Anomalous elastic properties of RF-sputtered amorphous TeO2+x thin film for temperature-stable SAW device applications

The anomalous elastic properties of TeO2+x thin films deposited by rf diode sputtering on substrates at room temperature have been studied. The deposited films are amorphous, and IR spectroscopy reveals the formation of Te-O bond. X-ray photoelectron spectroscopy confirms the variation in the stoichiometry of TeO2+x film from x = 0 to 1 with an increase in the oxygen percentage in processing gas composition. The elastic parameters of the films in comparison to the reported values for TeO2 single crystal are found to be low. However, the temperature coefficients of elastic parameters of all deposited films exhibit anomalous behavior showing positive values for TC(C-11) in the range (32.0 to 600.0) x 10(-4)degrees C-1 and TC(C-44) = (35.0 to 645.5) x 10(-4)degrees C-1 against the negative values (TC(C-11) = -2.7 x 10(-4)degrees C-1 and TC(C-44) = -0.73 x 10(-4)degrees C-1) reported for TeO2 single crystal. The variation in the elastic parameters and their temperature coefficients is correlated with the change in the three-dimensional network of Te-O bonding. The anomalous elastic properties of the TeO2+x films grown in 100% O-2 are useful for potential application in the design of temperature stable surface acoustic wave devices.