Correlation of optical energy gap with the nearest neighbour short range order in amorphous V2O5 films

The optical and structural properties of well characterized vacuum-evaporated amorphous V2O5 films were studied in the thickness range 5-500 nm. The structural analyses show that V-O, O-O and V-V nearest neighbour distances defining the short range order vary nonlinearly with film thickness. The optical absorption shows thickness-dependent energy gap (E-g) and the nonlinear behaviour of thickness-dependent E-g is similar to that of nearest neighbour distance with film thickness. The E-g correlates linearly very well with all the three nearest neighbour distances. The variation of E-g with film thickness is attributed to the residual stress in the film which causes the changes in short range order. The change in E-g corresponding to the change in V-O distance was found to be 35 eV nm(-1). This change is almost three times of that with V-V distance.