Tuning of the Depolarization Field and Nanodomain Structure in Ferroelectric Thin Films

Abstract

The screening efficiency of a metal-ferroelectric interface plays a critical role in determining the polarization stability and hence the functional properties of ferroelectric thin films. Imperfect screening leads to strong depolarization fields that reduce the spontaneous polarization or drive the formation of ferroelectric domains. We demonstrate that by modifying the screening at the metal-ferroelectric interface through insertion of ultrathin dielectric spacers, the strength of the depolarization field can be tuned and thus used to control the formation of nanoscale domains. Using piezoresponse force microscopy, we follow the evolution of the domain configurations as well as polarization stability as a function of depolarization field strength.

Piezoresponse force microscopy study on ferroelectric polarization of ferroelectric polymer thin films with various structural configurations

“…4 and 5, we do observe stable positive and negative polarization states, though ferroelectric domains show some patterns due to the influence of depolarization field. These results indicate, though depolarization field breaks large ferroelectric domain into nanoscale ones, 13 both polarization states still exist and can retain for a relatively long time. The first two facts discussed above for P(VDF-TrFE)/p-Si sructure are still suitable to understand the good polarization retention of P(VDF-TrFE)/Al 2 O 3 /p-Si sructure.…”

“…As for such a P(VDF-TrFE)/p-Si structure, charge compensation may be not sufficiently provided by p-Si and thus depolarization field is not completely screened, which induces depolarization of homogeneous polarization state, leading to either a reduction of the remanent polarization or formation of ferroelectric domain patterns once the removal of poling voltage. 13 Detailed discussion on these inactive domains is much more complicated and out of the scope of this paper. Anyway, in such a P(VDF-TrFE)/p-Si structure, we do observe stable positive and negative polarization states after the removal of poling voltage and both states retain unchanged for at least one hour in our microscopic measurement.…”

“…In fact, effective tuning of depolarization field has been demonstrated through insertion of ultrathin dielectric spacers between PbTiO 3 and SrTiO 3 layers. 13 The strength of the depolarization field can be tuned according to the thickness of the insulating layer and thus used to control the formation of nanoscale ferroelectric domain patterns. Note that here we only chose 5 nm thick Al 2 O 3 layer for our PFM measurements and did not try to illuminate the tuning of depolarization field through the changes in the thickness of dielectric layer.…”

“…However, it can be imagined that with the increase of thickness of Al 2 O 3 layer, depolarization field increases 13 and most of polarization domains are depolarized once poling voltage is removed.…”

Large pyroelectric properties at reduced depolarization temperature in A-site nonstoichiometry composition of lead-free 0.94Na x Bi y TiO3–0.06Ba z TiO3 ceramics

“…Although depolarization temperature is an important parameter in pyroelectric study, its origin has not been fully understood for NBT-xBT. It has more than one definition [27,32,[34][35][36][37], which includes the phase transition temperature from ferroelectric (FE) to antiferroelectric (AFE) phases or from ferroelectric to relaxor [33,34,38,39].…”