Non-vacuum Preparation of wse2 Thin Films via the Selenization of Hydrated Tungsten Oxide Prepared using Chemical Solution Methods

Authors

Christopher L. Exstrom, University of Nebraska at Kearney,Follow
Scott A. Darveau, University of Nebraska at KearneyFollow
Megan E. Falconer, University of Nebraska at Kearney
Jessica R. Blum, University of Nebraska at Kearney
Whitney M. Colling, University of Nebraska at Kearney
Natale J. Ianno, University of Nebraska - LincolnFollow

ORCID IDs

https://orcid.org/0000-0002-2423-0463 Natale Ianno

Document Type

Article

Date of this Version

2018

Citation

MRS Advances, Volume 3, Issue 56 (Energy Materials and Technologies),2018 , pp. 3281-3286

DOI: 10.1557/adv.2018.451

Comments

© 2018 Materials Research Societ. Used by permission.

Abstract

It is known that tungsten oxide may be reacted with selenium sources to form WSe₂ but literature reports include processing steps that involve high temperatures, reducing atmospheres, and/or oxidative pre-treatments of tungsten oxide. In this work, we report a non-vacuum process for the fabrication of compositionally high quality WSe₂ thin films via the selenization of tungsten oxide under milder conditions. Tungsten source materials were various hydrated WO₃ and WO_2.9 compounds that were prepared using chemical solution techniques. Resulting films were selenized using a two-stage heating profile (250 °C for 15 minutes and 550 °C for 30 minutes) under a static argon atmosphere. Effects of the starting tungsten oxide phase on WSe₂ formation after single and double selenization cycles were investigated using Raman spectroscopy and X-ray diffraction (XRD). After two selenization cycles, hydrated WO₃ was converted to (002)-oriented WSe₂ that exhibits well-resolved peaks for E¹_2g and A_1g phonon modes. Only a single selenization cycle was required to convert amorphous WO_2.9 to WSe₂. All selenizations in this work were achieved in non-reducing atmospheres and at lower temperatures and shorter times than any non-laser-assisted processes reported for WO₃-to-WSe₂ conversions.