Single layer graphene has shown promising applications in fast and sensitive optoelectronic applications such as optical modulators and photodetectors. Twisted bilayer graphene has the potential to further improve the performances of such graphene devices due to its modified electronic band structure. However, the lack of synthesis method for large-area isolated twisted bilayer graphene has limited device applications. After a brief review of recent development in single layer graphene optoelectronic property and photodetectors, we discuss unique optical properties of twisted bilayer graphene. We then show two methods that we have developed to fabricate large-size twisted bilayer graphene islands. The first method uses chemical vapor deposition; the other method utilizes mechanical stacking of two large-size single layer graphene hexagons. The realization of such twisted bilayer graphene samples enables new development of novel graphene-based devices.
This paper demonstrates the sectioning of chemically synthesized, single-crystalline microplates of gold with an ultramicrotome to produce single-crystalline nanowires. This method produces collinearly aligned nanostructures with small, regular changes in dimension with each consecutive cross-section. The diamond knife cuts cleanly through microplates 100 nm thick without bending the resulting nanowire, and cuts through the sharp edges of a crystal to
generate nanoscale tips. This paper demonstrates that the smooth surface of the single-crystalline gold nanowires allows
them to guide plasmons with lower loss than rough, polycrystalline nanowires, and that the sharp tips on the singlecrystalline
nanowires serve as optical antenna that selectively couple light into the nanowire at the resonance frequency of the sharp tip.
We present a novel approach to enhance light emission in Si and demonstrate sub-bandgap light-emitting diodes (LED) based on the introduction of point defects. Ion implantation, pulsed laser melting and rapid thermal annealing were used to create LEDs containing self-interstitial-rich optically active regions. Procedures to fabricate LEDs on a bulk silicon substrate and on a silicon-on-insulator (SOI) wafer will be presented, and methods to improve device performances will be discussed. The control and utilization of point defects represents a new approach toward creating Si in a stable, optically active form for Si-based optoelectronics.