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Tunable Bulk Acoustic Wave Resonators Based on BaxSr1-xTiO3 Thin Films

John Berge (Institutionen för mikroteknologi och nanovetenskap, Fysikalisk elektronik)
Göteborg : Chalmers University of Technology, 2009.
[Licentiatavhandling]

The main focus of this thesis is the study of a novel component based on ferroelectric BaxSr1−xTiO3 thin films – the tunable thin film bulk acoustic resonator (TFBAR). The tunable TFBAR utilizes a dc field induced piezoelectric effect in the ferroelectric film, in contrast to conventional fixed frequency TFBARs, widely used for filtering applications in wireless communication systems, which are based on ordinary piezoelectric materials. This allows dc field tuning of the resonance frequency as well as switching between resonator and capacitor response.

The first two chapters of the thesis considers general ferroelectric material and thin film properties, including film growth and characterization methods used during this work.

The third chapter is devoted to the tunable TFBAR, describing design and fabrication, as well as measurement results in wide dc bias and temperature ranges. The achieved room temperature tuning range for a Ba0.25Sr0.75TiO3 TFBAR at a center frequency of 4.2 GHz is 1.7% and the electromechanical coupling coefficient 3.7% at 15 V dc bias, with a Q-factor of 120. Modeling of the measurement results based on theory describing the field induced piezoelectric effect is presented. Finally, performance issues are discussed, concluding that improvements can be expected from further studies of the resonator design and fabrication details, including optimized Bragg reflector and electrode materials.

Nyckelord: ferroelectric films, tunable devices, field induced piezoelectric effect, bulk acoustic wave devices, piezoelectric resonators



Denna post skapades 2009-04-02. Senast ändrad 2009-04-02.
CPL Pubid: 92121

 

Institutioner (Chalmers)

Institutionen för mikroteknologi och nanovetenskap, Fysikalisk elektronik (2007-2010)

Ämnesområden

Funktionella material

Chalmers infrastruktur

Relaterade publikationer

Inkluderade delarbeten:


Tunable Solidly Mounted Thin Film Bulk Acoustic Resonators Based on BaxSr1-xTiO3 Films


Field and temperature dependent parameters of the dc field induced resonances in BaxSr1-xTiO3-based tunable thin film bulk acoustic resonators


The effect of growth temperature on the nanostructure and dielectric response of BaTiO3 ferroelectric films


Examination

Datum: 2009-05-12
Tid: 09:00
Lokal: Luftbryggan, Kemivägen 9, Chalmers University of Technology
Opponent: Prof. Thorvald Andersson