Space charge contribution to the apparent enhancement of polarization in ferroelectric bilayers and multilayers

The authors study the effect of interfacial space charge in ferroelectric multilayers through a thermodynamic formalism. Using an electrostatic approach that takes into account the presence of trapped charges between the layers, the authors show that considerable modification in electrical properties can be exhibited, giving rise to polarization enhancement depending on the type of dopants and configuration of the layers. Space charge effect becomes more pronounced in structures with smaller ferroelectric layer fractions. It is shown that built-in polarization due to space charge can stabilize a switchable ferroelectric polarization at small fractions of the ferroelectric layer in a paraelectric matrix. (C) 2007 American Institute of Physics.