Control of Anisotropy in Nanostructured Silicon by Linearly Polarized Light

纳米结构多孔硅样品在电化学腐蚀过程中，经线偏振光照射后表现出光学各向异性。本研究项目旨在阐明各向异性形成的机制，并将其应用于新型光学器件。主要研究结果如下：1.折射率各向异性的观察多孔硅层中的光学各向异性已经被几个研究小组基于他们在光致发光中的线偏振度的结果报道。在这个项目中，我们首次观察到折射率的显著各向异性。各向异性使得最大折射率出现在偏离最大线性偏振度90度的方向上。这可以通过假设大的硅结构负责折射率各向异性而小的结构控制发光各向异性来解释。激发波长对发光的影响 ...更多信息 发光各向异性我们已经观察到发光各向异性很大程度上受激发波长的影响。我们的实验结果表明，这不是由于氧化物发光的影响，而是源于深度不稳定性.红外激光辐照样品中强各向异性的实验观察和计算机模拟我们用1.06 μ mNd：YAG激光器作光源，获得了很强的发光各向异性。基于平面内线性振子分布的二维模型的计算机仿真结果可以很好地再现.阳极氧化条件的影响我们已经表明，发光多孔硅样品可以得到使用极稀的HF溶液与HF浓度低至0.1%。没有显着的发光各向异性，但是，已观察到在这些样品中，这意味着阳极氧化电流密度在很大程度上影响各向异性的形成。少

Nanostructured porous silicon samples exhibit optical anisotropy after being irradiated with linearly polarized light while they are etched electrochemically. This research project aims at clarifying the mechanism for the formation of anisotropy and applying this to novel optical devices. Major results are summarized as follows:1. Observation of anisotropy in refractive indicesThe optical anisotropy in porous silicon layers has been reported by several research groups based on their results on the degree of linear polarization in photoluminescence. In this project, we have observed a significant anisotropy in refractive indices for the first time. The anisotropy is such that the largest index appears in a direction 90-degree off that of the largest degree of linear polarization. This can be explained by assuming that large silicon structures are responsible for refractive index anisotropy while small structures govern luminescence anisotropy.2. Effect of excitation wavelengths on lumin … More escence anisotropyWe have observed that the luminescence anisotropy is affected largely by the excitation wavelength. Our experimental results show that this is not due to the effect of luminescence from oxides but is originating from depth inhomogeneity.3. Experimental observation and computer simulation of the strong anisotropy in samples irradiated with infrared laser lightWe have used a 1.06-μm Nd : YAG laser of relatively high intensity as an illumination source and obtained very strong luminescence anisotropy. The result can be reproduced well by computer simulation based on a two-dimensional model in which linear oscillators are distributed in a plane.4. Effect of anodization conditionsWe have shown that luminescent porous silicon samples can be obtained by using extremely dilute HF solutions with HF concentrations down to 0.1%. No significant luminescence anisotropy, however, has been observed in these samples, implying that anodization current density largely affects the formation of anisotropy. Less