Ambipolar Thickness-Dependent Thermoelectric Measurements of WSe.

Thermoelectric materials can harvest electrical energy from temperature gradients, and could play a role as power supplies for sensors and other devices. Here, we characterize fundamental in-plane electrical and thermoelectric properties of layered WSe over a range of thicknesses, from 10 to 96 nm, between 300 and 400 K. The devices are electrostatically gated with an ion gel, enabling us to probe both electron and hole regimes over a large range of carrier densities.

Nonequilibrium Phonon Thermal Resistance at MoS/Oxide and Graphene/Oxide Interfaces.

Accurate measurements and physical understanding of thermal boundary resistance () of two-dimensional (2D) materials are imperative for effective thermal management of 2D electronics and photonics. In previous studies, heat dissipation from 2D material devices was presumed to be dominated by phonon transport across the interfaces. In this study, we find that, in addition to phonon transport, thermal resistance between nonequilibrium phonons in the 2D materials could play a critical role too when the 2D material devices are internally self-heated, either optically or electrically.

Ultrathin Three-Monolayer Tunneling Memory Selectors.

High-density memory arrays require selector devices, which enable selection of a specific memory cell within a memory array by suppressing leakage current through unselected cells. Such selector devices must have highly nonlinear current-voltage characteristics and excellent endurance; thus selectors based on a tunneling mechanism present advantages over those based on the physical motion of atoms or ions. Here, we use two-dimensional (2D) materials to build an ultrathin (three-monolayer-thick) tunneling-based memory selector.

High-Performance p-n Junction Transition Metal Dichalcogenide Photovoltaic Cells Enabled by MoO Doping and Passivation.

Layered semiconducting transition metal dichalcogenides (TMDs) are promising materials for high-specific-power photovoltaics due to their excellent optoelectronic properties. However, in practice, contacts to TMDs have poor charge carrier selectivity, while imperfect surfaces cause recombination, leading to a low open-circuit voltage () and therefore limited power conversion efficiency (PCE) in TMD photovoltaics. Here, we simultaneously address these fundamental issues with a simple MoO ( ≈ 3) surface charge-transfer doping and passivation method, applying it to multilayer tungsten disulfide (WS) Schottky-junction solar cells with initially near-zero .

Tuning electrical and interfacial thermal properties of bilayer MoSvia electrochemical intercalation.

Layered two-dimensional (2D) materials such as MoShave attracted much attention for nano- and opto-electronics. Recently, intercalation (e.g.

High Current Density in Monolayer MoS Doped by AlO.

Semiconductors require stable doping for applications in transistors, optoelectronics, and thermoelectrics. However, this has been challenging for two-dimensional (2D) materials, where existing approaches are either incompatible with conventional semiconductor processing or introduce time-dependent, hysteretic behavior. Here we show that low-temperature (<200 °C) substoichiometric AlO provides a stable -doping layer for monolayer MoS, compatible with circuit integration.

Uncovering the Effects of Metal Contacts on Monolayer MoS.

Metal contacts are a key limiter to the electronic performance of two-dimensional (2D) semiconductor devices. Here, we present a comprehensive study of contact interfaces between seven metals (Y, Sc, Ag, Al, Ti, Au, Ni, with work functions from 3.1 to 5.

Publisher Correction: An electrochemical thermal transistor.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Ultrahigh thermal isolation across heterogeneously layered two-dimensional materials.

Heterogeneous integration of nanomaterials has enabled advanced electronics and photonics applications. However, similar progress has been challenging for thermal applications, in part due to shorter wavelengths of heat carriers (phonons) compared to electrons and photons. Here, we demonstrate unusually high thermal isolation across ultrathin heterostructures, achieved by layering atomically thin two-dimensional (2D) materials.

Fast Spiking of a Mott VO-Carbon Nanotube Composite Device.

The recent surge of interest in brain-inspired computing and power-efficient electronics has dramatically bolstered development of computation and communication using neuron-like spiking signals. Devices that can produce rapid and energy-efficient spiking could significantly advance these applications. Here we demonstrate direct current or voltage-driven periodic spiking with sub-20 ns pulse widths from a single device composed of a thin VO film with a metallic carbon nanotube as a nanoscale heater, without using an external capacitor.

Localized Triggering of the Insulator-Metal Transition in VO Using a Single Carbon Nanotube.

Vanadium dioxide (VO) has been widely studied for its rich physics and potential applications, undergoing a prominent insulator-metal transition (IMT) near room temperature. The transition mechanism remains highly debated, and little is known about the IMT at nanoscale dimensions. To shed light on this problem, here we use ∼1 nm-wide carbon nanotube (CNT) heaters to trigger the IMT in VO.

Spatial Separation of Carrier Spin by the Valley Hall Effect in Monolayer WSe Transistors.

We investigate the valley Hall effect (VHE) in monolayer WSe field-effect transistors using optical Kerr rotation measurements at 20 K. While studies of the VHE have so far focused on n -doped MoS, we observe the VHE in WSe in both the n - and p -doping regimes. Hole doping enables access to the large spin-splitting of the valence band of this material.

An electrochemical thermal transistor.

The ability to actively regulate heat flow at the nanoscale could be a game changer for applications in thermal management and energy harvesting. Such a breakthrough could also enable the control of heat flow using thermal circuits, in a manner analogous to electronic circuits. Here we demonstrate switchable thermal transistors with an order of magnitude thermal on/off ratio, based on reversible electrochemical lithium intercalation in MoS thin films.

Unipolar n-Type Black Phosphorus Transistors with Low Work Function Contacts.

Black phosphorus (BP) is a promising two-dimensional (2D) material for nanoscale transistors, due to its expected higher mobility than other 2D semiconductors. While most studies have reported ambipolar BP with a stronger p-type transport, it is important to fabricate both unipolar p- and n-type transistors for low-power digital circuits. Here, we report unipolar n-type BP transistors with low work function Sc and Er contacts, demonstrating a record high n-type current of 200 μA/μm in 6.

Temperature-Dependent Thermal Boundary Conductance of Monolayer MoS by Raman Thermometry.

The electrical and thermal behavior of nanoscale devices based on two-dimensional (2D) materials is often limited by their contacts and interfaces. Here we report the temperature-dependent thermal boundary conductance (TBC) of monolayer MoS with AlN and SiO, using Raman thermometry with laser-induced heating. The temperature-dependent optical absorption of the 2D material is crucial in such experiments, which we characterize here for the first time above room temperature.

Investigation of the Anxiolytic and Antidepressant Effects of Eucalyptol (1,8-Cineole), a Compound From Eucalyptus, in the Adult Male Sprague-Dawley Rat.

Anxiety and depression are debilitating, costly psychological disorders that account for $133 billion in direct medical expenses per year in the United States. Finding alternative means of treatment to reduce the personal and financial burden for patients with these disorders, while maintaining patient safety, is vital for overall patient wellness. The purposes of this study were 2-fold: (1) to determine if pure eucalyptol (1,8-cineole) produces anxiolytic and/or antidepressant effects using rat models for anxiety and behavioral despair and (2) to determine the effects of eucalyptol at the benzodiazepine site on the γ-aminobutyric acid (GABA) A receptor in the rat central nervous system.

Rapid Flame Synthesis of Atomically Thin MoO down to Monolayer Thickness for Effective Hole Doping of WSe.

Two-dimensional (2D) molybdenum trioxide (MoO) with mono- or few-layer thickness can potentially advance many applications, ranging from optoelectronics, catalysis, sensors, and batteries to electrochromic devices. Such ultrathin MoO sheets can also be integrated with other 2D materials (e.g.

Field effect transistors with current saturation and voltage gain in ultrathin ReS2.

We report the fabrication and device characteristics of exfoliated, few-layer, dual-gated ReS2 field effect transistors (FETs). The ReS2 FETs display n-type behavior with a room temperature Ion/I(off) of 10(5). Many devices were studied with a maximum intrinsic mobility of 12 cm(2) · V(-1) · s(-1) at room temperature and 26 cm(2) · V(-1) · s(-1) at 77 K.

Oxidized titanium as a gate dielectric for graphene field effect transistors and its tunneling mechanisms.

We fabricate and characterize a set of dual-gated graphene field effect transistors using a novel physical vapor deposition technique in which titanium is evaporated onto the graphene channel in 10 Å cycles and oxidized in ambient to form a top-gate dielectric. A combination of X-ray photoemission spectroscopy, ellipsometry, and transmission electron microscopy suggests that the titanium is oxidizing in situ to titanium dioxide. Electrical characterization of our devices yields a dielectric constant of κ = 6.