Interface Dynamics during Indium Antimonide Crystal Growth

Experiments with a stoichiometric InSb compound were first performed at small temperature gradient across the crystal/melt interface of 3 °C/cm and furnace translation velocity, V_frn, of 2 μ/sec. Known growth requirements for quality crystals were confirmed. They are, (1) the interface temperature must be close to the congruent melting temperature and, (2) the interface must be located within the adiabatic zone. These requirements can be obtained only through specific settings of the heater temperatures. An X-ray radioscopic system has been modified to accommodate real-time visualization of the crystal/melt interface during vertical Bridgman-Stockbarger growth of InSb. It is shown that asymmetric temperature settings of the heaters can be advantageously used to minimize defect formation. The interface temperature was assessed indirectly with calibrated outside thermocouples. Optical microscopy and electron microprobe analyses provided feedback on crystalline homogeneity.     

Growth Rate Effects during Indium-Antimony Crystal Growth

Local interface velocities are tracked radioscopically in the III-V semiconductor compound indium-antimony grown in a vertical Bridgman-Stockbarger furnace. Comparisons are made of interface velocities from five different compositions (40, 49, 50, 55, and 60 at.% Sb). Under specific growth conditions, the growth velocity for stoichiometric melts was comparatively constant and very close to the translation velocity. Measured chemical homogeneity was excellent, though polycrystallinity could occur when concentration boundary layers formed ahead of the interface. Off-stoichiometric melts exhibited initial supercooling, resulting in transient interface velocities and polycrystallinity. The observed supercooling is governed by chemical segregation in the melt. Thus, local growth velocity fluctuations are unambiguously attributed to a coupling of ompositional effects in the melt and crystal facetting kinetics.     

锑化铟晶体材料的发展及应用

锑化铟(InSb)晶体材料自发现伊始,基于其独特的物理化学性质和优良的工艺兼容性,成为了半导体材料领域研究的热点。近几十年来,由于其在红外探测领域的应用前景,更是深受国内外研究机构的广泛关注和重视,技术发展迅速。目前,InSb晶体材料作为制备高性能中波红外探测器的首选材料,应用前景和商业需求巨大,基于InSb晶体材料的红外探测器的快速发展更是大大提升了红外系统的性能,促进了红外技术在军民领域的广泛应用。本文主要介绍了InSb晶体材料的性质,梳理了国内外各公司及研究机构关于InSb晶体材料的研究进展,以及其在红外探测领域的应用情况,对其发展前景和趋势进行了展望。     

Crystallization of InSb in Aerogel Crucibles

A novel type of a furnace for Vertical-Gradient-Freeze growth VGF of semiconductors is introduced. The basic element - a silica aerogel crucible - allows us to detect the crystallisation front with a suitable IR-CCD-camera due to its transparency. The growth velocity and the temperature gradient ahead of the solid-liquid interface are directly obtained in an optical way from the experiment. This is demonstrated for the growth of InSb. The excellent thermal insulation properties of the aerogels lead to a nearly one-dimensional temperature field and a nearly planar crystallisation front.     

5英寸锑化铟晶片加工及表征

锑化铟(InSb)材料因其特殊的性质被广泛用于红外光电探测等领域。随着更大面阵中波红外焦平面探测器的发展以及对低成本InSb红外探测器的需求,所需的晶片材料尺寸也日益增加。本文通过采用新结构石墨托以及高精度低损伤单线切割实现了5英寸InSb晶体定向断段;采用低损伤边缘倒角技术同时优化研磨参数改善了5英寸InSb晶片研磨;通过优化贴片工序提高了5英寸InSb晶片抛光后的平整度;通过优化抛光液pH值以及配比提高了5英寸InSb晶片表面质量。同时,使用X射线晶体定向仪、原子力显微镜等测试仪器对5英寸InSb晶片的晶向及偏差、抛光表面宏观质量、几何参数、表面粗糙度、晶格质量进行了测试表征。测试结果表明,采用优化后的加工工艺制备出了高质量的5英寸InSb晶片,能够满足InSb红外探测器制备需求。     

Influence of substrate temperature on the properties of vacuum evaporated InSb films

Indium Antimonide (InSb) thin films were grown onto well cleaned glass substrates at different substrate temperatures (303, 373 and 473 K) by vacuum evaporation. The elemental composition of the deposited InSb film was found to be 52.9% (In) and 47.1% (Sb). X‐ray diffraction studies confirm the polycrystallinity of the films and the films show preferential orientation along the (111) plane. The particle size (D), dislocation density (δ) and strain (ε) were evaluated. The particle size increases with the increase of substrate temperature, which was found to be in the range from 22.36 to 32.59 nm. In Laser Raman study, the presence of longitudinal mode (LO) confirms that the deposited films were having the crystalline nature. Raman peak located at 191.26 cm^–1 shift towards the lower frequencies and narrows with increase in deposition temperature. This indicates that the crystallinity is improved in the films deposited at higher substrate temperatures. Hall measurements indicate that the films were p‐type, having carrier concentration ≅10¹⁶ cm^–3 and mobility (4–7.7) ×10³ cm²/Vs. It is observed that the carrier concentration (N) decreases and the Hall mobility (μ) increases with the increase of substrate temperature. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Directional Solidification and Melting of Eutectic GaIn

Eutectic gallium-indium is studied in a horizontal Bridgman furnace geometry. Differential temperature gradients are applied to solidify and melt the alloy while observing in-situ the interface morphology and the chemical segregation in the melt and in the solid as well. Upon cooling, a wedge-type indium-rich mushy zone develops at the cold wall. The melt is initially stirred by convective flow. After solidification starts the roll cell recedes to be replaced by a chemically layered conductive melt that eventually solidifies with rather uniform eutectic structure. Upon re-melting, the morphology of the interface adopts a profile that is predetermined by the original solid structure. Those patterns, as well as the flow, are different from single element solid melting experiments and have yet to be modeled. Under high thermal gradient the convective flow mixes the binary melt and the visualized density pattern eventually becomes that of a homogeneous melt.     

Detached solidification of InSb on earth

Detached solidification of lightly gallium-doped indium antimonide was achieved in the laboratory only when the ampoule was coated with hexagonal boron nitride and when the material appeared to be oxide-free. A furnace was constructed with the temperature increasing with height in order to minimize bouyancy-driven convection, so as to maximize transport of segregated dissolved gases into the gap between the growing solid and the ampoule wall. There appeared to be no difference in results with freezing rates of 5 and 10 mm/h. Best results were obtained when the ampoule was backfilled with 20 kPa of Ar-10% H₂ prior to sealing. The detached portions were depressed by several μm from adjacent attached regions, were dull, and sometimes had microfacets and steps.     

A statistical thermodynamic model for oxygen segregation during Czochralski growth of silicon single crystals

A thermodynamic model derived from atomic scale statistics is formulated for the crystal–melt interface where oxygen segregation occurs during silicon crystal growth by the Czochralski method. The model shows that the segregation coefficient is close to but less than unity. Approaches for controlling oxygen concentration in the resulted crystal are discussed.     

Solidification behavior and microstructural evolution of the Cr‐Nb eutectic alloy

A series of microstructures including fully coupled eutectic, both α‐Cr and β‐Cr₂Nb primary dendrites embedded in eutectic and only β‐Cr₂Nb primary dendrites plus eutectic were observed in the arc‐melted Cr‐Cr₂Nb eutectic alloy. By employing EPMA analysis performed at the eutectic regions, the eutectic composition of the Cr‐Cr₂Nb system was indicated to contain less than 18 at.%Nb. Based on the solidification phase selection involving phase competitive nucleation and growth, the α‐Cr phase was predicted to be the primary nucleating phase and the β‐Cr₂Nb the primary growing phase. Under large undercooling conditions, the solidification process was controlled by nucleation, which led to the formation of α‐Cr primary particles. With the decrease in undercooling, the solidification process developed into growth controlling, which caused the occurrence of β‐Cr₂Nb primary phase since the actual solidification path of the alloy lay within the hypereutectic region. The explanation was confirmed by the experimental composition analysis.     

Effects of anions on rapid growth and growth habit of KDP crystals

The synthesis of KDP from its raw material has been found exist in the growth solution. In the crystal growth experiment, significant extension of specific faces was observed at low dopant concentration. At high doping concentration, the growth rate of the whole crystal decreased with no significant habit modification. The inhibiting effects of phosphite and other H-bonding anionic ions on the growth of pyramidal faces are discussed. Rapid growth rate experiments have been carried out with purified material and an averaged growth rate of 18.6mm/day was obtained.     

Compositional effects accompanying near equilibrium vapour growth of solid solution crystals of the types IV‐VI and II‐VI

Near equilibrium evaporation‐condensation in a sealed ampoule leads to almost full compositional reproduction of a solid solution if it consists of components having comparable vapour pressures; this can be qualitatively interpreted by domination of entropy increase. Nevertheless, even vestigial separation requires closer characteristics, since it may prove crucial – particularly for properties of semiconducting solid solutions. Maximum component separation allowed by a small temperature difference is described here in terms of thermodynamics and kinetics of solid‐vapour and vapour‐solid phase transitions. Theoretical models of the determining effects having different character are shortly described, and their applicability areas are determined. Experimental data collected for crystal growth of numerous semiconducting solid solutions of the II‐VI and IV‐VI type support the conclusion drawn from the models that the near equilibrium crystal growth from the vapour in a closed system ensures the highest degree of compositional uniformity. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

原料对DKDP晶体生长习性及光学性能的影响

通过传统降温法,利用不同原料从氘化程度为85;的溶液中生长DKDP晶体并对加工样品进行了相关测试.研究了不同原料对DKDP晶体的生长和光学性能的影响.实验表明:采用高纯原料所得DKDP晶体的光学性能提高,但其晶体生长容易出现外扩现象.     

微重力条件下Marangoni数对分离结晶过程的影响

为了了解微重力条件下新型分离结晶生长过程中熔体热毛细对流的基本特征,利用有限差分法进行了三维数值模拟.当熔体顶部分别为自由表面及固壁边界条件时,得到了新型分离结晶Bridgrnan生长过程中熔体热毛细对流的速度分布和温度分布.结果表明:熔体顶部为自由表面时,当Marangoni数较小时,在上自由表面和下部狭缝处自由表面的表面张力的驱动下,熔体内部产生了逆时针和顺时针两个流动方向相反的流胞,此时熔体内的流动状态为稳态;随着Marangoni数进一步的增大,流胞的流动逐渐增强并逐步向熔体内部扩展,熔体内部温度分布非线性增强,上自由表面和下部狭缝处自由表面处速度增大;当Marangoni数超过某一临界值后,流动转化为非稳态流动.当熔体顶部为固壁时,与熔体顶部为自由表面时相比,临界Marangoni数增大.流动失稳的物理机制是流速的变化和阻力的变化之间存在滞后.     

溶剂对有机非线性光学晶体NPAN生长习性的影响

本文测定了有机晶体N-(4-硝基苯)-N-甲基-2-氨基乙腈(简称NPAN)在某些醇和酮有机溶剂中的溶解度,研究了NPAN在这些有机溶剂中的溶液热力学性质、溶质与溶剂的相互作用以及溶剂对NPAN结晶习性的影响.根据界面熵因子α值,预测了NPAN晶体在不同溶剂中低指数晶面的晶体生长机制.选择丁酮为生长溶剂,进行单晶生长实验.在35～25℃温度区间内,用溶液降温法在较高过饱和度下成功地培养出尺寸为37×7.0×7.0 mm3的棱柱状透明单晶,所得晶体的外形与预测的结果相吻合.     

Self-selecting vapour growth of bulk crystals – Principles and applicability

A method of self-selecting vapour growth (SSVG) for bulk binary and multernary crystals of semiconducting materials is reviewed comprehensively for the first time. Although it has been developed over three decades, the method is less well known – even though it is physically distinct from the more widely used ‘Piper–Polich’ and ‘Markov–Davydov’ vapour transport bulk growth methods. The means by which growth takes place on a polycrystalline source to form a crystal free from the walls is described. Modelling and empirical observations have been used to establish the characteristics of the almost isothermal temperature fields that drive the transport in SSVG. It is demonstrated that precise control of thermal radiation is a fundamental requirement for tailoring the temperature distribution—a fact that has been used well in the design of horizontal tube furnace growth rigs. Achievements in the growth of useful PbS, PbSe, PbTe, CdTe and ZnTe compound crystals are described. The SSVG method has proved to be particularly well suited to the growth of solid solutions, and the results of growth experiments, and of compositional and structural analysis, are presented for Pb(Se,S), (Pb,Sn)Se, (Pb,Sn)Te, (Pb,Ge)Te, Cd(Te,Se), Cd(Te,S) and (Cd,Zn)Te. The excellent compositional uniformity delivered is attributed to entropy driven mixing in the low thermal gradients present in SSVG.

To date, most SSVG has been done at the <50 g level for research or small scale production use. Prospects for scaling up the growth are considered, there being no barriers identified in principle. However, there is a limitation in that the shape of the grown crystals is not accurately controlled at present. To overcome this, and to offer an alternative method of scaling up, the use of vertical tube systems is explored. A significant additional advantage of the vertical configuration is that it allows for continuous recycling of the source/crystal mass so as to continuously self-refine the increasingly uniform – and crystalline – product. Achievements to date in growing II–VI and IV–VI crystals are described for prototype vertical SSVG systems. Finally, future prospects for the SSVG method in terms of further developments to the method, and the specific materials that will benefit from it are highlighted.     

静电场对V型火焰法中碳纳米管定向生长的影响

针对V型火焰实验系统的特点,考察了在种不同的静电场引入方式,以及在5V、30V和150V三种偏置电压下碳纳米管的定向生长情况.对实验结果进行了SEM、TEM表征,验证了静电场对碳纳米管定向生长的诱导作用,同时发现在一定范围内,随着偏置电压的增人,碳纳米管的准直性生长越明显.     

水热体系中不同前驱物对合成镁铝水滑石微结构的影响

以不同的镁源、铝源组合为前驱物,利用XRD、SEM及EDS比较研究了水热体系中不同的前驱物组合对合成镁铝水滑石(Mg-Al-LDHs)晶体微结构及晶体生长的影响,同时利用生长基元的配位体理论对其生长机理进行了初步探讨.研究结果表明:当固定体系的pH =12,水热温度120℃、水热时间18h的条件下,不同的前驱物组合均可以合成结晶度较好的镁铝水滑石晶体;但不同的镁源、铝源组合对产物的物相、分散性、结晶规整性、厚径比、纯度、大小及微结构有一定的影响.当镁源固定为MgCl2,铝源分别为Al2O3、Al(NO3)3、AlCl3时,不溶性氧化铝合成的LDHs规整性、分散性及纯度较差,晶体发育不完整;当铝源分别为溶解度较好Al(NO3)3、AlCl3时,合成产物LDHs晶体的结晶度、规整性、分散性及纯度较好,但由于溶解度和相连阴离子极性的不同,造成产物微结构的微小差异;当镁源固定为溶解度较大的Mg(NO3)2时,铝源分别为Al(NO3)3、AlCl3时,同溶解度较小MgCl2相比,更有利于合成结晶度、规整度、尺寸更小的镁铝水滑石晶体.溶解度较大的镁源、铝源前驱物组合合成的镁铝水滑石有更高的结晶度和规整度.EDS分析证实,溶解度较差的Al2O3合成的镁铝水滑石纯度较差.溶解度较好的不同镁源、铝源前驱物组合合成的镁铝水滑石不含有任何其它阴离子杂质,平均镁铝比约为3,非常接近LDHs的理论值.     

Effects of CaO on crystallization properties in BaO-SrO-TiO2-SiO2 glass-ceramics

The role of calcium oxide (CaO) was investigated in the crystallization of BaO-SrO-TiO₂-SiO₂ glass. The CaO dopant altered the oriented growth facets of crystal unit cells in the glass-ceramics. The crystallites are acicular in micron scale in the samples having as small as 1% CaO dopant, but are long granular in the nanometer scale in the sample without CaO. The glass-ceramics which have nano crystallites are observed with a less crystallization density qualitatively, a higher transmissivity in the wavelength range of 200-2600 nm, and 30% lower piezoelectric coefficient, d₃₃, at 9.5 ± 0.3 pC/N than those glass-ceramics having CaO in the study.     

Fe3+对KDP晶体生长影响的研究

金属离子对KDP晶体的影响是多方面的.本文采用不同的过饱和度,在不同的Fe3+掺杂浓度的生长溶液中生长KDP晶体,定量地研究了Fe3+对KDP晶体生长的影响.实验发现,无论是在高过饱和度还是在低过饱和度下生长KDP晶体,在一定的浓度范围内,Fe3+的掺入既可以增加生长溶液的稳定性,又可以有效抑制晶体柱面的扩展,而且晶体基本不楔化,同时,对晶体光学性能的影响也不大.