Oxygen vacancies in proximity to surfaces and heterointerfaces in oxide thin film heterostructures have major effects on properties, resulting, for example, in emergent conduction behaviour, large changes in metal-insulator transition temperatures or enhanced catalytic activity. Here we report the discovery of a means of reversibly controlling the oxygen vacancy concentration and distribution in oxide heterostructures consisting of electronically conducting In2O3 films grown on ionically conducting Y2O3-stabilized ZrO2 substrates. Oxygen ion redistribution across the heterointerface is induced using an applied electric field oriented in the plane of the interface, resulting in controlled oxygen vacancy (and hence electron) doping of the film and possible orders-of-magnitude enhancement of the film's electrical conduction. The reversible modified behaviour is dependent on interface properties and is attained without cation doping or changes in the gas environment.

Interfacial control of oxygen vacancy doping and electrical conduction in thin film oxide heterostructures.

Semiconducting In2O3 gas sensors have been fabricated by two different deposition techniques, i.e., spin-coating and screen-printing. In both cases the same starting material – sol-gel-prepared cubic In2O3 – was used for the deposition in order to ensure a better comparability of the different sensing layers. The morphology of the layers has been characterized using scanning electron microscopy (SEM) technique. The layers deposited by different methods show similar grain size and porosity. Furthermore, Dc electrical tests have been performed to analyze the sensing properties of the different gas sensors. Reducing gases (CO and propanal) as well as oxidizing gases (NO2 and ozone) were used as test gases in the background of dry and humidified synthetic air. All measurements were performed at several temperatures. It was found that the spin-coated and screen-printed layers show different sensing properties, i.e., screen-printed sensors showed higher sensor signals than spin-coated sensors for CO, propanal, ...

Properties of Indium Oxide Semiconducting Sensors Deposited by Different Techniques

In situ Hall effect and conductivity measurements of ITO thin films

Porous In2O3 microstructures: Hydrothermal synthesis and enhanced Cl2 sensing performance

A review of the transport properties of molten oxide membranes (MOMs) is given. The MOMs are a new type of mixed-conducting membranes for oxygen separation from air. The rapidly expanding field of ion transport membranes is driven by a growing number of potential applications (fuel cells, membrane reactors, oxygen separators, sensors, etc.). Special attention is paid to the oxygen ion transport in MOM. The oxygen permeation kinetics and thermodynamics of MOM are considered. A dynamic polymer chain model for oxygen ion transport in molten oxides is analyzed. Prospects of MOM for oxygen technology are discussed.

Electrical and mass transport processes in molten oxide membranes

This paper reports electrical properties of In2O3 thin film (100 nm) at elevated temperatures (667–1118 K) and under controlled oxygen activity. The present study, based on the measurements of electrical conductivity (EC) using the method proposed by van der Pauw, includes the following determinations: Dynamics of EC changes during gas/solid equilibration of the O2/In2O3 system; The dependence of EC on oxygen partial pressure dependence; The dependence of EC on temperature.

Electrical conductivity of indium sesquioxide thin film

This paper reports electrical properties of In2O3 thin film (100 nm) at elevated temperatures (667-1118 K) and under controlled oxygen activity. The present study, based on the measurements of electrical conductivity (EC) using the method proposed by van der Pauw, includes the following determinations: Dynamics of EC changes during gas/solid equilibration of the O2/In2O3 system; The dependence of EC on oxygen partial pressure dependence; The dependence of EC on temperature.

This paper reports surface electrical properties of thin film of indium sesquioxide, In2O3, during oxidation and reduction at elevated temperatures (298 K and 873 K). The studies involved monitoring of surface potential during oxidation and reduction experiments using work function measurements. The obtained experimental data are considered in terms of the effect of temperature on reactivity between oxygen and In2O3, involving chemisorption and oxygen incorporation. The reactivity in the range 298 – 773 K is limited to chemisorption resulting in the formation of surface dipoles exhibiting positive surface charge. Oxidation at 873 K results in slow oxygen incorporation.

W. Wlodarski

Papers

Electrical conductivity of indium sesquioxide thin film

Electrical conductivity of indium sesquioxide thin film

Work function of indium sesquioxide thin film