Operando hall measurements on tin doped indium oxide thin films: A different approach to gain insight into the mechanism of interaction of oxygen or hydrogen at different temperatures

Abstract

Hall voltage measurement is a unique tool to quantify the charge carrier density ($n$) and charge carrier mobility (μ) in conducting/semiconducting materials. Understanding the interaction of gases with oxide surfaces plays a crucial role in applications such as sensing, catalysis, energy storage, etc. In particular, studies of Hall transverse voltage on tin in indium oxide (ITO) films from 300 K to 648 K indicated ionosorption of oxygen above 548 K. The interaction with hydrogen is found to be temperature-dependent, with a common effect of decreasing resistivity (ρ). At 598 K, $n$ increases due to the pumping back of oxygen-trapped electrons to the conduction band during interaction with H₂ from 3.5 × 10²⁰ cm^-3 (in air) to 6.1 × 10²⁰ cm^-3 (in 1250 ppm of H₂) whereas, at 473 K the increase in μ is more dominant from 5.4 cm²V^-1s^-1 (in air) to 24.7 cm²V^-1s^-1 (in 5000 ppm of H₂) over decrease in$n$. This study presents the temperature-dependent behavior of charge carrier characteristics during gas-surface interactions.