High quality VO2 thin films synthesized from V2O5 powder for sensitive near-infrared detection

Vapor transport method has been successfully used to synthesize high quality VO2 thin films on SiO2/Si substrate using V2O5 as a precursor in an inert-gas environment. The morphological and structural evolutions of the intermediate phases during the nucleation and growth processes were investigated by SEM and Raman spectroscopy, respectively. The results showed that the conversion of V2O5 powder to VO2 thin films was dominated by a melting-evaporation-nucleation-growth mechanism. Further characterization results demonstrated that the high quality crystals of monoclinic VO2 thin films exhibit a sharp resistance change up to 4 orders of magnitude. In addition, the VO2 thin films exhibited good near-infrared response, high stability, and reproducibility under ambient conditions, which should be promising for sensitive near-infrared detection. Our work not only provided a simple and direct approach to synthesize high quality VO2 thin films with distinct phase transition properties but also demonstrated the possible infrared sensing application in the future.

Microfabrication of VO2 Thin Films via a Photosensitive Sol-Gel Method

VO2 films are widely used in photoelectric switches, smart glasses, storage media, and terahertz communications. In these applications, microfabrication technology is a very important process for producing microdevices or even improving film properties. In this paper, a novel photoetching microfabrication method is proposed for VO2 thin films. First, a VO2 precursor sol with ultraviolet photosensitivity was prepared using vanadyl acetylacetonate as the raw material and anhydrous methanol as the solvent. The dip-coated VO2 gel film can be directly subjected to photolithography processing without coating additional photoresist by using the photosensitive sol. A fine pattern on the VO2 film with good phase-transition performance can be obtained after annealing in a nitrogen atmosphere at 550 °C for 1 h. This method can be used to prepare grating, microarray, and various other fine patterns with the remarkable advantages of a low cost and simplified process, and the as-obtained material performances are unaffected using the method. It is a potential alternative method for optics, electronics, and magnetics devices based on VO2 thin films.