Origin of the optical contrast in phase-change materials
|Title||Origin of the optical contrast in phase-change materials|
|Publication Type||Palaiseau Article|
To be filled in
|Author Address|| |
Welnic, W (Reprint Author), Rhein Westfal TH Aachen, Inst Phys 1 1A, D-52056 Aachen, Germany. Rhein Westfal TH Aachen, Inst Phys 1 1A, D-52056 Aachen, Germany. Ecole Polytech, CNRS CEA, Solides Irradies Lab, Palaiseau, France. ETSF, San Sebastian, Spain.
|Welnic, W, Botti, S, Reining, L, Wuttig, M|
|Publisher||AMERICAN PHYSICAL SOC|
|Year of Publication||2007|
|Journal||Phys. Rev. Lett.|
Several chalcogenide alloys exhibit a pronounced contrast between the optical absorption in the metastable rocksalt and in the amorphous phase. This phenomenon is the basis for their application in optical data storage. Here we present ab initio calculations of the optical properties of GeTe and Ge1Sb2Te4 in the two phases. The analysis of our computations and experimental data reveal the correlation between local structural changes and optical properties as well as the origin of the optical contrast in these materials. We find that the change in optical properties cannot be attributed to a smearing of transition energies as commonly assumed for amorphous semiconductors: the optical contrast between the two phases can only be explained by significant changes in the transition matrix elements.