Study of the Rolling Effect on MoS2-Carbon Fiber Density and Its Consequences for the Functionality of Li-Ion Batteries.

In this study, an electrode slurry composed of molybdenum disulfide (MoS2) and vapor-grown carbon fiber (VGCF) prepared through a solid-phase synthesis method was blade-coated onto copper foil to form a thick film as the anode for lithium-ion batteries. In previously reported work, MoS2-based lithium-ion batteries have experienced gradual deformation, fracture, and pulverization of electrode materials during the charge and discharge cycling process. This leads to an unstable electrode structure and rapid decline in battery capacity. Furthermore, MoS2 nanosheets tend to aggregate over charge and discharge cycles, which diminishes the surface activity of the material and results in poor electrochemical performance. In this study, we altered the density of the MoS2-carbon fiber/Cu foil anode electrode by rolling. Three different densities of electrode sheets were obtained through varying rolling repetitions. Our study shows the best electrochemical performance was achieved at a material density of 2.2 g/cm3, maintaining a capacity of 427 mAh/g even after 80 cycles.

Performance Enhancement of Three-Dimensional MAPbI3 Perovskite Solar Cells by Doping Perovskite Films with CsPbX3 Quantum Dots.

Perovskite thin films directly impact solar cell properties, making defect reduction crucial in perovskite solar cell research. In our study, we used perovskite quantum dots in the anti-solvent to act as nucleation centers in MAPbI3 thin films. These centers had lower nucleation barriers than homogeneous nucleation, improving perovskite crystallinity, reducing defects, and extending carrier lifetime. Fine-tuning the energy band also enhanced carrier transport. The most effective results were obtained using CsPb(Br0.5 I0.5)3 perovskite quantum dots. The resulting device, ITO/SnO2/MAPbI3 (300 nm)/spiro-OMeTAD (200 nm)/Ag (100 nm), achieved a 12.88% power conversion efficiency, a 16% increase from the standard element. The modified device maintained approximately 95% of its efficiency over 100 h in a 70% humidity environment.

Effects of Post-Annealing on the Properties of ZnO:Ga Films with High Transparency (94%) and Low Sheet Resistance (29 Ω/square).

This study presents gallium-doped zinc oxide (ZnO:Ga, GZO) thin films. GZO thin films with both high transparency and low sheet resistance were prepared by RF sputtering and then post-annealed under nitrogen and hydrogen forming gas. With post-annealing at 450 °C, the proposed films with a film thickness of 100 nm showed high transparency (94%), while the sheet resistance of the films was reduced to 29 Ω/square, which was comparable with the performances of commercial indium tin oxide (ITO) samples. Post-annealing under nitrogen and hydrogen forming gas enhanced the films' conductivity while altering the thin-film composition and crystallinity. Nitrogen gas played a role in improving the crystallinity while maintaining the oxygen vacancy of the proposed films, whereas hydrogen did not dope into the thin film, thus maintaining its transparency. Furthermore, hydrogen lowered the resistance of GZO thin films during the annealing process. Then, the detailed mechanisms were discussed. Hydrogen post-annealing helped in the removal of oxygen, therefore increasing the Ga3+ content, which provided extra electrons to lower the resistivity of the films. After the preferable nitrogen/hydrogen forming gas treatment, our proposed films maintained high transparency and low sheet resistance, thus being highly useful for further opto-electronic applications.

Application of a Perovskite NIR-LED with Highly Stable FAPbI3@SiO2 Core-Shell Nanocomposites in a SPR Sensing Platform.

In recent years, the demand for detection and diagnostic methods has consistently risen due to the aging of the population and the increase in the number of patients with chronic diseases. Label-free biomedical detection techniques have emerged as indispensable instruments for diagnosing a variety of diseases. The development of label-free and highly sensitive near-infrared (NIR) biomedical detection technology has attracted considerable attention. As a label-free, swift, and cost-effective analytical technique, it has demonstrated immense potential for a wide range of applications. We successfully assembled FAPbI3 near-infrared perovskite quantum dots (NIPQDs) into SiO2 shells using a rapid room-temperature atmospheric synthesis method, obtaining monodisperse FAPbI3@SiO2 nanocomposites (NCs) with a high photoluminescence quantum yield (PLQY) of 72%. Additionally, the incorporation of hydrophobic multi-branched trioctylphosphine oxide effectively passivated the surface defects of FAPbI3 NIPQDs and suppressed the hydrolysis rate of tetraethoxysilane, enabling the formation of a highly stable and high PLQY nanoscale-particle level within the FAPbI3@SiO2 core-shell structure. Notably, we successfully incorporated FAPbI3@SiO2 core-shell NCs onto InGaN blue chip as NIR excitation light sources for surface plasmon resonance sensing platforms, providing a novel platform for bioanalytical detection. With a detection sensitivity of 6302.5 nm/RIU, the system demonstrated high sensitivity, stability, and dependability. This achievement expands the biomedical research field's capacity for diagnosis, monitoring, and treatment.

Multi-Level Resistive Al/Ga2O3/ITO Switching Devices with Interlayers of Graphene Oxide for Neuromorphic Computing.

Recently, resistive random access memory (RRAM) has been an outstanding candidate among various emerging nonvolatile memories for high-density storage and in-memory computing applications. However, traditional RRAM, which accommodates two states depending on applied voltage, cannot meet the high density requirement in the era of big data. Many research groups have demonstrated that RRAM possesses the potential for multi-level cells, which would overcome demands related to mass storage. Among numerous semiconductor materials, gallium oxide (a fourth-generation semiconductor material) is applied in the fields of optoelectronics, high-power resistive switching devices, and so on, due to its excellent transparent material properties and wide bandgap. In this study, we successfully demonstrate that Al/graphene oxide (GO)/Ga2O3/ITO RRAM has the potential to achieve two-bit storage. Compared to its single-layer counterpart, the bilayer structure has excellent electrical properties and stable reliability. The endurance characteristics could be enhanced above 100 switching cycles with an ON/OFF ratio of over 103. Moreover, the filament models are also described in this thesis to clarify the transport mechanisms.

High Linearity Synaptic Devices Using Ar Plasma Treatment on HfO2 Thin Film with Non-Identical Pulse Waveforms.

We enhanced the device uniformity for reliable memory performances by increasing the device surface roughness by exposing the HfO2 thin film surface to argon (Ar) plasma. The results showed significant improvements in electrical and synaptic properties, including memory window, linearity, pattern recognition accuracy, and synaptic weight modulations. Furthermore, we proposed a non-identical pulse waveform for further improvement in linearity accuracy. From the simulation results, the Ar plasma processing device using the designed waveform as the input signals significantly improved the off-chip training and inference accuracy, achieving 96.3% training accuracy and 97.1% inference accuracy in only 10 training cycles.

Effects of phosphor distribution and step-index remote configuration on the performance of white light-emitting diodes.

Phosphor-converted white light-emitting diodes (pc-WLEDs) are fabricated by combining CaSi2O2N2:Eu2+ and Ca2Si5N8:Eu2+ phosphors with a blue chip. Experimental results demonstrate that placing the red phosphor layer above the yellow one (Y down/R up) yields the highest luminous efficiency, making it the preferable phosphor distribution for pc-WLEDs rather than Y up/R down. This finding suggests that the extent of overlap between the emission spectrum of short-emission-wavelength phosphors and the excitation spectrum of long-emission-wavelength phosphors and their luminous efficacy of radiation should be taken into account simultaneously when studying the optical characteristics of pc-WLEDs. Compared to common pc-WLEDs with silicone gel as the remote layer, the proposed step-index remote configuration exhibits superior luminous efficiency because of reduced total internal reflection and Fresnel loss.

Fabrication of high-power piezoelectric transformers using lead-free ceramics for application in electronic ballasts.

CuO is doped into (Na(0.5)K(0.5))NbO(3) (NKN) ceramics to improve the piezoelectric properties and thus obtain a piezoelectric transformer (PT) with high output power. In X-ray diffraction patterns, the diffraction angles of the CuO-doped NKN ceramics shift to lower values because of an expansion of the lattice volume, thus inducing oxygen vacancies and enhancing the mechanical quality factor. A homogeneous microstructure is obtained when NKN is subjected to CuO doping, leading to improved electrical properties. PTs with different electrode areas are fabricated using the CuO-doped NKN ceramics. Considering the efficiency, voltage gain, and temperature rise of PTs at a load resistance of 1 kΩ, PTs with an electrode with an inner diameter of 15 mm are combined with the circuit design for driving a 13-W T5 fluorescent lamp. A temperature rise of 6°C and a total efficiency of 82.4% (PT and circuit) are obtained using the present PTs.

Effects of improved process for CuO-doped NKN lead-free ceramics on high-power piezoelectric transformers.

In this paper, the effects of the electrical proper- ties of CuO-doped (Na(0.5)K(0.5))NbO(3) (NKN) ceramics prepared separately using the B-site oxide precursor method (BO method) and conventional mixed-oxide method (MO method) on high-power piezoelectric transformers (PTs) were investigated. The performances of PTs made with these two substrates were compared. Experimental results showed that the output power and temperature stability of PTs could be enhanced because of the lower resonant impedance of the ceramics prepared using the BO method. In addition, the output power of PTs was more affected by the resonant impedance than by the mechanical quality factor (Q(m)) of the ceramics. The PTs fabricated with ceramics prepared using the BO method showed a high efficiency of more than 94% and a maximum output power of 8.98 W (power density: 18.3 W/cm(3)) with temperature increase of 3°C under the optimum load resistance (5 kΩ) and an input voltage of 150 V(pp). This output power of the lead-free disk-type PTs is the best reported so far.

UV-ozone-treated ultra-thin NaF film as anode buffer layer on organic light emitting devices.

An ultra-thin NaF film was thermally deposited between ITO and NPB as the buffer layer and then treated with the ultraviolet (UV) ozone, in the fabrication of organic light emitting diodes (ITO/NaF/NPB/Alq(3)/LiF/Al) to study its effect on hole-injection properties. The treatment drastically transforms the role of NaF film from hole-blocking to hole-injecting. This transformation is elucidated using hole-only devices, energy band measurement, surface energy, surface polarity, and X-ray photoelectron spectra. With the optimal thickness (3 nm) of the UV-ozone-treated NaF layer, the device performance is significantly improved, with a turn-on voltage, maximum luminance, and maximum current efficiency of 2.5 V, 15700 cd/m(2), and 4.9 cd/A, respectively. Results show that NaF film is not only a hole-blocking layer, but also a promising hole-injecting layer after UV-ozone treatment.

Doping effects of CuO additives on the properties of low-temperature-sintered PMnN-PZT-based piezoelectric ceramics and their applications on surface acoustic wave devices.

To develop the anisotropic ceramic substrate with low sintering temperature for surface acoustic wave (SAW) applications, the low cost and feasible material with moderate piezoelectric properties, good dielectric properties, and higher Curie temperature were explored. The piezoelectric ceramics with compositions of Pb[(Mn(1/3)Nb(2/3))(0.06-) (Zr(0.52)Ti(0.48))0.94] O(3) (PMnN-PZT) + 0.5 wt.% PbO + x wt.% CuO (0.05 = x = 0.3) had been prepared by the conventional mixed-oxides method. CuO dopants were used as the sintering aid to improve the bulk density under low sintering temperature (i.e., 980-1040 degrees C). The phase structures, microstructures, frequency behavior of dielectric properties (up to 50 MHz), piezoelectric properties, ferroelectric properties, and temperature stability with the amount of CuO additive were systematically investigated. Experimental results showed that the sintering temperature could be lowered down to 1020 degrees C and still keep reasonably good piezoelectric activity (i.e., high electromechanical coupling factor (k(p)), (k(t)) and dielectric and ferroelectric properties. The preferable composition, obtained at x = 0.1, presented the values of the electromechanical coupling factor (k(p)) (k(t)), mechanical quality factor (Q(m)), piezoelectric charge constant (d(33)), dielectric constant, dielectric loss, temperature coefficient of resonant frequency (TCF(B)), and Curie point (T(c)) of 0.54, 0.48, 850, 238 pc/N, 1450, 0.0023, 1.1 kV/mm, 26 coul/cm(2), -150 ppm/ degrees C, and 348 degrees C. Using this developed low-temperature-sintered material to make the piezoelectric substrate, the SAW filter was fabricated and its properties were measured. Results showed that this device possessed very high value of k(2)(7.13%) with a good TCF (-40.15 ppm/ degrees C), and a surface wave velocity (V(P)) of 2196 m/s.

The improvement of dynamic characteristics of ultrasonic therapeutic transducers using fine-grain PZT-based piezoceramics.

Optimizing the dynamic resonant characteristics of ultrasonic therapeutic transducers depends most importantly on fine-grain piezoceramics with good resonant properties. In this paper, we prepare and compare modified Pb(0.99)Sr(0.01)[0.03(Mn(1/3)Nb(2/3))-0.97(Zr(0.51)Ti(0.49))]O(3) piezoceramics with 0.1 wt% CaCO(3) and 0.8 wt% PbO additives (PMZT3) synthesized by B-oxides precursor (BO) and conventional ceramic mixed-oxide methods (MO). Our experimental results show that the BO-type piezoceramics have better grain microstructure and better material properties [e.g., d(33)= 340 pc/N, k(t)= 0.52, Q(m)= 1250, temperature coefficient of change rate of resonant frequency (TCF) = 0.01%/degrees C, and temperature coefficient of change rate of clamped capacitance (TCC) = 0.18%/degrees C]. We construct 1-MHz transducers using our BO and MO types of piezoceramics and examine their dynamic resonant characteristics as the transducers are driven by a power driver with open-loop control. Results show that the transducers with the BO-type piezoceramics have better dynamic characteristics, such as time stability (e.g., aging rate of resonant frequency at thickness mode = 0.26%/decade cycle, and aging rate of clamped capacitance = 0.55%/decade cycle) and temperature stability as BO-type piezoceramics. Furthermore, we observe that the clamped capacitance variation has more influence on the transducer dynamic characteristics than the resonant frequency variation, and we verify the observation from the partial derivative ratio of the transfer function derived by a simulated ultrasonic equivalent circuit system. It is concluded that the BO-type piezoceramics are better candidates than the MO-type samples for obtaining optimum dynamic resonant characteristics in ultrasonic therapeutic transducers.

The effects of ZnO films on surface acoustic wave properties of modified lead titanate ceramic substrates.

Poly-crystal zinc oxide (ZnO) films with c-axis (002) orientation have been successfully grown on the strontium (Sr) modified lead titanate ceramic substrates with different Sr dopants by r.f. magnetron sputtering technique. Highly oriented ZnO films with c-axis normal to the substrates can be obtained under a total pressure of 10 mTorr containing 50% argon and 50% oxygen and r.f. power of 70 W for 3 hours. Crystalline structures of the films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The phase velocity, electromechanical coupling coefficient and temperature coefficient of frequency of surface acoustic wave (SAW) devices with ZnO/IDT/PT (IDT, inter-digital transducer; PT, PbTiO3 ceramics) structure were investigated. The devices with ZnO/IDT/PT structure shows that the ZnO film effectively raise the electromechanical coupling coefficient (kappa2) from 3.8% to 9.9% of the device with the concentrations of Sr dopants of 0.15. It also improves the temperature coefficient of frequency of SAW devices.

Fabrication of modified lead titanate piezoceramics with zero temperature coefficient and its application on SAW devices.

The Samarium-modified, lead titanate ceramics with a composition of (Pb0.67Ca0.15Sr0.06Sm0.08) (Ti0.98Mn0.02)O3 were prepared by conventional mixed-oxide method. By properly varying the sintering and poling conditions, the samples with zero temperature coefficient of resonant frequency were fabricated. The piezoelectric and dielectric properties were measured; it showed that the samples with zero temperature coefficient still keep high-thickness, electromechanical coupling coefficient, kt (>0.55), and small planar electromechanical coupling coefficient, kp. Surface acoustic wave (SAW) filters were fabricated; and the properties, including phase velocity and electromechanical coupling coefficient, were measured. Microstructural and compositional analyses have been carried out using scanning electron microscopy and x-ray diffraction.

An investigation of the dependence of ZnO film on the sensitivity of Love mode sensor in ZnO/quartz structure.

Love mode acoustic devices are very promising as biosensors in liquid environments because of their high sensitivity. An experimental study of Love mode sensors based on ZnO/90 degrees rotated ST-cut quartz structure with different sputtering conditions to deposit ZnO films is presented. In order to achieve sensor with higher sensitivity, the effects of sputtering substrate temperatures to deposit ZnO films on the sensitivity of viscosity and conductivity were investigated. Phase velocity, sensitivity and temperature coefficient of frequency (TCF) of Love wave devices have been studied. The Love wave sensor has higher sensitivity as sputtering ZnO films on the unheated substrate than that of on the heated substrate. The maximum sensitivity up to -18.77 x 10(-8) m(2) s kg(-1) of ZnO film with thickness of 1.8 microm for a wavelength of 40 microm is much bigger than SiO(2)/quartz structure. In this research, we report ZnO/90 degrees rotated ST-cut quartz structure of Love wave sensors with high sensitivity of viscosity and conductivity in liquid circumstance and TCF of quartz is compensated by ZnO film.

Effects of strontium on the surface acoustic wave properties of Sm-modified PbTiO3 ceramics.

The Sm-modified lead titanate ceramics with a composition of (Pb(0.88-x)Sr(x)Sm(0.08))(Ti(0.98)Mn(0.02))O(3); x = 0.05-0.25 were prepared by conventional mixed-oxide method. Surface acoustic wave (SAW) properties, including phase velocity, electromechanical coupling coefficient and temperature coefficient of frequency, were measured. The experiments successfully showed that Sr additive is helpful to obtain higher phase velocity and high electromechanical coupling coefficient. The SAW properties of our samples (V(p),k(2)) are better than some commercially-made PZT and PT samples.