Gil‐Ho Kim

Carbon nanotubes (CNTs), either single wall carbon nanotubes (SWNTs) or multiwall carbon nanotubes (MWNTs), can improve the thermoelectric properties of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT : PSS), but it requires addition of 30-40 wt% CNTs. We report that the figure of merit (ZT) value of PEDOT : PSS thin film for thermoelectric property is increased about 10 times by incorporating 2 wt% of graphene. PEDOT : PSS thin films containing 1, 2, 3 wt% graphene are prepared b

Molybdenum disulfide (MoS₂) based field effect transistors (FETs) are of considerable interest in electronic and opto-electronic applications but often have large hysteresis and threshold voltage instabilities. In this study, by using advanced transfer techniques, hexagonal boron nitride (hBN) encapsulated FETs based on a single, homogeneous and atomic-thin MoS₂ flake are fabricated on hBN and SiO₂ substrates. This allows for a better and a precise comparison bet

Two-dimensional transition metal dichalcogenides (TMDCs) have emerged as promising materials for next-generation electronics due to their excellent semiconducting properties. However, high contact resistance at the metal-TMDC interface plagues the realization of high-performance devices. Here, an effective metal-interlayer-semiconductor (MIS) contact is demonstrated, wherein an ultrathin ZnO interlayer is inserted between the metal electrode and MoS₂, providing damage-free and clean i

An ambipolar dual-channel field-effect transistor (FET) with a WSe₂ /MoS₂ heterostructure formed by separately controlled individual channel layers is demonstrated. The FET shows a switchable ambipolar behavior with independent carrier transport of electrons and holes in the individual layers of MoS₂ and WSe₂ , respectively. Moreover, the photoresponse is studied at the heterointerface of the WSe₂ /MoS₂ dual-channel FET.

Transition metal dichalcogenides (TMDs) are of great interest owing to their unique properties. However, TMD materials face two major challenges that limit their practical applications: contact resistance and surface contamination. Herein, a strategy to overcome these problems by inserting a monolayer of hexagonal boron nitride (h-BN) at the chromium (Cr) and tungsten disulfide (WS₂ ) interface is introduced. Electrical behaviors of direct metal-semiconductor (MS) and metal-insulator-

HfSe₂ field effect transistors are systematically studied in order to selectively tune their electrical properties by optimizing layer thickness and oxygen plasma treatment. The optimized plasma-treated HfSe₂ field effect transistors showed a high on/off ratio improvement of four orders of magnitude, from 27 to 10⁵, a field effect mobility increase from 2.16 to 3.04 cm² V^-1 s^-1, a subthreshold swing improvement from 30.6 to 4.8 V

We studied insulator-metal transitions in VO2 nanobeams for both abrupt and gradual changes in applied electric fields. Based on the observations, the Poole-Frenkel effect explained the abrupt transition, while the gradual case is found to be dominated by the Joule heating phenomenon. We also carried out power model and finite element method based simulations which supported the Joule heating phenomena for gradual transition. An in-principle demonstration of the Poole-Frenkel effect, performed u

We report a facile and highly effective n-doping method using hydrazine solution to realize enhanced electron conduction in a WSe2 field-effect transistor (FET) with three different metal contacts of varying work functions-namely, Ti, Co, and Pt. Before hydrazine treatment, the Ti- and Co-contacted WSe2 FETs show weak ambipolar behaviour with electron dominant transport, whereas in the Pt-contacted WSe2 FETs, the p-type unipolar behaviour was observed with the transport dominated by holes. In th

Low-noise thermoelectric and electrical measurements were used to derive the dependences of Seebeck coefficient and hole mobility on carrier concentration and grain size in the “bulk” regions of thermally evaporated pentacene thin films (in contrast to the channel field-effect mobility typically measured using thin-film transistor geometries). Distinct charge transport regimes were observed for larger (0.5 and 0.8 μm) and smaller (0.2 μm) grain sizes, attributed to carrier-dopant scattering and

We present a study of the transport properties of two-dimensional electron gases formed in GaAs/AlGaAs heterostructures in which InAs self-assembled quantum dots have been inserted in the center of a GaAs quantum well. We observed that, while maintaining a constant carrier density, the mobility increased as the InAs dot density was reduced. The ratio of the transport to the quantum lifetime was measured to be approximately five with the dominant scattering mechanism attributed to short-range sca