AC conduction in amorphous thin films of SnO2

• Published in: Journal of materials science 2008-09, Vol.43 (18), p.6049-6056
• Main Authors: Anwar, M., Ghauri, I. M., Siddiqi, S. A.
• Format: Article
• Language: English
• Subjects: Alternating current; Aluminum; Amorphous semiconductors; glasses; Annealing; Applied sciences; Building materials. Ceramics. Glasses; Capacitance; Characterization and Evaluation of Materials; Chemical industry and chemicals; Classical Mechanics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conduction cooling; Conduction heating; Crystallography and Scattering Methods; Electrical measurement; Electrical properties; Electrical properties of specific thin films; Electrical resistivity; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Film thickness; Glasses; High temperature; Hopping conduction; Materials Science; Oxidation; Oxygen; Physics; Polymer Sciences; Solid Mechanics; Space charge; Stoichiometry; Structure, analysis, properties; Substrates; Thickness measurement; Thin films; Tin dioxide; Vacancies; Valence
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-008-2959-5

Alternating current (a.c.) electrical properties of thermally evaporated amorphous thin films of SnO 2 sandwiched between aluminium electrodes have been investigated for temperature during electrical measurements, film thickness, substrate temperature and post-deposition annealing. The a.c. conductivity, σ(ω), is found to vary with frequency according to the relation σ(ω) ∝ ω s , indicating a hopping process at low temperature. The conduction is explained by single polaron hopping process as proposed by Elliott. The increase in electrical conductivity with increase in temperature during electrical measurements is ascribed to the increase in the formation and high mobility of doubly ionized oxygen vacancies. The increase in conductivity with increase in film thickness is caused by the increase in interstitial tin, oxygen vacancies and defects produced due to deviation from stoichiometry. The increase in conductivity with increase in substrate and annealing temperature may be due to the formation of singly or doubly ionized oxygen vacancies and tin species of lower oxidation state. Measurements of capacitance C as a function of frequency and temperature show a decrease in C with increasing frequency and increase in C with increasing temperature. The increase in capacitance in the high-temperature low-frequency region is probably due to space charge polarization induced by the increasing number of free carriers as a result of increasing temperature.