Emergency Radiology of the AbdomenImaging Features and Differential Diagnosis for a Timely Management Approach /

XVII, 277p. 300 illus. in color.online resource

Aktuelle Herausforderungen an die Sozialstaatlichkeit der Bundesrepublik: Symposium an der Fachhochschule Pforzheim 6. Dezember 1995

Available from Bibliothek des Instituts fuer Weltwirtschaft, ZBW, Duesternbrook Weg 120, D-24105 Kiel W 46 (76) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

A direct comparison of CVD-grown and exfoliated MoS2 using optical spectroscopy

MoS2 is a highly interesting material, which exhibits a crossover from an indirect band gap in the bulk crystal to a direct gap for single layers. Here, we perform a direct comparison between large-area MoS2 films grown by chemical vapor deposition (CVD) and MoS2 flakes prepared by mechanical exfoliation from mineral bulk crystal. Raman spectroscopy measurements show differences between the in-plane and out-of-plane phonon mode positions in CVD-grown and exfoliated MoS2. Photoluminescence (PL) mapping reveals large regions in the CVD-grown films that emit strong PL at room-temperature, and low-temperature PL scans demonstrate a large spectral shift of the A exciton emission as a function of position. Polarization-resolved PL measurements under near-resonant excitation conditions show a strong circular polarization of the PL, corresponding to a valley polarizatio

Control of biaxial strain in singel-layer MoS2 using local thermal expansion of the substrate

Single-layer MoS2 is a direct-gap semiconductor whose electronic band structure strongly depends on the strain applied to its crystal lattice. While uniaxial strain can be easily applied in a controlled way, e.g., by bending of a flexible substrate with the atomically thin MoS2 layer on top, experimental realization of biaxial strain is more challenging. Here, we exploit the large mismatch between the thermal expansion coefficients of MoS2 and a silicone-based substrate to apply a controllable biaxial tensile strain by heating the substrate with a focused laser. The effect of this biaxial strain is directly observable in optical spectroscopy as a redshift of the MoS2 photoluminescence. We also demonstrate the potential of this method to engineer more complex strain patterns by employing highly absorptive features on the substrate to achieve non-uniform heat profiles. By comparison of the observed redshift to strain-dependent band structure calculations, we estimate the biaxial strain applied by the silicone-based substrate to be up to 0.2%, corresponding to a band gap modulation of 105 meV per percentage of biaxial tensile strain