Bad Münster am Stein-Ebernburg, Germany
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Ji D.,University of Munster | Donner A.D.,Institute For Materialphysik | Wilde G.,Institute For Materialphysik | Hu W.,CAS Beijing National Laboratory for Molecular | Fuchs H.,University of Munster
RSC Advances | Year: 2015

The development of high-integration, flexible and transferable devices is a very important premise to realize authentically wearable applications in the future. Here, we report how to fabricate flexible, free-standing and high-resolution (down to 5 μm) top-contact OFETs based on a polystyrene (PS) dielectric layer. In this process, we use a special sacrificial layer, poly(sodium-4-styrene sulfonate) (PSSNa). It is low-cost, dissolves quickly in water at room temperature and has good compatibility with most organic material processing techniques. With the help of this sacrificial layer, this kind of free-standing transistors can be successfully transferred onto arbitrary substrates. Furthermore, the degradation of the performance of the devices after multiple and successive transfer is tolerated. © The Royal Society of Chemistry 2015.

Pundt A.,Institute For Materialphysik
Ceramic Transactions | Year: 2013

For hydrogen storage applications, nano-scale metal-hydrogen systems are suggested to reduce loading and unloading times. But, nano-scaling the system does also change other physical properties. Many changes can be related to micro-structure and mechanical stress, but also to new structures only evolving in the nanometer-range. This paper shortly summarizes changes of metal-hydrogen systems turned to nano-scale and discusses the findings with regard to storage applications.

Boll T.,King Abdullah University of Science and Technology | Boll T.,Institute For Materialphysik | Al-Kassab T.,King Abdullah University of Science and Technology | Al-Kassab T.,Institute For Materialphysik
Ultramicroscopy | Year: 2013

In this paper simulations of the field evaporation process during field ion microscopy (FIM) and atom probe tomography (APT) are presented and compared with experimental data. The Müller-Schottky-model [1] was extended to include the local atomic arrangement on the evaporation process of atoms. This arrangement was described by the sum of the next-neighbor-binding-energies, which differ for an atom of type A, depending on how many A-A, B-B or A-B bonds are present. Thus simulations of APT-data of intermetallic phases become feasible. In this study simulations of L10-TiAl with additions of Nb are compared with experimental data. Certain artifacts, which appear for experimental data are treated as well. © 2012 Elsevier B.V.

Huger E.,Clausthal University of Technology | Kube R.,Institute For Materialphysik | Bracht H.,Institute For Materialphysik | Stahn J.,Paul Scherrer Institute | And 2 more authors.
Physica Status Solidi (B) Basic Research | Year: 2012

We carried out experiments of self-diffusion in single crystalline silicon at a temperature of 900°C by a method that is based on neutron reflectometry in combination with 29Si/ 28Si isotope multilayers. The experimental reflectivity pattern shows artificial Bragg peaks due to isotope periodicity and is fitted by the program Parratt32. Diffusivities are calculated from the roughness parameter of the isotope interfaces. The results are compared to that one obtained from a simple analytical expression on the reduction of the Bragg peak. The results exhibit that both methods deliver identical diffusivities within error limits. The diffusivity of 4×10 -22m 2·s -1 does not depend on annealing time for diffusion on a length scale of 1-6nm and is in good accordance to literature data, ranging between 1 and 10×10 -22m 2·s -1. The results demonstrate that the neutron reflectometry method is well suited to determine self-diffusivities in single crystalline silicon at very short length scales. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Romero-Salazar C.,Institute For Materialphysik | Jooss C.,Institute For Materialphysik | Hernandez-Flores O.A.,Benito Juárez Autonomous University of Oaxaca
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

The study of electric field distributions induced by flux creep in type-II superconducting films allows for important insight into the mechanism of vortex dynamics, the temporal evolution of flux and current distributions, and the occurrence of local losses. Most studies are based on the assumption that a phenomenological materials law, which has been extracted from macroscopic transport measurements, can be also applied to the local electric field during magnetization decay. We evaluate this ansatz by reconstructing the three-dimensional-induced Ei and potential Ep electric fields from experimentally measured time dependence of the flux density distribution. The results are quantitatively compared with solutions of the nonlinear and nonlocal equation of motion for the flux penetration, where the Maxwell equations as well as a materials law are utilized to obtain a two-dimensional Ei,2D and Ep,2D. We focus our analysis on the electric field distributions on a partially penetrated magnetized state of an epitaxial YBa2 Cu3 O6.95 film. © 2010 The American Physical Society.

Song T.E.,Institute For Materialphysik | Wilde G.,Institute For Materialphysik | Peterlechner M.,Institute For Materialphysik
Applied Physics Letters | Year: 2014

Nanoscale Bi particles embedded in a Zn matrix were obtained by casting and melt-spinning, resulting in quenching rate-dependent sizes and shapes. With decreasing Bi particle size, an increasing aspect ratio was observed. Due to high resolution transmission electron microscopy performed for different orientations of the nanoparticles and the matrix, the three-dimensional shape and the respective crystallographic orientations of the Bi nanoparticles as well as the orientation relationship with the matrix have been evaluated. It is suggested that the size-dependence of the nanoparticle morphologies has a strong impact on their thermal stabilities thus affecting the size dependence of the melting temperature. © 2014 AIP Publishing LLC.

Mazumder B.,CNRS Material Physics Group | Vella A.,CNRS Material Physics Group | Deconihout B.,CNRS Material Physics Group | Al-Kassab T.,Institute For Materialphysik | Al-Kassab T.,King Abdullah University of Science and Technology
Ultramicroscopy | Year: 2011

In this paper the field evaporation properties of bulk MgO and sandwiched MgO layers in Fe are compared using laser assisted Atom Probe Tomography. The comparison of flight time spectra gives an estimate of the evaporation times as a function of the wavelength and the laser energy. It is shown that the evaporation takes place in two steps on two different time scales in MgO. It is also shown that as long as the MgO layer is buried in Fe, the evaporation is dominated by the photon absorption in Fe layer at the tip apex. Eventually the evaporation process of MgO is discussed based on the difference between the bulk materials and the multilayer samples. © 2010 Elsevier B.V.

Gusak A.M.,Cherkasy National University | Schmitz G.,Institute For Materialphysik | Tyutyunnyk N.,Cherkasy National University
Defect and Diffusion Forum | Year: 2012

The problem of phase competition during reactive diffusion is revisited. Nucleation of an intermediate phase at an interface under external fluxes in the neighboring phases is considered in the frame of kinetic Fokker-Planck approach. Effective nucleation barrier depending on the divergence of external fluxes is introduced. New suppression/growth criteria are obtained. © (2012) Trans Tech Publications.

Mazumder B.,CNRS Material Physics Group | Vella A.,CNRS Material Physics Group | Gilbert M.,IMEC | Deconihout B.,CNRS Material Physics Group | Schmitz G.,Institute For Materialphysik
New Journal of Physics | Year: 2010

In this work, the lifetime of silicon (Si) ions generated through photoionization of Si surface atoms from a field emitter was measured. Under low-intensity fs laser pulse illumination, a linear dependence of the number of evaporated ions per pulse on the laser intensity was observed. A simple model was developed to explain this linear dependence and to estimate the rate of success of the field evaporation process. It is shown that the number of evaporated ions per pulse depends on the standing field applied to the Si surface, demonstrating the existence of an ionic energy barrier for Si ions. The lifetime of these ions was estimated to be 0.5 ps. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Sunder K.,Institute For Materialphysik | Grofmeier M.,Institute For Materialphysik | Staskunaite R.,Institute For Materialphysik | Bracht H.,Institute For Materialphysik
Zeitschrift fur Physikalische Chemie | Year: 2010

Conductivity measurements and diffusion studies with radioactive and stable isotopes were performed to investigate the diffusion of both network modifiers (alkali (A) and alkaline-earth (M) ions) and network formers (oxygen (O) and silicon (Si)) in various mixed-cation silicate glasses below the respective glass transition temperatures. The dynamics of the network modifiers A and M were studied in bulk glasses prepared from the melt and in sol-gel derived glass films. The diffusion anneals were performed under air and under reducing conditions in forming gas. No impact of the glass preparation on the diffusion of the network modifiers was found. However, the diffusion of the alkaline-earth ions is affected by additional defects formed under reducing conditions. The dynamics of the network formers O and Si was investigated against the type of alkali and alkaline-earth ions, their composition ratio, and the number of non-bridging oxygens. We found that Si diffusion is directly related to the rigidity of the glass. Combining the data on O diffusion with previous results on the diffusion of alkaline-earth ions M in glasses of the same composition, we conclude that the diffusion of O is likely assisted by M via the formation of O?M pairs. © by Oldenbourg Wissenschaftsverlag, München.

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