AVS 51st International Symposium
    Electronic Materials and Processing Monday Sessions
       Session EM-MoP

Paper EM-MoP9
Change of Structural and Electrical Properties due to Phase Transition of Ge@sub 2@Sb@sub 2@Te@sub 5@

Monday, November 15, 2004, 5:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: Y.K. Kim, Yonsei University, Korea
Authors: Y.K. Kim, Yonsei University, Korea
S.A. Park, Yonsei University, Korea
J.H. Beack, Yonsei University, Korea
M.K. Noh, Yonsei University, Korea
K.H. Jeong, Yonsei University, Korea
E.J. Jeong, Yonsei University, Korea
D.-H. Ko, Yonsei University, Korea
M.-H. Cho, Korea Research Institute of Standards and Science, Korea
Correspondent: Click to Email
Ge @sub 2@Sb @sub 2@Te @sub 5@ ternary alloy film is used for phase-change nonvolatile memory device. This material shows electrical switching phenomena of resistance (~10 @super 6@ times) when phase transition occurs. In this research, we investigated the changes of structural and electrical properties after the phase of film transited from amorphous state to poly crystalline state. Phase transition of the alloy film grown by RF magnetron sputtering method was induced by post annealing treatment in N @sub 2@ ambient. XRD analysis showed that as-dep. film which was amorphous state crystallizes to NaCl fcc structure at 160~170 °C. As a result of DSC experiment, the effective activation energy for this crystallization is 2.5 ±0.11eV. Sheet resistance decreased from 10 @super 9@ to 10 @super 3@ @ohm@/sq. When it was annealed at 250 °C, phase transition from NaCl fcc structure to Hexagonal structure occurred. But not only hexagonal structure, other phases-Te and GeSb @sub 2@Te @sub 4@ hexagonal structures also appeared. This phase separation phenomenon also can be shown in SPEM(Scanning Photoemission Microscopy) data. In this phase, the sheet resistance decreased to 10 @super 2@ @ohm@/sq. AFM and XRR results show that while the crystallization occurs the surface roughening proceeds and thickness is decreased so that eventually the density increases. Hall measurement results indicate that resistance change is related to the change of hall concentration which is due to structure transition.