Franz J. Himpsel

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The limits of pushing storage density to the atomic scale are explored with a memory that stores a bit by the presence or absence of one silicon atom. These atoms are positioned at lattice sites along self-assembled tracks with a pitch of five atom rows. The memory can be initialized and reformatted by controlled deposition of silicon. The writing process(More)
Gold atom chains on vicinal Si(111) surfaces exhibit an unusual doublet of half-filled bands, whose origin has remained uncertain. The splitting is identified by angle-resolved photoemission as a spin splitting induced by the spin-orbit interaction (Rashba effect), in agreement with a theoretical prediction by Sánchez-Portal, Riikonen, and Martin. This(More)
A vicinal surface of silicon is found that exhibits an atomically accurate step pattern with a period of 5.73 nm, corresponding to 17 atomic rows per ͑111͒ terrace. It can be viewed as reconstructed Si͑557͒ surface, where a triple step is combined with a single Si͑111͒7ϫ7 unit. The driving forces for establishing regular step patterns are discussed.(More)
Highly regular arrays of steps are produced on vicinal Si͑111͒7ϫ7. The step edges are atomically straight for up to 2ϫ10 4 lattice sites. The terraces are single domain, which produces a minimum kink width of 2.3 nm ͑half a 7ϫ7 unit cell͒ and thus a high barrier for creating kinks. Criteria for obtaining optimum step arrays are established, such as the(More)
The photodissociation of the amide bond by UV light and soft x-rays is investigated by x-ray absorption spectroscopy at the C, N, and O 1s edges. Irradiation leaves a clear and universal signature for a wide variety of amides, ranging from oligopeptides to large proteins and synthetic polyamides, such as nylon. As the π∗ peak of the amide bond shrinks, two(More)
We demonstrate a self-organized pattern formation on vicinal Si(111) surfaces that are miscut toward the [2;11] direction. All the patterns, consisting of a periodic array of alternating (7 x 7) reconstructed terraces and step-bunched facets, have the same periodicity and facet structure, independent of the miscut angle, while the width of the facets(More)
In recent years, it has become possible to create well-ordered semiconductor surfaces with metallic surface states by using self-assembly of metal atoms. Since these states lie in the band gap of the semiconductor, they completely decouple from the substrate. In addition to two-dimensional structures it is possible to obtain arrays of one-dimensional atomic(More)
Ribonuclease A (RNase A) is immobilized on silver surfaces in oriented and random form via self-assembled monolayers (SAMs) of alkanethiols. The immobilization process is characterized step-by-step using chemically selective near-edge X-ray absorption fine structure spectroscopy (NEXAFS) at the C, N, and S K-edges. Causes of imperfect immobilization are(More)
The pathway for thermal decomposition of an oleic acid surfactant protecting Co and Ni nanocrystals is identified by probing the relevant molecular orbitals with x-ray absorption spectroscopy. The two steps observed previously in thermogravimetric measurements are identified with thermal desorption of entire molecules at Ϸ200 °C and dehydrogenation at Ϸ400(More)
A one-dimensional 5 Â 2 reconstruction of Gd is observed on Si(1 1 1), which can be stabilized in single domain form on vicinal surfaces. It contains zigzag rows of occupied orbitals alternating with rows of unoccupied orbitals, as inferred from spectroscopic scanning tunneling microscopy. The large magnetic moment of the Gd 4f electrons creates atomic(More)