Fabrication and analysis of optical properties in spherical microcavity using nc-Si dispersed films

本研究旨在建立一种新型的含硅纳米晶的微球光学腔的制备方法。然后从腔量子电动力学的角度，从自发光与微腔相互作用的角度分析了它们的光学性质。采用射频溅射法和热氧化法分别制备了非晶态（α-）SiOx和α- sio_2薄膜。采用钨基板，以保证耐热性。膜的厚度为5μm。溅射靶材为带有硅尖的SiO_2圆盘。通过改变硅尖的数量来控制薄膜的组成。利用电子束拉伸系统将薄膜微细加工成岛状图案。在膜上形成了直径为0.5 ~ 20μm的铬圆形图案。然后用cf_4等离子体反应离子刻蚀法刻蚀薄膜。用扫描电镜对所制备的柱形进行了检查。SiOx薄膜的柱岛加热到软化点附近，即1200-1600℃。为了避免氧化，在Mo电池中插入的样品处于氩气流动的气氛中。最佳加热条件为1600℃，加热2分钟。在这种条件下，柱状岛屿成功地变形成半球形。然而，在那个时间点上，分析它们的光学性质是困难的。

This research work aimed to establish a novel fabrication method of microsphere optical cavity including silicon nanocrystallites. Then their optical properties are analyzed from a viewpoint of cavity quantum electrodynamic theory with respect to an interaction between spontaneously emitted light and microcavity.Amorphous (α-)SiOx and α-SiO_2 films as bases of samples are deposited using a radio-frequency sputtering method and a thermal oxidation method, respectively. Tungsten substrates are used in order to ensure heat resistance. The thickness of the films were 5μm. The sputtering target was SiO_2 disc with Si tips on it. The composition of the films deposited was controlled by varying the number of Si tips. An electron-beam drawing system was used for microfabrication of the films into island-like patterns. Circular patterns of chromium with 0.5-20μm in diameter were formed on the film by a lift-off process. The film was then etched by CF_4-plasma reactive ion etching. The columner patterns fabricated were checked by scanning electron microscope. Those columner islands of SiOx fims were heated up to around softening point, that is, 1200-1600℃. The samples inserted in a Mo cell were in an atmosphere of Ar gas flow in order to avoid oxidation. The optimal condition of heating was 2 minutes at 1600℃. Under this condition, the columner islands were successfully deformed into hemispherical shapes. However, analysis of their optical properties was difficult at that point in time.