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The Influence of Thermal Treatment on the Electronic Properties of a-Nb2O5

The effect of thermal treatments for 1h at 250{degree sign}C in air or under vacuum on the electronic structure of thick amorphous anodic niobia was characterized by electrochemical impedance, differential admittance (DA) and photocurrent spectroscopy (PCS). The analysis of anodized niobia has revealed that it behaves as a pure dielectric. The thermal treatment in air increases the value of the differential capacitance of the niobia sample. The effect is stronger when the thermal treatment is carried out in vacuum and can be cancelled out by reanodizing the oxide to the initial formation potential. In the case of thermally vacuum-treated sample, a behavior typical of semiconducting amorphou…

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Dynamic response of thin-film semiconductors to AC voltage perturbations

A theoretical treatment of a Schottky barrier dynamic response is developed on the basis of a general model of a semiconductor with thickness comparable in length to the space charge region width. It is shown that, when the space charge region approaches the metal/semiconductor interface, the electric field at this interface, induced by the charge accumulated on the metal, becomes significant with respect to the electric field induced by the charge accumulated on the semiconductor. Under this condition, the total capacitance of the Schottky barrier becomes independent of the polarization potential and tends to the value ε/L, like in a pure dielectric insulator. The term thin film is intende…

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Physicochemical Characterization of Passive Films and Corrosion Layers by Differential Admittance and Photocurrent Spectroscopy

Two different electrochemical techniques, differential admittance and photocurrent spectroscopy, for the characterization of electronic and solid state properties of passive films and corrosion layers are described and critically evaluated. In order to get information on the electronic properties of passive film and corrosion layers as well as the necessary information to locate the characteristic energy levels of the passive film/electrolyte junction like: flat band potential (Ufb), conduction band edge (EC) or valence band edge (EV), a wide use of Mott-Schottky plots is usually reported in corrosion science and passivity studies. It has been shown, in several papers, that the use of simpl…

Characterization of Thin Passive Film-Electrolyte Junctions. The Amorphous Semiconductor (a-SC) Schottky Barrier Approach.

A detailed study of the electronic properties of thin (< 20 nm) anodic TiO2 potentiostatically grown on titanium in two different solutions is presented. The results show that the nature of the anodizing solution affects the electronic properties of the anodic film and in particular the density of electronic state (DOS) distribution. Different DOS were derived from the experimental data analyzed according to the theory of amorphous semiconductor (a-SC) Schottky barrier. It is shown that the usual non-linear and frequency dependent Mott-Schottky plots are in agreement with expected theoretical behaviour of a-SC Schottky barrier. It is shown the importance of the DOS distribution in determini…