School Seminar Program
Physics under Pressure: New Phases of Silicon and Germanium
Dr Bianca Haberl
Electronic Materials Engineering, RSPE, ANU
Pressure is the only thermodynamic variable that allows modification of materials on an atomic level through direct changes of the atomic bond-length. This provides not only wide scope for cleanly identifying structure/property relationships, but can also be exploited to synthesize entirely new materials through pressure-induced solid-solid phase transitions. Experimentally, such high pressure is usually realized through static compression, either using diamond-anvil cells, where the material is confined and compressed between two diamonds, or through point loading (nanoindentation), where a sharp diamond tip is pressed into the material.
In this talk, I will present such pressure-induced phase transitions on the examples of the elemental semiconductors silicon and germanium. Both these materials are of particular interest since pressure-induced transitions in both elements are irreversible. That is, after full pressure release new crystalline structures with unique electronic and/or mechanical properties are formed from the parent structure. Understanding these transitions is important from a fundamental point of view, but may also be utilized for localized band-gap engineering for novel devices.
Dr Bianca Haberl received a master in physics from the University of Augsburg (Germany) in 2006. She completed her Ph.D. in 2011 on the characterization of different forms of amorphous silicon and, in particular, on the correlation of their structural properties and high-pressure behaviour. She is now working as a postdoctoral research fellow and has been extending her research to include the high-pressure behaviour of further crystalline and amorphous Group IV elements, such as carbon and germanium.
Refreshments will be held in the tearoom after the seminar