A new chain structure of Au is found on stepped Si(111) which exhibits a 1/4-filled band and a pair of > or =1/2-filled bands with a combined filling of 4/3. Band dispersions and Fermi surfaces for Si(553)-Au are obtained by photoemission and compared to that of Si(557)-Au. The dimensionality of both systems is determined using a tight binding fit. The fractional band filling makes it possible to preserve metallicity in the presence of strong correlations.

Germanium‐based alloys hold great promise for future spintronics applications, due to their potential for integration with conventional Si‐based electronics. High‐quality single phase Mn5Ge3(0001) films, grown by solid‐phase epitaxy on Ge(111) and GaAs(111), exhibit strong ferromagnetism up to the Curie temperature TC ∼ 296 K. Point Contact Andreev Reflection (PCAR) measurements on Mn5Ge3 epilayers reveal a spin‐polarization P = 42 ± 5% for both substrates. We also calculate the spin polarization of bulk Mn5Ge3 in the diffusive and ballistic regimes using density‐functional theory (DFT). The measured spin polarization exceeds the theoretical estimates of PDFT = 35 ± 5% and 10 ± 5% for the diffusive and ballistic limits, respectively. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

We investigate theoretically the spin-polarized electron transport through a complex organic molecule coupled to magnetic contacts. Our focus is on how low-energy deformations of the molecule affect the current-voltage characteristics and the magnetotransport of this molecular-scale device. We find that fairly modest deformations, costing only a few tens of meVs, can substantially change the tunneling current-by factors of 2 or more. Such deformations have still larger impact on the magnetoresistance, with small changes in molecular conformation even leading to changes in the sign of the magnetoresistance.

We report the epitaxial growth of CryGe1−y and CryMnxGe1−x−y(001) thin films on GaAs(001), describe the structural and transport properties, and compare the measured magnetic properties with those predicted by theory. The samples are strongly p type, and hole densities increase with Cr concentration. The CryGe1−y system remains paramagnetic for the growth conditions and low Cr concentrations employed (y⩽0.04), consistent with density functional theory predictions. Addition of Cr into the ferromagnetic semiconductor MnxGe1−x host systematically reduces the Curie temperature and total magnetization.

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The basic chemical structure and orientation of ethylene chemisorbed on Si(114)-(2×1) at submonolayer coverage is characterized in ultrahigh vacuum using transmission Fourier transform infrared (FTIR) spectroscopy. The spectra are consistent with di-sigma bonding of ethylene to the surface with a preferential molecular orientation over macroscopic lengths. These results are supported by density functional theory (DFT) calculations of vibrational frequencies for optimized ethylene-Si(114) structures occupying the dimer and rebonded atom surface sites. A detailed analysis of the strong angular and polarization dependence of the C-H stretching mode intensities is also consistent with the adsorption structures identified by DFT, indicating that ethylene chemisorbs with the C-C bond axis parallel to the structural rows oriented along the [1 h10] direction on the Si(114)-(2×1) surface. The results indicate that the unique structure of this surface makes it an excellent template for elucidating relationships between surface structure and organic reaction mechanisms on silicon.

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