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1.
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 相似文献
2.
利用超高真空化学气相沉积系统, 基于低温Ge缓冲层和选区外延技术, 在Si/SiO2图形衬底上选择性外延生长Ge薄膜. 采用X射线衍射、扫描电镜、原子力显微镜、拉曼散射光谱等表征了其晶体质量和应变等参数随图形尺寸的变化规律. 测试结果显示, 位错密度随着图形衬底外延窗口的尺寸减小而减少, Ge层中的张应变随窗口尺寸的增大先增大而后趋于稳定. 其原因是选区外延Ge在图形边界形成了(113)面, 减小了材料系统的应变能, 而单位体积应变能随窗口尺寸的增加而减少; 选区外延厚度为380 nm的Ge薄膜X射线衍射曲线半高宽为678", 表面粗糙度为0.2 nm, 表明选区生长的Ge材料具有良好的晶体质量, 有望应用于Si基光电集成. 相似文献
3.
报道Ge在Ru(0001)表面上生长以及相互作用行为的扫描隧道显微镜(STM)和x射线光电子能谱(XPS)研究. STM的实验结果表明Ge在Ru(0001)表面的生长呈典型的Stranski_Krastanov生长模式,Ge的覆盖度小于单原子层时呈层状生长,而从第二层开始呈岛状生长. XPS测量显示衬底Ru(0001)与Ge的相互作用很弱. Ru(0001)表面的Ru 3d5/2和Ru 3d3/2芯态结合能分别处于2798和2840 eV. 随着Ge的生长,到Ge层的厚度为20个单原子层,衬底Ru 3d芯态结合能减小了约02 eV,而Ge 3d芯态结合能从Ge低覆盖度时的289 eV增加到了290 eV,其相对位移约为01 eV.
关键词:
Ge
Ru表面
生长
相互作用 相似文献
4.
采用晶体相场模型研究了异质外延过程中失配应变与应力弛豫对外延层界面形态演化的影响, 并对由衬底倾角引起的外延层晶向倾侧进行了分析.研究结果表明: 在有一定倾角的衬底晶体上进行外延生长时,若衬底和外延层之间失配度较大 (ε>0.08),外延层中弹性畸变能会以失配位错的形式释放, 最终薄膜以稳定的流动台阶形式生长且外延层的晶向倾角与衬底倾角呈近似线性关系. 而当衬底和外延层之间失配度较小(ε<0.04)不足以形成失配位错时, 外延层中弹性畸变能会以表面能的形式释放,最终使薄膜以岛状形态生长. 在高过冷度条件下,衬底倾角和失配度较大时,衬底和外延层之间会形成由大量位错规则排列而成的小角度晶界从而显著改变外延层的生长位向. 相似文献
5.
6.
用X射线反射方法研究了分子束外延技术生长的Si中Ge薄层异质结构的Ge原子分布特性.根据X射线反射理论及Parratt数值计算方法对实验反射曲线的模拟,得到不同厚度的Ge薄层异质结构样品中Ge原子的深度分布为非对称指数形式:在靠近样品表面一侧的衰减长度为8埃,而在靠近样品衬底一侧的衰减长度为3埃,且分布形式与Ge原子层的厚度无关.讨论了不同结构参数(Ge原子薄层的深度、Ge原子分布范围、样品表面粗糙度、样品表面氧化层厚度等)对样品低角反射曲线的影响. 相似文献
7.
用X射线反射方法研究了分子束外延技术生长的Si中Ge薄层异质结构的Ge原子分布特性.根据X射线反射理论及Parratt数值计算方法对实验反射曲线的模拟,得到不同厚度的Ge薄层异质结构样品中Ge原子的深度分布为非对称指数形式:在靠近样品表面一侧的衰减长度为8埃,而在靠近样品衬底一侧的衰减长度为3埃,且分布形式与Ge原子层的厚度无关。讨论了不同结构参数(Ge原子薄层的深度、Ce原子分布范围、样品表面粗糙度、样品表面氧化层厚度等)对样品低角反射曲线的影响. 相似文献
8.
利用超高真空化学气相淀积系统, 基于低温缓冲层和插入应变超晶格的方法, 在Si(100)衬底上外延出厚度约为880 nm的纯Ge层. 采用X射线双晶衍射、高分辨透射电镜、原子力显微镜和光致发光谱分别表征了其结构及光学性质. 测试结果显示外延Ge的X射线双晶衍射曲线半高宽为273", 表面均方根粗糙度为0.24 nm, 位错密度约为1.5×106 cm2. 在室温下观测到外延Ge的直接带跃迁光致发光, 发光峰值位于1540 nm. 表明生长的Si基Ge材料具有良好的结晶质量, 可望在Si基光电子器件中得到应用. 相似文献
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10.
GaAs/Ge的MOCVD生长研究 总被引:3,自引:3,他引:0
用常压MOCVD在Ge衬底上外延生长了GaAs单晶层,研究了GaAs和6e的极性与非极性材料异质外延生长,获得了质量优良的GaAs/Ge外延片,GaAs外延层X射线双晶衍射回摆曲线半高宽达16弧秒.10K下PL谱半峰宽为7meV.讨论了极性与非极性外延的界面反相畴问题和GaAs-Ge界面的Ga、Ge原子互扩散问题. 相似文献
11.
The Si capping of Ge/Si(001) islands was observed by in situ time-resolved transmission electron microscopy. During the initial stages of the Si deposition, islands were observed not only to flatten but also to shrink in volume. This unexpected shrinkage is explained by taking into account the intermixing of the deposited Si with the wetting layer and a consequently induced diffusion of Ge from the islands into the wetting layer. A model of the capping process which takes into account Ge diffusion is presented which is in good agreement with the experimental data. 相似文献
12.
T.I. Kamins K. Nauka R.S. Williams 《Applied Physics A: Materials Science & Processing》2001,73(1):1-9
Incorporating self-assembled Ge islands on Si surfaces into electronic devices has been suggested as a means of forming small
features without fine-scale litho-
graphy. For use in electronic devices, the electrical properties of the deposited Ge and their relation to the underlying
Si substrate must be known. This report presents the results of a surface photovoltage investigation of the surface energy
barrier as increasing amounts of Ge are added to a Si surface by chemical vapor deposition. The results are interpreted in
terms of band discontinuities and surface states. The surface barrier increases as a wetting layer is deposited and continues
to increase as defect-free islands form. It saturates as the islands grow. As the amount of Ge continues increasing, defects
form, and the surface barrier decreases because of the resulting allowed states at the Ge/Si interface. Qualitatively similar
behavior is found for Si(001) and Si(111). Covering the Ge with Si reduces the surface-state density and possibly modifies
the wetting layer, decreasing the barrier to one more characteristic of Si. Initial hydrogen termination of the surface decreases
the active surface-state density. As the H desorbs, the surface barrier increases until it stabilizes as the surface oxidizes.
The behavior is briefly correlated with scanning-tunneling spectroscopy data.
Received: 13 November 2000 / Accepted: 14 November 2000 / Published online: 23 May 2001 相似文献
13.
Rudd RE Briggs GA Sutton AP Medeiros-Ribeiro G Williams RS 《Physical review letters》2003,90(14):146101
We present a nanostructure diagram for use in designing heteroepitaxial systems of quantum dots. The nanostructure diagram is computed using a new equilibrium statistical physics model and predicts the island size and shape distributions for a range of combinations of growth temperature and amount of deposited material. The model is applied to Ge on Si(001), the archetype for bimodal island growth, and the results compare well with data from atomic force microscopy of Ge/Si islands grown by chemical vapor deposition. 相似文献
14.
G. Jin J.L. Liu S.G. Thomas Y.H. Luo K.L. Wang B.-Y. Nguyen 《Applied Physics A: Materials Science & Processing》2000,70(5):551-554
Self-organized Ge islands grown on patterned Si(001) substrates have been investigated. Selective epitaxial growth (SEG) of
Si is carried out with gas-source molecular beam epitaxy to form Si stripe mesas followed by subsequent Ge island growth.
Self-aligned Ge islands with regular spacing are formed on the <110>-oriented ridges of the Si mesas. The regular spacing
is driven by the repulsive interaction between the neighbor islands through the substrates. A mono-modal distribution of the
islands has been observed on the ridges of the Si mesas. The spatial confinement as well as the preferential nucleation is
believed to be the mechanism of this alignment of the self-organized Ge islands.
Received: 16 July 1999 / Accepted: 6 August 1999 / Published online: 24 March 2000 相似文献
15.
N. Hrauda J. J. Zhang M. Stoffel J. Stangl G. Bauer A. Rehman-Khan V. Holy O. G. Schmidt V. Jovanovic L. K. Nanver 《The European physical journal. Special topics》2009,167(1):41-46
We report on studies of strain and composition of two-dimensionally ordered SiGe islands grown by molecular beam epitaxy using
high resolution x-ray diffraction. To ensure a small size distribution of the islands, pit-patterned (001) Si wafers were used as substrates. The Si wafers were patterned by optical lithography and reactive ion etching. The
pits for island growth are ordered in regular 2D arrays with periods ranging from 500 to 1000 nm along two orthogonal 〈110〉
directions. After the growth of a Si buffer layer, 5 to 9 monolayers of Ge are deposited, leading to the formation of islands
with either dome- or barn shape, depending on the number of monolayers deposited. The Si capping of the islands is performed
at low temperatures (300○C) to avoid intermixing and thus strain relaxation. Information on the surface morphology obtained by atomic force microscopy
(AFM) was used to set up models for three-dimensional Finite Element Method (FEM) simulations of the islands including the
patterned Si substrate. In the model, special attention was given to the non uniform distribution of the Ge content within
the islands. The FEM results served as an input for calculating the diffracted x-ray intensities using kinematical scattering
theory. Reciprocal space maps around the vicinity of symmetric (004) and asymmetric (113) and (224) Bragg peaks were recorded
in coplanar geometry. Simulating different germanium gradients leads to altered scattered intensity distribution and consequently
information on this quantity is obtained for both dome- and barn-shaped islands as well as on the strain fields. 相似文献
16.
We report scanning tunneling microscopy observations of Ge deposited on the Si(111)-(7 x 7) surface for a sequence of submonolayer coverages. We demonstrate that Ge atoms replace so-called Si adatoms. Initially, the replacements are random, but distinct patterns emerge and evolve with increasing coverage, until small islands begin to form. Corner adatom sites in the faulted half unit cells are preferred. First-principles density functional calculations find that adatom substitution competes energetically with a high-coordination bridge site, but atoms occupying the latter sites are highly mobile. Thus, the observed structures are indeed more thermodynamically stable. 相似文献
17.
Jie Yang Yingxia Jin Chong WangLiang Li Dongping TaoYu Yang 《Applied Surface Science》2012,258(8):3637-3642
The effect of temperature and Ge coverage on the evolution of self-assembled Ge/Si islands grown by ion beam sputtering deposition is studied. Atomic force microscopy and Raman spectroscopy are used to analyze the island morphology and the intermixing between Si and Ge. The experiments are presented in two aspects. First, when the temperature is increased, intermixing is promoted, resulting in the reappearance of low aspect ratio islands. Second, a different evolution pathway is observed, in which short islands initially don’t grow along the constant ratio of 11:1 (diameter:height) and the islands always grow faster in vertical direction. In summary, the interdiffusion, surface diffusion, and amount of Ge determines the evolution of Ge/Si islands. 相似文献
18.
L. Vescan M. Goryll T. Stoica P. Gartner K. Grimm O. Chretien E. Mateeva C. Dieker B. Holländer 《Applied Physics A: Materials Science & Processing》2000,71(4):423-432
The distribution of Ge islands is analysed in order to understand their optical behaviour. The Ge islands described in this
paper were deposited by low-pressure chemical vapour deposition at relatively high temperature (700 °C), therefore the diffusion
length of adatoms is high (∼100 μm) and thus, not the limiting factor for nucleation. By changing the deposition time and
the coverage, square-based pyramids, domes and relaxed domes are nucleated. Mainly domes emit light, the emission being in
the wavelength range 1.38–1.55 μm. When pyramids or relaxed domes are present, the photoluminescence broadens and decreases
in intensity. The electroluminescence of vertically correlated islands increases with the number of layers, i.e. with the
number of islands. The nucleation of islands on patterned (001) Si is changed when the deposition is performed on Si mesas
with high index facets. The size distribution becomes narrower when the mesa size is decreased. An intermixing of up to 40%
Si in the 2D layer was determined from photoluminescence data. PIN diodes fabricated on patterned wafers show an area-dependent
electroluminecence related to a different microstructure of islands on large and small mesas. Finally, the lateral ordering
on {hkl} facets is discussed.
Received: 14 April 2000 / Accepted: 17 April 2000 / Published online: 6 September 2000 相似文献
19.
Based on first-principles calculations of surface diffusion barriers, we show that on a compressive Ge(001) surface the diffusivity of Ge is 10(2)-10(3) times higher than that of Si in the temperature range of 300 to 900 K, while on a tensile surface, the two diffusivities are comparable. Consequently, the growth of a compressive SiGe film is rather different from that of a tensile film. The diffusion disparity between Si and Ge is also greatly enhanced on the strained Ge islands compared to that on the Ge wetting layer on Si(001), explaining the experimental observation of Si enrichment in the wetting layer relative to that in the islands. 相似文献
20.
We have deposited a 12 nm thick Ge layer on Si(1 0 0) held at 200 °C by thermal evaporation under high vacuum conditions. Upon subsequent thermal annealing in vacuum, self-assembled growth of nanostructural Ge islands on the Ge layer occurred. Atomic force microscopy (AFM) and grazing incidence small-angle X-ray scattering (GISAXS) were used to characterize such layers. GISAXS measurements evidenced the formation of cylinder shaped structures upon annealing at 700 °C, which was confirmed by AFM measurements with a very sharp tip. A Ge mass transport from the layer to the islands was inferred by X-ray reflectivity and an activation energy of 0.40 ± 0.10 eV for such a process was calculated. 相似文献