Dresden 2006 – scientific programme

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DS: Dünne Schichten

DS 2: Optical properties of thin films II

DS 2.1: Invited Talk

Monday, March 27, 2006, 11:15–12:00, GER 37

Phase Change Materials for Optical and Electronic Storage — •Christoph Steimer, Ralf Detemple, Henning Dieker, Johannes Kalb, Daniel Wamwangi, Wojciech Welnic, and Matthias Wuttig — I. Physikalisches Institut 1A RWTH-Aachen, 52056 Aachen, Germany

Phase change materials are commercially used in rewritable optical storage and currently investigated as non-volatile electronic storage to replace conventional FLASH-memory. A short laser or current pulse of high intensity melts a sub-micron spot of crystalline material before quenching to the amorphous state. A second pulse of lower intensity but longer duration leads to a weaker spatial temperature profile and activates recrystallisation. Since reflectivity and conductivity of the amorphous state are lower, a third even weaker laser - or current pulse can be used to read out the state of the bit without changing it. As recrystallisation is the slowest process involved, materials with a small structural difference between the crystalline and amorphous phase promise higher data transfer rates. Such structural similarity however limits the optical and electronic contrast between the phases, i.e. readability, and the stability against spontaneous recrystallisation, i.e. data retention. Despite of their commercial application material development of PC-media still heavily relies on empirical approaches. This contribution summarizes recent progress in understanding how stoichiometry determines the structure of the crystalline and the amorphous phase and the resulting electronic differences.