Deposition of Diamond Films and Comparative Characterization by Raman, X-Ray Photoelectron, and Positron Annihilation Spectroscopies
Diamond films were grown by hot filament assisted chemical vapor deposition (HFCVD) and characterized by the complimentary techniques of Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), positron annihilation spectroscopy (PAS) and scanning electron microscopy (SEM). Films were grown utilizing two deposition parameter regimes; regime 1 films (growth rates ~ 0.1 mum/hr) were deposited with CH_4/H_2 ratios ranging from 0.25 to 2.0%, and regime 2 films (growth rates ~1.0 mu m/hr) were deposited with CH_4/H _2 ratios ranging from 1.0 to 4.0%. Raman studies of the diamond films from both regimes show the typical evolution from polycrystalline diamond to DLC and graphitic structure with increasing CH_4 concentration. Detailed Raman measurements of diamond peak FWHM values were also done to determine approximate domain sizes in the films. XPS valence spectra show a change in s-p hybridization with CH_4 concentration and an extension of mixing of s electrons from pure s bands to ppi bands in the films. SEM growth studies indicate a linear increase in median particle size with deposition time and a dependence of crystalline orientation on CH_4 concentration. Preliminary PAS lifetime analysis of the films show four possible lifetime components arising due to annihilations from the bulk, surface, and assorted defects within the films. PAS Doppler broadening analyses indicate high crystalline order for the lowest and highest CH _4 concentrations (polycrystalline diamond and microcrystalline graphite respectively) and an excursion from crystallinity for the mid-CH_4 concentrations (mixture of diamond, DLC, and graphitic structures). All characterization techniques show that in both regimes, the highest quality diamond films were obtained for the lowest CH_4 concentration. Results from the initial configuration of the deposition system which yielded DLC films are also presented.
- Pub Date:
- RAMAN SPECTROSCOPY;
- POSITRON ANNIHILATION SPECTROSCOPY;
- Engineering: Materials Science; Physics: Condensed Matter