Highly oriented diamond films on heterosubstrates: Current state of the art and remaining challenges

The potential applications of diamond in the field of electronics working under high power and high temperature (aeronautic, aerospace, etc.) require highly oriented films on heterosubstrates. This is the key motivation of the huge research efforts that have been carried out during the last ten years. Very significant progress has been accomplished and nowadays diamond films with misorientations close to 1.5degrees are elaborated on beta-SiC monocrystals. Moreover, an excellent crystalline quality with polar and azimuthal misalignments lower than 0.6degrees is reported for diamond films grown on iridium buffer layers. Unfortunately, these films are still too defective for high power electronics applications. To achieve higher crystalline quality, further improvements of the deposition methods are needed. Nevertheless, a deeper knowledge of the elemental mechanisms occurring during the early stages of growth is also essential. The first part of this paper focuses on the state of the art of the different investigated ways towards heteroepitaxy. Secondly, the present knowledge of the early stages of diamond nucleation and growth on silicon substrates for both classical nucleation and bias-assisted nucleation (BEN) is reviewed. Finally, the remaining questions concerning the understanding of the nucleation processes axe discussed.