The dependence of the microstructure and thermoelectric properties of germanium-doped higher manganese silicide crystals

The reason why manganese monosilicide inclusions are formed during the growth of higher manganese silicide (HMS) crystals has not been studied in detail so far. Changes in the amount and density of these inclusions are greatly influenced by dopants. In this study, the structure of HMS crystals with various contents of germanium as a doping element is examined. It is found that raising the germanium content to 1 at % results in the fragmentation of layered manganese monosilicide inclusions and, simultaneously, leads to significant changes in the thermoelectric properties of HMS crystals. The results of the microstructural analysis of HMS crystals in relation to the germanium concentration may be of use for understanding the mechanism by which the manganese monosilicide phase is formed during the growth of higher manganese silicide crystals.     

Observation of iron silicide formation by plan-view transmission electron microscopy

The formation and the phase transitions of iron silicide by solid-phase epitaxy have been investigated by means of plan-view transmission electron microscopy, which enables us to observe a clean interface between Fe and Si. Layers of Fe were deposited on Si (100) at room temperature in an ultrahigh vacuum chamber. The sample was annealed in the electron microscope at a temperature between 673 and 1073 K. After annealing at 673 K, FeSi crystallites were formed with various orientations. When the annealing temperature was increased to 973 K, we found that the crystallites suddenly started to coalesce into grains of several hundreds of nanometers in size and polycrystalline beta-FeSi2 was formed. These phase transitions were also confirmed with electron energy-loss spectroscopy.     

Structure and property of magnetron sputtered ternary cobalt-nickel silicide films

Ternary cobalt-nickel silicide films were prepared using magnetron sputtering from an equiatomic cobalt-nickel alloy target on Si substrate. The effect of post-deposition annealing on the phase formation, structural properties and resistivity of the resultant films has been studied. The results of XRD show that the annealing temperature and impurity level of oxygen play a crucial role in controlling the phase transformation of ternary silicide. Silicide phases are absent in the as-deposited film due to the amorphous nature. At relatively low annealing temperature, the phase of CoNi₃Si (2 2 0) and CoNiSi (2 2 0) coexist. With the increase of annealing temperature, the phase of CoNi₃Si (2 2 0) begins to transform into CoNiSi (2 2 0). At high annealing temperature (800 °C), only the phase of CoNiSi₂ (2 2 2) is formed. For Co-Ni silicide film annealed in pure argon gas ambient, two Raman peaks at 1357 cm⁻¹ and 1591 cm⁻¹ are attributed to the vibrational mode of CoSi₂ and NiSi₂ compounds. For ternary silicide annealed in atmosphere ambient, two Raman peaks located at 538 cm⁻¹ and 690 cm⁻¹ were observed and may be related to Si oxide or Co-Ni oxide. The 3D views of AFM images show that the surface roughness is relatively low when the silicidation temperature is smaller than 550 °C. After silicidation in 800 °C, the surface roughness increases abruptly. The resistance initially decreases with the increase of annealing temperature, and achieves minimum value (19 μΩ cm) in temperature ranges 500-550 °C. When the annealing temperature increases from 600 °C to 800 °C, the resistivity was found to increase slightly to 26 μΩ cm. The ternary silicide shows a temperature window for low resistivity as compared to binary NiSi.     

单晶硅摩擦致相变的SEM研究

自从Jamieson发现单晶硅的高压相变现象以来，有关单晶硅的高压相变的研究逐步开展起来，其最终目的之一就是通过金属延性相的出现来解决单晶硅的加工问题。Pharr、Gogotsi、zhang liangchi等人利用纳米压入技术系统研究了单晶硅的压力致相变问题。本文旨在研究单晶硅在滑动摩擦过程中的相     

Processing of titanium films on silicon using a multiscanned electron beam

A multiscanned electron beam has been used to process titanium films thermally on single-crystal silicon. The redistribution of titanium and the composition of the processed films were studied by Rutherford backscattering. Oxygen contamination within the titanium is found to control the reaction rate. Processing conditions have been established which give stoichiometric TiSi2 layers and the removal of oxygen from the system. These results have been confirmed by Auger analysis and the surface texture has been examined using scanning electron microscopy.     

Control of island formation on silicon surfaces using ultra-high-vacuum scanning electron microscopy

In situ scanning electron microscopy has been used to control Au island formation on a patterned Si(111) surface with a periodic array of atomic-step bunches and holes. Liquid phase Au-Si islands were observed to redistribute on the patterned surface by annealing. The islands accumulate at a particular position of the step bunch in each pattern unit. This phenomenon is interpreted in terms of the energetic stability of a droplet on a patterned surface.     

Infrared spectroscopy and transmission electron microscopy of polycrystalline silicon carbide

The polycrystalline structure of silicon carbide was investigated by infrared spectroscopy and transmission electron microscopy (TEM). The films were obtained by annealing in the temperature range 950–1250°C of amorphous silicon carbide films deposited on a silicon substrate by PECVD. The broad absorption band at around 750 cm⁻¹ in the infrared spectrum of amorphous material after annealing at high temperature changes from a Gaussian to a Lorentzian shape, corresponding to the transition from an amorphous to a polycrystalline phase. The SiC peak becomes sharper with increasing the annealing temperature, this effect being related to the growth of crystalline grains. TEM microscopy indicates that the crystallisation occurs homogeneously in the films and the diffraction pattern shows that the film crystallises into cubic 3C–SiC. The distribution of polycrystalline grains as determined by TEM evidences an increase of the grain size with increasing the annealing temperature. A correlation between infrared peak width and mean grain radius has been found.     

Investigation of polycrystalline silicon layers by electron microscopy and x-ray diffraction

The structure of polycrystalline Si layers deposited by pyrolysis of silane in a hydrogen ambient has been investigated by replica electron microscopy and X-ray diffraction. When the gas flow ratio (SiH₄/H₂) is 3·64 × 10⁻⁴ the temperature region below 900°C is a surface reaction control region and the activation energy of the chemical surface reaction rate is 1·6 eV. The temperature range above 900°C is a mass transfer region and the deposition rate is about 500 Å/min. The grains become larger and the texture of the surface of the poly Si layers becomes coarser with the deposition temperature. Some phase change was found to occur around 900°C by replica electron microscopy. The X-ray diffraction experiments show that there exist three preferred orientations of (220), (111) and (311) in the poly Si layers. The decrease of the relative intensity of the (311) orientation might have a relation to the phase change around 900°C.     

金属纳米颗粒表面外延钝性氧化膜的透射电子显微学研究

Transmission electron microscopy study of nanoparticles of Fe, Cr, Ni, Co, Cu and stainless steel, prepared in Tianjin University and the Hong Kong University of Science and Technology, along the <001> and <110> zone axes has shown that they are passivated by epitaxial oxide films a few nanometer thick. There is a wide spread of mismatch between the shell oxide and the core metal, ranging from about 3% in Fe to 19% in Ni and Co. The morphology of the nanoparticlesand the structure of the oxide films depend on the passivation temperature and atmosphere, as well as the oxide metal mismatch.     

Transmission electron microscopy study of epitaxial passive oxide films on nanoparticles of metals

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二氧化硅超薄膜的扫描隧道显微镜和扫描隧道谱研究

用超高真空热氧化方法在Si(111)清洁衬底上生长了二氧化硅超薄膜，并利用超高真空扫描隧道显微镜和扫描隧道谱技术对超薄膜的表面形貌和局域电学特性进行了研究。结果显示，在超薄范围二氧化硅呈层状生长，不同层的微分电导谱所测禁带宽度差别可以达到约3eV，形貌对二氧化硅带宽的影响小于膜厚的影响。     

Grain boundary diffusion and growth of titanium silicide layers on silicon

A kinetics study of titanium silicide formation is described. The results show that a fine grained precursor layer exist in between the well developed C-54 silicide layer and the unreacted titanium film. This layer is a mixture of C49-TiSiV₂ and unreacted titanium. The fact that no C54-TiSi₂ formed directly from the Ti-Si reaction suggests that the nucleation of C49-TiSi₂ is easier than that of C54-TiSi₂ under our annealing conditions. The silicide layer growth has a non-t^1/2 dependence and is much better described by a grain boundary diffusion limited model giving different kinetics. This indicates that grain boundary diffusion is the major atomic transportation mechanism. The growth rate depends on both the grain boundary diffusion coefficient and the silicide grain growth rate.     

Scanning electron microscopy used to measure the feature dimensions of a nanoscale test pattern on a silicon surface

A method is proposed for nanoscale dimensional metrology with the scanning electron microscope in the case of an array of trapezoidal ridges on a silicon surface, the minimum feature size being comparable with the effective beam diameter. The method is tested by measuring the top width of an individual ridge, which lies between 14 and 24 nm. The method works at accelerating voltages higher than 15 kV.     

Transmission electron microscopy observations of low-temperature ion implanted (100) silicon

Phosphorus implantations have been performed at room temperature and near 77°K on (100) silicon wafers. It is shown that this low-temperature process is able to produce after furnace annealing doped layers completely free from the usual residual damage (mainly dislocation loops) that is observed in room temperature implanted and furnace annealed silicon.     

外延生长的Gd掺杂CeO2薄膜内位错的透射电子显微学表征

利用脉冲激光沉积（ pulsed laser depositon, PLD）方法在YSZ（ Y2 O3 stabilised zirconia）单晶衬底上外延生长了Gd掺杂的CeO2薄膜（gadolinium doped CeO2,GDC）。利用透射电子显微镜（TEM）对GDC／YSZ界面以及GDC薄膜内部的位错结构进行了表征。实验发现,界面处存在周期性分布的失配位错,界面失配主要通过失配位错释放。 GDC薄膜内部存在两种不同的位错,其中一种为纯刃型位错,另外一种为混合型位错。     

电子显微镜平台使用数据分析及管理建议

电子显微镜(以下简称电镜)在生命科学研究中起到了非常重要的作用。随着电镜使用需求的日益扩大,对仪器管理也提出了新的要求。本文利用北京大学生命科学学院仪器中心电镜平台2010年及2017年安装的两台透射电镜的使用数据,详细分析每台电镜的使用时间、使用时长以及相应的用户,并通过描述统计的方法,对这些数据进行分析与整合,包括电镜使用的日内分布、周内分布以及用户群体的变化等。统计得出北京大学生命科学学院电镜平台用户更倾向于在工作时间使用电镜,同时电镜使用的寡头垄断及用户偏好粘性现象明显。建议通过鼓励培训独立用户、合理设计管理者工作时间以及设置设备使用费梯度等方式提高电镜的使用率。     

电子束热蒸发非晶硅薄膜红外光学特性

采用Ar+离子束辅助电子束热蒸发技术制备非晶硅(a-Si)薄膜,利用正交实验研究了薄膜红外光学常数与工艺参数之间的关系.采用椭偏仪和分光光度计分析了薄膜沉积速率、基底温度和工作真空度对非晶硅薄膜的折射率和消光系数的影响.实验结果表明:影响a-Si薄膜光学特性的主要因素是沉积速率和基底温度,工作真空度的影响最小.随着沉积...     

Some experimental data on thin mixed films of silicon monoxide/germanium dioxide

Mixed amorphous films are of interest as electronic materials and materials based on silicon monoxide are under substantial investigation. Comparisons are made between SiO/GeO₂ and SiO/SnO₂ films. In general the electrical properties of the two series are similar but the optical properties demonstrate significant differences. The effect of SnO₂ addition has a greater effect on paramagnetic resonance than adding GeO₂.     

Observation of dislocations in a silicon phototransistor by scanning electron microscopy using the barrier electron voltaic effect

Silicon planar phototransistors crossed by slip planes were examined both by X-ray topography and by conductive mode scanning electron microscopy using the barrier electron voltaic effect current as video signal. Only a few of the dislocations visible in the topographs gave rise to contrast in the scanning electron micrographs. This observation of single dislocations by means of the barrier electron voltaic effect is particularly valuable for the study of the role of defects in device failure and production yields as it renders visible only the electrically effective defects. Quantitative analysis of the barrier electron voltaic effect short circuit current obtained on scanning across an electrically effective dislocation provides a new means for measuring the electrical properties of dislocations. Repeated scanning produced lines of enhanced contrast across the surfaces of the devices. These lines were visible in surface X-ray topographs. This observation is believed to be due to beam induced damage in the oxide and interface region.     

碳掺杂β-FeSi2薄膜的电子显微学研究

本文利用透射电子显微镜对离子注入合成的β-FeSi2和β-Fe(C,Si)2薄膜进行了对比研究.电镜观察结果表明,选择C作为掺杂元素,能够得到界面平直、厚度均一的高质量β相薄膜,晶粒得到细化,β-FeSi2层稳定性提高.尤其在60kV、4×1017ions/cm2条件下注入直接形成非晶,在退火后会晶化为界面平滑、厚度均匀的β-FeSi2薄膜.因此从微结构角度考虑,引入C离子有益于提高β-FeSi2薄膜的质量.