Xu Zemin, Chen Chaonan, Wang Zhewei, Wu Ke, Chong Haining, Ye Hui
State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University Hangzhou 310027 P. R. China
RSC Adv. 2018 Jun 8;8(37):21040-21046. doi: 10.1039/c8ra01382a. eCollection 2018 Jun 5.
In this work, phase change chalcogenide GeSbTe (GST) thin films were fabricated by magnetron sputtering. The optical properties, especially the optical constants (refractive index and extinction coefficient), of such alloys were systematically studied by investigating their thermally and photo-thermally induced switching between different phases. The results show that GST films are highly tunable in microstructure and optical constants, either by post-annealing at 160 °C, 200 °C, 250 °C and 350 °C, respectively, or by laser irradiation of 1 mW, 3 mW, 5 mW and 10 mW power with beam diameter of 7 μm at 532 nm, respectively. From the structural analysis, we can clearly observe different crystallinities and chemical bonding in the different post-treated GST films. The optical constants of GST films under various phases were obtained from spectrophotometry, by fitting their transmittance data with the Tauc-Lorentz (TL) dispersion model. The refractive index and extinction coefficient exhibit notable change upon annealing and laser irradiation, specifically at 1550 nm, from 3.85 (amorphous) to 6.5 (crystalline) in refractive index. The optical constants have been proved capable of fine tuning the laser irradiation method. Hence, the pronounced adjustability in optical properties due to rapid and repeatable phase change render GST suitable for tunable photonic devices.
在本工作中，通过磁控溅射制备了相变硫系化合物锗锑碲（GST）薄膜。通过研究此类合金在不同相之间的热诱导和光热诱导切换，系统地研究了它们的光学性质，特别是光学常数（折射率和消光系数）。结果表明，GST薄膜在微观结构和光学常数方面具有高度可调性，既可以分别在160°C、200°C、250°C和350°C下进行后退火，也可以分别用功率为1 mW、3 mW、5 mW和10 mW、光束直径为7μm的激光在532 nm波长下进行照射。通过结构分析，我们可以清楚地观察到不同后处理GST薄膜中的不同结晶度和化学键合。通过用Tauc-Lorentz（TL）色散模型拟合其透射率数据，从分光光度法获得了不同相下GST薄膜的光学常数。折射率和消光系数在退火和激光照射时表现出显著变化，特别是在1550 nm处，折射率从3.85（非晶态）变为6.5（晶态）。光学常数已被证明能够通过激光照射方法进行微调。因此，由于快速且可重复的相变导致的光学性质的显著可调性使GST适用于可调谐光子器件。
