用氢钝化Si（100）面抑制分子束外延界面的硼尖峰

采用一种新的简便的氢钝化方法，可以在Ｓｉ（１００）衬底表面获得稳定的钝化层，用俄歇电子能谱，反射式高能电子衍射，Ｃ－Ｖ和二次离子质谱等方法对衬底表面及其上面生长的分子束处延层进行检测，发现这种方法可以有效地防止衬底表面被碳、氧沾污，降低退火温度至少２００℃，并完全消除处延层与Ｓｉ（１００）衬底界面处的高浓度硼尖峰，在此基础上，结合衬底表面锗束处理的实验结果，对硼尖峰的主要来源是由于硅衬底表面的氧化     

GaP衬底上分子束外延Si时P偏析的抑制

用Si分子束外延技术在GaP(111)衬底上生长Si时,发现Si外延层表面存在P偏析,根据俄歇电子能谱(AES),反射式高能电子衍射(RHEED)在一系列不同实验条件下的结果,本文对P偏析产生的机制、外延层表面再构与P偏析之间的关系作了分析和讨论,得出偏析主要来自外延Si原子与衬底P元素之间的相互交换。在此基础上提出了一种能有效地抑制P偏析同时又改善外延层质量的新的Si/GaP(111)异质结制备方法。 关键词：     

Si(100)表面Se薄膜生长及其在Ti/Si欧姆接触中的应用

本文采用分子束外延(MBE)系统在Si(100)表面淀积Se薄膜. 通过控制衬底和固态Se束源炉的温度,实现了Se材料在Si(100)表面上的自限制超薄薄膜生长;在Se超薄层钝化的Si(100)表面上制备的Ti金属电极具有低的欧姆接触电阻特性,且热稳定性温度提升至400 ℃. 关键词： 硒 钝化 欧姆接触 热稳定性     

Si衬底上分子束外延Ge,Si时的反射式高能电子衍射强度振荡观察

本文观察了在Si(100)和Si(111)衬底上分子束外延Si,Ge时的反射式高能电子衍射(RHEED)强度振荡现象。其振荡特性表明,外延一定厚度的缓冲层可以改善表面的平整性,较慢的生长速率或中断生长一段时间有利于外延膜晶体质量的提高。Si(100)上外延Si或Ge时,沿[100]和[110]方位观测到的振荡特性均为单原子模式,起因于表面存在双畴(2×1)再构;而Si(111)上外延Ge时,[112]方位观测到的振荡为双原子层模式,但在[110]方位观察到不均匀周期的强度振荡行为。两种衬底上保持RHEED     

湿法刻蚀对Si基片孔点阵及ZnO外延薄膜周期形貌的影响

利用射频等离子体辅助分子束外延法,在刻有周期性孔点阵结构的Si衬底上生长了ZnO二维周期结构薄膜,系统研究了湿法化学刻蚀对孔形点阵Si(100),Si(111)基片表面形貌的影响,以及两种初底上ZnO外延薄膜的结晶质量与周期形貌的差异.X射线衍射及扫描电子显微测试结果表明：Si (111)衬底上生长出的ZnO二维周期结构薄膜具有较好的结晶质量与较好的周期性表面形貌.该研究结果为二维周期结构的制备提供了一种新颖的方法. 关键词： ZnO 分子束外延 Si 湿法刻蚀     

在Si衬底上用分子束外延低温生长Ge薄膜

本文报道了室温下淀积的薄层Ge在Si衬底表面上通过加热形成结晶的Ge岛,然后在此“带结构”的衬底表面上用分子束外延(MBE)方法生长Ge薄膜的反射式高能电子衍射(RHEED),俄歇电子能谱(AES)研究结果。X射线双晶衍射的测试结果表明,衬底表面的Ge岛有助于释放外延层的失配应力,提高外延层的晶体质量。 关键词：     

高能电子衍射研究H钝化偏角Si衬底上Si,GexSi1-x的分子束外延生长模式

用高能电子衍射(RHEED)研究H钝化偏角Si衬底上Si,Ge_xSi_1-x材料的分子束外延(MBE)生长模式,发现经低温处理的H钝化Si衬底上要经过10nm左右的Si生长才能获得比较平整的表面.Si,Ge_xSi_1-x外延时的稳定表面均以双原子台阶为主,双原子台阶与单原子台阶并存的结构.Si双原子台阶上的Si二聚体列(dimerrow)取向垂直于台阶边缘,而Ge_xSi_1-x双原 关键词：     

Si(111)分子束外延生长时RHEED强度振荡的观察

本文报道用反射式高能电子衍射的强度振荡测量来观察Si(111)衬底上分子束外延的生长行为,观察到了双原子层的振荡模式。振荡的衰减和恢复特性不同于Si(100)衬底上的生长行为,而同GaAs分子束外延时的特性非常相似。 关键词：     

GS-MBE生长的GaP/Si的XPS研究

利用X射线光电子能谱(XPS)深度剖析方法对气体源分子束外延(GS-MBE)生长的GaP/Si异质结构进行了详细的分析.其结果表明:(1)外延层内Ga、P光电子峰与GaP相相符,且组份分布均匀,为正化学比GaP.(2)在不同富PH₃流量条件下生长的样品,其表面富P量稍有不同,而GaP外延层内的测试结果相同.界面也未见有P的富集.(3)XPS剖析至GaP/Si界面附近,随外延层界面向衬底过渡,Si2p光电子峰向高结合能方向移动,且其结合能高于原衬底p型Si,接近于n型Si.但Ga、P光电子峰未发现有明显能移.(4)在XPS检测限内,外延层内和界面都未见有C、O等沾污.这一研究表明:无污染的本底超高真空、相对过剩的富₃生长环境、成功的Si衬底清洗方法等措施保证了GS-MBE生长出正化学比GaP/Si外延异质结构.     

Au钝化Si(100)表面的电子特性

用TB-LMTO方法研究单层的Au原子在理想的Si(100)表面的化学吸附.计算了Au原子在不同位置的吸附能,吸附体系与清洁Si(100)表面的层投影态密度, 以及电子转移情况.结果表明, Au原子在吸附面上方的A位(顶位)吸附最稳定, Au钝化Si(100)表面可以取得明显的钝化效果, 这一结论与实验事实相符合.     

Influence of boron on the initial stages of Si molecular beam epitaxy on Si(1 1 1) studied by reflection high-energy electron diffraction

The influence of boron as a function of coverage on molecular beam epitaxial Si growth on Si(1 1 1) surface was systematically studied by reflection high-energy electron diffraction. At boron coverage above 0.3 monolayer regular oscillations occur with a period typically for two-bilayers, whereas at lower boron coverage a transient behaviour with irregular intensity oscillations was observed in the initial growth stages. This behaviour can be attributed to a superposition of a bilayer and a two-bilayer dominated growth mode. The appearance of these two growth modes is discussed in terms of an initial surface defect-induced nucleation of bilayer-high Si islands and the formation of two-bilayers-high Si islands on top of the van der Waals like boron-covered surface, respectively. We suggest that these surface defects are of intrinsic nature, and their number only depends on the amount of boron at the surface. The oscillations become regular during further Si deposition with a bilayer period, indicating a diminishing influence of the layer/substrate interface on the growth processes.     

Nucleation and growth during molecular beam epitaxy (MBE) of Si on Si(111)

The nucleation of Si on Si(111) has been studied during deposition in UHV by spot profile analysis of low energy electron diffraction (SPA-LEED). A new method of evaluation is developed by separating the measured spot profile into a central spike and a broad shoulder. The energy dependence of the fraction of the central spike out of the total diffracted intensity provides the vertical distribution of surface atoms over different levels. With this method it is shown that the first nucleation occurs in islands of double height. Only after deposition of several layers a layer-by-layer growth is found with a well defined nucleation of a new layer before the former one is completed.     

Si衬底上异质外延金刚石的初始阶段原子H的作用及其界面结构

用高分辨率电子能量损失谱方法研究了原子H与被C₂H₂吸附的Si(100)界面的相互作用.结果显示,在Si(100)界面上,Si—Si二聚化键和C₂H₂中的C—C键被H原子打开,它们分别形成Si—H,C—H键.用AM1量子化学方法,计算了C₂H₂和C₂H₄在Si(100)上的吸附结构,指出了C₂H_{2关键词：}     

Si(100)表面电子态的总电流谱研究

用自制的总电流谱仪研究了Si(100)2×1清洁表面以及H原子饱和吸附后的Si(100)1×1-2H双氢化相表面的电子态。在清洁表面上测得的空电子态位于价带顶以上0.7eV处,而占有电子态则在价带顶以下0.25,8.4和近12eV处。在双氢化相表面上还观测到处于价带顶以下两个诱导表面态。 关键词：     

FI-STM STUDY OF HYDROGEN ADSORPTION ON Si(100) SURFACE

Chemisorption of atomic hydrogen on the Si(100)2×1 surface has been investigated in detail by using a field ion-scanning tunneling microscope (FI-STM). The results showed that the adsorption geometry changed from the 2×1 monohydride phase to the 1×1 dihydride phase with increasing exposure of hydrogen. The data of desorption of the hydrogen-saturated Si surface showed that on annealing at 670K the surface becomes highly disordered: the 1×1 dihydride structure is eliminated and the 2×1 reconstructed monohydride is also hardly to identify. When the temperature rises to as high as 730 K, the surface is domi-nated by the 2×1 structure with missing dimer rows, and some adatom chains occur on the Si substrate ler-races. We attribute the formation of these atomic chains to an epitaxial growth of Si atoms which are formed by the dissociation of SiH_x (x= 1, 2, 3 or 4) compounds on the Si surface.     

Features of atomic processes at the formation of a wetting layer and nucleation of three-dimensional Ge islands on Si(111) and Si(100) surfaces

The intermediate stages of the formation of a Ge wetting layer on Si(111) and Si(100) surfaces under quasiequilibrium grow conditions have been studied by means of scanning tunneling microscopy. The redistribution of Ge atoms and relaxation of mismatch stresses through the formation of surface structures of decreased density and faces different from the substrate orientation have been revealed. The sites of the nucleation of new three-dimensional Ge islands after the formation of the wetting layer have been analyzed. Both fundamental differences and common tendencies of atomic processes at the formation of wetting layers on Si(111) and Si(100) surfaces have been demonstrated. The density of three-dimensional nuclei on the Si(111) surface is determined by changed conditions for the surface diffusion of Ge adatoms after change in the surface structure. Transition to three-dimensional growth on the Si(100) surface is determined by the nucleation of single {105} faces on the rough Ge(100) surface.     

Si_3N_4/Si表面Si生长过程的扫描隧道显微镜研究

利用原位扫描隧道显微镜和低能电子衍射分析了Si的纳米颗粒在Si3N4 /Si(111)和Si3N4 /Si(10 0 )表面生长过程的结构演变 .在生长早期T为 35 0— 10 75K范围内 ,Si在两种衬底表面上都形成高密度的三维纳米团簇 ,这些团簇的大小均在几个纳米范围内 ,并且在高温退火时保持相当稳定的形状而不相互融合 .当生长继续时 ,Si的晶体小面开始显现 .在晶态的Si3N4 (0 0 0 1) /Si(111)表面 ,Si的 (111)小面生长比其他方向优先 ,生长方向与衬底Si(111)方向一致 .最后在大范围内形成以 (111)为主的晶面 .相反 ,在非晶的Si3N4 表面 ,即Si3N4 /Si(10 0 ) ,Si晶体的生长呈现完全随机的方向性 ,低指数面如 (111)和 (10 0 )面共存 ,但它们并不占据主导地位 ,大部分暴露的小面是高指数面如 (113)面 .对表面生长过程进行了探讨并给出了合理的物理解释     

Effect of hydrogenation on B/Si(0 0 1)-(1 × 2)

Ab initio calculations, based on pseudopotentials and density functional theory, have been performed to investigate the effect of hydrogenation on the atomic geometries and the energetics of substitutional boron on the generic Si(0 0 1)-(1 × 2) surface. For a single B atom substitution corresponding to 0.5 ML coverage, we have considered two different sites: (i) the mixed Si-B dimer structure and (ii) boron substituting for the second-layer Si to form Si-B back-bond structure, which is energetically more favorable than the mixed Si-B dimer by 0.1 eV/dimer. However, when both of these cases are passivated by hydrogen atoms, the situation is reversed and the Si-B back-bond case becomes 0.1 eV/dimer higher in energy than the mixed Si-B dimer case. For the B incorporation corresponding to 1 ML coverage, among the substitutional cases, 100% interdiffusion into the third layer of Si and 50% interdiffusion into the second layer of Si are energetically similar and more favorable than the other cases that are considered. However, when the surface is passivated with hydrogen, the B atoms energetically prefer to stay at the third layer of the Si substrate.