振动模式扫描极化力显微镜对氧化石墨烯热还原过程的实时原位监控

通过调控GO(graphene oxide,GO)的还原程度可以得到电学性质不同的石墨烯,能更广泛地应用于纳米电子器件的构造中。本文利用振动模式扫描极化力显微镜(vibrating scanning polarization force microscopy,VSPFM)实时监控了氧化石墨烯的热还原反应过程。实验中发现GO的热还原启动逐点发生,在同一片中间还原态GO上的局域介电常数分布不均匀,而不同片的GO还原反应的进程也有差别。发现GO和还原的GO(reduced grapheneoxide,rGO)在VSPFM中呈现出不同的表观高度,由此可以在云母和玻璃以及同一片GO上直接辨别GO和rGO。这种实时原位监控单片层GO的各个还原状态的方法将推动它在纳米电子学领域的多种应用。

Modulation of Photonic Bandgap and Localized States by Dielectric Constant Contrast and Filling Factor in Photonic Crystals

The band structure of 2D photonic crystals (PCs) and localized states resulting from defects are analyzed by finite-difference time-domain (FDTD) technique and Padé approximation.The effect of dielectric constant contrast and filling factor on photonic bandgap (PBG) for perfect PCs and localized states in PCs with point defects are investigated.The resonant frequencies and quality factors are calculated for PCs with different defects.The numerical results show that it is possible to modulate the location,width and number of PBGs and frequencies of the localized states only by changing the dielectric constant contrast and filling factor.