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.

No abstract

No abstract

The characterization of thermal and elastic properties at the nanometer length scale is fundamental for the implementation of materials in nanotechnology. Here, we show how four-wave mixing of extreme ultraviolet ultrashort pulses allows for high-precision measurements of nanoscale elasticity in thin suspended silicon nitride membranes through the generation and detection of Lamb waves at 10's of nm wavelengths. Our approach is contact-free and nondestructive, and it provides an estimate of both shear and longitudinal elastic moduli, without the need of nanopatterning. The data provide important information on nanoscale thermal transport and reveal a heat carrier behavior compatible with the diffusive regime. By controlling the fluence of the free-electron laser excitation pulses, we study the dependence of elastic moduli and the thermal relaxation rate on the sample temperature, which increases by hundreds of kelvins due to radiation absorption. At the same time, the experimental data allow us to estimate the characteristic time of phonon attenuation. The capability of determining this parameter, as well as the elastic moduli, at nanoscale wavelengths is a key aspect for the fundamental understanding of solids without translational invariance.

Ultrafast control of magnetization on the nanometer length scale, in particular all-optical switching, is key to putting ultrafast magnetism on the path toward future technological application in data storage technology. However, magnetization manipulation with light on this length scale is challenging due to the wavelength limitations of optical radiation. Here, we excite transient magnetic gratings in a GdFe alloy with a periodicity of 87 nm by the interference of two coherent femtosecond light pulses in the extreme ultraviolet spectral range. The subsequent ultrafast evolution of the magnetization pattern is probed by diffraction of a third, time-delayed pulse tuned to the Gd N-edge at a wavelength of 8.3 nm. By examining the simultaneously recorded first and second order diffractions and by performing reference real-space measurements with a wide-field magneto-optical microscope with femtosecond time resolution, we can conclusively demonstrate the ultrafast emergence of all-optical switching on the nanometer length scale.