Growth of well-adhered and smooth diamond thin films on fused silica substrates

Fused silica substrates were pretreated by ultrasonic vibration in diamond powder slurry. Under the appropriate pretreatment and growth conditions, the diamond nucleation density of higher than 10 10 cm −2 was obtained. The average diamond grain size was ca. 150 nm, and continuous diamond thin films with smooth surfaces (average surface roughness ca. 6 nm) were synthesized by a four-step process using the hot filament chemical vapor deposition (HFCVD) technique. The optical transmittance of diamond thin films was 73–84% in the longer wave range (1–5 μm). The adhesion of diamond thin films grown 3 years ago is still good and the mechanism is briefly discussed.