Simulation of Nano Si and Al Wires Growth on Si(1O0) Surface

Growth of nano Si and Al wires on the Si(100) surfaces is investigated by computer simulation, including the anisotropic diffusion and the anisotropic sticking. The diffusion rates along and across the substrate dimer rows are different, so are the sticking probabilities of an adatom, at the end sites of existing islands or the side sites. Both one-dimensional wires of Si and Al are perpendicular to the dimer rows of the substrate, though the diffusion of Si adatoms is contrary to that of Al adatoms, i.e. Si adatoms diffuse faster along the dimer rows while Al adatoms faster across the dimer rows. The simulation results also show that the shape anisotropy of islands is due to the sticking anisotropy rather than the diffusion anisotropy,which is in agreement with the experiments.     

Simulation of Nano Si and Al Wires Growth on Si(100) Surface\+*

Because of the importance in microelectronics and their unique properties,the nanosilicon wires or other nano metal wires grown on Si(1 0 0 ) surface have been extensively in-vestigated and itis now a field ofvery active research[1—...     

Si(100)—As表面钝化作用和氧吸附

利用自己研制的具有分子束外延系统的表面分析联合谱仪研究了氧与Si(100)—As表面的相互作用。本文进一步证实了As层是Si表面的很好的钝化层,并首次研究了Si(100)—As表面的氧吸附全过程。实验表明,氧的饱和覆盖量为0.5单原子层,即Si表面上存在As原子层而使吸附位置减少一半。另外,通过吸附动力学分析得知,Si(100)—As表面的初始粘附系数是5.6×10~(-3),比清洁的Si(100)表面小一个数量级。Si表面上As的钝化作用是Si原子的悬挂键态被As原子的占有孤立对态代替而形成。     

无掩模Si圆柱纳米图形衬底上GaAs的异变外延生长

采用金属有机化学气相沉积方法在无掩模的直径为400nm的圆柱Si(100)图形衬底上外延生长了GaAs薄膜。图形衬底采用纳米压印技术及反应离子刻蚀技术制作而成。运用两步法生长工艺在此图形衬底上制备了厚度为1.8μm的GaAs外延层。GaAs的晶体质量通过腐蚀坑密度和透射电镜表征。图形衬底上的GaAs外延层表面腐蚀坑密度约1×107 cm-2,比平面衬底上降低了两个数量级。透射电镜观测显示大部分产生于GaAs/Si异质界面的穿透位错被阻挡在圆柱顶部附近。     

Fabrication of Co2Fe(Al,Si) and Co2Fe(Al,Si)/MgO on Ge(111) Substrate and Its Magnetic Properties

We investigated the interfacial effects on magnetic properties in Co₂Fe(Al,Si)/Ge (CFAS/Ge) and CFAS/MgO/Ge systems to demonstrate the effects of the interface structure on magnetic properties. CFAS and CFAS/MgO were deposited on the i-Ge(111) substrate. In-situ reflection high energy electron diffraction (RHEED) patterns showed epitaxially grown CFAS and MgO on Ge(111). According to the X-ray diffraction (XRD) ϕ-scan of CFAS(220), we determined that the crystallographic orientation relationships were CFAS(111)<–110>// Ge(111)<–110> and CFAS(111)<–110>//MgO(111)<–110>Ge(111)<–110>. The magnetic properties were measured by the vibrating sample magnetometer (VSM) and the saturation magnetization M_s value of CFAS with 2-nm thick MgO reached the value of L2₁ ordered one. A uniaxial magnetic anisotropy behavior was observed both in CFAS/Ge and CFAS/MgO/Ge structures after annealing. We confirmed the behavior did not only originate from the CFAS/Ge interface but also CFAS/MgO and the ordering structure.     

Growth and fabrication of AlGaN/GaN HEMT based on Si(1 1 1) substrates by MOCVD

AlGaN/GaN high electron mobility transistor (HEMT) hetero-structures were grown on the 2-in Si (1 1 1) substrate using metal-organic chemical vapor deposition (MOCVD). Low-temperature (LT) AlN layers were inserted to relieve the tension stress during the growth of GaN epilayers. The grown AlGaN/GaN HEMT samples exhibited a maximum crack-free area of 8 mm×5 mm, XRD GaN (0 0 0 2) full-width at half-maximum (FWHM) of 661 arcsec and surface roughness of 0.377 nm. The device with a gate length of 1.4 μm and a gate width of 60 μm demonstrated maximum drain current density of 304 mA/mm, transconductance of 124 mS/mm and reverse gate leakage current of 0.76 μA/mm at the gate voltage of −10 V.     

Al/SiO_2/Si表面Al_2O_3纳米图形的AFM阳极氧化制备方法

采用AFM阳极氧化方法,在控制AFM探针尖端电压和扫描方式的条件下,在Al/SiO2/Si表面制备了Al2O3纳米图形,图形最小尺寸为70nm.研究了表面吸附水层存在下AFM阳极氧化机理.实验结果表明AFM阳极氧化是制备金属氧化物半导体纳米器件的较好方法     

Effects of temperature and pressure in oxynitridation kinetics on Si(100) with N2O gas

We have investigated oxynitridation of Si(100) surfaces with nitrous oxide (N₂O) gas in a wide range of substrate temperatures (600–1000 °C) and N₂O pressures (10⁻²–10² Pa). The growth rate and atomic composition of the oxynitride layer have been measured by in situ x-ray photoelectron spectroscopy. The surface morphology of the oxynitride layer has been also observed by scanning electron microscopy. The results show that in higher N₂O pressure (>1 Pa) regime, the nitridation reaction is suppressed by the oxide layer, which quickly forms on the surface. On the other hand, in lower pressure (<1 Pa) and higher substrate temperature (>900 °C) regime, the nitridation reaction strongly occurs because of the active oxidation (etching reaction), which causes the surface roughness. It is found by argon-ion-sputtering measurements that the nitride layer locally exists only near the surface at the reduced N₂O pressure. We discuss qualitatively the oxynitridation kinetics and the effective condition for growing the oxynitride layer.     

ScAlN缓冲层厚度对Si(100)衬底上GaN外延层的影响

采用脉冲直流磁控溅射方法在Si(100)衬底上制备了ScAlN薄膜。以溅射的ScAlN作为缓冲层,在Si(100)衬底上用金属有机化学气相沉积(MOCVD)技术外延了GaN薄膜。使用高分辨X射线衍射、原子力显微镜和拉曼光谱研究了ScAlN缓冲层的厚度对ScAlN缓冲层和GaN外延层的影响。研究结果表明,ScAlN缓冲层的厚度是影响GaN薄膜晶体质量的重要因素。随着ScAlN厚度的增加,ScAlN的(002)面X射线衍射摇摆曲线半高宽持续减小,GaN的(002)面X射线衍射摇摆曲线半高宽先减小后增大。当ScAlN缓冲层厚度为500nm时,得到的GaN晶体质量最好,其中GaN(002)面的X射线衍射摇摆曲线半高宽为0.38°,由拉曼光谱计算得到的张应力为398.38MPa。     

Growth and characterization of ZnO nanowires grown on the Si(1 1 1) and Si(1 0 0) substrates: Optical properties and biaxial stress of nanowires

In this paper the effects of silicon substrates with different orientations on the morphological and optical properties as well as biaxial stress of ZnO nanowires were investigated. The ZnO nanowires were grown on Si(1 0 0) and Si(1 1 1) substrates by the vapor–solid (VS) method using a physical vapor deposition reactor. In addition ZnO nanowires were grown on Si(1 1 1) substrate by the vapor–liquid–solid (VLS) method using an Au film as catalyst, which were deposited on Si(1 1 1) substrate using a sputtering method, with the same conditions. Room temperature photoluminescence (PL) spectrum showed a stronger ultraviolet (UV) peak at 381 nm for the nanowires that were grown on Si(1 1 1) by the VS method than those that were grown on Si(1 0 0) with the same green emission (deep-level emission (DLE)) intensities at about 520 nm peak. On the other hand, the PL result of the ZnO nanowires, which were grown by the VLS method, showed the same intensities for the both UV and DLE peaks. Furthermore, the effects of silicon substrate orientation and Au catalyst on biaxial stress of the nanowires were studied by Raman spectrometer. It was discussed that Au catalyst was one of the important factors that could affect the biaxial stress value of the ZnO nanowires that were grown on Si substrates.     

The Growth of Transition Metals on H‐Passivated Si(111) Substrates

The growth of Co and Ag layers on wet‐processed H‐passivated Si(111) substrates by molecular beam epitaxy (MBE) has been studied using high resolution scanning tunneling microscopy (STM) with regard to possible applications of the layers in magnetoelectronic devices. Roughness and intermixing at interfaces as functions of deposition temperature and layer thickness are key parameters for the performance of such devices. The initial growth of Co and Ag and the influence of Ag atoms on the Si(111) surface reconstructions provide insight into adatom–substrate interactions.     

硅表面上的纳米量子点的自组织生长

纳米半导体量子点以其所具有的新颖光电性质与输运特性正在受到人们普遍重视。作为制备高质量纳米量子点的工艺技术 ,自组织生长方法倍受材料物理学家的青睐。而如何制备尺寸大小与密度分布可控的纳米量子点更为人们所注目。因为这是关系到纳米量子点最终能否器件实用化的关键。文中以此为主线 ,着重介绍了各种 Si表面 ,如常规表面、氧化表面、台阶表面以及吸附表面上 ,不同纳米量子点的自组织生长及其形成机理 ,并展望了其未来发展前景     

Si(111)湿法腐蚀后表面形态的FTIR研究

运用偏振衰减全反射傅立叶变换红外光谱技术 (ATR-FTIR) ,研究了 Si(1 1 1 )在不同比例的 NH4F-HCl溶液中腐蚀后的表面形态。通过分析表面振动模型的偏振波长及红外粗糙因子 ,表明在较低的 PH值的NH4F-HCl溶液中腐蚀的 Si(1 1 1 )表面粗糙度较大 ,与通过扫描隧道显微镜 (STM)技术测量的结果基本一致     

Si(113)表面电子结构的研究

采用Si_(16)H_(21)和Si_(31)H_(39)原子集团分别模拟Si(113)和Si(111)表面;通过半经验自洽CNDO法计算了两个体系的电子结构.结果表明,Si(113)具有与Si(111)不同的表面态特征.Si(113)表面台阶和台面原子上电荷重新分布,与悬键相关的表面电子态都强烈地定域在表面Si原子上,尤其局域在悬键方向上,并且具有比(111)面上更高的悬健态密度.理论计算结果能解释以前的光电子谱实验.     

铝插入层对硅基AlN外延特性的影响

采用等离子体辅助分子束外延(PA-MBE)研究了Al金属插入层对Si(111)衬底上AlN薄膜材料生长的影响。结果证明,Al插入层可改善AlN外延层的晶体质量,而且引入Al预扩散机制可消除外延表面的孔隙。同时,采用AlN插入层预扩散有利于获得Al极性的AlN,否则倾向于获得N极性的AlN。     

Amplifying Surface Energy Difference toward Anisotropic Growth of All-Inorganic Perovskite Single-Crystal Wires for Highly Sensitive Photodetector

It is a great challenge to directly grow super long all-inorganic perovskite monocrystalline wires due to the weak surface energy difference among the low index facets. Here, a one-pot solution process to grow the aspect ratio over 10⁵ of monocrystalline CsPbBr₃ perovskite wires (PWs) and yield up to 70% is reported. A chemical potential dependent surface energy difference amplification strategy is proposed to regulate the surface energy of growing and grown surfaces accordingly to the anisotropic growth of CsPbBr₃. The anisotropic growth of wires is derived from the regulation of anti-solvent diffusion kinetic and the mass transfer kinetic control of the metal halide salts. This experiment demonstrates a 50 times amplification of surface energy difference. As-produced PWs present a high photodetection responsivity up to 4923 A W⁻¹, external quantum efficiency exceeding 13 784%, and detectivity over 3.6 × 10¹³ Jones. This work not only reveals the mechanism of surface energy dominated anisotropic growth for CsPbBr₃ PWs, but also elucidates the important role of kinetics regulation during the growth process, which may open a new window for the low-dimensional crystal growth of ionic compounds.     

Selective Growth of CdTe on Si(211): First-Principle Calculations

The adsorption of CdTe layers on clean and As-passivated Si(211) substrates has been simulated by first-principle calculations in this study. Based on the simulation results, we theoretically show the important roles of the As₄ passivation during the epitaxial growth. Arsenic can saturate part of the dangling bonds and weaken the surface states. The partial passivation finally induces the B-face polarity selection automatically. This conclusion can provide further explanations for the successful growth of large area high-quality CdTe(211)B layers on the Si(211) substrates.     

Nucleation of ZnTe on the As-Terminated Si(112) Surface

We employ a suite of surface analysis techniques that probe the outermost ZnTe/As-Si(112) surface to generate an understanding of the initial stages of the heteroepitaxial HgCdTe/CdTe/ZnTe/As-Si(112) layer formation. Ion scattering spectroscopy (ISS), reflection-high energy electron diffraction (RHEED), along with nondestructive depth profiles by angle-resolved x-ray photoelectron spectroscopy (XPS) are successfully applied to clarify and support the nucleation stages of ZnTe formation on the As-terminated Si(112) substrate. Data indicate a slow growth of the first ZnTe layer. In addition, no evidence of thick ZnTe island formation exists. The current ZnTe formation process generates full coverage on the Si(112) surface after six to nine MBE cycles. In order to fully understand the details of the ZnTe nucleation process on the Si(112) substrate, we present an inelastic background analysis with the Tougaard method to study surface morphology.     

Si(113)表面的原子结构

利用LEED研究了Si(113)表面的原子结构.清洁表面是采用离子轰击和退火方法制备的.实验发现:当温度高于600℃时表面为1×1结构,随着温度缓慢下降,表面原子结构发生1×1(?)3×1(?)3×2的可逆相变.