Nanoscale phase change on Ge2Sb2Te5 thin films induced by optical near fields with photoassisted scanning tunneling microscope
Nanoscale phase change on Ge2Sb2Te5 thin films induced by optical near fields with photoassisted scanning tunneling microscope
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DOI：
10.1063/5.0032573
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发表时间：
2020-11-23
影响因子：
4
通讯作者：
Takeda, Jun
中科院分区：
文献类型：
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作者：
Asakawa, Kanta;Kim, Dang-il;Takeda, Jun
扫描探针显微镜与飞秒激光脉冲或太赫兹脉冲相结合，不仅在观察超快现象方面有很大的希望，而且在纳米尺度上也可以制造出理想的结构。在本研究中，我们证明了利用激光驱动的扫描隧道显微镜(STM)可以在Ge2Sb2Te5表面非热存储几个纳米尺度的相变。用飞秒激光脉冲注入STM针尖-样品结产生的光学近场照射原子平坦的Ge2Sb2Te5表面。扫描隧道显微镜的形貌图像显示，辐照后出现了很少的纳米级的丘状结构。此外，隧道电导谱显示，在5×5 nm(2)的区域内，禁带宽度增加了0.2 eV。这些结果表明，纳米晶到非晶态的相变是由STM针尖诱导的近场引起的。我们在这里提出的方法在光学存储设备的记录密度方面提供了前所未有的增加，因此，预计将促进下一代信息技术的发展。
A scanning probe microscope coupled with either femtosecond laser pulses or terahertz pulses holds great promise not only for observing ultrafast phenomena but also for fabricating desirable structures at the nanoscale. In this study, we demonstrate that a few-nanometer-scale phase change can be non-thermally stored on the Ge2Sb2Te5 surface by a laser-driven scanning tunneling microscope (STM). An atomically flat Ge2Sb2Te5 surface was irradiated with the optical near-field generated by introducing femtosecond laser pulses to the STM tip-sample junction. The STM topographic images showed that few-nanometer-scale mounds appeared after irradiation. In addition, tunneling conductance spectra showed that the bandgap increased by 0.2eV in the area of 5x5nm(2). These indicate that the nanoscale crystal-to-amorphous phase change was induced by the STM-tip-induced near field. Our approach presented here offers an unprecedented increase in the recording density of optical storage devices and is, therefore, expected to facilitate the development of next-generation information technology.