TY - JOUR
T1 - Why phase-change media are fast and stable
T2 - A new approach to an old problem
AU - Kolobov, Alexander V.
AU - Fons, Paul
AU - Tominaga, Junji
AU - Frenkel, Anatoly I.
AU - Ankuoinov, Alexei L.
AU - Yannopoulos, Spyros N.
AU - Andrikopoulos, Konstantinos S.
AU - Uruga, Tomoya
PY - 2005/5
Y1 - 2005/5
N2 - Present-day multimedia strongly relies on re-writable phase-change optical memories. We find that, different from current consensus Ge2Sb 2Te5 (GST), the material of choice in digital versatile discs-random access memory (DVD-RAM), possesses a structure similar to ferroelectric GeTe, namely that Ge and Sb atoms are located off-center giving rise to a net dipole moment. Amorphisation of both GeTe and GST results in a significant shortening of covalent bonds and a decrease in the mean-square relative displacement concomitant with a drastic change in the short-range order. We demonstrate that the order-disorder transition in GeTe and GST is primarily due to a flip of Ge atoms from an octahedral position into a tetrahedral position without rupture of strong covalent bonds. It is this nature of the transformation that ensures large changes in reflectivity, fast disk performance and repeatable switching over millions cycles.
AB - Present-day multimedia strongly relies on re-writable phase-change optical memories. We find that, different from current consensus Ge2Sb 2Te5 (GST), the material of choice in digital versatile discs-random access memory (DVD-RAM), possesses a structure similar to ferroelectric GeTe, namely that Ge and Sb atoms are located off-center giving rise to a net dipole moment. Amorphisation of both GeTe and GST results in a significant shortening of covalent bonds and a decrease in the mean-square relative displacement concomitant with a drastic change in the short-range order. We demonstrate that the order-disorder transition in GeTe and GST is primarily due to a flip of Ge atoms from an octahedral position into a tetrahedral position without rupture of strong covalent bonds. It is this nature of the transformation that ensures large changes in reflectivity, fast disk performance and repeatable switching over millions cycles.
KW - Armorphous-to-crystalline transition
KW - Local structure
KW - X-ray absorptionlihe structure (XAFS)
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U2 - 10.1143/JJAP.44.3345
DO - 10.1143/JJAP.44.3345
M3 - Article
AN - SCOPUS:23144454441
SN - 0021-4922
VL - 44
SP - 3345
EP - 3349
JO - Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
JF - Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
IS - 5 B
ER -