Study on enhancement of diamond nucleation on fused silica substrate by ultrasonic pretreatment

Fused silica substrates were pretreated by the ultrasonic vibration in the diamond powder slurry (UVDS). The influence of UVDS parameters such as the grain size of diamond powder, the liquid medium used to form the slurry, the weight ratio of diamond powder to liquid medium and the pretreatment time on the diamond nucleation density (DND) were systemically investigated. The grain size of diamond powder greatly affected the DND. the larger the grain size the higher the DND in our experiment conditions. The DND was about the same using acetone or ethanol of hexane medium. The best weight ratio of diamond powder (grain size 20-40 mum) to liquid medium was similar to1/60. Under appropriate pretreatment and CVD conditions, the DND of similar to10(10) cm(-2) was obtained on fused silica substrates. Continuous ultra-thin diamond films with uniform and smooth surface (diamond grain size: similar to150 nm and surface toughness: similar to6 nm) were synthesized in an improved hot filament chemical vapor deposition (HFCVD) system. Nano-damaged sites on the pretreated surface mainly enhanced the DND and shortened the incubation time of nucleation. (C) 2003 Elsevier B.V. All rights reserved.