Electric field stabilization for temperature driven variation of permittivity in ferroelectric devices

Abstract

The Ginzburg–Devonshire phenomenological approach is used to define the correlation between temperature and electric field magnitudes required to keep permanent values of permittivity of ferroelectrics in rather broad range of operating temperatures. The existence of a crossover of the electric field dependencies for ε at different temperatures is demonstrated theoretically. It makes it possible to establish the upper limit of electrical field strength necessary to provide the thermal stability of ferroelectric devices. Theoretical results have been confirmed experimentally with (Ba,Sr)TiO3 thin film measurements.

Thermally activated polarization dynamics under the effects of lattice mismatch strain and external stress in ferroelectric film

“…The link between the reversed polarization and these important parameters is given by the J 1 ð1Þ, t sw and the energy. The additional factor (1 À J 1 ð1Þ) in relation (14) accounts for the fact that at equilibrium not all the polar sites are necessarily reversed. The amount of reversed polarization can be 0 if J 1 ð1Þ ¼ 1, 2P s if J 1 ð1Þ ¼ 0 (i.e., full reversal) and it can take fractional values 2P S ð1 À J 1 ð1ÞÞ when J 1 ð1Þ 6 ¼ 0 or 1.…”

“…This relation can be approximated, especially in the case E appl = 0, by the expression 20 t SW À1 ¼ t 0 Á e ÀðW B ÀP s E appl Þ=ðk b TÞ : However, it is important to mention that the real switching time is defined as the time taken for the switching current to drop from its maximum value to zero. Using relation (14), the switching current is defined as…”

“…5,[9][10][11] Furthermore, the ferroelectric materials are sensitive to the temperature, and the ferroelectric field effect transistor (FeFET) memory device is apt to be working in an environment with large temperature fluc-tuations, which significantly degrades the performances of the devices. [12][13][14][15] Therefore, a study of the combined effects of the lattice mismatch strain, external stress, and temperature on polarization switching of ferroelectric films is highly desirable.…”