BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Memento EPFL// BEGIN:VEVENT SUMMARY:IMX Seminar Series - Microsonics for communication and sensors DTSTART:20191209T131500 DTEND:20191209T141500 DTSTAMP:20260609T100638Z UID:0ff53ad7169795241310ae60db233c0b38dcaac0a7d1b66a2ca3decf CATEGORIES:Conferences - Seminars DESCRIPTION:Prof. Paul Muralt\, EPFL Switzerland\nMicrosonics has emerged as field in microsystems technology dealing with ultrasonic applications. Considering that typical sound velocities in solids are ranging from 4’0 00 to 10’000 m/s we conclude that a wavelength of a micrometer correspon ds to frequencies of 4 to 10 GHz. This means that mechanical resonators wi th micrometer dimensions resonate in the lower GHz frequency range\, the s ame range as the transmission bands of mobile telecommunication (between 0 .4 and 3 GHz). Of course\, we need a link between wireless transmission ba sed on electromagnetic waves\, and the ultrasonic waves in microsonic devi ces. The required transformation is provided by piezoelectric materials\, either as single crystal or as thin film. Modern mobile communication owes its existence indeed to piezoelectric materials\, because only electromec hanical resonances in selected piezoelectrics yield high enough quality fa ctors within reasonably small dimensions.\nThis talk focuses on piezoelect ric thin film resonators\, which in the simplest configuration are just th ickness mode vibrators. We note again that a typical thin film thickness f its well the required half-wavelength thickness for communication bands in the lower GHz frequency bands. Microsonics developed in parallel to mains tream MEMS technology\, focusing on integrating piezoelectric films\, and improving dimensional precision. There are of course very high requirement s as to the quality and stability of such films. The best material found s o far is AlN\, having a correct size of piezoelectric coupling\, a large m echanical quality factor\, and also a good thermal conductivity\, which is important for filters in the transmit line to support the power in the se nding mode. With the discovery of the extraordinary increase of piezoelect ricity when alloying non-piezoelectric ScN into AlN by a Japanese group\, the field got a new thrill. The larger piezoelectric coupling allows for l arger communication bands\, satisfying better the ever-increasing need for higher bit rates.  Moreover\, other types of resonators having inherentl y lower coupling factors than the simple devices exploiting longitudinal b ulk waves become now also interesting.\nThe talk will address some growth and microstructural issues in Al(1-x)ScxN thin films. The piezoelectric wu rtzite phase is in fact a metastable phase\, and its growth in a polarly o riented microstructure at relatively low temperatures (300 °C) is a typic al achievement of sputter deposition. Nevertheless\, there is a certain ri sk to obtain misaligned grains that are thought to be caused by secondary nucleation of ScN rich\, nanometer sized rocksalt within grain boundaries at the surface of the growing wurtzite film. On the acoustic side we shall speak about a breakthrough in Lamb wave devices\, for which a larger qual ity factor was achieved when having the wave-carrying plate not freely sup ported\, but isolated by an acoustic Bragg mirror structure. Finally\, ano ther novel device is presented\, a 3D machined micro transducer that coupl es bulk waves generated in periodic pillars into a surface wave that is tr avelling away on the substrate surface. When combined with a reflector gri d at some distance\, the wave comes back into the transducer and is detect ed as echo. Knowing the temperature coefficient of the surface wave\, the travelling time reveals the temperature of the device. A wireless coupling between transducer and an antenna enables then a wireless temperature rea dout up to 600 °C in experiment\, with prospects to reach 800 °C.\n\nBio : Paul Muralt is professor at Swiss Federal Institute of Technology EPFL a t Lausanne\, Switzerland. He leads a group working in electroceramic thin films within the Materials Science Institute\, studying particularly piezo electric and solid ionic MEMS and NEMS devices. Having a background (PhD) in solid state physics\, he moved more and more into thin films\, surface\ , and materials science for micro and nanotechnology. In his professional career he was working at the Swiss Federal Institute of Technology ETH\, t he IBM Research Laboratory in Zurich\, the Free University of Berlin\, and in a thin film coating industry (Balzers) before joining the Ceramics Lab oratory at EPFL in 1993. His PhD studies dealt with incommensurate crystal line phases in an organic-inorganic layered perovskite structure. As a pos t-Doc\, he pioneered scanning tunneling potentiometric imaging. Today\, he is particularly known for his works in processing\, characterization and applications of piezoelectric and pyroelectric thin films such as PbZrTiO3 and Al1-xScxN\, including also works on materials integration\, micro mac hining\, and device physics. He teaches thin film deposition\, micro and n ano structuration\, surface analysis and introduction to ceramics. He auth ored or co-authored over 250 scientific articles. He is IEEE Fellow\, rece ived the outstanding achievement award of the International Symposium of I ntegrated Ferroelectrics (ISIF) in 2005\, and the C.B. Sawyer award from t he IEEE International Frequency Control Symposium in 2016. He acted as co- chair of the MRS spring meeting 2008\, co-organized MRS and E-MRS symposia \, served in program committees of the International IEEE Symposium on App lications for Ferroelectrics (ISAF) and ISIF conferences\, and of the Euro pean Meeting on Ferroelectricity (EMF). He was co-founder of the Internati onal Workshops on PiezoMEMS (IWPM) in 2010. He was an IEEE distinguished l ecturer in 2017. In 2019\, he was general chair of the joint meeting inclu ding ISAF\, EMF\, the International Conference on Electroceramics (ICE)\, IWPM\, and the Workshop on piezo-AFM (PFM).\n  LOCATION:MXF 1 https://plan.epfl.ch/?room==MXF%201 STATUS:CONFIRMED END:VEVENT END:VCALENDAR