R. Danneau

Shot Noise in Ballistic Graphene

We have investigated shot noise in graphene field effect devices in the temperature range of 4.2-30 K at low frequency (f=600-850 MHz). We find that for our graphene samples with a large width over length ratio W/L, the Fano factor F reaches a maximum F ~ 1/3 at the Dirac point and that it decreases strongly with increasing charge density. For smaller W/L, the Fano factor at Dirac point is significantly lower. Our results are in good agreement with the theory describing that transport at the Dirac point in clean graphene arises from evanescent electronic states.

Evanescent Wave Transport and Shot Noise in Graphene: Ballistic Regime and Effect of Disorder

AbstractWe have investigated electrical transport and shot noise in graphene field effect devices. In large width over length ratio W/L graphene strips, we have measured shot noise at low frequency (f=600–850xa0MHz) in the temperature range of 4.2–30 K. We observe a minimum conductivity of n

Graphene microwave transistors on sapphire substrates

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High-quality Si 3 N 4 circuits as a platform for graphene-based nanophotonic devices

nand a finite and gate dependent Fano factor reaching the universal value of n

Highly sensitive and broadband carbon nanotube radio-frequency single-electron transistor

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Shot noise suppression and hopping conduction in graphene nanoribbons

nat the Dirac point, i.e. where the density of states vanishes. These findings are in good agreement with the theory describing that transport at the Dirac point should occur via evanescent waves in perfect graphene samples with large W/L. Moreover, we show and discuss how disorder and non-parallel leads affect both conductivity and shot noise.

Persistent hysteresis in graphene-mica van der Waals heterostructures

We have developed metal-oxide graphene field-effect transistors (MOGFETs) on sapphire substrates working at microwave frequencies. For monolayers, we obtain a transit frequency up to ∼80 GHz for a gate length of 200 nm and a maximum oscillation frequency of about ∼3 GHz for this specific sample. Given the strongly reduced charge noise for nanostructures on sapphire, the high stability and high performance of this material at low temperature, our MOGFETs on sapphire are well suited for a cryogenic broadband low-noise amplifier.

Graphene on boron nitride microwave transistors driven by graphene nanoribbon back-gates

Hybrid circuits combining traditional nanophotonic components with carbon-based materials are emerging as a promising platform for optoelectronic devices. We demonstrate such circuits by integrating single-layer graphene films with silicon nitride waveguides as a new architecture for broadband optical operation. Using high-quality microring resonators and Mach-Zehnder interferometers with extinction ratios beyond 40u202fdB we realize flexible circuits for phase-sensitive detection on chip. Hybrid graphene-photonic devices are fabricated via mechanical transfer and lithographic structuring, allowing for prolonged light-matter interactions. Our approach holds promise for studying optical processes in low-dimensional physical systems and for realizing electrically tunable photonic circuits.

rf-electrometer using a carbon nanotube resonant tunneling transistor

We have investigated radio-frequency single-electron transistor operation of single-walled carbon nanotube quantum dots in the strong tunneling regime. At a temperature of 4.2 K and with a carrier frequency of 754.2 MHz, we reach a charge sensitivity of 2.3×10−6e/Hz over a bandwidth of 85 MHz. Our results indicate a gain-bandwidth product of 3.7×1013u2002Hz(3/2)/e, which is by one order of magnitude better than those for typical radio-frequency single-electron transistors.

Tailoring supercurrent confinement in graphene bilayer weak links

We have investigated shot noise and conduction of graphene field-effect nanoribbon devices at low temperature. By analyzing the exponential I-V characteristics of our devices in the transport gap region, we found out that transport follows variable range hopping laws at intermediate bias voltages 1< Vbias <12 mV. In parallel, we observe a strong shot noise suppression leading to very low Fano factors. The strong suppression of shot noise is consistent with inelastic hopping, in crossover from one- to two-dimensional regime, indicating that the localization length lloc