Early Development of Graphene Electronics

Note: Some personal information has been removed; original documents are available upon request.Graphene has recently emerged as a material likely to complement or eventually succeed silicon in electronics. From 2001 to 2004, groundbreaking research was pursued behind the scenes at Georgia Tech; various directions were explored, including exfoliation techniques and CVD growth, but epitaxial graphene on silicon carbide emerged as the most viable route. This document provides archival information that may otherwise be difficult to obtain, including two proposals on file with the NSF, submitted in 2001 and 2003, and the first graphene patent, filed in 2003. The 2001 document proposes much of the graphene research carried out during this decade, and the 2003 proposal includes the data that was eventually published in J. Phys. Chem. B in Dec. 2004

Thermoelectric effect in high mobility single layer epitaxial graphene

The thermoelectric response of high mobility single layer epitaxial graphene on silicon carbide substrates as a function of temperature and magnetic field have been investigated. For the temperature dependence of the thermopower, a strong deviation from the Mott relation has been observed even when the carrier density is high, which reflects the importance of the screening effect. In the quantum Hall regime, the amplitude of the thermopower peaks is lower than a quantum value predicted by theories, despite the high mobility of the sample. A systematic reduction of the amplitude with decreasing temperature suggests that the suppression of the thermopower is intrinsic to Dirac electrons in graphene.Comment: 5 pages, 4 figure

Epigraphene : epitaxial graphene on silicon carbide

This article presents a review of epitaxial graphene on silicon carbide, from fabrication to properties, put in the context of other forms of graphene.Comment: 46 pages, 322 references, 35 figures. Submitted December 201

Measurement of magnetic moments of free Bi\u3ci\u3eN\u3c/i\u3eMn\u3ci\u3eM\u3c/i\u3e clusters

Magnetic properties of free BiNMnM clusters (N=2–20, M=0–7) are determined from Stern-Gerlach deflections at low temperature (46.5 K). Pure bismuth clusters with odd number of atoms exhibit paramagnetic deflections. The addition of manganese atoms produces a ferromagnetic response which is strongly size dependent. Certain combinations have very large magnetic moments such as Bi5Mn3, Bi9 Mn4, Bi10Mn5, and Bi12Mn6

Spin Uncoupling in Free Nb Clusters: Support for Nascent Superconductivity

Molecular beam Stern-Gerlach deflection measurements on Nb clusters (NbN, N \u3c100) show that at very low temperatures the odd-N clusters deflect due to a single unpaired spin that is uncoupled from the cluster. At higher temperatures the spin is coupled and no deflections are observed. Spin uncoupling occurs concurrently with the transition to the recently found ferroelectric state, which has superconductor characteristics [Science 300, 1265 (2003)]. Spin uncoupling (also seen in V, Ta, and Al clusters) is analogous to the reduction of spin-relaxation rates observed in bulk superconductors below Tc

Magnetic Moments and Adiabatic Magnetization of Free Cobalt Clusters

Magnetizations and magnetic moments of free cobalt clusters CoN (12\u3c N \u3c200) in a cryogenic (25 K ≤ T ≤ 100 K) molecular beam were determined from Stern-Gerlach deflections. All clusters preferentially deflect in the direction of the increasing field and the average magnetization resembles the Langevin function for all cluster sizes even at low temperatures. We demonstrate in the avoided crossing model that the average magnetization may result from adiabatic processes of rotating and vibrating clusters in the magnetic field and that spin relaxation is not involved. This resolves a longstanding problem in the interpretation of cluster beam deflection experiments with implications for nanomagnetic systems in general

Weak antilocalization in epitaxial graphene: evidence for chiral electrons

Transport in ultrathin graphite grown on silicon carbide is dominated by the electron-doped epitaxial layer at the interface. Weak anti-localization in 2D samples manifests itself as a broad cusp-like depression in the longitudinal resistance for magnetic fields 10 mT$< B <$ 5 T. An extremely sharp weak-localization resistance peak at B=0 is also observed. These features quantitatively agree with graphene weak-(anti)localization theory implying the chiral electronic character of the samples. Scattering contributions from the trapped charges in the substrate and from trigonal warping due to the graphite layer on top are tentatively identified. The Shubnikov-de Haas oscillations are remarkably small and show an anomalous Berry's phase.Comment: 5 pages, 4 figures. Minor change