Browsing by Author "Yamamoto, Mahito"

Now showing 1 - 2 of 2

Ambipolar MoTe2 Transistors and Their Applications in Logic Circuits
(2014-05-28)
Lin, Yen-Fu
;
Xu, Yong
;
Wang, Sheng-Tsung
;
Li, Song-Lin
;
Yamamoto, Mahito
We report ambipolar charge transport in a-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 ratio could be modified by modulating the electrostatic fields of the back-gate voltage (V-bg) and drain-source voltage (V-ds). Using these ambipolar MoTe2 transistors we fabricated complementary inverters and amplifiers, demonstrating their feasibility for future digital and analog circuit applications.
Strong Enhancement of Raman Scattering from a Bulk-Inactive Vibrational Mode in Few-Layer MoTe2
(2014-04-01)
Yamamoto, Mahito
;
Wang, Sheng Tsung
;
Ni, Meiyan
;
Lin, Yen-Fu
;
Li, Song-Lin
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 alpha-MoTe2 using Raman spectroscopy. The Raman spectrum of alpha-MoTe2 shows a prominent peak of the in-plane E-2g(1) mode, with its frequency upshifting with decreasing thickness down to the atomic scale, similar to other dichalcogenides. Furthermore, we find large enhancement of the Raman scattering from the out-of-plane B-2g(1) mode in the atomically thin layers. The B-2g(1) models Raman inactive in the bulk, but is observed to become active in the few-layer films. The intensity ratio of the B-2g(1) to E-2g(1) peaks evolves significantly with decreasing thickness, in contrast with other dichalcogenides. Our observations point to strong effects of dimensionality on the phonon properties of MoTe2.