Domain control in strained lead-free alkaline niobate thin films to tune piezoelectric coefficients

• Applicant: Dr. Jutta Schwarzkopf, since 9/2015
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2015 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 276754399

Ferroelectric materials are omnipresent in our everyday life, e.g. as sensors and actuators in cars, ultrasound devices in medicine or memory devices. In spite of an existing EU-Directive for the restriction of hazardous substances a huge volume of lead-based ferroelectric materials is still used yet due to a substantial lack of alternative materials. In the quest for lead-free ferroelectrics, niobates have been identified to exhibit strong piezoelectric properties similar to lead-based materials. In order to reveal the correlation of microstructure and ferroelectric domain formation with piezoelectric properties, the proposal aims to develop the fabrication of lead-free ferroelectric potassium sodium niobate thin films (KNN) by the industrially compatible metal-organic chemical vapor deposition (MOCVD) with the perspective to optimize piezoelectric properties. A targeted introduction of epitaxial lattice strain will be realized by the use of different oxide substrates to tune piezoelectric properties of the films. An understanding and controlling of the domain and defect formation is indispensable for enhancing the piezoelectric properties. MOCVD as deposition method is potentially more eligible for industrial processes than pulsed laser deposition (PLD) typically applied in fundamental research. The thin film growth of niobates by MOCVD was developed in the host group at IKZ only very recently. Excellent results were achieved for pure NaNbO3 thin films, thus now this method will be applied to the more complex KNN. PLD will be used in parallel as comparative method to study the influence of deposition conditions on piezoelectric properties. The aim is to provide KNN films with large piezoelectric coefficients by MOCVD in order to tentatively exploit these films in electronic devices. The applicant brings comprehensive expertise in thin film growth, characterization and particularly control of ferroelectric domain structure which are complimentary to the host organization's competences.

• DFG Programme: Research Grants
• International Connection: Netherlands
• Cooperation Partner: Professorin Dr. Beatriz Noheda
• Ehemaliger Antragsteller: Dr. Ludwig Feigl, until 9/2015