Polarization reversal in thin film lithium niobate

Abstract

The direction of polarization in thin-film LiNbO₃ has been shown to be reversible under the influence of an applied electric field at room temperature. These films were r-f sputtered on silicon substrates and their dielectric and photoelectric properties have been characterized previously.¹ They have exhibited photocurrents under illumination which have been attributed to the pyroelectric effect (transient) and the bulk photovoltaic effect (steady state). Polarization reversal was induced by application of a voltage pulse and observed as a reversal in the direction of the photocurrents, and as a current transient whose magnitude is proportional to the spontaneous polarization. An analysis of the switching transient, which is used to understand the reversal mechanism in LiNbO₃ type ferroelectrics, will be presented. From such an analysis it is possible to determine the magnitude of the spontaneous polarization the coercive field necessary for reversal, and the switching speed. These results are compared with previous measurements of the spontaneous polarization of LiNbO₃.² Possible device applications based on these properties will be examined.