Articles written in Bulletin of Materials Science

    • Synthesis and properties of zirconia thin films

      M H Suhail M Ghanashyam Krishna G Mohan Rao S Mohan

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      Thin films of zirconia have been synthesized using reactive DC magnetron sputtering. It has been found that films with good optical constants, high refractive index (1·9 at 600 nm) and low extinction coefficient can be prepared at ambient temperatures. The optical constants and band gap and hence the composition are dependent on the deposition parameters such as target power, rate of deposition and oxygen background pressure. Thermal annealing of the films revealed that the films showed optical and crystalline inhomogeneity and also large variations in optical constants.

    • Effect of pre-annealing on the structural evolution and optical response of Ag films exposed to iodine vapours


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      Ag thin films of 5nm thickness were deposited on glass substrates by thermal evaporation. The films were divided into two sets, out of which, one set was not annealed and the other set was subjected to pre-annealing at 300$^{\circ}$C for2 h in air. The un-annealed and pre-annealed films were exposed to iodine vapours at room temperature for the durations from 5min to 10 h. The un-annealed films were crystallized into the $\beta$ phase of AgI after exposure for 5 h. In contrast, for the pre-annealed films, crystallization into the $\beta$ phase occurred within the first 5 min. Both sets of films, however, exhibit astrong preferential c-axis orientation in the $\beta$-AgI phase. Optical absorption studies reveal that the un-annealed films exhibit a localized surface plasmon resonance (LSPR) with a peak at 545 nm and a long wavelength shoulder at 620 nm, which shifts to 516nm after iodization for a few minutes. This peak position does not change with further iodization. The LSPR for the pre-annealed films has a single peak at 538 nm. After iodization for a few minutes, this peak shifts to 525 nm. Iodization for 3 h results in a further blue-shift of this resonance to 475 nm. The photoluminescence spectrum reveals two peaks, oneat 368 nm and the other at 712 nm. The first one is assigned to the excitons of AgI, whereas the long wavelength peak is attributed to the presence of disorder in the films. The reasons for the difference in behaviour of the un-annealed andpre-annealed films are discussed.

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