Strukturuntersuchungen von auf Festkörperoberflächen adsorbierten [Mn6IIICrIII]3+[Mn^{III}_{6}Cr^{III}]^{3+} Einzelmolekülmagneten mittels Raster-Kraftmikroskopie und Kelvin-Sonden-Kraftmikroskopie im Ultrahochvakuum

Gryzia A. Strukturuntersuchungen von auf Festkörperoberflächen adsorbierten $[Mn^{III}_{6}Cr^{III}]^{3+}$ Einzelmolekülmagneten mittels Raster-Kraftmikroskopie und Kelvin-Sonden-Kraftmikroskopie im Ultrahochvakuum. Bielefeld: Universitätsbibliothek Bielefeld; 2014.Diese Arbeit befasst sich mit dem Einzelmolekülmagneten (SMM) $[Mn^{III}_{6}Cr^{III}]^{3+}$ und der Adsorption desselben auf Oberflächen im UHV. Die Präparation des Einzelmolekülmagneten geschah mittels Droplet Technik aus Lösung heraus. Die so präparierten Substrate, darunter HOPG, Glimmer, sowie SiO2 und Si3N4 wurden mittels Röntgenphotoelektronenspektroskopie (XPS), Rastertunnelmikroskopie (STM), Rasterkraftmikroskopie (AFM) und Kelvin-Sonden-Kraftmikroskopie (KPFM) im Ultrahochvakuum (UHV) untersucht. Der SMM liegt mit drei verschiedenen Gegenionen vor, die zu drei unterschiedlichen Molekülen führen. Zusammen mit den verschiedenen Substraten ergeben sich spezifische Resultate in der Adsorption. Die Kombination des SMM $[Mn^{III}_{6}Cr^{III}]$ (ClO4)3 auf HOPG führt zu zwei Adsorptionscharakteristika, die einzigartig im Vergleich mit anderen $[Mn^{III}_{6}Cr^{III}]^{3+}$ basierten SMMs und Substraten sind. Der SMM zeigt einerseits eine Dekomposition auf der Oberfläche, bei der sich das Molekül in seine Hauptkomponenten zersetzt. Auf der Oberfläche lassen sich intakte und zersetzte Moleküle gleichzeitig beobachten und auch durch die jeweilige Kontaktpotentialdifferenz (CPD) unterscheiden. Das zersetzte Molekül wurde modelliert, wodurch sowohl die Ausrichtung des intakten als auch des zersetzten Moleküls auf dem Substrat beschrieben werden kann. Andererseits gibt es Bereiche in denen intakte Moleküle geordnet auf dem Substrat adsorbieren. Dies resultiert in Strukturen mit großer Symmetrie auf der Oberfläche. Die Fourieranalyse zeigt zweizählige Strukturen und solche, die ebenfalls zweizählig, aber einer vierzähligen Symmetrie sehr ähnlich sind. Ein hierzu entwickeltes Modell ist in der Lage die Abstände und Winkel der Moleküle untereinander, sowie relativ zum Substrat zu beschreiben

Crystallographic order and decomposition of [MnIII6CrIII]3+ single-molecule magnets deposited in submonolayers and monolayers on HOPG studied by means of molecular resolved Atomic Force Microscopy (AFM) and Kelvin Probe Force Microscopy in UHV

Gryzia A, Volkmann T, Brechling A, et al. Crystallographic order and decomposition of [MnIII6CrIII]3+ single-molecule magnets deposited in submonolayers and monolayers on HOPG studied by means of molecular resolved Atomic Force Microscopy (AFM) and Kelvin Probe Force Microscopy in UHV. Nanoscale Research Letters. 2014;9(1): 60.Monolayers and submonolayers of [MnIII6CrIII]3+ single-molecule magnets (SMMs) adsorbed on highly oriented pyrolytic graphite (HOPG) using the droplet technique characterized by non-contact atomic force microscopy (nc-AFM) as well as by Kelvin probe force microscopy (KPFM) show island-like structures with heights resembling the height of the molecule. Furthermore, islands were found which revealed ordered 1D as well as 2D structures with periods close to the width of the SMMs. Along this, islands which show half the heights of intact SMMs were observed which are evidences for a decomposing process of the molecules during the preparation. Finally, models for the structure of the ordered SMM adsorbates are proposed to explain the observations

Heptanuclear [FeIII6CrIII]3+ Complexes Experimentally Studied by Means of Magnetometry, X-ray Diffraction, XAS, XMCD and Spin-Polarized Electron Spectroscopy in Cross-Comparison with [MnIII6CrIII]3+ Single-Molecule Magnets

Dohmeier N, Helmstedt A, Müller N, et al. Heptanuclear [FeIII6CrIII]3+ Complexes Experimentally Studied by Means of Magnetometry, X-ray Diffraction, XAS, XMCD and Spin-Polarized Electron Spectroscopy in Cross-Comparison with [MnIII6CrIII]3+ Single-Molecule Magnets. Magnochemistry. 2016;2(1): 5

The structure of [Mn-6(III) Cr-III](3+) single-molecule magnets deposited in submono-layers and monolayers on surfaces studied by means of molecular resolved atomic force microscopy (AFM) and Kelvin Probe Force Microscopy in UHV

Heinzmann U, Gryzia A, Volkmann T, Brechling A, Höke V, Glaser T. The structure of [Mn-6(III) Cr-III](3+) single-molecule magnets deposited in submono-layers and monolayers on surfaces studied by means of molecular resolved atomic force microscopy (AFM) and Kelvin Probe Force Microscopy in UHV. In: Collisions involving condensed matter [Abstracts]. Journal of Physics Conference Series. Vol 488. Bristol: Iop Publishing; 2014.Single molecule magnets (SMM) deposited in submonolayers and monolayers have been analyzed with respect to their structures by means of non-contact AFM (topographic as well as damping mode) and Kelvin Probe Force Microscopy with molecular resolution

Preparation of monolayers of [Mn^III ₆Cr^III]³⁺single-molecule magnets on HOPG, mica and silicon surfaces and characterization by means of non-contact AFM

Abstract We report on the characterization of various salts of [MnIII 6CrIII]3+ complexes prepared on substrates such as highly oriented pyrolytic graphite (HOPG), mica, SiO2, and Si3N4. [MnIII 6CrIII]3+ is a single-molecule magnet, i.e., a superparamagnetic molecule, with a blocking temperature around 2 K. The three positive charges of [MnIII 6CrIII]3+ were electrically neutralized by use of various anions such as tetraphenylborate (BPh4 -), lactate (C3H5O3 -), or perchlorate (ClO4 -). The molecule was prepared on the substrates out of solution using the droplet technique. The main subject of investigation was how the anions and substrates influence the emerging surface topology during and after the preparation. Regarding HOPG and SiO2, flat island-like and hemispheric-shaped structures were created. We observed a strong correlation between the electronic properties of the substrate and the analyzed structures, especially in the case of mica where we observed a gradient in the analyzed structures across the surface.</p

Preparation of monolayers of [Mn(III) (6)Cr(III)](3+) single-molecule magnets on HOPG, mica and silicon surfaces and characterization by means of non-contact AFM

Gryzia A, Predatsch H, Brechling A, et al. Preparation of monolayers of [Mn(III) (6)Cr(III)](3+) single-molecule magnets on HOPG, mica and silicon surfaces and characterization by means of non-contact AFM. Nanoscale Research Letters. 2011;6(1): 486.We report on the characterization of various salts of [Mn(6)(III)Cr(III)](3+) complexes prepared on substrates such as highly oriented pyrolytic graphite (HOPG), mica, SiO(2), and Si(3)N(4). [Mn(6)(III)Cr(III)](3+) is a single-molecule magnet, i.e., a superparamagnetic molecule, with a blocking temperature around 2 K. The three positive charges of [Mn(6)(III)Cr(III)](3+) were electrically neutralized by use of various anions such as tetraphenylborate (BPh(4)(-)), lactate (C(3)H(5)O(3)(-)), or perchlorate (ClO(4)(-)). The molecule was prepared on the substrates out of solution using the droplet technique. The main subject of investigation was how the anions and substrates influence the emerging surface topology during and after the preparation. Regarding HOPG and SiO(2), flat island-like and hemispheric-shaped structures were created. We observed a strong correlation between the electronic properties of the substrate and the analyzed structures, especially in the case of mica where we observed a gradient in the analyzed structures across the surface

The local magnetic properties of [MnIII6 CrIII]3+ and [FeIII6 CrIII]3+ single-molecule magnets deposited on surfaces studied by spin-polarized photoemission and XMCD with circularly polarized synchrotron radiation

It is demonstrated that local magnetic moments of single molecule magnets (SMM) normally studied by XMCD at very low temperatures and high magnetic fields can be measured by means of spin-resolved electron emission in the paramagnetic phase at room temperature by use of circularly polarized radiation.publishe

Preparation and characterization of gold nanocrystals on NaCl(100) surfaces as labels for the dynamical x-ray tracking technique

Slieh J, Winter A, Gryzia A, et al. Preparation and characterization of gold nanocrystals on NaCl(100) surfaces as labels for the dynamical x-ray tracking technique. Thin Solid Films. 2009;517(11):3257-3261.We report on the fabrication of single crystalline gold nanocrystals of sizes between 10 nm and 25 nm. Gold was deposited under ultra high vacuum conditions on a freshly-cleaved NaCl(100) surface by means of the Molecular Beam Epitaxy technique. The preparation parameters substrate temperature and average thickness of the deposited gold were studied systematically. After the preparation, the crystals were characterized by means of different techniques, such as Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM), X-Ray Diffractometry (XRD) and Laue Diffractometry. Measurements of the deposited cluster size, as measured by AFM, and the crystal size, as measured by XRD exhibited similar results at substrate temperatures between approx. 200 degrees C and 250 degrees C, indicating a high amount of single gold crystals. TEM images of gold crystals, made after the gold crystals had been dissolved in an aqueous 3-[(3-cholamidopropyl)dimethyl-ammonio]propane solution, support these results. Further, an effect of the substrate temperature during the deposition on the orientation of the gold crystals with respect to the NaCl(100) surface was observed. XRD measurements reveal a perpendicular texture of Au (111) parallel to NaCl(001) at approximately 310 degrees C. The second detected texture:Au(001)parallel to NaCl(001) (in plane) and Au[100]parallel to NaCl[100] (perpendicular) was observed over the complete studied temperature range (180 degrees C-330 degrees C). (C) 2008 Elsevier B.V. All rights reserved

Exposure of [(Mn6CrIII)-Cr-III](3+) single-molecule magnets to soft X-rays: The effect of the counterions on radiation stability

Helmstedt A, Sacher M, Gryzia A, et al. Exposure of [(Mn6CrIII)-Cr-III](3+) single-molecule magnets to soft X-rays: The effect of the counterions on radiation stability. Journal of Electron Spectroscopy and Related Phenomena. 2012;184(11-12):583-588.X-ray absorption spectroscopy studies of the [(Mn6CrIII)-Cr-III](3+) single-molecule magnet deposited as a microcrystalline layer on gold substrates are presented. The oxidation state of the manganese centers changes from Mn-III to Mull due to irradiation with soft X-rays. The influence of the charge-neutralizing anions on the stability of [(Mn6CrIII)-Cr-III](3+) against soft X-ray exposure is investigated for the different anions tetraphenylborate (BPh4-), lactate (C3H5O3-) and perchlorate (ClO4-). The exposure dependence of the radiation-induced reduction process is compared for [(Mn6CrIII)-Cr-III](3+) with the three different anions. (C) 2011 Elsevier B.V. All rights reserved