Weak-Localization Phenomena as a Tool for Quantification of Defects in MXenes and 2D Metallic Nanolayers

Weak localization¹ (WL) is a quantum phenomenon, where at cryotemperatures, electrons in the metal move around a closed loops and return to their initial point of origin rather than proceeding forward in the lattice, which increases resistivity of metal with decreasing temperature. Typically, metals with defects exhibit transition from normal metallic conductivity to WL regime at low temperatures. In this study, we introduced defects in MXene flakes, such as vacancy clusters and flake boundaries and measured the temperature and field dependence of the resistivity in 2D metallic MXene films. We observed the transition temperature to WL state increases with increasing the amount of defects in MXene flakes. Properties of the 2D nanosheets were also studied by complementary experiments such as XRD, AFM and SEM. Our results indicated that measurements of the temperature and field dependencies of resistivity, can be used as a sufficient and superior technique to understand the amount of defects in the MXenes and 2D metal nanosheets in general, by determining coherence length of electrons at low temperatures in the WL regime. We thus present how the overall quality of 2D flakes in MXene films can be determined by investigating their transport properties. This technique gives a broader picture of MXene defects compared to more localized defect characterization techniques such as transmission electron microscopy.<br/><br/><br/>1. Falko, V. I. <i>et al.</i> Weak localization in graphene. <i>Solid State Commun</i> <b>143</b>, 33–38 (2007).