Ultrafast crystalline-to-amorphous phase transition in Ge2Sb2Te5 chalcogenide alloy thin film using single-shot imaging spectroscopy
Ultrafast crystalline-to-amorphous phase transition in Ge2Sb2Te5 chalcogenide alloy thin film using single-shot imaging spectroscopy
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DOI：
10.1063/1.4886969
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发表时间：
2014-06-30
影响因子：
4
通讯作者：
Katayama, Ikufumi
中科院分区：
文献类型：
--
作者：
Takeda, Jun;Oba, Wataru;Katayama, Ikufumi
利用宽带单次激发成像光谱技术在Ge_2Sb_2Te_5硫系合金薄膜中观察到了一个不可逆的从晶到非晶的超快相变。即使对于高于临界值的激光能量密度，也可以通过单次检测来测量伴随超快非晶化的吸光度变化，其中形成了永久性非晶化标记。发现观察到的达到非晶化的上升时间类似于130-200 fs，这与八面体GeTe 6结构中A（1）声子频率的半周期非常一致。这一结果有力地表明，超快非晶化可以归因于Ge原子从八面体结构到四面体结构的重排。最后，根据吸光度变化与激光能量密度的关系，讨论了光致非晶相的稳定性。(C)2014 AIP Publishing LLC.
We have observed an irreversible ultrafast crystalline-to-amorphous phase transition in Ge2Sb2Te5 chalcogenide alloy thin film using broadband single-shot imaging spectroscopy. The absorbance change that accompanied the ultrafast amorphization was measured via single-shot detection even for laser fluences above the critical value, where a permanent amorphized mark was formed. The observed rise time to reach the amorphization was found to be similar to 130-200 fs, which was in good agreement with the half period of the A(1) phonon frequency in the octahedral GeTe6 structure. This result strongly suggests that the ultrafast amorphization can be attributed to the rearrangement of Ge atoms from an octahedral structure to a tetrahedral structure. Finally, based on the dependence of the absorbance change on the laser fluence, the stability of the photoinduced amorphous phase is discussed. (C) 2014 AIP Publishing LLC.