Spectroscopic investigation on phase transitions for Ge2Sb2Te5 in a wide photon energy and high temperature region

Title
Spectroscopic investigation on phase transitions for Ge2Sb2Te5 in a wide photon energy and high temperature region
Authors
Y. K. SeoJ. -S. ChungY. S. LeeE. J. Choi정병기
Keywords
Ge2Sb2Te5(GST); optical constants; ellipsometry; amorphous phase; crystalline phase
Issue Date
2012-02
Publisher
Thin solid films
Citation
VOL 520, NO 9, 3458-3463
Abstract
We investigated the electronic properties of phase-change material Ge2Sb2Te5 (GST) films using spectroscopic ellipsometry in a wide photon energy and high temperature region. Apart from the charge carrier response, the totality of optical conductivity spectra for three phases of GST films, i.e., amorphous (AM), face-centeredcubic (FCC), and hexagonal (HEX), is quite similar, composed of two interband transitions in visible and UV regions. From optical analysis in a wide photon energy region up to 8.7 eV, we found that the intensity as well as the position of the interband transition in the visible region changes significantly as the phase of GST films turns from the amorphous to the crystalline phase, which is consistent with previous theoretical studies. In high temperature measurements above room temperature for the three phases of GST films, we found that the change of optical response for the AM phase of GST film occurs abruptly through two successive phase transitions near 150 °C and 270 °C, while the optical spectra of the FCC phase shows a change only near 270 °C. In contrast to the two above-mentioned cases, a slight change in optical spectra is observed for the HEX phase with the increasing temperature. From the measured optical spectra, we derived the temperature dependence of optical bandgap for the three phases, which are closely correlated to the change of the transport property for the GST films.
URI
http://pubs.kist.re.kr/handle/201004/42865
ISSN
00406090
Appears in Collections:
KIST Publication > Article
Files in This Item:
There are no files associated with this item.
Export
RIS (EndNote)
XLS (Excel)
XML


qrcode

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

BROWSE