Gate-controlled nonvolatile graphene-ferroelectric memory

Abstract

In this letter, we demonstrate a non-volatile memory device in a graphene FET structure using ferroelectric gating. The binary information, i.e. "1" and "0", is represented by the high and low resistance states of the graphene working channels and is switched by controlling the polarization of the ferroelectric thin film using gate voltage sweep. A non-volatile resistance change exceeding 200% is achieved in our graphene-ferroelectric hybrid devices. The experimental observations are explained by the electrostatic doping of graphene by electric dipoles at the ferroelectric/graphene interface. PACS numbers: Valid PACS appear hereThe discovery of graphene in 2004 [1, 2, 3] has triggered enormous experimental and theoretical efforts [4,5]. As a gapless semiconductor, charge carriers in graphene can be tuned continuously from electrons to holes crossing the charge neutral Dirac point using an external electric field. Unlike conventional semiconductors, the doping process does not influence the mobility of charge carriers in graphene, which can exceed 10 5 cm 2 V −1 s −1 at low temperature [6,7]. Such doping-independent mobility leads to the field-dependent conductance in graphene. Based on these two properties, many novel graphene-based device applications have been predicted or demonstrated [8,9,10,11,12,13,14,15,16], including the heavilyexplored graphene-based field-effect transistor (GFET) [17,18,19,20,21,22]. However, a paradigm shift in the microelectronics industry from Si to graphene also requires graphene-based memory applications. Despite graphene intrinsically having a high resistance state at the Dirac point and a low resistance state when heavily doped, reports on graphene for non-volatile information storage is rarely seen. This is due to the difficulty in maintaining the resistance states in graphene without an external electric field. One chemical modification approach to achieve non-volatile switching in graphene has been recently proposed by Echtermeyer et al [19]. Although this method can achieve very high on-off ratio, it alters the unique crystalline structure of graphene upon which many of the extraordinary electronic properties and hence most novel device concepts are based [4,5].In this letter, we show non-volatile switching in graphene by using ferroelectric gating without having to break the lattice symmetry. We demonstrate basic writing and reading processes of this novel grapheneferroelectric memory device structure combining the field-dependent conductance of graphene with the remnant electric field of ferroelectric thin films. A bistable * Electronic address: phyob@nus.edu.sg FIG. 1: (a) Sample geometry of a finished grapheneferroelectric memory device. (b) Optical image of a graphene sample showing the Hall-bar geometry of the bottom electrodes. (c) R vs VBG of the graphene sample before P(VDF-TrFE) coating, measured in two-terminal configuration. (d) AFM image of another graphene sample after P(VDF-TrFE) spin-coating. The contrast comes from the slightly different crystallization of P(...

Ferroelectrically driven spatial carrier density modulation in graphene

“…Devices based on this concept have demonstrated non-volatile resistance hysteresis [13][14][15] and transparent conductivity in flexible electronics 16,17 . Initial experimental studies, however, achieved charge density changes in graphene much smaller than anticipated from full compensation of the polarization 18 , since the electrostatic coupling can be limited by extrinsic effects caused by adsorbed molecules 15,19,20 .…”

“…A low-power, simple alternative to complex split-gate electrodes can be achieved by coupling graphene to an adjacent, remanent ferroelectric polarization, which can drive changes in the graphene via electrostatic doping from interaction with the polarization 13 . Devices based on this concept have demonstrated non-volatile resistance hysteresis [13][14][15] and transparent conductivity in flexible electronics 16,17 .…”

Quasi-Periodic Nanoripples in Graphene Grown by Chemical Vapor Deposition and Its Impact on Charge Transport

“…[2][3][4][5] Cu-based CVD methods have now made wafer-scale graphene synthesis and transfer feasible both for single layer graphene 6,7 (SLG) and bilayer graphene (BLG). 8 This not only brings the commercial applications of graphene within reach, but also provides great advantages in introducing new substrates to enhance and engineer its electronic properties by tuning the substrate-induced screening 9-12 and substrate-induced strain.…”

Resonant tunneling and intrinsic bistability in twisted graphene structures

“…We stress, however, that relative phases in T j do not alter in any significant way the physics of tunneling in Eq. (6). Furthermore, while the interlayer hopping amplitude t is sensitive to several parameters, e.g., twist angle [19] and the choice of dielectric material [20], its order of magnitude is mainly governed by the wave function overlap between the graphene layers.…”

“…Bistable electronic systems which exhibit fast switching are of interest for applications such as low-power memory and logic [1]. Recently, new realizations of intrinsically bistable systems have been discovered, both in graphene [2][3][4][5][6] and in other systems [7][8][9]. In particular, van der Waals heterostructures comprising graphene layers sandwiched between insulating hexagonal boron nitride (hBN) layers afford electronic environments with tailored band structures and transport characteristics [10].…”