Growth time experiments highlight potential for single crystal diamond film optoelectronics

Diamonds hold several unique electronic properties, including high carrier mobility, high dielectric breakdown threshold and excellent broadband optical transmission performance. Single crystal diamond (SCD) has shown potential for next generation optical devices such as optical windows, photoelectric devices, and semiconductors. New work has provided clues about the optical properties and surfaces of one promising type of SCDs.

Zhang et al. announce findings on the changes of surface morphology and optical trasmittance for SCD films during epitaxial growth. After putting the seed crystal through a hydrogen plasma treatment to treat the grooves created when cutting the diamond into films, the researchers homoepitaxially deposited SCDs on a seed substrate under high pressure and high temperature using microwave plasma chemical vapor deposition with growth times of 12, 36 and 84 hours.

The top surface of the epitaxial layer of the crystal exhibited a creased morphology with no polycrystalline rim growth on the side. Inferring from transmittance theory, the researchers conclude that the transmittance of the film was primarily affected by its surface roughness, which in turn was influenced by the growth time.

For longer growth time, the surface roughness of the SCD samples became significantly higher. However, post-polishing may be used for mitigating this feature and improving film transmittance.

Due to the relatively long growth times, a trace amount of silicon impurities was present in the films, which provided photoluminescence at 738 nm. Such findings, the authors state, suggest SCDs like the films they grew might find use in optoelectronic devices.

Source: “Evolution of surface morphology and optical transmittance of single crystal diamond film by epitaxial growth,” by Zhengqiang Zhang, Yatong Song, and Li Gou, AIP Advances (2019). The article can be accessed at https://doi.org/10.1063/1.5118764 .