Composite plasma-polymerized organosiloxane-based material for hydrocarbon vapor selectivity

Films synthesized by plasma enhanced chemical vapor deposition from a mixture of octamethyltrisiloxane and hexamethylcyclotrisiloxane have been studied regarding to their preparation, deposition, chemical composition and membrane properties according to hydrocarbon vapor selectivities of solubility.

Composition of the plasma glow discharge in neutral species has been studied by mass spectrometry whereas structural information of the deposited membranes has been extracted from Fourier transform infra-red (FTIR) spectroscopy. In the deposition conditions presented here leading to plasma-polymerized films, heavy radicals mostly contribute to their growth and their chemical composition. Depending on the precursors ratio in the plasma, i.e. linear and cyclic clusters ratio in the deposited material, solubility of selectivity against nitrogen of the deposited material varies from 50 up to 150 for hexane vapor.     

高阻隔碳氢膜的制备及性能研究

利用射频等离子体化学气象沉积法（r.f.PECVD），在12μm厚的聚对苯二甲酸乙二醇酯 (PET)上制备了碳氢膜. 用原子力显微镜（AFM），x射线光电子能谱（XPS），激光拉曼光谱，傅里叶红外光谱等仪器，对碳氢膜的表面形貌和内部结构特性进行了较详细研究. 镀碳氢膜PET的阻隔性能在标准透水蒸气测试仪上进行检测. 实验结果证明：沉积工艺参数对碳氢膜的生长速率及结构性能有重要影响；在PET上沉积的是纳米碳氢膜，该膜主要由sp2和sp3杂化的碳氢化合物组成；当PET上碳氢膜厚度为900nm时，阻水蒸气性能可提高7倍. 关键词： 碳氢膜 射频等离子体化学气象沉积法 聚对苯二甲酸乙二醇酯 阻隔性能     

PECVD growth of crystalline silicon from its tetrafluoride

The process of plasma chemical deposition of silicon from inductively coupled plasma of the mixture of high‐purity SiF₄ and H₂ sustained by RF discharge at 13.56 MHz in amount sufficient for subsequent growth of crystal by Czochralski method was investigated. The structure and impurity content of the produced layers as well as of the grown crystal have been studied (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

射频功率对PECVD制备类金刚石薄膜光学性能的影响

采用射频等离子体增强化学气相沉积(RF-PECVD)法在石英片上生长类金刚石薄膜。通过紫外可见分光光度计、椭偏仪测试手段,研究不同射频功率条件下类金刚石薄膜的光学性能的变化。结果表明,射频功率对类金刚石薄膜的生长具有重要影响,在较低功率下生长的类金刚石薄膜,具有较高的光学透过率和较大的光学带隙。     

Single-mode SiON/SiO2/Si optical waveguides prepared by plasma-enhanced chemical vapor deposition

We present the characteristics of low-propagation-loss single-mode SiON / SiO₂ / Si planar optical waveguides using plasma-enhanced chemical vapor deposition (PECVD). Using a thermal annealing process and a thick silicon dioxide buffer layer, we get an improvement on the propagation loss by the amounts of 1.24 dB /cm and 1.1 dB /cm, respectively. Optical waveguides with propagation loss lower than 0.3 dB /cm can be achieved.     

A spectroscopic investigation of growth regimes in silane-ammonia discharges used for plasma nitride deposition

Using optical emission spectroscopy (OES) we have been able to distinguish three operating regimes for the ammonia-silane glow discharge used in plasma nitride deposition. By monitoring the deposition rate and analyzing the structure and composition of thea-SiN: H films it has been possible to correlate these three plasma regimes with three distinct deposition mechanisms. The growth plasma may be tuned to each of these regimes by varying one or more of the following three external parameters: ammonia mole fraction, r .f. power, and gas flow rate. Choice of these parameters allows control of the NH _n radical concentration and the residence time in the reactor, and hence control over the number of gas-phase SiH _n -NH _n radical-radical reactions. Thus OES makes control of the film deposition mechanism possible.     

Structure,Composition, Mechanical,and Tribological Properties of BCN Films Deposited by Plasma Enhanced Chemical Vapor Deposition

In this work thin BCN films were deposited by plasma enhanced chemical vapor deposition (PECVD) using chloridic precursors. Through adjusting the BCl₃ content in the inlet gas mixture the chemical composition of the deposited films was changed from carbon rich to boron rich. Based on optical emission spectroscopy (OES) measurements, a correlation between film composition and precursor species concentration in the plasma was established. The films were amorphous as detected by grazing incidence X-ray diffraction (GIXRD). The hardness and the elastic modulus have maximal values of 25.5±1.2 and 191±6 GPa, respectively, for the films with a boron concentration of 45.2 at.%. GIXRD data suggest that a depletion in boron content may initiate the formation of graphitic domains in the amorphous matrix. The observed degradation of the mechanical properties is associated with the graphitization. The tribological behavior was studied with a tribometer operated in pin-on-plate configuration at the temperatures 25 and 400°C. The wear mechanisms were discussed with respect to the formation of a boric acid surface layer which was detected by reflection electron energy loss spectroscopy (REELS) analysis.     

Molecular Design of Fluorocarbon Film Architecture by Pulsed Plasma Enhanced and Pyrolytic Chemical Vapor Deposition

Pulsed plasma enhanced chemical vapor deposition (pulsed PECVD) and pyrolytic chemical vapor deposition (pyrolyric CVD) of fluorocarbon films from hexafluoropropylene oxide (HFPO) have demonstrated the ability to molecularly design film architecture. Film structures ranging from highly amorphous crosslinked matrices to linear perfluoroalkyl chain crystallites can be established by reducing the modulation frequency of plasma discharge in plasma activated deposition and by eventually shifting mechanistically from an electrically activated to a thermally activated process. X-ray photoelectron spectroscopy (XPS) showed CF₂ content increasing from 39–65 mol%. Fourier transform infrared spectroscopy (FTIR) showed an increasing resolution between the symmetric and asymmetric CF₂ stretches, and a reduction in the intensity of the amorphous PTFE and CF₃ bands. High-resolution solid-state ¹⁹F nuclear magnetic resonance spectroscopy (NMR) revealed an increasing CF₂CF₂CF₂ character, with the pyrolytic CVD film much like bulk poly(tetrafluoroethylene) (PTFE). X-ray diffraction (XRD) patterns evidenced an increase in crystallinity, with the pyrolytic CVD film showing a characteristic peak at 2 = 18° representing the (100) plane of the hexagonal structure of crystalline PTFE above 19°C.     

The Role of Oxygen Dissociation in Plasma Enhanced Chemical Vapor Deposition of Zinc Oxide from Oxygen and Diethyl Zinc

The influence of electron impact dissociation of oxygen on neutral chemistry was studied for plasma-enhanced chemical vapor deposition (PECVD) of zinc oxide using oxygen and diethyl zinc. Electron conditions in the reactor were estimated based on simulations of well-known Ar-O₂ plasmas, while the majority of the thermal chemistry was abstracted from the combustion literature. A rudimentary model of film growth was developed using the rate of oxygen dissociation as the lone adjustable parameter.n Model results were compared directly with experimental measurements of deposition rates and neutral species densities for a wide range of conditions. Good quantitative agreement between experiments and model were observed as a function of composition and rf power. The system is highly sensitive to the electron impact dissociation of oxygen, which creates the radical pool that drives the majority of the chemistry. The approach detailed here provides a framework for the development of models of oxide PECVD derived from other metalorganic precursors.     

Vertically aligned carbon nanotube based electrodes: Fabrication, characterisation and prospects

We present a methodology to fabricate carbon nanotube based electrodes using plasma enhanced chemical vapour deposition. The metal catalyst nanoparticles used to promote nanotube growth are removed using a water plasma treatment in combination with an acid attack. The final integrated microelectrode-based devices present excellent electrocatalytic properties that make them suitable for electrochemical applications. The presented methodology enables the construction of highly regular and dense vertically aligned carbon nanotube (VACNT) forests that can be confined within the patterned bounds of a desired surface. These VACNT electrodes display very low capacitive currents and are amenable to further chemical modifications.