Optical and Electronic Structural Properties of Cu₃N Thin Films: A First-Principles Study (LDA + U)

Abstract

A comprehensive study on the electronic structure and optical properties of a Cu 3 N film is performed by the firstprinciples study using density functional theory. The Hubbard (U) term is added in the local density approximation approach for improvement of the theoretical band gap energy. The band structure of the Cu 3 N unit cell shows a strong hybridization of Cu 3d and N 2p orbitals in the near-valence band region (M) because of their antibonding states which are also observed by molecular orbitals (HOMO−LUMO). The conduction band is dominated by a very small amount of Cu 3p and N 2p orbitals. The density of states exhibits a negligible deformation in Cu−N bonding. The Cu 3 N thin film deposited by the DC magnetron-sputtering technique shows a polycrystalline structure with a nonstoichiometric Cu 3 N phase. The experimentally obtained optical band gap and refractive index of the Cu 3 N film are 1.44 eV and 2.14, respectively, which are comparable with those from the theoretical approximation.

Preparation and DFT studies of chiral Cu (I)-complexes of biphenyl bisoxazolines and their application in enantioselective Kharasch–Sosnovsky reaction

“…In the following, to compare the chemical activity of the complexes, the HOMO–LUMO energy gaps of the ( S, a S,S ) complexes were calculated 74 , 75 . In fact, the lower the HOMO–LUMO gap, the higher the chemical activity.…”

Construction of nanorod-shaped TiO2/Cu3N p–n heterojunction for efficient visible-light hydrogen evolution

“…The Hubbard-U correction was performed for the improvement of underestimated band-gap, namely, 7 eV for Ti 3d, 6.8 eV for Cu 3d and 10 eV for O 2p. [30][31][32] Structural optimization with dipolecorrection was accomplished until the force of all atoms was less than 0.005 eV Å À1 . The self-consistent convergence criterion was set to 2 Â 10 À6 eV per atom.…”

Application of Copper-Based Compounds in Energy Conversion and Catalysis

“…The band gap of the above CuO nanoparticles is estimated to be 1. (VBM) and conduction band minimum (CBM) are located at R and M points, respectively, informing an indirect band gap of 1.4 eV [26]. Ultraviolet photoelectron spectroscopy (UPS, Figure 12(c)) reveals that the VBM of Cu 3 N located at 0.42 eV below E F , UV-visible (UV-vis) absorption spectrum measurement (Figure 12 (d)) gives the optical band gap to be 1.92 eV, then CBM should be located at 1.50 eV above E F .…”