Mechanical behavior of BDD films after different heat treatments

Abstract

The applications of diamond are limited by its brittleness although it has numerous remarkable properties. The in-situ hydrogen plasma treatment and vacuum annealing were investigated to improve the mechanical properties of boron-doped diamond (BDD) films. Before and after different heat treatments, the surface morphologies , phase composition, and microstructure of BDD films were characterized by SEM, Raman spectroscopy , and TEM, respectively. The results show that vacuum annealing can increase the defect density of BDD due to the formation of more twins. On the contrary, in-situ hydrogen plasma treatment is beneficial to reduce defects such as twins. The nano-indentation test results demonstrate plastic deformability of BDD film is significantly improved after vacuum annealing with a decrease of 38.3% in H 3 /E 2 and an increase of about 59.1% in plasticity index PI value. In contrast, the role of in-situ hydrogen plasma treatment is just the opposite, which leads to a high hardness due to lower defects. • The lattice distortion and defects of BDD films reduced after the H plasma treatment. • Many twins and large-angle grain boundaries occurred after the V annealing. • The change of mechanical properties is closely related to the defects of BDD films.