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1.
Pb 1−xSn xTe single crystals have been grown by a vertical Bridgman method. They have typical Hall mobilities and carrier concentration values of 10 3 cm 2/V · s and 10 18 cm -3, respectively, and change from p- to n-type as the Sn content increases. The ingots were single crystal with a subgrain structure that has a misorientation no higher than 2′. The segregation of Sn has been determined and it suggests that there is a convective flow in the liquid. 相似文献
2.
Single crystal of CdTe or dilute alloys of Cd 1−yZn yTe (y < 0.04) and CdTe 1−zSe z (z < 0.04) with low defect density, high purity, and large single-crystal area (>30 cm 2) are required as substances for high-quality epitaxial Hg 1−xCd xTe thin films in the infrared (IR) detector industry. Bridgman or gradient freeze is the most common technique used for commercial production of these materials because of its success in producing large-area substrates of good quality and reproducibility. For epitaxial growth of Hg 1−xZn xTe, which has been of considerable interest in recent years as an IR detector material, the substrate of choice has been Cd 0.80Zn 0.20Te, for lattice matching with long-wavelength Hg 1−xZn xTe epitaxial layers ( x = 0.15). The primary focus of this paper is on CdZnTe, which is currently the preffered subtrate material and most widely used for both HgCdTe and HgZnTe epitaxy. This paper reviews the current status of bulk substrate technology for IR detector applications, highlighting critical issues and essential research areas for further improvement of these materials. 相似文献
3.
The choice a suitable crystal growth method and a reasonable x value is of profound importance in the preparation of high quality Cd 1−xZn xTe crystals for x-ray and gamma-ray detectors. The present paper reviews the evolution and development of Cd 1−xZn xTe crystal growth for x-ray and gamma-ray detectors. At the same time, emphasis is put upon finding the relationship between the x value and the quality of the Cd 1−xZn xTe. Three sets of Cd 1−xZn xTe ingots with different x values, specifically 0.10, 0.15, and 0.20 were grown by the vertical Bridgman method (VBM) and characterized. Their x specification was then correlated with their dislocation densities, Te precipitates, inclusions, IR transmission, resistivities, and impurity concentrations, respectively. It was found that VBM Cd 0.85Zn 0.15Te as grown in this paper possessed the best choice of qualities with respect to defects and impurities. 相似文献
4.
The study of structural properties of quaternary Pb 1−x−ySn xMn yTe alloys revealed that they crystallise in a cubic structure of NaCl-type for a wide region of manganese content (up to y=0.16). It was found from X-ray measurements and microprobe analysis that Vegard's law is obeyed. The dependencies of the lattice constants on composition for Pb 1−x−ySn xMn y, Pb 1−yMn yTe and Sn 1−yMn yTe were used to extract the lattice parameter of NaCl-type MnTe phase by extrapolation. The experimental data were also used to obtain an improved estimate of the covalent octahedral radius for Mn. 相似文献
5.
Solid solutions of Nd xLa 2−xcaB 10O 19 with different Na 3+ concentration have been synthesized by substituting Nd 3+ for La 3+ in La 2CaB 10O 19 Powder X-ray diffraction analysis shows that Nd 3+ is easy to incorporate into the crystal. Single crystal nd xLa 2−xCaB 10O 19 (NLCB) in centimeter size has been grown by Kyropoulos method. The crystal has strong absorption around 580nm and 805nm. The fluorescence spectra indicate that there is an energy transition at 1.06μm. And the SHG of NLCB is about the twice as that of KDP. These favorable features make NLCB a candidate for laser NLO multifunctional materials. 相似文献
6.
The effects of ion implantation on the properties of spin-on sol–gel Ba 0.7Sr 0.3TiO 3 (BST) thin films were studied by implanted Ar +, N +, and F + doses. The F +-implanted BST samples present leakage current density <10 −6 A/cm 2 at 2.5 V and dielectric constant 450. The leakage current of F +-implanted BST samples was reduced about one order of magnitude as compared with that of samples with implanted Ar +, N + or without implantation. The thickness shrinkage from 135 to 115 nm was observed in F +-implanted BST films (before annealing treatment) and a respective increase in the refractive index from 1.84 to 2.05 was measured. After annealing the implanted samples, the changes of thickness and refractive index depend on the concentration of implanted dose. Based on an infrared transmission study of the samples we suggest that the ion-implanted samples with smaller dose (5×10 14 cm −2) have fewer −OH contaminants than the non-implanted or implanted samples with the larger doses (1×10 15 cm −2). Based on the results presented, we conclude that suitable ion implantation densifies the spin-on sol–gel BST films and reduces the −OH contaminants in the films. 相似文献
7.
Experimental results are presented for SiC epitaxial layer growths employing a unique planetary SiC-VPE reactor. The high-throughput, multi-wafer (7×2″) reactor, was designed for atmospheric and reduced pressure operation at temperatures up to and exceeding 1600°C. Specular epitaxial layers have been grown in the reactor at growth rates ranging from 3–5 μm/h. The thickest layer grown to date is 42 μm thick. The layers exhibit minimum unintentional n-type doping of 1×10 15 cm −3, and room temperature mobilities of 1000 cm 2/V s. Intentional n-type doping from 5×10 15 cm −3 to >1×10 19 cm −3 has been achieved. Intrawafer layer thickness and doping uniformities (standard deviation/mean at 1×10 16 cm −3) are typically 4 and 7%, respectively, on 35 mm diameter substrates. Moderately doped, 4×10 17 cm −3, layers, exhibit 3% doping uniformity. Recently, 3% thickness and 10% doping uniformity (at 1×10 16 cm −3) has been demonstrated on 50 mm substrates. Within a run, wafer-to-wafer thickness deviation averages 9%. Doping variation, initially ranging as much as a factor of two from the highest to the lowest doped wafer, has been reduced to 13% at 1×10 16 cm −3, by reducing susceptor temperature nonuniformity and eliminating exposed susceptor graphite. Ongoing developments intended to further improve layer uniformity and run-to-run reproducibility, are also presented. 相似文献
8.
The (Pb 0.90La 0.10)TiO 3 [PLT] thick films (3.0 μm) with a PbO buffer layer were deposited on the Pt(1 1 1)/Ti/SiO 2/Si(1 0 0) substrates by RF magnetron sputtering method. The PLT thick films comprise five periodicities, the layer thicknesses of (Pb 0.90La 0.10)TiO 3 and PbO in one periodicity are fixed. The PbO buffer layer improves the phase purity and electrical properties of the PLT thick films. The microstructure and electrical properties of the PLT thick films with a PbO buffer layer were studied. The PLT thick films with a PbO buffer layer possess good electrical properties with the remnant polarization ( Pr=2.40 μC cm −2), coercive field ( Ec=18.2 kV cm −1), dielectric constant ( εr=139) and dielectric loss (tan δ=0.0206) at 1 kHz, and pyroelectric coefficient (9.20×10 −9 C cm −2 K −1). The result shows the PLT thick film with a PbO buffer layer is a good candidate for pyroelectric detector. 相似文献
9.
Heavily carbon-doped p-type In xGa 1−xAs (0≤ x<0.49) was successfully grown by gas-source molecular beam epitaxy using diiodomethane (CH 2I 2), triethylindium (TEIn), triethylgallium (TEGa) and AsH 3. Hole concentrations as high as 2.1×10 20 cm −3 were achieved in GaAs at an electrical activation efficiency of 100%. For In xGa 1−xAs, both the hole and the atomic carbon concentrations gradually decreased as the InAs mole fraction, x, increased from 0.41 to 0.49. Hole concentrations of 5.1×10 18 and 1.5×10 19 cm −3 for x = 0.49 and x = 0.41, respectively, were obtained by a preliminary experiment. After post-growth annealing (500°C, 5 min under As 4 pressure), the hole concentration increased to 6.2×10 18 cm −3 for x = 0.49, probably due to the activation of hydrogen-passivated carbon accepters. 相似文献
10.
The Ge 25Ga 5Se 70 and Ge 30Ga 5Se 65 pure and Pr 3+-doped glasses were prepared by direct synthesis from elements and PrCl 3. It was found that up to 1 mol% PrCl 3 can be introduced in the Ge 25Ga 5Se 70 and Ge 30Ga 5Se 65 glasses. Both types of glasses with overstoichiometric and substoichiometric content of Se were homogeneous and of black color. The optical energy gap is Eoptg=2.10 eV, and the glass transition temperature is Tg=543 K for Ge 25Ga 5Se 70 and Tg=633 K for Ge 30Ga 5Se 65. The long-wavelength absorption edge is near 14 μm and it corresponds to multiphonon processes. Doping by Pr 3+ ions creates absorption bands in transmission spectra, which can be assigned to the electron transitions from the ground 3H 4 level to the higher energy levels of Pr 3+ ions 3H 5, 3H 6, 3F 2, 3F 3 and 3F 4, respectively. By excitation with YAG:Nd laser line (1064 nm), two intense luminescence bands (1343 and 1601 nm) were excited. The first band can be ascribed to electron transitions between 1G 4 and 3H 5 energy levels of Pr 3+ ions. Full width at half of maximum (FWHM) of the intensity of luminescence was found to be 70 nm for (Ge 25Ga 5Se 70) 1 − x(PrCl 3) x and (Ge 30Ga 5Se 65) 1 − x(PrCl 3) x glasses. The FWHM in selenide glasses is lower than in halide and sulphide glasses. The second luminescence band (1601 nm) can be probably ascribed to the transitions between 3F 3 and 3H 4 energy levels of Pr 3+ ions. The absorption and luminescence spectra of Pr 3+ ions in studied glasses are slightly influenced by stoichiometry of glassy matrix. The Raman spectra of studied glasses were deconvoluted and assignment of Raman bands to individual vibration modes of basic structural units was suggested. The structure of studied glasses is mainly formed by corner-sharing and edge-sharing GeSe 4 tetrahedra. The vibration modes of Ga-containing structural units were not found, they are apparently overlapping with Ge-containing structural units due to small difference between atomic weights of Ge and Ga. In the glasses with substoichiometry of Se, the Ge–Ge bonds of Ge 2Se 6 structural units were found. In Se-rich glasses the Se–Se vibration modes were found. In all studied glasses also ‘wrong' bonds between like atoms were found in small amounts. Maximum phonon energy of studied glasses is 320 cm −1. 相似文献
11.
11B ( I=3/2) MAS NMR in the binary glass system xV 2O 5–B 2O 3 ( x=0.053, 0.43) and the ternary glass system xV 2O 5–B 2O 3–PbO (0.1 x1.5) has been investigated at room temperature. In the xV 2O 5–B 2O 3 glasses, one NMR line due to BO 3 unit was observed. Meanwhile in the xV 2O 5–B 2O 3–PbO, two NMR lines which arise from BO 3 and BO 4 units were detected, where the appearance of BO 4 units is produced by the presence of PbO. From the computer-simulation of the 11B NMR central transition line ( m=−1/2↔1/2), the quadrupole parameters ( e2qQ/ h and η) for BO 3 units in xV 2O 5–B 2O 3, and those for BO 3 and BO 4 units in xV 2O 5–B 2O 3–PbO were obtained as a function of x. As the V 2O 5 content increases in xV 2O 5–B 2O 3–PbO, the e2qQ/ h and η values of the BO 3− associated resonance are found to slightly decrease and increase, respectively. Meanwhile, the e2qQ/ h and η values of BO 4− associated resonance in xV 2O 5–B 2O 3–PbO are found to slightly increase and decrease, respectively. By comparing the intensities of the total transitions ( m=−3/2↔−1/2, m=−1/2↔1/2, and 1/2↔3/2) for the 11B NMR line of BO 3 and BO 4 units contained in xV 2O 5–B 2O 3–PbO with those of respective standard samples of 0.053V 2O 5–B 2O 3 and NaBH 4, the quantitative fractions of BO 3 and BO 4 in xV 2O 5–B 2O 3–PbO were obtained as a function of x. 相似文献
12.
Vitreous BeF 2 was prepared by two techniques; (1) remelting of a technical grade material, and (2) vacuum distillation/fluoridation. Infrared spectroscopy studies have established that the first material contains about 0.5 wt.% hydroxyl, predicted to be coherently incorporated into the vitreous network as edge-linked [Be(OH) 4] 2− units. The distilled BeF 2 is water-free. The dc electrical conductivity of the remelted BeF 2 was measured as σ = (7.9 × 10 3/ T) exp(−24500 cal/mol/ RT) ω −1 cm −1 and for the distilled BeF 2 as σ = (3.0 × 10 5/ T) exp(−36700 cal/mol/ RT ω −1 cm −1 at temperatures to 280°C. Ionic transport studies utilizing a dc electrolysis polarization technique with N 2−F 2 and H 2−HF gas electrodes have demonstrated that the fluorine ion is the transport species. A general model for fluorine transport is proposed based upon a modified anti-Frenkel defect model. The difference in the fluorine transport process for the undistilled grade of BeF 2 is seen as a consequence of the anti-Frenkel defect pair interaction with the [Be(OH) 4[ 2− groupings. 相似文献
13.
Optical third-harmonic generation from some high-index glasses was investigated. The highest χ (3) was obtained from As 2S 3 glass 2.2 × 10 −12 esu/ This value was 100 times higher than that of pure SiO 2 glass and comparable with that of the polymer with monomer-doping, which are known as organic materials with quite high χ (3). From the relationship between χ (3) and composition, sulfide glasses were found to have higher χ (3) than oxide or semiconductor-doped oxide glasses with similar refractive indices. 相似文献
14.
We have grown undoped, Si- and Mg-doped GaN epilayers using metalorganic chemical vapor deposition. The grown samples have electron Hall mobilities (carrier concentrations) of 798 cm 2/V s (7×10 16 cm −3) for undoped GaN and 287 cm 2/V s (2.2×10 18 cm −3) for Si-doped GaN. Mg-doped GaN shows a high hole concentration of 8×10 17 cm −3 and a low resistivity of 0.8 Ω cm. When compared with undoped GaN, Si and Mg dopings increase the threading dislocation density in GaN films by one order and two orders, respectively. Besides, it was observed that the Mg doping causes an additional biaxial compressive stress of 0.095 GPa compared with both undoped and Si-doped GaN layers, which is due to the incorporation of large amount of Mg atoms (4–5×10 19 cm −3). 相似文献
15.
The vapor phase epitaxy of thin epilayers of VO 2 and V 1−xCrxO 2 on TiO 2 transparent substrates is described. Chemical vapor deposition occurs by reacting a (VOCL 3/CrO 2Cl 2/H 2O/H 2) mixture at about 800°C using argon as a carrier gas. The preparation of pure VO 2 requires special care to make it homogeneously stoichiometric and to obtain steep concentration profiles at the TiO 2/VO 2 interface. Layers were obtained which had electrical and optical properties comparable to the best bulk crystals grown by other techniques. Homogeneous solid solutions of V 1−xCr xO 2 epilayers were also grown for the first time in the range o < x < 0.17. Chromium concentration and homogeneity were determined by electron microprobe analysis. The separation coefficient k was also found to vary with x. It is close to unity below x = 0.001 and above this value Cr is incorporated more easily. High quality heteroepitaxial layers (1 cm 2 area, 1 to 30 μm thickness) of V 1−xCr xO 2 have for the first time allowed the measurement of the optical absorption coefficient. 相似文献
16.
A series of titania-silica glasses with 0–9% TiO 2 were fabricated using a sol/gel process. The sol was prepared by dispersing colloidal silica fume in an aqueous solution of titania which was synthesized through the acid-catalyzed hydrolysis of titanium isopropoxide. The sols gelled in 2–4 days, and then were dried for 6–8 days. The dry gels were sintered at 1450–1500°C to produce clear, dense, microstructure-free glasses. The gels underwent a total shrinkage of 50% to yield glass rods about 50 mm long and 5 mm in diameter, or glass discs about 4 cm in diameter and 5 mm thick. The drying step was most critical in the production of crack-free specimens. In the gel, the transmission electron microscope (TEM) revealed the presence of 1–5 nm rutile microcrystallites uniformly distributed within a network of colloidal silica particles. After sintering to 1450–1500°C, though, a dense, transparent, microstructure-free glass was created. Fourier transform infrared spectroscopy (FTIR) verified the formation of an amorphous solid-solution of titania and silica after sintering. The thermal expansion of the glasses was measured using a differential dilatometer. The average linear coefficients of thermal expansion (CTE @ 25–675°C) varied between +5 × 10−7 and −0.2 × 10−7°C−1 in the range 0 to 9% TiO2. The glass with 7.2% TiO2 exhibited a zero thermal expansion coefficient at 150–210°C. The hysteresis in CTE on heating and cooling was of the order of 0.01–0.02 ppm. 相似文献
17.
The 11B, 27Al, 29Si and 31P magic angle spinning (MAS) NMR spectra of MO–P 2O 5, MO–SiO 2–P 2O 5 and MO(M ′2O)–SiO 2–Al 2O 3–B 2O 3 (M=Mg, Ca, Sr and Ba, M ′=Na) glasses were examined. In binary MO–P 2O 5 (M=Ca and Mg) glasses, the distributions of the phosphate sites, P(Q n), can be expressed by a theoretical prediction that P 2O 5 reacts quantitatively with MO. In the ternary 0.30MO–0.05SiO 2–0.65P 2O 5 glasses, the 6-coordinated silicon sites were detected, whose population increases in the order of MgO xCaO–0.05SiO2–(0.95−x)P2O5 glasses, its population increases with an increase in f (=([P2O5]−[MO]−[B2O3]−[Na2O])/[SiO2]) and has maximum at f=9. The signal due to the 5-coordinated silicon atoms is also observed when x is smaller than 0.45. When three network-forming oxides such as SiO2, Al2O3 and B2O3 coexist, Al2O3 reacts preferably with MO. The populations of 4-coordinated boron atoms, N4, are expressed well with r/(1−r), where r=([Na2O]−[Al2O3])/([Na2O]−[Al2O3]+[B2O3]). The correlation of the Raman signal at 1210 and 1350 cm−1 with the NMR signal of Si(Q6) at −215 ppm is also seen. 相似文献
18.
We have first of all studied (in reduced pressure–chemical vapour deposition) the high-temperature growth kinetics of SiGe in the 0–100% Ge concentration range. We have then grown very high Ge content (55–100%) SiGe virtual substrates at 850 °C. We have focused on the impact of the final Ge concentration on the SiGe virtual substrates’ structural properties. Polished Si 0.5Ge 0.5 virtual substrates were used as templates for the growth of the high Ge concentration part of such stacks, in order to minimize the severe surface roughening occurring when ramping up the Ge concentration. The macroscopic degree of strain relaxation increases from 99% up to values close to 104% as the Ge concentration of our SiGe virtual substrates increases from 50% up to 100% (discrepancies in-between the thermal expansion coefficients of Si and SiGe). The surface root mean square roughness increases when the Ge concentration increases, reaching values close to 20 nm for 100% of Ge. Finally, the field (the pile-up) threading dislocations density (TDD) decreases as the Ge concentration increases, from 4×10 5 cm −2 (1–2×10 5 cm −2) for [Ge]=50% down to slightly more than 1×10 5 cm −2 (a few 10 4 cm −2) for [Ge]=88%. For [Ge]=100%, the field TDD is of the order of 3×10 6 cm −2, however. 相似文献
19.
Mössbauer absorption measurements have been made at room temperature on 57Fe in iron sodium silicate glasses containing 3–15 mol% Fe 2O 3 and various iron alkali silicate crystals in order to study the state of iron in these glasses. The spectra of all the glasses gave one doublet with a quadrupole splitting varying from 0.73–0.78 mm s −1, while those of Na 2O · Fe 2O 3 · 4 SiO 2 and 5 Na 2O · Fe 2O 3 · 8 SiO 2 crystals showed much smaller quadrupole splitting, 0.28 mm s −1 and 0.10 mm s −1, respectively, and an asymmetrical doublet of much narrower linewidth. When sodium was replaced by other alkali metals of larger size, such as K and Cs, in MFeSi 2O 6 and MFeSi 3O 8 crystals, the quadrupole splitting became wider and approached to 0.73 mm s −1. Such a variation was not observed for glasses. These results suggest that a larger number of non-identical sites exist in iron sodium silicate glasses than in the corresponding crystals. 相似文献
20.
Using chemical etching.method, the growth twins in self-frequency doubling laser crystal Yb xY 1−xAl 3(BO 34 have been observed. The etching pits on both sides of growth twin boundaries in the (10
1) slice are of the triangles with different orientations. The structure of growth twins is investigated by transmission synchrotron topography. In the transmission synchrotron topograph, the growth twins are visible not by ‘domain contrast’ but by ‘boundary contrast’, i.e. the twins appear in the topograph in form of X-ray kinematical diffraction contrast due to the lattice strain stemming from the impurity incorporation in the boundaries. The growth twins in Yb xY 1−xAl 3(BO 3) 4 crystal are of inversion types, since no domain contrast was observed. 相似文献
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