Mahito Yamamoto

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Two-dimensional layered crystals could show phonon properties that are markedly distinct from those of their bulk counterparts, because of the loss of periodicities along the c-axis directions. Here we investigate the phonon properties of bulk and atomically thin α-MoTe2 using Raman spectroscopy. The Raman spectrum of α-MoTe2 shows a prominent peak of the(More)
We report ambipolar charge transport in α-molybdenum ditelluride (MoTe2 ) flakes, whereby the temperature dependence of the electrical characteristics was systematically analyzed. The ambipolarity of the charge transport originated from the formation of Schottky barriers at the metal/MoTe2 contacts. The Schottky barrier heights as well as the current on/off(More)
Single-layer graphene (SLG) supported on SiO(2) shows anomalously large chemical reactivity compared to thicker graphene, with charge inhomogeneity-induced potential fluctuations or topographic corrugations proposed as the cause. Here we systematically probe the oxidative reactivity of graphene supported on substrates with different surface roughnesses and(More)
Growth of a uniform oxide film with a tunable thickness on two-dimensional transition metal dichalcogenides is of great importance for electronic and optoelectronic applications. Here we demonstrate homogeneous surface oxidation of atomically thin WSe2 with a self-limiting thickness from single- to trilayers. Exposure to ozone (O3) below 100 °C leads to the(More)
Understanding the interfacial electrical properties between metallic electrodes and low-dimensional semiconductors is essential for both fundamental science and practical applications. Here we report the observation of thickness reduction induced crossover of electrical contact at Au/MoS2 interfaces. For MoS2 thicker than 5 layers, the contact resistivity(More)
A doping-free transistor made of ambipolar α-phase molybdenum ditelluride (α-MoTe2) is proposed in which the transistor polarity (p-type and n-type) is electrostatically controlled by dual top gates. The voltage signal in one of the gates determines the transistor polarity, while the other gate modulates the drain current. We demonstrate the transistor(More)
Transition metal oxides show much promise as effective p-type contacts and dopants in electronics based on transition metal dichalcogenides. Here we report that atomically thin films of under-stoichiometric tungsten oxides (WOx with x < 3) grown on tungsten diselenide (WSe2) can be used as both controlled charge transfer dopants and low-barrier contacts for(More)
The polarity of the charge carriers injected through Schottky junctions of α-phase molybdenum ditelluride (α-MoTe2) and various metals was characterized. We found that the Fermi-level pinning in the metal/α-MoTe2 Schottky junction is so weak that the polarity of the carriers (electron or hole) injected from the junction can be controlled by the work(More)
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. We study the second-order Raman process of mono-and few-layer MoTe 2 , by(More)
2 is the permittivity of free space, ε c is the complex relative permittivity, σ is the optical conductivity, and ω is the angular frequency of the incident monochromatic optical field. " should read: " Here, H and E are the magnetic and electric fields, respectively, ε 0 is the permittivity of free space, ε c = (n − ik) 2 is the complex relative(More)