Low temperature synthesis of spherical nano-diamond

Thin film nano-diamonds have been synthesised using CH4/H2 mixture by micro-wave plasma enhanced CVD (MW-PECVD) at a substrate temperature as low as 250°C. These are found to be spherically shaped, homogeneously distributed on the film surface (size ∼100 nm) and are related to ball-like or ballas-like nano-diamonds. With the increment of temperature from 200°C to 250°C, these spherical structures are found to form in increasing number density, but the same could not be grown with the variation of power and pressure. However, the bulk material is found to improve in crystallinity with the increment of pressure and highly polycrystalline nano-diamonds (111), along with Graphitic [(100), (004)] inclusions, have been grown using a gas pressure of 70 Torr and 500 W of MW power. The preliminary results on FE-SEM, Raman and HR-TEM studies are discussed here. Further developments of the material and characterisation are in progress.