Electronic transitions and vibrational properties of bulk and monolayer g-C3N4, and a g-C3N4/MoS2 heterostructure from a DFT study

Abstract

Successful recognition of a dynamically stable carbonitride structure revealed that unlike other planar layered structures in the case of g-C₃N₄ the stable configurations are distorted [J. Wang et al., Chem. Mater., 2017, 29(7), 2694–2707, DOI: https://doi.org/10.1021/acs.chemmater.6b02969.]. This generates interest in a detailed study of the possibilities of controlling the structure and its properties both in its pristine and heterostructure forms. Here, we present the results of the investigation of dynamically stable bulk and monolayer g-C₃N₄, and a g-C₃N₄/MoS₂ heterostructure. The bulk g-C₃N₄ was found to be an indirect band gap semiconductor exhibiting an indirect-to-direct band gap transition upon dimensionality reduction. In the case of the heterostructure, the analysis of partial density of states shows a charge transfer from nitrogen ions in g-C₃N₄ to the MoS₂ layer. The Raman spectra of bulk g-C₃N₄ are discussed in detail, and the changes occurring in the spectra upon the transition to the monolayer form and in the g-C₃N₄/MoS₂ heterostructure are demonstrated. It was found that the characteristic features of such an atomic transition can be seen in the region below 300 cm⁻¹ and between 700 and 800 cm⁻¹.