Vienna University of Technology

About: Vienna University of Technology is a education organization based out in Vienna, Austria. It is known for research contribution in the topics: Laser & Context (language use). The organization has 16723 authors who have published 49341 publications receiving 1302168 citations.

Spin-orbit splitting of the L -gap surface state on Au(111) and Ag(111)

Abstract: We present high-resolution photoemission results on the L-gap surface state on Au(111) and Ag(111), in combination with fully relativistic density-functional calculations. In the case of Au(111), both experimental and theoretical results demonstrate that the lack of inversion symmetry at the surface leads to a considerable spin-orbit splitting of this surface state over the whole Fermi surface, whereas in the case of Ag(111) this splitting is far too small to be experimentally resolved in our data.

High-resolution 3-D direction-of-arrival determination for urban mobile radio

Abstract: The in-depth knowledge of the mobile radio channel is particularly important for radio communication modeling and advanced technology system design. We propose an accurate method to determine jointly the azimuth and elevation angle and the delay of waves incoming at the receiver. The method is applied to measurements of the complex impulse response of the mobile radio channel, performed on a planar array placed on a mobile in an urban cellular environment. The directions-of-arrival (DOA) were obtained by the means of a direction finding algorithm-two-dimensional (2-D) unitary ESPRIT. Two-dimensional spatial smoothing as an extension of ordinary spatial smoothing is utilized to decorrelate coherent waves. The application of 2-D unitary ESPRIT increases the angular resolution over conventional Fourier analysis or the scattering function by an order of magnitude and overcomes difficulties due to secondary lobes. The time delay is determined from wideband channel sounder measurements. The results confirm some assumptions on propagation mechanisms: (1) the wave-guiding property of streets (canyon effect), which is especially pronounced for long-delayed paths; (2) the variation of the number of incoming waves with their excess delay-the larger the excess delay, the lower the number of paths comprising an echo in the power delay profile; (3) if a single path remains, the privileged DOA is the direction of the street; (4) the exponential part of the power delay profile due to scatterers all around the receiver; and (5) the elevation dependence or the impinging power. In the tested receiver locations, paths with elevations between 0/spl deg/ and 40/spl deg/ dominate, containing about 90% of the received power.

Observation of light-phase-sensitive photoemission from a metal

Abstract: We demonstrate that multiphoton-induced photoelectron emission from a gold surface caused by low-energy (unamplified) 4-fs, 750-nm laser pulses is sensitive to the timing of electric field oscillations with respect to the pulse peak. This observation confirms recent theoretical predictions and opens the door to measuring the absolute value of the carrier-envelope phase difference of few-cycle light pulses with a solid-state detector.

Structural and electronic properties of liquid and amorphous SiO2: An ab initio molecular dynamics study.

Abstract: We performed a first-principles molecular dynamics study of liquid ${\mathrm{SiO}}_{2}$ at a temperature of 3500 K, followed by a rapid quench to 300 K obtaining a perfectly chemically ordered amorphous network. Structural and electronic properties of our amorphous sample are in good agreement with neutron diffraction, x-ray photoemission, and optical experiments. On the basis of the partial structure factors, we investigated the origin of the first sharp diffraction peak. Disorder affects differently the localization properties of valence and conduction band states, as suggested by experimental mobilities of electrons and holes.

Deep-ultraviolet solar-blind photoconductivity of individual gallium oxide nanobelts.

Abstract: We designed solar-blind deep-ultraviolet semiconductor photodetectors using individual Ga2O3 nanobelts. The photoconductive behavior was systematically studied. The photodetectors demonstrate high selectivity towards 250 nm light, fast response times of less than 0.3 s, and a large photocurrent to dark current ratio of up to 4 orders of magnitude. The photoresponse parameters such as photocurrent, response time, and quantum efficiency depend strongly on the intensity of light, the detector environment, and the nanobelt size. The photoresponse mechanism was discussed, which was mainly attributed to the band bending, surface traps, and distribution of traps in the bandgap. Present Ga2O3 nanobelts can be exploited for future applications in photo sensing, light-emitting diodes, and optical switches.