  g-C3N4 is a novel semiconductor photocatalyst material; however, the low
specific surface area and rapid carrier compliance hinder its photocatalytic
performance. On the other hand, the synthesis of 2D g-C3N4 with high
crystallinity remains challenging. Here, we report the growth of 2D crystalline
g-C3N4 films with thicknesses up to 100 nm on the indium tin oxide substrates
by chemical vapor deposition. The films show high quality, as shown by scanning
electron microscopy and X-ray diffraction, and exhibit intense fluorescence at
room temperature. The optimal growth conditions, such as temperature and
carrier gas flow rate, were achieved by analyzing their effects on the
electronic structure through X-ray absorption spectra and X-ray photoelectron
spectroscopy. By adding thiourea to the melamine precursors, we introduced N
vacancies to achieve band gap modulation and promote carrier separation. This
work provides guidelines for the further improvement of g-C3N4 performance and
for extending its application in the field of photocatalytic devices.
