Structure, DC and AC conductivity of oxazine thin films prepared by thermal evaporation technique

Thin films of oxazine (OXZ) were prepared using thermal evaporation technique under high vacuum. The thermogravimetric analysis (TGA/DSC) was investigated. Thin films of nano-crystalline OXZ were identified by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Temperature dependence of the DC electrical conductivity was investigated in the temperature range 300-425 K. Measurements revealed that the DC behavior of the films can be described by Mott's one-dimensional variable range hopping (VRH) model in the entire temperature range. The AC conductivity of the sample is found to be proportional to omega(s) The temperature dependence of the AC conductivity and the frequency exponent, s is reasonably well interpreted in terms of the correlated barrier-hopping CBH model. Frequency dependence of the capacitance in the frequency range 42 Hz-5 MHz indicates that the capacitance is strongly frequency dependent. The capacitance was determined to decrease with increasing frequency at low frequency and less rapidly at higher frequencies. This is quantitatively interpreted using an equivalent circuit model. (C) 2010 Elsevier B.V. All rights reserved.