硅/锗量子点空间分布的有序性及其制备技术

随着纳米技术的进步,量子点纳米材料在理论和实验研究方面受到越来越多的关注.由于量子点阵列优异的物理性能与其空间分布的有序性十分相关,空间分布有序量子点阵列的大面积重复性制备已成为高性能纳米光电子器件商业化应用的关键.近几十年来,在量子点空间排列分布有序性的提高、缺陷态的减少、成核位置可控以及大面积重复制备方面人们已做了大量研究.本文主要讨论和综述当前在制备空间分布有序硅/锗(Si/Fe)量子点方面的技术工艺和成果,并展望其未来技术发展思路和方向,希望为今后进一步探索研究大面积空间分布有序Si/Ge量子点阵列的制备提供信息参考.     

低磁场条件下Mn5(Ge3-xSbx)(x=0、0.1、0.2、3)合金磁热效应研究

用真空高频悬浮炉在高纯氩气保护下制备了Mn5（Ge3-xSbx）（x=0、0.1、0.2、3）合金系列样品,用直接测量方法测定了在永磁体提供的低磁场（H=1.3T）条件下样品的磁热效应曲线（ΔTad-T）,结果表明,用元素Sb替代Mn5Ge3合金中的Ge原子,不能增强合金的磁热效应,但对合金的居里温度有一定影响.     

Orientation control of epitaxial Ge thin films growth on SrTiO3 (100) by ultrahigh vacuum sputtering

We report the orientation control of crystalline Ge (111) and Ge (001) growth on SrTiO₃ (100) substrate by adjusting the temperature of substrate. It is found that the substrate temperature plays an important role for the formation of crystalline Ge with different surface orientations and interfacial chemical configuration during the sputtering process. At 500 °C, Ge (111) with good crystalline quality is formed, while Ge (001) is preferably grown on SrTiO₃ substrate at 650 °C. Our results show the possibility of manipulating the surface orientations during Ge growth on SrTiO₃ by controlling the substrate temperatures.     

Laser ablation and growth of Si and Ge

In this work, we investigated the laser ablation and deposition of Si and Ge at room temperature in vacuum by employing nanosecond lasers of 248 nm, 355 nm, 532 nm and 1064 nm. Time-integrated optical emission spectra were obtained for neutrals and ionized Ge and Si species in the plasma at laser fluences from 0.5 to 11 J/cm². The deposited films were characterized by using Raman spectroscopy, scanning electron microscopy and atomic force microscopy. Amorphous Si and Ge films, micron-sized crystalline droplets and nano-sized particles were deposited. The results suggested that ionized species in the plasma promote the process of subsurface implantation for both Si and Ge films while large droplets were produced from the superheated and melted layer of the target. The dependence of the properties of the materials on laser wavelength and fluence were discussed.     

巨大晶胞化合物Ho117Fe52Ge112的结构磁性能研究

利用X射线衍射技术和振动样品磁强计（VSM）研究了巨大晶胞三元化合物Ho117Fe52Ge112的结构与磁性能,测定了外加磁场为0．5T时该化合物的磁矩随温度的变化关系。该化合物具有Tb117Fe52Ge112结构类型,空间群为Fm3m（No．225）点阵参数为a=2．80832（8）nm。在90K到室温的范围内,Ho117Fe52Ge112的磁化率与温度关系服从居里——外斯定律,每个化学式有效磁矩的实验值为ueff=111．25us。测定了室温（300K）时磁矩随外加磁场的变化关系。当外加磁场到2．1T时,该化合物的磁矩约为3．61emu／g,还没有达到饱和状态。     

Ambient stability of wet chemically passivated germanium wafer for crystalline solar cells

Surface passivation has been recognized as a crucial step in the evaluation of minority carrier lifetime of photovoltaic materials as well as in the fabrication of high efficient solar cells. Dilute acids of HF and HCl are employed for germanium (Ge) surface passivation. An effective lifetime of passivated Ge wafers has been evaluated by a microwave photoconductive decay (μ-PCD) measurement. Surface recombination velocities, S, of H- and Cl-terminated Ge surfaces are 23 and 37 cm/s, respectively. The stability of passivated Ge surfaces against exposure to air has also been examined. The HCl-passivated Ge surfaces are found to be more robust than HF-passivated surfaces.     

Si versus Ge for future microelectronics

The quest for higher performance of scaled down technologies resulted in the use of high-mobility substrates and strain engineering approaches. The development of advanced processing modules, based on low temperature processing and deposited (MBE, ALD, epitaxially grown, etc.) gate stacks, has triggered the interest of exploring Ge for sub 32 nm technology nodes. A comparison between Si and Ge for future microelectronics has to take into account a variety of materials, processing and performance aspects. Here special attention will be given to passivation and gate stack formation in relation to device performance, including leakage current and reliability aspects. The potential of Ge-based device structures and the monolithic integration of Ge and III-V devices on silicon are highlighted.     

应变影响下单晶Ge薄膜热导率分析

利用非平衡态分子动力学模拟方法研究了应变对Ge薄膜热导率的影响。结果表明系统应变对单晶Ge薄膜热导率产生明显影响,热导率随着拉伸应变的增大而减小,随着压缩应变的增大而增大,得出声子速率降低以及薄膜表面重构是产生该模拟结果的内在原因。同时,采用修正的Callaway模型对NEMD结果进行理论验证,两种方法得到的结果吻合得较好。理论结果表明应变弛豫时间对Ge单晶薄膜的热导率产生了重要影响。     

董志塬区黄土高填方地基工后沉降特性试验研究

黄土高填方地基工后沉降量大,容易引起建筑物开裂破坏。本文以庆阳市西峰区某小区填沟造地项目为背景,对董志塬区黄土高填方地基的工后沉降特性进行了分析研究,研究结果表明,⑴黄土高填方地基在回填后200天到250天左右工后沉降量较大,最大沉降量可达到79cm。⑵黄土高填方地基工后沉降在沟谷处较大,距离沟谷越远,沉降量越小。⑶干密度是影响黄土高填方地基工后沉降的主要因素,可以通过提高干密度的方法提高黄土的回填质量,对于超厚的黄土高填方地基,宜采用高能级强夯进行分层回填。     

N型和P型Si80Ge20合金制备及热电性能

对N型Si80Ge20(P4)x及P型Si80Ge20Bx固溶体合金的化学计量比进行了研究,采用已总结出的最佳工艺条件,制备了一系列N型、P型固溶体合金,并比较了各系列样品的热电性能.结果表明,x=1.5的N型Si80Ge20(P4)x固溶体合金具备良好的热电性能,与未掺杂Si80Ge20固溶体合金相比,最高热电优值ZT为0.651,提高了3.34倍.x=1.5的P型Si80Ge20Bx固溶体合金也具备较佳的热电性能,最高热电优值(ZT)值为0.538.