"Electrical and Optical Properties of Nanocrystalline-Si-Dispersed Film with Periodical Modulation of Its Layer Structure"

纳米硅分散薄膜是指纳米硅分散在氧化硅薄膜中，是一种新型的可见光发光材料。然而，nc-Si分散膜通常具有低电导率，因此难以通过电流注入实现发光。在本计画中，我们的目标是同时达到高效率发光与高导电性，借由高效率发光层与低电阻率富矽层的周期性多层膜结构的形成，借由改变氧气流量来调整薄膜中的氧气含量来达成多层膜结构的形成。结果表明，高温退火后nc-Si的平均尺寸在空间上有周期性的变化，这是因为形成的nc-Si的尺寸取决于薄膜的成分。确认了由于多层结构而导致的导电性的增加，但是仅对于具有小于100 nm的周期的多层观察到多层结构的效果。这与分布布拉格反射器在800 nm波长区域的周期为1000 nm不兼容，800 nm波长是光致发光的峰值波长。这种不兼容性必须在未来解决。

Nanocrystalline (nc-) Si-dispersed films, which are the silicon oxide thin films including nc-Si dispersively, are a new light-emitting material providing high efficiency visible photolminescence. However, the nc-Si-dispersed films generally have low electrical conductivity, and thus there are difficulties in achievement of light emission by current injection. In this project, we aimed to achieve both high efficiency light emission and high conductivity simultaneously by the formation of periodical multilayers with high-efficiency light-emitting layers and low-resistivity Si-rich layers.The formation of the multilayer structure was realized by modulating oxygen content of the films through a variation of O_2 flow rate. As a result, a spacially periodical modulation of the average size of nc-Si was bought about after high-temperature thermal annealing because the size of nc-Si formed depends on the composition of the films. An increase of the conductivity due to the multilayer structure was confirmed but the effect of multilayer structure observed only for the multilayer that has a period less than 100nm. That was not compatible to the period 〜300 nm of distributed Bragg reflector for 800-nm wavelength region, which is the peak wavelength of photoluminescence. This incompatibility must be solves in future.