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)
It has been proposed that the Si(557)-Au surface exhibits spin-charge separation in a one-dimensional electron liquid. Two narrowly spaced bands are found which exhibit a well-defined splitting at the Fermi level. That is incompatible with the assignment to a spinon-holon pair in a Luttinger liquid. Instead, we propose that the two bands are associated with(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)
Polarization-dependent near edge X-ray absorption fine structure (NEXAFS) spectroscopy was used to determine the ordering of octadecyltrichlorosilane (OTS) molecules in self-assembled (SA) films on Si/SiOx. Coverages of adsorbed material for different SA films were determined by integration of the NEXAFS signal due entirely to the C 1s absorption. 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)
Highly regular arrays of steps are produced on vicinal Si(111)7ϫ7 surfaces. A tilt of the surface normal from ͑111͒ toward ͑1 ¯ 1 ¯ 2͒ produces single steps ͑0.3 nm high and typically 15 nm apart͒. The opposite tilt toward ͑1 1 2 ¯ ͒ produces bunched steps with adjustable height ͑1–5 nm͒ and a spacing of 70 nm. Preparation criteria for straight edges and(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)