Fabrication of 2D based pn junctions with improved performance by selective laser annealing

There is a growing body of research on transistors based on nanomaterials such as 2D transition metal dichalcogenides (TMDs) (WS2, MoS2, etc.) and carbon nanotubes (CNTs). Here we co-deposited MoS2 and WS2 as PN junctions. The deposition could be performed on a PCB (printed circuit board) with Cu electrodes. The current-voltage characteristics were obtained using an Arduino board. The effect of laser irradiation could be investigated by studying the IV curves and light sensitivity for the same kind of devices in which one of the Cu electrodes was modified by a laser. The IV curves from the devices with and without laser treatment could be compared to quantify the changes in performance

In situ, broadband measurement of the radio frequency attenuation length at Summit Station, Greenland

Over the last 25 years, radiowave detection of neutrino-generated signals, using cold polar ice as the neutrino target, has emerged as perhaps the most promising technique for detection of extragalactic ultra-high energy neutrinos (corresponding to neutrino energies in excess of 0.01 Joules, or $10^{17}$ electron volts). During the summer of 2021 and in tandem with the initial deployment of the Radio Neutrino Observatory in Greenland (RNO-G), we conducted radioglaciological measurements at Summit Station, Greenland to refine our understanding of the ice target. We report the result of one such measurement, the radio-frequency electric field attenuation length $L_\alpha$. We find an approximately linear dependence of $L_\alpha$ on frequency with the best fit of the average field attenuation for the upper 1500 m of ice: $\langle L_\alpha \rangle = \big( (1154 \pm 121) - (0.81 \pm 0.14) (\nu/$MHz$)\big)$ m for frequencies $\nu \in [145 - 350]$ MHz.Comment: 13 pages, 8 figures, Accepted to Journal of Glaciolog

Precision measurement of the index of refraction of deep glacial ice at radio frequencies at Summit Station, Greenland

Glacial ice is used as a target material for the detection of ultra-high energy neutrinos, by measuring the radio signals that are emitted when those neutrinos interact in the ice. Thanks to the large attenuation length at radio frequencies, these signals can be detected over distances of several kilometers. One experiment taking advantage of this is the Radio Neutrino Observatory Greenland (RNO-G), currently under construction at Summit Station, near the apex of the Greenland ice sheet. These experiments require a thorough understanding of the dielectric properties of ice at radio frequencies. Towards this goal, calibration campaigns have been undertaken at Summit, during which we recorded radio reflections off internal layers in the ice sheet. Using data from the nearby GISP2 and GRIP ice cores, we show that these reflectors can be associated with features in the ice conductivity profiles; we use this connection to determine the index of refraction of the bulk ice as n=1.778 +/- 0.006

Search for dark matter annual modulation with DarkSide-50

Dark matter induced event rate in an Earth-based detector is predicted to show an annual modulation as a result of the Earth's orbital motion around the Sun. We searched for this modulation signature using the ionization signal of the DarkSide-50 liquid argon time projection chamber. No significant signature compatible with dark matter is observed in the electron recoil equivalent energy range above $40~{\rm eV_{ee}}$, the lowest threshold ever achieved in such a search.Comment: 8 pages, 4 figure

Search for dark matter-nucleon interactions via Migdal effect with DarkSide-50

Dark matter elastic scattering off nuclei can result in the excitation and ionization of the recoiling atom through the so-called Migdal effect. The energy deposition from the ionization electron adds to the energy deposited by the recoiling nuclear system and allows for the detection of interactions of sub-GeV/c$^2$ mass dark matter. We present new constraints for sub-GeV/c$^2$ dark matter using the dual-phase liquid argon time projection chamber of the DarkSide-50 experiment with an exposure of (12306 $\pm$ 184) kg d. The analysis is based on the ionization signal alone and significantly enhances the sensitivity of DarkSide-50, enabling sensitivity to dark matter with masses down to 40 MeV/c$^2$. Furthermore, it sets the most stringent upper limit on the spin independent dark matter nucleon cross section for masses below $3.6$ GeV/c$^2$.Comment: 7 pages, 3 figure

Search for dark matter particle interactions with electron final states with DarkSide-50

We present a search for dark matter particles with sub-GeV/$c^2$ masses whose interactions have final state electrons using the DarkSide-50 experiment's (12306 $\pm$ 184) kg d low-radioactivity liquid argon exposure. By analyzing the ionization signals, we exclude new parameter space for the dark matter-electron cross section $\bar{\sigma}_e$, the axioelectric coupling constant $g_{Ae}$, and the dark photon kinetic mixing parameter $\kappa$. We also set the first dark matter direct-detection constraints on the mixing angle $\left|U_{e4}\right|^2$ for keV sterile neutrinos.Comment: 6 pages, 2 figure

DarkSide-50 532-day dark matter search with low-radioactivity argon

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOThe DarkSide-50 direct-detection dark matter experiment is a dual-phase argon time projection chamber operating at Laboratori Nazionali del Gran Sasso. This paper reports on the blind analysis of a (16 660 +/- 270) kg d exposure using a target of low-radioactivity argon extracted from underground sources. We find no events in the dark matter selection box and set a 90% C. L. upper limit on the dark matter-nucleon spin-independent cross section of 1.14 x 10(-44) cm(2) (3.78 x 10(-44) cm(2), 3.43 x 10(-43) cm(2)) for a WIMP mass of 100 GeV/c(2) (1 TeV/c(2), 10 TeV/c(2)).9810117FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO2016/09084-0Agências de fomento estrangeiras apoiaram essa pesquisa, mais informações acesse artig