Surface Oxidation Induced Ferroelectricity and Memristor Like Conductance in Bulk T _d ‐WTe ₂

ABSTRACT

Tungsten ditelluride (WTe ₂ ) is a unique Type‐II semimetal described by the Weyl equation to define its electronic topological band structure and known to show ferroelectricity at room temperature in the bulk phase. In this regard, two competing explanations exist: ferroelectricity arising due to intrinsic non‐centrosymmetric structure analogous to polar metals first proposed by Anderson decades ago, or extrinsic ferroelectricity induced by surface oxidation. Here, we address this question by using a combination of controlled experiments comprising of bulk characterization techniques in conjunction with in situ scribing of the local surface using an atomic force microscopy (AFM) tip to remove the top oxide layer and perform conducting atomic force microscopy (CAFM), Kelvin probe force microscopy (KPFM), and piezoresponse force microscopy (PFM) measurements. Furthermore, ab initio simulations provide supporting findings to corroborate the origin of ferroelectric polarization from switchable interfacial dipoles on the oxidized surface while double loop phase spectrum points to antiferroelectricity in the scribed surface. Our results demonstrate that the observed ferroelectric switching is a surface‐mediated phenomenon associated with the naturally oxidized layer on bulk T _d ‐WTe ₂ , and offering new opportunities for nanoscale manipulation and local characterization using scanning probe microscopy‐based techniques in Weyl and Dirac semimetals.