Polycrystalline diamond films were deposited on quartz (fused silica), glass and Si substrates by chemical vapour deposition of Freon 22 (CHF 2 Cl≤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 3.7-3.95 eV on glassandE g 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 525-725 K) were 5.6-6.0 10 - 3 and 4.9-5.7 GPa, respectively. With variation of freon content (≤10 vol%) in the gas mixture the strain and stress on quartz substrate (for T s 725 K) varied within 1.6-8.0 10 - 3 and 1.5-7.8 GPa, respectively. The films were found to be scratch resistant for higher deposition temperature (T s ≥700 K) and lower freon content (∼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%.