Characterization of diamond thin films: Diamond phase identification, surface morphology, and defect structures
- PDF / 2,305,429 Bytes
- 12 Pages / 593.28 x 841.68 pts Page_size
- 31 Downloads / 251 Views
Thin carbon films grown from a low pressure methane-hydrogen gas mixture by microwave plasma enhanced CVD have been examined by Auger electron spectroscopy, secondary ion mass spectrometry, electron and x-ray diffraction, electron energy loss spectroscopy, and electron microscopy. They were determined to be similar to natural diamond in terms of composition, structure, and bonding. The surface morphology of the diamond films was a function of position on the sample surface and the methane concentration in the feedgas. Well-faceted diamond crystals were observed near the center of the sample whereas a less faceted, cauliflower texture was observed near the edge of the sample, presumably due to variations in temperature across the surface of the sample. Regarding methane concentration effects, threefold {111} faceted diamond crystals were predominant on a film grown at 0.3% CH4 in H2 while fourfold {100} facets were observed on films grown in 1.0% and 2.0% CH4 in H2. Transmission electron microscopy of the diamond films has shown that the majority of diamond crystals have a very high defect density comprised of {111} twins, {111} stacking faults, and dislocations. In addition, cross-sectional TEM has revealed a 50 A epitaxial layer of /3—SiC at the diamond-silicon interface of a film grown with 0.3% CH4 in H2 while no such layer was observed on a diamond film grown in 2.0% CH4 in H2. I. INTRODUCTION Diamond is an excellent candidate material for use in both electronic and wear resistant coating applications due to its exceptional hardness, strength, thermal conductivity, electron saturated drift velocity, hole and electron mobilities, chemical and thermal stability, radiation hardness, and optical transmission.1"3 Electronic devices of particular interest include high power/high frequency devices and devices to be utilized in high temperature, chemically harsh, and/or high radiation flux environments. Recent developments in the growth of diamond films from low pressure (i.e., less than one atmosphere) gases have made the fabrication of such devices a real possibility, particularly since it has been shown that epitaxial diamond films can be grown on diamond substrates.4"9 However, for diamond to reach its true potential, high quality monocrystalline films must be grown on economically viable, non-diamond substrates. Judging from various previous investigations, this is a formidable task since numerous experiments have yielded only highly defective, poly crystalline films to date. Therefore, to achieve high quality, monocrystalline films, we must gain a greater understanding of the nucleation and growth of diamond by thoroughly characterizing the films achieved to date. The information obtained from this characterization can then be fed back to the growth of these films to improve film quality and properties. Diamond films have now been grown on various substrates (i.e., Si, SiO2, A12O3, /3-SiC, a-SiC, Cu, Mo, W, WC, and Ni) by several different methods including hot filament enhanced chemical vapor deposition (CVD),10
Data Loading...
