Electrodeposition of 2D layered tungsten diselenide thin films using a single source precursor

Abstract

The development of area-selective, scalable deposition methods for the anisotropic growth of transition metal dichalcogenide (TMDC) thin films with a planar morphology is essential for their practical applications in integrated electronic and optoelectronic devices. In this work, we report on the electrodeposition of layered WSe₂ from a single source molecular precursor, containing both W and Se, for the first time. Using WSeCl₄ in an acetonitrile (MeCN) electrolyte solution, we have employed cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM) techniques to study the electrochemical behaviour of WSeCl₄. A pulsed electrodeposition technique was then used to deposit WSe₂ films, which possess a homogeneous composition across the whole electrode area. Characterization using scanning and transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy confirm the electrodeposited thin films to be WSe₂. As a proof-of-concept for future growth directly into 3D device architectures, we present the 2D anisotropic growth of WSe₂ thin films from the edge of a 100 nm thick TiN nanoband electrode across SiO₂ on microfabricated 3D structures, allowing the direct measurement of electrical characteristics. Through this work, we also demonstrate electrodeposition as an area-selective growth technique suitable for obtaining highly anisotropic WSe₂ thin films which are very promising for future electronic and optoelectronic applications.