Optical absorption behaviour of vanadium pentoxide thin films

Abstract

Thin ®lms of vanadium pentoxide have been prepared by the electron beam evaporation technique over a wide range of substrate temperatures. Spectrophotometric investigations have been made on these ®lms in the wavelength range 350±1500 nm to determine the nature of the optically induced transition and the optical band gap. A better ®t for the direct forbidden transition than for the indirect allowed transition is observed in all the ®lms. The optical band gap is found to decrease with increasing substrate temperature and the subsequent appearance of a broadband absorption at about 1000 nm is attributed to the oxygen vacancies in the ®lms. The eect of heat treatment in vacuum and oxygen ambient on the optical properties of these ®lms is also reported.

Tunable thermochromic properties of V 2 O 5 coatings

“…Controlled oxidation of as-grown films to V 2 O 5 is accepted to yield films with various oxygen deficiencies [45,46]. These oxygen deficiencies are assumed to be responsible for the wide range of reported optical band gaps [47] and perceived colours [35].…”