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

The anomalous elastic properties of TeO
_2+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 TeO
_2+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 TeO
_2+x
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
^-40
C
^-1
and TC(C
¹¹
) = (35.0 to 645.5) x 10
^-4deg
C
^-1
against the negative values TC(Cn) = -2.7 x 10
^-4deg
C
^-1
and TC(C
₁₁
) = -0.73 x 10
^-4deg
C
^-1
reported for TeO
₂
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 TeO
_2+x
films grown in 100% O
₂
are useful for potential application in the design of temperature stable surface acoustic wave devices.