Flux confinement by artificial arrays and clusters in superconducting films

We have studied the superconducting properties of antidot arrays and mesoscopic antidot clusters near the superconducting-normal phase boundary. Characteristic minima and maxima have been observed in the magnetore-sistance, critical current and phase boundary caused by the formation of stable vortex configurations at the antidots. A comparison with a simple theoretical model has shown that the effects in the arrays as well as in the clusters originate from quantization of the fluxoid at the antidots. This model has enabled an identification of all vortex configurations.     

溅射功率对Ge2Sb2Te5薄膜光学常数的影响

研究了溅射功率对Ｇｅ２Ｓｂ２Ｔｅ５薄膜的光学常数与波长关系的影响。结果表明,在波长小于５００ｎｍ的情况下,随溅射功率的增加非晶态薄膜的折射率ｎ先增加然后减小,消光系数ｋ则逐渐减小;在波长大于５００ｎｍ的情况下,随溅射功率的增加折射率ｎ逐渐减少,消光系数ｋ先减小后增加。对于晶态薄膜样品,在整个波长范围折射率ｎ随溅射功率的增加减小后增加,消光系数ｋ则逐渐减少。薄膜样品的光学常数,在长波长范围随波长变化较大,在短波长范围变化较小。讨论了溅射功率对Ｇｅ２Ｓｂ２Ｔｅ５薄膜的光学常数影响的机理。     

生长温度对Si基Ge量子点VLP-CVD自组织生长的影响

对利用超低压化学气相淀积技术在Ｓｉ上自组织生长Ｇｅ量子点的特征进行了研究,发现生长温度对Ｇｅ量子点尺寸分布和密度的影响不同于分子束外延的结果,这种现象与ＶＬＰ－ＣＶＤ表面控制反应模式有关,实验表明,选择适当的生长温度可以在Ｓｉ上自组织生长具有窄尺寸分布和高密度和Ｇｅ量子点。     

Si基富Ge含量Si1-x-yGexCy异质结构的热退火行为研究

研究了Si基富Ge含量的Si1-x-yGexCy异质结构的热退火地为,采用等离子体增强化学气相淀积（PECVD）法在Si(100）衬底上淀积一层厚度为170nm的Si1-x-yGexCy薄膜（x-0.7,y-0.15),并在其上覆盖－Ge层,将样品分别在650度和800度下进行N2氛围下热退火20min。用拉曼谱（Raman),俄歇电子能谱（AES）以及X射线光电子能谱XPS等方法对样品进行研究。研究结果表明,低温PECVD法生长的Si1-x-yGexCy薄膜是一种亚稳结构,Ge/Si1-x-yGexCy/Si异质结构在650度下呈现不稳定性,薄膜中的Ge,C相对含量下降,且在界面处出现Ge,C原子的堆积,经过800度下退火20min的样品中C 含量基本为0,Ge相对含量下降至约20％左右,且薄膜的组分比较均匀。     

一种新型Si电子束蒸发器的研制及其应用研究

我们成功地设计出一种新型的Si电子束蒸发器,并将它应用于Ge/Si(111)量子点的生长.由于采用悬臂式设计,它完全克服了高压短路的问题.电子束蒸发器的性能试验表明,稳定输出功率可以控制输出稳定的Si束流.应用这种电子束蒸发器可以在700 ℃,成功沉积出平整的单晶Si薄膜.进一步的试验表明,在这种缓冲层表面可以自组装生长出Ge量子点.     

Growth of Ge-Si nanowire heterostructures via chemical vapor deposition

The growth of Ge-Si and Ge-Si nanowire (NW) heterostructures was demonstrated via chemical vapor deposition. Due to the influence of interface energy, differing topographies of the heterostructures were observed. On initially grown Ge NWs, numerous Si NW branches were grown near the tip due to Au migration. However, on initially grown Si NWs, high-density Ge nanodots were observed.     

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.     

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.     

微量Ge对Sn-0.7Cu高温钎焊界面组织的影响

测试了Sn-0.7Cu和Sn-0.7Cu-0.012Ge钎料在不同钎焊温度下的润湿性,研究了Ge元素对老化过程中钎焊界面金属间化合物(IMC)层生长速率的影响。结果表明:2种钎料的润湿性相差不大,但添加了Ge元素的Sn-0.7Cu-0.012Ge钎料在不同钎焊温度下的漫流性得到了明显的改善,相应提高了约4.00%~5.00%;250℃和350℃钎焊温度下,Sn-0.7Cu/Cu钎焊界面IMC在150℃的老化条件下的生长速率分别为3.24×10-18m2/s和2.50×10-17m2/s,Sn-0.7Cu-0.012Ge/Cu钎焊界面IMC的生长速率分别为2.66×10-18m2/s和1.48×10-17m2/s。Ge元素在钎焊界面处富集,提高了界面IMC的致密性,阻碍了原子的扩散,在一定程度上抑制了界面IMC层的粗化与增厚。     

Growth and characterization of GaAs films deposited on Ge/Si composite substrates by metalorganic chemical vapor deposition

We report the results of studies which have been made on heteroepitaxial layers of GaAs and AlGaAs grown by metalorganic chemical vapor deposition on composite substrates that consist of four different types of heteroepitaxial layered structures of Ge and Ge-Si grown by molecular beam epitaxy on (100)-oriented Si substrates. It is found that of the four structures studied, the preferred composite substrate is a single layer of Ge ∼1 μm thick grown directly on a Si buffer layer. The double-crystal X-ray rocking curves of 2 μm thick GaAs films grown on such substrates have FWHM values as small as 168 arc sec. Transmission electron micrographs of these Ge/Si composite substrates has shown that the number of dislocations in the Ge heteroepitaxial layer can be greatly reduced by an anneal at about 750° C for 30 min which is simultaneously carried out during the growth of the GaAs layer. The quality of the GaAs layers grown on these composite substrates can be greatly improved by the use of a five-period GaAs-GaAsP strained-layer superlattice (SLS). Using the results of these studies, low-threshold optically pumped AlGaAs-GaAs DH laser structures have been grown by MOCVD on MBE Ge/Si composite substrates.