A pilot study for the thickness measurement of HfO2 films was performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The aim of this ...pilot study was to ensure the equivalency in the measurement capability of national metrology institutes for the thickness measurement of HfO2 films. In this pilot study, the thicknesses of six HfO2 films with nominal thickness from 1 nm to 4 nm were measured by X-ray Photoelectron Spectroscopy (XPS), X-ray Reflectometry(XRR), X-ray Fluorescence Analysis (XRF), Transmission Electron Spectroscopy (TEM), Spectroscopic Ellipsometry (SE) and Rutherford Backscattering Spectrometry (RBS). The reference thicknesses were determined by mutual calibration of a zero-offset method (Medium Energy Ion Scattering Spectroscopy (MEIS) of KRISS) and a method traceable to the length unit (the average thicknesses of three XRR data except the thinnest film). These reference thicknesses are traceable to the length unit because they are based on the traceability of XRR. For the thickness measurement by XPS, the effective attenuation length of Hf 4f electrons was determined. In the cases of XRR and TEM, the offset values were determined from a linear fitting between the reference thicknesses and the individual data by XRR and TEM. The amount of substance of HfO2, expressed as thickness of HfO2 films (in both linear and areal density units), was found to be a good subject for a CCQM key comparison.To reach the main text of this paper, click on Final Report. The final report has been peer-reviewed and approved for publication by the CCQM.
Gallium nitride (GaN) nanoparticles are synthesized by the gallium particle trapping effect in a N2 nonthermal plasma with metallic Ga vapor. A proposed method has an advantage of synthesized GaN ...nanoparticle purity because the gallium vapor from the inductively heated tungsten boat does not contain any impurity source. The synthesized particle size can be controlled by the amount of Ga vapor, which is adjusted using the plasma emission ratio of nitrogen to gallium, owing to the particle trapping effect. The synthesized nanoparticles are investigated by electron microscopy studies. High-resolution transmission electron microscopy (HRTEM) studies confirm that the synthesized GaN nanoparticles (10–40 nm) crystallize in a single-phase wurtzite structure. Room-temperature photoluminescence (PL) measurements indicate the band-edge emission of GaN at around 378 nm without yellow emission, which implies that the synthesized GaN nanoparticles have high crystallinity.
•We synthesize the gallium nitride(GaN) nanoparticle with nitrogen nonthermal plsma and metallic gallium(Ga) vapor using Ga particle trapping method.•Metallic Ga vapor could be controlled using temperature of Ga heating boat and Ga emission from the plasma.•GaN nanoparticle are formed on Ga particle surface during particle trapping in dark sheath.•According to electron microscopy studies, the synthesized nanoparticles are crystallized as single-phase wurtzite structure.
Single crystalline wurzite GaN nanowires were successfully synthesized on the NiO catalyzed alumina substrate through a simple thermal chemical vapor deposition method. The mixture of Ga and GaN ...powder was used as the source material of Ga for synthesizing GaN nanowires. The diameter of nanowires ranged 50–60 nm and the length was about hundreds of micrometers. The nanowires were single crystal with hexagonal wurzite structure. The peaks of Raman spectra of GaN nanowires appeared broadened and asymmetric compared with those of bulk GaN. PL spectra under excitation at 325 nm showed a strong emission at 3.315 eV from near band-edge transition and a broad weak emission at 2.695 eV related to deep level defects.
Bat-like InN nanostructures were successfully grown on GaN/AlN/Si(1
1
1) substrates using molecular beam epitaxy method. The initial growth behavior and structural properties of InN nanobats were ...studied from a nanostructural point of view. During the initial stage of the growth, a nucleation process and a shape-decision process took place in which 3-dimensional (3-D) GaN nanoislands and nanorods were formed on AlN initiation layer/Si substrate. This was followed by the independent growth of 3-D InN nanoislands and nanorods. Lateral expansion of the InN nanobats was observed, and the diameter of InN bats then reached a fixed value.
Context.
The occurrence rate of long-period (
a
≳ 50 au) giant planets around young stars is highly uncertain since it is not only governed by the protoplanetary disc structure and planet formation ...process, but also reflects both dynamical re-structuring processes after planet formation as well as possible capture of planets not formed in situ. Direct imaging is currently the only feasible method to detect such wide-orbit planets and constrain their occurrence rate.
Aims.
We aim to detect and characterise wide-orbit giant planets during and shortly after their formation phase within protoplanetary and debris discs around nearby young stars.
Methods.
We carry out a large
L
′-band high-contrast direct imaging survey for giant planets around 200 young stars with protoplanetary or debris discs using the NACO instrument at the ESO Very Large Telescope on Cerro Paranal in Chile. We use very deep angular differential imaging observations with typically >60° field rotation, and employ a vector vortex coronagraph where feasible to achieve the best possible point source sensitivity down to an inner working angle of about 100 mas. This paper introduces the NACO Imaging Survey for Planets around Young stars (NACO-ISPY), its goals and strategy, the target list, and data reduction scheme, and presents preliminary results from the first 2.5 survey years.
Results.
We achieve a mean 5
σ
contrast of Δ
L
′ = 6.4 ± 0.1 mag at 150 mas and a background limit of
L
′
bg
= 16.5±0.2 mag at >1.′′5. Our detection probability is >50% for companions with ≳8
M
Jup
at semi-major axes of 80–200 au and >13
M
Jup
at 30–250 au. It thus compares well to the detection space of other state-of-the-art high-contrast imaging surveys. We have already contributed to the characterisation of two new planets originally discovered by VLT/SPHERE, but we have not yet independently discovered new planets around any of our target stars. We have discovered two new close-in low-mass stellar companions around R CrA and HD 193571 and report in this paper the discovery of close co-moving low-mass stellar companions around HD 72660 and HD 92536. Furthermore, we report
L
′-band scattered light images of the discs around eleven stars, six of which have never been imaged at
L
′-band before.
Conclusions.
The first 2.5 yr of the NACO-ISPY survey have already demonstrated that VLT/NACO combined with our survey strategy can achieve the anticipated sensitivity to detect giant planets and reveal new close stellar companions around our target stars.
The effect of the Ni content (2-18 at.% Ni) in Al thin films on their resistivity, hillock formation and Al3Ni compound formation was investigated. The as-deposited Al-Ni-alloy films showed high ...elastic strains which increased with increasing Ni content. In addition, the annealing of the supersaturated Al-Ni-alloy thin films yielded two phases: Al3Ni and Al with strong (2 2 0) and (1 1 1) textures, respectively, suggesting that the nucleation of (2 2 0) Al3Ni is closely associated with (1 1 1) Al. The resistivity of the as-annealed Al-Ni-alloy films varied as functions of the volume fraction and grain size of the two phases, which were determined by the Ni content and annealing temperature, respectively. The hillock formation was effectively suppressed when a small amount of Ni was added to the Al alloy. The results showed that a Ni content of less than approximately 4.5 at.% produced hillock-free Al-alloy thin films with a low resistivity of less than 6.0 µΩ cm upon annealing at 350 °C.
The A-type metallic-line (Am) stars are typically considered to be non-magnetic or possessing very weak sub-G magnetic fields. This view has been repeatedly challenged in the literature, most ...commonly for the bright hot Am star o Peg. Several studies claimed to detect 1-2 kG field of unknown topology in this object, possibly indicating a new process of magnetic field generation in intermediate-mass stars. In this study, we revisit the evidence of a strong magnetic field in o Peg using new high-resolution spectropolarimetric observations and advanced spectral fitting techniques. The mean magnetic field strength in o Peg is estimated from the high-precision CRIRES+ measurement of near-infrared sulphur lines. This observation is modelled with a polarised radiative transfer code, including treatment of the departures from local thermodynamic equilibrium. In addition, the least-squares deconvolution multi-line technique is employed to derive longitudinal field measurements from archival optical spectropolarimetric observations of this star. Our analysis of the near-infrared S I lines reveals no evidence of Zeeman broadening, ruling out magnetic field with a strength exceeding 260 G. This null result is compatible with the relative intensification of Fe II lines in the optical spectrum taking into account blending and uncertain atomic parameters of the relevant diagnostic transitions. Longitudinal field measurements at three different nights also yield null results with a precision of 2 G. This study refutes the claims of kG-strength dipolar or tangled magnetic field in o Peg. This star is effectively non-magnetic, with the surface magnetic field characteristics no different from those of other Am stars.
Well-aligned single-crystalline zinc oxide (ZnO) nanowires with high density were successfully synthesized on nickel monoxide (NiO) catalyzed alumina substrate through a simple metal–vapor deposition ...method at an extremely low temperature (450 °C). The single-crystalline ZnO nanowires had a hexagonal wurzite structure and diameters of about 55 nm, and lengths up to 2.6 μm. The photoluminescence spectra under excitation 325 nm showed a ultra-violet (UV) emission at 3.26 eV and a green emission at 2.44 eV. The UV emission and green emission bands were attributed to near band-edge transition and radial combination of a singly ionized oxygen vacancy with a photo-induced hole, respectively.
Well-aligned single-crystalline wurzite zinc oxide (ZnO) nanowire array was successfully fabricated on an Al2O3 substrate by a simple physical vapor-deposition method at a low temperature of 450 °C. ...The diameter and growth rate of ZnO nanowires increased as a function of growth temperature. TEM observation showed that the ZnO nanowires were synthesized along the c-axial direction of the hexagonal crystal structure. We demonstrate that ZnO nanowires followed the self-catalyzed growth mechanism on the ZnO nuclei. Besides high-quality ZnO nanowires, sometimes a fascinating hierarchically ordered ZnO structure was also observed.
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