Influence of pulsed laser deposition (PLD) parameters on the H2 sensing properties of zinc oxide thin films

Thin films of n-type ZnO were produced by a novel two-target, two-pulsed laser deposition technique. This method allows on-line control of the film properties by just changing the laser parameters. A number of deposition parameters, as well as the dopants (Al, Au) and the substrate type (Si, SiO2, glass), were changed. The sensing properties of the films were tested upon exposure to a H2 flow in air ambient at working temperatures between 150 and 210 ∘C. Undoped ZnO thin films, deposited on SiO2 substrates at 200 ∘C, in ambient O2 at 20 Pa and with a laser fluence of 9.6 J/cm3, exhibited a maximum sensitivity (ΔR/R0) higher than 97% and a response time lower than 3 min at the working temperature 180 ∘C. Decrease of the working temperature to 150 ∘C was achieved by means of surface sensitization of films after deposition of Au nanoclusters on the surface of the above-mentioned ZnO thin films.