Scanning tunneling spectroscopy of one-dimensional surface states on a metal surface

Observation of the Magnetization Reorientation in Self-Assembled Metallic Fe-Silicide Nanowires at Room Temperature by Spin-Polarized Scanning Tunneling Spectromicroscopy

The quasi-periodic magnetic domains in metallic Fe-silicide nanowires self-assembled on the Si(110)-16 × 2 surface have been observed at room temperature by direct imaging of both the topographic and magnetic structures using spin-polarized scanning tunneling microscopy/spectroscopy. The spin-polarized differential conductance (dI/dV) map of the rectangular-sectional Fe-silicide nanowire with a width and height larger than 36 and 4 nm, respectively, clearly shows an array of almost parallel streak domains that alternate an enhanced (reduced) density of states over in-plane (out-of-plane) magnetized domains with a magnetic period of 5.0 ± 1.0 nm. This heterostructure of magnetic Fe-silicide nanowires epitaxially integrated with the Si(110)-16 × 2 surface will have a significant impact on the development of Si-based spintronic nanodevices.

LOCAL ELECTRONIC PROPERTIES OF DOMAIN BOUNDARIES ON c(2 × 2) Fe(001) THIN FILM SURFACES

Scanning tunneling microscopy (STM) and spectroscopy have been performed on a nanostructure "line-like pattern" appearing on atomically flat terraces of bcc-Fe (001) with a c(2 × 2) reconstructed structure. Atomically resolved STM reveals that the line-like pattern consists of regularly aligned surface atoms that have a similar symmetry to the (1 × 1) structure of Fe (001). The line-like pattern plays a role of domain boundaries of c(2 × 2) domains. The patterns exhibit bias-voltage dependent image contrast in the STM topographic images. In negative sample bias-voltage range the patterns appear lower than the c(2 × 2) domains and higher in positive range. In dI/dV tunneling spectra taken on the patterns a shoulder is observed around +0.2 V. On the other hands, a small salient is distinguished around +0.4 V in the spectra taken on the c(2 × 2) domains. These features are originated from surface states existing on bcc-Fe (001) surfaces with (1 × 1) structure and c(2 × 2) reconstructed structure, respectively. Emergence of the line-like patterns results in the difference of tunneling conductance.

Local atomic structures of palladium nanowire

In this paper, investigation of the structure of palladium nanowire has been performed by using genetic algorithm simulation based on the molecular dynamics. Our calculation employs a well-fitted, tight-binding many-body potential for Pd atoms. Some local atomic structures and defects in nanowires have been reported. The melting behavior of palladium nanowire has also been investigated. An interesting result is that the diffusion of the central atoms results in the beginning of the melting. The moving central atoms build up a monostrand atomic chain during the melting process. The single atomic chain is very stable which can exist in a wide temperature region (800-950 K). The formation of the single atomic chain causes some new defects in the nanowire. And the new defects result in the decrease of the thermal stability of the nanowire. Interestingly, the liquid from the nanowire melting has a supercooled feature because the splitting of the second peak of pair correlation function is observed. The curves of the internal energy and the local cluster are used to monitor the phase transition. The melting of the nanowire is not only due to the single atomic diffusion, but also the diffusion of the local clusters.

Influence of impurities on localized transition metal surface states: scanning tunneling spectroscopy on V(001)

The first scanning tunneling spectroscopy measurements on V(001) are reported. A strong surface state is detected which is very sensitive to the presence of segregated carbon impurities. The surface state energy shifts from 0.03 eV below the Fermi level at clean areas towards higher energies (up to approximately 0.2 eV) at contaminated areas. Because of the negative dispersion of this state, the upward shift cannot be described in a simple confinement picture. Rather, the surface state energy is governed by vanadium surface s- d interactions which are altered by carbon coverage.