Electrical properties of V_2O_5 thin films obtained by atomic layer deposition (ALD)

摘要

Dielectric and conductivity spectra of a V_2O_5 thin film were recorded in a broad frequency range 40-1.1 x 10~8 Hz at temperatures varying between 205 and 297 K.The V_2O_5 thin film (thickness 260 nm) was deposited on titanium substrate by atomic layer deposition (ALD).An annealing process at 500 deg C in air was required to obtain crystallized V_2O_5.All the data are presented in the form of complex resistivity diagrams which have been analyzed in relation to characterizations with scanning electron microscopy (SEM) and X-ray diffraction (XRD).These diagrams show the existence of relaxations due to interfacial polarization phenomena (grain boundary polarization) within the sample,which permits the determination of the de-conductivity of the grain (monocrystal).A dielectric relaxation is found,attributed to non-adiabatic small polaron hopping.The corresponding relaxation frequency is thermally activated with an activation energy of 0.14 eV.The experimental results enabled us to determine the drift mobility of the small polarons,i.e.mu_D= 1.84 x 10~(-2) cm~2 V~(-1) s~(-1) at room temperature.