Progress on Application of Bias Technology for Preparation of Diamond Films

In recent years, heteroepitaxial monocrystalline diamond has been grown by bias voltage technique and its size has been increased to over inch level. Since the application of bias can act as a means to significantly promote nuclear capability of diamound, therefore, the bias voltage technology may be used to prepare oriented diamond films, nano diamond films and ultra-nano diamond films etc. In this paper, the mechanism related with the action of bias technology, the forms and devices of bias technology, as well as the mechanism of surface reaction model, thermal peak model and sublayer injection model are reviewed. The commonly used bias techniques include DC bias, DC pulse bias, pulse overlap bias and bipolar pulse bias. The effect of bias voltage on the microstructure and properties of diamond films are also introduced, and the effect of applied bias voltage on the orientation growth, secondary nucleation rate, amorphous carbon-graphite-diamond phase transition, growth rate and bonding force of diamond films are described in detail. Biasing can change the energy of bombarded particles and the concentration of specific groups, affect the transformation of diamond phase and grain orientation and size, and then affect the optical, mechanical, thermal and electrical properties of diamond films. Some shortcomings in the present research work are also discussed, such as the mechanism related with the action of bias is still not clear, the change of electron concentration and the effect of hydrogen etching are still not clearly explained. Finally, the future research and application directions of bias voltage technology for diamond preparation are also prospected. © 2022, Editorial Office of Chinese Journal of Materials Research. All right reserved.