Prof. Yonatan Calahorra
Magneto-Electro-Mechanical Smart Materials lab, Department of Materials Science and Engineering, Technion – IIT, Haifa, Israel
Multifunctional materials play a major role in transducing and sensing applications, for example piezoelectric materials allowing electromechanical energy and information conversion, leading to applications such as ultrasound and sonar imaging. Our lab deals with such materials with a goal of bringing new multifunctionality through composites or utilizing of overlooked properties. For example, GaN as a semiconducting material received its fame due to excellent electronic and optoelectronic properties. However, it also possesses piezoelectric properties – thus opening up a path for electromechanical semiconductor applications (sometimes called piezotronic).
In this seminar I will share some of our recent work in this field. In the first part, focusing on the ability to enhance/control the piezoelectricity of GaN through nanostructuring – achieved by electrochemical as well as dry etching. AFM based electromechanical measurements were used to quantify the conductivity and piezoelectricity as a function of etching and doping degree. The role of crystalline defects will be discussed in particular. Next, I will introduce the concept of magnetoelectric composite coupling – a combination of piezoelectric and magnetostrictive materials. In particular, our work on magnetic layer nanostructure engineering, achieved by sputtering on initially porous substrates, and also new concepts in the design of the composite interface.