Slider LPE of Hg1-xCdxTe using mercury pressure controlled growth solutions

Homogeneous, nearly perfect single crystals of Hg_1-xCd_xTe are extremely difficult to prepare due primarily to the high vapor pressure of mercury. However, epitaxially grown Hg_1-xCd_xTe layers have a high potential for yielding material of a substantially higher quality. Using a new, open-tube, horizontal slider-type liquid phase epitaxial (LPE) growth technique, in which mercury pressure controlled growth solutions are used, a high degree of growth solution compositional control has been demonstrated. LPE layers of Hg_1-xCd_xTe have been grown on CdTe substrates and their high quality has been confirmed by optical, transport and electron microprobe measurements. Layer thicknesses are uniform and have been varied from 5 to 40 μ by changing the degree of supercooling or the growth time. An electron carrier concentration as low as 8.6 × 10¹⁵/cm³ and electron Hall mobilities up to 2.8 × 105 cm²/V-sec at 77K have been measured on in situ annealed samples. This work was sponsored by the Department of the Air Force and the U.S. Army Research Office.     

Effects of In and Sb doping in LPE growth thermodynamics and in GaAs layer qualities

We have experimentally determined the distribution coefficients of In and Sb in liquid phase epitaxially (LPE) grown GaAs at several different temperatures and found them to be consistent with the values calculated from the pseudobinary phase diagram of the ternary system at a dilute In or Sb concentration. Both In and Sb are found to be effective in reducing the dislocation densities in the LPE grown GaAs epi-layers. Studies of the phase diagram and the surface morphology indicate that Sb is more effective than In. Based on the results from the surface morphology, x-ray broadening and etch pit density (EPD) data, the optimal Sb concentration was 2–3 × 10¹⁹ cm⁻³.     

InAs基室温中波红外探测器的液相外延生长

材料质量好坏对于获得高性能红外探测器至关重要。提出决定材料质量的关键点在于精准控制材料结构中层与层之间的晶格失配度,报道了晶格失配对材料质量和器件暗电流性能的影响。实验结论表明在液相外延技术生长的InAs/InAsSbP材料体系中,InAs和InAsSbP间的晶格失配不是越小越好,而是有一个最佳值。如果晶格失配偏离这个值,不管是偏大还是偏小,材料的质量都会恶化。阐述了如何调整生长参数以获得合适的晶格失配度。制备了具有适宜晶格失配度的红外探测器件,该探测器零偏压下的室温峰值探测率为6.8×10⁹ cm Hz^1/2W^-1,与国际商用InAs探测器的指标相当。     

Evaluation of binary and ternary melts for the low temperature liquid phase epitaxial growth of silicon

Liquid-phase-epitaxy allows the growth of good quality layers at low temperature, although this advantage is yet to be fully exploited for silicon. Silicon solubility was investigated in a range of binary and ternary metal alloys to identify suitable low temperature combinations. Gold based alloys were determined to be the most suitable for the growth of lightly doped layers, with Au-Bi and Au-Pb alloys giving high silicon solubilities at temperatures below 400° C. Liquid-phase-epitaxy of silicon was demonstrated over the 380–450° C range from such alloys.     

Status of Te-rich and Hg-rich liquid phase epitaxial technologies for the growth of (Hg,Cd)Te alloys

In this review, we summarize the progress to-date in the technology of Hg_1−xCd_xTe liquid phase epitaxial growth from Hg-rich and Te-rich solutions. Areas of research which need to be pursued to further improve the state of the art in device performance are discussed.     

Liquidus isotherms,solidus lines and LPE growth in the Te-rich corner of the Hg-Cd-Te system

Liquidus isotherms for the Hg_1−xCd_xTe primary phase field in the Te-rich corner of the Hg-Cd-Te ternary system have been determined for temperatures from 425 to 600‡C by a modified direct observational technique. These isotherms were used to help establish conditions for the open-tube liquid phase epitaxial growth of Hg_1−xCd_xTe layers on CdTe_1−ySe_y substrates. Layers with x ranging from 0.1 to 0.8 have been grown from Te-rich HgCdTe solutions under flowing H₂ by means of a horizontal slider technique that prevents loss of Hg from the solutions by evaporation. Growth temperatures and times of 450–550‡C and 0.25–10 min, respectively, have been used. The growth solution equilibration time is typically 1 h at 550‡C. Source wafers, supercooled solutions, and (111)-oriented substrates were employed in growing the highest quality layers, which were between 3 and 15 Μm thick. Electron microprobe analysis was used to determine x for the epitaxial layers, and the resulting data, along with the liquidus isotherms, were used to obtain solidus lines. In addition to EMP data, optical transmission results are given. This work was sponsored by the Department of the Air Force and the U. S. Army Research Office.     

不同固液相组分下土壤蒽的激光诱导荧光发射光谱特性研究

以蒽为研究对象,研究了不同土壤固、液相组分下蒽的激光诱导荧光发射光谱特性。结果显示,在266 nm激光激发下,土壤蒽在420 nm和444 nm附近分别具有荧光峰,当土壤的原生矿物和次生矿物比例发生变化时,蒽的荧光光谱峰位置未发生明显偏移,420 nm处荧光峰处强度的相对标准偏差为4.52%;土壤中腐殖质种类、浓度改变时,蒽的荧光强度随浓度增大而降低,在不同浓度的腐殖酸和富里酸的土壤中,420 nm处的荧光峰处强度的相对标准偏差分别为38.1%和27.4%,且正交实验的极差分析结果表明腐殖酸对强度影响大于富里酸;受到重金属污染后的土壤蒽的激光诱导荧光强度明显下降,但液相重金属不同浓度的土壤中,蒽在420 nm处的荧光强度差异不大,荧光峰位置未发生明显偏移.在土壤中含有不同浓度的Cd时,其相对标准偏差为1.60%,含有不同浓度的Cu时,其相对标准偏差为2.05%,含有不同浓度的Pb时,其相对标准偏差为4.54%。因此,采用荧光峰强度定标法测定时,应考虑固液组分变化导致的光谱强度差异。该研究结果为采用激光诱导荧光光谱技术对土壤蒽准确测量提供了基础数据。     

电化学STM及对固液界面的研究

电化学扫描探针显微术是将电化学研究系统和扫描探针显微技术（Scanning Probe Microscopy:SPM)相结合而产生的一门新的研究技术。该技术的最大特点是可以在溶液环境下工作,以原子分辨率,实时,原位,三维空间观察,控制化学反应及过程,又可以对材料进行原子级加工等,本文将以SPM技术的重要分支－电化学扫描隧道显微技术（ECSTM：electrochemical scanning tunneling microscopy)为主,简要介绍其工作原理,对固液界面的研究及发展趋势。     

Liquid phase epitaxial growth and characterization of InAsxSb1−;x AND In1−yGaySb ON (111)B InSb substrates

Liquid phase epitaxial growth of InAs_xSb_1−x, for 0<_x<0.27 and In_1−yGa_ySb, for 0<y<0.37, has been successfully accomplished on (111)B InSb substrates between the temperatures of 450 and 520°C. The phase diagrams and the growth conditions for high-quality planar epitaxial layers have been determined. For growth of InAs_xSb_1−x for high values of x, the strong tendency of the ternary melt to dissolve the substrate, even when the liquid is a few degrees below its melting point, was negated by using large supercooling. Small supercooling of zero to 5.6°C were required over the whole range of composition examined for (In.Ga)Sb, whereas, for example, supercooling greater than 30°C was required to grow InAs_o.26Sb_o.74 to avoid substrate dissolution. Lattice mismatch to the substrate was relieved by compositional grading. Etch pit studies in both materials yielded dislocation densities ranging from 5.8 × 10² to 2×10⁶ cm⁻² with most materials in the low 10⁴ range. Hall and resistivity measurements performed at 300K and 77K on most samples showed an impurity contamination of the epitaxial layers. Some samples were n-type (carrier concentration approximately 10¹⁷/cm³), with varying degrees of acceptor compensation and others were n-type (carrier concentration approximately l0¹⁷/cm³) at room temperature due to intrinsic conduction, but exhibited p-type conduction (carrier concentration approximately 5×l0^l6/cm³) at 77K. Hall measurements performed on one of the latter samples ofvery low As content from 77K to 4.2K to examine hole freeze-out yielded an acceptor level ionization energy of 0.0126eV which is close to the effective mass acceptor level ionization energy in InSb. The electron-to-hole mobility ratio was also found to be 65.9. Electron microprobe analysis showed silicon to be the dominant impurity.     

The effect of temperature on the growth of Ag2O nanoparticles and thin films from bis(2-hydroxy-1-naphthaldehydato)silver(I) complex by the thermal decomposition of spin–coated films

Bis(2-hydroxy-1-naphthaldehydato)silver(I) complex (Ag-HNA) was prepared through the reaction of the ligand and silver nitrate. Silver oxide nanoparticles were synthesized via thermal decomposition at different temperatures by calcinating Ag complex inside a ceramic boat. The same metal precursor was used to prepare Ag₂O thin films at different temperatures by spin coating onto a glass substrate. The prepared silver complex was characterized by Fourier transform infrared (FTIR) spectroscopy, elemental analysis, nuclear magnetic resonance (NMR) and thermogravimetric (TGA) analysis. The effects of decomposition temperatures (150, 200, 250 and 300 °C) and of the annealing temperatures for the films at 200, 250, 300 and 350 °C were studied. The surface morphologies, structural and optical properties of the nanoparticles and films were investigated. The results shows that the temperature plays a significant role in controlling nature of the nanoparticles and thin films. The X-Ray diffraction patterns of Ag₂O nanoparticles and the prepared thin films prepared revealed the face-centred cubic structures.     

Lpe growth of Hgl−xCdxTe using conventional slider boat and effects of annealing on properties of the epilayers

The epitaxial layers of Hg_1−xCd_xTe (0.17≦×≦0.3) were grown by liquid phase epitaxy on CdTe (111)A substrates using a conventional slider boat in the open tube H₂ flow system. The as-grown layers have hole concentrations in the 10¹⁷− 10¹⁸ cm⁻³ range and Hall mobilities in the 100−500 cm²/Vs range for the x=0.2 layers. The surfaces of the layers are mirror-like and EMPA data of the layers show sharp compositional transition at the interface between the epitaxial layer and the substrate. The effects of annealing in Hg over-pressure on the properties of the as-grown layers were also investigated in the temperature range of 250−400 °C. By annealing at the temperature of 400 °C, a compositional change near the interface is observed. Contrary to this, without apparent compositional change, well-behaved n-type layers are obtained by annealing in the 250−300 °C temperature range. Sequential growth of double heterostructure, Hg_l−xCd_xTe/Hg_l−yCd_yTe on a CdTe (111)A substrate was also demonstrated.