Ferroelectric semiconductor junctions based on graphene/In2Se3/graphene van der Waals heterostructures (original) (raw)
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Polarization-driven resistive switching in ferroelectric tunnel junctions (FTJs)--structures composed of two electrodes separated by an ultrathin ferroelectric barrier--offers new physics and materials functionalities, as well as exciting opportunities for the next generation of non-volatile memories and logic devices. Performance of FTJs is highly sensitive to the electrical boundary conditions, which can be controlled by electrode material and/or interface engineering. Here, we demonstrate the use of graphene as electrodes in FTJs that allows control of interface properties for significant enhancement of device performance. Ferroelectric polarization stability and resistive switching are strongly affected by a molecular layer at the graphene/BaTiO3 interface. For the FTJ with the interfacial ammonia layer we find an enhanced tunnelling electroresistance (TER) effect of 6 × 10(5)%. The obtained results demonstrate a new approach based on using graphene electrodes for interface-faci...
Tuning electronic transport in epitaxial graphene-based van der Waals heterostructures
Nanoscale, 2016
Two-dimensional tungsten diselenide (WSe2) has been used as a component in atomically thin photovoltaic devices, field effect transistors, and tunneling diodes in tandem with graphene. In some applications it is necessary to achieve efficient charge transport across the interface of layered WSe2-graphene, a semiconductor to semimetal junction with a van der Waals (vdW) gap. In such cases, band alignment engineering is required to ensure a low-resistance, ohmic contact. In this work, we investigate the impact of graphene electronic properties on the transport at the WSe2-graphene interface. Electrical transport measurements reveal a lower resistance between WSe2 and fully hydrogenated epitaxial graphene (EGFH) compared to WSe2 grown on partially hydrogenated epitaxial graphene (EGPH). Using low-energy electron microscopy and reflectivity on these samples, we extract the work function difference between the WSe2 and graphene and employ a charge transfer model to determine the WSe2 car...
Nano Letters, 2014
We report the fabrication of both n-type and p-type WSe 2 field effect transistors with hexagonal boron nitride passivated channels and ionic-liquid (IL)-gated graphene contacts. Our transport measurements reveal intrinsic channel properties including a metal-insulator transition at a characteristic conductivity close to the quantum conductance e 2 /h, a high ON/OFF ratio of >10 7 at 170 K, and large electron and hole mobility of µ ≈ 200 cm 2 V-1 s-1 at 160 K. Decreasing the temperature to 77 K increases mobility of electrons to ≈330 cm 2 V-1 s-1 and that of holes to ≈270 cm 2 V-1 s-1. We attribute our ability to observe the intrinsic, phonon limited conduction in both the electron and hole channels to the drastic reduction of the Schottky barriers between the channel and the graphene contact electrodes using IL gating. We elucidate this process by studying a Schottky diode consisting of a single graphene/WSe 2 Schottky junction. Our results indicate the possibility to utilize chemically or electrostatically highly doped graphene for versatile, flexible and transparent low-resistance Ohmic contacts to a wide range of quasi-2D semiconductors.
Wafer-scale graphene/ferroelectric hybrid devices for low-voltage electronics
2011
Preparing graphene and its derivatives on functional substrates may open enormous opportunities for exploring the intrinsic electronic properties and new functionalities of graphene. However, efforts in replacing SiO$_{2}$ have been greatly hampered by a very low sample yield of the exfoliation and related transferring methods. Here, we report a new route in exploring new graphene physics and functionalities by transferring large-scale chemical vapor deposition single-layer and bilayer graphene to functional substrates. Using ferroelectric Pb(Zr$_{0.3}$Ti$_{0.7}$)O$_{3}$ (PZT), we demonstrate ultra-low voltage operation of graphene field effect transistors within pm1\pm1pm1 V with maximum doping exceeding 1013,mathrmcm−210^{13}\,\mathrm{cm^{-2}}1013,mathrmcm−2 and on-off ratios larger than 10 times. After polarizing PZT, switching of graphene field effect transistors are characterized by pronounced resistance hysteresis, suitable for ultra-fast non-volatile electronics.
Combining graphene and organic ferroelectric for possible memory devices
Both ferroelectric materials and graphene attract plenty of scientific attention. Ferroelectrics are well known for their ability to maintain a polarization, which can be switched/reversed by an external electric field. Organic ferroelectrics (e.g. PVDF/TrFE) are of special interest because of their flexibility and durability. Graphene has already demonstrated its promise for future electronics. The two materials brought together give a new functionality of non-volatile memory. Proof-of-concept works have been already done, but only with exfoliated graphene. The main goal of this research is to study the possibility of making such devices using CVD graphene, in large amounts. In other words, we address the feasibility of this kind of graphene-based memory devices. This can be important for graphene-based electronics in the near future.
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Quasi-two-dimensional perovskites have emerged as a new material platform for optoelectronics on account of its intrinsic stability. A major bottleneck to device performance is the high charge injection barrier caused by organic molecular layers on its basal plane, thus the best performing device currently relies on edge contact. Herein, by leveraging on van der Waals coupling and energy level matching between two-dimensional Ruddlesden-Popper perovskite and graphene, we show that the plane-contacted perovskite and graphene interface presents a lower barrier than gold for charge injection. Electron tunneling across the interface occurs via a gate-tunable, direct tunneling-to-field emission mechanism with increasing bias, and photoinduced charge transfer occurs at femtosecond timescale (~50 fs). Field effect transistors fabricated on molecularly thin Ruddlesden-Popper perovskite using graphene contact exhibit electron mobilities ranging from 0.1 to 0.018 cm2V−1s−1 between 1.7 to 200 ...
A Graphene-Edge Ferroelectric Molecular Switch
Nano letters, 2018
We show that polar molecules (water, ammonia, and nitrogen dioxide) adsorbed solely at the exposed edges of an encapsulated graphene sheet exhibit ferroelectricity, collectively orienting and switching reproducibly between two available states in response to an external electric field. This ferroelectric molecular switching introduces drastic modifications to the graphene bulk conductivity and produces a large and ambipolar charge bistability in micrometer-size graphene devices. This system comprises an experimental realization of envisioned memory capacitive ("memcapacitive") devices whose capacitance is a function of their charging history, here conceived via confined and correlated polar molecules at the one-dimensional edge of a two-dimensional crystal.
Physical review letters, 2018
We report the experimental observation of strongly enhanced tunneling between graphene bilayers through a WSe_{2} barrier when the graphene bilayers are populated with carriers of opposite polarity and equal density. The enhanced tunneling increases sharply in strength with decreasing temperature, and the tunneling current exhibits a vertical onset as a function of interlayer voltage at a temperature of 1.5 K. The strongly enhanced tunneling at overall neutrality departs markedly from single-particle model calculations that otherwise match the measured tunneling current-voltage characteristics well, and suggests the emergence of a many-body state with condensed interbilayer excitons when electrons and holes of equal densities populate the two layers.
Graphene is a carbon allotrope in which the atoms are arranged in a two-dimensional honeycomb lattice, which comprises two hexagonal sublattices. The existence of these two sublattices gives rise to the electron pseudospin and, along with the overlapping pz orbitals, to the absence of back-scattering, which give to graphene high-quality transport properties. Graphene is a gapless material and currents in graphene nanoribbons cannot be effectively switched off. This is the most important obstacle for the use of graphene in the fabrication of integrated logic circuits. Recently, theoretical and experimental studies have shown that the conductance on graphene nanoribbons can be controlled in back and top gated graphene devices. Here we use tight-binding Hamiltonians and Non-equilibrium Green's Functions to design and simulate the operation of nanoelectronic graphene devices. We simulate the operation of the graphene FET (GFET), the graphene quantum-point contact and the potentially doped graphene p-n junction. Our results show that the conductance in these graphene devices can be tuned by the geometry of the device, and the top-gate and bottom-gate potentials. This conductance variation shows that graphene can be potentially used as the basic material for the forthcoming carbon based nanoelectronics.