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Sylvia Matzen: Integration of piezoelectric thin films in electronic devices

Wanneer:do 15-09-2016 11:00 - 12:00

The coupled degrees of freedom in complex oxides can be manipulated by electric field, magnetic field or light, providing new avenues for understanding and engineering functionality in nanoelectronic devices as well as enhancing material properties. Among complex oxides, ferroelectric materials possess a thermodynamically stable and switchable polarization that persists even in the absence of an applied electric field. These materials exhibit interesting properties, especially piezoelectricity which is the ability to generate mechanical deformation under electric field. Lead zirconium titanate PbZr(1-x)Ti(x)O3 (PZT) is the most widely used ferro-piezoelectric, showing very high electro-mechanical and dielectric responses at a particular composition (x=0.48) called the morphotropic phase boundary. Intensive research is now focused on its integration in micro- and nanoelectronic devices (such as microelectromechanical systems MEMS or sensors) in thin film form between two electrodes. This capacitor geometry allows manipulating PZT properties by applying low voltages as well as tuning devices functionalities through interface control.

Over the past few years, we have worked on the integration of PZT thin films in devices, by controlling interfacial effects and combining piezoelectric response of PZT with other functionalities. This talk will mainly summarize our current investigation on two research topics: magnetoelectric devices combining piezoelectricity and ferromagnetism in hybrid PZT/ spin valves heterostructures, and photostrictive devices combining piezoelectricity and photovoltaic properties.

In the first type of device, we have shown that the strain induced in PZT by an electric field can be transferred in a ferromagnetic layer at the interface with PZT, allowing manipulating electrically magnetic domain wall propagation.

In the second type of device, we investigate the potential of the coupling between piezoelectricity and photovoltaic properties. Ferroelectric materials can respond to optical excitations through the interaction of photoinduced charge carriers with the polarization. However, little is known about the coupling of these photogenerated currents with the structural response of ferroelectrics. We will present our recent results on photoinduced currents and photoinduced strain in PZT capacitors, showing strong electrical contributions from interfaces.