Prof. Ganpati Ramanath
Rensselaer Polytechnic Institute

Out-of-the-box design of molecularly-tailored nanomaterials and interfaces

Location: EB1 Room 1011

Friday, August 25th 2017 - 11:00 am

Realizing novel nanomaterials and heterointerfaces with control over electrical, thermal and mechanical properties is crucial for diverse applications in electronics and energy harvesting. The first part of my talk will discuss the synthesis of a new class of bulk semiconductor and oxide thermoelectric materials obtained by surfactant-directed sculpting and doping for solid-state cooling and waste-heat harvesting. The second part of my talk will describe the use of single nanolayers of organic coupling agents to tailor multiple properties of soft-hard or organic-inorganic heterointerfaces germane to emergent nanodevices. I will demonstrate a scalable microwave-solvothermal approach to sculpt nanocrystals with controllable shape, size, trace doping and surface chemistry. Bulk pellets made from these nanocrystals exhibit multifold superior figures of merit than their non-nanostructured and non-alloyed counterparts. While nanostructuring leads to ultralow thermal conductivities, doping-induced alterations in defect chemistry and electronic structure lead to high electrical conductivities and high Seebeck coefficients. Electron spectroscopy and density functional theory calculations show that key mechanisms include doping-induced carrier concentration control, suppression of antisite defects, and multifold increases in the charge carrier effective mass due to profound changes in the electronic structure. I will then demonstrate the use of molecular nanolayers to tailor chemical, mechanical, thermal and electronic properties of metal-ceramic and metal-thermoelectric interfaces. Introducing molecular nanolayers (e.g., organosilanes, thiols, organophosphonates) at inorganic metal-oxide and metal-thermoelectric interfaces can produce multifold enhancement in interfacial mechanical strength, and thermal and electronic transport. Electron spectroscopy, and X-ray diffraction show that the property enhancements are due to nanolayer-induced changes in the interface chemistry and structure. Key mechanisms include strong bonding, oxide scavenging, diffusion curtailment, and altered phase formation, all of which can be controlled by appropriate choice of molecular termini, length and backbone chemistry, and annealing. I will conclude by discussing the property interrelationships, and the utility of using nanomolecular layers to access atomistic details of nanoscopic interfacial phenomena via macro-experiments.

Professor Ramanath received his PhD from the University of Illinois, Urbana, in 1997. His PhD thesis work won him a Graduate Student Gold Award from the Materials Research Society. He joined Rensselaer in 1998 as an assistant professor and has been a full professor since 2006, and was named John Tod Horton Chaired Professor in 2013. His research focuses on developing a fundamental understanding of structure-processing-property relationships in molecularly-tailored inorganic nanomaterials and heterointerfaces for applications in energy and electronics. He has co-authored 170 journal articles (Google Scholar h-index 48, ~8000 citations), one book chapter, and holds 9 US patents. He has delivered more than 200 invited/plenary/keynote talks worldwide, and has organized several international symposia and workshops for the MRS, AVS and TMS. Ramanath is a co-founder and director of ThermoAura Inc., which is commercializing a nanomaterials manufacturing technology developed in his laboratory. He was the Director of the NY State Center for Future Energy Systems (2008-10). He served as an Editor of IEEE Transactions on Nanotechnology (2003-15) and is an Editorial Advisory Board member for Journal of Experimental Nanoscience. Ramanath is a Fellow of the American Physical Society and the American Vacuum Society. His awards include Friedrich Wilhem Bessel Award (2013), Brahm Prakash Chaired Professorship at IISc, Bangalore, India, NSF CAREER Award, Bergman Young Scientist Award from the US-Israel Binational Science Foundation, an IBM University Research Partnership Award and Alexander von Humboldt Fellowship. Visiting appointments include RWTH, Aachen University, Germany; Max-Planck-Institute for Solid State Research, Stuttgart, Germany; National Institute of Materials Science, Tsukuba, Japan; IISc, Bangalore, India; University of Wollongong, Australia; PSG Institute of Advanced Studies, Coimbatore, India. Ramanath’s hobbies include performing and teaching Indian classical music (live and TV performances in the US, Australia, Germany, and India), various aspects of Indic culture, philosophy, chants and devotional hymns, Sanskrit, Indian history, cricket, multilingual puns, and poetry in 5 different languages.

North Carolina State University