Tuning the Electrical Conductivity of Ti2CO2 MXene by Varying the Layer Thickness and Applying Strains

MXenes have attracted intensive attention because of their widespread applications. As a well-studied member of the MXene family, Ti2CO2 has been demonstrated to be semiconducting with ultrahigh carrier mobility, acting as a candidate material for electronic devices. In this work, the influence of layer thickness on the electrical conductivity of Ti2CO2 is investigated combined with first-principles density functional calculations and the Boltzmann transport theory. Because of the layer interaction-induced band splitting, the band gap of Ti2CO2 generally decreases with increasing layers. Based on the generalized gradient approximation, the band gap in monolayer Ti2CO2 is determined to be 0.260 eV, which decreases to 0.0369 eV in the five-layer configuration. Further, the strain influence on the electronic structure of the multilayer Ti2CO2 is studied. With increasing compression strains perpendicular to the basal plane, the configuration is found to transform from a semiconductor to a semimetal, then to a semiconductor, and at last to a metal. This result implies that the electronic property of the multilayer Ti2CO2 can be efficiently manipulated by strain and that the multilayer configurations could be applied in strain sensors. Moreover, our work may open a door to realize bulk semiconductors through compression of accordion-like multilayer MXenes.