Robust conductivity changes in ZnO and MgZnO nanoparticle films from annealing in hydrogen ambient

We report changes observed in the I-V characteristics of ZnO and MgZnO nanoparticle thin films after annealing in H₂ at sufficiently high temperatures. The nanoparticles were grown on insulating silicon substrates and had an average diameter of 30 nm. The devices were of a two terminal design, where the terminals consisted of two 25 μm diameter gold wires laid parallel to each other on the nanoparticle film to measure the current passing through the film. When exposed to H₂ gas at room temperature, no significant changes in the current-voltage behavior of the nanoparticles were observed relative to measurements done in vacuum. Annealing in H₂ below 100 °C also resulted in no significant change in the current. When annealed above 100 °C, we observed an increase of about a factor of twenty that was semi-permanent. The origin of the change in I-V characteristics of ZnO and MgZnO nanoparticles when annealed in H₂ will be discussed.