Impurity Evaluations of SiO2 Films Formed on LiNbO3 Substrates

SiO2 films deposited by sputtering (SP) and vacuum evaporation (VE) techniques are commonly used as buffer layers in LiNbO3-based devices. The impurity levels in such films are measured as 1017 to 1022 atoms/cm3 for H, Li and Nb ions, which might affect the electrical properties of the devices. The major differences between the SP and VE films are in the density and the hydrogen contents, which possibly influence the I/V characteristics of the films and leads to different dc drift phenomena of LiNbO3 optical modulators made of such layers.