Open AccessPenn gap rule in phase-change memory materials: No clear evidence for resonance bonds
Author(s) -
K. Shimakawa,
Lukáš Střižík,
T. Wágner,
M. Frumar
Publication year - 2015
Publication title -
apl materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.571
H-Index - 60
ISSN - 2166-532X
DOI - 10.1063/1.4907251
Subject(s) - materials science , band gap , resonance (particle physics) , dielectric , phase change , amorphous solid , phase (matter) , condensed matter physics , optoelectronics , engineering physics , crystallography , atomic physics , chemistry , physics , organic chemistry
Although a proposal of resonance bonds in crystalline phase-change materials based on the GeSbTe system has been provided, we do not find any clear evidence in favor of the proposal. The ellipsometric study demonstrates that a change in the high frequency dielectric constant ε∞ between the amorphous and crystalline phases is only scaled by the average bandgap (the Penn gap rule). Even for a pure antimony film, regarded as a prototype resonance bonding material, ε∞ was found to follow the Penn gap rule. Experimentally, we did not find any evidence of a significant change in the optical transition matrix element during the phase change, which is necessary to support the idea of resonance bonds