Polarization reversal and capacitance-voltage characteristic of epitaxial Pb(Zr,Ti)O3 layers

Abstract

Capacitance-voltage (C–V) measurements were performed on epitaxial layers of Pb(Zr0.2Ti0.8)O3 (PZT) with top and bottom SrRuO3 (SRO) electrodes. It is shown that the sharp capacitance peak∕discontinuity which is present in the C–V characteristics at different frequencies is directly associated with the polarization reversal. The ferroelectric film is assumed as a large band-gap semiconductor with Schottky contacts at the metal-ferroelectric interfaces. The capacitance discontinuity at the reversal (coercive) voltage is associated with a discontinuity in the built-in potential at the PZT∕SRO interfaces. The C–V characteristics for voltage ranges outside the coercive values can be used to extract the free carrier concentrations as in the case of Schottky metal-semiconductor contacts. The carrier concentration was found to be (2–4)×1018cm−3, independent of measuring frequency and temperature up to 1 MHz and 170 °C, respectively, suggesting completely ionized shallow impurities.

Anomalous capacitance–voltage characteristics of Pt–AlGaN/GaN Schottky diodes exposed to hydrogen

“…Fifth, as for the C-V curves at low frequencies, the capacitance in H 2 dramatically increases with decreasing V G down to the V TH as compared with those in N 2 although the capacitance at zero bias is nearly the same value both in N 2 and H 2 , suggesting that the alignment of electric dipoles by applied biases may be related. Similar phenomenon is observed in ferroelectric materials in which the domains can switch from one direction of spontaneous alignment to another when an electric filed is applied, giving rise to large changes in polarization and dielectric constant [9]. Furthermore, the fluctuations of the capacitance observed in the C-V curve at 1 Hz in H 2 may be explained by alignment of hydrogen-related dipoles when the ac oscillation is applied, i.e., the ac oscillation tries to switch the polarity of dipoles, but some of them cannot follow the oscillation simultaneously, resulting in the capacitance fluctuation as a function of the applied bias voltages.…”

Orientation-dependent potential barriers in case of epitaxial Pt–BiFeO3–SrRuO3 capacitors

“…However, the requirement to explain both C-V and I-V characteristics within the frame of the same model requires considering both interface-controlled charge injection into the BFO film and volume-limited charge transport across the BFO film through bulk-related parameters such as carrier mobility. 16,17 The SRO-BFO-Pt structure can be modeled as a back-to-back connection of two Schottky diodes. Unfortunately, due to the unknown conduction type in BFO films it is difficult to establish which of the two interfaces ͑bottom SRO-BFO or top BFO-Pt͒ is reverse biased for a certain polarity.…”

Aging in epitaxial ferroelectric PbTiO3 films

“…The hysteresis originates from the presence and switching of FE polarization. 32 The sharp peaks of capacitance suggest abrupt change of polarization at coercive voltages V c . Also the observed difference between the dynamic and dielectric coercive voltages agrees with the results in Ref.…”