Influence of Hydrogenation on the Amorphous-to-Crystalline Phase Transition Characteristics of Ge2Sb2Te5 and Ge8Sb2Te11 Thin Films

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The characteristics of amorphous-to-crystalline phase transformation in the hydrogenated Ge2Sb2Te5 and Ge8Sb2Te11 thin films were investigated by X-ray diffraction (XRD), optical transmittance ($T_{\text{OP}}$), and nano-pulse reflection response. The hydrogenation was conducted under a H2 pressure ($P_{\text{H}}$) of 20 atm and an annealing temperature ($T_{\text{a}}$) of 100 and 200 °C. The incorporation of hydrogens into the chalcogenide films was verified by secondary ion mass spectrometry (SIMS) depth profile. The variation of H-signals in the SIMS profile was apparently compensated by the variation of Sb and Ge signals rather than by that of Te. The results measured in hydrogenated films were compared with those in the as-deposited and post-annealed films at $T_{\text{a}}$ for 4 h in pure N2 atmosphere. The hydrogenation effects led to very different dependences between the Ge2Sb2Te5 and Ge8Sb2Te11 thin films. Amorphous-to-crystalline phase-transition speed was evaluated via nano-pulse reflection response measurement. The hydrogenation inhibited the transition of Ge2Sb2Te5 but hardly affected that of Ge8Sb2Te11. In particular, the amorphous-to-crystalline transition in the hydrogenated Ge8Sb2Te11 film was very stable.
2008-07-25