Response kinetics of doped CuO/ZnO heterocontacts

In this work, the effects of doping on hydrogen sensitivity and sensor response of CuO/ZnO heterocontacts were examined. Both current-voltage and current-time measurements were utilized in hydrogen/air and hydrogen/nitrogen atmospheres at 400 degrees C. The addition of Ni to p-type CuO and Ga to n-type ZnO were observed to enhance the sensor properties. Through analysis of the time-dependent current data, it was shown that the sensor response of the heterocontact can be modeled via a two-site Langmuir adsorption model. The response times of the two sites were calculated using this model. While one of the sites showed a significant decrease in response time when the p-side was doped with Ni, the response time of the other site changed only slightly. The highest sensitivity was obtained by doping the n-side with Ga at the expense of the response rate. The fastest response times were achieved when both sides of the heterocontact were doped. This suggests that carrier density may play a significant role in the sensor response.