Imprint Model Based on Thermionic Electron Emission Under Local Fields in Ferroelectric Thin Films

Abstract

We investigated the origin of the imprint mechanism of ferroelectric thin films such as PbZr x Ti 1- x O 3 (PZT) or SrBi 2 Ta 2 O 9 (SBT) by considering thermionic field emission under local fields. The electric fields inside the ferroelectric films are represented. Since the poled ferroelectric capacitors have strong local field inside, the thermionic field emission rate is enhanced by tunneling effect. The emission rate is estimated by taking the thermionic field emission into account. The dependence of imprint phenomenon on the emitted electrons from traps is explained in detail. We calculate the voltage shift that results from the imprint phenomenon. Comparing the results with the experiments, we successfully explain the imprint phenomenon based on pinning.