Diamond heteroepitaxy on Ir / SrTiO3 / Si (001) substrates: from nucleation to thick films characterizations

The up-scaling of heteroepitaxial diamond remains one challenge for the development of power electronics. One option is to consider heterosubstrates compatible with silicon based technologies, such as Ir / YSZ / Si [1]. We have developed diamond heteroepitaxy on iridium buffer layers grown on SrTiO3 / Si (001) [2]. The SrTiO3 has a low lattice mismatch with Ir (1.7 %) whereas the silicon substrate ensures a closer thermal expansion mismatch with diamond. This study provides an extended characterization of the heteroepitaxial process on SrTiO3 / Si (001): from the iridium deposition, to the bias enhanced nucleation (BEN) and the growth of heteroepitaxial diamond films (200 nm up to 240 m thick). High quality iridium buffer layers were grown on SrTiO3 / Si (001) with mosaicities of 0.3° (polar) and 0.1° (azimuthal) according to XRD. After the BEN step, the surface and the interfaces of Ir / SrTiO3 / Si (001) multilayer were investigated by SEM and HRTEM in cross-section. The morphology and the crystalline quality of a 200 nm thick heteroepitaxial diamond film were characterized using SEM and UV Raman. A cross-section of this film was investigated by High Resolution TEM. Thicker diamond films were grown under MPCVD growth conditions close to homoepitaxy [3]. Structural and chemical characterizations of diamond heteroepitaxial films grown on Ir / SrTiO3 / Si (001) were performed by XRD, Raman and Cathodoluminescence. The obtained results demonstrate the potential of Ir / SrTiO3 / Si (001) to achieve heteroepitaxial diamond films with characteristics at the state-of-the-art. The up-scaling has already proved successful allowing the substrate size to be increased from 5x5 to 7x7 mm2. References [1] M. Schreck et al., MRS Bulletin 39 (2014) 504 [2] K. H. Lee et al., Diam. Relat. Mater. 66 (2016) 67. [3] J. Achard et al., J. Phys. D, 40 (2007) 6175