1. IAA-99-IAA.12.1.02 DIAMOND FILM DEPOSITION BY CHEMICAL VAPOR TRANSPORT Liya L. Regel and William R. Wilcox International Center for Gravity Materials Science and Applications, Clarkson University, Potsdam, New York 13699-5814, USA International Astronautical Congress Amsterdam, October 1999

2. Some current and many potential applications for diamond films. Improvements needed. Techniques and apparatus will be described. Deposited on silicon, molybdenum, graphite, carbon felt and glass without typical pre- treatment with diamond powder. Selective deposition on copper pattern on oxidized silicon Deposition enhanced by centrifugation. Modeling and current understanding: radiation heat transfer, buoyancy convection, surface and gas chemistry.

3. Current applications of CVD diamond Heat spreaders for semiconductor devices, photonic devices, high-power amplifiers and Multi Chip Modules Hard coatings for tools for cutting, grinding, microdrilling, etc. Highly transparent hard windows useful from the infrared to the ultraviolet, and as a radome. Chemically resistant coatings, e.g., for biomedical implants. Cold-cathode field emitters for flat panel displays, electron guns, amplifiers, oscillators, miniature x-ray sources, etc. High frequency speaker diaphragms.

4. Techniques Previous techniques use flowing hydrogen gas at ~1/10 atm containing ~1% methane. Either a hot tungsten filament or a plasma is used to generate H atoms and C-containing deposition species. Nucleation is often difficult and sometimes requires diamond powder. Deposition rates are ~1 micron/hr. Our new technique uses hydrogen at ~1/10 atm in a sealed chamber. Hot graphite generates both hydrogen atoms and carbon-containing deposition species. Seems to nucleate on anything without special surface treatment. Deposition rate can be ~10 micron/hr. Appears to be self regulating.

5. This shows the original apparatus. A larger apparatus has been constructed with improved cooling and better control. Power requirement about 300 watts -- a large light bulb!

6. Complete coating on entire 8.8 sq cm Mo sheet. Grain size ~0.4 micron.

7. Optical interference pattern from fine- grained deposit on molybdenum

8. Diamond deposited on roughened (111) silicon for 40 minutes under different conditions.

9. Deposition of diamond on graphite Before deposition After deposition

10. Selective deposition of diamond on copper pattern on oxidized silicon Cu pattern (lighter color) After deposition

11. Comparison of temperature distribution in chamber with silicon and glass substrates.

12. Comparison of convection field in chamber with silicon and glass substrates.

13. Equilibrium compositions versus temperature.