Abstract
This work reports on the fabrication and characterization of an Au/ZnO/Pt-based high-overtone bulk acoustic resonator (HBAR) on SiC substrates. We evaluate its microwave characteristics ...comparing with Si substrates for micro-electromechanical applications. Dielectric magnetron sputtering and an electron beam evaporator are employed to develop highly
c
-axis-oriented ZnO films and metal electrodes. The crystal structure and surface morphology of post-growth layers are characterized using X-ray diffraction, atomic force microscopy, and scanning electron microscopy techniques. HBAR on SiC substrate results in multiple longitudinal bulk acoustic wave resonances up to 7 GHz, with the strongest excited resonances emerging at 5.25 GHz. The value of
f.Q
(Resonance frequency.Quality factor) parameter obtained using a novel
Q
approach method for HBAR on SiC substrate is 4.1
$$\times$$
×
10
$$^{13}$$
13
Hz, which to the best of our knowledge, is the highest among all reported values for specified ZnO-based devices.
The first and foremost task of a phishing-detection mechanism is to confirm the appearance of a suspicious page that is similar to a genuine site. Once this is found, a suitable URL analysis ...mechanism may lead to conclusions about the genuineness of the suspicious page. To confirm appearance similarity, most of the approaches inspect the image elements of the genuine site, such as the logo, theme, font color and style. In this paper, we propose a novel logo-based phishing-detection mechanism that characterizes the existence and unique distribution of hue values in a logo image as the foundation to unambiguously represent a brand logo. Using the proposed novel feature, the detection mechanism optimally classifies a suspicious logo to the best matching brand logo. The experiment is performed over our customized dataset based on the popular phishing brands in the South-Asia region. A set of five machine-learning algorithms is used to train and test the prepared dataset. We inferred from the experimental results that the ensemble random forest algorithm achieved the high accuracy of 87% with our prepared dataset.
This article reports the detailed X-ray absorption spectroscopy (XAS) study of Al
1−
x
Cr
x
N (
x
= 4, 6, 11%) thin films synthesized by the reactive magnetron co-sputtering technique. All these ...films were crystallized with a hexagonal wurtzite structure with preferential orientation along the
a
-axis without the formation of any secondary phases. Surface chemical analysis to evaluate the Cr concentration was carried out using X-ray photoelectron spectroscopy. The study confirmed the presence of AlN and Cr in bonding with N. The local crystal structure around the Cr dopant in the as-synthesized and annealed thin films has been analyzed by both the X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) techniques. From XAS, it was found that Cr replaced the Al atom in the AlN lattice and led to a localized CrN species with distorted tetrahedral AlN in the absence of Cr clustering. The bond lengths of (Cr-N)
ax
, (Cr-N)
bs
and Cr-Al, extracted from the EXAFS fitting, were found to decrease with the Cr concentration for both the as-synthesized and annealed thin films due to the enhancement of p-d hybridization between the dopant and the host atoms. However, in the annealed 11% Cr film, the bond lengths are larger than the other and tend to match the Cr-N geometry in CrN.
This article reports the detailed X-ray absorption spectroscopy (XAS) study of Al
1−
x
Cr
x
N (
x
= 4, 6, 11%) thin films synthesized by the reactive magnetron co-sputtering technique.
We report the mechanical properties of Cr-doped AlN thin films synthesized by reactive magnetron co-sputtering technique with different Cr concentrations (0, 2, 4, 6 and 11 at%). Surface chemical ...analysis and crystal structure studies of Cr doped AlN films are carried out using X-ray photoelectron spectroscopy (XPS) and grazing incidence X-ray diffraction (GIXRD) techniques. All these films are crystallized with wurtzite structure and grown predominantly along a-axis orientation in the absence of secondary phases belonging to Cr. The surface morphology and RMS roughness are measured by atomic force microscope (AFM). The residual stress of these films exhibit a tensile behavior and it decreases with Cr concentration as calculated by sin2ψ technique. Indentation hardness of these films is measured by nanoindentation technique, which is ranged from 17.5 to 23.0 GPa. However, indentation modulus is enhanced with Cr concentration due to strong p-d hybridization between Cr and N atoms. Indentation impression of these films exhibit a sink-in behavior and gives an evidence of high elastic recovery without radial cracks.
We report on the influence of Al doping on the structural, morphological and vibrational properties of hematite crystallite synthesized by using the hydrothermal method. The structural property of ...the pristine and Al doped hematite samples are extensively characterized by the Rietveld profile refinement of X-ray diffraction data. The structural refinement suggests that both the pristine and the doped compounds are stabilized in the hexagonal R3̄c symmetry. Doping with Al induces a compressive strain in the hematite lattice, which is further reflected in the spectroscopic Raman studies. It is also observed that the Al atom has a significant influence on the growth mechanism of hematite crystallites. Temperature dependent Raman study performed in the Al doped hematite sample brings out anomalous behaviour of phonon modes and line widths around the temperature region of 150 K. These anomalies observed around the temperature region of 150 K are suggestive of the presence of spin-phonon coupling associated with the Morin transition in the Al doped hematite. Our detailed structural and Raman spectroscopic analyses suggest that the Al doped hematite can be a potential magnetodielectric candidate.
This paper reports the temperature effects on the optical properties of metalorganic vapour-phase epitaxy (MOCVD) grown c-axis oriented AlN epilayer thin film studied by in-situ high-temperature ...spectroscopic ellipsometry. The crystal structure and the quality of the grown AlN epilayer film are analyzed using X-ray Diffraction and rocking curve techniques, respectively. Modelling of the ellipsometric data revealed that the uniaxial anisotropic refractive indices of the c-axis oriented film in the directions n‖ and n⊥ increased from 2.50 to 2.59 and 2.32 to 2.37, respectively with the increase in temperature from 223 to 573 K. The thermo-optic coefficients were evaluated to be around 10−5. Nano-mechanical characterization of this film showed an average hardness of 19.4 GPa at ambient temperature, which is higher than a-axis oriented AlN film. The average surface free energy of the synthesized film as evaluated from contact angle measurements is reported to be around 36.22 ± 0.64 mN/m. These results are highly relevant for a better understanding of c-axis oriented AlN-based materials in high-temperature ultraviolet optical devices.
•Spectroscopic Ellipsometry technique is used to investigate the temperature-dependent uniaxial anisotropic optical constants of c-axis AlN film.•Refractive indices along parallel and perpendicular to the c-axis of AlN increase from 2.50 to 2.59 and 2.32 to 2.37, respectively with an increase in temperature from 223 to 573 K.•Nano-mechanical characterization of the c-axis AlN film shows high hardness than that of the a-axis oriented AlN film.•The surface free energy of the film as evaluated from contact angle measurements is around 36.22 ± 0.64 mN/m.
Spectroscopic Ellipsometer is employed to study the optical properties (including complex refractive index and bandgap) of pristine and doped AlN (Ti and Cr) films as a function of doping ...concentration and temperature (273 K–573 K). Pristine AlN, Al1−xTixN (x = 1.5, 3 and 4 at%) and Al1−xCrxN (x = 2, 4 and 6 at%) films are grown on Si(100) substrates using magnetron sputtering technique. The crystal structure and chemical composition of the as grown films are analyzed using Grazing Incidence X-ray Diffraction (GIXRD) and X-ray Photoelectron Spectroscopy (XPS) techniques, respectively. The optical properties of Ti, Cr doped AlN films at a wider range of energies as well as different ambient temperatures are reported. To determine the complex refractive indices, the measured ellipsometric parameters Is and Ic are fitted using a five layer model with Lorentz oscillator dispersion relation. As far as the bandgap region is concerned, both the real and imaginary parts of the refractive index show significant changes near the bandgap. It is observed that, the real part of refractive index of AlN increases monotonically with the increase in Ti doping and opposite in Cr doping. The extinction coefficient is relatively larger for Cr-doped AlN compared to Ti-doped AlN films. With the increase in doping concentration, the bandgap is found to decrease rapidly for Cr-doped AlN in comparison to Ti-doped AlN films. Additionally, a significant change in the complex refractive index of doped AlN films is observed with temperature.
Display omitted
•Spectroscopic Ellipsometry (SE) technique is used to investigate the optical constants of Ti and Cr doped AlN films.•The refractive index (n) of doped-AlN increases monotonically with the increase in Ti doping and decreases for Cr doping.•A significant increase in the extinction coefficient (k) of doped AlN films is observed with the increase in temperature.•With the increase in doping concentration, the bandgap decreases rapidly for Cr-doped AlN films, unlike Ti-doped AlN.
In this article, we predominantly report the investigation of the local crystal structure around a Ti dopant by X-ray absorption spectroscopy (XAS) and the nano-mechanical properties of co-sputtered ...Al
1−
x
Ti
x
N (
x
= 0 to 4%) thin films. Grazing incidence X-ray diffraction (GIXRD) results show that these films are crystallized with the hexagonal wurtzite structure of AlN. Surface chemical analysis and morphology analysis of Al
1−
x
Ti
x
N films are executed using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques, respectively. X-ray absorption near-edge structure (XANES) shows that a Ti atom replaces Al in the AlN crystal and forms localized distorted tetrahedral TiN species, leading to a tensile strain. The bond lengths (Ti-N)
ax
and (Ti-N)
bs
are found to be moderately decreased with increasing Ti concentration, which is extracted from the extended X-ray absorption fine structure (EXAFS) analysis. However, the Ti-Al bond length in the second coordination sphere having Al vacancies is unaffected by Ti concentration. The hardness (
H
) and modulus (
E
) of Al
1−
x
Ti
x
N films are measured by the nano-indentation technique, and increase from 17.5 to 27.6 GPa and 231 to 293 GPa, respectively with
x
= 0 to 4 at% because of the improvement of p-d hybridization between the Ti and N atoms.
In this article, we predominantly report the investigation of the local crystal structure around a Ti dopant by X-ray absorption spectroscopy (XAS) and the nano-mechanical properties of co-sputtered Al
1−
x
Ti
x
N (
x
= 0 to 4%) thin films.
In the present work, gadolinium zirconate (Gd2Zr2O7) coatings have been developed on Inconel-718 substrates by electron beam physical vapor deposition (EB-PVD) technique. The structural, ...morphological and mechanical properties as a function of substrate temperature have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), nanoindentation and scratch tests. XRD analysis revealed that the coatings showed cubic defect fluorite phase, and no secondary phase formation was observed in the coatings during deposition. The decrease in the lattice constant of the fluorite phase with increasing deposition temperature was explained on the basis of strain relaxation and vacancy concentration. Increased surface roughness of the coatings has been found with increasing substrate temperature as a result of increased crystallite size. An improved coating adhesion achieved for the coating deposited at higher substrate temperature of 973 K was confirmed by scratch test. Nanoindentation measurements indicated higher hardness (7.7 GPa) and resistance to plastic deformation and better capability to accommodate deformation energy for the coatings prepared at higher deposition temperature.
