Fraunhofer Institute for Electronic Nanosystems

Chemnitz, Germany

Fraunhofer Institute for Electronic Nanosystems

Chemnitz, Germany

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Sowade E.,TU Chemnitz | Blaudeck T.,TU Chemnitz | Baumann R.R.,TU Chemnitz | Baumann R.R.,Fraunhofer Institute for Electronic Nanosystems
Crystal Growth and Design | Year: 2016

The manufacturing of three-dimensional colloidal structures on solid substrates is an important topic of applied research, aiming for photonic components especially in photovoltaic and sensor applications. Whereas conventional techniques such as wet self-assembly are based on engineering of the substrate surface energy, alternative strategies envisage the independence of the interfacial conditions. We report on inkjet printing of colloidal suspensions of monodisperse silica or polystyrene nanoparticles or both and their self-assembly to spherical colloidal photonic crystals. The formation process of the colloidal nanoparticles into stable spherical colloidal assemblies (SCAs) is achieved by a self-assembly process inside tiny droplets of a stochastic mist generated intentionally instead of a jet of individual single droplets using inkjet printing. The mist-jetted, shrinking droplets serve as confined geometries for the solidification of the nanoparticles during the evaporation; thus the particles are packed into stable ball-shaped assemblies. We show how fine-tuning of the jetting parameters allows the reliable generation and deposition of three-dimensional (3D) spherical colloidal assemblies of nanoparticles variable in size and with a high packing order. Microreflectance spectroscopy proves that the degree of order in the SCA is such that photonic stop bands occur inherent for photonic crystals. © 2016 American Chemical Society.


Sowade E.,TU Chemnitz | Blaudeck T.,TU Chemnitz | Baumann R.R.,TU Chemnitz | Baumann R.R.,Fraunhofer Institute for Electronic Nanosystems
Nanoscale Research Letters | Year: 2015

We report on inkjet printing of aqueous colloidal suspensions containing monodisperse silica and/or polystyrene nanosphere particles and a systematic study of the morphology of the deposits as a function of different parameters during inkjet printing and solvent evaporation. The colloidal suspensions act as a model ink for an understanding of layer formation processes and resulting morphologies in inkjet printing in general. We investigated the influence of the surface energy and the temperature of the substrate, the formulation of the suspensions, and the multi-pass printing aiming for layer stacks on the morphology of the deposits. We explain our findings with models of evaporation-driven self-assembly of the nanosphere particles in a liquid droplet and derive methods to direct the self-assembly processes into distinct one- and two-dimensional deposit morphologies. © 2015, Sowade et al.


Wang W.-S.,Fraunhofer Institute for Electronic Nanosystems | Lullin J.,CNRS Femto ST Institute | Froemel J.,Fraunhofer Institute for Electronic Nanosystems | Wiemer M.,Fraunhofer Institute for Electronic Nanosystems | And 5 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

The paper presents the multi-wafer bonding technology as well as the integration of electrical connection to the zscanner wafer of the micromachined array-type Mirau interferometer. A Mirau interferometer, which is a key-component of optical coherence tomography (OCT) microsystem, consists of a microlens doublet, a MOEMS Z-scanner, a focusadjustment spacer and a beam splitter plate. For the integration of this MOEMS device heterogeneous bonding of Si, glass and SOI wafers is necessary. Previously, most of the existing methods for multilayer wafer bonding require annealing at high temperature, i.e., 1100°C. To be compatible with MEMS devices, bonding of different material stacks at temperatures lower than 400°C has also been investigated. However, if more components are involved, it becomes less effective due to the alignment accuracy or degradation of surface quality of the not-bonded side after each bonding operation. The proposed technology focuses on 3D integration of heterogeneous building blocks, where the assembly process is compatible with the materials of each wafer stack and with position accuracy which fits optical requirement. A demonstrator with up to 5 wafers bonded lower than 400°C is presented and bond interfaces are evaluated. To avoid the complexity of through wafer vias, a design which creates electrical connections along vertical direction by mounting a wafer stack on a flip chip PCB is proposed. The approach, which adopts vertically-stacked wafers along with electrical connection functionality, provides not only a space-effective integration of MOEMS device but also a design where the Mirau stack can be further integrated with other components of the OCT microsystem easily. © 2015 SPIE.


Schonhoff M.,University of Paderborn | Assion F.,University of Paderborn | Hilleringmann U.,Fraunhofer Institute for Electronic Nanosystems
Smart Systems Integration 2016 - International Conference and Exhibition on Integration Issues of Miniaturized Systems, SSI 2016 | Year: 2016

Thermoelectric generators (TEGs) can be used as a self-sufficient power supply. Thereby, the application in smart systems is promising because of the large number of sensors which often also have a low power consumption. To ensure cost effective TEGs a mass producible cold pressed process was developed for Mg2Si. By adapting the process set-up, the sintering temperature and the process atmosphere, densities of spark plasma sintering materials were almost reached.


Kleine A.,University of Paderborn | Hilleringmann U.,Fraunhofer Institute for Electronic Nanosystems
Smart Systems Integration 2016 - International Conference and Exhibition on Integration Issues of Miniaturized Systems, SSI 2016 | Year: 2016

The efficiency of dye sensitized solar cells (DSSCs) is strongly influenced by the quality of the front electrode. To remove dispersal additives and to enable sintering effects the TiO2 layer has to be heated up to 450°C for one hour. Nevertheless, for flexible DSSCs the process temperature is limited by the foil to about 150°C. Hence, a sintering of the particles is not possible and the cleaning effect is also declined, but both can be compensated with the development presented in this paper. This paper demonstrates that after 90 min of permanent intensive UV-irradiation nearly all additives are evaporated. Furthermore, to decrease the stress on the foil a pulsed UV-irradiation is performed and the pulse-pause-ratio optimized.


Petrov D.,University of Paderborn | Hilleringmann U.,Fraunhofer Institute for Electronic Nanosystems
Smart Systems Integration 2016 - International Conference and Exhibition on Integration Issues of Miniaturized Systems, SSI 2016 | Year: 2016

Developed at the Paderborn University since 2010, the solar-powered model aircraft has elicited interest in the media and among students of electrical engineering. The plane is equipped with solar cells on its wings, which charge the aircraft batteries during the flight and power the aircraft engine and the electronics. Different sensors are used for navigation and for collecting information about the ambient.


Meyers T.,University of Paderborn | Vidor F.F.,University of Paderborn | Hilleringmann U.,Fraunhofer Institute for Electronic Nanosystems
Smart Systems Integration 2016 - International Conference and Exhibition on Integration Issues of Miniaturized Systems, SSI 2016 | Year: 2016

In order to improve the cut-off frequency in digital circuits a reduction of parasitic capacitances is requested. In this article we present a maskless integration process to reduce crosstalk by patterning the dielectric layer in the field region of the transistor template. Additionally, a method for structuring the semiconducting layer in the field region by lift-off technique is shown. All process steps are limited to a maximum temperature of 115°C aiming at the compatibility with flexible substrates.


Vidor F.F.,University of Paderborn | Meyers T.,University of Paderborn | Hilleringmann U.,Fraunhofer Institute for Electronic Nanosystems
Smart Systems Integration 2016 - International Conference and Exhibition on Integration Issues of Miniaturized Systems, SSI 2016 | Year: 2016

Aiming at flexible and transparent electronics, we present an integration process for ZnO based thin-film transistors on a freestanding polymeric substrate using spray-coating for the deposition of the semiconducting film. Moreover, a cost efficient post-treatment applying intensive UV irradiation combined with high humidity atmosphere leads to a simple integration process for ZnO TFTs with low parameter variations.


Baranski M.,CNRS Femto ST Institute | Bargiel S.,CNRS Femto ST Institute | Passilly N.,CNRS Femto ST Institute | Guichardaz B.,CNRS Femto ST Institute | And 5 more authors.
IEEE Photonics Technology Letters | Year: 2014

This letter reports on the development of an integrated micro-optical beam splitter that can be array-arranged. The proposed wafer-level fabrication, based on 45° saw-dicing of glass substrates, allows rapid and low-cost processing. In particular, it leads to high compactness and possibility of wafer-level alignment/assembly, suitable for vertically integrated imaging micro-instruments. The device, including additional out-of plane reflection for extraction of sensing beam, can be as small as 1 mm3. © 1989-2012 IEEE.


Baranski M.,University of Franche Comte | Bargiel S.,University of Franche Comte | Passilly N.,University of Franche Comte | Gorecki C.,University of Franche Comte | And 3 more authors.
Applied Optics | Year: 2015

This paper presents the optical design of a miniature 3D scanning system, which is fully compatible with the vertical integration technology of micro-opto-electro-mechanical systems (MOEMS). The constraints related to this integration strategy are considered, resulting in a simple three-element micro-optical setup based on an afocal scanning microlens doublet and a focusing microlens, which is tolerant to axial position inaccuracy. The 3D scanning is achieved by axial and lateral displacement of microlenses of the scanning doublet, realized by micro-electro-mechanical systems microactuators (the transmission scanning approach). Optical scanning performance of the system is determined analytically by use of the extended ray transfer matrix method, leading to two different optical configurations, relying either on a ball lens or plano-convex microlenses. The presented system is aimed to be a core component of miniature MOEMS-based optical devices, which require a 3D optical scanning function, e.g., miniature imaging systems (confocal or optical coherence microscopes) or optical tweezers. © 2015 Optical Society of America.

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