arXiv subjects

Gong Gu

Publications and source records attributed to Gong Gu.

5 recordsLinked to original sources

arXiv2024

Ultraclean suspended graphene by radiolysis of adsorbed water

Access to intrinsic properties of a 2D material is challenging due to the absence of a bulk that would dominate over surface contamination, and this lack of bulk also precludes effective conventional cleaning methods that are almost always sacrificial. Suspended graphene and carbon contaminants represent the most salient challenge. This work has achieved ultraclean graphene, attested by electron energy loss (EEL) spectra unprecedentedly exhibiting fine-structure features expected from bonding and band structure. In the cleaning process in a transmission electron microscope, radicals generated by radiolysis of intentionally adsorbed water remove organic contaminants, which would otherwise be feedstock of the notorious electron irradiation induced carbon deposition. This method can be readily adapted to other experimental settings and other materials, to enable previously inhibited undertakings that rely on the intrinsic properties or ultimate thinness of 2D materials. Importantly, the method is surprisingly simple and robust, easily implementable with common lab equipment.

cond-mat.mtrl-sci↗

arXiv2014

Friedel Oscillation-Induced Energy Gap Manifested as Transport Asymmetry at Monolayer-Bilayer Graphene Boundaries

We show that Friedel charge oscillation near an interface opens a gap at the Fermi energy for electrons with wave vectors perpendicular to the interface. If the Friedel gaps on two sides of the interface are different, a nonequlibrium effect - shifting of these gaps under bias - leads to asymmetric transport upon reversing the bias polarity. The predicted transport asymmetry is revealed by scanning tunneling potentiometry at monolayer-bilayer interfaces in epitaxial graphene on SiC (0001). This intriguing interfacial transport behavior opens a new avenue towards novel quantum functions such as quantum switching.

cond-mat.mes-hall↗

arXiv2013

SymFET: A Proposed Symmetric Graphene Tunneling Field Effect Transistor

In this work, an analytical model to calculate the channel potential and current-voltage characteristics in a Symmetric tunneling Field-Effect-Transistor (SymFET) is presented. The current in a SymFET flows by tunneling from an n-type graphene layer to a p-type graphene layer. A large current peak occurs when the Dirac points are aligned at a particular drain-to- source bias VDS . Our model shows that the current of the SymFET is very weakly dependent on temperature. The resonant current peak is controlled by chemical doping and applied gate bias. The on/off ratio increases with graphene coherence length and doping. The symmetric resonant peak is a good candidate for high-speed analog applications, and can enable digital logic similar to the BiSFET. Our analytical model also offers the benefit of permitting simple analysis of features such as the full-width-at-half-maximum (FWHM) of the resonant peak and higher order harmonics of the nonlinear current. The SymFET takes advantage of the perfect symmetry of the bandstructure of 2D graphene, a feature that is not present in conventional semiconductors.

cond-mat.mes-hall↗

arXiv2011

Single-Particle Tunneling in Doped Graphene-Insulator-Graphene Junctions

The characteristics of tunnel junctions formed between n- and p-doped graphene are investigated theoretically. The single-particle tunnel current that flows between the two-dimensional electronic states of the graphene (2D-2D tunneling) is evaluated. At a voltage bias such that the Dirac points of the two electrodes are aligned, a large resonant current peak is produced. The magnitude and width of this peak is computed, and its use for devices is discussed. The influence of both rotational alignment of the graphene electrodes and structural perfection of the graphene is discussed.

cond-mat.mes-hall↗

arXiv2009

Morphology of Graphene on SiC(000-1) Surfaces

Graphene is formed on SiC(000-1) surfaces (the so-called C-face of the crystal) by annealing in vacuum, with the resulting films characterized by atomic force microscopy, Auger electron spectroscopy, scanning Auger microscopy and Raman spectroscopy. Morphology of these films is compared with the graphene films grown on SiC(0001) surfaces (the Si-face). Graphene forms a terraced morphology on the C-face, whereas it forms with a flatter morphology on the Si-face. It is argued that this difference occurs because of differing interface structures in the two cases. For certain SiC wafers, nanocrystalline graphite is found to form on top of the graphene.

cond-mat.mtrl-sci↗