Synthesis and Optical Property Study on Graphene and Twinning Si Nanowires

Getting clean and high quality graphene samples on a target substrate is the foundation of graphene study and graphene based devices. Chemical doping is critical to enhancing electrical conductivity and making some devices. Here we systematically studied the PMMA residue on the graphene sample transferred by the typical wet transfer process. Methods were developed to effectively reduce the PMMA residue, and so that cleaner graphene samples could be achieved for devices. We report the observation of Fano-type phonon resonance using infrared Fourier transform spectroscopy at room temperature in few-layer graphene synthesized by chemical-vapor deposition on copper substrate. We subsequently demonstrate a continuous tuning of Fano line shape from antiresonance to phonon dominated by ammonia chemical doping. Making silicon an efficient light-emitting material is an important goal of silicon photonics. Here we report the observation of broadband sub-bandgap photoluminescence in silicon nanowires with a high density of stacking faults. The photoluminescence becomes stronger and exhibits a blue shift under higher laser powers.