the Schottky barrier and obtain a good Ohmic contact between an in situ deposited (without breaking the vacuum) Al metallization layer and a highly modulation...

  5. Linear and nonlinear resonance features of an erbium-doped fibre ...

    Indian Academy of Sciences (India)

    2014-07-01

    Jul 1, 2014 ... Abstract. The continuous-wave output of a single-mode erbium-doped fibre ring laser when sub- jected to cavity-loss modulation is found to exhibit linear as well as nonlinear resonances. At sufficiently low driving amplitude, the system resembles a linear damped oscillator. At higher amplitudes, the ...

  6. Identifying Antisite and Vacancy Defects in n-doped Bi2Se3 Topological Insulators from Scanning Tunneling Microscopy and First Principles Calculations

    Science.gov (United States)

    Jeon, Jeong Heum; Park, Joon-Suh; Kim, Howon; Jang, Won Jun; Han, Jinhee; Lee, Hyungjun; Choi, Hyung-Joon; Kahng, Se-Jong

    2014-03-01

    Intrinsic defects are the major sources of n-type doping character in Bi2Se3 topological insulators, but their structural nature remains unsettled; Theoretical calculations predicted that SeBi antisite was the most preferred under Se-rich, i.e. molecular beam epitaxy conditions, but there has been no report on its experimental observation. Here, we present our energy-dependent atomic resolution scanning tunneling microscopy (STM) images for intrinsic defects obtained from Bi2Se3 thin films grown under Se-rich conditions. We observed two types of defects, and identified them as SeBi antisite and Bi vacancy located at Bi layer right below surface Se layer, by comparing experimental STM images with the simulated ones obtained from first principles calculations. Our study shows that, in agreement with previous predictions, not Se-vacancy at surface but SeBi antisite is the origin of n-type doping in our Bi2Se3.

  7. Fabrication and Thermoelectric Properties of n-Type CoSb2.85Te0.15 Using Selective Laser Melting.

    Science.gov (United States)

    Yan, Yonggao; Ke, Hongquan; Yang, Jihui; Uher, Ctirad; Tang, Xinfeng

    2018-04-25

    We report a nonequilibrium fabrication method of n-type CoSb 2.85 Te 0.15 skutterudites using selective laser melting (SLM) technology. A powder of CoSb 2.85 Te 0.15 was prepared by self-propagating high-temperature synthesis (SHS) and served as the raw material for the SLM process. The effect of SLM processing parameters such as the laser power and scanning speed on the quality of the forming CoSb 2.85 Te 0.15 thin layers was systematically analyzed, and the optimal processing window for SLM was determined. A brief postannealing at 450 °C for 4 h, following the SLM process, has resulted in a phase-pure CoSb 2.85 Te 0.15 bulk material deposited on a Ti substrate. The Seebeck coefficient of the annealed SLM prepared bulk material is close to that of the sample prepared by the traditional sintering method, and its maximum ZT value reached 0.56 at 823 K. Moreover, a Ti-Co-Sb ternary compound transition layer of about 70 μm in thickness was found at a dense interface between CoSb 2.85 Te 0.15 and the Ti substrate. The contact resistivity was measured as 37.1 μΩcm 2 . The results demonstrate that SLM, coupled with postannealing, can be used for fabrication of incongruently melting skutterudite compounds on heterogeneous substrates. This lays an important foundation for the follow-up research utilizing energy efficient SHS and SLM processes in rapid printing of thermoelectric modules.

  8. Fabrication of p-type conductivity in SnO{sub 2} thin films through Ga doping

    Energy Technology Data Exchange (ETDEWEB)

    Tsay, Chien-Yie, E-mail: cytsay@fcu.edu.tw; Liang, Shan-Chien

    2015-02-15

    Highlights: • P-type Ga-doped SnO{sub 2} semiconductor films were prepared by sol-gel spin coating. • Optical bandgaps of the SnO{sub 2}:Ga films are narrower than that of the SnO{sub 2} film. • SnO{sub 2}:Ga films exhibited p-type conductivity as Ga doping content higher than 10%. • A p-n heterojunction composed of p-type SnO{sub 2}:Ga and n-type ZnO:Al was fabricated. - Abstract: P-type transparent tin oxide (SnO{sub 2}) based semiconductor thin films were deposited onto alkali-free glass substrates by a sol-gel spin-coating method using gallium (Ga) as acceptor dopant. In this study, we investigated the influence of Ga doping concentration ([Ga]/[Sn] + [Ga] = 0%, 5%, 10%, 15%, and 20%) on the structural, optical and electrical properties of SnO{sub 2} thin films. XRD analysis results showed that dried Ga-doped SnO{sub 2} (SnO{sub 2}:Ga) sol-gel films annealed in oxygen ambient at 520 °C for 1 h exhibited only the tetragonal rutile phase. The average optical transmittance of as-prepared thin film samples was higher than 87.0% in the visible light region; the optical band gap energy slightly decreased from 3.92 eV to 3.83 eV with increases in Ga doping content. Hall effect measurement showed that the nature of conductivity of SnO{sub 2}:Ga thin films changed from n-type to p-type when the Ga doping level was 10%, and when it was at 15%, Ga-doped SnO{sub 2} thin films exhibited the highest mean hole concentration of 1.70 × 10{sup 18} cm{sup -3}. Furthermore, a transparent p-SnO{sub 2}:Ga (Ga doping level of 15%)/n-ZnO:Al (Al doping level of 2%) heterojunction was fabricated on alkali-free glass. The I-V curve measurement for the p-n heterojunction diode showed a typical rectifying characteristic with a forward turn-on voltage of 0.65 V.

  9. Analysis of electronic parameters of nanostructure copper doped cadmium oxide/p-silicon heterojunction

    Energy Technology Data Exchange (ETDEWEB)

    Karatas, Suekrue, E-mail: skaratas@ksu.edu.tr [Department of Physics, Faculty of Science, Suetcue Imam University, Karamanmaras (Turkey); Yakuphanoglu, Fahrettin [Department of Physics, Faculty of Science, Firat University, Elazig (Turkey)

    2012-10-05

    Highlights: Black-Right-Pointing-Pointer The copper doped cadmium oxide (CdO) heterojunction diodes were fabricated by sol-gel method. Black-Right-Pointing-Pointer The electrical properties of Cu doped CdO/p-Si heterojunction diode have been investigated. Black-Right-Pointing-Pointer A strong effect of the Cu-doped content on the I-V characteristics of the diodes was found. Black-Right-Pointing-Pointer It is evaluated that the electrical performance of the CdO/p-Si diode can be controlled by Cu doped. - Abstract: The nanostructure Cu-doped CdO thin film was grown on p-type silicon substrate by sol-gel method. An Al/Cu doped CdO/p-Si heterojunction diode was fabricated. The values of ideality factor and barrier height for the Al/n-type CdO/p-Si heterojunction were obtained as 5.99 and 0.69 eV, respectively. A modified Norde function combined with conventional forward I-V method was used to extract the junction parameters including the ideality factor, barrier height and series resistance. Norde function was compared with the Cheung functions and it is seen that there is a good agreement with both method for the series resistance values. Furthermore, the interface state density (N{sub SS}) as a function of energy distribution (E{sub SS} - E{sub V}) was extracted from the forward-bias I-V measurements by taking into account the bias dependence of the effective barrier height and series resistance.

  10. Reflectivity-modulated grating-mirror

    DEFF Research Database (Denmark)

    2012-01-01

    region in a layer structure comprising a p- and a n-doped semiconductor layer with an electrooptic material layer (12) arranged there between. The grating region comprises a grating structure formed by periodic perforations to change the refractive index periodically in directions normal...... a reflectivity with little or no out coupling and a reflectivity with normal out coupling, wherein lasing in the VCL is supported at both the first and the second reflectivity. As the out coupling mirror modulates the output, the lasing does not need to be modulated, and the invention provides the advantage...

  11. Magnetic control of single transition metal doped MoS{sub 2} through H/F chemical decoration

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Sizhe [Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105 (China); He, Junjie [Faculty of Science, Charles University in Prague, 128 43 Prague 2 (Czech Republic); Zhou, Pan [Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105 (China); Sun, L.Z., E-mail: lzsun@xtu.edu.cn [Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105 (China)

    2017-01-15

    Using density function theory, we study the spin state control of transition metal doped MoS{sub 2} through H/F chemical decoration. The results indicate that the ground spin state of single TM (Mn, Fe, and Co) doped MoS{sub 2} is sensitive to its chemical environment. H/F chemical decoration on TM can effectively modulate their magnetic moment up to 1 μ{sub B}, especially for the Mn doped system, the F decoration will produce the system show “spin ON” to “spin OFF” transition. Interestingly, the H decoration will increase the magnetic moment of TM doped MoS{sub 2} with 1 μ{sub B}, however, the F decoration will reduce the magnetic moment of TM doped MoS{sub 2} with 1 μ{sub B}. Such modulation derives from the anti-bonding and bonding nature between TM and H/F atom, respectively. Our results may open a new route to apply TM doped MoS{sub 2} to multistate memory. - Highlights: • Spin state control of TM doped MoS2 through H/F chemical decoration. • “Spin ON” to “spin OFF” transition. • Anti-bonding and bonding nature between TM and H/F atom.

  12. Optimal process parameters for phosphorus spin-on-doping of germanium

    Energy Technology Data Exchange (ETDEWEB)

    Boldrini, Virginia [Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, Via Marzolo 8, I-35131 Padova (Italy); INFN-LNL, Viale dell’Università 2, I-35020 Legnaro, Padova (Italy); Carturan, Sara Maria, E-mail: sara.carturan@lnl.infn.it [Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, Via Marzolo 8, I-35131 Padova (Italy); INFN-LNL, Viale dell’Università 2, I-35020 Legnaro, Padova (Italy); Maggioni, Gianluigi; Napolitani, Enrico [Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, Via Marzolo 8, I-35131 Padova (Italy); INFN-LNL, Viale dell’Università 2, I-35020 Legnaro, Padova (Italy); Napoli, Daniel Ricardo [INFN-LNL, Viale dell’Università 2, I-35020 Legnaro, Padova (Italy); Camattari, Riccardo [INFN Sezione di Ferrara, Dipartimento di Fisica, Università di Ferrara, Via Saragat 1, 44122, Ferrara (Italy); De Salvador, Davide [Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, Via Marzolo 8, I-35131 Padova (Italy); INFN-LNL, Viale dell’Università 2, I-35020 Legnaro, Padova (Italy)

    2017-01-15

    Highlights: • Optimized protocol for the application of phosphorus spin-on-doping to Ge surface. • Homogeneous n-type Ge layers, fully electrically active, are obtained. • Crucial parameters for SOD curing are relative humidity, time and temperature. • Characterization of Ge loss from the surface into the SOD film by diffusion. • Spike annealing in standard tube chamber furnace are performed. - Abstract: The fabrication of homogeneously doped germanium layers characterized by total electrical activation is currently a hot topic in many fields, such as microelectronics, photovoltaics, optics and radiation detectors. Phosphorus spin-on-doping technique has been implemented on Ge wafers, by developing a protocol for the curing process and subsequent diffusion annealing for optimal doping. Parameters such as relative humidity and curing time turned out to affect the surface morphology, the degree of reticulation reached by the dopant source and the amount of dopant available for diffusion. After spike annealing in a conventional furnace, diffusion profiles and electrical properties have been measured. Ge loss from the surface during high-temperature annealing, due to diffusion into the source film, has been observed and quantified.

  13. P-type hole mobility measurement in Na-doped BaSnO3

    Science.gov (United States)

    Hong, Sungyun; Jang, Yeaju; Park, Jisung; Char, Kookrin

    P-type doping in oxide materials has been a difficult task because of the oxygen vacancies. Taking advantage of the excellent oxygen stability in BaSnO3 (BSO), we replaced Ba with Na in BSO to achieve p-type doping. Ba1-xNaxSnO3 (BNSO) films with varying dopant ratios were epitaxially grown by the pulsed laser deposition technique. We confirmed that the BNSO films were properly grown and determined their lattice constants with respect to the dopant ratio by x-ray diffraction. Due to the high resistance of the films at room temperature, we measured the transport properties of the BNSO films at temperatures ranging from 200 C to 400 C. Hall resistance measurements in a +/- 5 kG magnetic field were performed to confirm that the films are indeed p-type. As the temperature increased, the hole carrier concentration of the films increased while the film resistance decreased. The hole mobility values, in the tens of cm2/Vsec range, were found to decrease with the temperature. We will present the complete doping rate and temperature dependence of the hole mobility and compare their behavior with those of n-type La-doped BSO. Samsung science and technology foundation.

  14. CO2 Sensors Based on Nanocrystalline SnO2 Doped with CuO

    Science.gov (United States)

    Xu, Jennifer C.; Hunter, Gary W.; Liu, Chung Chiun; Ward, Benjamin J.

    2008-01-01

    Nanocrystalline tin oxide (SnO2) doped with copper oxide (CuO) has been found to be useful as an electrical-resistance sensory material for measuring the concentration of carbon dioxide in air. SnO2 is an n-type semiconductor that has been widely used as a sensing material for detecting such reducing gases as carbon monoxide, some of the nitrogen oxides, and hydrocarbons. Without doping, SnO2 usually does not respond to carbon dioxide and other stable gases. The discovery that the electrical resistance of CuO-doped SnO2 varies significantly with the concentration of CO2 creates opportunities for the development of relatively inexpensive CO2 sensors for detecting fires and monitoring atmospheric conditions. This discovery could also lead to research that could alter fundamental knowledge of SnO2 as a sensing material, perhaps leading to the development of SnO2-based sensing materials for measuring concentrations of oxidizing gases. Prototype CO2 sensors based on CuO-doped SnO2 have been fabricated by means of semiconductor-microfabrication and sol-gel nanomaterial-synthesis batch processes that are amendable to inexpensive implementation in mass production.

  15. Investigation Performance and Mechanisms of Inverted Polymer Solar Cells by Pentacene Doped P3HT : PCBM

    Directory of Open Access Journals (Sweden)

    Hsin-Ying Lee

    2014-01-01

    Full Text Available The inverted polymer solar cells (PSCs with pentacene-doped P3HT : PCBM absorption layers were fabricated. It was demonstrated that the pentacene doping modulated the electron mobility and the hole mobility in the resulting absorption layer. Furthermore, by varying the doping content, the optimal carrier mobility balance could be obtained. In addition, the pentacene doping led to an improvement in the crystallinity of the resulting films and made an enhancement in the light absorption, which was partly responsible for the performance improvement of the solar cells. Using the space-charge-limited current (SCLC method, it was determined that the balanced carrier mobility (μh/μe=1.000 was nearly achieved when a pentacene doping ratio of 0.065 by weight was doped into the P3HT : PCBM : pentacene absorption layer. Compared with the inverted PSCs without the pentacene doping, the short circuit current density and the power conversion efficiency of the inverted PSCs with the pentacene doping ratio of 0.065 were increased from 9.73 mA/cm2 to 11.26 mA/cm2 and from 3.39% to 4.31%, respectively.

  16. Conserved N-terminal negative charges support optimally efficient N-type inactivation of Kv1 channels.

    Directory of Open Access Journals (Sweden)

    Alison Prince

    Full Text Available N-type inactivation is produced by the binding of a potassium channel's N-terminus within the open pore, blocking conductance. Previous studies have found that introduction of negative charges into N-terminal inactivation domains disrupts inactivation; however, the Aplysia AKv1 N-type inactivation domain contains two negatively charged residues, E2 and E9. Rather than being unusual, sequence analysis shows that this N-terminal motif is highly conserved among Kv1 sequences across many phyla. Conservation analysis shows some tolerance at position 9 for other charged residues, like D9 and K9, whereas position 2 is highly conserved as E2. To examine the functional importance of these residues, site directed mutagenesis was performed and effects on inactivation were recorded by two electrode voltage clamp in Xenopus oocytes. We find that inclusion of charged residues at positions 2 and 9 prevents interactions with non-polar sites along the inactivation pathway increasing the efficiency of pore block. In addition, E2 appears to have additional specific electrostatic interactions that stabilize the inactivated state likely explaining its high level of conservation. One possible explanation for E2's unique importance, consistent with our data, is that E2 interacts electrostatically with a positive charge on the N-terminal amino group to stabilize the inactivation domain at the block site deep within the pore. Simple electrostatic modeling suggests that due to the non-polar environment in the pore in the blocked state, even a 1 Å larger separation between these charges, produced by the E2D substitution, would be sufficient to explain the 65× reduced affinity of the E2D N-terminus for the pore. Finally, our studies support a multi-step, multi-site N-type inactivation model where the N-terminus interacts deep within the pore in an extended like structure placing the most N-terminal residues 35% of the way across the electric field in the pore blocked

  17. Spectral modulation through controlling anions in nanocaged phosphors

    NARCIS (Netherlands)

    Bian, H.; Liu, Y.; Yan, D.; Zhu, H.; Liu, C.; Xu, C.S.; Liu, Y.; Zhang, H.; Wang, X.

    2013-01-01

    A new approach has been proposed and validated to modulate the emission spectra of europium-doped 12CaO center dot 7Al(2)O(3) phosphors by tuning the nonradiative and radiative transition rates, realized by controlling the sort and amount of the encaged anions. A single wavelength at 255 nm can

  18. Optical Controlled Terahertz Modulator Based on Tungsten Disulfide Nanosheet.

    Science.gov (United States)

    Fan, Zhiyuan; Geng, Zhaoxin; Lv, Xiaoqin; Su, Yue; Yang, Yuping; Liu, Jian; Chen, Hongda

    2017-11-01

    The terahertz (THz) modulator, which will be applied in next-generation wireless communication, is a key device in a THz communication system. Current THz modulators based on traditional semiconductors and metamaterials have limited modulation depth or modulation range. Therefore, a THz modulator based on annealed tungsten disulfide (WS 2 , p-type) and high-resistivity silicon (n-type) is demonstrated. Pumped by a laser, the modulator presents a laser power-dependent modulation effect. Ranging from 0.25 to 2 THz, the modulation depth reaches 99% when the pumping laser is 2.59 W/cm 2 . The modulator works because the p-n heterojunction can separate and limit carriers to change the conductivity of the device, which results in a modulation of the THz wave. The wide band gap of WS 2 can promote the separation and limitation of carriers to obtain a larger modulation depth, which provides a new direction for choosing new materials and new structures to fabricate a better THz modulator.

  19. Property database for single-element doping in ZnO obtained by automated first-principles calculations

    Science.gov (United States)

    Yim, Kanghoon; Lee, Joohee; Lee, Dongheon; Lee, Miso; Cho, Eunae; Lee, Hyo Sug; Nahm, Ho-Hyun; Han, Seungwu

    2017-01-01

    Throughout the past decades, doped-ZnO has been widely used in various optical, electrical, magnetic, and energy devices. While almost every element in the Periodic Table was doped in ZnO, the systematic computational study is still limited to a small number of dopants, which may hinder a firm understanding of experimental observations. In this report, we systematically calculate the single-element doping property of ZnO using first-principles calculations. We develop an automation code that enables efficient and reliable high-throughput calculations on thousands of possible dopant configurations. As a result, we obtain formation-energy diagrams for total 61 dopants, ranging from Li to Bi. Furthermore, we evaluate each dopant in terms of n-type/p-type behaviors by identifying the major dopant configurations and calculating carrier concentrations at a specific dopant density. The existence of localized magnetic moment is also examined for spintronic applications. The property database obtained here for doped ZnO will serve as a useful reference in engineering the material property of ZnO through doping.

  20. Preparation and characterization of Co-doped TiO2 materials for solar light induced current and photocatalytic applications

    International Nuclear Information System (INIS)

    Ganesh, Ibram; Gupta, A.K.; Kumar, P.P.; Chandra Sekhar, P.S.; Radha, K.; Padmanabham, G.; Sundararajan, G.

    2012-01-01

    Different amounts of Co-doped TiO 2 powders and thin films were prepared by following a conventional co-precipitation and sol–gel dip coating technique, respectively. The synthesized powders and thin films were subjected to thermal treatments from 400 to 800 °C and were thoroughly investigated by means of X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive analysis with X-rays, FT-infrared, FT-Raman, diffuse reflectance spectroscopy, ultraviolet–visible spectroscopy, BET surface area, zeta potential, flat band potential measurements, band-gap energy, etc. The photocatalytic ability of the powders was evaluated by methylene blue (MB) degradation studies. The thin films were characterized by photocurrent and ultraviolet–visible (UV–Vis) spectroscopy techniques. The characterization results suggest that the Co-doped TiO 2 powders synthesized in this study consist mainly anatase phase, and possess reasonably high specific surface area, low band gap energy and flat band potentials amenable to water oxidation in photoelectrochemical (PEC) cells. The photocatalytic degradation of MB over Co-doped TiO 2 powders followed the Langmuir–Hinshelwood first order reaction rate relationship. The 0.1 wt.% Co-doped TiO 2 composition provided the higher photocurrent, n-type semi-conducting behavior and higher photocatalytic activity among various Co-doped TiO 2 compositions and pure TiO 2 investigated.

  1. Nanostructure Size Determination in N+-Type Porous Silicon by X-Ray diffractometry and Raman Spectroscopy

    CERN Document Server

    Ramirez-Porras, A

    1997-01-01

    A series of porous silicon surfaces were obtained after different exposition times of electrochemical etching on cristalline n+- type silicon in presence of hydrofluoric acid. These kind of surfaces show photoluminescence when illuminated by UV light. One possible explanation for this is that the treated surface is made up of small crystallites the nanometer scale that split away the semiconductor band edges up to optical photon energies for the band- to -band recombination processes. In this study, a nanometer size determination of such proposed structures was performed by the use of X-Ray Diffractometry and Raman Spectroscopy. The result suggest the consistency between the so called Quantum Confined Model and the experimental results. (Author)

  2. Application of the new LDA+GTB method for the band structure calculation of n-type cuprates

    International Nuclear Information System (INIS)

    Korshunov, M.M.; Ovchinnikov, S.G.; Gavrichkov, V.A.; Nekrasov, I.A.; Pchelkina, Z.V.; Anisimov, V.I.

    2006-01-01

    A novel hybrid scheme is proposed and applied for band structure calculations of undoped n-type cuprate Nd 2 CuO 4 . The ab initio LDA calculation is used to obtain single electron and Coulomb parameters of the multiband Hubbard-type model. In strong correlation regime the electronic structure within this model is calculated by the generalized tight-binding (GTB) method, that combines the exact diagonalization of the model Hamiltonian for a small cluster with perturbation treatment of the intercluster hopping and interactions. For Nd 2 CuO 4 , this scheme results in charge transfer insulator with value of the gap and band dispersion in agreement to the experimental data

  3. Inductively coupled plasma-induced defects in n-type GaN studied from Schottky diode characteristics

    International Nuclear Information System (INIS)

    Nakamura, W.; Tokuda, Y.; Ueda, H.; Kachi, T.

    2006-01-01

    Inductively coupled plasma-(ICP-)induced defects in n-type GaN have been studied from current-voltage (I-V) characteristics and deep-level transient spectroscopy (DLTS) for Schottky diodes fabricated on etched surfaces. The samples after ICP etching show the ohmic I-V characteristics. Schottky characteristics are obtained after annealing at 600 and 800 deg. C in N 2 , but are not restored to that of the control samples. DLTS shows that the effect of ICP etching is small on the region beyond 80 nm from the surface. These results suggest that there remain ICP-induced damage in the near-surface region after thermal annealing

  4. Effects of thermal budget in n-type bifacial solar cell fabrication processes on effective lifetime of crystalline silicon

    Directory of Open Access Journals (Sweden)

    Tomihisa Tachibana

    2017-04-01

    Full Text Available The effects of residual C on cell properties are investigated from the view point of thermal budget in the n-type bifacial cell processes. Implied Voc obtained from wafers with same Oi concentration depend on the thermal budgets decreases as the Cs concentration increases. The Voc values vary depending on the wafer with different growth cooling rate. To analyze the effect of thermal budget correspond to solar cell fabrication process, CZ wafers with almost the same Oi concentrations are prepared. One of the wafers with relatively high residual Cs concentration shows the longer lifetime than the initial value after the 950 oC annealing step. On the other hand, the lifetime of a wafer with relatively low Cs concentration dramatically decreased by the same process due to the O segregation. These results suggest that it is important to choose appropriate wafer specification, starting with feedstock material, for increasing the solar cell efficiency.

  5. Superluminal propagation in a poly-chromatically driven gain assisted four-level N-type atomic system

    International Nuclear Information System (INIS)

    Bacha, Bakht Amin; Ahmad, Iftikhar; Ullah, Arif; Ali, Hazrat

    2013-01-01

    We investigate the behavior of light propagation in an N-type four-level gain assisted model (Agarwal and Dasgupta 2004 Phys. Rev. A 70 023802) under poly-chromatic pump fields. The system exhibits interesting results of multiple controllable pairs of the gain doublet profile with changes in the intensity of the control field. We observe multiple anomalous dispersive regions for superluminal propagation in the medium. A negative group velocity of −37.50 m s −1 with a negative time delay of −8 ms is observed between each gain doublet in anomalous dispersive regions. This generalized model and its predictions can be tested with existing experimental setups. (paper)

  6. Comparative study of long alkyl chain substituted naphthalene diimide derivatives as n-type organic thin-film transistor materials

    Science.gov (United States)

    Ichikawa, Musubu; Iwasaki, Kazuaki; Ohyama, Atsuro; Miyazawa, Jun; Yokota, Yoichiro; Hirata, Naoki; Oguma, Naomi

    2017-11-01

    In this study, vacuum-evaporated thin films of several naphthalene tetracarboxylic acid diimide derivatives substituted at the N and N‧ positions with long normal alkyl chains of varying lengths (NTCDI-Cn) were evaluated as active materials for n-type organic thin-film transistors (TFTs). The electron mobility (μe) of the TFTs increased with increasing chain length from octyl (NTCDI-C8) to pentadecyl (NTCDI-C15); those of NTCDI-C15 and C18 TFTs were of 0.262 ± 0.016 and 0.222 ± 0.016 cm2 V-1 s-1, respectively. However, the threshold voltage of the TFTs increased with increasing chain length.

  7. Staircase and saw-tooth field emission steps from nanopatterned n-type GaSb surfaces

    CERN Document Server

    Kildemo, M.; Le Roy, S.; Søndergård, E.

    2009-01-01

    High resolution field emission experiments from nanopatterned GaSb surfaces consisting of densely packed nanocones prepared by low ion-beam-energy sputtering are presented. Both uncovered and metal-covered nanopatterned surfaces were studied. Surprisingly, the field emission takes place by regular steps in the field emitted current. Depending on the field, the steps are either regular, flat, plateaus, or saw-tooth shaped. To the author’s knowledge, this is the first time that such results have been reported. Each discrete jump in the field emission may be understood in terms of resonant tunneling through an extended surface space charge region in an n-type, high aspect ratio, single GaSb nanocone. The staircase shape may be understood from the spatial distribution of the aspect ratio of the cones.

  8. Diodes of nanocrystalline SiC on n-/n+-type epitaxial crystalline 6H-SiC

    Science.gov (United States)

    Zheng, Junding; Wei, Wensheng; Zhang, Chunxi; He, Mingchang; Li, Chang

    2018-03-01

    The diodes of nanocrystalline SiC on epitaxial crystalline (n-/n+)6H-SiC wafers were investigated, where the (n+)6H-SiC layer was treated as cathode. For the first unit, a heavily boron doped SiC film as anode was directly deposited by plasma enhanced chemical vapor deposition method on the wafer. As to the second one, an intrinsic SiC film was fabricated to insert between the wafer and the SiC anode. The third one included the SiC anode, an intrinsic SiC layer and a lightly phosphorus doped SiC film besides the wafer. Nanocrystallization in the yielded films was illustrated by means of X-ray diffraction, transmission electronic microscope and Raman spectrum respectively. Current vs. voltage traces of the obtained devices were checked to show as rectifying behaviors of semiconductor diodes, the conduction mechanisms were studied. Reverse recovery current waveforms were detected to analyze the recovery performance. The nanocrystalline SiC films in base region of the fabricated diodes are demonstrated as local regions for lifetime control of minority carriers to improve the reverse recovery properties.

  9. Doping effects of Fe ion on magnetic anisotropy of YBa2Cu3Oy

    International Nuclear Information System (INIS)

    Ugawa, T.; Horii, S.; Maeda, T.; Haruta, M.; Shimoyama, J.

    2013-01-01

    Highlights: •We clarified orientation effects of Fe-doped Y123 in modulated rotating fields. •Y123 showed two different hard magnetic axes due to twin microstructures. •The two hard magnetic axes in Fe-doped Y123 were [1 0 0] and [1 1 0] directions. •Magnetic anisotropy of the [1 1 0] grain was higher than that of the [1 0 0] grain. -- Abstract: We report magnetic alignment of YBa 2 (Cu 1−x Fe x ) 3 O y (Fe-doped Y123, x = 0–0.1) powders under modulated rotation magnetic fields (MRFs) and roles of Fe ion as a determination factor of magnetic anisotropy in Y123. The Fe-free and Fe-doped Y123 powder samples aligned in the MRF of 10 T showed two different orientation types of the hard axis in Y123 grains. From an X-ray rocking curve measurement for the magnetically aligned powder samples of the Fe-doped Y123, inplane magnetic anisotropy for Y123 grains with the hard axis parallel to the [1 1 0] direction was found to be higher than that for Y123 grains with the hard axis parallel to the [0 1 0] direction

  10. Electronic properties of B and Al doped graphane: A hybrid density functional study

    Science.gov (United States)

    Mapasha, R. E.; Igumbor, E.; Andriambelaza, N. F.; Chetty, N.

    2018-04-01

    Using a hybrid density functional theory approach parametrized by Heyd, Scuseria and Ernzerhof (HSE06 hybrid functional), we study the energetics, structural and electronic properties of a graphane monolayer substitutionally doped with the B (BCH) and Al (AlCH) atoms. The BCH defect can be integrated within a graphane monolayer at a relative low formation energy, without major structural distortions and symmetry breaking. The AlCH defect relaxes outward of the monolayer and breaks the symmetry. The density of states plots indicate that BCH doped graphane monolayer is a wide band gap semiconductor, whereas the AlCH defect introduces the spin dependent mid gap states at the vicinity of the Fermi level, revealing a metallic character with the pronounced magnetic features. We further examine the response of the Al dependent spin states on the multiple charge states doping. We find that the defect formation energy, structural and electronic properties can be altered via charge state modulation. The +1 charge doping opens an energy band gap of 1.75 eV. This value corresponds to the wavelength in the visible spectrum, suggesting an ideal material for solar cell absorbers. Our study fine tunes the graphane band gap through the foreign atom doping as well as via defect charge state modulation.

  11. Giant Dirac point shift of graphene phototransistors by doped silicon substrate current

    Directory of Open Access Journals (Sweden)

    Masaaki Shimatani

    2016-03-01

    Full Text Available Graphene is a promising new material for photodetectors due to its excellent optical properties and high-speed response. However, graphene-based phototransistors have low responsivity due to the weak light absorption of graphene. We have observed a giant Dirac point shift upon white light illumination in graphene-based phototransistors with n-doped Si substrates, but not those with p-doped substrates. The source-drain current and substrate current were investigated with and without illumination for both p-type and n-type Si substrates. The decay time of the drain-source current indicates that the Si substrate, SiO2 layer, and metal electrode comprise a metal-oxide-semiconductor (MOS capacitor due to the presence of defects at the interface between the Si substrate and SiO2 layer. The difference in the diffusion time of the intrinsic major carriers (electrons and the photogenerated electron-hole pairs to the depletion layer delays the application of the gate voltage to the graphene channel. Therefore, the giant Dirac point shift is attributed to the n-type Si substrate current. This phenomenon can be exploited to realize high-performance graphene-based phototransistors.

  12. Simultaneous phase and size control of upconversion nanocrystals through lanthanide doping

    KAUST Repository

    Wang, Feng

    2010-02-25

    Doping is a widely applied technological process in materials science that involves incorporating atoms or ions of appropriate elements into host lattices to yield hybrid materials with desirable properties and functions. For nanocrystalline materials, doping is of fundamental importance in stabilizing a specific crystallographic phase, modifying electronic properties, modulating magnetism as well as tuning emission properties. Here we describe a material system in which doping influences the growth process to give simultaneous control over the crystallographic phase, size and optical emission properties of the resulting nanocrystals. We show that NaYF 4 nanocrystals can be rationally tuned in size (down to ten nanometres), phase (cubic or hexagonal) and upconversion emission colour (green to blue) through use of trivalent lanthanide dopant ions introduced at precisely defined concentrations. We use first-principles calculations to confirm that the influence of lanthanide doping on crystal phase and size arises from a strong dependence on the size and dipole polarizability of the substitutional dopant ion. Our results suggest that the doping-induced structural and size transition, demonstrated here in NaYF 4 upconversion nanocrystals, could be extended to other lanthanide-doped nanocrystal systems for applications ranging from luminescent biological labels to volumetric three-dimensional displays. © 2010 Macmillan Publishers Limited. All rights reserved.

  13. Analytical models of lateral power devices with arbitrary vertical doping profiles in the drift region

    International Nuclear Information System (INIS)

    Hua Ting-Ting; Guo Yu-Feng; Yu Ying; Jian Tong; Yao Jia-Fei; Sheu Gene

    2013-01-01

    By solving the 2D Poisson's equation, analytical models are proposed to calculate the surface potential and electric field distributions of lateral power devices with arbitrary vertical doping profiles. The vertical and the lateral breakdown voltages are formulized to quantify the breakdown characteristic in completely-depleted and partially-depleted cases. A new reduced surface field (RESURF) criterion which can be used in various drift doping profiles is further derived for obtaining the optimal trade-off between the breakdown voltage and the on-resistance. Based on these models and the numerical simulation, the electric field modulation mechanism and the breakdown characteristics of lateral power devices are investigated in detail for the uniform, linear, Gaussian, and some discrete doping profiles along the vertical direction in the drift region. Then, the mentioned vertical doping profiles of these devices with the same geometric parameters are optimized, and the results show that the optimal breakdown voltages and the effective drift doping concentrations of these devices are identical, which are equal to those of the uniform-doped device, respectively. The analytical results of these proposed models are in good agreement with the numerical results and the previous experimental results, confirming the validity of the models presented here. (interdisciplinary physics and related areas of science and technology)

  14. General practitioners knowledge, practice and training requirements in relation to doping in sport.

    Science.gov (United States)

    Woods, C B; Moynihan, A

    2009-01-01

    This study examined General Practitioner's (GP) knowledge, practice and training requirements in relation to doping in sport in Ireland. All 2083 GPs on the Irish College of General Practitioners (ICGP) register received a postal questionnaire, yielding a 37% response rate (N=771, 63% male, average age 46.2 +/- 9SD, range 28-74 years). Results revealed that 14% (112) deemed their knowledge of doping agents to be good or very good, 12% (94) had completed specific training modules in doping or sport, and 24% (183) were connected with a specific sport as a team doctor/advisor. Over one in four (28%: 217) had been consulted for advice on doping in Sport, 33% (256) possessed the current list of prohibited substances, and 25% (190) knew of the Irish Sports Council's drug-testing procedures. The current initiatives to discourage doping in sport were felt to be ineffective, and although 92% (716) indicated that GPs had a role to play in the prevention of doping in sport, only 9% (66) felt adequately trained for such a role. There was overwhelming support for further training among GPs, although the most appropriate method of providing training is complex and requires strategic planning.

  15. Anabolic agents: recent strategies for their detection and protection from inadvertent doping.

    Science.gov (United States)

    Geyer, Hans; Schänzer, Wilhelm; Thevis, Mario

    2014-05-01

    According to the World Anti-Doping Agency (WADA) Prohibited List, anabolic agents consist of exogenous anabolic androgenic steroids (AAS), endogenous AAS and other anabolic agents such as clenbuterol and selective androgen receptor modulators (SARMs). Currently employed strategies for their improved detection include the prolongation of the detection windows for exogenous AAS, non-targeted and indirect analytical approaches for the detection of modified steroids (designer steroids), the athlete's biological passport and isotope ratio mass spectrometry for the detection of the misuse of endogenous AAS, as well as preventive doping research for the detection of SARMs. The recent use of these strategies led to 4-80-fold increases of adverse analytical findings for exogenous AAS, to the detection of the misuse of new designer steroids, to adverse analytical findings of different endogenous AAS and to the first adverse analytical findings of SARMs. The strategies of the antidoping research are not only focused on the development of methods to catch the cheating athlete but also to protect the clean athlete from inadvertent doping. Within the past few years several sources of inadvertent doping with anabolic agents have been identified. Among these are nutritional supplements adulterated with AAS, meat products contaminated with clenbuterol, mycotoxin (zearalenone) contamination leading to zeranol findings, and natural products containing endogenous AAS. The protection strategy consists of further investigations in case of reasonable suspicion of inadvertent doping, publication of the results, education of athletes and development of methods to differentiate between intentional and unintentional doping.

  16. Doping and thrombosis in sports.

    Science.gov (United States)

    Lippi, Giuseppe; Banfi, Giuseppe

    2011-11-01

    Historically, humans have long sought to enhance their "athletic" performance to increase body weight, aggressiveness, mental concentration and physical strength, contextually reducing fatigue, pain, and improving recovery. Although regular training is the mainstay for achieving these targets, the ancillary use of ergogenic aids has become commonplace in all sports. The demarcation between ergogenic aids and doping substances or practices is continuously challenging and mostly based on perceptions regarding the corruption of the fairness of competition and the potential side effects or adverse events arising from the use of otherwise unnecessary ergogenic substances. A kaleidoscope of side effects has been associated with the use of doping agents, including behavioral, skeletal, endocrinologic, metabolic, hemodynamic, and cardiovascular imbalances. Among the various doping substances, the most striking association with thrombotic complications has been reported for androgenic anabolic steroids (i.e., cardiomyopathy, fatal and nonfatal arrhythmias, myocardial infarction [MI], intracardiac thrombosis, stroke, venous thromboembolism [VTE], limb arterial thrombosis, branch retinal vein occlusion, cerebral venous sinus thrombosis) and blood boosting (i.e., VTE and MI, especially for epoetin and analogs). The potential thrombotic complication arising from misuse of other doping agents such as the administration of cortisol, growth hormone, prolactin, cocaine, and platelet-derived preparations is instead speculative or anecdotal at best. The present article provides an overview on the epidemiological association as well as the underlying biochemical and biological mechanisms linking the practice of doping in sports with the development of thrombosis. © Thieme Medical Publishers.

  17. Band structure of graphene modulated by Ti or N dopants and applications in gas sensoring.

    Science.gov (United States)

    Zhang, Hong-Ping; Luo, Xue-Gang; Lin, Xiao-Yan; Zhang, Ya-Ping; Tang, Ping-Ping; Lu, Xiong; Tang, Youhong

    2015-09-01

    The exploration of novel sensors for NO2 detection is particularly important in material and environmental sciences. In this work, the HOMO-LUMO gap of graphene, Ti- or N-doped graphene is investigated by DFT methods. The adsorption of NO2, NO, and O2 on Ti- or N-doped graphene of different sizes is also explored. Results reveal that the interactions between gases (NO2, NO, and O2) and Ti- or N-doped graphenes is not affected by the size of graphene. The doped Ti greatly improves the interactions between gases and graphene whereas the doped N has no effect on those interactions. The HOMO- LUMO gap of Ti-doped graphene can be modulated by adsorption of the gases. The cross effect of the NO and O2 is also investigated, and it is demonstrated that Ti-doped graphene has specific interactions with NO2. Thus, Ti-doped graphene can be a candidate for NO2 sensor materials. Furthermore, doping the graphene with Ti or N improves the sensitivity of the sheets toward NO2, which can be trapped and detected by the intrinsic graphene. Efficient sensors are rationally designed to diversify their applications in environmental science and engineering. Copyright © 2015 Elsevier Inc. All rights reserved.

  18. Potassium doped MWCNTs for hydrogen storage enhancement

    International Nuclear Information System (INIS)

    Adabi Qomi, S.; Gashtasebi, M.; Khoshnevisan, B.

    2012-01-01

    Here we have used potassium doped MWCNTs for enhancement of hydrogen storage process. XRD and SEM images have confirmed the doping of potassium. For studying the storage process a hydrogenic battery set up has been used. In the battery the working electrode has been made of the silver foam deposited by the doped MWCNTs electrophoretically.

  19. Direct Electrical Probing of Periodic Modulation of Zinc-Dopant Distributions in Planar Gallium Arsenide Nanowires.

    Science.gov (United States)

    Choi, Wonsik; Seabron, Eric; Mohseni, Parsian K; Kim, Jeong Dong; Gokus, Tobias; Cernescu, Adrian; Pochet, Pascal; Johnson, Harley T; Wilson, William L; Li, Xiuling

    2017-02-28

    Selective lateral epitaxial (SLE) semiconductor nanowires (NWs), with their perfect in-plane epitaxial alignment, ability to form lateral complex p-n junctions in situ, and compatibility with planar processing, are a distinctive platform for next-generation device development. However, the incorporation and distribution of impurity dopants in these planar NWs via the vapor-liquid-solid growth mechanism remain relatively unexplored. Here, we present a detailed study of SLE planar GaAs NWs containing multiple alternating axial segments doped with Si and Zn impurities by metalorganic chemical vapor deposition. The dopant profile of the lateral multi-p-n junction GaAs NWs was imaged simultaneously with nanowire topography using scanning microwave impedance microscopy and correlated with infrared scattering-type near-field optical microscopy. Our results provide unambiguous evidence that Zn dopants in the periodically twinned and topologically corrugated p-type segments are preferentially segregated at twin plane boundaries, while Si impurity atoms are uniformly distributed within the n-type segments of the NWs. These results are further supported by microwave impedance modulation microscopy. The density functional theory based modeling shows that the presence of Zn dopant atoms reduces the formation energy of these twin planes, and the effect becomes significantly stronger with a slight increase of Zn concentration. This implies that the twin formation is expected to appear when a threshold planar concentration of Zn is achieved, making the onset and twin periodicity dependent on both Zn concentration and nanowire diameter, in perfect agreement with our experimental observations.

  20. Conducting atomic force microscopy studies on doped CulnO2 thin films for resistive memory device applications

    International Nuclear Information System (INIS)

    Mehta, B.R.

    2009-01-01

    Full text: Delafosite thin films have interesting structural, optical and electronic properties due to the highly anisotropic crystal structure and possibility of bipolar conductivity. In this presentation, optical, structural and electrical properties of Sn (n type) and Ca (p type) doped CulnO 2 layers grown by rf magnetron sputtering technique will be discussed. Depending on doping and deposition temperature, these films show nanocolumnar structure with (110) and (006) preferred orientations. The observed decrease in activation energy from 0.9 eV to about 0.10 eV and a large decrease in conductivity from 2.11 x 10 -10 Scm -1 to 1.66 x 10 -1 Scm -1 on Sn doping has been explained due to the change in preferred orientation along with efficient doping. Our results show that crystallite orientation is the most important factor controlling the electrical conduction in delafossite thin films. The anisotropy of electrical conduction along (006) and (110) directions in tin doped samples has been further established using conducting atomic force microscopy (CAFM) measurements. The CAFM measurements shows the presence of nanoconducting region when the current flow direction is aligned along the BO 6 layer and complete absence of conducting regions when the current direction is perpendicular to the film surface. Resistive memory devices based on Sn and Ca doped CulnO 2 films show stable and reproducible 'on' and 'off' states. CAFM measurement on these devices carried out before and after 'forming' show the growth of nanoconducting filaments on the application of a threshold voltage. It is possible to control resistance in the 'on' and 'off' states and magnitude of the forming and switching voltages by controlling the doping concentration and crystallite orientation in CulnO 2 layers

  1. Photoluminescence properties of erbium-doped III-V semiconductors

    Science.gov (United States)

    Culp, Thomas Dudley

    1998-12-01

    high temperature. Additionally, the interaction between Er3+ centers and free carriers was shown to be important to excitation and quenching of the Er-2O center in GaAs. The Er3+ emission was greatly reduced in n-type samples, whereas the emission remained strong in p-type samples. A model based on the results of a two-beam experiment indicated the presence of a strong Auger quenching mechanism involving free electrons.

  2. Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals

    DEFF Research Database (Denmark)

    Scolari, Lara; Gauza, Sebastian; Xianyu, Haiqing

    2009-01-01

    We infiltrate liquid crystals doped with BaTiO3 nanoparticles in a photonic crystal fiber and compare the measured transmission spectrum with the one achieved without dopant. New interesting features, such as frequency modulation response of the device and a transmission spectrum with tunable....... The threshold voltage for doped and undoped liquid crystals in a silica capillary and in a glass cell are also measured as a function of the frequency of the external electric field and the achieved results are compared....

  3. Doping in controlling the type of conductivity in bulk and nanostructured thermoelectric materials

    International Nuclear Information System (INIS)

    Fuks, D.; Komisarchik, G.; Kaller, M.; Gelbstein, Y.

    2016-01-01

    Doping of materials for thermoelectric applications is widely used nowadays to control the type of conductivity. We report the results of ab-initio calculations aimed at developing the consistent scheme for determining the role of impurities that may change the type of conductivity in two attractive thermoelectric classes of materials. It is demonstrated that alloying of TiNiSn with Cu makes the material of n-type, and alloying with Fe leads to p-type conductivity. Similar calculations for PbTe with small amount of Na substituting for Pb leads to p-type conductivity, while Cl substituting for Te makes PbTe an n-type material. It is shown also that for nano-grained materials the n-type conductivity should be observed. The effect of impurities segregating to the grain boundaries in nano-structured PbTe is also discussed. - Highlights: • Bulk and nano-grained TE materials were analyzed by DFT. • The electronic effects on both PbTe and TiNiSn were demonstrated. • The role of impurities on the conductivity type was analyzed. • Interfacial states in nano-grained PbTe affect the conductivity type.

  4. Copper doped borate dosimeters revisited

    Energy Technology Data Exchange (ETDEWEB)

    Alajerami, Y.S.M. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Department of Medical Radiography, Al-Azhar University, Gaza Strip, Palestine (Country Unknown); Hashim, S., E-mail: suhairul@utm.my [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Oncology Treatment Centre, Sultan Ismail Hospital, 81100 Johor Bahru (Malaysia); Ghoshal, S.K. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Bradley, D.A. [Centre for Nuclear and Radiation Physics, Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Mhareb, M. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Saleh, M.A. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); National Atomic Energy Commission (NATEC), Sana' a (Yemen)

    2014-11-15

    We render a panoramic overview on copper (Cu) doped borate dosimeters. Preparing a dosimeter by mixing specific materials with precise weights and methods is a never-ending quest. The recommended composition is highly decisive for accurate estimation of the absorbed dose, prediction of the biological outcome, determination of the treatment dose for radiation therapy and facilitation of personal monitoring. Based on these principles, the proposed dosimeter must cover a series of dosimetric properties to realize the exact results and assessment. The doped borate dosimeters indeed demonstrate attractive thermoluminescence (TL) features. Several dedicated efforts are attempted to improve the luminescence properties by doping various transition metals or rare-earth elements. The Cu ion being one of the preferred activators shows excellent TL properties as revealed via detail comparison with other dosimeters. Two oxide states of Cu (Cu{sup +} and Cu{sup ++}) with reasonable atomic number allow easy interaction with boron network. Interestingly, the intrinsic luminescent centers of borate lattice are in cross linked with that of Cu{sup +} ions. Thus, the activation of borate dosimeter with Cu ions for the enhancement of the TL sensitivity is recognized. These dosimeters reveal similar glow curves as the standard TLD-100 (LiF:Mg,Ti) one irrespective of the use of modifiers and synthesis techniques. They display high sensitivity, low fading, dose response linearity over wide range and practical minimum detectable dose. Furthermore, the effective atomic number being the most beneficial aspect (equivalent to that of human tissue) of borate dosimeters do not show any change due to Cu ion activations. The past development, major challenges, excitement, applications, recent progress and the future promises of Cu doped borate TL dosimeters are highlighted. - Highlights: • The manuscript gives a panoramic overview on copper doped borate dosimeters. • Cu ions activated

  5. Copper doped borate dosimeters revisited

    International Nuclear Information System (INIS)

    Alajerami, Y.S.M.; Hashim, S.; Ghoshal, S.K.; Bradley, D.A.; Mhareb, M.; Saleh, M.A.

    2014-01-01

    We render a panoramic overview on copper (Cu) doped borate dosimeters. Preparing a dosimeter by mixing specific materials with precise weights and methods is a never-ending quest. The recommended composition is highly decisive for accurate estimation of the absorbed dose, prediction of the biological outcome, determination of the treatment dose for radiation therapy and facilitation of personal monitoring. Based on these principles, the proposed dosimeter must cover a series of dosimetric properties to realize the exact results and assessment. The doped borate dosimeters indeed demonstrate attractive thermoluminescence (TL) features. Several dedicated efforts are attempted to improve the luminescence properties by doping various transition metals or rare-earth elements. The Cu ion being one of the preferred activators shows excellent TL properties as revealed via detail comparison with other dosimeters. Two oxide states of Cu (Cu + and Cu ++ ) with reasonable atomic number allow easy interaction with boron network. Interestingly, the intrinsic luminescent centers of borate lattice are in cross linked with that of Cu + ions. Thus, the activation of borate dosimeter with Cu ions for the enhancement of the TL sensitivity is recognized. These dosimeters reveal similar glow curves as the standard TLD-100 (LiF:Mg,Ti) one irrespective of the use of modifiers and synthesis techniques. They display high sensitivity, low fading, dose response linearity over wide range and practical minimum detectable dose. Furthermore, the effective atomic number being the most beneficial aspect (equivalent to that of human tissue) of borate dosimeters do not show any change due to Cu ion activations. The past development, major challenges, excitement, applications, recent progress and the future promises of Cu doped borate TL dosimeters are highlighted. - Highlights: • The manuscript gives a panoramic overview on copper doped borate dosimeters. • Cu ions activated technique in borate

  6. Module descriptor

    DEFF Research Database (Denmark)

    Vincenti, Gordon; Klausen, Bodil; Kjær Jensen, Jesper

    2016-01-01

    The Module Descriptor including a Teacher’s Guide explains and describes how to work innovatively and co-creatively with wicked problems and young people. The descriptor shows how interested educators and lecturers in Europe can copy the lessons of the Erasmus+ project HIP when teaching their own...

  7. Memory Modulation

    NARCIS (Netherlands)

    Roozendaal, Benno; McGaugh, James L.

    2011-01-01

    Our memories are not all created equally strong: Some experiences are well remembered while others are remembered poorly, if at all. Research on memory modulation investigates the neurobiological processes and systems that contribute to such differences in the strength of our memories. Extensive

  8. Visualization of carrier dynamics in p(n)-type GaAs by scanning ultrafast electron microscopy.

    Science.gov (United States)

    Cho, Jongweon; Hwang, Taek Yong; Zewail, Ahmed H

    2014-02-11

    Four-dimensional scanning ultrafast electron microscopy is used to investigate doping- and carrier-concentration-dependent ultrafast carrier dynamics of the in situ cleaved single-crystalline GaAs(110) substrates. We observed marked changes in the measured time-resolved secondary electrons depending on the induced alterations in the electronic structure. The enhancement of secondary electrons at positive times, when the electron pulse follows the optical pulse, is primarily due to an energy gain involving the photoexcited charge carriers that are transiently populated in the conduction band and further promoted by the electron pulse, consistent with a band structure that is dependent on chemical doping and carrier concentration. When electrons undergo sufficient energy loss on their journey to the surface, dark contrast becomes dominant in the image. At negative times, however, when the electron pulse precedes the optical pulse (electron impact), the dynamical behavior of carriers manifests itself in a dark contrast which indicates the suppression of secondary electrons upon the arrival of the optical pulse. In this case, the loss of energy of material's electrons is by collisions with the excited carriers. These results for carrier dynamics in GaAs(110) suggest strong carrier-carrier scatterings which are mirrored in the energy of material's secondary electrons during their migration to the surface. The approach presented here provides a fundamental understanding of materials probed by four-dimensional scanning ultrafast electron microscopy, and offers possibilities for use of this imaging technique in the study of ultrafast charge carrier dynamics in heterogeneously patterned micro- and nanostructured material surfaces and interfaces.

  9. Nonlinear absorption coefficient and relative refraction index change for an asymmetrical double δ-doped quantum well in GaAs with a Schottky barrier potential

    Energy Technology Data Exchange (ETDEWEB)

    Rojas-Briseño, J.G.; Martínez-Orozco, J.C.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esquina con Paseo la Bufa S/N, C.P. 98060, Zacatecas, Zac. (Mexico); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Instituto de Física, Universidad de Antioquia, AA 1226, Medellín (Colombia); Duque, C.A., E-mail: cduque@fisica.udea.edu.co [Instituto de Física, Universidad de Antioquia, AA 1226, Medellín (Colombia)

    2013-09-01

    In this work we are reporting the energy level spectrum for a quantum system consisting of an n-type double δ-doped quantum well with a Schottky barrier potential in a Gallium Arsenide matrix. The calculated states are taken as the basis for the evaluation of the linear and third-order nonlinear contributions to the optical absorption coefficient and to the relative refractive index change, making particular use of the asymmetry of the potential profile. These optical properties are then reported as a function of the Schottky barrier height (SBH) and the separation distance between the δ-doped quantum wells. Also, the effects of the application of hydrostatic pressure are studied. The results show that the amplitudes of the resonant peaks are of the same order of magnitude of those obtained in the case of single δ-doped field effect transistors; but tailoring the asymmetry of the confining potential profile allows the control the resonant peak positions.

  10. A study of the effect of gamma radiation and doping on the catalytic activity of some oxides in the decomposition of hydrogen per-oxide

    International Nuclear Information System (INIS)

    Mousa, M.A.

    1987-01-01

    The rates of hydrogen peroxide decomposition on pure, doped and gamma-irradiated oxides Chromium oxide, Cobalt oxide, Magnesium oxide Nickel oxide, Ferric oxide, Magnesium ferri oxide were measured in a temperature range of 25-40 degree centigrade. It was found that lattice defect induced by doping and gamma-irradiation affect the catalytic properties of the oxides, either by activation or deactivation. The correlation between the catalytic activity for the hydrogen peroxide decomposition and the electronic defects produced by doping and by gamma-irradiation in the oxides is dicussed. Generally, it was found that the p-type semiconductor oxides are more active towards hydrogen peroxide decomposition than the n-type semiconductor oxides. (orig./A.B.)

  11. Effect of N/B doping on the electronic and field emission properties for carbon nanotubes, carbon nanocones, and graphene nanoribbons.

    Science.gov (United States)

    Yu, Shan-Sheng; Zheng, Wei-Tao

    2010-07-01

    Carbon nanotubes, carbon nanocones, and graphene nanoribbons are carbon-based nanomaterials, and their electronic and field emission properties can be altered by either electron donors or electron acceptors. Among both donors and accepters, nitrogen and boron atoms are typical substitutional dopants for carbon materials. The contribution of this paper mainly provides a comprehensive overview of the theoretical topics. The effect of nitrogen/boron doping on the electronic and field emission properties for carbon nanotubes, carbon nanocones, and graphene nanoribbons is reviewed. It is also suggested that nitrogen is more an n-type donor. The discussion about the mechanism of field emission for N-doped carbon nanotubes and electronic structures of N-doped graphene nanoribbons is interesting and timely.

  12. Study on the adsorption properties of O3, SO2, and SO3 on B-doped graphene using DFT calculations

    International Nuclear Information System (INIS)

    Rad, Ali Shokuhi; Shabestari, Sahand Sadeghi; Mohseni, Soheil; Aghouzi, Samaneh Alijantabar

    2016-01-01

    We investigated the structure, adsorption, electronic states, and charge transfer of O 3 , SO 2 and SO 3 molecules on the surface of a B-doped graphene using density functional theory (DFT). We found weak physisorption of SO 2 (−10.9 kJ/mole, using B3LYP-D) and SO 3 (−15.7 kJ/mole, using B3LYP-D) on the surface of B-doped graphene while there is strong chemisorption for O 3 (−96.3 kJ/mole, using B3LYP-D ) on this surface. Our results suggest the potential of B-doped graphene as a selective sensor/adsorbent for O 3 molecule. We noticed some change in hybridizing of boron from sp 2 to sp 3 upon adsorption of O 3 which cases transformation of the adsorbent from 2D to 3D. - Graphical abstract: The electronic property of B-doped graphene is responsible to highly adsorption of O 3 molecules while the adsorption of SO 2 and SO 3 molecules on this surface exhibits only a weak interaction. - Highlights: • B-doped graphene clearly is n-type semiconductor. • High negatively charge of C-atoms neighboring the boron dopant. • Chemisorption of O 3 and physisorption of SO 2 and SO 3 on the surface of B-doped graphene.

  13. Phosphorous Doping of Nanostructured Crystalline Silicon

    DEFF Research Database (Denmark)

    Plakhotnyuk, Maksym; Davidsen, Rasmus Schmidt; Steckel, André

    surface aspect ration (22.25) of bSi to planar surface doping concentration might be slightly higher than on planar surfaces. Therefore, we conducted a study and present recent results of doping of bSi and compared their properties to planar Si. We doped planar, KOH-etched random pyramid and bSi surfaces...... with phosphorous (POCl3) in the temperature range 850-1000oC for 15 and 20 min, respectively. Sheet resistance measurements show slight differences in doping density between planar, KOH pyramidal and bSi structures. bSi samples have lower sheet resistance, pointing to higher doping density presumably due...

  14. Defect mediated reversible ferromagnetism in Co and Mn doped zinc oxide epitaxial films

    Energy Technology Data Exchange (ETDEWEB)

    Mal, Siddhartha; Nori, Sudhakar; Narayan, J. [Department of Material Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Mula, Suhrit [Department of Material Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Department of Metallurgical and Materials Engineering, National Institute of Technology, Rourkela 769008 (India); Prater, J. T. [Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709 (United States)

    2012-12-01

    We have introduced defects in ZnO (undoped and doped with Co and Mn) epitaxial thin films using laser irradiation from nanosecond laser pulses and thermal annealing in oxygen ambient. In contrast to the as grown samples, the laser irradiated films show a significant increase in conductivity, enhancement in UV emission, while maintaining the same wurtzite crystal structure. Room-temperature ferromagnetism (RTFM) is observed in laser-irradiated samples, which increased with the number of laser pulses up to a certain value where magnetic moment saturates. The induced ferromagnetism as well as the enhanced electrical conductivity can be reversed with thermal annealing in oxygen ambient. The magnetization in Co and Mn doped films was found to be strong function of growth conditions and defect concentration. X-ray diffraction and optical absorption experiments suggested a 2+ valance state and tetrahedral coordination for both Co and Mn ions. There is a simultaneous increase in n-type electrical conductivity with the number of laser pulses and continue to exhibit semiconducting behavior in both undoped and doped films. The saturation magnetization was found to be 0.08 {mu}{sub B}/Co and 0.05 {mu}{sub B}/Mn, much lower than 3.0 {mu}{sub B}/Co and 5.0 {mu}{sub B}/Mn, indicating the prominent role of intrinsic defects in RTFM with some contribution from Co{sup 2+}-oxygen vacancy complexes. We propose a unified mechanism based upon introduction of intrinsic defects to explain RTFM and n-type conductivity enhancements during pulsed laser and thermal annealing.

  15. DOPING IN SPORT: GLOBAL ETHICAL ISSUES

    Directory of Open Access Journals (Sweden)

    Angela J. Schneider

    2007-09-01

    Full Text Available DESCRIPTION In this book the question of "How ethical is using performance improving drugs in sport?" is argued in global perspective. PURPOSE The ethical questions in sport are discussed comprehensively. Particularly, different cultures and approach of various countries to that issue were examined. FEATURES The book composed of 10 chapters following a thorough introduction from the editors in 194 pages. The titles are: 1.Fair is Fair, Or Is It? : A Moral Consideration of the Doping Wars in American Sport; 2.Are Doping Sanctions Justified? A Moral Relativistic View; 3.Cultural Nuances: Doping, Cycling and the Tour de France; 4.On Transgendered Athletes, Fairness and Doping: An International Challenge; 5.Creating a Corporate Anti-doping Culture: The Role of Bulgarian Sports Governing Bodies; 6. Doping in the UK: Alain and Dwain, Rio and Greg - Not Guilty?; 7.The Japanese Debate Surrounding the Doping Ban: The Application of the Harm Principle; 8. Doping and Anti-doping in Sport in China: An Analysis of Recent and Present Attitudes and Actions; 9.Anti-doping in Sport: The Norwegian Perspective; 10.Ethics in Sport: The Greek Educational Perspective on Anti-doping. AUDIENCE Given that this book is about a popular topic in sport, it is a great interest to the sport public as well as students, researchers and practitioners in the sport and exercise disciplines.

  16. Synthesis and characterization of n-type NiO:Al thin films for fabrication of p-n NiO homojunctions

    Science.gov (United States)

    Sun, Hui; Liao, Ming-Han; Chen, Sheng-Chi; Li, Zhi-Yue; Lin, Po-Chun; Song, Shu-Mei

    2018-03-01

    n-type NiO:Al thin films were deposited by RF magnetron sputtering. Their optoelectronic properties versus Al target power was investigated. The results show that with increasing Al target power, the conduction type of NiO films changes from p-type to n-type. The variation of the film’s electrical and optical properties depends on Al amount in the film. When Al target power is relatively low, Al3+ cations tend to enter nickel vacancy sites, which makes the lattice structure of NiO more complete. This improves the carrier mobility and film’s transmittance. However, when Al target power exceeds 40 W, Al atoms begin to enter into interstitial sites and form an Al cluster in the NiO film. This behavior is beneficial for improving the film’s n-type conductivity but degrades the film’s transmittance. Finally, Al/(p-type NiO)/(n-type NiO:Al)/ITO homojunctions were fabricated. Their performance was compared with Al/(p-type NiO)/ITO heterojunctions without an n-type NiO layer. Thanks to the better interface quality between the two NiO layers, the homojunctions present better performance.

  17. Regulating Charge and Exciton Distribution in High-Performance Hybrid White Organic Light-Emitting Diodes with n-Type Interlayer Switch

    Science.gov (United States)

    Luo, Dongxiang; Yang, Yanfeng; Xiao, Ye; Zhao, Yu; Yang, Yibin; Liu, Baiquan

    2017-10-01

    The interlayer (IL) plays a vital role in hybrid white organic light-emitting diodes (WOLEDs); however, only a negligible amount of attention has been given to n-type ILs. Herein, the n-type IL, for the first time, has been demonstrated to achieve a high efficiency, high color rendering index (CRI), and low voltage trade-off. The device exhibits a maximum total efficiency of 41.5 lm W-1, the highest among hybrid WOLEDs with n-type ILs. In addition, high CRIs (80-88) at practical luminances (≥1000 cd m-2) have been obtained, satisfying the demand for indoor lighting. Remarkably, a CRI of 88 is the highest among hybrid WOLEDs. Moreover, the device exhibits low voltages, with a turn-on voltage of only 2.5 V (>1 cd m-2), which is the lowest among hybrid WOLEDs. The intrinsic working mechanism of the device has also been explored; in particular, the role of n-type ILs in regulating the distribution of charges and excitons has been unveiled. The findings demonstrate that the introduction of n-type ILs is effective in developing high-performance hybrid WOLEDs. [Figure not available: see fulltext.

  18. Heat-Electric Power Conversion Without Temperature Difference Using Only n-Type Ba8Au x Si46-x Clathrate with Au Compositional Gradient

    Science.gov (United States)

    Osakabe, Yuki; Tatsumi, Shota; Kotsubo, Yuichi; Iwanaga, Junpei; Yamasoto, Keita; Munetoh, Shinji; Furukimi, Osamu; Nakashima, Kunihiko

    2018-02-01

    Thermoelectric power generation is typically based on the Seebeck effect under a temperature gradient. However, the heat flux generated by the temperature difference results in low conversion efficiency. Recently, we developed a heat-electric power conversion mechanism using a material consisting of a wide-bandgap n-type semiconductor, a narrow-bandgap intrinsic semiconductor, and a wide-bandgap p-type semiconductor. In this paper, we propose a heat-electric power conversion mechanism in the absence of a temperature difference using only n-type Ba8Au x Si46-x clathrate. Single-crystal Ba8Au x Si46-x clathrate with a Au compositional gradient was synthesized by Czochralski method. Based on the results of wavelength-dispersive x-ray spectroscopy and Seebeck coefficient measurements, the presence of a Au compositional gradient in the sample was confirmed. It also observed that the electrical properties changed gradually from wide-bandgap n-type to narrow-bandgap n-type. When the sample was heated in the absence of a temperature difference, the voltage generated was approximately 0.28 mV at 500°C. These results suggest that only an n-type semiconductor with a controlled bandgap can generate electric power in the absence of a temperature difference.

  19. The annealing of interstitial carbon atoms in high-resistivity n-type silicon after proton irradiation

    CERN Document Server

    Kuhnke, M; Lindström, G

    2002-01-01

    The annealing of interstitial carbon C sub i after 7-10 MeV and 23 GeV proton irradiations at room temperature in high-resistivity n-type silicon is investigated. Deep level transient spectroscopy is used to determine the defect parameters. The annealing characteristics of the impurity defects C sub i , C sub i C sub s , C sub i O sub i and VO sub i suggest that the mobile C sub i atoms are also captured at divacancy VV sites at the cluster peripheries and not only at C sub s and O sub i sites in the silicon bulk. The deviation of the electrical filling characteristic of C sub i from the characteristic of a homogeneously distributed defect can be explained by an aggregation of C sub i atoms in the environment of the clusters. The capture rate of electrons into defects located in the cluster environment is reduced due to a positive space charge region surrounding the negatively charged cluster core. The optical filling characteristic of C sub i suggests that the change of the triangle-shaped electric field dis...

  20. Conduction band mass determinations for n-type InGaAs/InAlAs single quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Jones, E.D.; Reno, J.L. [Sandia National Labs., Albuquerque, NM (United States); Kotera, Nobuo [Kyushu Inst. of Tech., Iizuka, Fukuoka (Japan); Wang, Y. [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab.

    1998-05-01

    The authors report the measurement of the conduction band mass in n-type single 27-ML-wide InGaAs/InAlAs quantum well lattice matched to InP using two methods: (1) Magnetoluminescence spectroscopy and (2) far-infrared cyclotron resonance. The magnetoluminescence method utilizes Landau level transitions between 0 and 14 T at 1.4 K. The far infrared cyclotron resonance measurements were made at 4.2 K and to fields as large up to 18 T. The 2D-carrier density N{sub 2D} = 3 {times} 10{sup 11} cm{sup {minus}2} at low temperatures. The magnetoluminescence technique yielded an effective conduction-band mass of m{sub c} = 0.062m{sub 0} while the far infrared cyclotron resonance measurements gave m{sub c} = 0.056m{sub 0}, where m{sub 0} is the free electron mass. Both measurements show no evidence for any significant conduction-band nonparabolicity.

  1. Stability of alloyed and nonalloyed ohmic contacts to n-type GaN at high temperature in air

    Science.gov (United States)

    Zhao, Shirong; Gao, Jianyi; Wang, Shuo; Xie, Hongen; Ponce, Fernando A.; Goodnick, Stephen; Chowdhury, Srabanti

    2017-12-01

    We report on the high-temperature characteristics and stability of both alloyed Ti/Al/Ni/Au ohmic contacts and nonalloyed Al/Au ohmic contacts to n-type GaN at temperatures up to 600 °C in air. The alloyed contacts showed a specific contact resistivity (ρc) of 6.8 × 10‑6 Ω cm2 at room temperature after fabrication. ρc did not change with temperature or show degradation after the application of thermal stress at 600 °C for 4 h in air. The ρc of nonalloyed contacts was reduced by two orders of magnitude and stabilized to 5 × 10‑6 Ω cm2 after the application of high-temperature thermal stress. Transmission electron microscopy, scanning transmission electron microscopy, and electron energy loss spectroscopy were used to analyze the metal–semiconductor interface to understand the formation of the low-resistivity and high-stability ohmic contacts at high temperature. Our study reveals the high stability of both alloyed and nonalloyed ohmic contacts for GaN-based electronic devices operating at high temperatures in air.

  2. Band alignment at organic-inorganic heterojunctions between P3HT and n-type 6H-SiC.

    Science.gov (United States)

    Dietmueller, Roland; Nesswetter, Helmut; Schoell, Sebastian J; Sharp, Ian D; Stutzmann, Martin

    2011-11-01

    The exact band alignment at organic/inorganic semiconductor heterojunctions is influenced by a variety of properties and is difficult to predict. For organic/inorganic bilayer heterojunctions made of poly(3-hexylthiophene) (P3HT) and n-type 6H-SiC, the band alignment is determined via current-voltage measurements. For this purpose, a model equivalent circuit, combining thermionic emission and space-charge-limited current effects, is proposed which describes the behavior of the heterojunction very well. From the fitting parameters, an interface barrier height of 1.1 eV between the lowest unoccupied molecular orbital (LUMO) of P3HT and the conduction band (CB) of 6H-SiC is determined. In addition, from the maximum open circuit voltage of 6H-SiC/P3HT diodes, a difference of 0.9 eV between the highest occupied molecular orbital (HOMO) of P3HT and the CB of 6H-SiC is deduced. These two values determine the alignment of the energy bands of 6H-SiC relative to the HOMO and LUMO of P3HT. The 6H-SiC/P3HT bilayer heterojunction exhibits an open circuit voltage of ~0.5 V at room temperature, which makes such a materials system a potential candidate for bulk heterojunction hybrid solar cells with 6H-SiC nanoparticles.

  3. Study of various n-type organic semiconductors on ultraviolet detective and electroluminescent properties of optoelectronic integrated device

    Science.gov (United States)

    Deng, Chaoxu; Shao, Bingyao; Zhao, Dan; Zhou, Dianli; Yu, Junsheng

    2017-11-01

    Organic optoelectronic integrated device (OID) with both ultraviolet (UV) detective and electroluminescent (EL) properties was fabricated by using a thermally activated delayed fluorescence (TADF) semiconductor of (4s, 6s)-2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN) as an emitter. The effect of five kinds of n-type organic semiconductors (OSCs) on the enhancement of UV detective and EL properties of OID was systematically studied. The result shows that two orders of magnitude in UV detectivity from 109 to 1011 Jones and 3.3 folds of luminance from 2499 to 8233 cd m‑2 could be achieved. The result shows that not only the difference of lowest unoccupied molecular orbital (LUMO) between active layer and OSC but also the variety of electron mobility have a significant effect on the UV detective and EL performance through adjusting electron injection/transport. Additionally, the optimized OSC thickness is beneficial to confine the leaking of holes from the active layer to cathode, leading to the decrease of dark current for high detective performance. This work provides a useful method on broadening OSC material selection and device architecture construction for the realization of high performance OID.

  4. The determination of electronic and interface state density distributions of Au/n-type GaAs Schottky barrier diodes

    Energy Technology Data Exchange (ETDEWEB)

    Karatas, S. [Faculty of Sciences and Arts, Department of Physics, University of Kahramanmaras Suetcue Imam, 46100 Kahramanmaras (Turkey)]. E-mail: skaratas@ksu.edu.tr; Tueruet, A. [Faculty of Sciences and Arts, Department of Physics, Atatuerk University, 25240 Erzurum (Turkey)

    2006-05-31

    The electronic and interface state density distribution properties obtained from current-voltage (I-V) and capacitance-voltage (C-V) characteristics of Au/n-type GaAs Schottky barrier diode (SBD) at room temperature was investigated. SBD parameters such as ideality factor (n), series resistance (R {sub S}) and barrier height ({phi}{sub IV} ) were obtained from I-V and C-V measurements using Cheung's method. The diode parameters such as ideality factor, series resistance and barrier heights were found as 1.51-1.78, 7.597-8.167 {omega} and 0.88-1.14 eV, respectively. The diode shows non-ideal I-V behaviour with an ideality factor greater than unity. Furthermore, the energy distribution of interface state density was determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height. The results show the presence of thin interfacial layer between the metal and semiconductor.

  5. Electron mobilities of n-type organic semiconductors from time-dependent wavepacket diffusion method: pentacenequinone derivatives.

    Science.gov (United States)

    Zhang, WeiWei; Zhong, XinXin; Zhao, Yi

    2012-11-26

    The electron mobilities of two n-type pentacenequinone derivative organic semiconductors, 5,7,12,14-tetraaza-6,13-pentacenequinone (TAPQ5) and 1,4,8,11-tetraaza-6,13-pentacenequinone (TAPQ7), are investigated with use of the methods of electronic structure and quantum dynamics. The electronic structure calculations reveal that the two key parameters for the control of electron transfer, reorganization energy and electronic coupling, are similar for these two isomerization systems, and the charge carriers essentially display one-dimensional transport properties. The mobilities are then calculated by using the time-dependent wavepacket diffusion approach in which the dynamic fluctuations of the electronic couplings are incorporated via their correlation functions obtained from molecular dynamics simulations. The predicted mobility of TAPQ7 crystal is about six times larger than that of TAPQ5 crystal. Most interestingly, Fermi's golden rule predicts the mobilities very close to those from the time-dependent wavepacket diffusion method, even though the electronic couplings are explicitly large enough to make the perturbation theory invalid. The possible reason is analyzed from the dynamic fluctuations.

  6. Properties of n-type SnO2 semiconductor prepared by spray ultrasonic technique for photovoltaic applications

    Science.gov (United States)

    Bendjedidi, H.; Attaf, A.; Saidi, H.; Aida, M. S.; Semmari, S.; Bouhdjar, A.; Benkhetta, Y.

    2015-12-01

    Transparent conducting n-type SnO2 semiconductor films were fabricated by employing an inexpensive, simplified spray ultrasonic technique using an ultrasonic generator at deferent substrate temperatures (300, 350, 400, 450 and 500 °C). The structural studies reveal that the SnO2 films are polycrystalline at 350, 400, 450, 500 °C with preferential orientation along the (200) and (101) planes, and amorphous at 300 °C. The crystallite size of the films was found to be in the range of 20.9-72.2 nm. The optical transmittance in the visible range and the optical band gap are 80% and 3.9 eV respectively. The films thicknesses were varied between 466 and 1840 nm. The resistivity was found between 1.6 and 4 × 10-2 Ω·cm. This simplified ultrasonic spray technique may be considered as a promising alternative to a conventional spray for the massive production of economic SnO2 films for solar cells, sensors and opto-electronic applications.

  7. Drastic Control of Texture in a High Performance n-Type Polymeric Semiconductor and Implications for Charge Transport

    KAUST Repository

    Rivnay, Jonathan

    2011-07-12

    Control of crystallographic texture from mostly face-on to edge-on is observed for the film morphology of the n-type semicrystalline polymer {[N,N-9-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl] -alt-5,59-(2,29-bithiophene)}, P(NDI2OD-T2), when annealing the film to the polymer melting point followed by slow cooling to ambient temperature. A variety of X-ray diffraction analyses, including pole figure construction and Fourier transform peak shape deconvolution, are employed to quantify the texture change, relative degree of crystallinity and lattice order. We find that annealing the polymer film to the melt leads to a shift from 77.5% face-on to 94.6% edge-on lamellar texture as well as to a 2-fold increase in crystallinity and a 40% decrease in intracrystallite cumulative disorder. The texture change results in a significant drop in the electron-only diode current density through the film thickness upon melt annealing, while little change is observed in the in-plane transport of bottom gated thin film transistors. This suggests that the texture change is prevalent in the film interior and that either the (bottom) surface structure is different from the interior structure or the intracrystalline order and texture play a secondary role in transistor transport for this material. © 2011 American Chemical Society.

  8. Effects of the L/N-type calcium channel antagonist cilnidipine on morning blood pressure control and peripheral edema formation.

    Science.gov (United States)

    Narita, Sumito; Yoshioka, Yasuko; Ide, Atsumi; Kadokami, Toshiaki; Momii, Hidetoshi; Yoshida, Masayoshi; Ando, Shin-ichi

    2011-01-01

    The L/N-type calcium channel blocker cilnidipine has unique effects including sympathetic nerve suppression and the balanced vasodilatation of arteries and veins that may alleviate morning hypertension (MHT) or peripheral edema caused by calcium channel antagonists. We used ambulatory blood pressure monitoring (ABPM) and a unique peripheral edema measurement to evaluate the effect of morning and bedtime cilnidipine in patients with MHT. Forty-three patients with MHT (60 ± 12 years) were randomly assigned to a morning or bedtime cilnidipine (10-20 mg/day). MHT was defined as a mean systolic blood pressure (SBP) ≥ 135 mm Hg by ABPM within 2 hours after awaking. After 3 months, greater SBP reductions were observed in the bedtime administration group (versus the morning administration group) at 3:30-6:00 AM (-24 ± 20 mm Hg vs. -10 ± 4 mm Hg; P < .05) and at 6:30-9:00 AM (-26 ± 15 mm Hg vs. -14 ± 17 mm Hg; P < .05). Although physical examinations showed leg edema in 16% of the patients, quantitative evaluations did not reveal significant volume gains. Cilnidipine had a greater effect on MHT, without causing significant leg edema, when administered at bedtime. Copyright © 2011 American Society of Hypertension. Published by Elsevier Inc. All rights reserved.

  9. The Role of the Side Chain on the Performance of N-type Conjugated Polymers in Aqueous Electrolytes

    KAUST Repository

    Giovannitti, Alexander

    2018-04-24

    We report a design strategy that allows the preparation of solution processable n-type materials from low boiling point solvents for organic electrochemical transistors (OECTs). The polymer backbone is based on NDI-T2 copolymers where a branched alkyl side chain is gradually exchanged for a linear ethylene glycol-based side chain. A series of random copolymers was prepared with glycol side chain percentages of 0, 10, 25, 50, 75, 90, and 100 with respect to the alkyl side chains. These were characterized to study the influence of the polar side chains on interaction with aqueous electrolytes, their electrochemical redox reactions, and performance in OECTs when operated in aqueous electrolytes. We observed that glycol side chain percentages of >50% are required to achieve volumetric charging, while lower glycol chain percentages show a mixed operation with high required voltages to allow for bulk charging of the organic semiconductor. A strong dependence of the electron mobility on the fraction of glycol chains was found for copolymers based on NDI-T2, with a significant drop as alkyl side chains are replaced by glycol side chains.

  10. Impurity doping processes in silicon

    CERN Document Server

    Wang, FFY

    1981-01-01

    This book introduces to non-experts several important processes of impurity doping in silicon and goes on to discuss the methods of determination of the concentration of dopants in silicon. The conventional method used is the discussion process, but, since it has been sufficiently covered in many texts, this work describes the double-diffusion method.

  11. Steroid profiling in doping analysis

    NARCIS (Netherlands)

    Kerkhof, Daniël Henri van de

    2001-01-01

    Profiling androgens in urine samples is used in doping analysis for the detection of abused steroids of endogenous origin. These profiling techniques were originally developed for the analysis of testosterone, mostly by means of the ratio of testosterone to epitestosterone (T/E ratio). A study was

  12. Characterization of selective reactive ion etching effects on delta-doped GaAs/AlGaAs MODFET layers

    Science.gov (United States)

    Agarwala, S.; Tong, M.; Ballegeer, D. G.; Nummila, K.; Ketterson, A. A.; Adesida, I.

    1993-04-01

    The effects of selective reactive ion etching (SRIE) using SiCl4/SiF4 plasma on delta-doped GaAs/Al0.3Ga0.7As modulation-doped field-effect transistor (MODFET) structures and devices have been investigated. The results are compared with those of corresponding conventionally doped MODFETs. Hall measurements were conducted at 300 and 77 K to characterize the change in the transport properties of the two-dimensional electron gas due to low energy ion bombardment during the SRIE process. Delta-doped structures showed a smaller change in sheet carrier density and mobility compared to conventionally doped structures. Direct current and high frequency measurements were performed on the SRIE gate-recessed MODFETs. No significant change in threshold voltage was observed for the delta-doped MODFETs in contrast to an increase of about 300 mV for the conventionally doped MODFETs processed at a plasma self-bias voltage of -90 V and a 1200% overetch time. Maximum dc extrinsic transconductance and unity current gain cutoff frequency did not change with SRIE processing for either of the structures.

  13. p and n-type germanium layers grown using iso-butyl germane in a III-V metal-organic vapor phase epitaxy reactor

    International Nuclear Information System (INIS)

    Jakomin, Roberto; Beaudoin, Gregoire; Gogneau, Noelle; Lamare, Bruno; Largeau, Ludovic; Mauguin, Olivia; Sagnes, Isabelle

    2011-01-01

    We report on the growth of n- and p-doped Germanium (Ge) on Ge substrates by Metal-Organic Vapor Phase Epitaxy (MOVPE). Iso-butyl germane, a liquid metal-organic source less toxic than Germane, is used as Ge precursor. We demonstrate the p-doping of Germanium by MOVPE using Trimethylgallium. The influence of the growth parameters for n and p-type doping is studied in order to optimize the morphology, the structural and the electrical properties of the Ge layers. The controlled growth of p and n doped Ge layers opens the possibility to realize totally epitaxially grown Ge diodes with improved performances, for example, for solar cell applications.

  14. Irradiation effects with 100 MeV Xe ions on optical properties of Al-doped ZnO films

    International Nuclear Information System (INIS)

    Fukuoka, O.; Matsunami, N.; Tazawa, M.; Shimura, T.; Sataka, M.; Sugai, H.; Okayasu, S.

    2006-01-01

    Al-doped ZnO (AZO) films are known as n-type transparent semiconductors. We have investigated the effects of 100 MeV Xe ion irradiation on the optical and structural properties of AZO films, which were prepared on SiO 2 glass at 400 deg. C by using a RF-magnetron sputtering deposition method. We discuss relationships between these property modifications and the recent observations of the conductivity increase by ion irradiation. It is suggested that the band-gap modification has more close relation with the conductivity increase than the structural modification

  15. Structural "δ Doping" to Control Local Magnetization in Isovalent Oxide Heterostructures

    Science.gov (United States)

    Moon, E. J.; He, Q.; Ghosh, S.; Kirby, B. J.; Pantelides, S. T.; Borisevich, A. Y.; May, S. J.

    2017-11-01

    Modulation and δ -doping strategies, in which atomically thin layers of charged dopants are precisely deposited within a heterostructure, have played enabling roles in the discovery of new physical behavior in electronic materials. Here, we demonstrate a purely structural "δ -doping" strategy in complex oxide heterostructures, in which atomically thin manganite layers are inserted into an isovalent manganite host, thereby modifying the local rotations of corner-connected MnO6 octahedra. Combining scanning transmission electron microscopy, polarized neutron reflectometry, and density functional theory, we reveal how local magnetic exchange interactions are enhanced within the spatially confined regions of suppressed octahedral rotations. The combined experimental and theoretical results illustrate the potential to utilize noncharge-based approaches to "doping" in order to enhance or suppress functional properties within spatially confined regions of oxide heterostructures.

  16. Fiber Bragg grating inscription in pure-silica and Ge-doped photonic crystal fibers.

    Science.gov (United States)

    Wang, Yiping; Bartelt, Hartmut; Becker, Martin; Brueckner, Sven; Bergmann, Joachim; Kobelke, Jens; Rothhardt, Manfred

    2009-04-10

    We report on fiber Bragg gratings (FBGs) inscribed in pure-silica and Ge-doped photonic crystal fibers (PCFs) with a two-beam interference technique and a femtosecond or excimer laser. Such a technique enables the inscription of FBGs for different Bragg wavelengths with high flexibility. Effects of H(2)-loading and Ge doping on the efficiency of grating inscription were investigated by measuring the development of Bragg wavelength and attenuation in the transmission spectra with an increased exposure dose. H(2)-loading dramatically enhances the laser-induced index modulation not only in Ge-doped PCFs but also in pure-silica PCFs. We observed a reversible Bragg wavelength shift during femtosecond pulse irradiation, which indicates an internal temperature rise of approximately 77 degrees C.

  17. A reconfigurable silicon-on-insulator diode with tunable electrostatic doping

    Science.gov (United States)

    Cristoloveanu, Sorin; Lee, Kyung Hwa; Bawedin, Maryline

    2017-08-01

    P-N diodes can be emulated in ultrathin, fully depleted Silicon-On-Insulator films by appropriately biasing the front and back gates. Adjacent electron and hole populations form a virtual P-N junction. Systematic current-voltage I-V characteristics are presented revealing similarities and major differences with those of conventional P-N diodes with ion-implanted doping. The lateral electric field from the anode combines with the gate-induced vertical field and leads to unusual two-dimensional effects. A distinct merit of the virtual diode is the possibility to adjust the concentrations of electrostatic doping via the gates. The reverse current, forward current, and depletion depth become gate-controlled. Our experiments show that by modifying the type, N or P, of electrostatic doping, the virtual diode can be reconfigured in 8 other devices: semi-virtual diodes, PIN diodes, tunneling field-effect transistors or band-modulation FET.

  18. Structural Comparison of n-type and p-type LaAlO3/SrTiO3 Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bell, Christopher

    2011-08-19

    Using a surface x-ray diffraction technique, we investigated the atomic structure of two types of interfaces between LaAlO{sub 3} and SrTiO{sub 3}, that is, p-type (SrO/AlO{sub 2}) and n-type (TiO{sub 2}/LaO) interfaces. Our results demonstrate that the SrTiO{sub 3} in the sample with the n-type interface has a large polarized region, while that with the p-type interface has a limited polarized region. In addition, the atomic intermixing was observed to extend deeper into STO substrate at the n-type interface than at the p-type. These differences result in different degrees of band bending, which likely contributes to the striking difference in electrical conductivity between the two types of interfaces.

  19. Optically pumped vertical-cavity surface-emitting laser at 374.9 nm with an electrically conducting n-type distributed Bragg reflector

    Science.gov (United States)

    Liu, Yuh-Shiuan; Saniul Haq, Abul Fazal Muhammad; Mehta, Karan; Kao, Tsung-Ting; Wang, Shuo; Xie, Hongen; Shen, Shyh-Chiang; Yoder, P. Douglas; Ponce, Fernando A.; Detchprohm, Theeradetch; Dupuis, Russell D.

    2016-11-01

    An optically pumped vertical-cavity surface-emitting laser with an electrically conducting n-type distributed Bragg reflector was achieved at 374.9 nm. An epitaxially grown 40-pair n-type AlGaN/GaN distributed Bragg reflector was used as the bottom mirror, while the top mirror was formed by a dielectric distributed Bragg reflector composed of seven pairs of HfO2/SiO2. A numerical simulation for the optical mode clearly demonstrated that a high confinement factor was achieved and the threshold pumping power density at room temperature was measured as 1.64 MW/cm2. The achieved optically pumped laser demonstrates the potential of utilizing an n-type distributed Bragg reflector for surface-emitting optical devices.

  20. High-temperature thermoelectric properties of La-doped BaSnO3 ceramics

    International Nuclear Information System (INIS)

    Yasukawa, Masahiro; Kono, Toshio; Ueda, Kazushige; Yanagi, Hiroshi; Hosono, Hideo

    2010-01-01

    To elucidate the thermoelectric properties at high temperatures, perovskite-type La-doped BaSnO 3 ceramics were fabricated by a polymerized complex (PC) method and subsequent spark plasma sintering (SPS) technique. Fine powders of Ba 1-x La x SnO 3 (x = 0.00-0.07) were prepared by the PC method using citrate complexes, and SPS treatment converted the powders into dense ceramics with relative densities of 93-97%. The La content dependence of the lattice parameter suggested that the solubility of La for Ba sites was approximately x = 0.03. The temperature dependence of the electrical conductivity σ and Seebeck coefficient S showed that each La-doped ceramic was an n-type degenerate semiconductor in the measured temperature range of 373-1073 K. The La content dependence of the S values indicated that the electron carrier concentration increased successively up to x = 0.03, which was the solubility limit of the La atoms. The thermoelectric power factors S 2 σ increased drastically with La doping, and reached a maximum for x = 0.01 with values of 0.8 x 10 -4 W m -1 K -2 at 373 K to 2.8 x 10 -4 W m -1 K -2 at 1073 K.