Chemical vapor deposition synthesis of two-dimensional freestanding transition metal oxychloride for electronic applications

Abstract

Two-dimensional transition metal oxychlorides (MOCl, $M$ = Fe, Cr, V, Ti, Sc) with the metal-oxygen plane sandwiched by two layers of chloride ions possess many exotic physical properties. Nevertheless, it is of great challenge to grow two-dimensional single-crystal MOCl because polyvalent nature of transition metal elements usually gives rise to mixed oxyhalides compounds with distinct physical properties. Here, we take VOCl as an example to present a solution for synthesizing 2D freestanding MOCl with various thicknesses through chemical vapor deposition (CVD) method. The single crystal and elementary composition as well as elements ratio of as-grown samples have been characterized through measurements of X-ray diffraction, X-ray photoelectron spectroscopy and energy-dispersive spectroscopy, respectively. Furthermore, we demonstrate that 2D VOCl-based memristive devices show low power consumption and excellent device reliability due to the layered-structure and electrically insulating properties of 2D VOCl flakes. Besides, we utilize the feature of multilevel resistive switching that memristive devices exhibit to emulate depression and potentiation of synaptic plasticity. This method developed in this study may open up a new avenue for the growth of 2D MOCl with single crystal and pave the way for high-performance electronic applications.