O-Vacancy-line defective Ti2CO2 nanoribbons: novel magnetism, tunable carrier mobility, and magnetic device behaviors

摘要

MXenes are well-known two-dimensional (2D) materials that have attracted increasing attention recently due to their excellent physical and chemical properties. However, most MXenes lack magnetism or useful magnetic features. Therefore, inducing magnetism and/or tuning it to obtain distinguished performance of MXenes is an interesting but challenging task. Here, we propose O-vacancy-line (OVL)-defective armchair-edged Ti2CO2 nanoribbon structures, where the OVL may be formed in the fabrication process or by chemical etching or high-energy atom/ion/electron beam bombardment. The higher stability of these structures is indicated by their calculated binding energies, phonon spectra, and molecular dynamics simulations. Calculations based on density functional theory show that the pristine ribbon is a nonmagnetic semiconductor; however, significant magnetism can be induced in the OVL-ribbon, which is attributed to the emergence of unpaired electrons due to distortion of the ribbon and charge redistribution after the introduction of the OVL. In particular, in the ferromagnetic ground state, outstanding magneto-electronic properties such as bipolar magnetic semiconductor, half-semiconductor, or half-metal behavior depending on the OVL position are predicted. More interestingly, the OVL can substantially modulate the carrier mobility of the ribbon, presenting OVL position-dependence as well as carrier polarity and spin polarity as mobility features of the ribbon. Furthermore, an OVL-ribbon-based device promises a perfect double spin-filtering effect and excellent dual spin diode properties. Therefore, our work suggests that fabricating an OVL on Ti2CO2 MXene ribbons is an effective strategy for engineering their magnetic features and developing on-demand MXene spintronic nanodevices.