We present a study on the growth and characterization of high-quality single-layer MoS 2 with a single orientation, i.e. without the presence of mirror domains. This single orientation of the MoS 2 layer is established by means of x-ray photoelectron diffraction. The high quality is evidenced by combining scanning tunneling microscopy with x-ray photoelectron spectroscopy measurements.Spin-and angle-resolved photoemission experiments performed on the sample revealed complete spin-polarization of the valence band states near the K and -K points of the Brillouin zone. These findings open up the possibility to exploit the spin and valley degrees of freedom for encoding and processing information in devices that are based on epitaxially grown materials.
VS 2 is a challenging material to prepare stoichiometrically in the bulk, and the single layer has not been successfully isolated before now. Here we report the first realization of single-layer VS 2 , which we have prepared epitaxially with high quality on Au(111) in the octahedral (1T) structure. We find that we can deplete the VS 2 lattice of S by annealing in vacuum so as to create an entirely new twodimensional compound that has no bulk analogue. The transition is reversible upon annealing in an H 2 S gas atmosphere. We report the structural properties of both the stoichiometric and S-depleted compounds on the basis of low-energy electron diffraction, X-ray photoelectron spectroscopy and diffraction, and scanning tunneling microscopy experiments.
We present a complete characterization at the nanoscale of the growth and structure of singlelayer tungsten disulfide (WS 2 ) epitaxially grown on Au(111). Following the growth process in real time with fast x-ray photoelectron spectroscopy, we obtain a singly-oriented layer by choosing the proper W evaporation rate and substrate temperature during the growth. Information about the morphology, size and layer stacking of the WS 2 layer were achieved by employing x-ray photoelectron diffraction and low-energy electron microscopy. The strong spin splitting in the valence band of WS 2 coupled with the single-orientation character of the layer make this material the ideal candidate for the exploitation of the spin and valley degrees of freedom.
This paper presents a new model for the surface roughness (SR) limited mobility in MOS transistors. The model is suitable for bulk and thin body devices and explicitly takes into account the non linear relation between the displacement of the interface position and the SR scattering matrix elements, which is found to significantly influence the r.m.s value of the interface roughness that is necessary to reproduce SR-limited mobility measurements. In particular, comparison with experimental mobility for bulk Si MOSFETs shows that with the new SR scattering model a good agreement with measured mobility can be obtained with r.m.s. values of about 0.2 nm, which is in good agreement with several AFM and TEM measurements. For thin body III–V MOSFETs, the proposed model predicts a weaker mobility degradation at small well thicknesses (Tw), compared to the Tw^6 behavior observed in Si extremely thin body device
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