Structural and band tail state photoluminescence properties of amorphous SiC films with different amounts of carbon

Amorphous silicon carbide films are deposited by the plasma enhanced chemical vapour deposition technique,and optical emissions from the near-infrared to the visible are obtained.The optical band gap of the films increases from 1.91 eV to 2.92 eV by increasing the carbon content,and the photoluminescence(PL) peak shifts from 1.51 eV to 2.16 eV.The band tail state PL mechanism is confirmed by analysing the optical band gap,PL intensity,the Stocks shift of the PL,and the Urbach energy of the film.The PL decay times of the samples are in the nanosecond scale,and the dependence of the PL lifetime on the emission energy also supports that the optical emission is related to the radiative recombination in the band tail state.     

灯笼图的可定向嵌入亏格分布

本文主要利用联树法研究了图的亏格多项式,得到了一类新图(灯笼图)的嵌入亏格分布.证明了灯笼图和偶梯图的亏格分布具有相同的递推关系,从而得到了灯笼图的嵌入亏格分布的精确解.     

有向图在可定向曲面上的嵌入性

Bonnington,Conder和Morton在2002年给出了有向图嵌入亏格的基本性质,并提出了如下问题:如何刻划有向嵌入是上可嵌入的?是否存在类似刻划图的上可嵌入中使用的叮裂树的结果?受此问题的启发,收稿给出了一类有向图在可定向曲面上是上可嵌入的性质.作为直接推论,可得到已有的反棱境图是上可嵌入的结论.另外得到了一些新的上可嵌入的图类.