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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 μm 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 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 H 2 will be discussed.Index Terms -ZnO and MgZnO nanoparticles, hydrogen ambient, nanoparticle conductivity.

We report apparent robust doping of ZnO and Mg x Zn 1-x O (x ~20%) nanoparticle films by annealing in hydrogen gas. The annealing was done at sequentially higher temperatures from about 20 ˚C to 140 ˚C. The effect of the annealing was determined by comparing current-voltage measurements of the samples at room-temperature and in vacuum after each annealing cycle. The nanoparticles were grown using an aqueous solution and heating process that created thinfilms of ZnO or MgZnO nanoparticles with diameters of about 30 nm. When exposed to hydrogen gas at room-temperature or after annealing at temperatures up to about 100 ˚C, no measureable changes to the room-temperature vacuum conductivity of the films was observed. However, when the samples were annealed at temperatures above 100 ˚C, an appreciable robust increase in the room-temperature conductance in vacuum occurred. Annealing at the maximum temperature (~135-140 ˚C) resulted in about a factor of about twenty increase in the conductivity. Furthermore, the ratio of the conductance of the ZnO and MgZnO nanoparticle films while being annealed to their conductance at room-temperature were found to increase and then decrease for increasing annealing temperatures. Maximum changes of about five-fold and seven-fold for the MgZnO and ZnO samples, respectively, were found to occur at temperatures just below the annealing temperature threshold for the onset of the robust hydrogen gas doping. Comparisons of these results to other work on bulk ZnO and MgZnO films and reasons for this behavior will be discussed.