Using resonant Raman spectroscopy, the authors report on the alloying effect and localization of electronic states in Zn1−xMgxO (x<0.15) nanostructures with average sizes in the range of 20–150nm. Anomalous intensity enhancement of the second-order longitudinal optical phonon has been observed, which is due to Fröhlich interaction via the localized exciton as the resonant intermediate electronic states. The alloying-induced disorder due to Mg incorporation led to the enhancement of exciton localization as well as the asymmetric broadening of longitudinal optical phonon line shape. The composition in ZnMgO could be determined by the first-order longitudinal optical phonon frequency via a bowinglike quadratic fit. This simple relationship is in perfect match to the modified random-element-isodisplacement model and provides a nondestructive approach to probe the quantitative composition distributions in wurtzite ZnMgO alloy system.

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Energy transport in photosynthetic systems can be tremendously efficient. In particular we study exciton transport in the Fenna-Mathews-Olsen (FMO) complex found in green sulphur bacteria. The exciton dynamics and energy transfer efficiency is dependent upon the interaction with the system environment. Based upon realistic, site-dependent, models of the system-bath coupling, we show that this interaction is highly optimised in the case of FMO. Furthermore we identify two transport pathways and note that one is dominated by coherent dynamics and the other by classical energy dissipation. In particular we note a strong correlation between energy transport efficiency and coherence for exciton transfer from bacteriochlorophyll (BChl) 8 to BChl 4. The existence of two clear pathways and the role played by BChl 4 also challenges assumptions around the coupling of the FMO complex to the reaction centre.

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We review our recent work showing how important the site-to-site variation in coupling between chloroplasts in FMO and their protein scaffold environment is for energy transport in FMO and investigate the role of vibronic modes in this transport.

Using a combination of selective dry etching techniques, surface micro‐machined GaN and ZnO micromechanical structures are demonstrated on silicon‐on‐insulator (SOI) substrates. The dry releasing technique employs a controlled gas phase pulse etching with non‐plasma xenon difluoride (XeF2), which selectively etches the Si overlayer of SOI, thus undercutting the wide bandgap semiconductor material on top. This method prevents crystal damage of overhanging wide bandgap semiconductor mechanical structures. The mechanical properties of these released microstructures are characterized by micro‐Raman spectroscopy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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