Synthesis and Characterization of Highly Crystalline Vertically Aligned WSe2 Nanosheets

Ayrton Sierra-Castillo,J.-F Colomer,Carla Bittencourt,Selene Acosta,Emile Haye

doi:10.3390/app10030874

Abstract

Here, we report on the synthesis of tungsten diselenide (WSe2) nanosheets using an atmospheric pressure chemical vapor deposition technique via the rapid selenization of thin tungsten films. The morphology and the structure, as well as the optical properties, of the so-produced material have been studied using electron microscopies, X-ray photoelectron spectroscopy, photoluminescence, UV–visible and Raman spectroscopies, and X-ray diffraction. These studies confirmed the high crystallinity, quality, purity, and orientation of the WSe2 nanosheets, in addition to the unexpected presence of mixed phases, instead of only the most thermodynamically stable 2H phase. The synthesized material might be useful for applications such as gas sensing or for hydrogen evolution reaction catalysis.

Highlights

Tungsten diselenide (WSe2 ) belongs to the transition-metal dichalcogenides (TMDs) family.The chemical formula of TMDs is MX2, where M is a transition metal (Mo, W, Nb, Ta, etc.) and X is a chalcogenide (S, Se, etc.)
Bulk WSe2 has attracted increasing attention because of its interesting properties, exemplified by its ultralow thermal conductivity at room temperature (0.05 W·m−1 ·K−1 ) when considering disordered crystals [3]. This bulk material has been reported to be efficient in different applications, such as catalysts for hydrogen evolution reactions [4,5], or in photovoltaic devices [6]
We report here on a simple growth strategy using the atmospheric pressure chemical vapor deposition (APCVD) technique to obtain vertically-aligned WSe2 nanosheets by rapid selenization

Summary

Introduction

Tungsten diselenide (WSe2 ) belongs to the transition-metal dichalcogenides (TMDs) family.The chemical formula of TMDs is MX2 , where M is a transition metal (Mo, W, Nb, Ta, etc.) and X is a chalcogenide (S, Se, etc.). The MX2 compounds form layers composed of three atomic planes, namely: one metal atom between two chalcogenide atoms, covalently bonded, and the layers are linked between them by van der Waals forces [1] This is the case of the material of interest, WSe2 [2]. Bulk WSe2 has attracted increasing attention because of its interesting properties, exemplified by its ultralow thermal conductivity at room temperature (0.05 W·m−1 ·K−1 ) when considering disordered crystals [3] This bulk material has been reported to be efficient in different applications, such as catalysts for hydrogen evolution reactions [4,5], or in photovoltaic devices [6]. Monolayer WSe2 possesses a small band-gap (smaller than monolayer MoS2 ), and shows an ambipolar transport phenomenon [8]

Methods

Results

Conclusion