Low value for the static background dielectric constant in epitaxial PZT thin films

Abstract

Ferroelectrics are intensively studied materials due to their unique properties with high potential for applications. Despite all efforts devoted to obtain the values of ferroelectric material constants, the problem of the magnitude of static dielectric constant remains unsolved. In this article it is shown that the value of the static dielectric constant at zero electric field and with negligible contribution from the ferroelectric polarization (also called static background dielectric constant, or just background dielectric constant) can be very low (between 10 and 15), possibly converging towards the value in the optical domain. It is also found that the natural state of an ideal, mono-domain, epitaxial ferroelectric is that of full depletion with constant capacitance at voltages outside the switching domain. The findings are based on experimental results obtained from a new custom method designed to measure the capacitance-voltage characteristic in static conditions, as well from Rayleigh analysis. These results have important implications in future analysis of conduction mechanisms in ferroelectrics and theoretical modeling of ferroelectric-based devices.

Epitaxial ferroelectric interfacial devices

“…Surprisingly, a strong dependence of the dielectric properties with the electrode material has been observed, in the extreme case leading to a strong reduction of the dielectric properties of the dielectric at reduced thicknesses, built-in electric fields, and fatigue. [49][50][51][52][53][54][55][56][57] To a large extent, such phenomena are linked to the physical characteristics of the metal/ferroelectric interface and the key aspects associated with this interface are discussed in section II C.…”

Self-consistently derived sample permittivity in stabilization of ferroelectricity due to charge accumulated at interfaces

“…Recently, values lower by one order of magnitude were reported for this quantity. 22,23 In the following, we comment on this discrepancy.…”

“…It may be computed by using eqn (8), once the thickness of the film and the tetragonality of the unit cell are known; as discussed above, it is quite close to 0. The measurable quantities are: (i) the saturation polarization P s = p s n 0 ; (ii) the Curie temperature, allowing one to estimate the stabilization energy e a = Gp s 2 n 0 /(e 0 k 0 ) in the previous model; (iii) the structure and thickness of the film, allowing one to estimate the parameter G; (iv) the coercive field at zero temperature; if it is measured at T a 0, one can use relations such as eqn (23) to derive its value at T = 0. Normally, the system seems to be uniquely defined.…”

Examination of permittivity for depolarization field of ferroelectric by ab initio calculation, suggesting hidden mechanisms

“…Standard GLD theories are based on a single polarization vector P as the order parameter. We approximate the polarization possibly missed in such GLD theory 29 by an extra permittivity ε NG − 1 35 , 36 , while ε NG is speculatively close to electronic permittivity 29 . The GLD energy F of an insulating FE is F = ( T − T 0 ) P 2 /2C ε 0 + βP 4 /4 + γP 6 /4 − PE d /2, where T 0 , C , β , γ , and θ are Curie–Weiss temperature, Curie constant, and GLD coefficients, respectively.…”