Mechanical behavior of BDD films after different heat treatments

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 H3/E2 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.