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1.
The dependence of the mobility of charge carriers on voltage has been studied in undoped GaSe single crystals and crystals doped with gadolinium; the latter crystals have exhibited various values of dark resistivity (??d.r ?? 104?108 ?? cm at 77 K) and of the doping level (N = 10?5, 10?4, 10?3, 10?2, and 10?1 at %). It is established that the dependence of the charge-carrier mobility on the electric field applied to the sample E ?? 102 V/cm is observed in undoped high-resistivity GaSe crystals (??d.r ?? 104 ?? cm) and in lightly doped GaSe crystals (N ?? 10?2 at %) in the region of T ?? 150 K. It is found that this dependence is not related to heating of the charge carriers by an electric field; rather, it is caused by elimination of drift barriers as a result of injection. 相似文献
2.
A Novel Optical Thermometry Strategy Based on Diverse Thermal Response from Two Intervalence Charge Transfer States
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Yan Gao Feng Huang Hang Lin Jiangcong Zhou Ju Xu Yuansheng Wang 《Advanced functional materials》2016,26(18):3139-3145
In this work, a novel thermometry strategy based on the diversity in thermal quenching behavior of two intervalence charge transfer (IVCT) states in oxide crystals is proposed, which provides a promising route to design self‐referencing optical temperature sensing material with superior temperature sensitivity and signal discriminability. Following this strategy, uniform Tb3+/Pr3+:NaGd(MoO4)2 micro‐octahedrons are directionally synthesized. Originated from the diverse thermal responses between Tb3+‐Mo6+ and Pr3+‐Mo6+ IVCT states, fluorescence intensity ratio of Pr3+ to Tb3+ in this material displays excellent temperature sensing property in a temperature range from 303 to 483 K. The maximum absolute and relative sensitivity reaches as high as 0.097 K?1 and 2.05% K?1, respectively, being much higher than those of the previously reported optical thermometric materials. Excellent temperature sensing features are also demonstrated in the other Tb3+/Pr3+ codoped oxide crystals having d0 electron configured transition metal ions (Ti4+, V5+, Mo6+, or W6+), such as scheelite NaLu(MoO4)2 and NaLu(WO4)2, and monazite LaVO4 and perovskite La2Ti3O9, evidencing the universal validity of the proposed strategy. This work exploits an effective pathway for developing new optical temperature sensing materials with high performance. 相似文献
3.
A. V. Budnik E. I. Rogacheva V. I. Pinegin A. Yu. Sipatov A. G. Fedorov 《Journal of Electronic Materials》2013,42(7):1324-1329
V2VI3 compounds and solid solutions based on them are known to be the best low-temperature thermoelectric (TE) materials. The predicted possibility of enhancement of the TE figure of merit in two-dimensional (2D) structures has stimulated studies of the properties of these materials in the thin-film state. The goal of the present work is to study the dependences of the Seebeck coefficient S, electrical conductivity σ, Hall coefficient R H, charge carrier mobility μ H, and TE power factor P = S 2 σ of Bi2Te3 thin films on the composition of the initial bulk material used for preparing them. Thin films with thickness d = 200 nm to 250 nm were grown by thermal evaporation in vacuum of stoichiometric Bi2Te3 crystals (60.0 at.% Te) and of crystals with 62.8 at.% Te onto glass substrates at temperatures T S of 320 K to 500 K. It was established that the conductivity type of the initial material is reproduced in films fairly well. For both materials, an increase in T S leads to an increase in the thin-film structural perfection, better correspondence between the film composition and that of the initial material, and increase in S, R H, μ H, σ, and P. The room-temperature maximum values of P for the films grown from crystals with 60.0 at.% and 62.8 at.% Te are P = 7.5 × 10?4 W/K2 m and 35 × 10?4 W/K2 m, respectively. Thus, by using Bi2Te3 crystals with different stoichiometry as initial materials, one can control the conductivity type and TE parameters of the films, applying a simple and low-cost method of thermal evaporation from a single source. 相似文献
4.
Kenneth M. Beck Maureen I. Mccarthy Wayne P. Hess 《Journal of Electronic Materials》1997,26(11):1335-1341
Calcium carbonate and sodium nitrate are isostructural crystals in which the covalently bonded polyatomic anions are also
isoelectronic, however, the chemical properties of these crystals are distinctly different. In this study, we report results
involving the photostimulated desorption (PSD) of neutral CO and O(3P) products from geologic calcite (CaCO3) using low laser fluence at 193 nm. Product states are probed using (2+1) resonance enhanced multiphoton ionization for both
neutrals. The CO products display a narrow angular distribution normal to the surface and a translational energy characterized,
by a temperature (T=110K) significantly lower than that of the substrate (T=295K).1 Atomic oxygen products display both broader angular and kinetic energy distributions than that of the CO fragments. Emission
of O(3P) is seen at angles greater than 30° with respect to the surface normal. In contrast, recent PSD studies of product NO from
single crystal sodium nitrate (NaNO3) show product distributions with both thermal and hyper-thermal components.2 Projected density of state plots computed using periodic Hartree-Fock theory indicate a strong overlap in the metal and carbonate
bands of the low lying excited states in CaCO3, while NaNO3 was found to have a well-separated nitrate band in the excited state below the mixed metal/nitrate bands. The differences
in the electronic structure of these materials may account for differences in the observed product distributions in the PSD
of calcite and sodium nitrate. 相似文献
5.
We have grown CdGeAs2 single crystals by chemical vapor transport (CVT), a method not previously applied for this compound. The crystallographic data of this chalcopyrite (cell parametersa 0 = 5.9456 ± 0.0001Å, c0 = 11.2131 ± 0.0007Å) and its electrical transport properties are reported. Predominantly n-type crystals are obtained (at RTn = 1 · 1017cm?3, μn = 2000 cm2(Vs)?1). Vacuum heat treatment at 500° C yields a type conversion fromn- to p-type. In all p-type samples the minority carrier mobility is calculated to be larger than 10000 cm2(Vs)?1. 相似文献
6.
Silver gallium (indium) ternary selenides (tellurides) single crystals were studied through infrared reflection in the frequency range of 80–500 cm−1. These spectra presented four infrared-active modes for studied crystals. Spectral dependencies of optical constants were computed from reflectivity spectra. The frequencies of transverse and longitudinal optical modes, damping constants and oscillator strengths were also evaluated. By replacing light selenium anions by heavier tellurium ones in Ag3Ga5Se9 crystal and by substitution of light gallium cations by heavier indium ones in Ag3Ga5Te9 crystal all the bands shift towards low frequencies. The bands observed in IR spectra of studied crystals were assigned to various vibration types (valence and valence-deformation). Crystal structure and atomic composition ratio of the constituent elements in Ag3Ga5Se9, Ag3Ga5Te9 and Ag3In5Te9 crystals were revealed by structural characterization techniques of X-ray diffraction and energy dispersive spectroscopy. 相似文献
7.
B.‐J. Fang Y.‐J. Shan H.‐Q. Xu H.‐S. Luo Z.‐W. Yin 《Advanced functional materials》2004,14(2):169-173
Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZNT91/9) single crystals were grown by two methods: from solution using PbO as a self‐fluxing agent (SC method) and directly from the melt without fluxing (MC method). In both growth methods, an allomeric Pb[(Mg1/3‐Nb2/3)0.69Ti0.31]O3 (PMNT69/31) single crystal was used as a seed. X‐ray diffraction patterns of ground crystals showed that phase‐pure perovskite PZNT91/9 single crystals were successfully fabricated by the above two methods. The composition of the crystals obtained by both the SC and MC methods was analyzed using X‐ray fluorescence, which confirmed that the crystal composition is close to the nominal value, although volatilization of PbO and segregation during crystal growth are inevitable. The MC PZNT91/9 crystals exhibit excellent piezoelectric properties, with the piezoelectric constant, d33, in the range of 1800–2200 pC N–1. This value is comparable to that of the SC crystals. However, the MC crystals show an abnormal dielectric behavior. In contrast with the SC crystals, in the MC crystals a much broader dielectric peak appears in the dielectric response curves, accompanied by a much lower peak temperature of around 105 °C. Furthermore, frequency dispersion is apparent over a much wider temperature range (even more apparent than in pure relaxors), where a large, i.e., about 70 °C, full width at half maximum (FWHM) for the dielectric peaks is observed in the dielectric response. It is speculated that such an unusual phenomenon correlates with defects, microinhomogeneities, and polar regions in the as‐grown MC crystals. The origins of this abnormality have not been interpreted in detail until now. However, optical observation of the domain structure confirms that both the SC and MC crystals possess complex structural states. 相似文献
8.
GaAs-AIIBIVC
2
V
single crystals are grown by crystallization from dilute gallium fluxed solutions. The electric and luminescence properties
of the crystals obtained are investigated. It is shown that the technological process is accompanied by the standard doping
of gallium arsenide and makes it possible to grow gallium arsenide single crystals whose optoelectronic properties are controlled
by the AIIBIVAs2 compound introduced into the fluxed solution.
Fiz. Tekh. Poluprovodn. 33, 697–700 (June 1999) 相似文献
9.
Yifan Wang Feng Yang Xuanze Li Fan Ru Pei Liu Li Wang Wei Ji Jing Xia Xiangmin Meng 《Advanced functional materials》2019,29(43)
Inorganic cesium lead halide perovskite (CsPbX3, X = Cl, Br, I) is a promising material for developing novel electronic and optoelectronic devices. Despite the substantial progress that has been made in the development of large perovskite single crystals, the fabrication of high‐quality 2D perovskite single‐crystal films, especially perovskite with a low symmetry, still remains a challenge. Herein, large‐scale orthorhombic CsPbBr3 single‐crystal thin films on zinc‐blende ZnSe crystals are synthesized via vapor‐phase epitaxy. Structural characterizations reveal a “CsPbBr3(110)//ZnSe(100), CsPbBr3[?110]//ZnSe[001] and CsPbBr3[001]//ZnSe[010]” heteroepitaxial relationship between the covering CsPbBr3 layer and the ZnSe growth substrate. It is exciting that the epitaxial film presents an in‐plane anisotropic absorption property from 350 to 535 nm and polarization‐dependent photoluminescence. Photodetectors based on the epitaxial film exhibit a high photoresponsivity of 200 A W?1, a large on/off current ratio exceeding 104, a fast photoresponse time of about 20 ms, and good repeatability at room temperature. Importantly, a strong polarization‐dependent photoresponse is also found on the device fabricated using the epitaxial CsPbBr3 film, making the orthorhombic perovskite promising building blocks for optoelectronic devices featured with anisotropy. 相似文献
10.
Toshinori Taishi Hideaki IseYu Murao Takayuki OhsawaYuki Tokumoto Yutaka OhnoIchiro Yonenaga 《Microelectronic Engineering》2011,88(4):496-498
Local vibrations of oxygen in Ge crystals grown from a melt fully covered by B2O3 were evaluated by Fourier-transform infrared spectroscopy. Ge single crystals containing oxygen were grown by the Czochralski method under various growth conditions. Oxygen concentrations in the crystals were determined to be in the range between 8.5 × 1015 and 5.5 × 1017 cm−3 from the infrared absorption at 855 cm−1 originating in local vibration of Ge-Oi-Ge quasi-molecules. Absorption peaks relating to GeOx, SiOx and Si-Oi-Si were not detected in the as-grown crystals. The calibration coefficient for determining oxygen concentration in Ge crystals from the absorption peak intensity at 1264 cm−1 was estimated to be 1.15 × 1019 cm−2. 相似文献
11.
O. A. Matveev A. I. Terent’ev N. K. Zelenina V. N. Gus’kov V. E. Sedov A. A. Tomasov V. P. Karpenko 《Semiconductors》2005,39(9):998-1003
The process of self-compensation in Cd0.95Zn0.05Te:Cl solid-solution crystals has been studied by annealing single crystals under a controlled Cd vapor pressure, with subsequent measurements of the Hall effect, photoluminescence, carrier lifetime and mobility, and photocurrent memory in the annealed crystals. By means of this annealing, conditions of thermal treatment that make it possible to fabricate low-conductivity samples with a low carrier density, 107–1011 cm?3, are defined. In these samples, a p → n conduction inversion is observed at a higher free-carrier density (n, p ≈ 109 cm?3) and the dependence of the electron density on the Cd vapor pressure exhibits a more gentle slope than in the case of CdTe:Cl crystals. The obtained data are discussed in terms of a self-compensation model in which intrinsic point defects act as acceptors with deep levels. This level is attributed to a Zn vacancy, which remains active at high Cd pressure. 相似文献
12.
Lithium lutetium fluoride (LiLuF4) single crystals doped with different Dy3+ ion concentrations were grown by Bridgman method. The Judd-Ofelt (J-O) strength parameters (Ω2, Ω4, Ω6) of Dy3+ in LiLuF4 crystal are calculated according to the measured absorption spectra and the J-O theory, by which the asymmetry of the Dy3+:LiLuF4 single crystal and the possibility of attaining stimulated emission from 4F9/2 level are analyzed. The capability of the Dy3+:LiLuF4 crystal in generating white light by simultaneous blue and yellow emissions under excitation with ultra- violet light is produced. The effects of excitation wavelength and doping concentration on chromaticity coordinates and photoluminescence intensity are also investigated. Favorable CIE coordinates, x=0.319 3 and y=0.349 3, can be obtained for Dy3+ ion in 2.701% molar doping concentration under excitation of 350 nm. 相似文献
13.
K. J. Bachmann E. Buehler J. L. Shay A. R. Strnad 《Journal of Electronic Materials》1975,4(2):389-406
The growth of bulk indium phosphide crystals via liquid encapsulated Czochralski pulling from both stoichiometric and nonstoichiometric
melts is described. Nominally un-doped crystals with carrier concentration ND-NA = 6 × 1015 cm−3 and Hall mobilities of 4510 cm2/Vsec at room temperature were grown. Also, we prepared Zn-or Cd-doped p-type crystals in the range 1016 ≤ NA-ND ≤ 1018 cm−3 with Hall mobilities ≤ 130 cm2/Vsec and Sn-doped n-type crystals in the range 4 × 1017 ≤ NA-ND ≤ 1018 cm-3 with Hall mobilities ≤ 2400 cm2/Vsec. The dislocation density of LEC pulled InP crystals is typically ~ 104 cm−2. 相似文献
14.
Visible emission from ZnO doped with rare-earth ions 总被引:1,自引:0,他引:1
W. M. Jadwisienczak H. J. Lozykowski A. Xu B. Patel 《Journal of Electronic Materials》2002,31(7):776-784
We report the results of a cathodoluminescence (CL) and photoluminescence (PL) study of ZnO-bulk single crystals and epilayer
thin-film samples grown on a sapphire (0001) substrate and doped by implantation with rare-earth ions (RE3+): Pr3+, Dy3+, Ho3+, Er3+, Tm3+ (bulk crystals, co-doped with Li), Sm3+, Dy3+, and Er3+ (epilayers). The PL and PL excitation (PLE) spectra of polycrystalline ZnO doped with RE3+ ions (Nd3+, Dy3+, Er3+, and Tm3+) and codoped with Li+, Cl−, and N− ions have also been studied. 相似文献
15.
H. Udono K. Nakamori Y. Takahashi Y. Ujiie I. J. Ohsugi T. Iida 《Journal of Electronic Materials》2011,40(5):1165-1170
We have investigated the crystal growth of single-phase MnSi1.75−x
by a temperature gradient solution growth (TGSG) method using Ga and Sn as solvents and MnSi1.7 alloy as the solute, and measured the thermoelectric properties of the resulting crystals. Single-phase Mn11Si19 and Mn4Si7 crystals were grown successfully using Ga and Sn as solvents, respectively. The typical size of a grown ingot of Mn11Si19 was 2 mm to 4 mm in thickness and 12 mm in diameter, whereas Mn4Si7 had polyhedral shape with dimensions in the range of several millimeters. The single-phase Mn11Si19 has good electrical conduction (ρ = 0.89 × 10−3 Ω cm to 1.09 × 10−3 Ω cm) compared with melt-grown multiphase higher-manganese silicide (HMS) crystals. The Seebeck coefficient, power factor,
and thermal conductivity were 77 μV K−1 to 85 μV K−1, 6.7 μW cm−1 K−2 to 7.2 μW cm−1 K−2, and 0.032 W cm−1 K−1, respectively, at 300 K. 相似文献
16.
Krishna C. Mandal Sung Hoon Kang Michael Choi Jiuan Wei Lili Zheng Hui Zhang Gerald E. Jellison Michael Groza Arnold Burger 《Journal of Electronic Materials》2007,36(8):1013-1020
Spectrometer-grade CdTe single crystals with resistivities higher than 109 Ω cm have been grown by the modified Bridgman method using zone-refined precursor materials (Cd and Te) under a Cd overpressure.
The grown CdTe crystals had good charge-transport properties (μτ
e = 2 × 10−3 cm2 V−1, μτ
h = 8 × 10−5 cm2 V−1) and significantly reduced Te precipitates compared with crystals grown without Cd overpressure. The crystal growth conditions
for the Bridgman system were optimized by computer modeling and simulation, using modified MASTRAPP program, and applied to
crystal diameters of 14 mm (0.55′′), 38 mm (1.5′′), and 76 mm (3′′). Details of the CdTe crystal growth operation, structural,
electrical, and optical characterization measurements, detector fabrication, and testing using 241Am (60 keV) and 137Cs (662 keV) sources are presented. 相似文献
17.
O. V. Vakulenko V. N. Kravchenko V. D. Ryzhikov V. I. Silin N. G. Starzhinskii 《Semiconductors》1997,31(10):1041-1045
The spectral and kinetic parameters of the X-ray luminescence of ZnSe crystals doped with Zn, Se, and Te were investigated
during the growth process at temperatures in the range 80–500 K, and also after annealing in Zn vapor. ZnSe crystals grown
from a stoichiometric mixture, or mixture containing chalcogenide impurities, typically produce the minimum level of afterglow
and a rapid rise of X-ray luminescence, as well as a shift of its peak from the infrared region toward shorter wavelengths
after annealing in zinc. ZnSe crystals grown from material with excess of Zn have a relatively low X-ray luminescence yield
and a substantial level of afterglow. It is assumed that the growth of Te-activated crystals is accompanied by the development
of thermally stable complexes of the form V
ZnTeSe that act as radiative recombination centers. The introduction of excess Zn into the initial mixture produces a reduction
in the concentration of V
Zn and, hence, in the concentration of radiative recombination centers. It is shown that, for free-electron concentrations n<1018 cm−3, the afterglow time constant τ can be described as a function of n by a model of radiative recombination that involves a single impurity level, whereas for n>1018 cm−3, the time constant decreases with increasing n, which cannot be explained in terms of the simple model. It is suggested that radiative recombination centers of a new type
are produced as a result of prolonged annealing in Zn vapor.
Fiz. Tekh. Poluprovodn. 31, 1211–1215 (October 1997) 相似文献
18.
Electron spin resonance and the Hall effect are investigated in n-Pb1−x
SnxTe:Gd crystals grown from melt. It is found that there is no direct correlation between the free electron density and the
density of the Gd3+ impurity in these crystals. The conclusion is drawn that the the electron conductivity of Pb1−x
SnxTe:Gd crystals is not caused by the Gd impurity but by intrinsic defects of the crystal lattice which have zero activation
energy due to the Gd impurities.
Fiz. Tekh. Poluprovodn. 32, 1331–1333 (November 1998) 相似文献
19.
《Materials Science in Semiconductor Processing》2001,4(1-3):205-207
In this paper, we present a simple non-destructive method for testing SiC plate single crystals of any size and shape. The method is based on measuring the impedance changes of an inductive ferrite-cored coil due to placing the sample into the core gap. The method is valid for any SiC polytypes, though we used 6H one. Using this method we have obtained and discussed a conductivity as a function of doping level (Nd–Na) for 6H–SiC Lely crystals. The conductivity measurements were carried out with alternating current of 747 kHz frequency. The sensitivity of the method is limited by minimal conductivity 1 Ω−1 cm−1 (that is corresponding to (Nd–Na)∼2×1016 cm−3 for 6H–SiC : N Lely crystals). 相似文献
20.
S. R. Samedov O. Baykan A. Gulubayov 《Journal of Infrared, Millimeter and Terahertz Waves》2004,25(5):735-747
Near IR properties of the mixed TlInS2xSe2(1?x) have been studied previously by the present authors. In this work the temperature and frequency dependence's of the conductivity and the current-voltage characteristics (in relatively weak electric field), have been investigated for monoclinic TlInS2xSe2(1?x) crystals, which are perspective materials for IR applications. From the temperature dependence's of conductivity in the direction perpendicular to c- axis the band gap Eg = 2.22 eV was determined for β--TlInS2 crystals. The impurity centres were determined located at 0.43, 0.73 eV and 0.35, 0.48, 1.12 eV for the direction of current i//c and i ⊥ c, respectively. The concentration of the centres located at 0.48 and 1.12 eV were calculated to be NA ? ND = 4.8 · 109 cm?3 and 1.9 · 1011 cm?3, respectively. It was found that in the solid solutions TlInS2xSe2(1?x) for 0.3 ≤ x ≤ 1, the conductivity follows the dependence σ (v) = σ0·υs in the temperature range between 100 to 600 K. In the temperature range of 80-400 K charge bounce plays an important role in the conductivity mechanism. Occurrence of the deep and low-levels impurity centres and a “tail” of the density of energy states in TlInS2xSe2(1?x) crystals make them perspective for practical applications: switching and memory effects, N-type current-voltage characteristics, induced conductivity etc. 相似文献