The effect of nitrogen on pulsed laser deposition of amorphous silicon carbide films: Properties and structure
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The effect of nitrogen on pulsed laser deposition of amorphous silicon carbide films: Properties and structure Andrew L. Yee,a) H. C. Ong, Fulin Xiong,b) and R. P. H. Chang Department of Materials Science and Engineering, Northwestern University, 2225 North Campus Drive, Evanston, Illinois 60208 (Received 16 February 1995; accepted 1 April 1996)
The influence of nitrogen on amorphous silicon carbide films deposited at room temperature using pulsed laser ablation has been investigated. Depositions were carried out either in ultrahigh vacuum or in a nitrogen ambient ranging from 10 to 100 mT. The mechanical and optical properties, as well as composition and structure of the resulting films, were evaluated using a variety of analytical techniques. Vacuum-deposited films exhibited high hardness but suffered from high compressive stresses (.1 GPa). At low nitrogen background pressures (,30 mT), films with an optimum balance among hardness (,16 GPa), adhesion, and intrinsic stress (,220 MPa) were found, making them ideal candidates for protective coating applications. As nitrogen pressure was increased, mechanical performance degraded due to the increasing amount of SiO2 found in the films as evidenced by spectroscopic ellipsometry, infrared spectroscopy, and Auger electron spectroscopy measurements. The source of oxygen is attributed to residual water vapor present in our vacuum system. Optical emission spectroscopy was used to confirm the presence of Si–O species in the laser-induced plasma plume.
I. INTRODUCTION
Amorphous carbon-based films have been actively studied in order to control their mechanical, optical, and electrical properties.1–7 As a result, amorphous films have found potential applications as a coating material for optical windows,4 tool bits,5 and magnetic recording media.6 Amorphous films based on the Si –C–N system are explored in this report in order to produce a viable protective coating suitable for a variety of substrate materials. Amorphous SiC films with components of Six Ny or possibly even Cx Ny7 are expected to possess favorable mechanical properties. Moreover, the incorporation of nitrogen in carbon-containing amorphous films has also been reported to reduce intrinsic film stress.8,9 Reduction and control of intrinsic film stress are necessary in order to deposit overcoating with desired hardness and thickness without spontaneous film cracking or delamination. To this end, films have been deposited using pulsed laser ablation of a CVD a –SiC target either in vacuum or in a nitrogen ambient at room temperature. In order to optimize the deposition conditions, films were deposited in a range of nitrogen background pressures. Mechanical and optical properties were investigated as a function of nitrogen pressure. The changes in the mechanical behavior could then be related to the variation in the
a) Present b)
address: Intel Corporation, Ocotillo, Arizona 85266. Present address: 3M Corporation, St. Paul, Minnesota 55144. J. Mater. Res., Vol. 11,
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