Valence band structures of the phase change material Ge2 Sb2 Te5

Dohyun Lee, Sang Sun Lee, Wondong Kim, Chanyong Hwang, M. B. Hossain, Ngyuen Le Hung, Hyojin Kim, C. G. Kim, Hangil Lee, Han Na Hwang, Chan Cuk Hwang, Tae Yon Lee, Younseon Kang, Cheolkyu Kim, Dong Seok Suh, Kijoon H.P. Kim, Yoonho Khang

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We report the experimental evidence of significant change of the valence band structure during crystallization of Ge2 Sb2 Te5 (GST). Amorphous GST, prepared by sputter deposition at room temperature (RT), transforms successively into face-centered-cubic (fcc) and a hexagonal-close-packed (hcp) structures at around 150 and 300 °C, respectively, during a stepwise temperature increase from RT to 350 °C. During temperature increase, ultraviolet photoemission spectra were in vacuo obtained using synchrotron radiation. The measurement of the amorphous and fcc GST shows that the difference between the maximum valence band edge and the Fermi level reduces by 0.35 eV during crystallization. For the fcc to hcp phase transformation, no band gap reduction was observed.

Original languageEnglish
Article number251901
JournalApplied Physics Letters
Issue number25
StatePublished - 2007

Bibliographical note

Funding Information:
Part of this work is supported by KORP through the “Development of Advanced Materials Metrology” project through Korea Research Institute of Standards and Science. Pohang Accelerator Laboratory is supported by Ministry of Science and Technology.


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