Pulsed Electron Beam Deposition of Nanocrystalline Diamond
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Pulsed Electron Beam Deposition of Nanocrystalline Diamond Redhouane Henda and Omar Alshekhli School of Engineering, Laurentian University, Ramsey Lake Road, Sudbury, ON P3E 2C6, Canada. ABSTRACT Pulsed electron beam ablation (15 keV, 1 kA, 100 ns) has been used to grow thin films of nanocrystalline diamond on silicon substrates. The films have been grown at room temperature and 150°C, and under argon as the working background gas at a pressure of about 4 mTorr. Visible reflectance spectroscopic analysis has shown films thickness to range between about 55 nm and 115 nm. Visible-Raman spectroscopic measurements have confirmed the presence of sp3 carbon bonds with a substantial fraction in the deposited films, and surrounded by a graphitic phase. The morphological features of the films have been assessed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The films surface is relatively smooth at room temperature and for low thickness, and becomes rougher at high temperature and for thicker films. INTRODUCTION Artificial bulk diamond was first produced in the 1950s from melted graphite under extreme high pressure and high temperature conditions (so called HPHT process) [1]. In the early 1980s, diamond films were produced using chemical vapor deposition (CVD) from carbonaceous gas mixtures and hydrogen (or other halogens) [2, 3], and, ever since, the growth of diamond films has attracted intensive worldwide attention by the research community. Different forms of carbon materials can be made, such as diamond-like carbon (amorphous), polycrystalline diamond, and nanocrystalline diamond. Nanocrystalline diamond (NCD) films possess smooth surface and high sp3 content, and are promising candidates in a broad range of applications, such as optical, electronic, biomedical, tribological [4], and catalytic [5]. In addition to CVD methods, the growth of diamond films has been attempted by physical vapor deposition (PVD) routes. These include sputtering methods [6], ion beam vacuum evaporation methods [7], and pulsed laser deposition methods [8]. Pulsed electron beam ablation (PEBA) has very attractive technical features relatively to other PVD methods due to its versatility and simplicity. Such features include non-thermalequilibrium ablation of virtually all kinds of materials, highly energetic electron beam, highly energetic plasma stream (plume) reaching the substrate, process scalability, low capital/operating cost, and small equipment footprint [9, 10]. PEBA configuration used in the present work is based on a channel-spark process to generate electrons from a hollow cathode, whereby magnetically self-pinched electrons are accelerated through narrow insulating tubes [11]. This article reports on the preparation of thin films of nanocomposites of nanocrystalline diamond on silicon substrates by PEBA method from a carbon target and using argon as the working gas atmosphere. The effect of substrate temperature and number of electron beam pulses on film composition and features were investigated. Experiment
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