Optical properties of graphitic carbon nitride films prepared by evaporation

Graphitic carbon nitride (g-C3N4) consists of two-dimensional sheets of carbon and nitrogen atoms. Films of g-C3N4 were prepared by evaporating guanidine carbonate at four different substrate temperatures. The optical absorption band of the films appears at 33 eV and the optical energy gaps are calculated to be 2.83-2.90 eV. Band intensity increases with increasing substrate temperature, but the energetic band position does not shift. The photocurrent of g-C3N4 films can be observed by irradiation with monochromatic light. While the photosensitivity spectra are in almost complete correspondence with the optical absorption spectra, it is also found that the photocurrent is generated by irradiation at photon energies below the optical energy gap down to 2.5 eV. (C) 2016 Elsevier B.V. All rights reserved.