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Crack damage detection for aluminum alloy materials using fiber Bragg Grating (FBG) sensor is a kind of structure health monitoring. In this paper, the damage index of full width at half maximum (FWHM) was extracted from the distorted reflection spectra caused by the crack-tip inhomogeneous strain field, so as to explain the crack propagation behaviors.

The FWHM variations were also investigated through combining the theoretical calculations with simulation and experimental analyses. The transfer matrix algorithm was developed to explore the mechanism by which FWHM changed with the linear and quadratic strain. Moreover, the crack-tip inhomogeneous strain field on the specimen surface was computed according to the digital image correlation measurement during the experiments.

The experimental results demonstrated that the saltation points in FWHM curve accorded with the moments of crack propagation to FBG sensors.

The interpretation of reflected spectrum deformation mechanism with crack propagation was analyzed based on both simulations and experiments, and then the performance of potential damage features – FWHM were proposed and evaluated. According to the correlation between the damage characteristic and the crack-tip location, the crack-tip of the specimen could be measured rapidly and accurately with this technique.

The purpose of this paper is to enhance the efficiency of the LED by introducing three-step magnesium (Mg) doping profile. Attention was paid to the effects of the Mg doping concentration of the first p-GaN layer (i.e. layer close to the active region). Attention was paid to the effects of the Mg doping concentration of the first p-GaN layer (i.e. layer close to the active region).

Indium gallium nitride (InGaN)–based light-emitting diode (LED) was grown on a 4-inch c-plane patterned sapphire substrate using metal organic chemical vapor deposition. The Cp₂Mg flow rates for the second and third p-GaN layers were set at 50 sccm and 325 sccm, respectively. For the first p-GaN layer, the Cp₂Mg flow rate varied from 150 sccm to 300 sccm to achieve different Mg dopant concentrations.

The full width at half maximum (FWHM) for the GaN (102) plane increases with increasing Cp₂Mg flow rate. FWHM for the sample with 150, 250 and 300 sccm Cp₂Mg flow rates was 233 arcsec, 236 arcsec and 245 arcsec, respectively. This result indicates that the edge and mixed dislocations in the p-GaN layer were increased with increasing Cp₂Mg flow rate. Atomic force microscopy (AFM) results reveal that the sample grown with 300 sccm exhibits the highest surface roughness, followed by 150 sccm and 250 sccm. The surface roughness of these samples is 2.40 nm, 2.12 nm and 2.08 nm, respectively. Simultaneously, the photoluminescence (PL) spectrum of the 250 sccm sample shows the highest band edge intensity over the yellow band ratio compared to that of other samples. The light output power measurements found that the sample with 250 sccm exhibits high output power because of sufficient hole injection toward the active region.

Through this study, the three steps of the Mg profile on the p-GaN layer were proposed to show high-efficiency InGaN-based LED. The optimal Mg concentration was studied on the first p-GaN layer (i.e. layer close to active region) to improve the LED performance by varying the Cp₂Mg flow rate. This finding was in line with the result of PL and AFM results when the samples with 250 sccm have the highest Mg acceptor and good surface quality of the p-GaN layer. It can be deduced that the first p-GaN layer doping has a significant effect on the crystalline quality, surface roughness and light emission properties of the LED epi structure.

The purpose of this paper is to report the structural properties of Al_xGa_1−xN (0≤x≤1) grown on sapphire substrate by means of X‐ray diffraction (XRD) technique. The main purpose of this work was to investigate the effects of Al(x) composition to the structural and microstructural properties of Al_xGa_1−xN ternary alloy such as the crystalline quality, crystalline structure and lattice constant c.

Al_xGa_1−xN thin films with wurtzite structure in the composition range of 0≤x≤1 are used in this study. The compositions of the samples are calculated using Vegard's law and verified by energy dispersive X‐ray analysis. The samples are then characterized by means of XRD rocking curve (RC) and phase analysis.

Investigation revealed that the full width half maximum (FWHM) of RC increase with the increase x value. This indicates that the crystalline quality of the samples deteriorate with the increase of Al compositions. The best fit of the non‐linear interpolation of the FWHM of the (002) diffraction RC data suggested that a maximum disorder should be expected in this mixed crystals system when the composition x≈45 percent.

This paper provides valuable information on the effect of Al compositions to the structural characteristics of Al_xGa_1−xN alloy system. The availability of information about maximum disorder of Al composition in Al_xGa_1−xN (0≤x≤1) alloy system provides useful reference in device fabrications where researchers are able to choose correct alloy composition in order to fabricate good quality devices.

This study aims to investigate the effect of temperature applied at the initial deposition of Aluminium Nitride (AlN) thin-film on a silicon substrate by high-power impulse magnetron sputtering (HiPIMS) technique.

HiPIMS system was used to deposit AlN thin film at a low output power of 200 W. The ramping temperature was introduced to substrate from room temperature to maximum 100°Cat the initial deposition of thin-film, and the result was compared to thin-film sputtered with no additional heat. For the heat assistance AlN deposition, the substrate was let to cool down to room temperature for the remaining deposition time. The thin-films were characterized by X-ray diffraction (XRD) and atomic force microscope (AFM) while the MIS Schottky diode characteristic investigated through current-voltage response by a two-point probe method.

The XRD pattern shows significant improvement of the strong peak of the c-axis (002) preferred orientation of the AlN thin-film. The peak was observed narrowed with temperature assisted where FWHM calculated at 0.35° compared to FWHM of AlN thin film deposited at room temperature at around 0.59°. The degree of crystallinity of bulk thin film was improved by 28% with temperature assisted. The AFM images show significant improvement as low surface roughness achieved at around 0.7 nm for temperature assisted sample compares to 3 nm with no heat applied.

The small amount of heat introduced to the substrate has significantly improved the growth of the c-axis AlN thin film, and this method is favorable in the deposition of the high-quality thin film at the low-temperature process.

Porous silicon (PS) was successfully fabricated using an alternating current photo-assisted electrochemical etching (ACPEC) technique. This study aims to compare the effect of different crystal orientation of Si n(100) and n(111) on the structural and optical characteristics of the PS.

PS was fabricated using ACPEC etching with a current density of J = 10 mA/cm² and etching time of 30 min. The PS samples denoted by PS₁₀₀ and PS₁₁₁ were etched using HF-based solution under the illumination of an incandescent white light.

FESEM images showed that the porous structure of PS₁₀₀ was a uniform circular shape with higher density and porosity than PS₁₁₁. In addition, the AFM indicated that the surface roughness of porous n(100) was less than porous n(111). Raman spectra of the PS samples showed a stronger peak with FWHM of 4.211 cm⁻¹ and redshift of 1.093 cm⁻¹. High resolution X-ray diffraction revealed cubic Si phases in the PS samples with tensile strain for porous n(100) and compressive strain for porous n(111). Photoluminescence observation of porous n(100) and porous n(111) displayed significant visible emissions at 651.97 nm (Eg = 190eV) and 640.89 nm (Eg = 1.93 eV) which was because of the nano-structure size of silicon through the quantum confinement effect. The size of Si nanostructures was approximately 8 nm from a quantized state effective mass theory.

The work presented crystal orientation dependence of Si n(100) and n(111) for the formation of uniform and denser PS using new ACPEC technique for potential visible optoelectronic application. The ACPEC technique has effectively formed good structural and optical characteristics of PS.

For additive manufacturing (AM) through laser-based powder bed fusion of polymers (PBF-LB/P), accurate characterization of powder flowability is vital for achieving high-quality parts. However, accurately characterizing feedstock flowability presents challenges because of a lack of consensus on which tests to perform and the diverse forces and mechanisms involved. This study aims to undertake a thorough investigation into the flowability of eight feedstock materials for PBF-LB/P at different temperatures using various techniques.

For ambient temperature assessments, established metrics such as avalanche angle and Hausner ratio, along with the approximated flow function coefficient (FFC_app), are used. The study then focuses on the influence of elevated temperatures representative of in-process conditions. FFC_app and differential scanning calorimetry (DSC) are performed and analyzed, followed by a correlation analysis as a holistic approach to identify key aspects for flowability. Furthermore, two feedstock materials are compared with a previous study to connect the present findings to PBF-LB/P processing.

The study revealed intrinsic material properties such as mechanical softening near the melting point to become significant. This partially explains why certain powders with poor ambient temperature flowability are consistently demonstrated to produce high-quality parts. FFC_app and thermal characterization through DSC are identified as critical metrics for optimizing feedstock material characteristics across temperature ranges.

Previous studies emphasized specific characterizations of feedstock material at ambient temperature, presented a limited materials selection or focused on metrics such as shape factors. In contrast, this study addresses a partially understood aspect by examining the critical role of temperature in governing feedstock material flowability. It advocates for the inclusion of temperature variables in flowability analyses to closely resemble the PBF-LB/P process, which can be applied to material design, selection and process optimization.

This paper aims to report the influence of sputtering plasma deposition time on the structural and mechanical properties of the a-axis oriented aluminium nitride (AlN) thin films.

The AlN films were prepared using RF magnetron sputtering plasma on a silicon substrate without any external heating with various deposition times. The films were characterized using X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), atomic force microscope (AFM) and nanoindentation techniques.

The XRD results show that the AlN thin films are highly oriented along the (100) AlN plane at various deposition times indicating the a-axis preferred orientation. All the AlN thin films exhibit hexagonal AlN with a wurtzite structure. The hardness and Young’s modulus of AlN thin films with various deposition times were measured using a nanoindenter. The measured hardness of the AlN films on Si was in the range of 14.1 to 14.7 GPa. The surface roughness and the grain size measured using the AFM revealed that both are dependent on the deposition times.

The novelty of this work lies with a comparison of hardness and Young’s modulus result obtained at different sputtering deposition temperature. This study also provides the relation of AlN thin films’ crystallinity with the hardness of the deposited films.

The aims of this paper is to study the effects of the V/III ratio of indium gallium nitride (InGaN) quantum wells (QWs) on the structural, optical and electrical properties of near-ultraviolet light-emitting diode (NUV-LED).

InGaN-based NUV-LED is successfully grown on the c-plane patterned sapphire substrate at atmospheric pressure using metal organic chemical vapor deposition.

The indium composition and thickness of InGaN QWs increased as the V/III ratio increased from 20871 to 11824, according to high-resolution X-ray diffraction. The V/III ratio was also found to have an important effect on the surface morphology of the InGaN QWs and thus the surface morphology of the subsequent layers. Apart from that, the electroluminescence measurement revealed that the V/III ratio had a major impact on the light output power (LOP) and the emission peak wavelength of the NUV-LED. The LOP increased by up to 53% at 100 mA, and the emission peak wavelength of the NUV-LED changed to a longer wavelength as the V/III ratio decreased from 20871 to 11824.

This study discovered a relation between the V/III ratio and the properties of QWs, which resulted in the LOP enhancement of the NUV-LED. High TMIn flow rates, which produced a low V/III ratio, contribute to the increased LOP of NUV-LED.

The purpose of this paper is to investigate the effect of high-k material HfO₂ as a buffer layer for the fabrication of metal-ferroelectric-insulator-silicon (MFeIS) structures on Si (100) substrate.

RF-sputtered Pb[Zr0.35Ti0.65]O₃ or (PZT) and plasma-enhanced atomic layer deposited HfO₂ films were selected as the ferroelectric and high-k buffer layer, respectively, for the fabrication of metal-ferroelectric-insulator-silicon (MFeIS) structures on Si (100) substrate. Multiple angle ellipsometry and X-ray diffraction analysis was carried out to obtain the crystal orientation, refractive index and absorption coefficient parameters of the deposited/annealed films. In the different range of annealing temperature, the refractive index was observed in the range of 2.9 to 2 and 1.86 to 2.64 for the PZT and HfO₂ films, respectively

Electrical and ferroelectric properties of the dielectric and ferroelectric films and their stacks were obtained by fabricating the metal/ferroelectric/silicon (MFeS), metal/ferroelectric/metal, metal/insulator/silicon and MFeIS capacitor structures. A closed hysteresis loop with remnant polarization of 4.6 µC/cm² and coercive voltage of 2.1 V was observed in the PZT film annealed at 5000 C. Introduction of HfO₂ buffer layer (10 nm) improves the memory window from 5.12 V in MFeS to 6.4 V in MFeIS structure with one order reduction in the leakage current density. The same MFeS device was found having excellent fatigue resistance property for greater than 1010 read/write cycles and data retention time more than 3 h.

The MFeIS structure has been fabricated with constant PZT thickness and varied buffer layer (HfO₂) thickness. Electrical characteristics shows the improved leakage current and memory window in the MFeIS structures as compared to the MFeS structures. Optimized MFeIS structure with 10-nm buffer layer shows the excellent ferroelectric properties with endurance greater than E10 read/write cycles and data retention time higher than 3 h. The above properties indicate the MFe(100 nm)I(10 nm)S gate stack as a potential candidate for the FeFET-based nonvolatile memory applications.

This paper aims to reports the further developments of an optical sensing technique, relying on Mie scattered and reflected light, from the ice surface and volume, to determine the ice accretion rate as well as the ice type.

By measuring the optical intensity of the backscattered and reflected light, the paper demonstrates that it is possible to obtain information on the onset of icing as well as determine the thickness and type of ice accreted on the leading edge of a wing in real time.

This work is important in the design and development of optical direct ice detection sensors for aerospace applications.

This work is aimed at showing a new approach to ice detection.

Original concept follow on paper from pervious publication.