Structural and Morphological Characterization of Magnetron Sputtered Nanocrystalline Vanadium Oxide Films for Thermochromic Smart Surfaces

Abstract

Nanocrystalline vanadium oxide thin films have been deposited by reactive DC magnetron sputtering onto glass substrates under different processing conditions. Structural analysis and phase identification have been carried out by means of X-ray diffractometry (XRD). The surface morphologies of the different films have been examined by both scanning electron microscopy (SEM) and atomic force microscopy (AFM). The XRD results revealed single and multiple phase oxides such as VO2(B), VO2(M), V2O5, etc. with considerable differences concerning to surface morphologies, as observed by SEM and AFM. The effects the O2/Ar flow ratio, DC current, and working pressure on the phases formed and growth rates is discussed. Moreover, VO2(M) films exhibited different morphologies concerning to grain size and shape as well as dissimilar preference in crystal orientation, as a result of the processing conditions. The optical/thermochromic response of the VO2(M) specimens deposited under different growth rate conditions was evaluated by optical spectrophotometry and related to the respective structural characteristics.