Optical waveguiding in amorphous tellurium oxide thin films

Properties of crystalline γ-TeO2 thin film

“…1. The vibrational spectra of as-deposited TeO 2 films in the wave number region of 400-1000 cm À1 show a strong broad absorption band at about 630 cm À1 , which was found to be well in the range reported earlier for TeO 2 films and bulk samples confirming the formation of Te-O bond [18][19][20]. The post-deposition annealing of as-deposited TeO 2 thin film at 100, 300, and 400 1C for 1 h showed significant changes in the shape, position, and intensity of the absorption band.…”

“…The accuracy of the absorbance values in the wavelength region of strong absorption is better than 2%. The band gap was observed to be direct type in all the samples and is in agreement with observation of other workers for TeO 2 thin film [18,19]. For direct electronic transition, extrapolation of the straight line region of the (ahv) 2 vs. hv plot to a ¼ 0 gives the band gap value [21].…”

“…4 shows the variation of estimated value of band gap of TeO 2 thin film as a function of annealing temperature. The estimated value of the band gap (eV) for as-deposited TeO 2 thin film is found to be higher than the reported value for single crystals (3.5 eV) [18] and is attributed to the amorphous nature of as-grown film. The value of band gap in general is reported to be higher for the structurally disordered thin films in other oxides as well with respect to corresponding values in crystalline form.…”

“…The value of force constant was estimated from the absorption band and listed in Table 1. The value of force constant was found to decrease with increase in annealing temperature (Table 1) indicating a decrease in the bond energy or dissociation energy [18]. Lower dissociation energy implies that less energy is required for the transition of charge carrier from ground state to the first excited state, and hence indicates weakening of the Te-O bond.…”

Fabrication of α-TeO2 smooth and beaded microwires by thermal evaporation method

“…Vinogradov et al [16] obtained large-diameter single crystals of TeO 2 by the Czochralski method in especially designed setups. Nayak et al [17] deposited thin films of tellurium oxide by a RF reactive sputtering technique using a pure tellurium target in the presence of oxygen and argon gases. Lecomte et al [18] deposited TeO 2 thin layers on silica glass substrates by a dip-coating technique from sols prepared in the tellurium isopropoxide-isopropanol-citric acid and water system.…”