Novel technological possibilities for growth of GaAs autoepitaxial films, and properties of Gunn diodes made on their basis

The n⁺-n-n⁺-n⁺⁺-GaAs epitaxial structures were MBE-grown on porous nanostructured and traditional (standard) heavily doped n⁺⁺-GaAs substrates. On their basis, we fabricated the Gunn diodes generating power output in the 44−59 GHz (first harmonic) and 101−104 GHz (second harmonic) frequency ranges. For both harmonics, the power output of the Gunn diodes grown on porous substrates was shown to be from 20 to 30 % higher than those grown on the flat ones

Porous nanostructured InP: technology, properties, application

We prepared porous InP (100) substrates with a nanostructured surface relief on which InP epitaxial films were grown. The structure, morphological, and photoluminescence properties of nanostructured substrates and InP epilayers grown on them were studied. These InP epilayers grown on the porous and standard InP substrates were used to make microwave diodes. We showed the advantages of the diodes made on the porous substrates (over those made on the standard ones) caused by higher structural perfection of the InP epilayers grown on the porous substrates

From graphene oxide towards aminated graphene facile synthesis, its structure and electronic properties

In this paper we present a facile method for the synthesis of aminated graphene derivative through simultaneous reduction and amination of graphene oxide via two-step liquid phase treatment with hydrobromic acid and ammonia solution in mild conditions. The amination degree of the obtained aminated reduced graphene oxide is of about 4 at.%, whereas C/O ratio is up to 8.8 as determined by means of X-ray photoelectron spectroscopy. The chemical reactivity of the introduced amine groups is further verified by successful test covalent bonding of the obtained aminated graphene with 3-Chlorobenzoyl chloride. The morphological features and electronic properties, namely conductivity, valence band structure and work function are studied as well, illustrating the influence of amine groups on graphene structure and physical properties. Particularly, the increase of the electrical conductivity, reduction of the work function value and tendency to form wrinkled and corrugated graphene layers are observed in the aminated graphene derivative compared to the pristine reduced graphene oxide. As obtained aminated graphene could be used for photovoltaic, biosensing and catalysis application as well as a starting material for further chemical modifications

Measurement of the muon flux from 400 GeV/c protons interacting in a thick molybdenum/tungsten target

The SHiP experiment is proposed to search for very weakly interacting particles beyond the Standard Model which are produced in a 400 GeV/c proton beam dump at the CERN SPS. About 1011 muons per spill will be produced in the dump. To design the experiment such that the muon-induced background is minimized, a precise knowledge of the muon spectrum is required. To validate the muon flux generated by our Pythia and GEANT4 based Monte Carlo simulation (FairShip), we have measured the muon flux emanating from a SHiP-like target at the SPS. This target, consisting of 13 interaction lengths of slabs of molybdenum and tungsten, followed by a 2.4 m iron hadron absorber was placed in the H4 400 GeV/c proton beam line. To identify muons and to measure the momentum spectrum, a spectrometer instrumented with drift tubes and a muon tagger were used. During a 3-week period a dataset for analysis corresponding to (3.27±0.07) × 1011 protons on target was recorded. This amounts to approximatively 1% of a SHiP spill

Track reconstruction and matching between emulsion and silicon pixel detectors for the SHiP-charm experiment

In July 2018 an optimization run for the proposed charm cross section measurement for SHiP was performed at the CERN SPS. A heavy, moving target instrumented with nuclear emulsion films followed by a silicon pixel tracker was installed in front of the Goliath magnet at the H4 proton beam-line. Behind the magnet, scintillating-fibre, drift-tube and RPC detectors were placed. The purpose of this run was to validate the measurement's feasibility, to develop the required analysis tools and fine-tune the detector layout. In this paper, we present the track reconstruction in the pixel tracker and the track matching with the moving emulsion detector. The pixel detector performed as expected and it is shown that, after proper alignment, a vertex matching rate of 87% is achieved

Wet chemical nitridation of GaAs(001) surface

Auger Electron Spectroscopy and Scanning Tunnelling Microscopy were used to study the chemical and structural properties of the GaAs(001) surface after wet chemical nitridation by hydrazine-sulfide solutions. AES results show that the as-nitrided surface is covered by a thin film formed by a layer of nitrogen atoms strongly bonded with the substrate, and by a layer of residual impurities above it. The residual layer consists of oxygen- and sulfur-containing compounds, which are removed by annealing at near 450 and 520$^{\circ}$C respectively. The STM relief of the annealed surface is smooth with the rms roughness of the order of 0.4 nm. It is formed by numerous grain-like features of average lateral size near 5 nm and of 0.5 nm of height. Possible origin of the features is discussed

Influence of the molecular structure of copper phtalocyanines on their ordering in thin films and, photoluminescence and absorption spectra

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