pinecone/core-2020-05-10-deduplication huggingface dataset:
Fabrication of site‐controlled InGaN quantum dots using reactive‐ion etching

We adopted the simple top‐down etching to fabricate site‐ and dimension‐controlled InGaN quantum dots. Each quantum dot is disk shaped and embedded in a nanoscale pillar. Arrays of nanopillars with varying densities and nanopillar diameters were fabricated from an InGaN/GaN single quantum well using inductively‐coupled plasma reactive‐ion etching. Micro‐photoluminescence (µ‐PL) was used to characterize the emission properties of individual and ensemble of nanopillars. Strong and distinct PL signal of a single nanopillar was observed even at the room temperature. The emission was found to exhibit characteristics from a discrete energy state that is homogeneously broadened. The ensemble of nanopillars exhibited a similar emission linewidth as the single nanopillar, indicating a well controlled quantum dot dimensions and uniformity. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
Influence of radiation damage on diffusion of fission products in silicon carbide

The influence of irradiation induced damage on the transport of implanted species in poly and single crystalline
silicon carbide is investigated. For this purpose published diffusion results of strontium, silver, iodine
and cesium are compared with the associated evolution of defect profiles determined by α-particle channelling
in a backscattering geometry. Strong diffusion takes place in the amorphized surface layer of room
temperature implanted 6H-SiC during annealing at 1100 °C, which drops below the detection limit of 10-21
m2 s-1 as soon as re-crystallization is completed. Diffusion in samples implanted above the critical amorphization
temperature is only observed when simultaneously a significant reduction of defect density occurs.
No diffusion into the undamaged bulk is detected at temperatures up to 1500 °C. The observed diffusion behaviour
is explained by a defect related trapping and release mechanism. Normal grain boundary diffusion
of silver and iodine occurs in CVD-SiC.National Research Foundation and the Bundesministerium für Bildung und Forschunghttp://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1610-1642ahb201
Continuous wave OSL in bulk AlN single crystals

The kinetics of recombination luminescence of β-irradiated AlN single crystals has been studied with continuous wave optically stimulated luminescence (CW-OSL) method. It is shown that the OSL process is characterized by two exponential components with a decay time τ = 32 and 212 s. Photoionization cross-sections σ = 4.8·10-19 and 7.3·10-20 cm2 have been evaluated, assuming each component is related to electron traps based on VN- and/or ON-centers at various charged states. It is established that dose dependences of the OSL response of the bulk crystals under study are linear with taking into correct accounting for the radiation induced afterglow and hence can be used for quantitative estimates in solid state dosimetry. (© 2012 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim) Copyright © 2013 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim
Ridge waveguide InGaN/GaN quantum dot edge emitting visible lasers

Blue‐emitting and green‐emitting laser heterostructures were grown by molecular beam epitaxy, incorporating InGaN/GaN quantum dots as the active medium, with a measured quantum efficiency of 60% on n‐GaN bulk substrates. These quantum dots exhibit no S‐shape in the photoluminescence peak wavelength as a function of temperature, as typically found in comparable quantum well devices. The lasers were characterized by a threshold current density, J th , of 930 A/cm 2  under pulsed bias, with a differential efficiency of 13.9%, and a wall plug (power conversion) efficiency of 0.4% at 1050 A/cm 2 . Green‐emitting quantum dot lasers have J th  = 935 A/cm 2 . The lasers were also characterized by their modal properties through near field imaging (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
Carrier lifetimes in green emitting InGaN/GaN disks‐in‐nanowire and characteristics of green light emitting diodes

Improvement in the internal quantum efficiency (IQE) of InGaN/GaN disks‐in‐nanowires by surface passivation is demonstrated. The highest IQE achieved through surface passivation for green emitting (λ=540 nm) InGaN/GaN disks‐in‐nanowires is ∼53%. Radiative and nonradiative carrier lifetimes are calculated for as‐grown and surface passivated green emitting disks‐in‐nanowires. Passivated green sample exhibits a room temperature radiative lifetime of ∼748 ps, which is much smaller than that of equivalent quantum wells. Electroluminescence measurements on passivated green light emitting diodes containing InGaN disks demonstrate no roll over or efficiency droop up to 375 A/cm 2 , and exhibit a blue‐shift of 7 nm in peak wavelength. An enhancement in the light output due to surface passivation is observable in the relative external quantum efficiency of the surface passivated devices as compared with the as‐grown samples. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
Role of bias conditions in the hot carrier degradation of AlGaN/GaN high electron mobility transistors

The impacts of gate bias and device temperature on carrier energy distributions are reported for AlGaN/GaN High Electron Mobility Transistors. The lateral electric field and the average carrier energy are the highest at the end of gate on the gate‐drain access side. The number of high energy carriers is the greatest in the semi‐ON operating condition, with maximum energies exceeding the activation energy of defects in the AlGaN. There is a significant decrease in the number of very high energy carriers (greater than 2 eV) as the device temperature increases whereas the number of moderately energetic carriers (between 1 to 2 eV) is higher at elevated temperatures.(© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
Phonon modes and raman scattering in SixGe1-x nanocrystals: microscopic modelling

Si1-xGex nanocrystals (NCs) of different composition and size were generated using the Molecular Dynamics (MD)
method by minimizing NC’s total energy calculated using Tersoff’s empirical potential and applying rigid boundary conditions. The dynamical matrix of the relaxed NC was constructed and the NC phonon modes were calculated. The localisation of the principal (Si-Si, Si-Ge and Ge-Ge) modes is investigated by analysing their inverse participation ratio. The dependence of the corresponding Raman spectra, obtained by employing the bond polarisability model, upon x and the NC size is presented and compared to previous calculated results and available experimental data.Fundação para a Ciência e a Tecnologia (FCT
Nano- and micro-scale morghological defects in oxidized a-SiC: H thin films

Amorphous carbon rich a-SiC:H films were deposited on silicon substrates by RF-magnetron sputtering of SiC target in argon/methane gas mixture. The principal focus of this study was investigation of the effect of thermal oxidation on structure and morphology reconstruction in a-SiC:H amorphous network. The density of the films was varied over the range 1.6-2.2 g/cm2 by varying the magnetron discharge power. The local nano- and micro-scale surface morphology and chemical composition distribution were examined by atomic force microscopy, scanning electron microscopy equipped with Auger electron scanning system and optical profilometry. It was found that partial oxidation leads to local structure reconstruction accompanied by transformation of mechanical stresses from compressive to tensile. Formation of carbon-enriched nano- and micro-scale regions was observed after oxidation in low density samples. We attrribute these morphological defects to migration and precipitation of carbon species released in the process of oxidation of the SiC amorphous network. The mechanism of tensile stresses generation is also discussed.Science and Technology Center of Ukraine, project No. 5513, National Academy of Science project No. 2-2-15-28 and Arts et Métiers ParisTech (invited professor
Surface modification of field emission cathodes made of artificial carbon-based material

While the field emission acts at the technical vacuum level conditions (10-5 Pa) and electrons emitted from cathode, the ion bombardment exists and continuously modifies the cathode surface. Using X-ray photoelectron spectroscopy (XPS) we studied the electronic structure of thin surface layer of artificial carbon-based materials (ACB) used as field emission cathodes (FEC). The research resulted in the spectra of the samples B-1300, B-1500, B-1900. After spectra processing features analysis shows the change in type of hybridization of the original material. This change is supported by three characteristic spectral features: asymmetry of the core levels spectrum lines change, the satellite structure transformation, Auger-line and modification. So the initial material had sp2 type of hybridization, the spectra show that in thin surface layer a new phase with sp3-hybridization exists and we can conclude formation of nanoclusters with diamond-phase in thin surface layer of cathode. © 2013 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim
Irradiation of carbon nanotubes with carbon projectiles: A molecular dynamics study

The irradiation of carbon based nanostructures with ions and electrons has been shown to be an appropriate tool to tailor their properties. The defects induced in the nanostructures during irradiation are able to modify their mechanical and electronic properties. Here we simulate the irradiation of carbon nanotubes with carbon ions using a molecular dynamics code. We use the Tersoff potential joined smoothly to the Universal Ziegler-Biersack-Littmark potential at short distances. We study the number of defects produced after irradiation with a single carbon ion finding a saturation with its energy at ∼ 3 keV. We observe, after continuum irradiation with low energy ions, the formation of bumps in the irradiated region. For larger energy ions we find that the diameter of the nanotube shrinks as shown in previous works.This work has been financially supported by Project FIS2010-17225 by the Spanish Ministerio de Ciencia e Innovación
Electronic structure of graphene functionalized with boron and nitrogen

We present a theoretical study of the structural and electronic properties of
graphene monolayer functionalized with boron and nitrogen atoms substituting
carbon atoms. Our study is based on the ab initio calculations in the framework
of the density functional theory. We calculate the binding energies of the
functionalized systems, changes in the morphology caused by functionalization,
and further the band gap energy as a function of the concentration of dopants.
Moreover, we address the problem of possible clustering of dopants at a given
concentration. We define the clustering parameter to quantify the dependence of
the properties of the functionalized systems on the distribution of B/N atoms.
  We show that clustering of B/N atoms in graphene is energetically unfavorable
in comparison to the homogenous distribution of dopants. For most of the
structures, we observe a nonzero energy gap that is only slightly dependent on
the concentration of the substituent atoms.Comment: accepted in Physica Status Solid
Production of nanopowders of oxides by means of fiber and pulse-periodical CO2 lasers

The results of investigation of YSZ, Nd:Y2O3, Al2O3 nanopowder production by laser evaporation of oxide targets in a gas current are reported in present paper. For this purpose we used the pulse-periodical CO2 laser and the continuous fiber ytterbium laser with 550 W and 600 W radiation mean power accordingly. The powders obtained by these lasers, consisted of weakly agglomerated spherical nanopartices (≥ 99 wt%), and ≤ 1 wt% of micron sized particles (drops and target fragments). Nanoparticles from various oxides produced by CO2 laser in atmospheric pressure air had close average sizes (10ч16 nm). The productivity of nanopowder synthesis by CO2 laser from YSZ 1%Nd:Y2O3, 1%Nd:Y2O3, Al2O3, and CeGdO was 23 g/hour, 29 g/hour, 24 g/hour and 80 g/hour, respectively. Unlike CO2 laser the deep melting mode is realized during evaporation of 1%Nd:Y2O3 and Al2O3 targets by fiber laser. The crater depth increases up to 300-1000 μm in this mode. As a result, the target surface became very irregular and productivity of nanopowder synthesis was less, than in the case of CO2 laser. To reduce the effect of deep melting the evaporation of a target has been investigated experimentally and theoretically. As a result of our investigations we have obtained 1%Nd:Y2O3 nanopowder with specific surface of 70 m2/g and productivity of 23 g/hour at air pressure 70 kPa. © 2013 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim
The influence of HfO2 additives on the optical properties of Nd3+-doped Y2O3 ceramics

Transparent yttria ceramics were fabricated by sintering a mixture of 1 at.% Nd:Y2O3 and HfO2 nanopowders produced by laser synthesis method. The best transmittance was 80.96% at the wavelength of λ=1080 nm in 6 mol.% HfO2 doped sample (1.5 mm thick). The additives of hafnium broaden both pumping and luminescence bands of Nd3+ ion in yttria ceramics. The luminescence intensity of 4F3/2→4I11/2 transition was little affected by hafnium concentration. The effective lifetime of 4F3/2 level in Nd:Y2O3 ceramics enhanced by 30% at 10 mol.% HfO2 doping concentration and the decay kinetics of laser transition attains Förster's behavior. © 2013 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim
Effect of the experimental parameters on the shape and formation kinetics of SiNWs formed by electroless chemical etching in aqueous AgNO3/HF/H2O2 solution

The discovery at the beginning of 1990 of carbon nanotubes awaked the interest for one-dimensional (1D) nanostructures. Currently, silicon nanowires (SiNWs) formed by electroless chemical etching in aqueous Ag- NO3/HF/H2O2 solution, arouse great interest due to their physical properties and potential applications. The  
understanding of physical-chemical phenomena that occur during the formation of SiNWs, the effect of etching parameters on their morphology, the formation mechanism and formation kinetic raise many questions. In this paper,  we investigate the effect of etching parameters; namely AgNO3 concentration, HF concentration, etching time
and the volume of H2O2 on the shape of obtained nanostructures. The formation kinetic was investigated by studying the effect of the etching time on the morphology of obtained nanostructures. SiNWs studied in this work were formed on a P type and (100) oriented monocrystalline silicon substrate. Characterization of formed SiNWs was performed using a scanning electron microscope (SEM)
Electrical and optical properties of mixed phase tungsten trioxide films grown by laser pyrolysis

Laser pyrolysis is a synthesis method used to produce
thin films and nanomaterials of high quality and purity,
by intersecting a laser beam with a chemical precursor.
We have chosen laser pyrolysis to synthesize tungsten
trioxide starting with tungsten ethoxide precursor. The
film had a thickness that varied from 205 nm to 1 μm. Xray
diffraction and Raman spectroscopy confirmed the
presence of a mixture of hexagonal and tetragonal phase
WO3 in the synthesized film, and it was clear that annealing
greatly influenced the phases and types of structures
formed. I-V curves of the films showed n-type semiconducting behaviour, but the mixed phase appeared to cause
a similar behaviour of dopants in a semiconductor. The
refractive index decreased with increasing wavelength
and gave values of up to 21 at low wavelengths. The average
optical band gap was found to 3.6 eV from UV/Vis
spectroscopy. Scanning Electron Microscopy (SEM)
showed a mixture of nano- and microstructures and
shapes formed after annealing. One of the grown
nanostructures was nanorods, this isolated using FIB for
possible applications such as an active sensing medium
in gas sensors.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1610-1642ahb201
Logic functions based on optical bias controlled SIC Tandem devices

The purpose of this paper is the design of an optoelectronic circuit based on a-SiC technology, able to act simultaneously as a 4-bit binary encoder or a binary decoder in a 4-to-16 line configurations and show multiplexer-based logical functions. The device consists of a p-i'(a-SiC:H)-n/p-i(a-Si:H)-n multilayered structure produced by PECVD. To analyze it under information-modulated wave (color channels) and uniform irradiation (background) four monochromatic pulsed lights (input channels): red, green, blue and violet shine on the device. Steady state optical bias was superimposed separately from the front and the back sides, and the generated photocurrent was measured. 
Results show that the devices, under appropriate optical bias, act as reconfigurable active filters that allow optical switching and optoelectronic logic functions development providing the possibility for selective removal of useless wavelengths. The logic functions needed to construct any other complex logic functions are the NOT, and both or either an AND or an OR. Any other complex logic function that might be found can also be used as building blocks to achieve the functions needed for the retrieval of channels within the WDM communication link. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei
Comparison of the physical, chemical and electrical properties of ALD Al2O3 on c- and m-plane GaN

This study compares the physical, chemical and electrical properties of Al[subscript 2]O[subscript 3] thin films deposited on gallium polar c- and nonpolar m -plane GaN substrates by atomic layer deposition (ALD). Correlations were sought between the film's structure, composition, and electrical properties. The thickness of the Al[subscript 2]O[subscript 3] films was 19.2 nm as determined from a Si witness sample by spectroscopic ellipsometry. The gate dielectric was slightly aluminum-rich (Al:O=1:1.3) as measured from X-ray photoelectron spectroscopy (XPS) depth profile, and the oxide-semiconductor interface carbon concentration was lower on c -plane GaN. The oxide's surface morphology was similar on both substrates, but was smoothest on c -plane GaN as determined by atomic force microscopy (AFM). Circular capacitors (50-300 μm diameter) with Ni/Au (20/100 nm) metal contacts on top of the oxide were created by standard photolithography and e-beam evaporation methods to form metal-oxide-semiconductor capacitors (MOSCAPs). The alumina deposited on c -plane GaN showed less hysteresis (0.15 V) than on m -plane GaN (0.24 V) in capacitance-voltage (CV) characteristics, consistent with its better quality of this dielectric as evidenced by negligible carbon contamination and smooth oxide surface. These results demonstrate the promising potential of ALD Al[subscript 2]O[subscript 3] on c -plane GaN, but further optimization of ALD is required to realize the best properties of Al[subscript 2]O[subscript 3] on m -plane GaN
Iron deposition on multi-walled carbon nanotubes by fluidized bed MOCVD for aeronautic applications

The fluidized bed MOCVD process has been studied in order to uniformly deposit iron nanoparticles on the outer surface of multi‐walled carbon nanotubes (MWCNTs) tangled in balls of 388 µm in diameter. Using ferrocene as organometallic precursor at atmospheric pressure, various reactive atmospheres of deposition (under N2, air and H2) and an ozone O3 surface pre‐treatment of MWCNTs were tested. Around 10 g Fe/100 g MWNCTs were deposited during each run. Under N2 at 650 °C on the raw MWCNTs, nanoparticles formed of Fe and Fe3C were deposited which have catalyzed the formation of carbon nanofibers (CNFs). 20 h of ozone (O3) pre‐treatment improved the number and distribution of iron nanoparticles but without increasing the surface coverage of nanotubes. A more intense amorphous carbon deposit also appeared. Under H2 at 550 °C, the amorphous carbon was partly eliminated but fewer iron nanoparticles were present. Under air at 450 °C, a part of the MWCNTs was lost and a Fe2O3 shell covered each remaining MWCNTs ball. New works are in progress to increase more markedly the surface reactivity of MWCNTs and to deposit pure iron. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
Growth and characterization of CdTe absorbers on GaAs by MBE for high concentration PV solar cells

CdTe based II-VI absorbers are promising candidates for high concentration PV solar cells with an ideal band gap for AM1.5 solar radiation. In this study, we propose single crystal CdTe absorbers grown on GaAs substrates with a molecular beam epitaxy (MBE) which is a clean deposition technology. We show that high quality CdTe absorber layers can be grown with full width half maximum of X-ray diffraction rocking curves (XRD RC) as low as 227 arc-seconds with 0.5% thickness uniformity that a 2 μm layer is capable of absorbing 99% of AM1.5 solar radiation. Bandgap of the CdTe absorber is found as 1.483 eV from spetroscopic ellipsometry (SE) measurements. Also, high absorption coefficient is calculated from the results, which is ∼5 x 105cm-1 in solar radiation spectrum
Electromagnetic absorption of quasi-1D Majorana nanowires

We calculate the electromagnetic absorption cross section of long and narrow
nanowires, in the so-called quasi-1D limit. We consider only two transverse
bands and compute the dipole absorption cross section taking into account
quasiparticle transitions from negative to positive energy eigenstates of the
Bogoliubov-de Gennes Hamiltonian. The presence of the zero energy (Majorana)
state manifests in the different absorption spectra for $x$ (parallel) and $y$
(transverse) polarizations of the electromagnetic field.
  In the $y$-polarized case, the Majorana state causes a low energy absorption
plateau extending from mid-gap up to full-gap energy. Increasing further the
energy, the plateau is followed by a region of enhanced absorption due to
transitions across the full gap. For $x$ polarization the low energy absorption
plateau is not observed.Comment: Submitted to E-MRS Spring Meeting 2015 ( Only acknowledgement update
Constructive feedback for the growth of laser-induced periodic surface
  structures

We study the formation and growth of laser-induced periodic surface
structures (LIPSSs) with the finite-difference time-domain (FDTD) method. We
use a recently proposed inter-pulse feedback method to account for the
evolution of the surface morphology between each laser pulse sent to the
surface of the processed material. This method has been used with an
ablation-like mechanism, by removing material exposed to a light intensity
higher than a given threshold. We propose an inverse mechanism, an
expansion-like mechanism, able to grow structures that the ablation-like
process cannot. This allows us to introduce the notions of constructive and
destructive feedback and explains a strong contradiction between the standard
Sipe-Drude theory and the experimental observations, i. e. the formation on
metals of structures usually linked to wide band gap dielectrics.Comment: 4 pages, 4 figures, conference proceeding (Excon2015