Several applications of semiconductors depend critically on their doping level, in fact, chemiresistive properties of crystalline metal-oxides strongly depend on the concentration of stoichiometric defects. In the case of tin oxide, oxygen vacancies are a case in point of such defects. We address the problem of band bending and Schottky barrier formation in tin oxide and consider the possibility of oxygen in- and out-diffusion in a field-assisted and thermionic emission conduction model. The asymmetry induced in the surface barrier by external bias will be taken into account to explain some experimental evidences: the model allowed us to explain the different behavior of conductance in gas of two sets of sensors with grains having two well distinct characteristic radii (R= w and R>w). We then approached the problem of oxygen vacancies distribution in a metal oxide in equilibrium with an ambient containing oxygen, under two equivalent points of view. We focused on the non-parabolic barriers character that results from this approach. Implications in electrical responses to oxygen concentration variations will be discussed.
Transport mechanisms in polycrystalline tin oxide: field-assisted and thermionic emission, intra-grain oxygen diffusion and non parabolic barriers
MALAGU', Cesare
2012
Abstract
Several applications of semiconductors depend critically on their doping level, in fact, chemiresistive properties of crystalline metal-oxides strongly depend on the concentration of stoichiometric defects. In the case of tin oxide, oxygen vacancies are a case in point of such defects. We address the problem of band bending and Schottky barrier formation in tin oxide and consider the possibility of oxygen in- and out-diffusion in a field-assisted and thermionic emission conduction model. The asymmetry induced in the surface barrier by external bias will be taken into account to explain some experimental evidences: the model allowed us to explain the different behavior of conductance in gas of two sets of sensors with grains having two well distinct characteristic radii (R= w and R>w). We then approached the problem of oxygen vacancies distribution in a metal oxide in equilibrium with an ambient containing oxygen, under two equivalent points of view. We focused on the non-parabolic barriers character that results from this approach. Implications in electrical responses to oxygen concentration variations will be discussed.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
