Berlin 2005 – scientific programme

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HL: Halbleiterphysik

HL 58: Poster IIb

HL 58.7: Poster

Tuesday, March 8, 2005, 16:30–19:00, Poster TU F

Optical properties of phase change materials for optical and electronic data storage with ab initio methods — •Wojciech Wełnic^1,2, Silvana Botti², Lucia Reining², and Matthias Wuttig¹ — ¹I. Physikalisches Institut, RWTH Aachen, 52056 Aachen, Germany — ²Laboratoire des Solides Irradiés, École Polytechnique, 91128 Palaiseau cedex - France

In this work excited state calculations are presented for GeTe, the basic phase-change-material. Due to a significant change of optical reflectivity and electric conductivity upon phase transition from the amorphous to the crystalline state these materials are promising candidates for future data storage applications.

The focus of the project is on the optical and electronic properties in different phases of GeTe, ranging from the two crystalline phases, to defect structures and the amorphous phase. The origin for the difference of these properties in the different states is examined. The amorphous structure is obtained in two different ways: on one side we employ ab initio MD within a 64-atom supercell and on the other side we use a simple model structure which reproduces the local configuration reported in earlier experimental work. The electronic structure is presented in the GW-correction and the spectra are calculated within TDDFT and GW-RPA. They are compared with experimental data of thin film GeTe-samples. Differences between theory and experiment are discussed as well as the changes in the optical and electronic properties upon phase transition from the crystalline to the amorphous state.