Karsten Pohl

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In conventional immunoelectron microscopy (IEM), very small colloidal gold particles (0.8-3 nm), or the gold compound Nanogold (1.4 nm) are silver-enhanced for easy detection. However, silver enhancement has drawbacks. First, the silver layer is dissolved during fixation with osmium tetroxide, even if the concentration and incubation time are strongly(More)
A key challenge in thin-film growth is controlling structure and composition at the atomic scale. We have used spatially resolved electron scattering to measure how the three-dimensional composition profile of an alloy film evolves with time at the nanometer length scale. We show that heterogeneity during the growth of Pd on Cu(001) arises naturally from a(More)
We have used in situ low-energy electron microscopy (LEEM) to correlate the atomic and electronic structure of graphene films on polycrystalline Ni with nm-scale spatial resolution. Spatially resolved electron scattering measurements show that graphene monolayers formed by carbon segregation do not support the π-plasmon of graphene, indicating strong(More)
We describe the design and performance of a fast-scanning, variable temperature scanning tunneling microscope (STM) operating from 80 to 700 K in ultrahigh vacuum (UHV), which routinely achieves large scale atomically resolved imaging of compact metallic surfaces. An efficient in-vacuum vibration isolation and cryogenic system allows for no external(More)
We present a combined experimental and theoretical study of the self-assembly of C60 molecules functionalized with long alkane chains on the (111) surface of silver. We find that the conformation of the functionalized C60 changes upon adsorption on Ag(111) and that the unit cell size in the self-assembled monolayer is determined by the interactions between(More)
Nearly two-dimensional (2D) metallic systems formed in charge inversion layers and artificial layered materials permit the existence of low-energy collective excitations, called 2D plasmons, which are not found in a three-dimensional (3D) metal. These excitations have caused considerable interest because their low energy allows them to participate in many(More)
We find that less than 0.01 monolayer of S can enhance surface self-diffusion on Cu(111) by several orders of magnitude. The measured dependence of two-dimensional island decay rates on S coverage (theta(S)) is consistent with the proposal that Cu3S3 clusters are responsible for the enhancement. Unexpectedly, the decay and ripening are diffusion limited(More)
Defining pathways to assemble long-range-ordered 2D nanostructures of specifically designed organic molecules is required in order to optimize the performance of organic thin-film electronic devices. We report on the rapid fabrication of a nearly perfect self-assembled monolayer (SAM) composed of a single-domain 6,13-dichloropentacene (DCP) brick-wall(More)
Using low-energy electron microscopy, we measure the diffusion of Pd into bulk Cu at the Cu(100) surface. Interdiffusion is tracked by measuring the dissolution of the Cu(100)-c(2 × 2)-Pd surface alloy during annealing (T>240 °C). The activation barrier for Pd diffusion from the surface alloy into the bulk is determined to be (1.8 ± 0.6) eV. During(More)
Highly uniform step and termination structures on 4Hand 6H-SiC(0001) surfaces have been prepared via moderate annealing in disilane. Atomic force microscopy and dark-field low-energy electron microscopy imaging indicate single-phase terminations separated solely by half-unit-cell-height steps, driven by stacking fault energy. The atomic structure of(More)