Dresden 2009 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

HL: Fachverband Halbleiterphysik

HL 13: Optical properties

HL 13.13: Vortrag

Dienstag, 24. März 2009, 12:45–13:00, BEY 118

Resonant bonding in crystalline phase-change materials — •Stephan Kremers¹, Kostiantyn Shportko¹, Michael Woda¹, Dominic Lencer¹, John Robertson², and Matthias Wuttig¹ — ¹I. Physikalisches Institut (IA), RWTH Aachen, Deutschland — ²Engineering Department, Cambridge University, UK

Phase-change materials are of considerable scientific and technological interest. These materials are already employed for rewriteable optical data storage and are strong contenders to replace non-volatile flash memory. They are based on a unique class of materials, which feature a special property combination. The two phases, amorphous and crystalline, show a pronounced contrast of electrical and optical properties. They are stable on a long time scale and at the same time, they can be rapidly switched on a time scale of some ten nanoseconds when heated to appropriate elevated temperatures. To improve these materials for dedicated applications, an in-depth understanding of the relevant properties is crucial. Therefore we have employed optical spectroscopy in the energy range from 0.025 to 3 eV to probe the electronic states. The optical dielectric constant is 70-200% larger for the crystalline than the amorphous phases. This difference is attributed to a significant change in bonding between the two phases. The optical dielectric constant of the amorphous phases is that expected of a covalent semiconductor, whereas that of the crystalline phases is strongly enhanced by resonant bonding effects. This finding allows us to discuss the physical origin of the unique behavior of this class of materials.