Annealing effects on the optical and electrochemical properties of tantalum pentoxide films

Wei Ren,Ai-Ling Feng,Rui-Xia Miao,Guang-Dao Yang,Jun-Bo Xia,Yong-Gang Wang

doi:10.1007/s40145-021-0465-2

Abstract

Tantalum pentoxide (Ta2O5) has attracted intensive attention due to their excellent physicochemical properties. Ta2O5 films were synthesized via electron beam evaporation (EBE) and subsequently annealed at different temperatures ranging from 300 to 900 °C. X-ray diffraction (XRD) results show that amorphous Ta2O5 thin films form from 300 to 700 °C and then a phase transition to polycrystalline β-Ta2O5 films occurs since 900 °C. The surface morphology of the Ta2O5 films is uniform and smooth. The resulted Ta2O5 films exhibit excellent transmittance properties for wavelengths ranging from 300 to 1100 nm. The bandgap of the Ta2O5 films is broadened from 4.32 to 4.46 eV by annealing. The 900 °C polycrystalline film electrode has improved electrochemical stability, compared to the other amorphous counterparts.

Highlights

Ta2O5, which forms at either tetragonal (α-Ta2O5) or orthogonal (β-Ta2O5) crystalline phase, is one of the important transition-metal oxides with high refractive index (n = 2.02–2.16), high dielectric constant ( = 20–46), wide bandgap (4.0–4.5 eV), and wide transmission spectrum [1]
Using chemical vapor deposition (CVD), Devine et al [19] developed a new plasma-enhanced process to obtain high-quality amorphous Ta2O5 thin films, which were used as gate insulators to make p-channel MOS transistors
The other three curves do not exhibit Ta2O5 peak except for a broad hump at 27°–32°. The presence of this hump infers that the Ta2O5 films are amorphous in the temperature range of 300–700 °C

Summary

Introduction

Masse et al [26] studied Ta2O5 thin films at different annealing temperatures ranging from room temperature up to 900 °C and found mutual diffusion of oxygen, silicon, and Ta at high temperatures. He et al [27] studied the effects of oxygen pressure on film roughness and optical transmission of PLD-grown Ta2O5 films. EBE, a simple film-growth method, had been employed to deposit amorphous Ta2O5 films on quartz and Si substrates to produce optical coatings with uniform, smooth surfaces and a high film density [33,34,35]. Our purpose is to investigate the properties of Ta2O5 samples at different annealing temperatures, and the research work should bear the significance to improve the long-term stability of the photocatalyst/ electrocatalyst electrodes

Experimental

Results and discussion

Conclusions