Sungjae Cho

The authors perform nonlocal four-probe spin-valve experiments on graphene contacted by ferromagnetic Permalloy electrodes. They observe sharp switching and often sign reversal of the nonlocal resistance at the coercive field of the electrodes, indicating the presence of a spin current between injector and detector. The nonlocal spin-valve signal changes magnitude and sign with back-gate voltage, and is observed up to T=300K. The gate voltage variation of the spin-valve signal may result from qu

The magnetic-field-dependent longitudinal and Hall components of the resistivity ${\ensuremath{\rho}}_{\mathrm{xx}}(H)$ and ${\ensuremath{\rho}}_{\mathrm{xy}}(H)$ are measured in graphene on silicon dioxide substrates at temperatures $1.6\phantom{\rule{0.3em}{0ex}}\mathrm{K}\ensuremath{\le}T\ensuremath{\le}300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. At charge densities near the minimum conductivity point ${\ensuremath{\rho}}_{\mathrm{xx}}(H)$ is strongly enhanced and ${\ensuremath{\rho}}_{\mathrm

Ultrathin (approximately three quintuple layer) field-effect transistors (FETs) of topological insulator Bi(2)Se(3) are prepared by mechanical exfoliation on 300 nm SiO(2)/Si susbtrates. Temperature- and gate-voltage-dependent conductance measurements show that ultrathin Bi(2)Se(3) FETs are n-type and have a clear OFF state at negative gate voltage, with activated temperature-dependent conductance and energy barriers up to 250 meV.

Graphitic nanostructures, e.g. carbon nanotubes (CNT) and graphene, have been proposed as ideal materials for spin conduction[1-7]; they have long electronic mean free paths[8] and small spin-orbit coupling[9], hence are expected to have very long spin-scattering times. In addition, spin injection and detection in graphene opens new opportunities to study exotic electronic states such as the quantum Hall[10,11] and quantum spin Hall[9] states, and spin-polarized edge states[12] in graphene ribbo

Aharonov–Bohm oscillations effectively demonstrate coherent, ballistic transport in mesoscopic rings and tubes. In three-dimensional topological insulator nanowires, they can be used to not only characterize surface states but also to test predictions of unique topological behaviour. Here we report measurements of Aharonov–Bohm oscillations in (Bi1.33Sb0.67)Se3 that demonstrate salient features of topological nanowires. By fabricating quasi-ballistic three-dimensional topological insulator nanow

We report the observation of current-induced spin polarization, the Rashba-Edelstein effect (REE), and its Onsager reciprocal phenomenon, the spin galvanic effect (SGE), in a few-layer graphene/2H-TaS₂ heterostructure at room temperature. Spin-sensitive electrical measurements unveil full spin-polarization reversal by an applied gate voltage. The observed gate-tunable charge-to-spin conversion is explained by the ideal work function mismatch between 2H-TaS₂ and graphene, wh

Transistor downscaling by Moore's law has facilitated drastic improvements in information technology, but this trend cannot continue because power consumption issues have pushed Moore's law to its limit. Tunnel field-effect transistors (TFETs) have been suggested to address these issues; however, so far they have not achieved the essential criteria for fast, low-power switches, i.e., an average subthreshold swing over four decades of current (SS_{ave_4dec}) below 60 mV/dec and a current

Electron transport through short, phase-coherent metal-graphene-metal devices occurs via resonant transmission through particle-in-a-box-like states defined by the atomically-sharp metal leads. We study the spectrum of particle-in-a-box states for single- and bi-layer graphene, corresponding to massless and massive two-dimensional (2-D) fermions. The density of states D as a function of particle number n shows the expected relationships D(n) ∼ n 1/2 for massless 2-D fermions (electrons in single

Zero-bias anomalies in topological nanowires have recently captured significant attention, as they are possible signatures of Majorana modes. Yet there are many other possible origins of zero-bias peaks in nanowires--for example, weak localization, Andreev bound states, or the Kondo effect. Here, we discuss observations of differential-conductance peaks at zero-bias voltage in non-superconducting electronic transport through a 3D topological insulator (Bi(1.33)Sb(0.67))Se3 nanowire. The zero-bia

Reductions in transistor size have improved functionality of transistors and lowered costs of electronic processors. However, as transistors decrease in size, quantum tunneling causes increased leakage currents and power consumption. To resolve power consumption issues, tunnel field-effect transistors (TFETs) utilizing band-to-band tunneling (BTBT) have been suggested. Such devices can overcome the 60 mV/dec subthreshold swing (SS) limit that is a disadvantage of conventional metal-oxide-semicon

Today's circuit technology requires low-power transistors and diodes to extend Moore's law. While research has been focused on reducing power consumption of transistors, low-power diodes have not been widely studied. Here, we report a low-power, thus steep-slope Schottky diode, with a “cold metal” source. The Schottky barrier between metal electrode and bulk MoS2 enabled the diode behavior, and the steep-slope diode IV curve originated from the change in the density of states of a graphite (cold

In near future, we envision instant and ubiquitous access to the VR worlds. However, existing highly portable VR devices usually lack rich and convenient input modality. In response, we introduce TouchVR, a system that enables BoD interaction in instant VR supported by mobile HMDs.

The authors investigated the microstructural and the electrical properties of ZnO based dye-sensitized solar cells (DSSCs) fabricated using a low-temperature-processed(200 °C) dye-sensitized ZnO-nanoparticle thin film and a Pt catalyst depositedon ITO/glass by using RF magnetron sputtering. A hydropolymer containing PEG (poly(ethylene glycol)) and PEO (poly ethylene oxide) was used to make uniformly-distributed ZnO nanoparticle layer that form a nano-porous ZnO network after heat treatment and w