Applied Physics A最新文献

The objective of this research is to explore the influence of praseodymium incorporation into cobalt ferrite nanoparticles, derived from sol-gel, on their response to hydrogen gas. Additionally, we investigated the hydroxyl scavenging capacity of praseodymium ions by comparing the results obtained at low relative humidity (RH ~ 20%) and high relative humidity (RH ~ 50%). Our findings revealed that the optimal gas sensing properties of the CoFe_2 − xPr_xO₄ semiconductor (where x = 0, 0.02, 0.04, 0.06) were achieved with a Pr concentration of 0.02 at a working temperature of 300 °C. Scanning electron microscopy and mapping Energy-dispersive X-ray spectroscopy (EDS) analysis of Pr-doped CoFe₂O₄ nanoparticles provided evidence for the existence of a secondary phase at higher Pr concentrations, which impacted gas-sensing performance when x > 0.02. Furthermore, the addition of palladium proved to be effective in enhancing the moisture-resistant gas-sensing properties of the CoFe_1.98Pr_0.02O₄ gas sensor. The synergistic interaction between palladium and praseodymium ions was responsible for the observed enhanced anti-humidity and hydrogen gas detection characteristics.

(K_0.41Na_0.59)(Nb_0.84Sb_0.06Ta_0.10)O₃ + x wt% CuO (KNNST + x Cu, 0 ≤ x ≤ 0.1) ceramics were prepared using a two-step sintering technique. The effects of CuO on the sintering behavior, the phase structure, surface morphologies, and the piezoelectric properties of the (K_0.41Na_0.59)(Nb_0.84Sb_0.06Ta_0.10)O₃ (KNNST) ceramics were investigated in details. The experimental results showed that CuO doping improved the “hardened” KNNST + x Cu ceramics through reduced dielectric loss (tanδ) and greatly enhanced mechanical quality factor (Q_m). Additionally, CuO doping significantly improved the piezoelectric properties at low sintering temperatures. The KNNST ceramics obtained excellent overall electrical properties of d₃₃ = 265 pC/N, k_p = 0.50, k_p = 0.41, Q_m = 420, ε_r = 1173, tanδ = 0.015, P_r = 15 µC/cm², and T_m = 325 °C at a sintering temperature of 1050 °C and 0.075 wt% CuO content, which showed that KNNST ceramics were promising candidates for power applications. Besides, CuO content of 0.1 wt% had the highest recoverable energy storage density (W_rec) of 0.34 J/cm³ and energy storage efficiency (η) of 61.0%, expanding the scope of application for CuO-doped KNNST ceramics.

Thermoelectric materials, such as SiGe alloys, have gained significant attention for their application in electricity generation at high temperatures. However, improving the thermal and electrical transport properties of n-type SiGe remains a challenge. In this work, n-type Silicon-Germanium alloys (SiGe) with dispersed nano-TiO₂ particles (Si₈₀Ge₂₀P₃-x wt% nano-TiO₂, x = 0, 3, 4, 5, 6) were synthesized by ball milling followed by spark plasma sintering. The effects of nano-TiO₂ particles on the electrical and thermal transport properties were investigated. The power factor of n-type SiGe alloys dispersed nano-TiO₂ particles was slightly decreased. However, the thermal conductivity had a significant reduction because of enhanced phonon scattering resulted from the multi-dimensional defect features. Coherent interfaces formed between SiGe alloys and nano-TiO₂ particles can generate phonon scattering in the range of medium to long wavelength. A dimensionless figure-of-merit (zT) of 1.64 at 1073 K was obtained in the sample of Si₈₀Ge₂₀P₃-4 wt% nano-TiO₂, which is 40% higher than the Si₈₀Ge₂₀P₃ alloy. This work provides a new approach to optimizing the thermoelectric performance and promoting the potential applications.

Fabrication of thin films of WSe₂ is challenging and various methods are being explored. This study investigates the thermoelectric properties of tungsten diselenide thin films. The thin films are fabricated on Si substrates by using two-step processes. Here, the selenization of DC sputtered W thin films was carried out at different temperatures in the range of 400 to 500^oC in the steps of 50^oC. The crystal structure is found to be hexagonal and crystallite sizes increase with the selenization temperature. The morphology of the thin films selenized at 400^oC shows no separated particles while raising the selenization temperature from 450^oC to 500 °C uniform distribution of particles is observed. The shape of the particles was found spherical and rod-like. The Raman spectra show four modes: E_1g,(:{text{E}}_{2text{g}}^{1})_, A_1g, and (:{text{B}}_{2text{g}}^{1}). Here, (:{text{B}}_{2text{g}}^{1}) is associated with the interlayer interaction. The electrical resistivities of these thin films exhibit the conduction mechanism of the band conduction model. The highest Seebeck coefficient was reported for S500 (-9.15µV/K). Also, the power factor of S500 is the highest i.e. 13.4 Χ 10^− 5µW/mK² This study shows the potential use of the selenization process to fabricate the WSe₂ thin films and optimize temperature for better thermoelectric properties.

Silicon carbide (SiC), as a key material in the third-generation semiconductor industry, holds critical importance due to its superior thermal conductivity, high breakdown voltage, and wide bandgap. However, the conventional chemical mechanical polishing (CMP) process used in SiC wafer manufacturing is time-consuming and resource-intensive, involving significant material consumption and prolonged processing times. In this study, we explored the application of laser-assisted dry ablation as a pre-treatment for CMP. The experimental results showed that the single laser ablation depth of SiC is about 2 μm, and demonstrated that a laser spot overlap rate between 30% and 60% can generate a relatively lower surface roughness of SiC. This optimal range of overlap ensures a smoother ablation process, minimizing the irregularities on the SiC wafer surface. After a single pass of laser dry ablation, SiC hardness can be reduced to less than 3% of its original value, while material removal depth can be precisely controlled by adjusting the number of laser passes. With 50 repetitions, a material removal depth of nearly 30 μm was achieved. This reduction in hardness and enhanced material removal directly contribute to improve the efficiency of subsequent CMP processes by reducing polishing time and wear on grinding heads. In addition, after more than 5 times of laser treatment and then wet grinding, the thickness achievement rate can be increased from 73 to 93%. These results provide the important academic reference value. The integration of laser-assisted ablation into SiC wafer processing presents significant advantages in terms of increasing production throughput and reducing overall manufacturing costs. By simplifying the polishing steps and minimizing consumable usage, this approach offers a promising avenue for industrial applications, particularly in enhancing SiC wafer yield and optimizing semiconductor production workflows.

Based on the previous optimal concentration of Er³⁺/Yb³⁺/Mo⁴⁺/Sb co-doped BiTa₇O₁₉ (BTO), Gd³⁺, La³⁺ or Lu³⁺ is planned to be doped into BTO: Er³⁺/Yb³⁺/Mo⁴⁺/Sb for further improving the upconversion luminescence (UCL) intensity under 980 nm laser excitation. These samples are prepared by solid phase sintering. The green UCL integral intensity of Gd³⁺, La³⁺ or Lu³⁺ doping samples reaches 2.87, 2.67 and 2.52 times than that of β-NaYF₄:Er³⁺/Yb³⁺, respectively. It can be attributed to the change in Er³⁺/Yb³⁺ doped site’ symmetry, bandgap increases and local structure changes. The maximum absolute sensitivity (S_A) and relative sensitivity (S_R) is got as 0.01098 K^− 1 at 356 K and 0.00776 K^− 1 at 303 K, respectively. Gd³⁺, La³⁺ or Lu³⁺ doping BTO: Er³⁺/Yb³⁺/Mo⁴⁺/Sb can be applied in luminescence display and temperature sensing.

In recent years, hafnium nitride films have demonstrated remarkable potential in numerous fields on account of their stability and resistance properties. In this study, a series of Hf-N films were fabricated by magnetron sputtering technology. The impacts of the Ar/N₂ ratio on the micro-morphology and microstructure of the films were investigated, and the relationship between the film properties and its microstructure was further analyzed. It was observed that the surface morphology of the Hf-N films, which grew in a columnar crystal form, became denser with the elevation of the Ar/N₂ ratio. When the Ar/N₂ ratio was increased to 50:2.5, the composition of the film transformed into a single HfN phase, and this single-phase composition remained unaltered within a wide range of nitrogen flow. We discovered that the compressive stress and texture coefficient significantly contributed to enhancing the nanohardness of the films. Specifically, when the Ar/N₂ ratio was 50:2.5, the film exhibited a maximum hardness value of 28.4 GPa along with an elastic recovery value of up to 63.1%. After undergoing high-temperature oxidation, the film maintained a stable structure and possessed good oxidation resistance. Moreover, its corrosion resistance was two orders of magnitude higher than that of the substrate material.

We applied nanosecond pulsed laser ablation to reduce the reflectivity of metal surfaces. The change in reflectivity was studied at different laser scanning pitches (i.e., pulse number densities) and the trends obtained were correlated with the morphological and compositional changes induced by the ablation. In the case of copper, we found that it wasn’t the laser etching itself that caused the darkening of the surface, but rather the nanoclusters and nanoparticles produced in the cooling ablation plume as they fell back onto the surface. Our model calculations confirmed the role of micro- and nanostructures and the presence of copper oxides in reducing the reflectivity of ablated copper.

The supercapattery integrates the rapid power output of supercapacitors (SCs) with the substantial energy storage capacity typical of batteries. Metal-organic frameworks (MOFs) offer a stable porous structure that enhances efficient ion transport through strong metal-organic linkages. Metal diselenides contribute high conductivity and stability, strengthening the composite’s energy and power densities. Polyaniline (PANI) provides pseudocapacitive behavior, further improving charge storage. This study presents a PCN-222/NiSe₂@PANI composite synthesized hydrothermal, ensuring strong material integration and uniform distribution. Surface morphology and phase purity, analyzed by SEM and XRD, confirmed structural uniformity and stability. Electrochemical testing revealed a specific capacity (Qs) of 2449 ± 5 C/g at 2.0 A/g in a tri-electrode configuration. A two-electrode supercapattery, fabricated using PCN-222/NiSe₂@PANI as the anode and activated carbon (AC) as the cathode, achieved an energy density of 68 Wh/kg and a power density of 900 W/kg, with 87.6% capacity retention over 8,000 GCD cycles, surpassing standard benchmarks. The power-law analysis yielded b-fitting values between 0.58 and 0.75, indicating hybrid charge storage. The composite exhibited promising hydrogen evolution reaction (HER) activity, with an overpotential of 87 ± 5 mV and a Tafel slope of 78 ± 5 mV/dec, showing high catalytic efficiency and favorable charge transfer kinetics. These results position PCN-222/NiSe₂@PANI as a strong contender for high-performance supercapattery applications, advancing energy storage and conversion technologies.

Surfaces with gradient wetting properties are crucial for alleviating water scarcity and efficient recycling, as it can be used for directed transport and collection of water. However, a major challenge is how to efficiently manufacture multi-scale micro-nano structures to increase surface wetting gradients. In this study, a composite processing that combines nanosecond laser oblique incidence and thermal oxidation to fabricate microgroove-nanowire (CuO) hierarchical structures with gradient wettability is proposed. Laser oblique incidence scanning is employed to fabricate microgroove structures with gradient geometric dimensions and chemical composition on the Cu surface, which in turn induced gradient wetting properties and facilitated the directed movement of droplets. The effect of scanning times on gradient structure and its wetting properties is also discussed in detail. To further enhance the directional flow distance of droplets, dense CuO nanowires are grown on the surface of microgrooves through thermal oxidation treatment, forming a micro-nano dual scale structure. The growth mechanism of nanowires is revealed, and the effects of thermal oxidation temperature and duration on nanowire growth and gradient wetting properties are discussed in detail. The gradient in contact angles, in conjunction with the variation in energy barriers in different directions, leads to more pronounced anisotropic wetting. Compared to the single microgroove structures, the directional flow distance of microgroove-nanowire dual scale structure is increased by about 50%. The proposed laser and thermal oxidation composite process provides a new strategy for efficiently manufacturing micro-nano dual scale structures and further enhancing surface gradient wetting performance.