Electronic and optical properties of 2D graphene-like compounds titanium carbides and nitrides: DFT calculations

A first principles study of the electronic and optical properties of the graphene-like Tin+1Xn (n=1,2: X= N,C) has been done in the framework of the Density Functional Theory (DFT) to obtain associated quantities as the dielectric function, energy-loss function, reflectivity and absorption spectra. Results infer to a metallic property, stronger for titanium nitrides than titanium carbides owing to an extra electron in nitrogen atom compared to carbon, as well as a decreasing DOS at the Fermi level as the thickness of the layer increases. The optical studies for horizontal E parallel to x and vertical E parallel to z applied fields at low energies (0-20 eV) reveal a forbidden interval of radiation in the real part of the dielectric function along with a non-zero static dielectric amount at zero energy, exclusively definable for the E parallel to z case of course. But in the imaginary part of the dielectric function some peaks are observed owing to the inter-band transitions. For both types of the applied fields, the plasmonic peaks in the energy loss functions of these compounds indicate a reflectivity of 100% in energies less than 1 eV for E parallel to x case, just in contrast to the E parallel to z. (C) 2014 Elsevier Ltd. All rights reserved.