Search results for "Nanoribbons"

Charge transport mechanism in networks of armchair graphene nanoribbons

2020

In graphene nanoribbons (GNRs), the lateral confinement of charge carriers opens a band gap, the key feature to enable novel graphene-based electronics. Successful synthesis of GNRs has triggered efforts to realize field-effect transistors (FETs) based on single ribbons. Despite great progress, reliable and reproducible fabrication of single-ribbon FETs is still a challenge that impedes applications and the understanding of the charge transport. Here, we present reproducible fabrication of armchair GNR-FETs based on a network of nanoribbons and analyze the charge transport mechanism using nine-atom wide and, in particular, five-atom-wide GNRs with unprecedented conductivity. We show formati…

Hysteresis in graphene nanoribbon field-effect devices

2020

Hysteresis in the current response to a varying gate voltage is a common spurious effect in carbon-based field effect transistors. Here, we use electric transport measurements to probe the charge transport in networks of armchair graphene nanoribbons with a width of either 5 or 9 carbon atoms, synthesized in a bottom-up approach using chemical vapor deposition. Our systematic study on the hysteresis of such graphene nanoribbon transistors, in conjunction with temperature-dependent transport measurements shows that the hysteresis can be fully accounted for by trapping/detrapping carriers in the SiO2 layer. We extract the trap densities and depth, allowing us to identify shallow traps as the …

A new on-surface synthetic pathway to 5-armchair graphene nanoribbons on Cu(111) surfaces

2017

We report a new pathway to fabricate armchair graphene nanoribbons with five carbon atoms in the cross section (5-AGNRs) on Cu(111) surfaces. Instead of using haloaromatics as precursors, the 5-AGNRs are synthesized via a surface assisted decarboxylation reaction of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA). The on-surface decarboxylation of PTCDA can produce extended copper–perylene chains on Cu(111) that are able to transform into graphene nanoribbons after annealing at higher temperatures (ca. 630 K). Due to the low yield (ca. 20%) of GNRs upon copper extrusion, various gases are introduced to assist the transformation of the copper–perylene chains into the GNRs. Typical redu…

Phase Transitions in Spin-Crossover Thin Films Probed by Graphene Transport Measurements

2016

Future multi-functional hybrid devices might combine switchable molecules and 2D material-based devices. Spin-crossover compounds are of particular interest in this context since they exhibit bistability and memory effects at room temperature while responding to numerous external stimuli. Atomically-thin 2D materials such as graphene attract a lot of attention for their fascinating electrical, optical, and mechanical properties, but also for their reliability for room-temperature operations. Here, we demonstrate that thermally-induced spin-state switching of spin-crossover nanoparticle thin films can be monitored through the electrical transport properties of graphene lying underneath the f…

Solution and on-surface synthesis of structurally defined graphene nanoribbons as a new family of semiconductors.

2018

Graphene nanoribbons (GNRs) with various structures and properties can be synthesized in solution or on surface.

Bottom-up realization and electrical characterization of a graphene-based device.

2016

We propose a bottom-up procedure to fabricate an easy-to-engineer graphene-based device, consisting of a microstrip-like circuit where few-layer graphene nanoplatelets are used to contact two copper electrodes. The graphene nanoplatelets are obtained by the microwave irradiation of intercalated graphite, i.e., an environmentally friendly, fast and low-cost procedure. The contact is created by a bottom-up process, driven by the application of a DC electrical field in the gap between the electrodes, yielding the formation of a graphene carpet. The electrical resistance of the device has been measured as a function of the gap length and device temperature. The possible use of this device as a …

Electrophoretic Nanocrystalline Graphene Film Electrode for Lithium Ion Battery

2015

Graphene sheets were fabricated by electrophoretic deposition method from water suspension of graphene oxide followed by thermal reduction. The formation of nanocrystalline graphene sheets has been confirmed by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The electrochemical performance of graphene sheets as anode material for lithium ion batteries was evaluated by cycling voltammetry, galvanostatic charge-discharge cycling, and electrochemical impedance spectroscopy. Fabricated graphene sheets exhibited high discharge capacity of about 1120 mAhg−1 and demonstrated good reversibility of lithium intercalation and deintercalation in graphene sheet film with capacity…

Technical Program

2015

Synthesis of graphene oxide-intercalated α-hydroxides by metathesis and their decomposition to graphene/metal oxide composites

2010

Graphene oxide-intercalated alpha-metal hydroxides were prepared using layers from the delaminated colloidal dispersions of cetyltrimethylammonium-intercalated graphene oxide and dodecylsulfate-intercalated alpha-hydroxide of nickel/cobalt as precursors. The reaction of the two dispersions leads to de-intercalation of the interlayer ions from both the layered solids and the intercalation of the negatively charged graphene oxide sheets between the positively charged layers of the alpha-hydroxide. Thermal decomposition of the intercalated solids yields graphene/nanocrystalline metal oxide composites. Electron microscopy analysis of the composites indicates that the nanoparticles are intercala…

Nonlinear photo-oxidation of graphene and carbon nanotubes probed by four wave mixing imaging and spectroscopy (Presentation Recording)

2015

Graphene has high potential for becoming the next generation material for electronics, photonics and optoelectronics. However, spatially controlled modification of graphene is required for applications. Here, we report patterning and controlled tuning of electrical and optical properties of graphene by laser induced non-linear oxidation. We use four wave mixing (FWM) as a key method for imaging graphene and graphene oxide patterns with high sensitivity. FWM produces strong signal in monolayer graphene and the signal is highly sensitive to oxidation providing good contrast between patterned and non-patterned areas. We have also performed photo-oxidation and FWM imaging for air suspended carb…