Microwave Tunability with ferroelectric thin films
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Microwave Tunability with ferroelectric thin films
Fri, 17/06/2016 - 13:30 to 14:30
Location:
Speaker:
Dr. K.C.James Raju
Affiliation:
Professor at CASEST (Centre for Advanced Studies in Electronics Science & Technology), School of Physics, University of Hyderabad
Synopsis:
Tuning of microwave circuits is an important emerging requirement as for example 5G mobile requires a handset to have about 70 radios. It is not practical to have that many independent circuits and hence it is necessary to reconfigure a few circuits in to a number of other by tuning the circuit elements. In ac circuits, R, L and C are the variables and among them only L and C can give tuning without loss. But L is not amenable for miniaturization. That leaves C to achieve tuning in miniaturized circuits which is achieved by varactor diodes, RF MEMS or by exploiting the variable dielectric constant exhibited mostly by ferroelectrics in their paraelectric state and a few similar materials. This talk will cover the basics of such materials, their growth as thin films, their measurements in the microwave frequency range, processing- property correlations and the tunable capacitors made with them as well as the circuits that employ them. In addition, some of the other microwave materials developed and the microwave measurement techniques being used for them and the sensing potential with some of these materials will also be introduced.
Biography:
K.C.James Raju is a Professor at CASEST, School of Physics, University of Hyderabad working in the areas of materials, phenomena and devices in the microwave frequency range. The materials suitable for microwave range applications are prepared in bulk, thin film and nano particle form. They are mostly ferroelectrics, multiferroics, high K dielectrics and high temperature piezoelectrics. The phenomena being explored in the microwave range include tunable microwave dielectric properties, low loss behaviour in some high k materials, ferroelectric domain kinetics, dielectric relaxation, interaction between transport and dielectric behaviours, multi ferroicity, magnetism in nano ferroelectrics and loss mechanism in microwave absorber materials as well as studies on the crystallization kinetics in materials and films processed under microwave or laser energy. The devices being explored for microwave applications are Dielectric Resonators (DR), planar microwave dielectric resonators and filters in LTCC technology, FBAR and HBAR using piezoelectric thin films, tunable microwave devices using ferroelectric and non- ferroelectric thin films and application of functional materials like ferroelectrics in MEMS based devices for microwave and energy harvesting applications. The microwave measurement techniques that are being used in the lab for materials include waveguide based techniques for bulk, liquids, powder and thin films, free space propagation techniques, Extended cavity perturbation technique for thin films, Resonator based techniques for low loss materials used for DRs, Split Post Dielectric Resonator technique for substrates and thin films at spot frequencies, On wafer probing techniquies like circular patch capacitor technique, calibration comparison technique, modelled planar IDC based technique, multiline calibration technique for tunable thin films and techniques for ferrites and multi ferroics.
The thin films are being processed by sol-gel process, RF sputtering and Pulsed Laser Deposition technique. Another technique being followed is low temperature deposition of thin films followed by crystallization with microwave annealing. Exploration of these materials and phenomena are now being extended to the THz frequency domain.