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Zichner R.,Fraunhofer Institute for Electronic Nano Systems | Baumann R.R.,Fraunhofer Institute for Electronic Nano Systems | Baumann R.R.,TU Chemnitz
Advances in Radio Science | Year: 2013

Miniaturized, highly integrated wireless communication systems are used in many fields like logistics and mobile communications. Often multiple antenna structures are integrated in a single product. To achieve such a high level of integration the antenna structures are manufactured e.g. from flexible boards or via LDS (laser direct structuring) which allows the production of complex monopole or dipole antennas with three-dimensionally curved shapes. Main drawbacks are the sophisticated production process steps and their costs. The additive deposition of metallic inks or pastes by a printing process is an alternative manufacturing method with reduced cost. To implement such printed antennas we investigated in the fields of antenna design, simulation, printing technology and characterization. The chosen example of use was a customized dipole antenna for a Radio Frequency Identification application. The results prove the intended functionality of the printed dipole in regard to a highly cost efficient printing manufacturing. © 2011 Author(s).

Braeuer J.,Fraunhofer Institute for Electronic Nano Systems | Besser J.,Fraunhofer Institute for Electronic Nano Systems | Wiemer M.,Fraunhofer Institute for Electronic Nano Systems | Gessner T.,Fraunhofer Institute for Electronic Nano Systems | Gessner T.,TU Chemnitz
Sensors and Actuators, A: Physical | Year: 2012

Considering the demand for low temperature bonding processes in 3D integration and packaging of microelectronic or micromechanical components, this paper introduces a method that uses a specific form of local heat generation, which is based on nano scale reactive material systems. Such systems consist of several layers of minimum two different materials with nano scale thicknesses. These layers generate a self-propagating and exothermic reaction during their intermixing. The resulting heat can be used as the heat source for bonding processes such as solder bonding of micro components. In contrast to other researchers, who focus on relatively thick Ni/Al foils for joining macroscopic parts, we focus on the direct deposition of reactive multilayer systems. The principle of this method is demonstrated by reactive bonding, for which we use different energetic systems. The main part of this paper deals with the preparation and investigation of integrated reactive material systems. © 2012 Elsevier B.V. All rights reserved.

Kang H.,TU Chemnitz | Sowade E.,TU Chemnitz | Baumann R.R.,TU Chemnitz | Baumann R.R.,Fraunhofer Institute for Electronic Nano Systems
ACS Applied Materials and Interfaces | Year: 2014

We demonstrate intense pulsed light (IPL) sintering of inkjet-printed CuO layers on a primer-coated porous PET substrate to convert the electrically insulating CuO into conductive Cu. With this approach, conductive layers are obtained in less than 1 s after the printing process. The IPL sintering was performed for high productivity with minimum duration and repetition of IPL irradiation to evaluate the effect of pulse number and energy output on the conductivity and morphology of the sintered Cu layers. Depending on the energy output, sheet resistances were measured as 0.355, 0.131, and 0.121 Ω·□-1 by exposure energy of 5.48 (single pulse), 7.03 (double pulse), and 7.48 J·cm-2 (triple pulse), respectively. In contrast, an excessive energy with relatively short pulse duration causes a delamination of the Cu layer. The lowest resistivity of about 55.4 nΩ·m (corresponds to about 30% conductivity of bulk Cu) was obtained by an IPL sintering process of 0.26 s after the printing, which was composed of 2 ms triple pulses with 10 Hz frequency. © 2014 American Chemical Society.

Krasselt C.,TU Chemnitz | Schuster J.,TU Chemnitz | Schuster J.,Fraunhofer Institute for Electronic Nano Systems | Von Borczyskowski C.,TU Chemnitz
Physical Chemistry Chemical Physics | Year: 2011

Blinking dynamics of CdSe/ZnS semiconductor quantum dots (QD) are characterized by (truncated) power law distributions exhibiting a wide dynamic range in probability densities and time scales both for off- and on-times. QDs were immobilized on silicon oxide surfaces with varying grades of hydroxylation and silanol group densities, respectively. While the off-time distributions remain unaffected by changing the surface properties of the silicon oxide, a deviation from the power law dependence is observed in the case of on-times. This deviation can be described by a superimposed single exponential function and depends critically on the local silanol group density. Furthermore, QDs in close proximity to silanol groups exhibit both high average photoluminescence intensities and large on-time fractions. The effect is attributed to an interaction between the QDs and the silanol groups which creates new or deepens already existing hole trap states within the ZnS shell. This interpretation is consistent with the trapping model introduced by Verberk et al. (R. Verberk, A. M. van Oijen and M. Orrit, Phys. Rev. B, 2002, 66, 233202). © 2011 the Owner Societies.

Hammerschmidt J.,TU Chemnitz | Wolf F.M.,TU Chemnitz | Goedel W.A.,TU Chemnitz | Baumann R.R.,TU Chemnitz | Baumann R.R.,Fraunhofer Institute for Electronic Nano Systems
Langmuir | Year: 2012

Inkjet printing is employed to apply a mechanically stable reinforcing pattern to polymeric microsieves prepared by float casting, where particles are used as molds for the pores. A mixture of silica particles and nonvolatile monomers is cast onto a water surface and subsequently photopolymerized to produce membranes consisting of a polymer film with embedded particles. These composite membranes are transferred onto an aluminum foil. Subsequently, a UV-curable ink is directly inkjet-printed onto the membranes in line patterns of grids or honeycombs and cured by UV radiation to create a mechanically reinforcing pattern. Afterwards, the particles and the aluminum foil are removed by chemical etching. The reinforcing pattern overcasts 40% of the previously manufactured membrane, is mechanically stable, and gives the microsieves such a robustness that they can be handled in further manufacturing processes. © 2012 American Chemical Society.

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