Electrical mechanism of thin films TeO2-V2O5-NiO prepared by vacuum evaporation method with MIM structure

In this experimental work bulk glasses of 40TeO2-(60-X)V2O5-XNiO compositions with 0 < X < 30 (in mol %) have been prepared using the press melt quenching method. Thin films of bulk samples with X= 0,10,30 (in mol %) have been prepared using the vacuum evaporation method with electrically heated evaporation sources for electrical study. Thin films with X=0,5,10,20,30 (in mol %) have been prepared using the electron beam evaporation technique for optical study. The DC conductivity of thin films, 40TeO2-60V2O5, 40TeO2-50V2O5-10NiO and 40TeO2-30V2O5-30NiO in the temperature range 300-423 K were measured. From the conductivity-temperature relation it was found that the small polaron hopping model is applicable. The values of activation energy was increased from 0.035 to 0.042 eV with increasing NiO concentration. The DC conductivities at 393 K for present films were determined to be in the range 7.5 * 10-11 S/cm to 5.26 * 10-9 S/cm, indicating that the conductivity decreases with increasing NiO concentration. Because NiO is not a glass-network former, the Ni ions are isolated in the glass-network, which causes obstruction for hopping of electrons due to the lack of oxygen bonds. Typical current-voltage curves of samples show that at low electric fields, the I-V characteristics of the samples has a linear shape, while at high electric fields (> 105V/cm) thin films show non-linear behavior (non-ohmic conduction). Behavior of I-V characteristics of the samples was studied at three different temperatures of 300,348 and 423 K. At high temperatures, the threshold field of non-ohmic behavior is reduced due to the increase of conductivity with an increase in temperature; therefore, we can state that the conduction mechanism is due to thermal excitation with the effect of electric field.