Effect of annealing on refractive indices of radio-frequency magnetron sputtered waveguiding zinc oxide films on glass

Abstract

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.

Structure, Morphology, and Optical Properties of the Compact, Vertically-Aligned ZnO Nanorod Thin Films by the Solution-Growth Technique

“…magnetron reactive sputtered ZnO film (a thickness of 1000 nm) fabricated under the sputtering conditions of a working pressure of 1.33×10 -2 m bar, a r.f. power of 500 W, Ar-O 2 ratio 40: 60, and the substrate temperature of room temperature (RT) by Mehan et al revealed that the refractive indexes (n at λ = 550 nm) were 1.980 (n eb : extra ordinary refractive index ) and 1.963 (n ob : ordinary refractive index), as well as packing densities were 0.986 and 0.978 (extra ordinary refractive index of bulk ZnO, n eb = 2.006, and ordinary refractive index of bulk ZnO, n ob = 1.990), respectively (Mehan et al, 2004). Although lots of parameters can influence the quality of sputtered ZnO films, such high refractive index and packing density may be the extreme values for the sputterred ZnO films.…”

Temperature dependent optical properties of (002) oriented ZnO thin film using surface plasmon resonance

“…21 The SPR curves of the double layer system were obtained at various temperatures from 300 to 525 K ͑Fig. 3͒.…”

Influence of Oxygen on Zinc Oxide Films Fabricated by Ion-Beam Sputter Deposition

“…The transmittances of ZnO-2 to -8 films deposited at O 2 < 1.0 × 10 −4 Torr are lower than 80% in visible region due to the heavier optical absorption of the suboxide film. The transmittances of ZnO-10 to -20 deposited at lower deposition rate at O 2 ≥ 1.0 × 10 −4 Torr are larger than 80% as the transparent films approach to stoichiometric [13,14]. However, the transmittances decrease sharply at absorption edges of about 350 nm wavelength.…”