Sahu Smriti, Sharma Rituraj, Adarsh K V, Manivannan Anbarasu
Appl Opt. 2018 Jan 10;57(2):178-184. doi: 10.1364/AO.57.000178.
Rapid and reversible switching between amorphous and crystalline phases of phase-change material promises to revolutionize the field of information processing with a wide range of applications including electronic, optoelectronics, and photonic memory devices. However, achieving faster crystallization is a key challenge. Here, we demonstrate femtosecond-driven transient inspection of ultrafast crystallization of as-deposited amorphous GeSbTe and GeSbTe thin films induced by a series of 120 fs laser pulses. The snapshots of phase transitions are correlated with the time-resolved measurements of change in the absorption of the samples. The crystallization is attributed to the reiterative excitation of an intermediate state with subcritical nuclei at a strikingly low fluence of 3.19 mJ/cm for GeSbTe and 1.59 mJ/cm for GeSbTe. Furthermore, 100% volumetric crystallization of GeSbTe was achieved with the fluence of 4.78 mJ/cm, and also reamorphization is seen for a continuous stimulation at the same repetition rate and fluence. A systematic confirmation of structural transformations of all samples is validated by Raman spectroscopic measurements on the spots produced by the various excitation fluences.
相变材料在非晶相和晶相之间实现快速且可逆的转换，有望彻底改变信息处理领域，其应用范围广泛，涵盖电子、光电子和光子存储设备等。然而，实现更快的结晶是一项关键挑战。在此，我们展示了由一系列120飞秒激光脉冲诱导的飞秒驱动的瞬态检测，用于研究沉积态非晶GeSbTe和GeSbTe薄膜的超快结晶过程。相变的瞬间图像与样品吸收变化的时间分辨测量结果相关联。结晶归因于对具有亚临界核的中间态的反复激发，对于GeSbTe，激发阈值低至3.19 mJ/cm²，对于GeSbTe，激发阈值低至1.59 mJ/cm²。此外，在4.78 mJ/cm²的能量密度下实现了GeSbTe的100%体积结晶，并且在相同重复率和能量密度下连续刺激时也观察到了再非晶化现象。通过对不同激发能量密度产生的光斑进行拉曼光谱测量，对所有样品的结构转变进行了系统确认。
