Temperature dependent optical properties of c-axis oriented ZnO thin film were investigated using surface plasmon resonance (SPR) technique. SPR data for double layer (prism-Au-ZnO-air) and single layer (prism-Au-air) systems were taken over a temperature range (300–525 K). Dielectric constant at optical frequency and real part of refractive index of the ZnO film shows an increase with temperature. The bandgap of the oriented ZnO film was found to decrease with rise in temperature. The work indicates a promising application of the system as a temperature sensor and highlights an efficient scientific tool to study optical properties of thin film under varying ambient conditions.

The effects of annealing and gas composition on the refractive indices of zinc oxide films were studied in light of the structural properties. ZnO films (1μm) were deposited by rf magnetron sputtering in different oxygen:argon mixtures on glass and annealed at 380°C in air, at different times. Waveguide modes were excited in the films by prism coupling using a He-Ne laser. The estimated values of the extraordinary and ordinary refractive indices of the films, which were close to the corresponding bulk values (ne=2.006, no=1.990), initially decreased with annealing time and later increased before becoming constant with further annealing. The variation in refractive indices was explained on the basis of contribution from both packing density p and lattice constant c of the films. The initial decrease in refractive indices was attributed to the observed lattice contraction, and the latter increase was explained in terms of the increase in packing density (p) of the films on annealing. A relation is proposed to estimate the refractive indices of films, which have the lattice constant c different from the bulk value.

The surface-plasmon resonance (SPR) technique is used to study the growth rate and the nature of Ag(2)S films formed on a silver (Ag) film exposed to an atmosphere containing 50% H(2)S for different times. The thickness of the Ag(2)S layer formed, estimated from shifts in the experimental SPR curves, showed a saturation tendency after an initial linear increase. Theoretical analysis of the curves when Ag and Ag(2)S are treated as two uniform layers and Ag-Ag(2)S as a composite layer showed that radiation damping is mainly responsible for the increase of half-width and dip reflectance, indicating that the Ag(2)S film formed is rough and discontinuous.

No abstract

No abstract