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Nanotechnology ; 30(2): 02LT01, 2019 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-30411716


Negative transconductance (NTC) refers to the phenomenon of the N-shape transfer characteristic appearing with a current peak and valley. It has been extensively studied in the past few decades due to its applications in logic and memory devices. Here, we observe unique antibipolar transfer characteristics and NTC behavior in multi-layer 2,6-diphenyl anthracene organic thin-film transistors grown on h-BN, which is due to the vertical potential barrier between the charge accumulation region near the substrate and the neutral bulk region under the contacts. The applied extrinsic electric field could effectively modulate the barrier height, resulting in a competition for charge carrier transport between lateral and vertical directions. Based on the NTC and antibipolar properties, a frequency doubler has been fabricated on a single transistor, which provides a new building block for organic logic circuits.

Nanotechnology ; 30(3): 034004, 2019 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-30452391


Phase transition from the semiconducting hexagonal (2H) phase to the metallic monoclinic (1T') phase in two-dimensional (2D) transition metal dichalcogenides like MoTe2 is not only of great importance in fundamental study but also of technological significance for broad device applications. Here we report a universal, facile, scalable and reversible phase engineering technique (between 2H and 1T' phases) for both monolayer and few-layer MoTe2 based on a soft hydrogen plasma treatment. The 2H â†’ 1T' transition was confirmed by a series of characterizations including Raman spectra and mapping studies, XPS analysis and FET device measurements at varying temperatures. We attribute the phase transition to the warping of Te-Mo bonds and the lateral sliding of the top Te-layer induced by the soft hydrogen ion bombardment according to both the structural and electronic characterizations as well as the horizontal comparison with the cases of Ar or O2 plasma treatment. We have also prepared a 2D heterostructure containing periodical 2H and 1T' MoTe2 and showed that such phase transition can be readily reversed by post annealing. These results thus provide a robust and efficient approach for the phase engineering of monolayer and few-layer MoTe2 and could aid the development of 2D optoelectronic, memory and reconfigurable devices.