The Coffee Journal Club, the scientific community of the CTR is a fixed meeting place for the exchange of scientific topics. External prospective customers and CTR employees meet regularly and talk about the latest findings in their specialist areas. The access to the lectures is open - everyone is welcome!
For further information and registration, please contact:
Dr. Christian Mentin, SAL
Abstract: Power electronics can be found in almost every electronic device today, starting from very small scale (mW) through mobile phone chargers (W) up to wind power inverters (MW). The first cooperative research project in SAL's power electronics division is the "Tiny Power Box" project. It targets highest efficiency and smallest size for a 3-11kW on-board charger for electric vehicles. This talk will provide a short insight into power electronics at SAL in general, the aims within the Tiny Power Box project and first results using a novel electrothermal co-simulation approach.
Dr. Melinda Mohl, CTR
Abstract: In this talk I will shortly introduce myself and give an overview of my research work. Furthermore an insight to nanomaterial based devices will be given including carbon nanotube supercapacitor, inkjet printed transparent film, and WO3/WS2 hybrid material gas sensor and field effect transistor.
Dr. Stefano Lumetti, CTR
Abstract: The massive advancements in performance from the first computing machines to the current electronic devices are mainly due to the extreme miniaturization of their active components. At present, further downscaling represents an enormous technological challenge, as the size of the devices is reaching the ultimate limit of the molecular and atomic scale. The evolution of a novel discipline, known as molecular spintronics, is contributing to develop new concepts and tools to control matter at the single-molecule scale and to manipulate spins and charges in electronic devices containing one or more molecules. In this framework, single-molecule magnets are expected to be suitable candidates as building blocks for molecular spintronic devices. One of the most interesting applications is the realization of electronic circuits addressing individual molecules in the three-terminal configuration, the so-called single-molecule transistors. Groundbreaking results have been achieved in this field, including the electrical read-out and manipulation of an individual nuclear spin.
In this talk, the use of graphene as a convenient platform to fabricate molecular-scale electrodes will be discussed. A feedback-controlled electroburning (EB) procedure was employed to open nanometer-sized gaps in graphene junctions suitable to contact single molecules. A systematic characterization of the EB performed on different types of graphene devices and in different environmental conditions will be provided. By means of this EB procedure, three-terminal molecular devices were prepared in which a Tb-based single-molecule magnet (TbPc2 or Tb2Pc3) is embedded between two nm-sized graphene electrodes. The low-temperature operation of these molecular spin transistors will be examined, with a particular focus on the detection mechanism of the Tb electronic spin reversal during the sweeping of an external magnetic field.
Dr. Clement Fleury, CTR
Abstract: The miniaturization of integrated circuits has made microelectronics devices better and better in many ways, but also more and more prone to failure caused by unwanted electrical stresses, as power density increases. The reliability of Gallium Nitride High Electron Mobility Transistors (GaN HEMTs) has been investigated in terms of vertical breakdown, degradation of the conducting and blocking performance at high temperature and short-circuit load conditions. Their behaviour under pulsed stress conditions (ESD and short circuit load) was studied with the TIM technique, which allows to probe heat dissipation and free carrier concentration through their effect on the refractive index of the material.
Dr. Perla Malagò CTR, MST
Abstract: Magnetic nanostructures have received a lot of attention in latest years, both from a fundamental point of view and for several potential technological applications. In the last few years, these structures have become one of the most important and exciting areas of solid state research. One very interesting field of magnetism is the study of the spin dynamics. Collective excitation of microscopic magnetizations are called spin waves. In the last years, spin waves have been widely investigated both from the theoretical and experimental point of view in thin films, in isolated elements. Recently, it has also been found that periodic systems can support the propagation of collective spin waves. Such systems are called magnonic crystals and they open a new possibility to tailor the dynamic properties at the nanoscale, e.g. by modifying band structures through patterning. A prominent application that will be discussed in this presentation are frequency filters.
Dr. Vladimir Pashchenko / CTR
Abstract: A novel type of the transducer combining bulk and surface acoustic waves was investigated in theory and experiment. Such a transducer combines advantages of both SAW and BAW devices like the control of frequency behavior by periodic structures on the surface and the often higher electromechanical coupling and quality factors achieved with bulk acoustic waves. The investigated device was based on a piezoelectric AlN and AlScN (Sc doped AlN) thin film deposited onto a non-piezoelectric substrates. A periodical spacing of the FBAR elements with a period equal to λSAW/2 and a thickness of about λBAW/2 – both wavelength corresponding to the same frequency - leads to an efficient excitation of a surface wave on the substrate surface. FEM simulations confirmed the feasibility of proposed concept. Its advantages are a higher electromechanical coupling (up to k2=7%) as compared to a SAW device based on a homogeneous piezoelectric film on top of a non-piezoelectric substrate (k2 <1% with AlN), low acoustical losses (and as a result high Q factor), and no need for an acoustical isolation like a Bragg mirror or an air gap. The potentially large coupling coefficient makes the concept interesting for RF filters in telecommunication and wireless sensors in harsh environment exploiting.
About the presenter: Vladimir Pashchenko was born in 1985 (Merke, Kazakhstan) and received his PhD in Condensed Matter Physics in 2014 from the Saint-Petersburg State Polytechnical University in Saint-Petersburg, Russia. From 2010 to 2015 Vladimir have been worked as a SAW&BAW device design engineer in R&D company Avangard, Saint-Petersburg. Between 2015-2018 he worked in postdoc position at the Electroceramic Thin Films Group, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland. In EPFL Vladimir worked under development and investigation of the new type of piezoelectric device - hybrid BAW/SAW transducer. Also he was involved in the project of extracting the piezoelectric and elastic parameters of AlScN films from the resonance characteristics.
Prof. Hubert Brückl Department für Integrierte Sensorsysteme Donau Universität Krems Overview of the MEMS activities Dr. Wilfried Hortschitz Department für Integrierte Sensorsysteme Donau Universität Krems
Abstract: Research and development of innovative concepts for high performance sensors and sensor networks is at the heart of the department, providing solutions for a widespread range of applications, such as building automation, industrial automation, medicine, traffic control, environmental monitoring, and multi-media and home appliances. The diversified, interdisciplinary expertise of the department revolves around the core topics of the four research units and includes sensor development and manufacturing in micro- and nanotechnology, microelectronics, function-, system-, and circuit integration, communication technology, and modelling/simulation. Current research activities focus on wearables, building automation, smart traffic systems, biomolecular diagnostics, spintronics, metamaterials, thermal sensors, magnetic materials and sensors, hybrid microsystems, physical biosensors, data management and coordination in sensor networks, localization and clock synchronization, security in sensor networks, analytical and numerical modelling, and sensor systems simulation and optimization. In the second part after a summary of the department, an overview will be given on MEMS and OMEMS research activities including electric field sensor and magnetic gradient field sensor.
Dr. Aron Dombovari / CTR
About: Aron Dombovari was born in 1984 (Hodmezovasarhely, Hungary) and received his college degree in chemistry and physics in 2009 from the University of Szeged, Hungary. During and following his university studies he performed his exchange student scholarship at the University of Cagliari (Italy), Department of Chemical Sciences furthermore he worked at University of Oulu (Finland), Microelectronics and Materials Physics Laboratories as a trainee where he became acquainted with nanomaterials. After his studies he spent almost 2 years at a spin-off company as a chemist and product developer. Between 2011-2018 he worked as a research assistant at the Faculty of Information Technology and Electrical Engineering, Microelectronics research unit, at the University of Oulu (Finland). His research has been focused on the synthesis of various nanomaterials, including their chemical, structural and electrical characterization for electronic, sensor and catalytic applications. During his work, he has contributed to several peer-reviewed research articles of nanomaterial applied as building blocks of supercapacitors, gas- or electrochemical sensors, and flexible electrodes. Beside the scientific aspect, he was in charge of training and supervising under- and postgraduate students for chemical processes and measurement techniques.
Houssam Razouk CTR / FH-Kärnten
Abstract: Using generative deep learning models for signal processing of sound waves is the focus of the talk . A new network design is developed to learn the transfer function of a loudspeaker. The transfer function of loudspeakers is learned by a deep generative network using training pairs from the ground truth data and the recorded (simulated) data from the output of the loudspeaker. This network is used to train a second generative network to learn the inverse transfer function of the same loudspeaker and is used to pre-distort the sound wave signal in order to get the optimal performance from the loudspeaker. Caffe-framework with python interface is used to develop and implement the generative deep learning models.
Niosha Navaei CTR / FH-Kärnten
Abstract: A Fluxgate sensor is a magnetometer measuring low magnetic fields based on Faraday’s law of inductance. The planar fluxgate structure is an emerging technology feasible for system integration contrary to it’s bulky 3D counterpart with simple fabrication and low power supply. Recently, a novel structure based on an asymmetric double core layout for improved sensitivity and energy efficiency was proposed. The main aim of this work is, for the first time, to conduct a direct experimental comparison between single- and asymmetric double-core structures of similar geometry. This is achieved by the fabrication of a PCB based sensor structure that can be laid out with single- and double core. Measurements were performed with multiple sensor heads in a static magnetic field within ±150 μT in a Helmholtz coil. Different setups were analyzed with respect to supply current, operation frequencies and sensitivity and compared to each other. The investigation confirms the original conjecture and show that asymmetric double core structure
Dr. Sarah Risquez CTR AG
Abstract: Advances in microfabrication are enabling a large variety of miniaturized implantable systems for health monitoring and deficiency treatments. Today, the new generation of pacemaker called leadless pacemaker is directly implanted on the endocardium within a heart cavity without any lead (e.g. Micra by Medtronics).
However, electrical energy lifespan of the implants (<12 years) and large size of batteries are still a problem. Funded by the European project MANpower (FP7-NMP), the objective of my PhD work was to develop a solution based on mechanical energy harvesting from the heart motion to sustainably power this new generation of pacemaker.
This application imposes several critical requirements in term of size (<1cm³), power output in range (1-10 µW), reliability, durability (>20 years) and compatibility with MRI. This talk will present a 3D energy harvesting microsystem consisting in a spring-mass-type mechanical resonator associated with an electrostatic transducer. Its originality comes from a three-dimensional architecture, whose shape fits pretty well with the cylindrical shape of the pacemaker capsule. The use of the third dimension combined with an original design enables to get a pseudo multiplication frequency effect.
To fabricate this complex three-dimensional microsystem, we developed an additive manufacturing process based on the repetition of three main steps: the micromolding of a structural material (nickel), the electrodeposition of a sacrificial material (copper) and a mechanical planarization of the layer. Identification of imperfections related to the fabrication process and the materials used allowed us to improve the design of the transducer. Moreover, many manufacturing obstacles were overcome through the implementation of dedicated instrumentation. This new process has enabled to fabricate a first three-dimensional prototype of the electrostatic MEMS made of 10 layers of nickel for a total thickness of 200 µm with a minimum in-plane pattern size of 10 µm.
Prof. Dieter Süss, Physics of Functional Materials, University of Vienna
Abstract: Within this talk I will present an overview about a new sensor concept that lead to a significant reduction of noise in tunneling magnetoresistance sensors (TMR) which are used for speed wheel sensors for ABS systems in cars. The development of the TMR sensors is performed in cooperation with Infineon AG which is the main industrial partner. The success of the developed ultra-low noise TMR sensors can be found in its dedicated microstructure and shape. In contrast to state of the art TMR sensors, which show a homogenous magnetization the developed sensors are in a unique topological state. Due to the nature of this topological protected state it intrinsically does not show the noise which occurs in state of the art TMR-sensors. This concept is highly successful in test systems and is currently tested for bulk production by Infineon AG
Omid Sam-Daliri PhD Candidate, School of mechanical engineering, University of Tehran, IRAN Guest researcher at AAU and CTR
Abstract: Nowadays, the employment of adhesives in assembling of similar and dissimilar parts in engineering structures increases considerably. The traditional mechanical fastening approaches, such as bolted and screw joints lead to a stress concentration in the fastening hole which can weaken the joint and cause premature failures. In addition, in metallurgical joints, like the welding joint, defects and residual stresses can be observed around the welding line, induced from heat treatment during the manufacturing process which diminishes the mechanical performance of the welded joint. Hence, adhesive bonding is often used for sensitive structures like in aircraft and naval applications, assembly of tubes in oil and gas industrials, etc. However, a disadvantage of the adhesive joint is its inability to be disassembled for evaluation of underlying damages by nondestructive methods. Non-Destructive Testing (NDT) evaluations are applied for the inspection of adhesive joints, to ensure their integrity after assembly or also used for condition monitoring of the adhesive joints during their service life. Understanding damage in adhesively-bonded joints is further complicated by the difficulty in detecting the onset and progression of joint damage due to delamination or adhesive cracking. The development of strategies for sensing of damage in situ will help to elucidate the initiation and progression of damage and ultimately enable more accurate life prediction and assessment of long-term durability. The emergence of nanotechnology has enabled the tailoring of a variety of functional properties. Recent researches address carbon nanotubes and graphene nanoplates for structural health monitoring of composites, because they have exceptional mechanical stiffness and strength, as well as excellent electrical conductivity and piezoresistivity. In this presentation, we will talk about the results of our experiments which are conducted by the impedance measurement method to analyze the sensing capability of adhesive joints made with carbon nanotube and Graphene nanoplates. Firstly, we will present how to make a smart adhesive with good sensing capability. Then we will use of this adhesive for condition monitoring of single lap adhesive joint and Mode-I fracture energy test (opening mode or DCB test). Also, the correlation between the electrical response and mechanical behavior will be presented. In summary, it has been observed that electrical resistance increases with mechanical strain in single lap adhesive joints due to tunneling effect or contact mechanism on CNT and GNP networks. On Mode-I tests, it has been observed also an increase of electrical resistance with delamination extension along the bonding line. Thus, it is possible to see a clear correlation between impedance response and mechanical behavior for prediction of fracture behavior in SLJ or damage propagation in adhesive joints.
Dr. Adrien Piot CTR
Abstract : A 3 axis gyroscope allows, with a single mechanical structure, the measurement of rotation rates of an object around 3 perpendicular spatial axes. Existing 3 axis microgyroscopes are scarce and typically resonating, made in silicon technology by surface micromachining, use electrostatic transductions and are designed for high volume applications where size and cost are major characteristics. In this thesis we investigated the transduction and fabrication process of a resonating 3 axis microgyroscope having piezoelectric actuation and detection, made in semi-insulating GaAs by bulk micromachining, and with performances potentially much higher than state of the art while limiting the size and cost. This microgyroscope requires a 3D piezoelectric transduction and circuitry which were modelled and optimized to reduce cross-talks effects. An original batch fabrication process was developed, modelled and characterized. This process notably makes use of very deep through wafer reactive ion etching of GaAs in a BCl3-Cl2 plasma. It is demonstrated for the first time that a through wafer highly anisotropic etching of 450 μm deep trenches can be realized owing to etching parameters optimization and the use of a resist masking layer. An original deposition and patterning process of Au/Cr electrodes on the vertical walls of an etched structure by oblique evaporation on rotated substrate through a dry film shadow mask has also been investigated in details. A fine characterization of the crystallographic structure, resistivity and mechanical stress before, during and after annealing of Au/Cr films evaporated under oblique incidence has been performed. Full microgyroscopes with the whole 3D transduction system were realized. Preliminary characterizations of realized gyroscopes by out-of-plane and in-plane optical vibrometry demonstrated promising results. Finally, different ways to improve the design and fabrication process are proposed.
Lisa-Marie Faller Institute of Smart Systems Technologies Abstract Alpen-Adria-Universität Klagenfurt
Abstract: To enable the fabrication of less expensive, light-weight and portable spectrometers, resonantly moving Micro-Electro-Mechanical System (MEMS) mirrors are employed. We show that further miniaturization and increased spectral resolution can be achieved with an inkjet-printed capacitive position sensor with nanometer resolution in a metal 3D-printed package. Very high resolutions of r espos < 50nm as required in, e.g., the spectrometer application, together with a wide necessary measurement range of rm = 1000μm, at an average distance of d0 = 1000μm, additionally motivate the development of a customized analog amplifier chain and the implementation of a laboratory demonstrator: an adaptable, (’all-digital’), Field Programmable Gate Array (FPGA)-based sensor evaluation platform, which is also fully adaptable to other sensing principles. The platform presented for the feasibility demonstration, provides high sampling rates (up to ≈ 100MS/s) and enables generation of trigger signals, i.e. the mirror control signal. It further enables flexible choices of bandwidth and measurement signal frequency, and allows for separation in frequency from coupling parasitics. Noise analysis and stochastic position estimation are applied to analyse and overcome remaining noise limitations and time-dependent uncertainty variations inflicted by the measurement- and system setups. Optimal system configurations and measurement models are determined and analysed using Finite Element Method simulations in combination with numerical optimization. These models, combined with a mirror motion model, are employed in an Extended Kalman Filter to enable nanometer resolution, independent of the measurement bandwidth. Thus, we can demonstrate a way to achieve very high position resolutions with low latency and little to no influence of parasitic stray electrical signals (e.g. the mirror excitation signal uexc = 90V). Measurements are done, using a demonstrator of the inkjet-printed capacitive sensor on a 3D-printed copper housing.
Jürgen Kosel Associate Professor of Electrical Engineering Associate Professor of Bioscience Computer, Electrical and Mathematical Sciences and Engineering Division (CEMSE) King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Saudi Arabia Email: firstname.lastname@example.org
Abstract: Microtechnology and Nanotechnology are rapidly growing fields that provide means for realizing transducer concepts with new capabilities and attractive performance features. Driven by new material developments, fabrication processes or applications, I develop a wide range of novel sensors and actuators, which I will cover in this talk. This includes multi-functional sensors; remotely activated drug delivery; magnetic nanowires for cancer treatment, artificial skins or active cell substrates; flexible graphene sensors for harsh environment applications or flexible magnets for marine monitoring. These new devices provide properties like ultra-low power consumption, minimal size, high performance or flexibility, which are needed for trends like smart living, advanced robots, smart surgeries or wearable devices.
Leonardo Persike Martins CTR / Instituto Federal De Educaҫa͋o, Ciência e Technologia de Santa Catarina
Abstract: A magnetic system demonstrator was developed in partnership with Infineon in order to present the functionalities and characteristics of a novel 3D Hall magnetic sensor. The purpose of this project was to design a magnetic position and orientation system based on only one magnet and one sensor. To do so, the system must be able to detect the magnetic fields when the magnet moves close to the sensor and then estimate the position and rotation of a joystick based on the measured data. Furthermore, a graphical user interface for Windows was developed in order to show the sensor information through charts and visual elements, which can be controlled and navigated with the joystick in a series of demonstrative tasks.
Stephan Mühlbacher-Karrer Joanneum Research Robotics Institut für Robotik und Mechatronik Klagenfurt
Abstract: The demand for robots capable of sharing their work environment with humans in a safe way has increased tremendously in the past decade. Mainly driven by industry, however, not limited to it, the range of applications of such robots enjoys a great variety in work and private life. An essential requirement of those robots is to have a robust and reliable perception to ensure safety throughout the entire operation. Recently, the International Organization for Standardization released the leading safety related technical specification document ISO/TS 15066 for the operation of collaborative robots specifying the guidelines for a human-robot coexistence in the industrial environment. In this talk capacitive sensing technologies (with inkjet printed sensor front ends) as well as tomography approaches utilized for robotic perception will be discussed. The presented reconstruction and detection algorithms are successfully examined in different case studies such as human-robot interaction (where the electrical capacitance tomography is used as contactless control of a serial manipulator) and human-robot collaboration scenarios to enhance the safety of a serial manipulator equipped with capacitive sensors in a shared environment.
Markus Adam CTR / FH Kärnten
Abstract: The focus of the study at hand is set to magnetic speed sensing and the influence of eddy currents on these systems. Magnetic speed sensing is used in many applications throughout different industrial domains like automotive, aeronautic a.s.o.. As there exist different versions of magnetic speed sensors like back bias, with or without pole wheel, they have one thing in common, they have to deal with eddy currents developing in conductive components in the used system geometry, as for example in the lead frame where the sensor is mounted on.
Previous studies by Ortner et al. have shown that eddy currents that develop in thin layers, like e.g. the lead frame of a sensor, can have a positive influence on the magnetic speed sensor signal. While one would in principle expect, that eddy currents always lead to an amplitude reduction and a phase shift it was shown that the sensor - signal can be enhanced by placing electrical conductive components in a way that the eddy current field developing deflects the permanent field in direction of the hall element. This thesis is taking on the work previously done by the fore-mentioned authors. With the help of ANSYS Maxwell Version b16 - 18 the findings of the foregone studies should be verified and taken a step further to identify the key parameters for the eddy current influence on magnetic speed sensor using back bias systems. While the amplitude reduction caused by Eddy Currents could be reproduced, the linear progression could only be reproduced for frequencies above the "reduction start"-frequency.
Desai Pratik CTR / Technische Universität Darmstadt, Germany
Abstract: Since few years, Artificial Neural Networks are heavily used in Computer Vision and Natural Language Processing domain in order to create intelligent applications for smart systems. It has also become an important area of research in Artificial Intelligence. Artificial Neural Networks perform well with specialized accelerated software Frameworks on higher computational resources (e.g GPU) in less constrained environments. But advances in VLSI technology and availability of compact SoC and embedded devices with limited computational resources and less memory limits the use of Multilayer Neural Networks called Deep Neural Networks on low power embedded hardware. Due to the fact that Deep Neural Networks and especially Convolutional Neural Networks are power and computation resource hungry mathematical computations, the new research is developed on optimization of Deep Neural Networks for its efficient inference under limited resource environments without significant loss in its performance. This thesis aims at the research of compression and optimization strategy of Deep Neural Networks that can run efficiently on embedded hardware with more generalized processing techniques. The constraints, requirements and statistical analysis of neural network computation which plays key role in identifying the important facets of compressed neural networks has been presented in this work. Deployability and inference time of Deep Neural Networks on embedded hardware such as smart mobile phones, Raspberry-pi and other FPGAs is fairly important for fast and real time processing for vision based applications. The implementation, evaluation results and analysis of computation time and classification accuracy of standard and newly designed deep neural network architectures has been demonstrated in this work for standard object classification tasks on embedded hardware.
Konstantin Posch CTR / AAU
Abstract: Reliable automatic classification of fruits and vegetables is of great interest for a wide and ever increasing range of applications. However, due to the similarity of the classes in both shape and color the task is considered as difficult and even state of the art deep neural networks are often still not accurate enough. It will be shown how the increased spectral resolution of hyperspectral cameras in comparison to classical RGB cameras can be used to train more accurate models. Deep learning has two major drawbacks. On the one hand, deep neural networks require a huge amount of training data, otherwise they tend to over fit, on the other hand only point estimates are computed. The absence of model uncertainty information through merely computing point estimates makes deep learning of limited use for many fields of application, such as medicine. Both problems are well addressed by using Bayesian statistics. A new approach for training deep nets in a Bayesian way will be presented.
Awan Aoun Amin, Diploma student of CTR
Accurate detection of mechanical vibrations having very high frequencies and extremely small amplitudes, has significant importance in many scientific areas. Among the practical applications of this kind of detection are sub-nanometric characterization of piezo actuators, and the characterizations of Surface Acoustic Wave (SAW) based RF filters, in order to determine their propagation losses. In this master thesis, already existing optics have been extended to measure amplitude of mechanical vibrations on the surface of SAW based RF filter. To achieve this goal, necessary electronics are developed, which take electrical signals from the photodetector of optical interferometer and then extract vibration amplitude information from it.
At the beginning, a study is conducted to get in depth knowledge of SAW devices and already developed optical interferometry set-up. The requirements of electronic detection system are specified, according to the specification of the photodetector. In the next stage a basic concept is developed, to build this system based upon a comparative study of different RF receiver architectures. This concept named Low-IF receiver architecture acts as a baseline for the next design phase, in which this receiver is going to be a major part of complete electronic detection system. The design process included finalization of the overall structure of the receiver chain, and selection of all hardware and software components.
Additionally this structure and components are analyzed according to the requirements. The hardware and software implementations are done in different stages. Initially, receiver chain and components are analyzed theoretically using software tools like ADISimRF, diamond plots and spread sheets. In the next stage the circuit implementation on hardware is tested using signal generators, spectrum analyzer and NI supported modules. The complete system incorporating both optics and electronics is then tested, using LabView based software, with specific tests defined exclusively for critical analysis of this application. Finally, test results prove that, the RF receiver can measure signal amplitudes in the complete required range of -80 dBm to -140 dBm , with an accuracy close to 100%. Also the precision in measuring vibration amplitudes is in acceptable limits and the electronic detection system can easily support measurements as low as 1 pm.
The overall system has proved to be fast enough to satisfy the million measurements per day requirement, by completing a single measurement in less than 86 msec. Because of LabView, the system also supports automation for the upcoming task of moving the SAW surface, to characterize multiple points
Wolfgang Mühleisen, CTR
A power plant in the south of Austria built with multi-crystalline PV modules was investigated after a hail storm. Standard measurement techniques like thermography, electroluminescence and ultraviolet fluorescence were used. It was found out that glass broken modules were not only responsible for a loss in power and yield. The remaining good-looking modules had invisible to the eyes cell damages causing the loss. Because of done measurements and documentation of impressive findings, the insurance decided to change the most affected bad working modules subsequently.
Anna Ermakova, CTR
Due to the high thermal and chemical stability wide bandgap materials such as diamond and silicon carbide attract more and more attention. From one side such materials are interesting for electronics. Since they can find a lot of applications in harsh environment. From another point of view they are good matrixes to „freeze“ single atom system at room temperature, which can be used for quantum computing and not only. I am going to discuss one atom-like point center in diamond – nitrogen-vacancy (NV) defect. It is optically active center with non-zero spin. NV center can be used as an optical marker for biological systems, due to nontoxicity and high biocompatibility of diamond. Also it can be used for magnetic field detection, including high sensitive NMR measurements.
Thomas Söllradl, CTR
Evanescent-field based methods such as surface plasmon resonance (SPR) have been used very effectively for label-free imaging of microscopic biological material in close proximity to a sensing surface. However, the shallow probing depth of SPR (typically less than ~200 nm) can be problematic when imaging relatively thick biological objects such as cells or bacteria. In this paper, we demonstrate how metal-clad waveguides (MCWG) can be used to achieve deeper probing depth compared to SPR while maintaining good imaging spatial resolution. Comparative numerical simulations of imaging spatial resolution versus probing depth are shown for a number of common SPR, long-range SPR, and MCWG configurations, demonstrating that MCWG offer the best compromise between resolution and depth for imaging thick biological objects. We demonstrate the potential of this approach by monitoring intracellular activity following the activation of apoptosis in individual cells exposed to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and by visualizing and quantifying extracellular changes in endothelial cell layer integrity following the activation of the proteinase-activated receptor 1 (PAR1) by thrombin.
Ulrich Pöschl, Prof. Dr., Director of Max Planck Institute for Chemistry , Mainz/Germany
Multiphase chemistry deals with chemical reactions, transport processes and transformations between solids, liquids and gases. These processes are important for Earth system science and climate research as well as for life and health sciences. In Earth system science and climate research, the focus of our department is on studying biological and organic aerosols, aerosol-cloud interactions and atmosphere-surface exchange processes. Concerning life and health sciences, we investigate how protein macromolecules are modified by air pollutants and how this affects allergic reactions and diseases. We try to elucidate the course of multiphase processes at the molecular level and its impact at the macroscopic and global scales. With regard to scientific publishing and communication, we promote open access for efficient dissemination and re-use of scientific knowledge, and multi-stage open peer review for efficient quality assurance through transparency and self-regulation. Further information:
Ying Ma, CTR
Wafer Level Packaging (WLP) based on redistribution is the key technology which in evolving to System in Package and Heterogeneous Integration by 3D packaging using TSV. Materials and process technologies are key for a reliable WLP. It’s not only the choice for the right polymer or metal but the interfaces could be even more critical like Under Bump Metallurgy (UBM) or the adhesion of polymers. In my presentation, I would like to share my experience in the field of WLP, including UBM process, wafer level bumping and flip chip assembly.
Thomas Moldaschl, CTR
Over the last years it has become easier and easier to realize full Quantum mechanical systems in the lab, often without the requirement for ultra-cold and ultra-clean environments. Today there are many proposals for practical QM applications, many of which have been implemented so efficiently that they have reached an industrial level.
At the same time we are at a point where several CTR employees have a QM background. To tap this vast potential of possible future research and funding strategies, our colleague, Thomas Moldaschl, has taken it onto himself to investigate QM applications for sensing technologies. He will present his findings and ideas at the next meeting of the CJC to initiate thought and discussion aiming at the realization of a future CTR Quantum sensor.
Prof. Jürgen Wilde, IMTEK, Albert-Ludwigs-Universität Freiburg
Die Aufbau- und Verbindungstechnik (AVT) verbindet die "Siliziumwelt" des Mikrosystems mit der Systemebene. Die AVT als Lehr- und Forschungsgebiet umfasst die Methoden, Verfahren und Technologien zur Herstellung der Hardware auf den Systemebenen oberhalb des eigentlichen Funktionselementes. Sie hat dabei folgende Aufgaben:
AVT hat insgesamt maßgeblichen Anteil an Kosten und Wertschöpfung elektronischer Systeme, und beeinflusst in hohem Maße Baugröße, Gewicht, elektrisches und thermisches Verhalten sowie die Zuverlässigkeit eines Gesamtsystems. Die Lebensdauer kann durch das Aufbaukonzept, durch optimierte thermische und thermomechanische Auslegung sowie durch eine geeignete Werkstoffauswahl und angepasste Herstellungsprozesse entscheidend verbessert werden.
Die AVT stellt somit in der MST ein sehr breites und vielfältiges Feld dar, mit Aktivitäten in Forschung und Lehre auf den folgenden Teilgebieten:
Prof. Dr. Maria Kufner, Coburg University for applied sciences
The institute of sensor and actuator technology (ISAT) of Coburg University of Applied Sciences and Arts in Coburg was founded in 2006. Its research and development activities primarily have been focused on surface acoustic waves, meanwhile supplemented with integrated optics and microfluidics. The topics cover a variety of application areas, such touch sensitivity, non-invasive detection of depositions, coatings or biofilms, non-contact detection of material properties, intelligent condition monitoring, data monitoring. The actuator developments comprise haptic feedback, spray generation, coagulation and mixing of fluids, as well as the acceleration of microscopic transport processes via surface acoustic waves, for example in electro-polishing or charging batteries.
Kumar Nithin, CTR / Coburg University of applied sciences
In order to develop a fully CMOS compatible CO2 micro gas sensor based on evanescent field absorption in the mid-infrared, it is essential to first characterize separately the various components of the sensor: the optical waveguide structures, the light source and the detector. The experimental results provide a feedback for the design and fabrication steps, and can be used for the design of improved structures. First, the presentation will give a short introduction about the sensing principle and the experimental methods employed for the optical and electrical characterization of the sensor components. Second, the results of the characterization will be presented, with focus on: (1) Optical characterization of losses in slab waveguide structures. (2) Electrical characterization of the on-chip light source and detector. Finally, a first proof-of-principle measurement of CO2 from structures containing both electrical and optical elements will be presented.
Dr. Roland Waldner, PHILIPS Health Tech
Roland Waldner studied plastics engineering and innovation management at the university of Klagenfurt. He is currently the head of “Advanced Development and Patents” at PHILIPS Health Tech working on innovation management, i.e. invention disclosures, patent applications as well as with project funding application.
Abasahl Banafsheh, CTR
Plasmonic nanoantennas are a versatile group of plasmonic structures with a peculiarity of being the interplay between the far-field and the near-field. As the properties of the nanoantennas are firmly tangled to their shape and dimensions, they can be engineer in order to achieve desired functionalities. In my presentation, I will give a short introduction to surface plasmon polaritons and plasmonic nanoantennas, then I will represent an equivalent circuit model in order to conceptualize the functionality of these structures. At the end, I will introduce new families of plasmonic antennas such as circularly polarized antennas, multi-layered antennas, gap-loaded antennas and horn antennas in the visible regime.
Dr. Jan Steinbrener, CTR
X-ray Diffraction Microscopy (XDM) has been gaining in popularity for nanoscale imaging of biological and material science samples. Its high penetration depth (compared to electron microscopy) and its good dose efficiency (compared to its lens-based X-ray alternative) make it uniquely suited for imaging whole biological specimens, where radiation damage is a concern. From a recorded diffraction pattern, the complex exit wave of the object can be recovered using an iterative reconstruction algorithm. In addition to structural information, the resulting data contains depth information of the object along the 2D projection and quantitative phase information. The extension to 3D imaging is straightforward and allows for element-specific reconstruction of the complex object function.
With the advent of X-ray lasers with high power pulses in the femtosecond regime, the technique can be extended to even the most radiation sensitive samples (such as micro-crystals), as the diffraction pattern can be recorded before any structural changes due to radiation damage occur (diffract then destroy). Results of the imaging of yeast cells (freeze-dried and frozen-hydrated) as well as structure determination of micro-crystals using a free-electron laser will be presented.
Markus Leitgeb, TU Vienna
The preparation of porous silicon carbide (SiC) layers with wet chemical etching methods from single crystalline SiC wafers is presented. In particular, photochemical and photoelectrochemical etching techniques are studied and evaluated for SiC.
Photochemical etching is achieved with the deposition of platinum electrodes on the surface of SiC and the subsequent exposure of the wafer to an etching solution. Both UV irradiation as well as an oxidant are necessary for etching. The resulting porous layers show light interference effects when investigated optically as well as a reorganization of the porous structure when exposed to high temperatures. Therefore, application scenarios of this approach could be in the field of pressure or optical sensors and are discussed.
Photoelectrochemical etching utilizes an external power source to initiate the formation of a porous layer. The homogeneity of the porous layers is increased by combining photoelectrochemical with photochemical etching. A possible application scenario of porous SiC multilayers in optical sensors is presented.
Thomas Moldaschl, CTR
The increasing interest in low dimensional semiconductor nanostructures hosting excitonic or spin qubit carriers leads to the investigation of decoherence mechanisms that are a direct or indirect consequence of light-matter and matter-matter interactions in the semiconductor matrix. Mechanisms are portrayed and possible solutions are presented.
Claude Humbert, Supméca Paris
In the frame of telecommunication, surface acoustic waves (SAW) are used to transport information in Radio-Frequency filters (microsystems able to filter an antenna signal). As such filters deal with very low energy (less than 1 mW), it is preferable to prevent any energy leakage during the SAW propagation. Dr Pascal Nicolay and Hugo Chambon wish to understand the causes of such losses in order to optimize these filters. That’s why I had to design and set up an optic device (interferometry) able to measure, with high accuracy and resolution, the amplitude of small wavelength SAW. Of course the CTR could also use it in the future for any other application involving a surface vibration amplitude measurement.
Antoine Caillard, Ecole Nationale Supérieure d´Ingénieurs du Mans (ENSIM)
Nowadays, a lot of consumer products include microelectromechanical systems (MEMS) in order to answer the constant need to reduce the size of products. For example, cellphones include many MEMS like microphones, accelerometers or gyroscopes. The market is principally focused on pressure sensors and microphones and so, the challenge is to improve the quality while reducing the size of these sensors. When it comes to microphones, the classical way to deal with acoustics, based on the wave propagation equation, is no more accurate because the thermal and viscous effects that appear on the boundaries are not taken into account. This presentation will demonstrate why it is primordial to use the Navier-Stokes equations to accurately describe the phenomena that are appearing when the thermoviscous boundary layers size is of the same magnitude order than the characteristic lengths of such sensors (millimeters). A simple analytical solution will be confronted to the simulation results obtained with COMSOL, with and without taking into account these diffusive effects and, finally, the study of a MEMS microphone will be presented.
Margret Leibinger, IMTEK, Universität Freiburg
The broad field of personalized medicine has been becoming more and more important in recent years, but as it is still in its infancy many challenges are to be mastered. One goal of personalized medicine is to determine the exact amount needed of a drug, which varies amongst individuals because metabolism of drugs happens at a different pace in each individual due to different amounts of enzymes present in our liver. For this application a microfluidic measurement chamber was developed that enables a continuous fluid flow as well as the integration of electrodes for electrochemical detection of the concentration of a substrate in a sample fluid. The design of the biosensor was evolved allowing a maximum amount of the sample fluid to get in direct contact with the enzymes immobilized on the working electrode while also respecting the constraints of additive manufacturing techniques at the same time. The electrodes are inkjet-printed using silver ink for the reference electrode whereas graphene ink is used for the working- and counter electrodes. The fluid flow through the measurement chamber was simulated and characterization of the electrodes is being done.
Alexander Stadler, FH Vorarlberg
One of the most important components in smartphones is the microphone. The microphones are optimized for room temperature. If the temperatures change, the quality of the sound will decrease. The main target of this work is finding a design for the compensation structure, which is able to compensate the thermal effects and, to know about the stresses in the structure. To understand the sound quality it is necessary to develop a small tool to calculate the compliance.
Bruno Spricigo, Federal university of Santa Catarina
Electronics and control are continuously growing subjects in the automotive industry. The development of new technologies to reduce consumption, increase comfort and handling are the number one priority of many manufactures. Various systems that make nowadays vehicles more secure like TCS (Traction Control System) and ESP (Electronic Stability Program) rely on sensing several variables like individual wheel speed and suspension displacement to compare it to an analytical model and decide if action is needed or not. The main target of this work is to propose a smart use of a new 3D magnetic sensor to improve the quality and precision of the suspension displacement measurement and, because of the greater capabilities of the sensor, detect the steering wheel angle at the same time. The mechanical and magnetic implementations are discussed in detail.
Bettina Findenig, Fachhochschule-Kärnten, Villach (Systems Engineering)
Wireless sensor nodes are usually powered by batteries or accumulators, which have a limited operation time and need to be recharged. Energy harvesting therefore offers the possibility to supply a system with freely available energy for making it autark. This work presents current approaches of using energy extracted from the environment to power microelectronic devices. In the first part the main focus is, to determine the amount of energy produced by different energy harvesters using measurements. As a second step, the operation of a micro energy harvesting system is explained and has been tested with a laboratory demonstrator. This demonstrator has been redesigned for an internal demo system of a micro energy harvesting system which shall visualize the effectiveness of the harvesters.
Hugo Chambon, Université technologique de Compiègne, CTR
IDT-based acoustic devices use electro mechanic coupling in piezoelectric media to excite propagating waves. Due to the sensitivity of media's wave velocity to temperature, stress and mass loading, these acoustic devices are used as sensors. Such acoustic devices enable passive and wireless detection making them especially good candidates for sensing application in harsh environment. However, the design of acoustic wave sensors is highly iterative because of the large number of parameters to be optimized in addition to the complex electro mechanic interactions.
To shorten development time, several numerical and analytical methods have been developed. The model we present here is based on Finite Element analysis. Because of the high aspect ratio of the geometry, a complete FE simulation of the device would be very time consuming, therefore using the periodicity of the structure, the model is simplified (reduced) to a single pair of fingers. This model enables to compute the harmonic admittance and extract parameters that are used afterward to simulate actual devices.
Prof. Hubert Zangl, Institut für Intelligente Systemtechnologien, Alpen-Adria Universität, Klagenfurt
More than 100 years after the first use of capacitive sensing principles, capacitive sensors are found in billions of products for various applications. As the actual sensor elements are just (more or less) conductive areas, they are of unparalleled simplicity and they can be realized by a variety of manufacturing technologies and materials. While used to cover rather large spatial areas e.g. in touch screens in mobile phones or as replacement of mechanical switches in cars and home appliances, the principle is also used in miniaturized microelectromechanical devices, e.g. in pressure, force and acceleration sensors or for the detection of chemical substances or biological cells.
As capacitive sensor exhibit sensitivities towards many physical parameters they find wide applicability. However, the sensitivity towards many parameters also implies that cross-sensitivities to may be a major concern. Thus, in order to design robust and accurate sensors, the entire chain starting from the electrode topology over the analog measurement circuitry up to the signal processing algorithms used to determine the parameter of interest from the measured capacitances has to be considered. Consequently, the present talk will provide an overview of this entire chain and specifically address reconstruction algorithms (including Electrical Capacitance Tomography) as well as the design strategies for electrode topologies.
Prof. Johannes Bernardi, USTEM, TU Wien
Biography: Prof. Bernardi studied at the technical university of Vienna. He soon became interested in analytical electron microscopy and during the following years be became engaged in the preparation and microstructure and properties of magnetic materials in the workgroup of Prof. Fidler. During the diploma study about "TEM investigations of Sm-Co 2:17 magnets" he gained experience in that field by industrial training at Treibacher Chemischen Werken and at Magnetfabrik Thyssen in Dortmund.
He was employed as research assistent at the Institute of Applied and Technical Physics, for the BRITE/EURAM project "Analysis of Coercivity and the Microstructure of High-Tech Hard Magnetic Materials" during PhD. Besides microstructural investigations, another main task was the installation of a powder metallurgical lab at the institute. The thesis entitled "Microstructure and Coercivity of Rare Earth - Iron Permanent Magnet Materials" was finished 1993.
After that he moved for two years to USA as an Erwin Schrödinger research fellow. He worked at the Department of Materials Science and Engineering, University of California, Berkeley, and the National Center for Electron Microscopy(NCEM), Lawrence Berkeley with Prof. Gareth Thomas, a pioneer in the field of transmission electron microscopy. During that research visit he investigated single-domain nanophases for GMR applications by high resolution TEM.
Returning to Europe he was employed as a guest scientist at the Institut für Festkörper- und Werkstofforschung in Dresden working on structural investigations of permanent magnet materials until he came back to Vienna University of Technologys in 1996 engaged in the BRITE/EURAM III Projektes "EMERGE".
1998 he became employed as a reasearch assistent in the electron microscopy group at the Institute of Angewandte und Technische Physik, Vienna University of Technology. He was strongly involved in the preparation for the foundation of the service centre USTEM, which was established in 2000 under the guidance of Prof. Schattschneider. 2001 he was assigned to USTEM as a university assistent.
2006 he became head of USTEM.
Mathias Kremer, PhD Student, CTR und Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology (IMT)
Highly reactive integrated material systems have recently gained attention, as they promise a feasible tool for heterogeneous integration of micro electromechanical systems (MEMS). As integrated energy sources they can be used to join heterogeneous materials without applying too much thermal stress to the whole device. Our new approach comprises a single layer of a reactive nanocomposite, made of intermixed metal nanoparticles, instead of multilayer systems. In this study we will present the development of the reactive nanocomposite from choice of materials through processing steps, handling and application methods and eventually the results of our experiments upon the reactivity of the nanocomposites and the feasibility for bonding applications.
Andreja Petrovic, Master Student, University of Ljubljana, Faculty of Chemistry and Chemical Technology
Although enzyme-based electro-chemical bio-sensors show significant potential towards the construction of a sensitive and selective sensor, a direct quantitative detection of the enzyme’s catalytic activity still remains challenging. Distinct properties of the enzyme are required as well as an electrode in order to enhance the direct electron transfer (DET) between the enzyme’s catalytic active site and the electrode.
Enzymes that contribute to these requirements are the cytochrome P450 enzymes (CYPs) that comprise for about 80% of the phase-I drug-metabolizing enzymes in the human liver. The isoenzyme cytochrome P450 2D6 (CYP2D6) is responsible for the metabolisation of 25% of all clinically prescribed drugs; therefore the interaction potential of xenobiotics with this isoenzyme is of utmost importance. Due to the fact that the CYP catalysed metabolisation reactions are electron dependent oxidative processes, CYPs are suitable candidates for the construction of a small-scale bio-sensor.
In our study, a screen printed working electrode with an additional carbon nanotube (CNT) layer was used for the immobilisation of the CYP2D6 enzyme. Two fundamentally different immobilisation techniques were investigated: (i) non-covalent immobilisation and (ii) covalent immobilisation, where either physical interactions or direct chemical bonds were exploited for the stable and electronically efficient connection between the enzymes and CNT electrode. The immobilisation was characterised by testing the activity of the enzymes through enzymatic demethylation of a model substrate, i.e. dextromethorphan, before and after an intensive wash of the working electrode. The concentration of the substrate and its product, i.e. dextrorphan, were determined using a high-performance liquid chromatography (HPLC). The stability, selectivity and sensitivity of the biosensor were further evaluated using a cyclic-voltammetrical processing of the induced signal.
Mohssen Moridi, MST Area manager, CTR
Mohssen Moridi obtained his master’s degree in micro engineering from École Polytechnique Fédérale de Lausanne (Switzerland), where he also received his PhD in microsystems, in 2005 and 2011, respectively. After a postdoctoral period at EPFL, in 2012 he joined the Microcity research centre in Neuchatel (Switzerland) as a senior scientist to supervise and work on several projects to develop new MEMS sensors in collaboration with industrial partners and academic institutes. He worked on developing different kind of sensors such as optical detectors, magnetic sensors, integrated silicon amorphous photodiode detectors, ASIC post processing sensing devices, biomedical devices, microfluidic, hybrid and Lab-on-a-chip sensors. His more than 10 years of working experience with microsystem technology and cleanrooms gives him a broad knowledge and expertise with many sensing technologies, microfabrication, process development, and device characterization. Recently he joined CTR as the head of the Microsystems Technologies department.
Prof. Dr. Miran Čeh, Department for Nanostructured Materials, Centre for Electron Microscopy and Microanalysis, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
Various Scanning Transmission Electron Microscopy (STEM) imaging techniques (ADF, HAADF, ABF) have become extremely useful for materials characterization at the nano- and atomic scale, particularly due to recent developments in the correction of spherical aberrations of the (S)TEMs microscope lenses. The main principle underpinning these imaging techniques is that the detectors are designed in such a way that they mostly collect high-angle scattered electrons, thus minimizing the contribution of elastically scattered electrons to the image. As a consequence, the intensity of the atom columns can be correlated to the chemical composition, or in case of annular bright-field STEM imaging, the light elements can be observed. This lecture will present an overview on the basic principles of STEM imaging techniques. The results of qualitative and quantitative STEM imaging at the nano- and atomic scale will be presented and commented on for various oxide ceramic materials.
Franz Josef Maier, TU-Wien, Institute of Applied Physics
Since CO2 has gotten a lot of attention in the past (climate change for example), there is a lot of interest in reducing the size and cost of CO2 sensors and subsequently allow a mass production of these sensors. As semiconductor technology allows for a realization of these requirements, a project was initiated by Infineon. A team at the JKU-Linz, led by Prof. Jakoby, made the theoretical design of this sensor. The working principle of these sensors is the absorbance of the evanescent field of a sub-wavelength waveguide, as I will explain in the talk. Part of my thesis was the design of a test bench used for an optical and electrical characterization of the waveguides and measurements of the absorbance of CO2 and Chloroform with the waveguide sensors. I will also talk about advantages and disadvantages of the waveguiding technology and give a future outlook on the project.
Dr. Giulio Manzoni, Microspace Communications Cooperation, Managing Director
Spacecraft miniaturization is a popular trend since over a decade and has grown from University exercises to fully performing satellites with commercial value. Challenges and successes will be discussed in particular for the application on remote sensing. The results of the two satellites POPSAT and ATHENOXAT, developed to demonstrate micropropulsion attitude control, formation flight capability, day and night vision on medium-high resolution will be presented.
Assoz. Prof. Dr. Manfred Hartbauer, Institute of Zoology, Karl-Franzens-Universität Graz
Extracting the information about impending collisions from the visual scene viewed from the ego-perspective of a fast moving agent is a challenging task that is solved in an efficient way in locusts flying in swarms of million individuals. Rapid luminance changes in adjacent receptors lead to the excitation of motion-sensitive layers that are connected to neurons selectively responding to impending collisions. This was simulated in a bionic computer model where the collision risk is extracted from traffic movies exhibiting a low spatial resolution. This method relies on relative object expansion and is therefore independent of distance measurements and object recognition. Additionally, the calculation of directional motion information can be used to compute the direction and force of evasive steering. Camera shaking and quickly approaching ground shadows are partially compensated. After parameter tuning, simulation results show that this method reliably indicates impending collisions and, if possible, an evasive steering direction using various crash car movies as input.
The problem for camera sensors used in dark conditions comes with noise that is amplified after application of common image enhancement procedures. Therefore, the second part of my talk addresses the night vision capabilities of the solitary bee Megalopta genalis (Greiner et al. 2004). The way eyes of this bee cumulate photons by simultaneously maintaining spatial and temporal resolution already inspired the development of innovative night vision cameras. Recently, I developed an iterative procedure that increases grey value saturation by simultaneously reducing sensor noise. Image blur is prevented by 'adaptive spatial averaging'. Additionally, temporal summation of grey values using static images as input was made possible by modelling saccadic eye movements. In both computer models most processing steps can be performed on the sensor thus computational demands can be minimized.
Wasif Kahn, M. Sc. Student, Computational Mechanics, Universität Duisburg Essen
During the manufacturing, thin slender Si wafers are coated with thin metal layers at high temperatures. When this composite is cooled down to room temperature, stresses are developed due to different thermal expansion coefficients of silicon and metal, leading to the deformation of the wafer. The aim of this master thesis is to develop and validate the appropriate modelling approaches for this classical thin-film-on-substrate problem for thin slender Si wafers using FEA program ANSYS.
Stoney's approach is modified for circular plates with anisotropic substrates subjected to thermal mismatch for the purpose of theoretical calculations. Further, considering the limitations of Stoney's approach, an analytical approach is developed based upon large deformation theory to predict the behaviour of thin slender wafers. In order to calculate the curvature from FE results, two analytical approaches based upon least square method and second order differential approximations are developed in program MATHEMATICA.
The problem is solved in two subsequent steps. In the first step, a moderately thick plate is analysed for isotropic and anisotropic substrates. Several modelling approaches based upon varying element types, element sizes, contact formulations and number of timesteps are examined in this step. In the second step, this study is extended to the thin slender wafers and studied in different regimes of in-plane film stress - curvature relationships. Bifurcation phenomenon, an important characteristic of geometrical nonlinearity is also examined.
The limitations of Stoney's approach for large deformations are mentioned. Analytical approach based upon large deformation theory is found to be serving a strong base for the purpose of comparison of FE results. The use of layered shell elements for anisotropy, large deformations and optimum calculation efforts is also examined.