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Currently, 2D layered material (2DLM) based heterostructures, also known as van der Waals (vdW) heterostructures, are actively pursued owing to their great potential for optoelectronic applications. They are produced either by vertical stacking of individual layers or via in-plane stitching of 2DLMs. Producing vdW heterostructures with clean interfaces and growing them using direct growth methods are challenging. Herein, we report successful growth of large-area MoS2–WS2 vdW heterostructures (single- to few-monolayer, ML, the thickness of MoS2 and WS2) on oxidized Si (100) substrates using the catalyst-free Pulsed Laser Deposition technique. The in-plane (E12g) and out-of-plane (A1g) Raman-active phonon modes are used to probe the interlayer interactions between the constituent 2D layers. We observe a blueshift of 4.73 (1.63) cm−1 of the A1g peak corresponding to MoS2 (WS2) in the MoS2(1ML)–WS2(1ML) heterostructure compared to 1.27 (0.88) cm−1 for the homo-bilayers. The E12g mode also exhibited blueshift for the heterostructure and redshift for the bilayer of the constituent material. We show that the broadband photodetectors fabricated utilizing in situ grown MoS2–WS2 heterostructures exhibit responsivity, specific detectivity, and current on/off ratio as high as 2.51 × 105 A/W, 4.20 × 1014 Jones, and 1.05 × 105, respectively, under 24 μW/cm2 at 405 nm excitation. The successful fabrication of vdW heterostructures using a simple and scalable direct growth method and excellent photodetector performance pave the way for exploitation of their application potential and offer a playground to test some of the theoretical predictions. [ABSTRACT FROM AUTHOR]

A new two-step technique was developed to fabricate a composite probe for a Scanning Tunneling Microscopy (STM). The first step was to form a flat area on the W(100) surface of several hundred square nanometers or less in an area at the end of a single crystalline tungsten tip. The second step consisted of epitaxial growth of a nanoparticle on this flat area by molecular beam epitaxy. Both atomic resolution imaging on the MoO2/Mo(110) surface covered with Fe nanoclusters and magnetic contrast on Fe nanoclusters were obtained at T=78K as an indication of an excellent performance and stability of the composite STM probe. The developed technique of composite probes formation is very promising for the fabrication of probes with the required physical characteristics. [ABSTRACT FROM AUTHOR]

We studied Fe3O4 (110) films grown epitaxially on MgO (110) substrates using oxygen plasma assisted molecular beam epitaxy. The films with thickness of 30-200 nm showed anisotropic in-plane partial strain relaxation. Magneto resistance (MR) measurements with current and magnetic field along h001i direction showed higher MR compared to 〈1̄10〉 direction. Maximum value of MR was measured at Verwey transition temperature for both directions. We explain the observed anisotropy in the MR on the basis of the effects of anisotropic misfit strain, and the difference between the density of antiferromagnetically coupled antiphase boundaries formed along 〈001〉 and 〈1̄10〉 crystallographic directions, suggesting the dependence of spin polarisation on the anisotropic strain relaxation along the said crystallographic directions. [ABSTRACT FROM AUTHOR]

Linear polarization angle, h, dependent measurements of the microwave radiation-induced oscillatory magnetoresistance, Rxx, in high mobility GaAs/AlGaAs 2D electron devices have shown a ϑ dependence in the oscillatory amplitude along with magnetic field, frequency, and extrema-dependent phase shifts, ϑ0. Here, we suggest a microwave frequency dependence of ϑ0(f) using an analysis that averages over other smaller contributions, when those contributions are smaller than estimates of the experimental uncertainty. [ABSTRACT FROM AUTHOR]

The precessional magnetization dynamics of high quality epitaxial magnetite (Fe3O4) thin films growth on MgO are investigated by inductive magnetization dynamic measurements in time and frequency domain. An upper bound for the intrinsic Gilbert damping parameter of α0=0.037±0.001 is derived, which is significantly lower than previously reported for epitaxial Fe3O4 on GaAs. With increasing film thickness from 5 up to 100 nm a strong increase in the effective damping up to 0.2 is observed which cannot be explained by simple nonuniform spin wave excitations. Possible origins of this effect are discussed. [ABSTRACT FROM AUTHOR]

Based on the group velocity concept, we investigated the traversal time of a quasi-one-dimensional waveguide that contains the ferromagnetic/semiconductor/ferromagnetic heterojunction in the presence of the Rashba spin-orbit interaction. The significant quantum size, quantum coherence, and Rashba spin-orbit interaction are considered simultaneously. The results indicate that as the strength of the spin-orbit coupling increases, the traversal time considerably decreases. The results also indicate that the traversal time is not prolonged linearly as the length of the semiconductor increases but shows step-like behavior. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

X-ray magnetic circular dichroism (XMCD) is used for studying the epitaxial magnetite ([Fe.sub.3][O.sub.4]) films on MgO (001) and [Al.sub.2][O.sub.3] (0001) substrates. The differences observed between film grown on MgO and [Al.sub.2][O.sub.3] are described within the framework of differences in mismatch strain experienced by the films.