The Effect of Different Metal Electrodes on the Performance of ZnO/p-Si/Al Hetero-Structure for Hydrogen Detection

Nanocrystalline n-ZnO was prepared by the simple low-cost sol-gel method and was deposited on crystalline Si substrate. Sensors with Al/n-ZnO/p-Si/Al, Ni/n-ZnO/p-Si/Al, Au/n-ZnO/p-Si/Al, and Pd/n-ZnO/p-Si/Al device structures were exposed to different hydrogen concentrations (0.01%, 0.05%, 0.1%, 0.5%, and 1.0%) at the optimum biasing voltage and temperature. The effect of gas response was investigated using nitrogen as the carrier gas. Pd/n-ZnO/p-Si/Al sensor gives the best results (response 37% and response time 174 s) due to the high absorption and dissociation power of Pd toward hydrogen. A possible gas sensing mechanism was suggested with a qualitative energy band diagram.