Effects of Crystallite Orientation on the Oxidation of MoS2 Thin Films.
AEROSPACE CORP EL SEGUNDO CA CHEMISTRY AND PHYSICS LAB
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Thin films of MoS2 have been prepared, by rf sputter deposition, with different microstructures that show markedly different susceptibilities to oxidation or other environmental degradation. The films were exposed to air atmospheres of variable relative humidity, and the extent of oxidation was measured by means of Auger electron AES and X-ray photoelectron XPS spectroscopies. The morphologies of the films were determined by transmission electron microscopy. Depths of oxidation of the thin films were calculated from changes in AES peak-to-peak height ratios and in XPS peak intensity ratios through the use of standard escape-depth models for attenuation of electron emission by a layer of reacted material in the present case, MoO3. The results show that MoS2 films whose crystallites are oriented with their basal planes at random angles to the plane of the substrate surface designated Type I films are oxidized to depths equal to or greater than 300 A, whereas films whose crystallite basal planes are coplanar with parallel to the substrate surface Type II films are oxidized to a maximum depth of 10 to 15 A. These results are interpreted in terms of relative reactivities of edge versus basal planes of the MoS2 crystallites. Keywords Molybdenum disulfide Solid lubrication Thin-film chemistry Thin-film oxidation Crystallite orientation.
- *SOLID LUBRICANTS
- PEAK VALUES
- THIN FILMS
- ELECTRON MICROSCOPY
- ELECTRON EMISSION
- X RAY PHOTOELECTRON SPECTROSCOPY
- AUGER ELECTRON SPECTROSCOPY
- MOLYBDENUM COMPOUNDS
- Inorganic Chemistry
- Atomic and Molecular Physics and Spectroscopy