Highly conductive nanometer-thick gold films grown on molybdenum disulfide surfaces for interconnect applications.

Thin gold (Au) films (10 nm) are deposited on different substrates by using a e-beam deposition system. Compared with sapphire and SiO surfaces, longer migration length of the Au adatoms is observed on MoS surfaces, which helps in the formation of a single-crystal Au film on the MoS surface at 200 °C. The results have demonstrated that with the assistance of van der Waals epitaxy growth mode, single-crystal 3D metals can be grown on 2D material surfaces.

Current Enhancement and Bipolar Current Modulation of Top-Gate Transistors Based on Monolayer MoS on Three-Layer W MoS.

We demonstrated the top-gate transistors composed of monolayer MoS grown on three-layer alloys Mo WS prepared by sequential sulfurization of predeposited transition metal films. The elemental mapping of the alloy indicates a uniform distribution of both cations Mo and W in the grown samples. Surprisingly, we find that the drain current of transistors could be enhanced by 2 orders of magnitude as the composition of Mo increases, whereas the gate-controlled current modulation turns bipolar and ultimately vanishes.

Preparation of Large-area Vertical 2D Crystal Hetero-structures Through the Sulfurization of Transition Metal Films for Device Fabrication.

We have demonstrated that through the sulfurization of transition metal films such as molybdenum (Mo) and tungsten (W), large-area and uniform transition metal dichalcogenides (TMDs) MoS2 and WS2 can be prepared on sapphire substrates. By controlling the metal film thicknesses, good layer number controllability, down to a single layer of TMDs, can be obtained using this growth technique. Based on the results obtained from the Mo film sulfurized under the sulfur deficient condition, there are two mechanisms of (a) planar MoS2 growth and (b) Mo oxide segregation observed during the sulfurization procedure.

Effect of Focused Ion Beam Imaging on the Crystallinity of InAs.

We investigated the effect of focused ion beam (FIB) imaging on the crystallinity of InAs using Raman scattering. A spatial correlation model was used to fit the broad band induced by FIB imaging. The fitting gives a correlation length of ~42 Å for the noisiest image condition (with an ion fluence of 7.