We report on the first demonstration of p-type doping in large area few-layer films of (0001)-oriented chemical vapor deposited (CVD) MoS 2 . Niobium was found to act as an efficient acceptor up to relatively high density in MoS 2 films. For a hole density of 4 x 10 20 cm -3Hall mobility of 8.5 cm 2 V -1 s -1 was determined, which matches well with the theoretically expected values. XRD and Raman characterization indicate that the film had good out-of-plane crystalline quality. Absorption measurements showed that the doped sample had similar characteristics to high-quality undoped samples, with a clear absorption edge at 1.8 eV. This demonstration of p-doping in large area epitaxial MoS 2 could help in realizing a wide variety of electrical and opto-electronic devices based on layered metal dichalcogenides.

We report on the vapor-solid growth of single crystalline few-layer MoS2 films on (0001)-oriented sapphire with excellent structural and electrical properties over centimeter length scale. Highresolution X-ray diffraction scans indicated that the films had good out-of-plane ordering and epitaxial registry. A carrier density of ~2 x 10 11 cm -2 and a room temperature mobility of 192 cm 2 /Vs were extracted from space-charge limited transport regime in the films. The electron mobility was found to exhibit in-plane anisotropy with a ratio of ~ 1.8. Theoretical estimates of the temperature-dependent electron mobility including optical phonon, acoustic deformation potential and remote ionized impurity scattering were found to satisfactorily match the measured data. The synthesis approach reported here demonstrates the feasibility of device quality few-layer MoS2 films with excellent uniformity and high quality.

KEYWORDSMoS 2 , tunnel diode, GaN, 2D/3D heterojunction, interband tunneling.

Electrical and optical characterization of two-dimensional/three-dimensional (2D/3D) pmolybdenum disulfide/n-gallium nitride (p-MoS 2 /n-GaN) heterojunction diodes are reported.Devices were fabricated on high-quality, large-area p-MoS 2 grown by chemical vapor deposition (CVD) on hexagonal sapphire substrates. The processed devices were transferred onto GaN/sapphire substrates, and the transferred films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). On-axis XRD spectra and surface topology

The growth and electrical characterization of the heterojunction formed between two-dimensional (2D) layered p-molybdenum disulfide (MoS 2 ) and nitrogen-doped 4H silicon carbide (SiC) are reported. The integration of 2D semiconductors with the conventional three-dimensional (3D) substrates could enable semiconductor heterostructures with unprecedented properties. In this work, direct growth of p-type MoS 2 films on SiC was demonstrated using chemical vapor deposition, and the MoS 2 films were found to be high quality based on x-ray diffraction and Raman spectra. The resulting heterojunction was found to display rectification and current-voltage characteristics consistent with a diode for which forward conduction in the low-bias region is dominated by multistep recombination tunneling. Capacitance-voltage measurements were used to determine the built-in voltage for the p-MoS 2 /n-SiC heterojunction diode, and we propose an energy band line up for the heterostructure based on these observations. The demonstration of heterogeneous material integration between MoS 2 and SiC enables a promising new class of 2D/3D heterostructures. V C 2014 AIP Publishing LLC. [http://dx.

We have investigated the intracellular roles of an Xklp2-related kinesin motor, KRP180, in positioning spindle poles during early sea urchin embryonic cell division using quantitative, real-time analysis. Immunolocalization reveals that KRP180 concentrates on microtubules in the central spindle, but is absent from centrosomes. Microinjection of inhibitory antibodies and dominant negative constructs suggest that KRP180 is not required for the initial separation of spindle poles, but instead functions to transiently position spindle poles specifically during prometaphase.

Transfer of epitaxial, two-dimensional (2D) MoS2 on sapphire grown via synthetic approaches is a prerequisite for practical device applications. We report centimeter-scale, single crystal, synthesized MoS2 field effect transistors (FETs) transferred onto SiO2/Si substrates, with a field-effect mobility of 4.5 cm2 V−1 s−1, which is among the highest mobility values reported for the transferred large-area MoS2 transistors. We demonstrate simple and clean transfer of large-area MoS2 films using deionized water, which can effectively avoid chemical contamination. The transfer method reported here allows standard i-line stepper lithography process to realize multiple devices over the entire film area.

We report controlled layer-by-layer removal of large-area, sulfurized, single-crystal molybdenum disulfide (MoS 2) films using a digital etching technique, which utilizes oxidation and removal of the oxidized layer. We demonstrate a self-limiting oxidation process where Mo oxide covered the surface of MoS 2. A constant etching rate of one monolayer/cycle and the uniformity of the etching process were also verified. We show that the etching of an integer number of MoS 2 layers can be precisely controlled. No noticeable film quality degradation was observed after multiple cycles of digital etching, as confirmed by Raman mapping of the ratio of the E 1 2g and A 1g peak intensities.