High quality thick CVD diamond films homoepitaxially grown on (111)-oriented substrates

• High-power PACVD growth was carried out on (111) HPHT substrates prepared form octahedral-shape crystals.
• Smooth films up to 100 μm thick were successfully obtained at 6 μm/h for the first time.
• Under high temperature and low methane concentration (low alpha) twinning is efficiently inhibited.
• Thick (111) CVD films showed low impurity concentration by photoluminescence.
• Cathodoluminescence showed a reduced crystalline quality compared to films grown on conventional (100) orientation.

The development of diamond power electronic devices based on p–n junctions strongly relies on the ability to achieve efficient n-type doping which has so far been the limiting step. (111)-oriented diamond films offer the advantage of a higher activity and incorporation of dopants. In this respect, growing high-quality films by Plasma Assisted Chemical Vapour Deposition (PACVD) on this orientation is critical. Other applications such as those based on nitrogen-vacancy (NV) centres could also benefit from the availability of high-quality (111)-oriented substrates. Due to the preferential orientation of the NV bond along the < 111 > direction, higher emission intensity and easier alignment of the magnetic field are expected. However (111) CVD films are plagued by twinning and defects that are easily formed on this orientation. Good quality (111) CVD films have been obtained but only for low thicknesses (< 1 μm) and at extremely low growth rates.In this paper, diamond growth was carried out by high power PACVD on (111)-oriented high pressure high temperature substrates prepared from octahedral-shape crystals. It was found that under conditions of high temperature and low methane concentration, the growth rate in the < 100 > direction is almost completely inhibited which ensures that penetration twins cannot develop. In this case smooth films with a thickness over 100 μm were successfully obtained at 6 μm/h. Although the crystalline quality is still below that of conventional (100) CVD films, the growth of such thick (111) CVD films opens the way to their integration into electronics applications.

Low defect thick (111) CVD diamond film obtained under low α value (microscope and luminescence images).Figure optionsDownload as PowerPoint slide