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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. [ABSTRACT FROM AUTHOR]

We have reported the density functional theory investigations on the monolayered, 2 layered and bulk MoSi2N4 in three structural modifications called α1 [Y.-L. Hong, et al., Chemical Vapor Deposition of Layered Two-Dimensional MoSi2N4 Materials, Science, 2020, 369(6504), 670–674, DOI: 10.1126/science.abb7023], α2 and α3 [Y. Yin, Q. Gong, M. Yi and W. Guo, Emerging Versatile Two-Dimensional MoSi2N4 Family, Adv. Funct. Mater., 2023, 2214050, DOI: 10.1002/adfm.202214050]. We showed that in the case of monolayers the difference in total energies is less than 0.1 eV between α1 and α3 phases, and less than 0.2 eV between α1 and α2 geometries. The most energetically favorable layer stacking for the bulk structures of each phase was investigated. All considered modifications are dynamically stable from a single layer to a bulk structure in energetically favorable stacking. Raman spectra for the monolayered, 2 layered and bulk structures were simulated and the vibrational analysis was performed. The main difference in the obtained spectra is associated with the position of the strongest band which depends on the Mo–N bond length. According to the obtained data, we can conclude that the Raman line at 348 cm−1 in the experimental spectra of MoSi2N4 can have more complex explanation than just Γ-point Raman-active vibration as was discussed before in [Y.-L. Hong, et al., Chemical Vapor Deposition of Layered Two-Dimensional MoSi2N4 Materials, Science, 2020, 369(6504), 670–674, DOI: 10.1126/science.abb7023]. [ABSTRACT FROM AUTHOR]

The structural and physicochemical properties of the MoSe2/PTCDA heterostructure, which consists of two-dimensional inorganic and molecular organic semiconductors, have been studied theoretically. Features of change in the electronic properties of the PTCDA monomolecular layer on the MoSe2 surface have been described by density functional theory. The quantitative analysis of charge transfer between the heterostructure components has explained the features of coupling between the layers. The study of the optical characteristics of the heterostructure has revealed the enhancement of the absorption spectrum in the infrared range. Consequently, MoSe2/PTCDA heterostructures are promising for applications in electronics, optoelectronics, and materials for the utilization of solar energy. [ABSTRACT FROM AUTHOR]

The structural and physicochemical properties of the MoSe2/PTCDA heterostructure, which consists of two-dimensional inorganic and molecular organic semiconductors, have been studied theoretically. Features of change in the electronic properties of the PTCDA monomolecular layer on the MoSe2 surface have been described by density functional theory. The quantitative analysis of charge transfer between the heterostructure components has explained the features of coupling between the layers. The study of the optical characteristics of the heterostructure has revealed the enhancement of the absorption spectrum in the infrared range. Consequently, MoSe2/PTCDA heterostructures are promising for applications in electronics, optoelectronics, and materials for the utilization of solar energy. [ABSTRACT FROM AUTHOR]