Phototransistors based on multilayer MoS(2) crystals are demonstrated with a wider spectral response and higher photoresponsivity than single-layer MoS(2) phototransistors. Multilayer MoS(2) phototransistors further exhibit high room temperature mobilities (>70 cm(2) V(-1) s(-1) ), near-ideal subthreshold swings (~70 mV decade(-1) ), low operating gate biases (<5 V), and negligible shifts in the threshold voltages during illumination.

Zero-bias anomaly in one-dimensional ultrathin metallic nanowires AIP Advances 2, 032143 (2012) Influence of electron scatterings on thermoelectric effect ZnO nanowires were grown between two Au electrodes on an Al 2 O 3 -deposited Si wafer. Photoresponse, photoresponse spectrum, and current-voltage (I -V) studies were performed for the investigation into photoconduction mechanism in these nanowires. The photoresponse of the nanowires under the continuous illumination of light with above-or below-gap energies was slow, which indicates that photocurrent in the nanowires is surface-related rather than bulk-related. The photoresponse spectrum represents the above-and below-gap absorption bands for the photocurrents. The I -V characteristics under the illumination of the above-gap light are ohmic, but the characteristics under the illumination of the below-gap light are Schottky. This observation indicates that the above-gap light lowers the potential barrier built in the contact between the ZnO nanowires and electrodes, but that the below-gap light does not lower the potential barrier.

ZnO nanorods were grown on SiO2/Si substrates by a sol-gel method at low temperatures of around T=95 °C. The diameters and the lengths of ZnO nanorods increased at high concentrations of zinc nitrate hexahydrate and methenamine solution. Current–voltage characteristics of the ZnO nanorods network followed a typical nonlinear behavior with significant photoresponse below λ&lt;400 nm in air, and the conductance was enhanced in vacuum with negligible photoresponse. In photoluminescence (PL) and photocurrent (PC) spectra, the PL peak (λpeak=380 nm and 3.26 eV) did not match the PC edge (λedge=400 nm and 3.1 eV), indicating the nondirect band-gap transition in photocurrent. The origin of the photocurrent was discussed from the point of the influence of the desorption of adsorbed water molecules on the surface or inside the ZnO nanorods.

Omega-shaped-gate (OSG) nanowire-based field effect transistors (FETs) have attracted a great deal of attention recently, because theoretical simulations predicted that they should have a higher device performance than nanowire-based FETs with other gate geometries. OSG FETs with channels composed of ZnO nanowires were successfully fabricated in this study using photolithographic processes. In the OSG FETs fabricated on oxidized Si substrates, the channels composed of ZnO nanowires with diameters of about 110 nm are coated with Al(2)O(3) using atomic layer deposition, which surrounds the channels and acts as a gate dielectric. About 80% of the surfaces of the nanowires coated with Al(2)O(3) are covered with the gate metal to form OSG FETs. A representative OSG FET fabricated in this study exhibits a mobility of 30.2 cm(2)/ (V s), a peak transconductance of 0.4 muS (V(g) = -2.2 V), and an I(on)/I(off) ratio of 10(7). To the best of our knowledge, the value of the I(on)/I(off) ratio obtained from this OSG FET is higher than that of any of the previously reported nanowire-based FETs. Its mobility, peak transconductance, and I(on)/I(off) ratio are remarkably enhanced by 3.5, 32, and 10(6) times, respectively, compared with a back-gate FET with the same ZnO nanowire channel as utilized in the OSG FET.

Sunkook Kim, Jinsoo Joo, and co‐workers demonstrate phototransistors based on multilayer MoS2 crystals with a wider spectral response and higher photoresponsivity than single‐layer MoS2 phototransistors. These multilayer MoS2 phototransistors also exhibit high room‐temperature mobilities, near‐ideal subthreshold swings, low operating gate biases, and negligible shifts in the threshold voltages during illumination.