Multi-Energy Processing for Novel Coating Technologies.

摘要

Due to the wide range of superior properties, diamonds are of great interest in industry applications and scientific research. The inherent shortcomings of conventional chemical vapor deposition (CVD) methods and the ever-increasing demand for diamonds urge extended efforts for further enhancement of diamond deposition without compromising the diamond quality. Conventional CVD processes, which rely on thermal heating, are inefficient energy coupling routes to drive gas reactions. As an intensive, coherent and monochromatic light, lasers are ideal candidates for exploring alternative energy coupling pathways. To address these challenges, the research efforts mainly focused on laser incorporation in combustion CVD of diamond films which ed to: 1) promoted energy coupling efficiency; 2) enhanced diamond deposition- 3) controlled crystallographic orientations; and 4) identified roles of active species in combustion CVD of diamond films. Pure diamond and nitrogen(N)-doped diamond films were deposited using combustion flames assisted by infrared-laser (IR-laser) vibrational excitations of ethylene and ammonia (NH,) molecules, respectively. Vibrational excitations of precursor molecules were realized using a kilowatt wavelength-tunable CO2 laser with a spectrum range from 9 2 to 10 9 urn On-resonance excitation of the CH^-wagging mode of ethylene (C2H4) molecules was demonstrated to be more efficient than off--resonance excitations in promoting the deposition rate and improving the diamond quality, attributed to a higher energy coupling efficiency Ro-vibrational excitations of C2H4 molecules enabled crystallographic control in {100}-textured diamond film deposition. Micro-crystalline N-doped diamond films with a high doping concentration were deposited using an ammonia-added oxyacetylene flame assisted by IR-laser vibrational excitations of the NH-wagging mode of NH3 molecules.