MSE Seminar Speaker: Adrian Podpirka, JHU/APL
Speaker: Adrian Podpirka, Ph.D., John Hopkins University Applied Physics Laboratory
Title: Nanopatterning in GeTe Phase Change Materials Using Heated Atomic Force Microscopy
The origin of phase-change materials dates back to 1968, when Ovshinsk observed that a class of compounds, namely the chalcogenide glasses, could be switched rapidly and reversibly between a highly resistive state and a conductive state by applying an electric field. It was in the early 1990s that commercialization occurred with the use of compact disks and thus, revolutionizing data-storage applications. The technological implementation of the electrical properties of phase-change materials has been pursued more recently, both with optical and electronic properties.
In this talk, I will discuss one such material, GeTe. In this work, we explore the crystallization of amorphous germanium telluride (GeTe) thin films, controlled with nanoscale resolution using the heat from a thermal AFM probe. The dramatic differences between the amorphous and crystalline GeTe phases yield embedded nanoscale features with strong topographic, electronic, and optical contrast. The flexibility of scanning probe lithography enables the width and depth of the features, as well as the extent of their crystallization, to be controlled by varying probe temperature and write speed. Together, these technologies suggest a new approach to nanoelectronic and opto-electronic device fabrication and a novel route to the patterning of conductive channels for such applications as lab-on-chips and conductive pathways.
I will conclude the talk by introducing some of the new capabilities we have at JHU/APL with chalcogenide material growth, our growth interests and possibilities for collaborative efforts.
Dr. Podpirka received his B.S. in Material Science and Engineering in 2006 from Columbia University and his M.S and Ph.D. from Harvard University in 2007 and 2012, respectively during which time, he worked with Professor Shriram Ramanathan on Complex Oxide Thin Films. His dissertation dealt with the effects of oxygen vacancies in complex oxide electronic systems; namely (BaSr)TiO3 and doped La2NiO4. systems After completing his graduate studies, Dr. Podpirka became a National Research Council Postdoctoral Fellow at the Naval Research Lab in Washington, D.C working on III-V MBE growth with Dr. Brian Bennett and phase change material. Upon conclusion of the post-doc, he won the prestigious Department of Energy Sunshot Fellowship and worked with Prof. Jonathan Spanier at Drexel University in complex oxide solar cells. He joined the Johns Hopkins University Applied Physics Laboratory in 2017 where he is working on MBE growth of chalcogenide systems.