Development and Application of Bule Light-Emitting Nanocrystalline Si Materials

在硅纳米结构中，量子尺寸效应有望产生新的光学和电学性质来取代现有的材料。本研究的目的就是开发这样的新材料和新器件。纳米硅(nc-Si)提供了一种将硅制备成Am尺度的方法。我们开发了一种成功的制备微晶尺寸可控的纳米硅的工艺，并在室温下展示了纳米硅的蓝光发射。本课题的主要研究成果如下：(1)利用Er作为晶核中心，实现了对a-Si基硅纳米晶尺寸依赖的蓝光发射的控制。我们已经制备了一系列尺寸从3 nm到10am的nc-Si样品最小的微晶尺寸为2.7 nm，一个含-1000个原子的硅点。Nc-Si层在晶粒度和光电性能上都是均匀的，并在1.54微米处出现一个蓝色发射带和一个锐利的峰，这是由壳内t…引起的在室温下，Er原子中有更多的跃迁。我们发现蓝光发射随着尺寸的减小而向高能方向移动。通过对纳米硅纳米晶尺寸的控制，首次证明了纳米硅中量子尺寸效应的存在，证明了纳米硅的吸收光谱和反射光谱都随着纳米晶尺寸的减小而向高能方向移动。由间接半导体Si中的直接跃迁引起的量子尺寸效应很好地解释了这种位移。我们提出了有序(nc-Si相)/无序(a-Si相)量子点系统的新模型来理解nc-Si材料中电子的尺寸效应。理论计算表明，由于尺寸减小，k选择规则的修正增强了直接跃迁导致蓝光发射，由该模型计算的吸收光谱和反射光谱都表现出尺寸效应，并与我们的实验结果很好地吻合。(4)室温运转的掺Er纳米硅激光器我们在硅衬底上制备了掺Er纳米硅光波导，并在光泵浦下实现了室温下1.54 nm的受激发射。这是实现全硅激光器的第一个突破。较少

In Si nanostructures, quantum size effects are expected to give rise to new optical and electrical properties to replace present materials. The motivation of this study is to develop such new materials and new devices. Nanocrystalline Si (nc-Si) provides a way to fabricate Si into am scale. We have developed a successful process to fabricate nc-Si with controllable crystallite sizes and demonstrated a blue light emission from nc-Si at room temperature. Main results of this project are shown in bellow.(1).Size-dependent blue light emission from nc-SiSize control of Si nanocrystallites formed in a-Si matrix is achieved by using Er as a nucleation center. We have fabricated a series of nc-Si samples with size from 3 nm to 10 am. The smallest crystallite size was 2.7 nm, a Si dot including .-l000 atoms. The nc-Si layers are homogeneous both in the crystallite size and in the optoelectronic properties and show a blue emission band and a sharp peak at 1.54mum which is caused by intra-shell t … More ransitions in Er atoms up to room temperature. We showed that the blue emission shift to higher energies with decreasing size. The value of the shift is in good agreement with the absorption data and could be explained by a novel quantum size effect.(2).First evidence of quantum size effect in ne-SiBy controlling the nanocrystallite size of nc-Si, we demonstrated that both the absorption and reflection spectra of nc-Si shift to higher energy side with decreasing crystallite size. The shift was well explained by the quantum size effect which originates direct transitions in the indirect semiconductor Si. The nc-Si is a promising material with size-tunable optical and electronic properties.(3).A new model of nc-Si/a-Si quantum dot systemWe proposed a new model of order (nc-Si phase)/disorder (a-Si phase) quantum dots system to understand the size effect of electrons in nc-Si materials. A theoretical calculation indicates that direct transitions enhanced by a modification of k-selection rules due to the size reduction result in the blue light emission, Both the absorption and reflection spectra calculated by the proposed model show size effect and are in good agreement with our experimental results.(4).An Er-doped nc-Si laser operated at room temperatureWe have fabricated Er-doped nc-Si waveguides on Si substrates and demonstrated a stimulated emission at 1.54 .tm at room temperature under optical pumping. This is the first breakthrough of realizing an all-Si laser. Less