High Rates of Diamond Deposition with Various Crystals Sizes by Combustion Flame Method

Abstract

A combustion-flame method is used to nucleate and grow various forms of polycrystalline diamond under ambient atmosphere. A two-colour pyrometer gives information to the system which monitors the stabilisation of the substrate temperature in the deposition zone. The deposition parameters are significantly controlled, leading to high quality and reproducibility of the diamond growth. This study has shown that the crystal growth, the texture and the physical properties of diamond films are strongly dependent on the processing conditions. At normal growth conditions (deposition under laminar flow) and in the first step of deposition, the growth rate and the diamond crystals size increase with the substrate temperature. At high substrate temperature deposition (Ts=900°C), the average crystals size reaches 30 μm and the growth rate is about 500 μm/h. The growth rate decreases with the times deposition but the crystal size continues to increase with the thickness of the deposited film. When the total gases flow is increased to the turbulent state, the deposition leads to very fine crystals (about 1 μm) with good quality. In that case, the growth rate reaches 700 μm/h. A model of crystal growth is proposed to explain this phenomenon.