Daniel M. Schaadt

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Surface plasmon resonances in metallic nanoparticles are of interest for a variety of applications due to the large electromagnetic field enhancement that occurs in the vicinity of the metal surface, and the dependence of the resonance wavelength on the nanoparticle’s size, shape, and local dielectric environment. Here we report an engineered enhancement of(More)
High-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) images of electron-transparent samples show dominant atomic number (Z-) contrast with a high lateral resolution. HAADF STEM at low electron energies <30 keV is applied in this work for quantitative composition analyses of InGaAs quantum wells. To determine the local(More)
Scanning force microscopy was used to study localized charge deposition and subsequent transport in Co nanoclusters embedded in SiO2 deposited on an n-type Si substrate. Co nanoclusters were charged by applying a bias voltage pulse between tip and sample, and electrostatic force microscopy was used to image charged areas, to determine quantitatively the(More)
Sub-wavelength photonic structures and nanoscale materials have the potential to greatly improve the efficiencies of solar cells by enabling maximum absorption of sunlight. Semiconductor heterostructures provide versatile opportunities for improving absorption of infrared radiation in photovoltaic devices, which accounts for half of the power in the solar(More)
In this study, we investigated pre-structured (100) GaAs sample surfaces with respect to subsequent site-selective quantum dot growth. Defects occurring in the GaAs buffer layer grown after pre-structuring are attributed to insufficient cleaning of the samples prior to regrowth. Successive cleaning steps were analyzed and optimized. A UV-ozone cleaning is(More)
: The number of quantum dots which nucleate at a certain place has to be controllable for device integration. It was shown that the number of quantum dots per nucleation site depends on the size of the hole in the substrate, but other dimensions of the nucleation site are vague. We report on the influence of hole shape on site-selectively grown InAs quantum(More)
We have used conductive atomic force microscopy to image the nanoscale current distribution in SrTiO3 grown epitaxially on n -Si by molecular beam epitaxy. Topographic and current images were obtained simultaneously in contact mode with a bias voltage applied to the sample. Topographic images show a flat surface with a roughness of about 0.5 nm. Current(More)
Scanning Kelvin probe microscopy is used to image surface potential variations in GaN ~0001! grown by hydride vapor phase epitaxy. The influence of finite probe tip size on these measurements is analyzed, suggesting that significant differences between measured and actual surface potential variations may exist. Experimentally, localized regions in which the(More)
The characteristics of dislocation-related leakage current paths in an AlGaN/GaN heterostructure grown by molecular-beam epitaxy and their mitigation by local surface modification have been investigated using conductive atomic force microscopy. When a voltage is applied between the tip in an atomic force microscope ~AFM! and the sample, a thin insulating(More)
Structures in which magnetic and electronic materials are combined offer a variety of possibilities for realization of devices with improvement functionality or performance compared to conventional devices. We have designed, characterized, and analyzed a novel hybrid magnetoelectronic device: a monolithic field-effect-transistor-amplified magnetic field(More)