Nickel oxide thin films synthesized by reactive pulsed laser deposition:: characterization and application to hydrogen sensing

Transparent nickel oxide thin films were grown by reactive pulsed laser deposition. An ArF* (lambda = 193 nm, tau = 12 ns) excimer laser source was used to ablate the Ni targets in a controlled pressure of ambient oxygen. The substrates were either kept at room temperature or heated to a selected temperature within the 200-400 degrees C range. Post-deposition heat treatment, which was applied to further promote crystallization and overcome any oxygen deficiency, yielded transparent thin films. The surface morphology and crystalline status of the synthesized thin structures were analyzed in correlation with their optical properties. A significant response to several concentrations of hydrogen was demonstrated when heating the nickel oxide films at 185 degrees C.