42 research outputs found
High performance bilayer-graphene Terahertz detectors
We report bilayer-graphene field effect transistors operating as THz
broadband photodetectors based on plasma-waves excitation. By employing
wide-gate geometries or buried gate configurations, we achieve a responsivity
and a noise equivalent power in the 0.29-0.38 THz range, in photovoltage and photocurrent mode.
The potential of this technology for scalability to higher frequencies and the
development of flexible devices makes our approach competitive for a future
generation of THz detection systems.Comment: 8 pages, 5 figures. Submitted to Applied Physics Letter
Hysteresis-free high mobility graphene encapsulated in tungsten disulfide
High mobility is a crucial requirement for a large variety of electronic device applications. The state of the art for high-quality graphene devices is based on heterostructures made with graphene encapsulated in >40
nm-thick flakes of hexagonal boron nitride (hBN). Unfortunately, scaling up multilayer hBN while precisely controlling the number of layers remains an outstanding challenge, resulting in a rough material unable to enhance the mobility of graphene. This leads to the pursuit of alternative, scalable materials, which can be used as substrates and encapsulants for graphene. Tungsten disulfide (WS2) is a transition metal dichalcogenide, which was grown in large (∼mm-size) multi-layers by chemical vapor deposition. However, the resistance vs gate voltage characteristics when gating graphene through WS2 exhibit largely hysteretic shifts of the charge neutrality point on the order of Δn∼
3 × 1011 cm−2, hindering the use of WS2 as a reliable encapsulant. The hysteresis originates due to the charge traps from sulfur vacancies present in WS2. In this work, we report the use of WS2 as a substrate and overcome the hysteresis issues by chemically treating WS2 with a super-acid, which passivates these vacancies and strips the surface from contaminants. The hysteresis is significantly reduced by about two orders of magnitude, down to values as low as Δn∼
2 × 109 cm−2, while the room-temperature mobility of WS2-encapsulated graphene is as high as ∼62 × 103 cm2 V−1 s−1 at a carrier density of n ∼ 1 ×1012 cm−2. Our results promote WS2 as a valid alternative to hBN as an encapsulant for high-performance graphene devices
Relations between climatic–geomorphological parameters and sediment yield in a mediterranean semi-arid area (Sicily, southern Italy)
The Interest-Rate Sensitivity of the Demand for Sovereign Debt. Evidence from OECD Countries (1995-2011)
Search for High-energy Neutrinos from Binary Neutron Star Merger GW170817 with ANTARES, IceCube, and the Pierre Auger Observatory
The Advanced LIGO and Advanced Virgo observatories recently discovered
gravitational waves from a binary neutron star inspiral. A short gamma-ray
burst (GRB) that followed the merger of this binary was also recorded by the
Fermi Gamma-ray Burst Monitor (Fermi-GBM), and the Anticoincidence Shield for
the Spectrometer for the International Gamma-Ray Astrophysics Laboratory
(INTEGRAL), indicating particle acceleration by the source. The precise
location of the event was determined by optical detections of emission
following the merger. We searched for high-energy neutrinos from the merger in
the GeV--EeV energy range using the ANTARES, IceCube, and Pierre Auger
Observatories. No neutrinos directionally coincident with the source were
detected within s around the merger time. Additionally, no MeV
neutrino burst signal was detected coincident with the merger. We further
carried out an extended search in the direction of the source for high-energy
neutrinos within the 14-day period following the merger, but found no evidence
of emission. We used these results to probe dissipation mechanisms in
relativistic outflows driven by the binary neutron star merger. The
non-detection is consistent with model predictions of short GRBs observed at a
large off-axis angle.Comment: 22 pages, 2 figure