Seminars

Aeromaterials: Structuring Thin Films into 3D — from capacitors to cell templates

by Dr. Rainer Adelung, Professor of Materials Science and Engineering at Christian-Albrechts-University Kiel July 30, 2020

Abstract: Thin film technology has pushed fascinating break through applications like microchip fabrication, medical technology or anti-reflection coatings. The presentation seeks to introduce the idea to bring the 2D thin film technology into 3D: Rolling up a thin film of nanoscopic thickness into a tube with a few micrometers in diameter, that is in space interconnected after a few tens of micrometers with other tubes pointing in different directions, will give you a relatively robust 3D tube network but with a weight in the scale of the ambient air and unusual physical properties. The talk will show that a simple sacrificial template approach can be used to realize these “aero structures”. Properties of this class of materials will be illustrated but not limited to aero carbon structures from graphene or carbon nanotubes [1], for applications like conductive silicone, energy materials  and cell templates as well as the fabrication of aero hexagonal boron nitride [2] that can be employed in optics as “artificial solid fog”.

[1] Nature Communications 8, 1215 (2017)

[2] Nature Communications 11, 1437 (2020)

Computation-Guided Discovery of Transparent Crystals with Ultrahigh Piezoelectricity

by Dr. Long-Qing Chen, Professor of Materials Science and Engineering and Professor of Engineering Science and Mechanics, Penn State. Piezoelectric crystals can generate electrical charge under an applied mechanical force and change shape under an applied electrical field. They have many applications in electromechanical devices such as ultrasonic transducers for medical imaging, actuators, etc. The piezoelectricity of a crystal is measured by the amount of strain that a crystal exhibits under an applied electric field or the amount of charge that a crystal generates under a stress. It has been a long-standing challenge to simultaneously achieve high piezoelectricity and light transparency in a crystal since the highest performance piezoelectric crystals are ferroelectrics containing high-density light-scattering domain walls within their domain structures. This presentation will discuss our recent computation-guided, rather surprising, discovery of simultaneous near-perfect light transparency and ultrahigh piezoelectricity in Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) crystals by understanding the ferroelectric domain evolution mechanisms under alternative current (AC) electric field poling using phase-field simulations. The newly discovered transparent ferroelectric crystals are expected to open up a range of electro-optical-mechanically coupled devices from high-throughput photoacoustic imaging to transparent actuators for haptic applications.

Thin Films for Piezoelectric Microelectromechanical Systems

by Dr. Susan Trolier-McKinstry, Professor of Materials Science and Engineering and Electrical Engineering, Penn State February 17, 2020 Piezoelectric materials couple electrical and mechanical energies, and as such, offer an interesting platform to study numerous functional properties. Piezoelectric thin films are ubiquitous in filters and duplexers for cell phones and are of increasing interest in low voltage microelectromechanical systems (MEMS) for sensing, actuation, and energy harvesting. This talk will discuss how materials are optimized for these applications, as well as examples of the use of piezoelectric films over a wide range of length scales. The key figures of merit for resonators, actuators, and energy harvesting will be discussed, with emphasis on how to achieve these on practical substrates. Recent work on doped AlN for cell phone resonators will be reviewed. In addition, the roles of crystallographic orientation and domain state will be described for low voltage actuators and mechanical harvesters in thin films with the perovskite structure. Examples of integration into MEMS structures will also be discussed, including adaptive optics for X-ray telescopes, low frequency and non-resonant piezoelectric energy harvesting devices, inkjet printers, and ultrasound transducers for miniaturized medical diagnostics.

Thin Film Synthesis Activities in the Maria Group at Penn State

 by Dr. Jon-Paul Maria, Penn State, 1/27/2020. This presentation summarizes the research activities in the Maria group that involve thin film synthesis. The major categories include high mobility conducting oxides for IR plasmonic applications, reactive nanoaminates for chemical energy storage and propulsion, entropy stabilized oxides, high entropy transition metal carbines, and thin film explorations to find new functional materials. In all cases, research in the group endeavors to advance the science and understanding of synthesis in parallel to property engineering.