大气下火焰法合成金刚石薄膜

本文介绍了用氧-乙炔火焰法在大气下合成金刚石薄膜的实验结果,初步研究了基板温度对金刚石晶体生长速度、结晶习性的影响,指出了在金刚石(111)及(100)晶面上外延单晶金刚石膜的温度范围,还探讨了氧对薄膜的质量均匀性的影响。     

化学汽相沉积金刚石薄膜的生长

利用热丝化学汽相沉积法生长出优异的金刚石薄膜，研究表明，金刚石的成核依赖于沉积点的尖锐度，薄膜的生长包括晶粒长大和薄膜上的二次成核及其生长，可用分层生长来描述，金刚石晶粒的生长由外延生长和二次成核及其生长组成。也是分层进行的，结果导致了金刚石晶体和薄膜的层状结构。     

偏压技术在金刚石薄膜制备中应用的进展

近年来,用偏压技术进行异质外延单晶金刚石生长并将其尺寸增大到英寸级以上。偏压技术强大的形核能力使其也可用于制备取向金刚石薄膜、纳米金刚石薄膜和超纳米金刚石薄膜。本文综述了国内外关于偏压技术的机理以及偏压的形式和设备等方面的研究现状,以及表面反应模型、热尖峰模型和亚层注入模型的机理。常用的偏压包括直流偏压、直流脉冲偏压、脉冲叠合偏压和双极性脉冲偏压。还介绍了偏压对金刚石薄膜组织和性能的影响,详细阐述了其对取向生长,二次形核率,无定形碳-石墨-金刚石相转变以及生长速率和结合力的作用规律和机理。加偏压能改变轰击粒子能量和特定基团的浓度、影响金刚石相的转变和晶粒取向和尺寸,进而影响金刚石薄膜的光,力,热,电学性能。还讨论了目前研究工作中存在的一些不足,如偏压作用的机理仍不清晰,对电子浓度变化,氢原子刻蚀的作用尚缺少明确的解释等。最后展望了偏压技术在金刚石制备领域未来的研究和应用方向。     

CVD金刚石薄膜取向生长研究现状

单晶衬底上外延生长金刚石薄膜一直是ＶＣＤ金刚石技术领域的重要研究方向之一,近年来这方面的研究取得了长足的进步。回顾了金刚石取向膜的研究史,介绍了提高金刚石膜取向度的方法和目前对金刚石取向膜生长过程,生长机理研究取得的进展及金刚石取向膜具有独特优异性能的实验研究。     

金刚石薄膜异质外延的研究状况与展望

综述了化学气相沉积异质外延金刚石薄膜机理及工艺的研究现状，分析了存在的问题，并对今后的研究进行了展望。     

沉积参数对化学气相沉积纳米金刚石薄膜的影响

用强电流直流伸展电弧化学气相沉积金刚石薄膜装置,在CH4-Ar和CH4-H2-Ar气氛中沉积了纳米金刚石薄膜,研究了沉积气氛中H2加入量和沉积压力对金刚石薄膜显微组织和生长机制的影响.沉积气氛中H2含量对金刚石薄膜的表面形貌、晶粒尺寸和生长速度有显著影响,随着H2含量增加,金刚石晶粒尺寸增大,薄膜生长速度提高.在1%CH4-Ar气氛中沉积的纳米金刚石薄膜,晶粒尺寸细小,薄膜表面形貌光滑平整.在1%CH4-少量H2-Ar气氛中沉积的金刚石薄膜,晶粒尺寸小于100nm,薄膜表面形貌较平整.随着沉积压力提高,金刚石薄膜的生长速度增大.用激光Ram an对金刚石薄膜进行了表征.     

器件级同质外延CVD金刚石膜上的具有高击穿电压的铝肖特基二极管

用微波等离子体化学气相沉积方法合成高品质同质外延金刚石膜,并且用扫描电镜和阴极荧光分析法评价。为了得到高薄膜生长速率,把甲烷浓度设定在4%。薄膜上的生长丘的数量和大小依赖于生长条件。在本工作的样品中,未发现任何非外延晶粒。室温下的阴极荧光分光结果表明这种金刚石薄膜具有与自由励起子相关的谱峰。氢终端的膜表面制作的铝电极显示了P型整流特性。击穿电压高于380V。实验结果表明,阴极荧光分析法观测到的缺陷和电性能密切相关,并且可以在有室温边发射的金刚石表面上制作具有高击穿电压的整流电极。     

金刚石薄膜场发射特性研究现状

金刚石薄膜具有负电子亲合能、高热导率和极强的化学惰性等优势，作为场发射材料引起了广泛关注。回顾了金刚石薄膜的分类，介绍了氢化金刚石薄膜具有的负电子亲合能特性，分析了金刚石薄膜场发射特性的影响因素，列举了场发射特性的优化方向，并总结了文献中报道的金刚石薄膜与其他材料复合获得的场发射阴极的性能，对于分析和改进金刚石薄膜器件场发射性能具有重要意义。     

金刚石薄膜摩擦学性能研究进展

化学气相沉积的金刚石薄膜通常是一种表面粗糙的多晶薄膜,其摩擦系数相对于单晶金刚石明显偏高,制约着其在摩擦学领域的应用.本文介绍了近年来国内外学者为提高金刚石薄膜摩擦学性能而进行的探索研究及其发展现状.简要分析了影响金刚石薄膜摩擦学性能的主要因素,并提出金刚石薄膜应用于摩擦学领域需要重视解决的几个问题.     

提高CVD金刚石薄膜附着力的方法及其研究进展

概述了金刚石薄膜与衬底附着力研究的最新进展,详细讨论了衬底材料的性质、衬底预处理方法、过渡层、负偏压以及CVD沉积条件对金刚石薄膜附着力的影响,总结出提高附着力的主要方法,并分析了金刚石薄膜的应用状况,指出了扩大金刚石薄膜应用的新方向及存在的主要问题.     

Numerical simulation of some peculiarities of the formation of multilayer structures with quantum dots by means of molecular beam epitaxy

Some peculiarities of the growth of nanoislands in multilayer heteroepitaxial stressed systems are studied numerically based on the theory of elastic interaction. Different scenarios of the behavior of the system of vertically coupled islands and the intervals, separating these scenarios, are determined for the case of heteroepitaxial growth of multilayer systems.     

Shedding Light on the Role of Misfit Strain in Controlling Core–Shell Nanocrystals

Heteroepitaxial modification of nanomaterials has become a powerful means to create novel functionalities for various applications. One of the most elementary factors in heteroepitaxial nanostructures is the misfit strain arising from mismatched lattices of the constituent parts. Misfit strain not only dictates epitaxy kinetics for diversifying nanocrystal morphologies but also provides rational control over materials properties. In recent years, advances in chemical synthesis along with the rapid development of electron microscopy and X-ray diffraction techniques have enabled a substantial understanding of strain-related processes, which offers theoretical foundation and experimental guidance for researchers to refine heteroepitaxial nanostructures and their properties. Herein, recent investigations on heterogeneous core–shell nanocrystals containing misfit strains are summarized, with a focus on the mechanistic understanding of strain and strain-induced effects such as tuning the epitaxial habit, modulating the optical emission, and enhancing the catalytic activity and magnetic coercivity.     

Microstructures of GaN thin films grown on graphene layers

Plan-view and cross-sectional transmission electron microscopy images show the microstructural properties of GaN thin films grown on graphene layers, including dislocation types and density, crystalline orientation and grain boundaries. The roles of ZnO nanowalls and GaN intermediate layers in the heteroepitaxial growth of GaN on graphene, revealed by cross-sectional transmission electron microscopy, are also discussed.     

Alloy formation at the tetrapod core/arm interface

The nature of the interfacial structure between the core and the arms of a tetrapod quantum dot (QD) formed during the heteroepitaxial growth of a ZnS arm onto a CdSe core is not well understood but can be analyzed through the use of high-frequency electron paramagnetic resonance (HF-EPR) spectroscopy. The spectroscopic resolution at high frequency allows the presence of unique crystal fields reflecting interfacial alloying to be analyzed by incorporating Mn(II) ions as a dopant into the QD to act as an intentional EPR active spectroscopic probe. In addition, the HF-EPR can spectroscopically observe the presence of ion vacancies that are anticipated to form at the heteroepitaxial interface to accommodate structural mismatch. The HF-EPR spectra for Mn(II) are extremely sensitive to perturbations of the microenvironment due to changes in the crystal field. The HF-EPR spectra of Mn(II) in a CdSe (core)/ZnS (arm) tetrapod exhibiting wurtzite symmetry for both core and interface of the tetrapod provide clear evidence of heteroalloying at the core-arm interface and formation of intrinsic dislocations at grain boundaries. The formation of the interfacial alloy and grain boundaries reflects short-range ion migration at the heteroepitaxial layer to reduce strain energy due to the 12% lattice mismatch between the wurtzite lattices of CdSe and ZnS.     

Microstructure, magnetic, and low-field magnetotransport properties of self-assembled (La0.7Sr0.3MnO3)0.5:(CeO2)0.5 vertically aligned nanocomposite thin films

Two-phase (La(0.7)Sr(0.3)MnO(3))(0.5):(CeO(2))(0.5) (LSMO:CeO(2)) heteroepitaxial nanocomposite films were grown on SrTiO(3) (STO) (001) by pulsed laser deposition (PLD). X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that LSMO:CeO(2) films epitaxially grow on STO as self-assembled vertically aligned nanocomposite (VAN). Magnetic and magnetotransport measurements demonstrate that the LSMO phase in the VAN structure behaves differently from its epitaxial single-phase counterpart, e.g. greatly enhanced coercivity (H(C)) and low-field magnetoresistance (LFMR). The enhanced properties in the VAN system are attributed to the interaction between the perovskite and the secondary phase or phase boundary. The results suggest that the growth of functional oxide in another oxide matrix with vertical heteroepitaxial form is a promising approach to achieve new functionality that may not be easily realized in the single epitaxial phase.     

Heteroepitaxial growth of the δ-Ta2O5 films on α-Al2O3 (0001)

Journal of Materials Science: Materials in Electronics - The heteroepitaxial δ-Ta2O5 films were deposited on α-Al2O3 (0001) by MOCVD. As the growth temperature increases from...     

X-ray irradiation at subthreshold energies modifies the surface micromorphology of epitaxial silicon layers on sapphire

Atomic force microscopy investigations revealed a change in the surface microrelief of the heteroepitaxial silicon films on sapphire substrates after pulsed X-ray irradiation at an energy of E≤140 keV.     

Absolute lattice parameter measurement

Absolute lattice parameter methods are useful for determining alloy composition, understanding point defects and dopants in semiconductor substrate materials and for the evaluation of lattice relaxation in heteroepitaxial layers. This paper reviews the techniques available. The assumptions and uncertainties of each technique are discussed.     

C－BN衬底上金刚石的异质外延生长研究

用热灯丝ＣＶＤ方法在Ｃ－ＢＮ单晶衬底上制备出金刚石膜，并且在Ｃ－ＢＮ（１００）面上观察到金刚石的异质外延。