Robust Conductivity Changes in ZnO and MgZnO Nanoparticle Films from Annealing in Hydrogen

We report changes observed in the I-V characteristics of ZnO and MgZnO nanoparticle thin films after annealing in H$_{2}$ 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 $\mu $m diameter gold wires laid parallel to each other on the nanoparticle film to measure the current passing through the film. When exposed to H$_{2}$ 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 H$_{2}$ below 140\r{ }C also resulted in no significant change in the current. When annealed above 140\r{ }C, we observed an increase of about a factor of ten that was semi-permanent. The origin of the change in I-V characteristics of ZnO and MgZnO nanoparticles when annealed in H$_{2}$ will be discussed.