LPEGaAs／Ga_（1－X）A1_xAs多层光阴极材料均匀性研究

用ＬＰＥ法生长了表面光亮、性质均匀的Ｐ－Ｇａ＿（１－ｘ）Ａ１＿ｘＡｓ／ｐ－ＧａＡｓ／ｐ一Ｇａ＿（１－ｘ）Ａ１＿ｘＡｓ／ｎ－ＧａＡｓ（衬底）多层异质材料；研究了材料的电学性质、掺杂剂分配，探讨了外延层的厚度均匀性、组份均匀性并观察了表面形貌。结果表明上述材料可用于制备第三代光阴极。     

LPE GaAs／Ga1—xAlxAs多层光阴极材料均匀性研究

用ＬＰＥ法生长了表面光亮、性质均匀的ｐ－Ｇａ１－ｘＡｌｘＡｓ／ｐ－ＧａＡｓ／ｐ－Ｇａ１－ｘＡｌｘＡｓ／ｎ－ＧａＡｓ（衬底）多层异质材料；研究了材料的电学性质、掺杂剂分配，探讨了外延层的厚度均匀性、组份均匀性并观察了表面形貌。结果表明上述材料可用于制备第三代光阴极。     

LPE法GaAlAs／GaAs多层光阴极材料的研制与性质

应用ＬＰＥ法成功地制出了Ｇａ＿（１－ｘ）Ａｌ＿ｘＡｓ／ＧａＡｓ多层结构材料，讨论了生长过程中铝、锗等元素的行为，测量了载流子浓度分布、少子扩散长度等电学性质，井观察了材料表面形貌。     

MOCVD法制备GaSb,GaAsSb,AlGaSb和AlGaAsSb异质外延材料

本文报导了用常压ＭＯＣＶＤ技术在ＧａＡｓ衬底上生长ＧａＳｂ、ＧａＡｓＳｂ、ＡｌＧａＳｂ和ＡｌＧａＡｓＳｂ异质外延材料的实验结果。研究了生长条件和材料质量的相互关系，优化了生长参数。首次采用组分缓变过渡层和超晶格结构来解决品格失配问题，利用ＳＥＭ和光学显微镜、Ｘ射线衍射仪、电子探针等测量、分析了外延层结构与组分、表面与断面形貌及其电学性质。测得ＧａＳｂ６／ＧａＡｓ结构中非有掺杂ＧａＳｂ层的Ｘ射线双晶摆曲线半峰小于１５０孤秒，霍尔迁移率μ＿ｐ（３００ｋ）＞６２０ｃｍ￣２／Ｖ·８，载流子浓度小于１×１０￣１６ｃｍ￣（－３），接近同质外延水平．     

Gd—Al—Dy系磁致冷材料的研究

用粒子排列烧结法制备了（Ｇｄ１－ｘＤｙｘ）３Ａｌ２系功能材料。研究了化学配位数ｘ分别为０和０１的二层（Ｇｄ１－ｘＤｙｘ）３Ａｌ２系合金。结果表明，（Ｇｄ１－ｘＤｙｘ）３Ａｌ２系化合物随着ｘ的增加，其居里温度Ｔｃ逐渐降低，二层梯度材料有与各单层相似的二个Ｔｃ，磁熵变化ΔＳｍ随温度Ｔ的变化平缓，因此，改善了材料的磁致冷性能。     

二次电子成分衬度成像方法在异质结半导体材料和器件的微结构研究中的应用

阐述了高分辨二次电子成分衬度像的成像原理、成像条件和实验方法，介绍了一种新的试样制备方法，讨论了各种制样方法的特点。以多层Ｐ＋Ｓｉ１－ｘＧｅｘ／ｐＳｉ异质结内光发射红外探测器为例，介绍了二次电子成分衬度像观察技术在异质结半导体材料和器件微结构研究中的应用。将这种技术与通常的透射电子衍射衬度方法进行了比较，讨论了它在异质结半导体材料和器件中的应用前景。     

二次电子成分衬度成像方法在异质结半导体材料和器件的微结构研究中 …

阐述了高分辨二次电子成分衬度像的成像原理，成像条件和实验方法，介绍了一种新的试样制备方法，讨论了各种制样方法的特点。以多层Ｐ＾＋－Ｓｉ２１－ｘＧｅｘ／ｐ－Ｓｉ半异质结内光发红外探测器为例，介绍了二次电子成发衬度像观察技术在异质结半导体材料和器件微结构研究中的应用。将这种技术与通常的透射电子衍射衬度方法进行了比较，讨论了它在异质结半导体材料和器件中的应用前景。     

Fe-Si合金系的机械合金化研究

采用高能行星球磨的方法研究了成分为ＦｅｘＳｉ１－ｘ（ｘ＝０．３０～０．７５）的纯元素混合粉末的机械合金化过程。对球磨不同时间粉末的结构分析和组织观察表明：Ｆｅ７５Ｓｉ２５粉末经球磨形成具有ｂｃｃ结构的纳米晶α固溶体，此α固溶体的晶粒尺寸和晶格常数随球磨时间的延长而减少。Ｆｅ５０Ｓｉ５０粉末的球磨产物为单相ＦｅＳｉ化合物，而Ｆｅ３０Ｓｉ７０混合粉末的球磨产物为α＋ＦｅＳｉ＋β－ＦｅＳｉ２三相混合结构。在研究的成分范围内无非晶化发生，对此进行了热力学分析。     

半导体碳化硅的研究现状与应用前景

综述了碳化硅的结构，性能与应用现状，讨论了原子层外延法生长β－ＳｉＣ薄膜及液相外延法制备蓝色α－ＳｉＣ发光管工艺；展望了半导体碳化硅材料的发展前景。     

Fe—P—C—Cu—Mo—Si非晶材料的晶化动力学

用不同加热速度下差热扫描量热卡计研究了Ｆｅ７９．５Ｐ１８－ｘＣｘＣｕ０．Ｍｏ０．５Ｓｉ１．５非晶材料的晶化动力学。实验结果表明：磷Ｆｅ（ｂ．ｃ．ｃ）起始晶化温度升高。对Ｆｅ７９Ｐ１８－ｘＣｘＣｕ０．５Ｍｏ０．５Ｓｉ１．５非晶材料，随着碳含量增多含量的减少，ＤＳＣ曲线出现双峰，并且两峰峰值温差ΔＴ＝ＴＰ２－Ｔｐ１加宽。     

Acheivement of Nano-Scale SiGe Layer with Discrete Ge Mole Fraction Profile Using Batch-Type HVCVD

The strained Si grown on the relaxed SiGe-on-insulator C-MOSFET's is a promising device for the future system LSI devices with the design rule of sub-micron. The achievement of the discrete Ge mole fraction in the SiGe layer is a key engineering in low-temperature SiGe epitaxial growth using HVCVD. The pre-flow of GeH4 gas enhanced the Ge mole fraction and SiGe layer thickness. In addition, the Ge mole fraction and SiGe layer thickness increases with the gas ratio of GeH4/SiH4 + GeH4, process temperature, and gas flow time. However, the haze was produced if the Ge mole fraction is above 22wt%. The discrete-like Ge mole fraction with 22 wt% in 10 nm SiGe layer was obtained by the pre-flow of GeH4 for 10 s, the mixture gas ratio of GeH4/SiH4 + GeH4 of 67%, and the gas flow time for 150 s at the process temperature of 550 C.     

MnP_(1-x)M_x系列合金的磁热效应

研究了1∶1型MnP基系列合金MnP1-xMx(M=Si,Sb,Ge,Zn,Sn)(x=0,0.1)的结构及其磁热效应。室温X射线衍射表明该系列合金的主相结构均为正交MnP结构,空间群为Pnma。在用Ge,Sb,Zn,Sn作为替代元素的合金中存在少量第二相Mn5.64P3。磁性测量表明该系列合金MnP1-xMx(M=Si,Sb,Ge,Zn,Sn)(x=0,0.1)的存在由铁磁-顺磁的二级相变。其居里温度Tc分别为286,295,294,295,295K。通过磁化曲线计算了MnP1-xMx(M=Si,Sb,Ge,Zn,Sn)(x=0,0.1)合金的最大等温磁熵变-ΔSm,均在0.7～1.3J.kg-.1K-1之间。     

Investigation of SiGe-on-Insulator Novel Structure

SiGe-on-Insulator (SGOI) is an ideal substrate material for realizing strained-silicon structures that are very competing and popular in present silicon technology. In this paper, two methods are proposed to fabricate SGOI novel structure. One is modified Separation by Implantation of Oxygen (SIMOX) starting from pseuodomorphic SiGe thin film without graded SiGe buffer layer. Results show that two-step annealing can improve the cystallinity quality of SiGe and block the Ge diffusion in high temperature annealing. SGOI structure with good quality has been obtained through two-step annealing. The second method is proposed to achieve SGOI with high content of Ge. High quality strained relax SiGe is grown on a compliant silicon-on-insulator (SOI) substrate by UHCVD firstly. During high temperature oxidation,Ge atoms diffuse into the top Si layer of SOI. We successfully obtain SGOI with the Ge content of 38%, which is available for the growth of strained Si.     

Validation of predicted precipitate compositions in Al-Si-Ge

Aged alloys of Al-0.5Si-0.5Ge (at. pct) contain diamond-cubic-A4 precipitates in a dispersion that is much finer than is found in alloys with Si or Ge alone. To help understand this aging behavior, the present work was undertaken to determine alloy composition as a function of aging temperature. The composition was estimated theoretically using a CALPHAD approach, and measured experimentally with energy-dispersive spectroscopy (EDS) in a high-resolution electron microscope. Theory and experiment are in reasonable agreement. As the aging temperature rises, the precipitates become enriched in Si, changing from 50 at. pct in the low-temperature limit to about 80 at. pct Si as the temperature approaches 433 °C, the high-temperature limit of the precipitate field.     

Effects of Buffer Layer on Hetero-Epi-Growth of SiCGe on 6H-SiC

Growth of SiCGe ternary alloy on 6H-SiC in a conventional hot-wall CVD system was initially studied. SiH4, GeH4 and C3H8 were employed as silicon, germanium and carbon source, respectively, while H2 was employed as the carrier gas. To reduce the heavy lattice mismatch between the film and the substrate, a 3C-SiC buffer layer was inserted between them in a CVD process. Optimizing the growth conditions was discussed. The samples were measured by means of SEM, SAXRD (Small Angle X-Ray Diffraction). It is shown that use of the 3C-SiC buffer layer is an effective way to improve the quality of the ternary alloy.     

MnFe1-xTixP0.63Ge0.12Si0.25（x=0,0.01,0.02,0.03）系列化合物的磁热效应

通过X射线衍射分析(XRD)和振动磁强计(VSM)磁性测量,研究了替代元素Ti替代Fe元素含量的MnFe1-xTixP0.63Ge0.12Si0.25(x=0,0.01,0.02,0.03)系列化合物的物相结构与磁热效应的影响。结果表明:该系列化合物的结构为Fe2P型六角晶系结构,空间群为P62m。主相均为(Mn,Fe)2(P,Ge,Si),并含有少量的第二相(Mn,Fe)3Si相。随着Ti原子替代Fe原子的增加化合物的晶格常数a增大,晶格常数c略有减小,晶胞体积V基本保持不变。随着Ti含量增加居里温度(TC)减小,热滞ΔThys的大小改进不太明显。MnFeP0.63Ge0.12Si0.25的TC为305 K,当外磁场变化为0～1.5 T时最大磁熵变的绝对值为14.8 J.(kg.K)-1。     

Gd2O3-HfO2栅介质薄膜的外延制备及Ge-MOS电学特性分析

以Gd2O3-HfO2( GDH)固溶氧化物作为靶材,采用脉冲激光沉积技术(PLD)在Ge(100)衬底上制备了GDH高k栅介质外延薄膜,其外延生长方式为“cube-on-cube”,GDH薄膜与Ge(100)衬底的取向关系为(100)GDH∥(100)Ge和[110] GDH∥[110]Ge.通过反射式高能电子衍射(RHEED)技术研究了激光烧蚀能量和薄膜沉积温度对薄膜晶体结构的影响,分析了二者与薄膜的取向关系,激光烧蚀能量对薄膜取向影响更为显著.得到较优的GDH外延薄膜沉积工艺为:激光烧蚀能量为3 J·cm-2、薄膜的沉积温度为600℃.用磁控溅射制备了Au/Ti顶电极和Al背电极,其中圆形的Au/Ti电极通过掩膜方法获得,直径为50μm.采用Keithley 4200半导体测试仪对所制备Au/Ti/GDH/Ge/Al 堆栈结构的Ge-MOS原型电容器进行电学特性分析,测试条件为:I-E测试的电场强度0～6MV·cm-1,C-V测试的频率300 kHz～1 MHz,结果表明,厚度为5nm的GDH薄膜具备良好介电性能:k-28,EOT ～0.49 nm,适于22 nm及以下技术节点集成电路的应用.     

Discussion of “Effect of Strontium and Phosphorus on Eutectic Al-Si Nucleation and Formation of <Emphasis Type="Italic">β</Emphasis>-Al<Subscript>5</Subscript>FeSi in Hypoeutectic Al-Si Foundry Alloys”*

The nucleation of Si during the solidification of Al-Si hypoeutectic alloys appears to result from a hierarchy of nucleating substrates operating at progressively lower temperatures: (1) AlP, whose generally particulate morphology can initiate the formation of compact Si particles as seen in hypereutectic alloys; (2) oxide bifilms alone, whose planar form creates platelike Si morphologies; and (3) a currently unknown nucleant that initiates the coral eutectic growth morphology. The consequential growth forms are particulate when initiated on particles and coarse (unmodified) plates when initiated on oxide films. However, when oxide films are deactivated by Sr, eutectic is forced to grow at a lower formation temperature with a consequently fine coral morphology known as “modified” Si. Increasing Sr additions progressively eliminate each substrate in turn to effect the change from the “unmodified” to the modified structure. *Y.H. CHO, H.-C. LEE, K.H. OH, and A.K. DAHLE: Metall. Mater. Trans. A, 2008, vol. 39A, pp. 2435–48. Discussion submitted October 6, 2008.     

Synthesis and photoluminescence properties of octahedral K_2(Ge,Si)F_6:Mn~(4+) red phosphor for white LED

A novel red-emitting K_2(Ge,Si)F_6:Mn~(4+) phosphor with uniform morphology was synthesized by co-precipitation method. The pure K_2GeF_6 phase with P63 mc space group other than P3m1 space group was affirmed just by incorporation of Si in K_2GeF_6 at room temperature according to XRD characterization. SEM images showed lamellar and octahedron grain morphology for K_2GeF_6:Mn~(4+) and K_2(Ge,Si)F_6:Mn~(4+) phosphors, respectively. It was also found that the photoluminescence excitation(PLE) and photoluminescence(PL) showed slight displacement in K_2GeF_6:Mn~(4+) and K_2(Ge,Si)F_6:Mn~(4+) system. And the zero-phonon line(ZPL) of the PL spectrum of K_2GeF_6:Mn~(4+) with Si showed a strong peak. Meanwhile crystalline field surrounding Mn~(4+) changes could affect the decay time in this fluoride system. The color gamut of the LED devices based on K_2(Ge,Si)F_6:Mn~(4+) and K_2GeF_6:Mn~(4+) reached up to 94.58% NTSC(National Television Standards Committee) and 94.386% NTSC, respectively, that was much higher than that based on nitride red phosphors. All these original characteristics in K_2(Ge,Si)F_6:Mn~(4+) phosphor are desirable for potential applications as a red phosphor for improving lighting and display quality of conventional white LEDs.     

New frontiers in thin film growth and nanomaterials

This article reviews recent developments in thin film growth and formation of three-dimensional epitaxial nanostructures. First, we present a unified standard model for thin film epitaxy, where single-crystal films with small and large lattice misfits are grown by a new paradigm of domain matching epitaxy (DME). We define epitaxy as having a fixed orientation rather than the same orientation with respect to the substrate. The DME involves matching of integral multiples of lattice planes (diffracting as well as nondiffracting) between the film and the substrate, and this matching could be different in different directions. The idea of matching planes is derived from the basic fact that during thin film growth, lattice relaxation involves generation of dislocations whose Burgers vectors correspond to missing or extra planes, rather than lattice constants. In the DME framework, the conventional lattice matching epitaxy (LME) becomes a special case where matching of lattice constants results from matching of lattice planes with a relatively small misfit of less than 7 to 8 pct. In large lattice mismatch systems, we show that epitaxial growth of thin films is possible by matching of domains where integral multiples of lattice planes match across the interface. We illustrate this concept with atomic-level details in the TiN/Si(100) with 3/4 matching, the AlN/Si(100) with 4/5 matching, and the ZnO/α-Al₂O₃(0001) with 6/7 matching of lattice planes across the film/substrate interface. By varying the domain size, which is equal to the integral multiple of lattice planes, in a periodic fashion, it is possible to accommodate additional misfit beyond the perfect domain matching. Thus, we can potentially design epitaxial growth of films with any lattice misfit on a given substrate with atomically clean surfaces as long as there is wetting or finite interatomic interaction across the interface and cores of dislocations do not overlap. In-situ X-ray diffraction studies on initial stages of growth of ZnO films on sapphire correctly identify a compressive stress and a rapid relaxation within one to two monolayers, consistent with the DME framework and the fact that the critical thickness is less than a monolayer. The DME examples ranging from the Ge-Si/Si(100) system with 49/50 matching (2 pct strain) to metal/Si systems with 1/2 matching (50 pct strain) are tabulated, strategies for growing strain-free films by engineering the misfit to be confined near the interface are presented, and the potential for epitaxial growth of films with any lattice misfit on a given substrate with atomically clean surfaces is discussed. In the second part, we discuss the formation of epitaxial nanodots/nanocrystals in crystalline matrices such as MgO and TiN. The formation Ni nanocrystals inside MgO involves lattice misfit ranging from 3.0 to 31.3 pct, and the formation of Ni nanocrystals in TiN has a misfit of about 17 pct. To form epitaxial nanodots, we use DME framework to grow nanodots inside crystalline matrices. Growth characteristics and crystallography of nanodots are controlled to enhance the overall properties of nanostructured materials. We illustrate this for nanostructured magnetic materials where coercivity and blocking temperature can be considerably enhanced by controlling the orientation for magnetic memory and storage applications, among others. In the last part, the DME principles are applied to grow self-assembled epitaxial nanodots using pulsed laser deposition. By controlling the clustering kinetics, it is possible to obtain a uniform distribution of epitaxial nanodots and overcome thermodynamically driven Ostwald ripening. This process allows the formation of epitaxial nanostructures via three-dimensional self-assembly, the “holy grail” of nanostructured materials processing, leading to unique and novel properties. Jagdish (Jay) Narayan holds The John C.C. Fan Family Distinguished Chair Professorship and is Director of the NSF Center for Advanced Materials and Smart Structures at North Carolina State University. The Edward DeMille Campbell memorial lecture entitled, “New Frontiers in Thin Film Growth and Nanomaterials,” was delivered at the Annual ASM International Meeting (October 17–20, 2004) in Columbus, Ohio. Professor Narayan received his M.S. (1970) and Ph.D. (1971) degrees in a record time of two years from the University of California, Berkeley, after his Bachelor’s of Technology with Distinction and Highest Honors from IIT, Kanpur in 1969. Professor Narayan has had a profound impact on our understanding of defects and interfaces in thin film heterostructures, laser-solid interactions and processing of novel materials, controlled thin film growth and self-assembled nanostructures, and nanoscale characterization and modeling of new materials and properties. He invented novel supersaturated semiconductor alloys formed by solid phase epitaxy, and by liquid-phase crystallization where melt-quenching rates are billions of degrees per second. This research, featured twice in Science Magazine, has resulted in numerous U.S. patents and three IR-100 Awards. More recently, Narayan has pioneered and patented a new concept of domain epitaxy, where an integral number of lattice planes of the film match that of the substrate in large lattice mismatched systems. The domain epitaxy is key to the formation of thin film heterostructures, such as TiN films on silicon with 4/3 matching, and III-nitrides and ZnO films on sapphire with 6/7 matching. Narayan invented new cubic ZnMgO alloys, which can be grown epitaxially on silicon (100) substrates for integrating optoelectronic and spintronic devices. Narayan discovered and patented a new method of self-assembly for processing nanostructured magnetic, photonic, electronic, and structural materials. His discoveries with Dr. John Fan, Kopin Corporation, related to domain epitaxy and quantum confinement by thickness variation (creating nanopockets) are being used by Kopin Corp. to manufacture high-efficiency light emitting diodes for solid-state lighting. He has published over 800 scientific articles, edited 9 books, and received 22 patents pertaining to novel materials and processing methods, domain epitaxy, and a new class of next-generation semiconductor alloys. He is a Fellow member of APS, AAAS, ASM International, TMS, and MRS-I. He has won numerous other honors, including three IR-100 Awards and a 1999 ASM Gold Medal. He also received Distinguished Alumnus Honors from IIT/K in 1997.