Layer-by-layer transfer of multiple, large area sheets of graphene grown in multilayer stacks on a single SiC wafer.

Here we report a technique for transferring graphene layers, one by one, from a multilayer deposit formed by epitaxial growth on the Si-terminated face of a 6H-SiC substrate. The procedure uses a bilayer film of palladium/polyimide deposited onto the graphene coated SiC, which is then mechanically peeled away and placed on a target substrate. Orthogonal etching of the palladium and polyimide leaves isolated sheets of graphene with sizes of square centimeters. Repeating these steps transfers additional sheets from the same SiC substrate. Raman spectroscopy, scanning tunneling spectroscopy, low-energy electron diffraction and X-ray photoelectron spectroscopy, together with scanning tunneling, atomic force, optical, and scanning electron microscopy reveal key properties of the materials. The sheet resistances determined from measurements of four point probe devices were found to be ∼2 kΩ/square, close to expectation. Graphene crossbar structures fabricated in stacked configurations demonstrate the versatility of the procedures.

Conjugated carbon monolayer membranes: methods for synthesis and integration.

Monolayer membranes of conjugated carbon represent a class of nanomaterial with demonstrated uses in various areas of electronics, ranging from transparent, flexible, and stretchable thin film conductors, to semiconducting materials in moderate and high-performance field-effect transistors. Although graphene represents the most prominent example, many other more structurally and chemically diverse systems are also of interest. This article provides a review of demonstrated synthetic and integration strategies, and speculates on future directions for the field.

Magnetoresistance in single-layer graphene: weak localization and universal conductance fluctuation studies.

We report measurements of magnetoresistance in single-layer graphene as a function of gate voltage (carrier density) at 250 mK. By examining signatures of weak localization (WL) and universal conductance fluctuations (UCF), we find a consistent picture of phase coherence loss due to electron-electron interactions. The gate dependence of the elastic scattering terms suggests that the effect of trigonal warping, i.e. the nonlinearity of the dispersion curves, may be strong at high carrier densities, while intra-valley scattering may dominate close to the Dirac point. In addition, a decrease in UCF amplitude with decreasing carrier density can be explained by a corresponding loss of phase coherence.