TY - JOUR
T1 - Photo-oxidation and the absence of photodarkening in Ge2Sb 2Te5 phase change material
AU - Lee, Bong Sub
AU - Xiao, Ying
AU - Bishop, Stephen G.
AU - Abelson, John R.
AU - Raoux, Simone
AU - Deline, Vaughn R.
AU - Kwon, Min Ho
AU - Kim, Ki Bum
AU - Cheong, Byung Ki
AU - Li, Heng
AU - Craig Taylor, P.
PY - 2006
Y1 - 2006
N2 - Ge2Sb2Te5 is under intense investigation for phase-change memory devices, including rewriteable DVDs where optical illumination is used to switch between the glassy and crystalline states. We investigate the influence of optical irradiation on the amorphous phase. Many chalcogenide glasses display photo-oxidation, photodarkening or photo-bleaching, but little has been reported on the Ge-Sb-Te system. Using spectroscopic ellipsometry (SE) and secondary ion mass spectrometry, we determine that the samples have a strong tendency to photo-oxidize; if this is not accounted for, then the analysis of SE data appears to show photodarkening. Other authors recently reported photodarkening in nonstoichiometric GexSb 20-xTe80 [Pamukchieva et al., Proc. SPIE 5581, 608 (2004); Pamukchieva et al., J. Optoelectron. Adv. Mater 7, 1277 (2005)], but our analysis suggests that the changes were actually the result of photo-oxidation. The oxide has lower values of (n, k) than Ge2Sb2Te 5, and can be etched by hydrofluoric acid or water. Our observation of negligible photodarkening is consistent with previous work that found less photodarkening in tellurides compared with selenides or sulfides, and that an increase in the mean coordination number, here by Ge addition, further reduces the photodarkening effect.
AB - Ge2Sb2Te5 is under intense investigation for phase-change memory devices, including rewriteable DVDs where optical illumination is used to switch between the glassy and crystalline states. We investigate the influence of optical irradiation on the amorphous phase. Many chalcogenide glasses display photo-oxidation, photodarkening or photo-bleaching, but little has been reported on the Ge-Sb-Te system. Using spectroscopic ellipsometry (SE) and secondary ion mass spectrometry, we determine that the samples have a strong tendency to photo-oxidize; if this is not accounted for, then the analysis of SE data appears to show photodarkening. Other authors recently reported photodarkening in nonstoichiometric GexSb 20-xTe80 [Pamukchieva et al., Proc. SPIE 5581, 608 (2004); Pamukchieva et al., J. Optoelectron. Adv. Mater 7, 1277 (2005)], but our analysis suggests that the changes were actually the result of photo-oxidation. The oxide has lower values of (n, k) than Ge2Sb2Te 5, and can be etched by hydrofluoric acid or water. Our observation of negligible photodarkening is consistent with previous work that found less photodarkening in tellurides compared with selenides or sulfides, and that an increase in the mean coordination number, here by Ge addition, further reduces the photodarkening effect.
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U2 - 10.1557/proc-0918-h02-04
DO - 10.1557/proc-0918-h02-04
M3 - Conference article
AN - SCOPUS:33751023107
SN - 0272-9172
VL - 918
SP - 113
EP - 118
JO - Materials Research Society Symposium Proceedings
JF - Materials Research Society Symposium Proceedings
T2 - 2006 MRS Spring Meeting
Y2 - 17 April 2006 through 21 April 2006
ER -