High Sensitivity Low-Temperature Hydrogen Sensors Based on SnO 2 /κ(ε)-Ga 2 O 3 :Sn Heterostructure.

The structural and gas-sensitive properties of n-N SnO₂/κ(ε)-Ga₂O₃:Sn heterostructures were investigated in detail for the first time. The κ(ε)-Ga₂O₃:Sn and SnO₂ films were grown by the halide vapor phase epitaxy and the high-frequency magnetron sputtering, respectively. The gas sensor response and speed of operation of the structures under H₂ exposure exceeded the corresponding values of single κ(ε)-Ga₂O₃:Sn and SnO₂ films within the temperature range of 25–175 °C. Meanwhile, the investigated heterostructures demonstrated a low response to CO, NH₃, and CH₄ gases and a high response to NO₂, even at low concentrations of 100 ppm. The current responses of the SnO₂/κ(ε)-Ga₂O₃:Sn structure to 10⁴ ppm of H₂ and 100 ppm of NO₂ were 30–47 arb. un. and 3.7 arb. un., correspondingly, at a temperature of 125 °C. The increase in the sensitivity of heterostructures at low temperatures is explained by a rise of the electron concentration and a change of a microrelief of the SnO₂ film surface when depositing on κ(ε)-Ga₂O₃:Sn. The SnO₂/κ(ε)-Ga₂O₃:Sn heterostructures, having high gas sensitivity over a wide operating temperature range, can find application in various fields. [ABSTRACT FROM AUTHOR]