Interplay of ferroelectricity and single electron tunneling

Abstract

We investigate the interplay of ferroelectricity and quantum electron transport at the nanoscale in the regime of Coulomb blockade. Ferroelectric polarization in this case is no longer the external parameter but should be self-consistently calculated along with electron hopping probabilities leading to new physical transport phenomena studying in this paper. These phenomena appear mostly due to effective screening of a grain electric field by ferroelectric environment rather than due to polarization dependent tunneling probabilities. At small bias voltages polarization can be switched by a single excess electron in the grain. In this case transport properties of SET exhibit the instability (memory effect).PACS numbers: 72.80.Tm,77.84.Lf Systems with ferroelectric (FE) elements attract much of attention due to their interesting fundamental properties at the nanoscale as well as due to their possible applications in microelectronics, especially in nonvolatile memory devices, in emerging technologies of Terahertz-detecting and in building of advanced (nano)capacitors.1-14 In quantum junctions the ferroelectricity influences electron transport: Tunneling through the FE barriers shows giant electro-resistance effect caused by the strong dependence of electron tunneling probability on the FE polarization and external bias orientations.7,15 Here we focus on the inverse processthe influence of electron transport on ferroelectricity. 2,10The naive guess would be that a single electron, small quantum object, can slightly influence the macroscopic effect -ferroelectricity. However, we show that this is not quite true and discuss the interplay of ferroelectricity and quantum electron transport at the nanoscale in the regime of Coulomb blockade. Polarization in this case is no longer the external parameter but should be self-consistently calculated along with electron hopping probabilities leading to new physical transport phenomena studying in this paper. These phenomena appear mostly due to effective screening of a grain electric field by ferroelectric environment rather than due to polarization dependent tunneling probabilities.Ferroelectrics (FE) are characterized by the polarization P whose direction and magnitude can be changed by applying an external electric field E larger than the ferroelectric switching field, E s . The ground ferroelectric state of a bulk sample is usually not uniformly polarized but divided into domains to lower the electrostatic energy, like in ferromagnets. 16At the nanoscale to influence the polarization of (nano)ferroelectric one can apply strong enough bias to nanotips:2 There is a well developed technique of imaging and control of domain structures in ferroelectric thin films by a tip of a scanning probe microscope, see, e.g., Refs. 2,7,10,[17][18][19] Here we show how ferroelectric polarization switching can be produced by placing a single excess electron at the nanograin. Charged metal particle creates a strong enough electric field, E ≈ 1 MV/cm around it. Numerous ferroelectric (nano)...

Memory effect in a ferroelectric single-electron transistor: Violation of conductance periodicity in the gate voltage

“…From the first glance physics of such ferroelectric should be similar to physics of SET considered in Ref. 15 with ferroelectric source and drain capacitors. But this is not so.…”

“…Recently it was shown that the presence of ferroelectricity in the source and drain tunnel junctions of single electron transistor (SET) induces memory effect in the current-voltage characteristics even in the limit of negligible hysteresis of the ferroelectric insulators. 15 The bottle-neck of ferroelectric SET is the experimental difficulty to produce ultrathin and ultra small ferroelectric tunnel junctions with special parameters. Technologically it is much easier to produce a nanothin ferroelectric layer but not thin enough for perfect electron tunneling.…”

Conductance of a single electron transistor with a retarded dielectric layer in the gate capacitor

“…Following the mean field theory of the SET with "slow" and weak dielectric layer (0 < χ 0 < χ cr 0 ) [24] in the gate capacitor the conductance in the vicinity of Q 0 = e/(2ǫ 0 ) has the form…”

“…Nanomechanical resonators are usually studied as linear oscillators. In contrast, the FE layer shows the non-linear response since the electric fields in the SET capacitors can exceed the FE saturation field [23,24]. Another important difference is related to the fact that the characteristic time scales of FE materials can be essentially lower than those of the nanomechanical systems and can be even comparable with characteristic times of SET.…”

“…The limit, t FE ≫ t ex , was studied in Refs. [23,24] using the mean field theory. In this case the polarization of FE layers "feels" only the average electric field produced in the SET capacitors.…”