Effects of etching conditions on surface morphology of periodic inverted trapezoidal patterned Si(100) substrate

In this paper, the anisotropic etching process of Si(100) wafers in tetramethyl ammonium hydroxide (TMAH) solution with isopropyl alcohol (IPA) is investigated in detail. An inverted trapezoidal pattern is developed. A series of experiments are performed by changing TMAH concentration, IPA concentration, etching temperature and etching time. The structure of inverted trapezoidal patterns and roughness of the bottom surface are characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results show that with TMAH concentration increases, the roughness of bottom surface will decrease. The addition of IPA into TMAH solution improves the morphology of the bottom surface significantly. Low temperature is beneficial to get a smooth bottom surface. Furthermore, etching time can change the bottom surface roughness. A model is proposed to explain the etching processes. The hillock area ratio of the bottom surface has the same tendency as the etching area ratio. Finally, smooth silicon inverted trapezoidal patterns are obtained for epitaxial growth of GaN-based light emitting diode (LED) devices.     

Cu-In-S三元量子点的合成及其性能调控

采用前驱体分解法制备了Cu-In-S量子点,研究了制备工艺对Cu-In-S量子点的形貌以及光学性能的影响。实验结果表明,反应时间和反应温度可影响Cu-In-S纳米颗粒的尺寸和光学性能。随时间增加,Cu-In-S粒径变大,同时会伴随着棒状晶体的出现,荧光发射谱的峰位发生红移。随反应温度升高,纳米晶的形核速率和长大速率增加,并且粒径也有增大,纳米晶的形状可以由单一的球形变为球形与棒状的混合,荧光谱峰位亦会发生红移。X射线光电子能谱分析表明,所制备颗粒为CuInS2纳米晶。为进一步制备无毒量子点发光器件(QLEDs)奠定了基础。