Optical properties of diamond film deposited by CVD of Freon: Studies on mechanical properties from the absorption band tail

Polycrystalline diamond films were deposited on quartz (fused silica), glass and Si substrates by chemical vapour deposition of Freon 22 (CHF2Cl less than or equal to 10 vol%) and hydrogen with substrate temperature in the range 525-725 K. Films were sp(3) rich (85-95%) with high band gap (E-g approximate to 3.7-3.95 eV on glass and E-g approximate to 4.5-5.5 eV on quartz). The strain and stress in the films were determined from the broadening of the optical absorption edge. The variations of strain and stress on glass with deposition temperature (T-s approximate to 525-725 K) were 5.6-6.0 x 10(-3) and 4.9-5.7 GPa, respectively. With variation of freon content (less than or equal to 10 vol%) in the gas mixture the strain and stress on quartz substrate (for T-s approximate to 725 K) varied within 1.6-8.0 x 10(-3) and 1.5-7.8 GPa, respectively. The films were found to be scratch resistant for higher deposition temperature (T-s greater than or equal to 700 K) and lower freon content (similar to 1-2 vol%) in the feed gas. The hardness in the films was observed to decrease from 71 to 63 GPa with increase of freon content from 2-10 vol%. (C) 1997 Elsevier Science S.A.