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Functional oxides

Oxide ferroelectrics show profound features, e.g., giant permittivity, large piezoelectricity, or tenability, for use in sensors, data storage and radio-frequency devices. We work on the systematic study of the impact of strain and stoichiometry on the properties and applications of oxide thin films. Strain in the film could be introduced by the mismatch between substrate and film. The lattice parameters of oxide film could be further modified via doping and cation non-stoichiometry. We demonstrate that the temperature of phase transition could be shift by either compressive or tensile strain. Our experimental and theoretical results lead to a strain-temperature phase diagram for Sr1-xBaxTiO3 films and K1-xNaxNbO3 films. Based on our strain-temperature phase diagram, we have obtained desirable operating temperatures for our oxides films with giant permittivity and/or large piezoelectricity for further applications, e.g. surface acoustic wave (SAW) devices and artificial synaptic device.

Applications are for instance:

Functional Oxides SAWApplication of strained ferroelectric films, example SAW.

(i). Surface acoustic wave mediated transductions could be used in biosensors or cellular-scale manipulation. The SAW is generated by interdigital transducers deposited on the top of the film. Our highly oriented and dense strained oxide films provide high piezoelectricity effect at desirable temperature. We have proved that strained thin K1-xNaxNbO3 films could generate SAW up to gigahertz-frequency. The high excitation frequencies results in finer resolution in terms of detect and manipulate cells or microparticles. It opens new opportunities to use function oxide layers as a sensor in our molecular layers deposition system, or to fabricate acoustic-based tweezers to precisely move cells/microparticles along the arbitrary path on the surface.

Functional Oxides in Neuromorphic ComputingNeuromorphic computing using strained ferroelectric films.

(ii). Artificial synaptic devices show pronounced advantages in performing energy-efficient computation than the conventional computational systems based on the von Neumann architecture. It emulates the computation performed by biological synapse. Our strained films, SrTiO3, perform resistive change behavior in the in-plane direction at room temperature.  This inspires us to perform the biological forgetting process, e.g. the short-term and long-term memory, with nano-scale electrodes 2D array on the top of the films.

Additional Information

Contact:

Prof. Dr. Roger Wördenweber

Tel.:  +49-2461-61-2365
e-mail: r.woerdenweber@fz-juelich.de

More Information

Projects:

  • - Engineering of Oxide Films via Strain
  • - Thin Film SAW
  • - Neuromorph Oxide Devices

Publications:

Electronic characterization of polar nanoregions in relaxor-type ferroelectric NaNbO3 films, Biya Cai et al, Phys. Rev. B 2016, 93, 224107

 

Electric field induced relaxor behavior in anisotropically strained SrTiO3 films, Yang Dai et al, Physica B Cond. Mat. 2016, 485, 78

 

Engineering of the frequency dependence of the ferroelectric properties of thin film Pt/Ba0.5Sr0.5TiO3/Pt structures, A. Markov at al, Physica B Cond. Mat. 2015, 475, 10

 

Anisotropic ferroelectric properties of anisotropically strained epitaxial NaNbO3 films , Biya Cai et al, J. Appl. Phys. 2014, 115, 224103

 

Ferroelectric domain structure of anisotropically strained NaNbO3 epitaxial thin films, J. Schwarzkopf et al, J. Appl. Phys. 2014, 115, 204105

 

Impact of compressive in-plane strain on the ferroelectric properties of epitaxial NaNbO3 films on (110) NdGaO3 , R. Woerdenweber et al, Appl. Phys. Lett. 2013, 103, 13

 

Relaxor ferro- and paraelectricity in anisotropically strained SrTiO3 films, R. Woerdenweber et al, J. Appl. Phys. 2013, 113, 164103


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