Impedance spectroscopy of semiconducting films on tin electrodes

Impedance spectroscopy and cyclic voltammetry measurements were used to exa mine solid-slate properties of thin anodic films on tin. The impedance of t in \ n-type SnO2 \ electrolyte system was studied as a function of applied potential and frequency. In the absence of illumination at room temperature . the impedance spectroscopy technique when used in conjunction with an app lied bias potential can be a powerful tool for identification of deep-level states. An electrical equivalent circuit corresponding to the Voight model , which describes the behavior of the passive film on tin more adequately t han the models for 'classical' semiconductors, is presented. The change in the Mott-Schottky plot was interpreted in terms of partial ionization of de ep-level states. The resistive component of the impedance measured at low f requencies was much more sensitive to deep-level states than the capacitive one and was used to determine their distribution in the bulk of SnO2. Both flat-band potential and donor concentration were estimated from the space charge capacitance at high frequencies. The dielectric properties of the ox ide film were discussed and several parameters were determined in terms of a parallel plate capacitor and in accordance with the high-field growth law . (C) 1999 Elsevier Science Ltd. All rights reserved.