Organometallic chemical vapor deposition using allyl precursors

Homoleptic allyl derivatives of many Main-Group and transition metals, M(C₃H₅)_n, are readily available through one-pot syntheses using metal halides and allyl Grignard reagents or by alkylation of alkali-metal salts. The relatively low molecular weight of a C₃H₅ ligand contributes to high vapor pressures whilst the stability of the allyl radical is predicted to reduce decomposition temperatures. These compounds represent a class of volatile precursors for organometallic chemical vapor deposition (OMCVD) of thin films. Film growth studies using iridium, molybdenum, palladium, platinum, rhodium, selenium, tellurium and tungsten compounds are reviewed and the relationships between pyrolysis pathways and film purity are discussed.     

Static ToF-SIMS analysis of plasma chemically deposited ethylene/allyl alcohol co-polymer films

A plasma co-polymerization of ethylene as a “chain extending” monomer and allyl alcohol as a carrier monomer for hydroxyl groups was studied. The composition of the feed gas was systematically varied and the plasma co-polymers were analyzed in terms of their relative concentrations of OH functional groups by static Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) immediately after their preparation without any air contact, i.e., under so called “in situ” conditions.The relative OH group concentration involved in the -CH₂-OH groups was derived from the normalized yields of the CH₃O⁺ secondary fragment ion. The density of functional groups in the plasma co-polymers was found to vary non-linearly with respect to the mole percentage of the monomers in the feed gas.Co-polymerization phenomena, i.e. chemical interactions and recombination reactions taking place between monomer molecules in the plasma and/or during the deposition process, become evident in ToF-SIMS spectra.     

Site-controlled quantum dots grown in inverted pyramids for photonic crystal applications

We report on the growth and optical properties of various configurations of sub-micron pitch dense arrays of pyramidal quantum dots (QDs) grown by organometallic chemical vapour deposition on patterned substrates. We show that the effective growth rate of these QDs is influenced by the ratio between the free {1 1 1}B area and {1 1 1}A exposed facets surrounding them. This provides a powerful technique for engineering the energy level structure of ordered QD arrays by means of geometrical patterning of the growth template. Such technique should be particularly useful for applications in photonic crystals incorporating QDs with tailored absorption and/or emission properties.     

Applications of “Dry” Processing in the Microelectronics Industry Using Carbon Dioxide

Condensed carbon dioxide (CO₂) has emerged as a leading enabler of advanced semiconductor manufacturing processes. By exploiting the physical properties of CO₂, some of the current challenges encountered in microelectronics processing related to shrinking feature sizes and materials compatibility have been addressed. Furthermore, the potential for reduction of chemicals used in processing is realized. Applications of CO₂ in microelectronics operations such as wafer cleaning, spin-coating, development, and stripping of photoresists, drying, low-k film preparation and repair, etching, and metal deposition are discussed.     

类富勒烯纳米晶CNx薄膜及其场致电子发射特性

利用微波等离子体增强化学气相沉积技术制备出了CN_x薄膜,并利用x射线光电子能谱、x射线衍射、扫描电子显微镜和Raman光谱等测试手段对所制备的CN_x薄膜的微结构和成分进行了分析.研究了其场致电子发射特性.发现薄膜的结构和场发射特性与反应系中的甲烷、氮气及氢气的流量比有关,当甲烷、氢气及氮气流量比为8/50/50 sccm时,制备的薄膜具有弯曲层状的纳米石墨晶体结构（类富勒烯结构）和很好的场发射特性.场发射阈值电场降低至1.1V/μm.当电场为5.9V/μm时,平 关键词： 类富勒烯 x薄膜')" href="#">CN_x薄膜 场致电子发射 微波等离子体增强化学气相沉积     

The parameter space for the direct spinning of fibres and films of carbon nanotubes

We have recently introduced a method for the continuous spinning of carbon nanotube fibres and films directly from the gas phase of a chemical vapour deposition furnace [Y. Li, et al., Science 304 (2004) 276]. In this work the effect of the process parameters on the ability to spin continuously is studied, with particular focus on the carrier gas and feedstock flow rates. Catalyst dilution by high carrier gas flow rates led to smaller diameter nanotubes but these conditions are found the hardest to spin.     

CVD金刚石薄膜的应力研究

 利用X射线衍射研究了化学气相沉积的金刚石薄膜的应力情况。研究表明：热应力在研究范围内为压应力，本征应力是张应力。分析了薄膜厚度、生长温度、碳源浓度等实验参数对薄膜应力的影响。     

Engineering the interface energetics of solar cells by grafting molecular properties onto semiconductors

The electronic properties of semiconductor surfaces can be controlled by binding tailor-made ligands to them. Here we demonstrate that deposition of a conducting phase on the treated surface enables control of the performance of the resulting device. We describe the characteristics of the free surface of single crystals and of polycrystalline thin films of semiconductors that serve as absorbers in thin film polycrystalline, heterojunction solar cells, and report first data for actual cell structures obtained by chemical bath deposition of CdS as the window semiconductor. The trend of the characteristics observed by systematically varying the ligands suggests changes in work function rather than in band bending at the free surface, and implies that changes in band line-up, which appear to cause changes in band bending, rather than direct, ligand-induced band bending changes, dominate.     

Growth, percolation, and correlations in disordered fiber networks

This paper studies growth, percolation, and correlations in disordered fiber networks. We start by introducing a 2D continuum deposition model with effective fiber-fiber interactions represented by a parameterp which controls the degree of clustering. Forp=1 the deposited network is uniformly random, while forp=0 only a single connected cluster can grow. Forp=0 we first derive the growth law for the average size of the cluster as well as a formula for its mass density profile. Forp>0 we carry out extensive simulations on fibers, and also needles and disks, to study the dependence of the percolation threshold onp. We also derive a mean-field theory for the threshold nearp=0 andp=1 and find good qualitative agreement with the simulations. The fiber networks produced by the model display nontrivial density correlations forp<1. We study these by deriving an approximate expression for the pair distribution function of the model that reduces to the exactly known case of a uniformly random network. We also show that the two-point mass density correlation function of the model has a nontrivial form, and discuss our results in view of recent experimental data on mss density correlations in paper sheets.     

螺旋波等离子体增强化学气相沉积氮化硅薄膜

利用螺旋波等离子体增强化学气相沉积(HWP-CVD)技术，以SiH4和N2为反应气体进行了氮化硅(SiN)薄膜沉积，并研究了实验参量对薄膜特性的影响.利用傅里叶变换红外光谱、紫外—可见光谱和椭偏光检测等技术对薄膜的结构、厚度和折射率等参量进行了测量.结果表明，采用HWP-CVD技术能在低衬底温度条件下以较高的沉积速率制备低H含量的SiN薄膜，所沉积的薄膜主要表现为Si—N键合结构.采用较低的反应气体压强将提高薄膜沉积速率，并使薄膜的致密性增加.适当提高N2/SiH4比例有利于薄膜中H含量的降低. 关键词： 螺旋波等离子体 化学气相沉积 氮化硅薄膜