HRTEM Microstructural Characterization of β-WO3 Thin Films Deposited by Reactive RF Magnetron Sputtering.

M.E. Botello-Zubiate,A. Faudoa-Arzate,A. Arteaga-Durán,J.A. Matutes-Aquino,P.R. Realyvazquez-Guevara,R.J. Saenz-Hernández

doi:10.3390/ma10020200

M.E. Botello-Zubiate, A. Faudoa-Arzate

Open Access

https://doi.org/10.3390/ma10020200

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Abstract

Though tungsten trioxide (WO3) in bulk, nanosphere, and thin film samples has been extensively studied, few studies have been dedicated to the crystallographic structure of WO3 thin films. In this work, the evolution from amorphous WO3 thin films to crystalline WO3 thin films is discussed. WO3 thin films were fabricated on silicon substrates (Si/SiO2) by RF reactive magnetron sputtering. Once a thin film was deposited, two successive annealing treatments were made: an initial annealing at 400 °C for 6 h was followed by a second annealing at 350 °C for 1 h. Film characterization was carried out by X-ray diffraction (XRD), high-resolution electron transmission microscopy (HRTEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) techniques. The β-WO3 final phase grew in form of columnar crystals and its growth plane was determined by HRTEM.

Highlights

Tungsten trioxide (WO3 ), either in bulk, thin films or as nanospheres, is widely studied for applications in catalysis [1], electrochromic devices [2], and gas sensing [3], among others
Bulk samples do not retain any of these phases (α- and β-WO3 ) when they are cooled to room temperature
In contrast to what happens to bulk WO3, all of the above phases (α- and β, γ- and δ-WO3 ) can be present in WO3 thin films at room temperature, depending on synthesis conditions, showing a diversity of morphologies, crystalline structures, and space groups [5]

Summary

Introduction

Tungsten trioxide (WO3 ), either in bulk, thin films or as nanospheres, is widely studied for applications in catalysis [1], electrochromic devices [2], and gas sensing [3], among others. For all these applications, the required physical properties are determined by the microstructure and by the present crystalline phases; there are very few studies on the microstructural and crystallographic characteristics of WO3 thin films. This work is focused on the study of the morphology of a reactive RF sputtered β-WO3 thin film and the effects of subsequent annealing on the orthorhombic crystal structure

Experimental

Results and Discussion

Thin films:

Conflicts