Thermally Stimulated Currents in Nanocrystalline Titania

Abstract

A thorough study on the distribution of defect-related active energy levels has been performed on nanocrystalline TiO2. Films have been deposited on thick-alumina printed circuit boards equipped with electrical contacts, heater and temperature sensors, to carry out a detailed thermally stimulated currents analysis on a wide temperature range (5–630 K), in view to evidence contributions from shallow to deep energy levels within the gap. Data have been processed by numerically modelling electrical transport. The model considers both free and hopping contribution to conduction, a density of states characterized by an exponential tail of localized states below the conduction band and the convolution of standard Thermally Stimulated Currents (TSC) emissions with gaussian distributions to take into account the variability in energy due to local perturbations in the highly disordered network. Results show that in the low temperature range, up to 200 K, hopping within the exponential band tail represents the main contribution to electrical conduction. Above room temperature, electrical conduction is dominated by free carriers contribution and by emissions from deep energy levels, with a defect density ranging within 1014–1018 cm−3, associated with physio- and chemi-sorbed water vapour, OH groups and to oxygen vacancies.

Defective States in Micro-Crystalline CsPbBr3 and Their Role on Photoconductivity

“…CsPbBr 3 films were deposited by drop-casting directly on an alumina printed circuit board (PCB) especially designed for electrical tests of thin semiconductor films at a wide temperature range [22]. The PCBs have two/four parallel gold contacts, 7 mm long, spaced at 0.8 mm, as well as integrated Pt temperature sensors and a heater on the back side.…”

Degenerated TiO2 Semiconductor Modified with Ni and Zn as Efficient Photocatalysts for the Water Splitting Reaction

“…[69] An important assumption would be that both oxides have oxygen vacancies and therefore are n-type doped. These oxygen vacancies produce a donor level located at about 1 eV below the bottom of the conduction band E C ; [68,70] therefore, the energy difference between E C and the Fermi level E F is about 0.5 eV. The separated energy diagrams are represented in Figure 6a.…”

ZnO- and TiO2-Based Nanostructures

“…The electrical properties are also analyzed: the memristive response of TiO 2 nanoparticle is investigated by Schmidt et al [ 20 ] while Bruzzi and coworkers [ 21 ] report the thermally stimulated current in nanocrystalline titania.…”