EFFECT OF THICKNESS ON THE OPTICAL-ABSORPTION EDGE OF SPUTTERED VANADIUM-OXIDE FILMS

A study of the optical absorption edge of de magnetron sputtered vanad ium oxide films is reported. It is shown that the absorption edge is s trongly dependent on the thickness of the films. From the spectral tra nsmittance characteristics and optical absorption edge behaviour it is demonstrated that there is a critical thickness (250 nm) above which the films become completely stoichiometric V2O5. At thickness greater than 250 nm the absorption edge is 2.24 eV corresponding to stoichiome tric V2O5 and below that the values range between 2.4 and 2.5 eV indic ating the possible existence of non-stoichiometry in thinner films. Th e most significant result of the present study is to show that thickne ss of the films in conjunction with oxygen partial pressure can be use d to modulate optical band gap of vanadium oxide films. (C) 1997 Elsev ier Science S.A.