arXiv subjects

Maksym V. Strikha

Publications and source records attributed to Maksym V. Strikha.

23 records · Page 2Linked to original sources

arXiv2016

Limits for the graphene on ferroelectric domain wall p-n-junction rectifier for different regimes of current

Here we present the theory of the conductivity of pn junction (pnJ) in graphene channel, placed on ferroelectric substrate, caused by ferroelectric domain wall (FDW) for the case of arbitrary current regime: from ballistic to diffusive one. We calculated the ratio of the pnJ conductions for opposite polarities of voltages, applied to source and drain electrodes of the channel,G+/G- as the function of the graphene channel length L, electron mean free path λ and ferroelectric substrate permittivity. We have demonstrated, that the small values of G+/G-(0.1 and smaller), which correspond to efficient graphene pnJ based rectifier, can be obtained for the ferroelectrics with high and for the ratios of L/λ~1 or smaller. However, for ferroelectrics with extremely high permittivity(relaxor or PbZrxTi1-xO3 with composition x near the morphotropic phase boundary x=0.52) the ratio G+/G- can be essentially smaller then unity for the case of a pronounced diffusive regime of current as well. This makes the ferroelectric substrates with high permittivity excellent candidates for the fabrication of new generation of rectifiers based on the graphene pnJ. Temperature effect on ratio was studied within Landau-Ginzburg-Devonshire approach. We have demonstrated that rectifying properties of the graphene pnJ become better in the vicinity of Curie temperature. However, for the temperatures higher than Curie temperature the rectifying effect vanishes due to the ferroelectric polarization disappearance.

cond-mat.mtrl-sci↗

arXiv2016

Hysteretic phenomena in GFET: general theory and experiment

We propose a general theory for the analytical description of versatile hysteretic phenomena in a graphene field effect transistor (GFET) allowing for the existence of the external dipoles on graphene free surface and the localized states at the graphene-surface interface. We demonstrated that the absorbed dipole molecules (e.g. dissociated or highly polarized water molecules) can cause hysteretic form of carrier concentration as a function of gate voltage and corresponding dependence of graphene conductivity in GFET on the substrate of different types, including the most common SiO2 and ferroelectric ones. It was shown that the increase of the gate voltage sweeping rate leads to the complete vanishing of hysteresis for GFET on SiO2 substrate, as well as for GFET on ferroelectric substrate for applied electric fields E less than the critical value Ec. For E>Ec the crossover from the hysteresis to antihysteresis takes place. These results well correlate with the available experimental data up to the quantitative agreement. Proposed model takes into consideration the carriers trapping from the graphene channel by the interface states and describes the antihysteresis in GFET on PZT substrate well enough. Obtained results clarify the fundamental principles of GFET operation as well as can be directly applied to describe the basic characteristics of advanced nonvolatile ultra-fast memory devices using GFET on versatile substrates.

cond-mat.mes-hall↗

arXiv2016

Ballistic conductivity of graphene channel with p-n junction on ferroelectric domain wall

We study the impact of the ferroelectric domain wall on the ballistic conductance of the single-layer graphene channel in the heterostructure graphene / physical gap / ferroelectric film using Wentzel-Kramers-Brillouin approximation. Both self-consistent numerical modeling of the electric field and space charge dynamics in the heterostructure and approximate analytical theory show that the domain wall contact with the surface creates p-n junction in graphene channel. We calculated that the carriers' concentration induced in graphene by uncompensated ferroelectric dipoles originated from the spontaneous polarization abrupt near the surface can reach the values of 1019 m-2 order, which is in two orders higher than it can be obtained for the gate doped graphene on non-ferroelectric substrates. Therefore we predict that graphene channel with the p-n junction caused by ferroelectric domain wall would be characterized by rather high ballistic conductivity.

cond-mat.mtrl-sci↗

arXiv2013

Ferroelectric domain triggers the charge modulation in semiconductors

We consider a typical heterostructure domain patterned ferroelectric film/ultra thin dielectric layer/ semiconductor, where the semiconductor can be an electrolyte, paraelectric or multi layered graphene. Unexpectedly we have found that the space charge modulation profile and amplitude in the semiconductor, that screens the spontaneous polarization of a 180-degree domain structure of ferroelectric, depends on the domain structure period, dielectric layer thickness and semiconductor screening radius in a rather non-trivial nonlinear way. Multiple size effects appearance and manifestation are defined by the relationship between these three parameters. In addition, we show that the concept of effective gap can be introduced in a simple way only for a single domain limit. Obtained analytical results open the way for understanding of current AFM maps of contaminated ferroelectric surfaces in ambient atmosphere as well as explore the possibilities of conductivity control in ultra-thin semiconductor layers.

cond-mat.mtrl-sci↗

arXiv2012

Pyroelectric origin of the carrier density modulation at graphene-ferroelectric interface

Using continuous approximation we study the static and high-frequency heat dissipation in multi-layer graphene on a ferroelectric. We demonstrate that the Joule heating effect, caused by a high-frequency ac electric current in graphene, creates a pronounced temperature gradient in a ferroelectric substrate. The pyroelectric effect transforms the gradient into the spontaneous polarization gradient.. Therefore, the high-frequency depolarizing electric field occurs and penetrates in the multi-layer graphene. Free charges in graphene immediately screen the electric field and thus their density oscillates at high-frequency. Performed calculations had proved that the pyroelectric effect can modify essentially the free carrier density at the graphene-ferroelectric interface and consequently the conductivity of multi-layer graphene channel. So, pyroelectric mechanism can be critical for understanding of the complex physical thermal and electrical processes taking place across and along graphene-ferroelectric interfaces at terahertz frequencies.

cond-mat.mtrl-sci↗