Non-parabolic intergranular barriers in tin oxide and gas sensing

Abstract

Chemoresistive properties of crystalline solids strongly depend on the concentration of stoichiometric defects. In the case of tin oxide, oxygen vacancies are a case in point of such kind of defects. We address the problem of band bending and Schottky barrier formation in tin oxide. We approached the problem of charged native defects, oxygen vacancies, in a metal oxide in equilibrium with an oxygen containing ambient under three equivalent points of view. We focused on the non-parabolic barriers character that form at intergrains. Implications in electrical responses to oxygen concentration variations will be discussed

Sensitivity of metal oxide gas sensors to non-parabolic intergranular barriers

“…The crucial point with Eq. ( 1) is that the equilibrium donor concentration strongly depends on band bending, as discussed in detail in Ref [16]. This issue, within the field of sensors, was raised by Lantto and co-workers long time ago [9].…”

Overview of Gas Sensors Focusing on Chemoresistive Ones for Cancer Detection

“…This potential barrier is typically parabolic (Figure 11); however, the observed changes in resistance cannot be accounted for solely by thermionic emission because there is also a tunneling contribution [62][63][64]. Therefore, the conductance changes depend not only on the barrier height but also on its width, as tunneling depends on both, and, in general, on the entire barrier shape, which changes as oxygen diffuses into the grain [65]. The changes of 𝐺 are detected by an acquisition circuit comprising an operational amplifier in the inverting configuration (Figure 12) in which the sensor is connected to the negative entrance of the amplifier and is polarized by 𝑉 𝑖𝑛 .…”