Position-sensitive-detectors (PSDs) based on lateral photoeffect has been widely used in diverse applications, including optical engineering, aerospace and military fields. With increasing demand in long distance, low energy consumption, and weak signal sensing systems, the poor responsivity of conventional PSDs has become a bottleneck limiting its applications. Herein, we present a high performance graphene based PSDs with revolutionary interfacial amplification mechanism. Signal amplification in the order of ~10^4 has been demonstrated by utilizing the ultrahigh mobility of graphene and long lifetime of photo-induced carriers at the interface of SiO2/Si. This would improve the detection limit of Si-based PSDs from uW to nW level, without sacrificing the spatial resolution and response speed. Such interfacial amplification mechanism is compatible with current Si technology and can be easily extended to other sensing systems.
Graphene is a two-dimensional (2D) semimetal with high mobility in charge carriers due to the existence of Dirac points. Silicene is another promising material, with properties analog to graphene. Many silicon (Si) based electronic devices can be integrated via graphene-silicene (Gra/si) hybrid structures. These electronic applications are mostly based on the ability to tune the bandgap via electronic structure deformation that is expected to be achieved by multilayer stacking, applying a transverse external electric field (EF), and altering interfacial distance. In this work, we investigate t…
Integration of two-dimensional (2D) van der Waals (vdWs) materials with non-2D materials to realize mixed-dimensional heterostructures has potential for creating functional devices beyond the reach of existing materials and has long been a pursuit of the material science community. Here we report the patterning of monolayer/bilayer transition metal dichalcogenide (TMD) nanostructures with nanometer-precision, tunable sizes and sites at interfaces of graphene/TMD heterostructures. Our experiments demonstrate that the TMD nanostructures can be created at selected positions of the interface using…
Exploring the mechanism of interfacial thermal transport and reducing the interfacial thermal resistance is of great importance for thermal management and modulation. Herein, the interfacial thermal resistance between overlapped graphene nanoribbons is largely reduced by adding bonded carbon chains by performing molecular dynamics simulations. And the analytical model (cross-interface model, CIM) is utilized to analyze and explain the two-dimensional thermal transport mechanism at cross-interface. An order of magnitude reduction in interfacial thermal resistance is found as the graphene nanori…
Graphene quality indicators obtained by Raman spectroscopy have been correlated to the structural changes of the graphene/Germanium interface as a function of in-vacuum thermal annealing. Specifically, it is found that graphene becomes markedly defected at 650 °C. By combining scanning tunneling microscopy, x-Ray Photoelectron Spectroscopy and Near Edge x-ray Absorption Fine Structure Spectroscopy, we conclude that these defects are due to the release of H_{2} gas trapped at the graphene/Germanium interface. The H_{2} gas was produced following the transition from the as-grown hydrogen-termina…
Recent studies showed that the in-plane and inter-plane thermal conductivities of two-dimensional (2D) MoS2 are low, posing a significant challenge in heat management in MoS2-based electronic devices. To address this challenge, we design the interfaces between MoS2 and graphene by fully utilizing graphene, a 2D material with an ultra-high thermal conduction. We first perform ab initio atomistic simulations to understand the bonding nature and structure stability of the interfaces. Our results show that the designed interfaces, which are found to be connected together by strong covalent bonds b…
The temperature ($\it T$) dependence of electrical resistivity in graphene has been experimentally investigated between 10 and 400 K for samples prepared on various substrates; HfO$_2$, SiO$_2$ and h-BN. The resistivity of graphene shows a linear $\it T$-dependence at low $\it T$ and becomes superlinear above a substrate-dependent transition temperature. The results are explained by remote interfacial phonon scattering by surface optical phonons at the substrates. The use of an appropriate substrate can lead to a significant improvement in the charge transport of graphene.
Intercalation is an established technique for tailoring the electronic structure of epitaxial graphene. Moreover, it enables the synthesis of otherwise unstable two-dimensional (2D) layers of elements with unique physical properties compared to their bulk versions due to interfacial quantum confinement. In this work, we present uniformly Pb-intercalated quasi-freestanding monolayer graphene on SiC, which turns out to be essentially charge neutral with an unprecedented $p$-type carrier density of only $(5.5\pm2.5)\times10^9$ cm$^{-2}$. Probing the low-energy electronic structure throughout the …
Realization of high-quality van der Waals (vdW) heterostructures with tailored properties by stacking two-dimensional (2D) layers requires atomically clean interfaces. Because of strong adhesion between the constituent layers, the vdW forces could drive trapped contaminants together into submicron-size bubbles, which leaves large interfacial areas atomically clean. Such a phenomenon is dubbed self-cleaning mechanism in 2D systems. Here, we demonstrate the breakdown of self-cleaning mechanism for nanoscale interfacial bubbles in tiny-angle twisted bilayer graphene (TBG). In the tiny-angle TBG, …
MXene-based heterostructures have received considerable interest owing to their unique properties. Herein, we examine various heterostructures of a prototypical MXene and graphene using density functional theory. We find that the adhesion energy, charge transfer, and band structure of these heterostructures are sensitive not only to the surface functional group, but also to the stacking order. Difference in work function dictates the direction and amount of electron transfer across the interface, which causes a shift in the Dirac point of the graphene bands in the heterostructures of monolayer…
The generation of non-equilibrium electron spin polarization, spin transport, and spin detection are fundamental in many quantum devices. We demonstrate that a lattice of magnetic nanodots enhances the electron spin polarization in monolayer graphene via carrier exchange. We probed the spin polarization through a resistively-detected variant of electron spin resonance (ESR) and observed resonance amplification mediated by the presence of the nanodots. Each nanodot locally injects a surplus of spin-polarized carriers into the graphene, and the ensemble of all "spin hot spots" generates a non-eq…
Tunnel-Barrier-Engineered Ultrafast Demagnetization and Spin Transport in Graphene-Based Heterostructures
S. N. Bose National Center for Basic Sciences（S.N. 玻色基础科学国家中心）；Indian Institute of Science Education and Research Kolkata（加尔各答印度科学与教育研究所）；Uppsala University（乌普萨拉大学）
Layer-Dependent Interfacial Coupling and Exciton Pinning in WSe2/Graphene Heterostructures
Empa – Swiss Federal Laboratories for Materials Science and Technology（瑞士联邦材料科技研究所）；University of Basel（巴塞尔大学）；Swiss Nanoscience Institute, University of Basel（巴塞尔大学瑞士纳米科学研究所）；The Pennsylvania State University（宾夕法尼亚州立大学）
The interfacial coupling between electrons and magnons in adjacent layers can mediate an attractive electron-electron interaction and induce superconductivity. We consider magic-angle twisted bilayer graphene sandwiched between two ferromagnetic insulators to optimize this effect. As a result, magnons induce an interlayer superconducting state characterized by $p$-wave symmetry. We investigate two candidate ferromagnets. The van der Waals ferromagnet CrI$_3$ stands out because it allows compression to tune the superconducting state with an exponential sensitivity. This control adds a new dimen…
Heat transfer across interfaces of graphene and polar dielectrics (e.g. SiO2) could be mediated by direct phonon coupling, as well as electronic coupling with remote interfacial phonons (RIPs). To understand the relative contribution of each component, we develop a new pump-probe technique, called voltage-modulated thermoreflectance (VMTR), to accurately measure the change of interfacial thermal conductance under an electrostatic field. We employed VMTR on top gates of graphene field-effect transistors and find that the thermal conductance of SiO2/graphene/SiO2 interfaces increases by up to ΔG…
Ferroelectric switching of interfacial dipoles in $α$-RuCl$_3$/graphene heterostructure
Daegu Gyeongbuk Institute of Science and Technology (DGIST)（大邱庆北科学技术院）；Pohang University of Science and Technology（浦项科技大学）；Institute for Basic Science（基础科学研究院）；National Institute for Materials Science（国立材料研究所）；California Institute of Technology（加州理工学院）
Strong electric fields can accelerate molecular dissociation reactions. The phenomenon known as the Wien effect was previously observed using high-voltage electrolysis cells that produced fields of about 10^7 V m-1, sufficient to accelerate the dissociation of weakly bound molecules (e.g., organics and weak electrolytes). The observation of the Wien effect for the common case of water dissociation (H2O = H+ + OH-) has remained elusive. Here we study the dissociation of interfacial water adjacent to proton-permeable graphene electrodes and observe strong acceleration of the reaction in fields r…
We demonstrate a large-area passivation layer for graphene by mechanical transfer of ultrathin amorphous Ga$_2$O$_3$ synthesized on liquid Ga metal. A comparison of temperature-dependent electrical measurements of millimetre-scale passivated and bare graphene on SiO$_2$/Si indicate that the passivated graphene maintains its high field effect mobility desirable for applications. Surprisingly, the temperature-dependent resistivity is reduced in passivated graphene over a range of temperatures below 220 K, due to the interplay of screening of the surface optical phonon modes of the SiO$_2$ by hig…
Interfacial thermal transport between electrodes and polymer electrolytes can play a crucial role in the thermal management of solid-state lithium-ion batteries (SLIBs). Modifying the electrode surface with functional molecules can effectively increase the interfacial thermal conductance (ITC) between electrodes and polymers (e.g., electrolytes, separators); however, how they influence the interfacial thermal transport in SLIBs during charge/discharge remains unknown. In this work, we conduct molecular dynamics (MD) simulations to investigate the ITC between charged electrodes and solid-state …
Surface Acoustic Wave Amplification by DC-Voltage Supplied to Graphene Film
利用高分辨率X射线衍射测量方法，研究了外加电流作用下，声表面波在Ca 3 TaGa 3Si 2 O 14（CTGS）压电晶体表面石墨烯薄膜中的传播特性.在这里，我们表明，第一次的应用程序的DC场导致SAW幅度的显着增强，因此，放大的衍射卫星。在施加+10V外部直流电压的情况下，在471 MHz处观察到卫星+1的放大率为33.2 dB/cm，卫星+2的放大率为13.8 dB/cm。SAW的放大发生在比使用体半导体的系统的DC场小得多的DC场之上。理论估计与我们对其他材料的实验数据的测量和分析是合理的。
Propagating edge and interfacial states in corrugated graphene: Robustness and configurability
University of Science and Technology Houari Boumediene（哈乌阿里·布麦迪内科技大学）；Ecole Supérieure des Sciences des Aliments et des Industries Agroalimentaires（食品科学与食品工业高等学院）；The University of Hong Kong（香港大学）；Ohio University（俄亥俄大学）
Interfacial electron-transfer (ET) reactions underpin the interconversion of electrical and chemical energy. Pioneering experiments showed that the ET rate depends on the Fermi Dirac distribution of the electronic density of states (DOS) of the electrode, formalized in the Marcus Hush Chidsey (MHC) model. Here, by controlling interlayer twists in well-defined trilayergraphene moires, we show that ET rates are strikingly dependent on electronic localization in each atomic layer, and not the overall DOS. The large degree of tunability inherent to moire electrodes leads to local ET kinetics that …
The radiative heat transfer between two dielectrics can be strongly enhanced in the near field in the presence of surface phonon-polariton resonances. Nevertheless, the spectral mismatch between the surface modes supported by two dissimilar materials is responsible for a dramatic reduction of the radiative heat flux they exchange. In the present paper we study how the presence of a graphene sheet, deposited on the material supporting the surface wave of lowest frequency, allows to widely tune the radiative heat transfer, producing an amplification factor going up to one order of magnitude. By …
In this paper, we establish the existence of both compressive stress and charge transfer process in hydrothermally synthesized cobalt ferrite-graphene oxide (CoFe2O4/GO) nanocomposites. Transmission electron microscopy (TEM) results reveal the decoration of CoFe2O4 nanoparticles on GO sheets. Magnetic response of nanocomposites was confirme from superconducting quantum interference device (SQUID) magnetometer measurement. Optical properties of these nanocomposites were investigated by Raman spectroscopy. Interfacial compressive stress involved in this system is evaluated from observed blue shi…
Combining both vertical and in-plane two-dimensional (2D) heterostructures opens up the possibility to create an unprecedented architecture using 2D atomic layer building blocks. The thermal transport properties of such mixed heterostructures, critical to various applications in nanoelectronics, however, have not been thoroughly explored. Herein, we construct two configurations of multilayer in-plane graphene/hexagonal boron nitride (Gr/h-BN) heterostructures (i.e. mixed heterostructures) via weak van der Waals (vdW) interactions and systematically investigate the dependence of their interfaci…
Correlated Insulating States in Twisted Double Bilayer Graphene Enhanced by Interfacial Effect on CrOCl
Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院物理研究所）；High Field Magnet Laboratory (HFML-EMFL), Radboud University（拉德堡德大学高场磁实验室）；Research Center for Functional Materials（功能材料研究中心）
Parametric amplification is widely used in nanoelectro-mechanical systems to enhance the transduced mechanical signals. Although parametric amplification has been studied in different mechanical resonator systems, the nonlinear dynamics involved receives less attention. Taking advantage of the excellent electrical and mechanical properties of graphene, we demonstrate electrical tunable parametric amplification using a doubly clamped graphene nanomechanical resonator. By applying external microwave pumping with twice the resonant frequency, we investigate parametric amplification in the nonline…
Exploiting 2D materials for spintronic applications can potentially realize next-generation devices featuring low-power consumption and quantum operation capability. The magnetic exchange field (MEF) induced by an adjacent magnetic insulator enables efficient control of local spin generation and spin modulation in 2D devices without compromising the delicate material structures. Using graphene as a prototypical 2D system, we demonstrate that its coupling to the model magnetic insulator (EuS) produces a substantial MEF (> 14 T) with potential to reach hundreds of Tesla, which leads to orders-of…
Plasmon oscillations have been intensively studied for more than forty years in conventional two-dimensional electron gas systems in order to find new alternatives to the vacuum devices based on the Smith-Purcell effect in the far-infrared region. However, beside the multiple endeavors, up to date, the plasmon generation in semiconductor heterostructures has been very inefficient. Here we demonstrate that the use of high mobility graphene metamaterials, due to their well-known stronger light-plasmon coupling compared to semiconductor materials can significantly improve the efficiency of far-in…
Motivated by the recent experiments [Scientific reports 6, 23051 (2016), Phys. Rev. Lett. 114, 096602 (2015)], we theoretically investigate Cooper pair splitting current in a graphene based Cooper pair beam splitter geometry. By considering the graphene based superconductor as an entangler device, instead of normal (2D) BCS superconductor, we show that the Cooper pair splitting current mediated by Crossed Andreev process is amplified compared to its normal superconductor counterpart. This amplification is attributed to the strong suppression of local normal Andreev reflection process (arising …
When Fe, which is a typical ferromagnet using d- or f-orbital states, is combined with 2D materials such as graphene, it offers many opportunities for spintronics. The origin of 2D magnetism is from magnetic insulating behaviors, which could result in magnetic excitations and also proximity effects. However, the phenomena were only observed at extremely low temperatures. Fe and graphene interfaces could control spin structures in which they show a unique atomic spin modulation and magnetic coupling through the interface. Another reason for covering graphene on Fe is to prevent oxidation under …
