000202048 001__ 202048
000202048 005__ 20181205220337.0
000202048 0247_ $$2doi$$a10.5075/epfl-thesis-6375
000202048 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis6375-8
000202048 02471 $$2nebis$$a10249190
000202048 037__ $$aTHESIS
000202048 041__ $$aeng
000202048 088__ $$a6375
000202048 245__ $$aPZT thin films for MEMS devices$$bfrom in-situ sputter deposition to energy harvesting device
000202048 269__ $$a2014
000202048 260__ $$aLausanne$$bEPFL$$c2014
000202048 336__ $$aTheses
000202048 502__ $$aProf. K. Scrivener (présidente) ; Prof. P. Muralt (directeur) ; Dr E. Defay,  Dr T. Maeder,  Dr R. Mamazza (rapporteurs)
000202048 520__ $$aThe recent progress in synthesis and integration of highly piezoelectric lead-zirconate-titanate (PZT) thin films onto silicon substrates are paving the way for new, more efficient and faster devices in micro electro-mechanical systems (MEMS). In comparison to competing principles, piezo-MEMS devices need less power and are faster than thermally actuated devices, and work with lower voltage than electrostatic actuators. Within the frame of the development of mass production routines for the microfabrication of piezo-MEMS devices, there are several bottlenecks to be solved. Among them, the most relevant one is represented by the need of a high-quality, high-throughput PZT thin film deposition route. The popular sol-gel method results often in satisfactory performance in terms of piezoelectric activity, but the lack of automation makes this deposition method unsuitable for a large-scale production. Magnetron sputtering is instead a high-throughput and reliable technology, but high-performing PZT thin films are not straightforward to achieve. In this work we defined a high-quality, high throughput, sputtering process, directly on an industrial machine suitable for large silicon substrates. We show how the film orientation can be tuned between highly-(100) textured and (111), simply by playing with the thickness of a sputtered seed layer. The flexibility offered by magnetron sputtering in terms of microstructural tuning and its impact on the piezoelectric properties is discussed as well. With an optimized process we measured a transverse effective piezoelectric coefficient e31,f = -23 C/m2 on samples showing very low dielectric losses and leakage currents. Energy harvesting (EH) from ambient vibrations can represent a relevant technological breakthrough as it allows self-powering of portable electronic devices for which wiring or battery replacement is either too costly or unpractical. Examples are wireless sensor nodes for structural health monitoring, drug delivery devices, and many others. The most promising route to achieve adequate power levels and acceptable unit costs is to implement piezoelectric energy conversion at the MEMS scale. Whereas devices excited through a frequency coupling with the resonance of the harvester have made significant progress, only few studies have been performed for the exploitation of motion sources characterized by low frequencies and high amplitudes, such as human motion. In this work we report about design, modeling, microfabrication and characterization of an energy harvester based on PZT thin films equipped with interdigitated electrodes (IDE). The advantages of this configuration with respect to the standard parallel-plate (PPE) capacitor one have been studied in detail, and experimentally compared with the PPE configuration realized with AlN-ScN alloys. The PZT-IDE version realizes a similar high output voltage range, however, with a much larger electromechanical coupling coefficient. This means that our new version can be used in combination with lower quality factor resonant structures. As a consequence, one can realize efficient harvesting also in presence of air damping and thus avoid vacuum packaging. The remarkable resulting energy conversion efficiency makes this geometry particularly suitable for vibration energy conversion from human motion.
000202048 6531_ $$aPZT thin films
000202048 6531_ $$aMEMS
000202048 6531_ $$aRF sputtering
000202048 6531_ $$apiezoelectric coefficient
000202048 6531_ $$ainterdigitated electrodes
000202048 6531_ $$aenergy harvesting
000202048 700__ $$0242095$$aMazzalai, Andrea$$g197189
000202048 720_2 $$0240369$$aMuralt, Paul$$edir.$$g105945
000202048 8564_ $$s16332887$$uhttps://infoscience.epfl.ch/record/202048/files/EPFL_TH6375.pdf$$yn/a$$zn/a
000202048 909C0 $$0252012$$pLC$$xU10334
000202048 909CO $$ooai:infoscience.tind.io:202048$$pthesis-bn2018$$pDOI$$pSTI$$pthesis$$qDOI2
000202048 917Z8 $$x108898
000202048 917Z8 $$x108898
000202048 918__ $$aSTI$$cIMX$$dEDMX
000202048 919__ $$aLC
000202048 920__ $$a2014-10-10$$b2014
000202048 970__ $$a6375/THESES
000202048 973__ $$aEPFL$$sPUBLISHED
000202048 980__ $$aTHESIS