Processing of multilayer microcrystalline and nanocrystalline diamond thin films using Ar-rich microwave plasmas

This article lays the foundation for the development of microwave plasma chemical vapor deposition process conditions for synthesizing multilayered microcrystalline and nanocrystalline diamond (MCD and NCD) thin films. The effects of gas composition and the diamond seeding medium are correlated with the film morphology and diamond phase purity. Results of process optimization experiments using single-layer diamond deposition indicate that for high gas-phase Ar content (≥90%) the film quality improves with reduced Ar content and with increasing thickness reaching a plateau above a thickness of ∼2 μm. Multilayer diamond deposition experiments with two different seeding media (25 nm and 1 μm) clearly show that it is feasible to selectively synthesize alternating MCD (60% Ar) and NCD (95% Ar) layers with good control of film quality and morphology, thereby setting the stage for development of multilayered diamond thin films with tailored properties for thermal management applications.