Optical and IR studies on (MoO3)1−x–(WO3)x mixed oxide thin films

Thin films of MoO3, WO3 and (MoO3)(1-x)-(WO3)(x) were deposited by a flash evaporation technique at a fixed oxygen partial pressure of 5x10(-4) mbar and at substrate temperatures of 300 and 500 K onto glass and p-Si (100) substrates. The prepared films were characterized by XRD, IR, UV VIS spectra. The XRD spectra reveals that the structure of (MoO3)(1-x)-(WO3)(x) films is amorphous. The IR spectra of the (MoO3)(1-x)-(WO3)(x) films for x=0.25, 0.5 and 1 were observed to be broad which also indicates the films were amorphous. The energy gaps of the mixed oxide films are in between 2.93 and 3.63 eV. The width of localized states is 0.62 eV (for x=0). The width of localized states E-e, increases with increasing WO3 concentration and is maximum at x=0.5. The electrical conductivity of the MoO3 films (x=0) deposited at 300 K is 1.39x10(-4) Omega(-1) cm(-1) and decreases to 2.3x10(-5) Omega(-1) cm(-1) with decreasing MoO3 concentration (x=1). The electrical conductivity of the films deposited at 500 K is 3.17x10(-4) Omega(-1) cm(-1) (x=0) and decreases to 2.5x10(-5) Omega(-1) cm(-1) with increasing WO3 concentration (x=1).