Evaluation and Improvement of the Adhesive Fracture Toughness of CVD Diamond on Silicon Substrate

Abstract

CVD diamond particles were produced on silicon substrates under various conditions such as different methane concentration in the source gas mixture and the substrate temperature. Adhesive fracture toughness of these diamond particles was evaluated. It was confirmed that the adequate control of methane concentration could improve the toughness by almost five times. Discussion is further focused on the difference in the composition of the particles with different levels of adhesive fracture toughness. The graphite content in the diamond particle seems to be closely related to the enhancement of adhesive fracture toughness. Detailed microscopic observations were also carried out on the fracture morphology of the interface and the cross-sections of the diamond particles. Finally, the nanoscale crystalline structure of diamond particles is found to play an important role on the adhesive fracture toughness.