Thickness-dependent charge transport in few-layer MoS₂ field-effect transistors

An origin of unintentional doping in transition metal dichalcogenides: the role of hydrogen impurities

We theoretically elucidate the origin of unintentional doping in two-dimensional transition-metal dichalcogenides (TMDs), which has been consistently reported by experiment, but which still remains unclear. Our explanation is based on the charge transfer between TMDs and the underlying SiO₂ in which hydrogen impurities with a negative-U property pin the Fermi level of the SiO₂ as well as adjacent TMD layers. Using first-principles calculations, we obtain the pinning point of the Fermi level from the charge transition level of the hydrogen in the SiO₂, ε(+/-), and align it with respect to the band-edge positions of monolayer TMDs. The computational results show that the Fermi levels of TMDs estimated by ε(+/-) successfully explain the conducting polarity (n- or p-type) and relative doping concentrations of thin TMD films. By enlightening on the microscopic origin of unintentional doping in TMDs, we believe that the present work will contribute to precise control of TMD-based electronic devices.

Design, synthesis and electrocatalytic properties of coaxial and layer-tunable MoS2nanofragments/TiO2nanorod arrays

We present a new concept for the design and preparation of a coaxial structure to increase electrolyte diffusion channels, enhance electron transport, and expose additional active edge sites.