Single-molecule-resolved structural changes induced by temperature and light in surface-bound organometallic molecules designed for energy storage.

We have used scanning tunneling microscopy, Auger electron spectroscopy, and density functional theory calculations to investigate thermal and photoinduced structural transitions in (fulvalene)tetracarbonyldiruthenium molecules (designed for light energy storage) on a Au(111) surface. We find that both the parent complex and the photoisomer exhibit striking thermally induced structural phase changes on Au(111), which we attribute to the loss of carbonyl ligands from the organometallic molecules. Density functional theory calculations support this conclusion.

Functionalization, self-assembly, and photoswitching quenching for azobenzene derivatives adsorbed on Au(111).

We have used scanning tunneling microscopy to investigate the structure and photoswitching behavior of azobenzene molecules functionalized with bulky spacer groups and adsorbed onto Au(111). We find that positioning tert-butyl "legs" in a canted arrangement on the azobenzene phenyl rings quenches photoisomerizability of the molecule on Au(111). Addition of cyano groups at the para positions changes the molecular self-assembly significantly, but does not alter the quenched photoisomerizability.

Magnetization reversal of nanoscale islands: how size and shape affect the arrhenius prefactor.

The thermal switching behavior of individual in-plane magnetized Fe/W(110) nanoislands is investigated by a combined study of variable-temperature spin-polarized scanning tunneling microscopy and Monte Carlo simulations. Even for islands consisting of less than 100 atoms the magnetization reversal takes place via nucleation and propagation. The Arrhenius prefactor is found to strongly depend on the individual island size and shape, and based on the experimental results a simple model is developed to describe the magnetization reversal in terms of metastable states.

Self-patterned molecular photoswitching in nanoscale surface assemblies.

Photomechanical switching (photoisomerization) of molecules at a surface is found to strongly depend on molecule-molecule interactions and molecule-surface orientation. Scanning tunneling microscopy was used to image photoswitching behavior in the single-molecule limit of tetra-tert-butyl-azobenzene molecules adsorbed onto Au(111) at 30 K. Photoswitching behavior varied strongly with surface molecular island structure, and self-patterned stripes of switching and nonswitching regions were observed having approximately 10 nm pitch.