Selective deposition of nanocrystalline carbon films on GaN diodes in photocatalytic reactions

Abstract

Crystalline carbon films are promising in many applications. However, traditional carbon film deposition methods are limited by involving ultra-high voltage or complicated equipment. In this study, we demonstrate a simple photocatalytic approach to crystalline carbon fabrication. The crystalline carbon is selectively deposited on the anode side of a GaN diode chip immersed in a mixture of CH₃OH and H₂O₂ with sunlight as the only energy source. Diamond and flat hexagonal crystallites are observed by scanning electron microscopy (SEM). Energy-dispersive X-ray (EDX), Raman and Fourier transform infrared (FTIR) spectra further confirm that diamond and graphite crystallites were successfully prepared. Detailed theoretical analysis shows that both H₂O₂ and photon-generated holes play important roles in the crystalline carbon formation. Compared to traditional approaches, the new approach is easy to realize at low cost, has deposition selectivity at the anode side, and requires no strong electric fields. Thus, our approach is novel and promising for preparing crystalline carbon.