In condensed matter systems, topological structures are inherent to ferroic materials, i.e. materials with a spontaneous reversible ordering, such as magnetic materials, ferroelectrics and ferroelastic materials. Due to degeneracy in possible orientations of the order parameter upon cooling below the ferroic phase transition temperature, ferroic phases tend towards the formation of discrete domain structures. Adjacent domains are separated by naturally occurring planar topological defects called domain walls.
The first part of the talk will focus on “ferroelectric domain wall memory device”. The discovery of electrical conductivity in specific types of ferroelectric domain walls gave rise to “domain wall nanoelectronics”, a technology in which the wall (rather than the domain) stores information. Here, we have recently demonstrated a prototype non-volatile ferroelectric domain wall memory, scalable to below 100 nm, whose binary state is defined by the existence or absence of conductive walls. The device can be read-out nondestructively at moderate voltages (< 3 V), exhibits relatively high OFF-ON ratios (~103) with excellent endurance and retention characteristics, and possesses multilevel data storage capacity. Our work1 thus constitutes an important step toward integrated nanoscale ferroelectric domain wall memory devices.
In the second half of the talk, nanoscale bubble domains in ultrathin ferroelectric films will be introduced. This new type of nanoscale ferroelectric domains, has been observed in ultrathin epitaxial PbZr0.2Ti0.8O3/SrTiO3/PbZr0.2Ti0.8O3 sandwich structures.2 Using piezoresponse force microscopy and aberration-corrected atomic-resolution scanning transmission electron microscopy mapping techniques, it is confirmed that the bubble domain are laterally confined spheroids of sub-10 nm size with local dipoles opposite to the macroscopic polarization of their surrounding ferroelectric matrix. An incommensurate phase and symmetry breaking is found within these domains, which result in local polarization rotation and hence a mixed Néel-Bloch-like character to the bubble domain walls. These findings highlight the richness of polar topologies that may develop in ultrathin ferroelectric structures and bring forward the prospect of emergent electronic functionalities due to topological transitions.
The Odyssey of the Mind team met to brainstorm new ideas and discuss current technical challenges.
STAMI held its inaugural Industrial Partners Day and Exposition on October 19th-20th at Geogria Tech's Historic Academy of Medicine in Midtown Atlanta. The event was attended by over 20 different companies interested in advanced materials and interfaces and by over 150 Georgia Tech faculty, students, and researchers from a variety of schools within the College of Engineering and the College of Science. Professor George M. Whitesides from Harvard University delivered the Keynote Address while both Georgia Tech faculty and Industrial speakers participated in presentations and networking opportunties.
STAMI has awarded 2017 Seed Grants to Georgia Tech researchers that are members of the Community for Research on Active Surfaces and Interfaces (CRĀSI) and the Soft Matter Incubator (SMI). Proposals were selected on a competitive basis. The 2017 CRĀSI seed grant program sought innovative proposals addressing fundamental scientific questions pertaining to surfaces and interfaces, and two collaborative proposals were selected. The 2017 SMI seed grant program sought proposals addressing questions pertaining to fundamental soft matter, and three collaborative proposals were selected. Learn more.
Professor Seth Marder, from the Georgia Tech Schools of Chemistry and Biochemistry and Materials Science and Engineering, has been elected as a Fellow of the National Academy of Inventors (NAI). According to the NAI, "Election to NAI Fellow status is the highest professional distinction accorded solely to academic inventors who have demonstrated a prolific spirit of innovation in creating or facilitating outstanding inventions that have made a tangible impact on quality of life, economic development, and welfare of society." Professor Marder is the first NAI fellow from the Georgia Tech College of Sciences. Read more here.
Modification of the TCO surface with a redox-active surface modifier is a possible approach toward enhancing OPV efficiency by providing an efficient charge-transfer pathway between either hole- or electron-harvesting contacts and the organic active layer. Two different deposition techniques were used with perylene diimide (PDI) surface modifiers in the study: adsorption from solution (SA) and spin coating (SC), to create three types of monolayer films on ITO: SA PDI–phenyl–PA, SA PDI–diphenyl–PA, and SC PDI–phenyl–PA. These thin films, designed to act as “charge-transfer mediators”, were used to study relationships between molecular structure, electron-transfer (ET) kinetics, and electronic structure.