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Hermann P.,Robert Koch Institute | Hermann P.,Fraunhofer Center Nanoelectronic Technologies | Fabian H.,Robert Koch Institute | Naumann D.,Robert Koch Institute | Hermelink A.,Robert Koch Institute
Journal of Physical Chemistry C | Year: 2011

Raman spectroscopic characterization of biological nanostructures requires near-field techniques, which provide nanoscale resolution and high sensitivity simultaneously. Tip-enhanced Raman spectroscopy provides the required sensitivity to obtain chemical and structural information from such small structures. However, near-field spectra typically show significant intensity variations and band shifts when comparing the spectroscopic information acquired from sample positions even a few nm apart. In the present study, we compare far-field and near-field Raman spectra of silicon-based samples and biological nanostructures like avipox virus or amyloid fibrils. It is found that the width of the bands in tip-enhanced spectra is typically narrower than in the corresponding far-field spectra. Additionally, the observed spectral variations in near-field Raman spectra are strongly influenced by the structural and chemical heterogeneity of the sample. © 2011 American Chemical Society. Source


Oszinda T.,Fraunhofer Center Nanoelectronic Technologies | Oszinda T.,Fraunhofer Center Nanoelektronische Techonlogien | Schaller M.,Globalfoundries | Schulz S.E.,TU Chemnitz
Journal of the Electrochemical Society | Year: 2010

A vapor phase based silylation process was used to restore plasma damaged porous ultra low- κ SiOCH dielectric films. The process was carried out with 11 different silylation agents. After the processing of blanked wafers, the restoration performance was analyzed by different analytic techniques such as Fourier infrared and Auger electron spectroscopy as well as contact angle, ellipsometric porosimetry, and mercury probe measurements. Quantum mechanic calculations and practical results suggest three repair chemicals having two reactive groups to be most promising. However, a comparable electrical improvement, i.e., κ -value improvement, was achieved with chemicals having one reactive group. The removal of water during the high temperature silylation process is suggested to be the main contributor to the κ -value improvement. The recovery of the surface free energy inhibits or retards water from returning after the silylation process. The chemicals with two reactive groups providing the highest degree of silylation are found to be most appropriate for ultra low- κ dielectric (ULK) recovery. But, depending on the requirement for ULK restoration (e.g., κ -value, surface recovery, etc.), chemicals having one reactive group can be sufficient as well. © 2010 The Electrochemical Society. Source


Schunemann C.,TU Dresden | Wynands D.,Leibniz Institute of Polymer Research | Wynands D.,University of California at Santa Barbara | Wilde L.,Fraunhofer Center Nanoelectronic Technologies | And 7 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

To achieve efficient organic solar cells, donor and acceptor molecules are mixed in the photoactive layer to form a so-called bulk heterojunction. Due to molecular interactions, a certain degree of phase separation between donor and acceptor domains arises, which is necessary to achieve efficient charge extraction within the absorber layer. However, the mechanism that induces the phase separation is not fully understood and gaining detailed information about the molecular arrangement within these blend layers is quite challenging. We show that grazing incidence x-ray diffraction, combined with variable angle spectroscopic ellipsometry is a suitable way to investigate the molecular structure of blend layers in detail, consisting of a mixture of zinc-phthalocyanine (ZnPc) and C 60. The degree of phase separation within the blend layer is influenced by substrate heating during the co-evaporation of ZnPc and C 60 and by a variation of the mixing ratio. The effect of different blend layer morphologies on optical and electrical device performance is investigated by solar cell characterization and mobility measurements. We find that the molecular arrangement of C 60 provides the essential driving force for efficient phase separation. Whereas spherical C 60 molecules are able to form crystalline domains when deposited at elevated substrate temperatures, no ZnPc crystallites are observed, although the planar ZnPc molecules are not randomly oriented but standing upright within its domains. Comparing specular and grazing incidence x-ray diffraction, we find that only the latter method is able to detect nanocrystalline C 60 in thin films due to its polycrystalline nature and small sized nanocrystallites. Solar cell measurements show an increase in fill factor and external quantum efficiency signal for blends with enhanced phase separation, induced by higher substrate temperatures. However, grazing incidence x-ray diffraction measurements reveal that ZnPc and C 60 already form separate domains in unheated ZnPc:C 60 blends, which provide fill factors close to 50% in the corresponding solar cells. © 2012 American Physical Society. Source


Finn A.,TU Dresden | Lu B.,TU Dresden | Kirchner R.,TU Dresden | Thrun X.,Fraunhofer Center Nanoelectronic Technologies | And 2 more authors.
Microelectronic Engineering | Year: 2013

Polymeric molds replicated from a master structure can provide intrinsic anti-sticking behavior and UVtransparency. They can be replicated from various substrates and offer cost efficient replication of multiple working stamps from only one master. They also allow the use of various imprint methods including UV- or thermal-assisted ones. Usually, the polymer material exhibits mechanical and surface-chemical properties which differ from hard mold materials like silicon, silicon dioxide or metals. Due to this, the molds might be deformed or even destroyed during imprint or cleaning. This is pronounced for high aspect ratio patterns, as they occur, if imprint is used as direct pattering method. The affinity to pattern damage of polymeric molds during cleaning is investigated in this paper. Different possible polymeric mold materials are considered. Experimental data is compared to simulation results and shows good agreement. Different exemplary patterns are investigated and a best suitable material is found. It is stable for feature aspect ratios up to 10 for half pitch gratings in the considered range of dimensions. © 2013 Elsevier B.V. All rights reserved. Source


Boscke T.S.,Loberwallgraben 2 | Boscke T.S.,NaMLab gGmbH | Teichert S.,UAS Jena | Brauhaus D.,RWTH Aachen | And 5 more authors.
Applied Physics Letters | Year: 2011

We investigated phase transitions in ferroelectric silicon doped hafnium oxide (FE-Si:HfO2) by temperature dependent polarization and x-ray diffraction measurements. If heated under mechanical confinement, the orthorhombic ferroelectric phase reversibly transforms into a phase with antiferroelectric behavior. Without confinement, a transformation into a monoclinic/tetragonal phase mixture is observed during cooling. These results suggest the existence of a common higher symmetry parent phase to the orthorhombic and monoclinic phases, while transformation between these phases appears to be inhibited by an energy barrier. © 2011 American Institute of Physics. Source

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