CuO thin films for the detection of H₂S doses: Investigation and application

Abstract

We present a new concept for the detection of hydrogen sulfide (H 2 S) doses based on percolation effects in semiconducting (p‐type) copper (II) oxide (CuO) thin films. Under H 2 S exposure at 180 °C CuO undergoes a chemical reaction to metallic conducting copper (II) sulfide (CuS). Reaching a certain dose of H 2 S (concentration × exposure time) the conductance increases rapidly by two orders of magnitude which is attributed to the formation of CuS percolation paths. This study focuses on the reproducibility of this effect as well as on theoretical modeling of the assumed underlying percolation mechanism. Analysis of conductance data reveals a behavior that is qualitatively very similar to standard scaling theory, but with a lower conductance exponent of µ ≈ 0.85 (instead of 1.3 for 2D systems). The deviation can be explained by a superimposing diffusion process and by deviations of the experimental systems from standard percolation systems. Nevertheless, the CuO thin films exhibit intrinsic structure controlled thresholds for H 2 S doses, which allows the utilization as H 2 S dosimeter. Conductance behavior of a CuO thin film exposed to 20 ppm H 2 S at 180 °C. The percolation threshold p c is reached 1054 s after start of the measurement.