First-principles study of the electronic, optical and transport of few-layer semiconducting MXene

M 2 CO 2 (M = Ti, Zr or Hf) MXene structures. The monolayer and multilayer two-probe M 2 CO 2 (M = Ti, Zr or Hf) p-n devices. • The band gaps decrease with the increasing layer number or E-field for MXenes. • The optical absorption for MXenes is higher in the visible and ultraviolet range. • The single and multilayer Ti 2 CO 2 p-n devices show a typical diode behavior. By combining the density functional theory and nonequilibrium Green’s function, we have studied the electronic, optical and transport properties of multilayer two-dimensional (2D) semiconducting MXenes. Firstly, the band gaps of multilayer MXenes are investigated under an external transverse electric field. Our results show that the band gaps slightly decrease with increasing of number of layers and the increasing electrical field strength. Next, the layer number dependent real and imaginary parts of the dielectric functions for these semiconducting MXenes are predicted, which indicates the larger absorption in both the visible and ultraviolet spectral ranges. Lastly, the transport properties of multilayer M 2 CO 2 (M = Ti, Zr, or Hf) p-n devices are studied. The Ti 2 CO 2 p-n devices show higher conductance than the others, and a typical behavior for conventional diodes of all systems are also clearly observed.