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Highlights: [•] Gold nanoparticles (NPs) were spin-coated on linker-free Si substrates. [•] Density of NPs on n-Si was significantly higher than that of p-Si substrate. [•] Protonation of –OH created a net positive charge on Si thus, immobilized NPs. [•] Density of NPs on Si substrate was manipulated by the number of depositions. [•] Embedded NPs in Al Schottky contact raised current density of diodes. [ABSTRACT FROM AUTHOR] more...

Abstract: The aim of this research work is to present a reliability analysis on the suitability of the Ag80–Al20 sintered die attach nanopaste for high temperature applications on SiC power devices. Die back metallization studies pointed out that Ag and Au would be suitable candidates to form a strong bond between the SiC die and Ag80–Al20 die attach for high temperature operations. The post-sintered Ag80–Al20 die attach revealed a low modulus of elasticity at 9.8GPa due to the formation of micro-pores during sintering. This also influenced the hardness and stiffness as well at 0.49GPa and 30354.14N/m, respectively. The electrical conductivity of the Ag80–Al20 die attach material decreased slightly with increasing thermal aging repetitions. As the die attach material aged, it seemed to undergo a reduction in electrical performance, though as shown earlier the structure was still intact. This decomposition was suggested to occur due to the organic–metallic system’s composition itself, and the volatility of the residue organics. [Copyright &y& Elsevier] more...

This study was a novel approach using biosynthesis of CeO 2 nanostructures from the extract of Pandanus amaryllifolius leaves as a stabilizing agent. Two types of CeO 2 nanostructures (with and without Monoethanolamine (MEA)) were prepared using the same precursors to determine the bio-reducing and stabilizing effects of MEA on the crystal growth of CeO 2 nanostructures. Both CeO 2 samples were subjected to calcination temperatures of 500 and 800 °C. Crystal structure, morphology, optical properties, and structural defects of the samples were characterized with high resolution X-ray diffraction (HRXRD), field emission scanning electron microscopy (FESEM), UV–visible spectrophotometry, and Raman spectra, respectively. The biosynthesized CeO 2 nanostructures were spherically shaped, and aggregated to form agglomerations of CeO 2 nanostructures as the calcination temperature was increased from 500 to 800 °C. The nanospherical CeO 2 nanostructures covered the Si substrate densely when MEA was added. HRXRD measurement displayed peaks corresponding to the cubic structure CeO 2. The peak intensity and distinctiveness was increased with the addition of MEA as well as with the increase in calcination temperature from 500 to 800 °C. More details were discussed in the work. • Biosynthesis of CeO 2 nanostructures using Pandanus amaryllifolius leaves. • CeO 2 nanostructures were deposited on silicon via spin coating technique. • Addition of monoethanolamine (MEA) for crystal growth of CeO 2 nanostructures. • Effects of calcination temperature onto CeO 2 nanostructures were studied. • Potential application in the production of metal-oxide-semiconductor (MOS) devices. [ABSTRACT FROM AUTHOR] more...

In this study, effect of post-fabrication annealing (PFA) on the electrical performance of the InAlN/GaN high electron mobility transistors (HEMTs) has been investigated. With PFA, the gate Schottky barrier height increases by 94 % (from 1.03 eV to 2.00 eV) and the interface trap state density (D it) is reduced by 27 %. Compared with the device without PFA, a higher on-current (11 %), a larger on/off current ratio (∼1 order), a higher transconductance (3 %), a reduced gate leakage current (84 %) and a lower subthreshold swing (10 %) are recorded in device with PFA. In addition, the improved electron mobility is observed and the reduction of polarization Coulomb field (PCF) scattering is proven in device with PFA due to the enhancement of polarization electrical field in InAlN/GaN heterostructure. [ABSTRACT FROM AUTHOR] more...

Poly(l-lactide-co-ε-caprolactone) (PLCL) is a potential material to fabricate scaffolds for vascular tissue engineering. In this work, scaffolds with a multilayered structure comprising a combination of porous and fibrous structures were developed. PLCL was used to fabricate the inner layer of the tubular scaffolds using the freeze-drying technique. The inner layer was then covered by an outer layer fabricated by the melt-spinning technique. The morphology and physical structure of the scaffolds were evaluated through SEM micrographs. The freeze-drying technique formed a porous structure, while the melt-spinning method formed a fibrous structure for the bilayer scaffolds. Physicochemical properties were also investigated by DSC and FTIR measurements; no new functional groups were found to have formed during the freeze-drying or melt-spinning processes. Mechanical properties and fracture mechanism under a tensile loading condition were carefully analyzed to characterize the deformation and fracture behaviors. It was found that the bilayer scaffolds exhibited better mechanical properties than single-layer scaffolds with higher maximum stress at 675.41 kPa, strain at maximum stress at 69.42%, fracture energy at 412.45 kJ/m3 and burst pressure at 147.93 kPa. Porosity, swelling ratio and in vitro biodegradation were measured to ensure its suitability for vascular tissue applications. The bilayer scaffolds with both porous and fibrous structures meet the requirements for vascular tissue engineering. [ABSTRACT FROM AUTHOR] more...

• The forming gas (FG) annealing results in a significantly reduction of surface native oxide whereby the amount of Ga–O bonds is decreased demonstrated by the X-ray photoelectron spectra. Hydrogen atoms in H 2 can react with oxygen atoms in the native oxide layer and remove the oxygen to form a surface with oxygen vacancies. Nitrogen molecules in FG can provide nitrogen atoms to fill up these vacancies. Consequently, the removed native oxide layer during FG annealing leads to the formation of a new nitridation layer on the surface. • Compared with N 2 annealing, an on-resistance of 1.68 Ω·mm, a subthreshold swing of 118 mV/dec, a transconductance peak of 513 mS/mm, a gate diode breakdown voltage of surpassing 42 V, and a high current/power gain cutoff frequency (f T / f max) of 165/165 GHz are achieved by the 50-nm InAlN/GaN HEMT annealing by FG H 2 /N 2 on Si substrate. The surface electronic states and defects of gallium nitride based high-electron-mobility transistors (HEMTs) play a critical role affecting channel electron density, electron mobility, leakage current, radio frequency (RF) power output and power added efficiency of devices. This article demonstrates the improved surface properties of InAlN/GaN HEMTs through forming gas (FG) annealing, resulting in a significantly improved electrical properties. The X-ray photoelectron spectra reveals a reduction of surface native oxide after FG H 2 /N 2 annealing whereby the amount of Ga–O bonds is decreased. Compared with N 2 annealing, an on-resistance of 1.68 Ω·mm, a subthreshold swing of 118 mV/dec, a transconductance peak of 513 mS/mm, a gate diode breakdown voltage of surpassing 42 V, and a high current/power gain cutoff frequency (f T / f max) of 165/165 GHz are achieved by the 50-nm InAlN/GaN HEMT on Si substrate. [ABSTRACT FROM AUTHOR] more...

We report a novel method of producing composite substrates by growing diamond films on a 4H–SiC substrate by microwave plasma chemical vapor deposition to enhance the thermal management for thermal diffusion applications in GaN-based RF power devices. Morphology, grain orientation and structure of the diamond films were characterized by scanning electron microscopy, electron backscatter diffraction, X-ray diffraction and Raman spectroscopy. The diamond films were uniform and compact, without voids and gaps observed via cross-sectional view of microscopy, and without any graphite phase and impurity peak. Thermal conductivity (TC) of the diamond-SiC composite substrates was simulated and calculated. Results indicate that the TC of the composite substrates is up to 512.02 ± 6.37 W m−1 K−1 when the SiC thickness is 500 μm, which is 1.53 ± 0.02 times of the pure SiC substrate, and this high TC increases to 1171.13 ± 67.23 W m−1 K−1 after the 4H–SiC substrate is thinned down to 50 μm. The coefficient of thermal expansion (CTE) of the composite substrates can be engineered by changing the thickness of SiC substrate. • A new thermal management approach for GaN-based RF power devices is proposed. • High quality, large area, thick, and uniform diamond films on 2-inch SiC substrate were produced. • TC and CTE of the diamond-SiC composite substrates were simulated and numerically calculated. • TC and CTE of composite substrates can be adjusted by changing substrate thickness. [ABSTRACT FROM AUTHOR] more...

Effects of rapid thermal annealing at different temperatures (700–900 °C) on structural, chemical, and electrical characteristics of lanthanum (La) doped zirconium oxide (ZrO 2 ) atomic layer deposited on 4H-SiC substrates have been investigated. Chemical composition depth profiling analysis using X-ray photoelectron spectroscopy (XPS) and cross-sectional studies using high resolution transmission electron microscopy equipped with energy dispersive X-ray spectroscopy line scan analysis were insufficient to justify the presence of La in the investigated samples. The minute amount of La present in the bulk oxide was confirmed by chemical depth profiles of time-of-flight secondary ion mass spectrometry. The presence of La in the ZrO 2 lattice led to the formation of oxygen vacancies, which was revealed through binding energy shift for XPS O 1s core level spectra of Zr O. The highest amount of oxygen vacancies in the sample annealed at 700 °C has yielded the acquisition of the highest electric breakdown field (∼ 6.3 MV/cm) and dielectric constant value ( k = 23) as well as the highest current–time ( I – t ) sensor response towards oxygen gas. The attainment of both the insulating and catalytic properties in the La doped ZrO 2 signified the potential of the doped ZrO 2 as a metal reactive oxide on 4H-SiC substrate. [ABSTRACT FROM AUTHOR] more...

Neural facilitation is an essential activity-dependent synaptic plasticity in most chemically transmitting synapses. Emerging artificial synaptic devices need to be capable of emulating this function in order to be used in brain-inspired neuromorphic computing systems. In this paper, neural facilitation in natural organic honey based synaptic memristor was investigated. The memristive layer was fabricated by commercially purchased honey via a solution-based process and sandwiched in between Al top electrode and ITO bottom electrode. Two process conditions, 90 °C/8 h and 140 °C/2 h were applied to dry the honey thin film for comparison. Test results show that both devices demonstrated bipolar resistive switching and neural facilitation behaviors, while the memristor with the honey film dried by 90 °C/8 h demonstrated a larger on/off ratio and read memory window, lower current at high-resistant state, and larger facilitation index. The index is also larger than our previously reported honey-memristor with same drying conditions but Ag top electrode, and memristors based on other natural organic materials such as chicken albumen and lignin. The index decayed following two exponential phases as a function of the interval time of the two stimulation voltage pulses, which is similar to biological synapses. Besides shorter pulse interval time, the response of facilitation also enhanced by larger magnitude and width of the stimulation voltage pulses. [Display omitted] • Synaptic neural facilitation of honey-based memristor was investigated. • Largest facilitation gain in natural organic memristors was achieved. • The gains decay with pulse interval time, similar to biological synapses. • Larger pulse magnitude and pulse width, short interval of stimuli enhance the gain. [ABSTRACT FROM AUTHOR] more...

This study has revealed that HNO 3 and H 2 O vapors can be utilized as direct thermal oxidation or postoxidation annealing agents at a temperature above 1000 °C; as they play a major role in simultaneous oxidation/nitridation/hydrogenation processes at the bulk oxide and SiO 2 /SiC interface. The varied process durations of the above-mentioned techniques contribute to the development of thicker gate oxides for high power device applications with improved electrical properties, lower interface-state density and higher breakdown voltage as compared to oxides grown through a more conventional wet (H 2 O vapor only) oxidation technique. The study highlights the effects of hydrogen and nitrogen species on the passivation of structural defects at the bulk oxide and the SiO 2 /SiC interface, which are revealed through the use of Time-of-Flight Secondary Ion Mass Spectroscopy and X-ray Photoelectron Spectroscopy. The physical properties of the substrate after oxide removal show that the surface roughness decreases as the process durations increase with longer hours of H 2 O and HNO 3 vapor exposures on the samples, which is mainly due to the significant reduction of carbon content at the SiO 2 /SiC interface. [ABSTRACT FROM AUTHOR] more...

Highlights: [•] Hydrogen bonding favors the long-range self-assembly leading to an entangled network structure. [•] The non-liquid crystalline gelator can be converted into liquid crystalline organogel. [•] The organogel exhibited monotropic nematic and smectic A phases. [•] The trans-cis isomerization of the azobenzene moiety disrupts the entanglement of gel fibers of self-assembly resulting in gel–sol transition. [•] The organogel is capable of the thermal and photo induced transition from gel–sol and vice versa. [ABSTRACT FROM AUTHOR] more...

Highlights: [•] A new technique of oxidizing SiC in a combination of H2O and HNO3 vapor at various heating temperatures of HNO3 solution. [•] Effects of heating temperature of HNO3 solution on structural, reliability, chemical and electrical properties of the oxide have been investigated. [•] The incorporation of nitrogen and hydrogen as passivation elements particularly in SiO2/SiC interface exhibits improvement in electrical properties and reliability of the grown oxide. [•] Reduction of substrates roughness after oxides removal is attributed by the significant reduction of carbon content at the SiC/SiO2 interface. [ABSTRACT FROM AUTHOR] more...

Abstract: Hierarchically meso–macroporous tetragonal ZrO2 (t-ZrO2) thin films with tunable thickness were prepared by spin-coating method via Pluronic P123 templated sol–gel route. This hierarchically porous ZrO2 was characterized by field-emission scanning electron microscope, atomic force microscope, nitrogen adsorption–desorption isotherm, X-ray diffraction, and ultraviolet–visible spectrometer. Effects of rotation speed and by coating another layer of sol on the first layer during spin-coating on the thickness and mesoporous structure of ZrO2 thin films formed were investigated. The meso–macroporous ZrO2 film coated on a glass substrate possessed an average transmittance higher than 80% in the visible range. It was suggested that the structure of Pluronic P123 was changed as concentration of deposited sol varied over time, which led to the formation of worm-like mesospores coexisted with macropores and rod-like ZrO2 framework. Formation of cracks on ZrO2 thin films was initiated by the structure of meso–macropores and shrinkage of respective films. [Copyright &y& Elsevier] more...

Abstract: We describe the preparation and characterization of zirconia (ZrO2) thin films via sol–gel route by spin-coating method. By utilizing alkoxides Zr[O(CH2)3CH3]4 in the presence of ethanol (EtOH), nitric acid and acetylacetone as a chelating agent, a stable sol of ZrO2 was obtained. Smooth surface morphology with nano-cracks was exhibited for all ZrO2 thin films being fabricated. The film thickness varied from 39 to 206nm depending on the molar ratio of EtOH during the sol preparation and also annealing temperature applied. All ZrO2 films possess high optical transmittance. Refractive index of the thin film was ranging from 1.6 to 2.4 depending on molar ratio of EtOH and annealing temperature. Tetragonal phase of ZrO2 was formed after annealed at 400°C. Crystallinity of ZrO2 was enhanced by increasing molar ratio of EtOH. Crystallite size of tetragonal ZrO2 was ranged from 3.0 to 9.9nm. A hot-water treatment reduced the film thickness and further improved crystallinity of the sol–gel derived oxide. [Copyright &y& Elsevier] more...

Abstract: Mesoporous zirconia (ZrO2) thin films were prepared by dip-coating via Pluronic P123 templated sol–gel route. ZrOCl2·8H2O was used as zirconium (Zr) precursors. Annealing of as-coated ZrO2 thin films is important in order to stiffen the respective films and to remove the Pluronic P123. The mesoporous structure and crystallite size of ZrO2 were characterized systematically by field-emission scanning electron microscope (FESEM), both low- and wide-angle X-ray diffraction, thermal analysis technique and Brunauer–Emmett–Teller method. At annealing temperature of 400°C, amorphous ZrO2 was transformed into tetragonal phase of ZrO2 (t-ZrO2). At 450°C, t-ZrO2 and monoclinic phase of ZrO2 (m-ZrO2) were obtained. By altering heating rate during annealing, volume fraction of t-ZrO2 and m-ZrO2 was changed. FESEM images showed that disordered mesostructures of ZrO2 were formed after annealing. The surface area of mesoporous ZrO2 obtained ranges from 54.33 to 93.39m2/g. [Copyright &y& Elsevier] more...

The rising environmental awareness has spurred the extensive use of green materials in electronic applications, with bio-organic materials emerging as attractive alternatives to inorganic and organic materials due to their natural biocompatibility, biodegradability, and eco-friendliness. This study showcases the natural rubber based resistive switching memory devices and how varying sulphur concentrations (0 - 0.8 wt.%) in natural rubber thin films impact the resistive switching characteristics. The natural rubber was formulated and processed into a thin film deposited on an ITO substrate as the bottom electrode and with an Ag film as the top electrode. The addition of sulphur modifies the degree of crosslinking in the natural rubber thin film, from which the concentration of -C=C- group and density of defect site (S+) are affected, and hence the resistive switching behavior of the memory device. The devices exhibit bipolar resistance with symmetric switching characteristics which are attributed to the formation of conductive paths facilitate by electron transport along -C=C- and S+ defect sites between the two electrodes. Notably, a sample with 0.2 wt.% sulphur exhibits a high ON/OFF ratio (104), a large memory window (5.5 V), prolonged data retention (10 years), and reliable endurance (120 cycles). These findings highlight the potential of natural rubber as a promising material for eco-friendly resistive-switching random access memory applications.&#xD., (© 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.) more...

This paper presents a fabricated solar-blind phototransistor based on hydrogen-terminated diamond. The phototransistor shows a large photocurrent and enhancement of responsivity over conventional two-terminal diamond-based photodetector. These enhancement effects are owing to the internal gain of the phototransistor. The fabricated phototransistor exhibits a high photoresponsivity ( R ) of 2.16 × 10 4 A/W and a detectivity ( D *) of 9.63 × 10 11 jones, with gate voltage ( V G ) and drain voltage of approximately -1.5 V and -5 V, respectively, under 213 nm light illumination. Even at ultralow operating voltage of -0.01 V, the device records satisfactory performance with R and D * of 146.7 A/W and 6.19 × 10 10 jones, respectively. By adjusting the V G , photocurrent generation in the device can be continuously tuned from the fast photoconductive effect to the optical gating effect with high optical gain. When V G increases from 1.4 to 2.4 V, the decay time decreases from 1512.0 to 25.5 ms. Therefore, responsivity, dark current, I photo / I dark , and decay time of the device can be well tuned by V G . more...

The effects of different post-deposition annealing ambients (oxygen, argon, forming gas (95% N2 + 5% H2), and nitrogen) on radio frequency magnetron-sputtered yttrium oxide (Y2O3) films on n-type gallium nitride (GaN) substrate were studied in this work. X-ray photoelectron spectroscopy was utilized to extract the bandgap of Y2O3 and interfacial layer as well as establishing the energy band alignment of Y2O3/interfacial layer/GaN structure. Three different structures of energy band alignment were obtained, and the change of band alignment influenced leakage current density-electrical breakdown field characteristics of the samples subjected to different post-deposition annealing ambients. Of these investigated samples, ability of the sample annealed in O2 ambient to withstand the highest electric breakdown field (approximately 6.6 MV/cm) at 10-6 A/cm2 was related to the largest conduction band offset of interfacial layer/GaN (3.77 eV) and barrier height (3.72 eV). more...

This study describes a novel fabrication technique to grow gold nanoparticles (AuNPs) directly on seeded ZnO sacrificial template/polymethylsilsesquioxanes (PMSSQ)/Si using low-temperature hydrothermal reaction at 80°C for 4 h. The effect of non-annealing and various annealing temperatures, 200°C, 300°C, and 400°C, of the ZnO-seeded template on AuNP size and distribution was systematically studied. Another PMMSQ layer was spin-coated on AuNPs to study the memory properties of organic insulator-embedded AuNPs. Well-distributed and controllable AuNP sizes were successfully grown directly on the substrate, as observed using a field emission scanning electron microscope followed by an elemental analysis study. A phase analysis study confirmed that the ZnO sacrificial template was eliminated during the hydrothermal reaction. The AuNP formation mechanism using this hydrothermal reaction approach was proposed. In this study, the AuNPs were charge-trapped sites and showed excellent memory effects when embedded in PMSSQ. Optimum memory properties of PMMSQ-embedded AuNPs were obtained for AuNPs synthesized on a seeded ZnO template annealed at 300°C, with 54 electrons trapped per AuNP and excellent current-voltage response between an erased and programmed device. more...

The band alignment of ZrO2/interfacial layer/Si structure fabricated by simultaneous oxidation and nitridation of sputtered Zr on Si in N2O at 700°C for different durations has been established by using X-ray photoelectron spectroscopy. Valence band offset of ZrO2/Si was found to be 4.75 eV, while the highest corresponding conduction offset of ZrO2/interfacial layer was found to be 3.40 eV; owing to the combination of relatively larger bandgaps, it enhanced electrical breakdown field to 13.6 MV/cm at 10-6 A/cm2. more...