Nonlinear space charge dynamics in mixed ionic-electronic conductors: Resistive switching and ferroelectric-like hysteresis of electromechanical response

Abstract

Articles you may be interested in Frequency dependent dynamical electromechanical response of mixed ionic-electronic conductorsWe performed self-consistent modelling of nonlinear electrotransport and electromechanical response of thin films of mixed ionic-electronic conductors (MIEC) allowing for steric effects of mobile charged defects (ions, protons, or vacancies), electron degeneration, and Vegard stresses. We establish correlations between the features of the nonlinear space-charge dynamics, currentvoltage, and bending-voltage curves for different types of the film electrodes. A pronounced ferroelectric-like hysteresis of the bending-voltage loops and current maxima on the double hysteresis current-voltage loops appear for the electron-transport electrodes. The double hysteresis loop with pronounced humps indicates a memristor-type resistive switching. The switching occurs due to the strong nonlinear coupling between the electronic and ionic subsystems. A sharp meta-stable maximum of the electron density appears near one open electrode and moves to another one during the periodic change of applied voltage. Our results can explain the nonlinear nature and correlation of electrical and mechanical memory effects in thin MIEC films. The analytical expression proving that the electrically induced bending of MIEC films can be detected by interferometric methods is derived. V C 2014 AIP Publishing LLC. [http://dx.

Possible electrochemical origin of ferroelectricity in HfO2 thin films

“…Following this, Noheda group has recently shown that ferroelectric phase of HfO 2 has polarization in (111) orientation, this providing the possible explanation for complex polarization dynamics observed in (100) films [19]. However, in parallel to this intrinsic model for the ferroelectricity, a number of authors offer strong evidence on the role of vacancies on materials behavior, including the role of preparation and annealing conditions, possible reactions at electrodes, and general proximity of ferroelectric and electroresistive switching [20,21,22,23]. For example, Polakowski and Muller [17] used conventional wake-up technology and did not observed ferroelectricity in the 20-nm thick undoped HfO 2 film, while the ferroelectric (FE) phase was observed for undoped HfO 2 film of thickness h ~ 35 nm by Nishimura et al [16], who annealed the films in N 2 atmosphere.…”

Surface-screening mechanisms in ferroelectric thin films and their effect on polarization dynamics and domain structures

“…Mixed ionic-electronic conductors, such as solids with rechargeable ions or vacancies, which also can be mobile, free electrons and/or holes, can display a reversible dynamics of the space charge layers that leads to a pronounced resistive switching between meta-stable states with high and low resistance [93][94][95][96][97][98] and unique dynamic properties (including hysteretic) electromechanical response. [99][100][101][102][103][104][105][106] Though ferroelectrics with mixed type conductivity (FeMIECs) are promising candidates for the nonvolatile and memristive [107][108][109] memory devices, the physical principles of the charge transfer phenomena at their surfaces and interfaces are far from clear. [102] Space charge dynamics in ferroelectric thin films were studied theoretically primarily in the framework of linear drift-diffusion Poisson-Planck-Nernst theory and diluted species approximation.…”

“…[99][100][101][102][103][104][105][106] Though ferroelectrics with mixed type conductivity (FeMIECs) are promising candidates for the nonvolatile and memristive [107][108][109] memory devices, the physical principles of the charge transfer phenomena at their surfaces and interfaces are far from clear. [102] Space charge dynamics in ferroelectric thin films were studied theoretically primarily in the framework of linear drift-diffusion Poisson-Planck-Nernst theory and diluted species approximation. [105,107,110,111] However one can expect a strong correlation between the electrochemical and electromechanical response in FeMIECs, because the spatial gradient of mobile species (ions, vacancies and electrons) concentration near the surface caused by electromigration (electric field-driven for charged species) and diffusion (concentration gradientdriven for both charged and neutral species) mechanisms can change the lattice molar volume.…”

Ferroelectric or non-ferroelectric: Why so many materials exhibit “ferroelectricity” on the nanoscale

“…ESM was extended to regimes with both diffusive and migration transport for open and blocking 259 electrodes, giving rise to more complex time dispersion of responses. 289,328 The important aspect of pure Vegard mechanisms is that it does not predict the formation of remnant states with opposite electromechanical responses and hysteresis loops beyond kinetic ones. Combined with the explicit assumption of fast surface reactions, these mechanisms can be relegated to purely electrochemical systems under rapid electrochemical control, e.g.…”