Matthias Batzill

Electronic contrast in scanning tunneling microscopy of Sn-Pt( 111) surface alloys

Abstract Scanning tunneling microscopy studies of mixed domain p(2×2) and ( 3 × 3 )R30° tin–platinum surface alloys are presented. It was found that the apparent height of Pt ensembles increases with a decreasing number of Sn next-neighbor atoms per Pt atom. This is explained by a reduction of the local density of states near the Fermi level at Pt sites due to the effects of alloying of Pt with Sn.

Ultrahigh vacuum instrument that combines variable-temperature scanning tunneling microscopy with Fourier transform infrared reflection-absorption spectroscopy for studies of chemical reactions at surfaces

We describe the construction of an ultrahigh vacuum chamber that incorporates variable-temperature scanning tunneling microscopy (STM), Fourier transform infrared reflection-absorption spectroscopy (FT-IRAS), Auger electron spectroscopy, low-energy electron diffraction, and temperature programmed desorption, for studying structure and reactivity at surfaces. The chamber and manipulator design enables in situ sample preparation and analysis, and rapid access to several surface-analytical techniques by rotation only. This eliminates sample inconsistencies due to ex situ preparation or the necessity to run parallel experiments. Inclusion of FT-IRAS allows us to characterize surface species and identify adsorbates during studies using STM.

Self-organized molecular-sized, hexagonally ordered SnOx nanodot superlattices on Pt(111)

Complete oxidation of the (√3×√3)R30° Sn/Pt(111) surface alloy or submonolayer amounts of Sn adatoms on Pt(111) under ultrahigh vacuum conditions, forms a highly ordered, lateral superlattice of SnOx islands on the Pt(111) substrate. The island superstructure exhibits a sharp (5×5) low energy electron diffraction pattern. Scanning tunneling microscopy images show islands arranged in a hexagonal lattice, uniformly distributed over the whole sample. This island array is thermally stable up to 1050 K. The coincidence of the island periodicity with a multiple of the supporting substrate, and the same hexagonal symmetry of islands and substrate, suggests a strong island–substrate interaction. We propose that the island formation results from the breakup of a strained SnOx adlayer.