Production and Characterization of Carbon Nanoscrolls
Carbon nanoscrolls (CNS) are graphene sheets wrapped spirally into continuous tubular structures similar to multiwalled carbon nanotubes (MWNT). Contrary to MWNTs however, the interior layers of a CNS are composed of a single graphene sheet and thus all connected. This fundamental difference is expected to manifest itself in several advantages for electronic, chemical, and mechanical properties.
Research into nanoscroll properties has lagged considerably behind graphene and carbon nanotubes, due to the difficulty of fabricating these structures. We build upon previous work demonstrating nanoscroll formation from single layer graphene sheets on silicon/silicon-oxide substrates using chemical vapor deposition (CVD) produced graphene. It is found that CVD graphene can considerably improve nanoscroll formation yield over exfoliated material.
We also investigate the use of carbon nanotubes deposited onto single layer graphene sheets as a method to initiate nanoscroll formation and produce novel nested nanotube-nanoscroll hybrid structures. An aligned MWNT transfer process is developed and used to produce the first nested nanotube-nanoscroll hybrid. Some possible future applications of these interesting materials are discussed.
Scrolling of suspended graphene sheets is investigated by transferring CVD graphene onto TEM grids. It is found that the suspended regions of graphene spontaneously form carbon nanoscrolls. The nanoscrolls are characterized using transmission electron microscopy and the presence of a continuous, tubular structure is confirmed by electron diffraction. This scrolling process, assisted by focused ion beam cutting of the suspended sheets may provide an avenue to controlling chirality and dimensionality of carbon nanoscrolls, which is not yet demonstrated.
Finally, single layer graphene cantilevers are found to be stabilized by MWNTs positioned at the end of the structure. Oscillations of these structures under electron beam radiation are shown, and thermal fluctuation-driven vibrations are discussed. Graphene mechanics have been previously studied by fabricating doubly and singly clamped beams (cantilevers); however, few examples of single layer graphene cantilevers exist. Graphene provides an interesting system to study mechanics, as it is at the atomic limit of material thickness. Our method of MWNT stabilization shows a promising avenue to study mechanics of this novel material.