Current-voltage characteristics of ultrafine-grained ferroelectric Pb(Zr, Ti)O₃ thin films

Abstract

Room-temperature current-voltage dependence of ultrafine-grained ferroelectric Pb(Zr, Ti)O3 thin films has been investigated. Both strong varistor type behavior and space charge limited conduction (SCLC) were observed. Differences in the current-voltage characteristics are attributed to differences in the nature of the grain boundaries resulting from variations in processing conditions. The strong varistor type behavior is believed to be due to the presence of highly resistive grain boundaries and thus may be termed grain boundary limited conduction (GBLC). A double-depletion-layer barrier model is used to describe the origin of high resistivity of the grain boundaries. It is suggested that the barrier height varies significantly with the applied field due to the nonlinear ferroelectric polarization, and that the barrier is overcome by tunneling at sufficiently high fields. In some other cases, the resistivity of the grain boundaries is comparable to that of the grains, and therefore the intrinsically heterogeneous films degenerate into quasi-homogeneous media, to which the SCLC theory is applicable. As such, a unified grain boundary modeling reconciles different types of conduction mechanisms in the ultrafine-grained ferroelectric thin films. This grain boundary modeling also well accounts for some other dc-related phenomena observed, including abnormal current-voltage dependencies, remanent polarization effect, electrode interface effect, and unusual charging and discharging transients. In addition, many other electrical properties of the ferroelectric films may be better understood by taking the effect of grain boundaries into account.

Low-Temperature Growth of Highly Crystalline (Ba, Sr)TiO[sub 3] Films by CLCB Method

“…The lower leakage current density of the smaller-grained ISTC film may be attributed to the highly resistive grain boundaries that inhibit current flow and cause lower leakage current. 35 The leakage current density of the ISTC film and the ESTC film were 8.0 ϫ 10 Ϫ9 and 2.0 ϫ 10 Ϫ8 A/cm 2 at 1.5 V, respectively.…”

Conduction mechanisms and enhanced multiferroic properties of 2-2 type Bi0.89Sm0.11FeO3–NiFe2O4 composition thin films

“…High internal stresses usually develop around grain boundaries and especially their junctions, where electric charges also accumulate. As a result, minor domains can preferably form at the grain boundaries and their junctions; this is beneficial for enhancing the ferroelectric properties [18]. The grain size of the BFO, BFO-NFO and BSFO-NFO thin films is 80-120, 90-140 and 50-90 nm, respectively.…”

Electrical properties of PLZT thin films formed by photochemical metal-organic deposition with various Zr/Ti ratios

“…Furthermore, the reduction of grain size with decreased Zr/Ti ratio was found from the changes in the diffraction peak width by using Scherrer relation [16]. The lower leakage current density of smallgrained film might be due to the inter-grain depletion of grain boundary limited conduction [17][18][19][20]. Namely, local space charges near grain boundaries inhibit current flow and the overlapped depletion region of neighboring grain boundaries are substantial cause of low leakage current.…”