Sönke Voss

Experimental observation of a band gap in individual Mn12 molecules on Au(111)

The authors report on the electronic properties of individual molecules of two Mn12 derivatives chemically grafted on the functionalized Au(111) surface studied by means of ultrahigh vacuum scanning tunneling microscopy/spectroscopy at room temperature. Reproducible current-voltage curves were obtained from both Mn12 molecules, showing a well defined wide band gap. In agreement with the tunneling spectroscopy results, the bias voltage variation upon scanning leads to apparent height changes of the Mn12 clusters. The authors discuss these findings in the light of the recent band structure calculations and electronic transport measurements on single Mn12 molecules.

X-ray Photoelectron Spectroscopy- and Surface Plasmon Resonance-Detected Photo Release of Photolabile Protecting Groups from Nucleoside Self-Assembled Monolayers on Gold Surfaces

The formation of self-assembled monolayers (SAMs) on gold by 2-(5-iodo-2-nitrophenyl) propoxycarbonyl (I-NPPOC)-protected thymidine with an attached mercaptohexyl succinate linker and the kinetics of photochemical release of the I-NPPOC group were monitored using X-ray photoelectron spectroscopy (XPS) and surface plasmon resonance (SPR) detection. In the XPS spectra, the iodine peaks allowed for specific and accurate monitoring of the presence and loss of I-NPPOC groups on the surface. In the SPR experiment, the overall signal change on photoillumination is in accord with a theoretical estimation of the density of I-NPPOC groups in a dense monolayer. The kinetics roughly follow a biexponential time dependence with two very different time constants, corresponding to photochemical quantum yields of 0.22 and 0.0032, respectively.

Identification of linker molecules suited for deposition and study of Mn12 single molecule magnets on Au surfaces

The authors report on a scanning tunneling microscopy/spectroscopy investigation of the possibility to influence the assembly of monolayers of Mn12 single molecule magnets on a functionalized Au(111) surface by using flexible linker molecules. The results corroborate the general suitability of the deposition via ligand exchange reaction but, on the other hand, reveal the need for a compromise between conductivity and flexibility of the linker molecules. The results are discussed with respect to previous attempts [A. Naitabdi et al., Adv. Mater. (Weinheim, Ger.) 17, 1612 (2005)] to deposit ordered monolayers of Mn12 molecules on Au(111).

X-Ray Spectroscopic Investigations of Zn

We investigated Zn0.94 Co0.06 O thin films on sapphire (0001) substrates with respect to their structural and magnetic properties. X-ray diffraction shows a c axis oriented growth and no secondary phases within its resolution. A clear improvement of the crystalline quality was obtained by post annealing under vacuum conditions. Further information about the local electronic structure is obtained by X-ray absorption spectroscopy at the Co L 2,3 and the O K edge. Magnetic properties were investigated with a superconducting quantum interference device (SQUID) and by X-ray magnetic circular dichroism at the Co L 2,3 edge. Both techniques yield mainly paramagnetic behavior of the samples. For low temperatures, an additional small ferromagnetic contribution was observed in SQUID measurements. Several possible origins of this ferromagnetic contribution are discussed.

_{0.94}

We report on the electronic properties of Mn12 molecules chemically grafted on the functionalized Au(111) surface studied by means of scanning tunneling microscopy/spectroscopy at room temperature. Reproducible current-voltage curves were obtained from Mn12 molecules showing a large region of low conductance around the Fermi energy. In agreement with the tunneling spectroscopy results the bias voltage variation upon scanning leads to apparent height changes of the Mn12 clusters. We discuss these findings in the light of the recent band structure calculations and electronic transport measurements on single Mn12 molecules.

Co

We investigated Zn0.94 Co0.06 O thin films on sapphire (0001) substrates with respect to their structural and magnetic properties. X-ray diffraction shows a c axis oriented growth and no secondary phases within its resolution. A clear improvement of the crystalline quality was obtained by post annealing under vacuum conditions. Further information about the local electronic structure is obtained by X-ray absorption spectroscopy at the Co L 2,3 and the O K edge. Magnetic properties were investigated with a superconducting quantum interference device (SQUID) and by X-ray magnetic circular dichroism at the Co L 2,3 edge. Both techniques yield mainly paramagnetic behavior of the samples. For low temperatures, an additional small ferromagnetic contribution was observed in SQUID measurements. Several possible origins of this ferromagnetic contribution are discussed.

_{0.06}

We investigated Zn0.94 Co0.06 O thin films on sapphire (0001) substrates with respect to their structural and magnetic properties. X-ray diffraction shows a c axis oriented growth and no secondary phases within its resolution. A clear improvement of the crystalline quality was obtained by post annealing under vacuum conditions. Further information about the local electronic structure is obtained by X-ray absorption spectroscopy at the Co L 2,3 and the O K edge. Magnetic properties were investigated with a superconducting quantum interference device (SQUID) and by X-ray magnetic circular dichroism at the Co L 2,3 edge. Both techniques yield mainly paramagnetic behavior of the samples. For low temperatures, an additional small ferromagnetic contribution was observed in SQUID measurements. Several possible origins of this ferromagnetic contribution are discussed.