Search results for "probe"

Anisotropic chemical etching of semipolar \{10\bar {1}\bar {1}\}\mbox {/} \{10\bar {1}{+}1\} ZnO crystallographic planes: polarity versus dangling bo…

2009

ZnO thin films grown by metal?organic vapor phase epitaxy along the nonpolar direction and exhibiting semipolar facets have been chemically etched with HCl. In order to get an insight into the influence of the ZnO wurtzite structure in the chemical reactivity of the material, Kelvin probe microscopy and convergent beam electron diffraction have been employed to unambiguously determine the absolute polarity of the facets, showing that facets are unstable upon etching in an HCl solution and transform into planes. In contrast, facets undergo homogeneous chemical etching perpendicular to the initial crystallographic plane. The observed etching behavior has been explained in terms of surface oxy…

Single-molecule switching with non-contact atomic force microscopy

2011

We report upon controlled switching of a single 3,4,9,10-perylene tetracarboxylic diimide derivative molecule on a rutile TiO(2)(110) surface using a non-contact atomic force microscope at room temperature. After submonolayer deposition, the molecules adsorb tilted on the bridging oxygen row. Individual molecules can be manipulated by the atomic force microscope tip in a well-controlled manner. The molecules are switched from one side of the row to the other using a simple approach, taking benefit of the sample tilt and the topography of the titania substrate. From density functional theory investigations we obtain the adsorption energies of different positions of the molecule. These adsorp…

Correlating Cathodoluminescence and Kelvin Probe Force Microscopy Measurements of Methylammonium-Free 2D Ruddlesden Popper Passivated Perovskite Abso…

2021

Three-dimensional atomic force microscopy mapping at the solid-liquid interface with fast and flexible data acquisition

2016

We present the implementation of a three-dimensional mapping routine for probing solid-liquid interfaces using frequency modulation atomic force microscopy. Our implementation enables fast and flexible data acquisition of up to 20 channels simultaneously. The acquired data can be directly synchronized with commercial atomic force microscope controllers, making our routine easily extendable for related techniques that require additional data channels, e.g., Kelvin probe force microscopy. Moreover, the closest approach of the tip to the sample is limited by a user-defined threshold, providing the possibility to prevent potential damage to the tip. The performance of our setup is demonstrated …

Synthesis of azobenzene substituted tripod-shaped bi(p-phenylene)s. Adsorption on gold and CdS quantum-dots surfaces

2013

We report here the synthesis of several tripod-shaped oligo(p-phenylene)s with legs composed of two phenylene units. Each leg is end-capped with a thioacetate group for adhesion to metallic surfaces. An azobenzene chromophore group is present on the functional arm of the tripod. The key step in the synthesis is the Pd-catalyzed Suzuki cross-coupling reaction of the silicon derivative core molecule with substituted phenyl moieties and azobenzene derivatives. Gold surfaces prepared by thermal evaporation and CdS quantum-dots surfaces were covered by the tripod-shaped molecules. Modified surfaces were characterized by atomic force microscopy (AFM), fluorescence, and Kelvin Probe analyses.

Structural characterization of selective area growth GaN nanowires by non-destructive optical and electrical techniques

2015

The growth selectivity and structural quality of GaN nanowires obtained by plasma-assisted molecular beam epitaxy on pre-patterned GaN(0001) templates are investigated by means of non-destructive techniques. Optimum control over the nanowire arrangement and size requires a pitch between the mask apertures below twice the diffusion length of Ga atoms. Lower pitches, however, seem to slightly diminish the structural quality of the material, as revealed by the increase of the Raman peak linewidths. The photoluminescence spectra of the nanowires show a considerable presence of basal plane stacking faults, whose density increases for decreasing nanowire diameter. The capabilities of Kelvin probe…

Insights into Kelvin probe force microscopy data of insulator-supported molecules

2015

We present a detailed analysis and understanding of Kelvin probe force microscopy (KPFM) data for a system of point charges in a vacuum-dielectric tip-sample system. Explicit formulae describing the KPFM signal $\ensuremath{\Delta}V$ are derived for the two KPFM operation modes, namely amplitude modulation and frequency modulation (FM). The formulae allow for a physical interpretation of the resulting KPFM signal, reveal contributing parameters, and especially disclose an additive behavior. We numerically evaluate these equations and show exemplary KPFM slice data for a single point charge. The theoretical analysis is complemented by two-dimensional FM-KPFM maps obtained experimentally on 2…

Assessment of Polarity in GaN Self-Assembled Nanowires by Electrical Force Microscopy

2015

In this work, we demonstrate the capabilities of atomic force microscopies (AFMs) for the nondestructive determination of the polarity of GaN nanowires (NWs). Three complementary AFMs are analyzed here: Kelvin probe force microscopy (KPFM), light-assisted KPFM, and piezo-force microscopy (PFM). These techniques allow us to assess the polarity of individual NWs over an area of tens of μm(2) and provide statistics on the polarity of the ensemble with an accuracy hardly reachable by other methods. The precise quantitative analysis of the tip-sample interaction by multidimensional spectroscopic measurements, combined with advanced data analysis, has allowed the separate characterization of elec…

Studies of host-guest thin films of corona-poled betaine-type polar molecules by kelvin probe technique and atomic force microscopy

2004

In this work betaine-type molecules were investigated. As a result of the asymmetry of charge distribution, molecules possess in the ground state a considerable permanent dipole moment. The decay of surface potential of poled polymer films is dependent at least on two relaxation processes. The influence of glass transition of PMMA on thermal dependence of the surface potential is shown. The transition temperature, where no changes of the surface potential appeared, is related to glass transition temperature of the host-guest system. The topography of the film surface was obtained by AFM.

Kelvin probe force microscopy studies of the charge effects upon adsorption of carbon nanotubes and C 60 fullerenes on hydrogen-terminated diamond

2018

Hydrogen-terminated diamond is known for its unusually high surface conductivity that is ascribed to its negative electron affinity. In the presence of acceptor molecules, electrons are expected to transfer from the surface to the acceptor, resulting in p-type surface conductivity. Here, we present Kelvin probe force microscopy (KPFM) measurements on carbon nanotubes and C60 adsorbed onto a hydrogen-terminated diamond(001) surface. A clear reduction in the Kelvin signal is observed at the position of the carbon nanotubes and C60 molecules as compared with the bare, air-exposed surface. This result can be explained by the high positive electron affinity of carbon nanotubes and C60, resulting…