Physics of the Solid State最新文献

In this work, titanium dioxide nanoparticles, titanium dioxide nanofibers and zinc oxide nanoparticles were synthesized by sol-gel method and the structure and performance of these nanomaterials on color-sensitive solar cells along with carbon nanotubes as cathodes have been discussed using XRD, SEM, and cu-rrent–voltage curve. The results of XRD analysis of titanium dioxide and zinc oxide nanoparticles showed that these particles have good crystalline structure without any impurity peaks in the graphs. According to the result, titanium dioxide nanofiber shows the best electrical efficiency, which is shown by the slope of the current–voltage curve for this sample among the titanium dioxide nanoparticles and zinc oxide nanoparticles.

We report on fabrication and characterization of high-performance ZnSe-based metal–semiconductor–metal (MSM) ultraviolet (UV) photodetectors with different Schottky contacts (Cr/Au, Ni/Au, Ag‑nanowire (Ag-NW)) and device structures (conventional planar contacts, interdigitated contacts, hybrid nanowire contacts). At room temperature, the low values of dark current of 0.71, 0.59, and 0.36 nA at bias voltage of 15 V were achieved for devices with Cr/Au, Ni/Au, and hybrid Ni/Au and Ag-NW contacts, respectively. A very high responsivity of 5.40 A W^–1 and detectivity of 3.4 × 10¹¹ cm W^–1 Hz^1/2 at bias voltage of 15 V for light with a wavelength of 325 nm is obtained for UV photodetector with Ni/Au interdigitated contacts. The best performance of devices with Ni/Au interdigitated contacts due to the higher Schottky barrier height of ~1.49 eV for Ni/Au contacts in comparison with ~1.26 eV for Cr/Au contacts is found. The measured response times of all UV photodetectors is in the µs-range and is limited by the RC time of the measurement system. Thus, this study demonstrates the high potential of ZnSe-based MSM structures with Ni/Au interdigitated and hybrid Ni/Au and Ag-NW contacts as a high-sensitive ultrafast UV photodetectors, which are promising for the applications, such as UV tomography and UV high-speed communication systems.

We theoretically investigate phonon and thermal properties in germanium nanowires with square cross-sections ranging from 2.26 to 27.72 nm. Using a face-centered cubic cell model for lattice vibrations and the Boltzmann transport equation approach, we find that the thermal conductivity of Ge nanowires is 3 to 20 times lower than in bulk c-Ge, depending on the roughness of the nanowire surfaces. This significant decrease in lattice thermal conductivity results from the interplay between two effects: the redistribution of phonon energy spectra due to spatial confinement and phonon boundary scattering. We calculate the temperature distribution in a nanometer-thick porous germanium film with a thermal conductivity of 3.5 W/(m K), typical for rough Ge nanowires. Our results indicate the potential for localized heating in specific regions, reaching temperatures up to ~950 K. This finding aligns well with previous experimental estimations made using Raman spectroscopy.

Since magnetic energy is exchanged across spin domains, magnetic anisotropy is important for applications using spintronic devices. FeCo is unique among d-block magnetic materials because of its strong spin polarization and higher-than-room-temperature of Curie temperature. In current day-to-day electrical applications, dimensions shrink down to the nanoscale range. It has been demonstrated that the thin film technique improves these materials’ basic characteristics. The FeCo thin film was prepared on a glass substrate with various thicknesses such as 10, 30, and 50 nm. The magnetic properties and surface were investigated to corresponding thicknesses at room temperature by using the AFM and VSM techniques, respectively. The magnetic properties varied by the topography nature of the prepared thin films and all the thickness films exhibited the hysteresis loop that confirmed that thin film has a magnetic nature at room temperature. For spin valve devices, electrode preferences differ; instead, the same magnetic material with varying thicknesses may be used as top and bottom electrodes.

This study explores the impact of annealing temperature (TA) on the sol-gel-deposited ZnO thin‑films’ nonlinear optical characteristics on glass substrates. By examining the surface topography with Atomic Force Microscopy (AFM), samples that were annealed at 450°C were found to have the ideal surface smoothness of 9.27 nm. Utilising the second harmonic output of a Nd:YAG laser, the Z-scan technique, UV‑Vis-NIR transmission, and X-ray diffraction (XRD) were employed in the analysis of the films. The materials’ nonlinear optical (NLO) characteristics revealed that the annealing temperature had a significant impact. Notably, the maximum nonlinear optical susceptibility, χ⁽³⁾, was achieved at an annealing temperature of 450°C, indicating a direct correlation between thermal processing and the enhancement of NLO performance.

Multiple quantum-wells light-emitting diodes (MQWs-LEDs) are high-performance electroluminescent light sources, which is widely used in solid state lighting, medical, industrial and other fields. Understanding the light emission origin and mechanisms of MQWs-LEDs is crucial for their practical applications. Here, we show the excellent ultraviolet (UV) and deep-ultraviolet (DUV) emissions from ZnO/AlGaN MQWs-LEDs using Technology Computer Aided Design (TCAD) simulation, which deviates from the typical ZnO heterojunction LEDs. The adjustment of the structural parameters of the MQWs was performed to control the emission wavelength in the range of 335–366 nm. After parameter optimization, 342.6–348.7 nm DUV EL from ZnO/AlGaN MQWs is obtained successfully. The deconvolution analysis of the EL spectra was conducted to investigate the origin of the emissions. The results indicate that the structural parameter operation-induced emission blue-shift results from the quantum confinement effect. This work provides new references for designing ZnO-based MQWs and preparing new DUV LEDs.

Ba-doped bismuth ferrite with chemical composition Bi_1 – xBa_xFeO₃ (x = 0.1, 0.2, 0.3, 0.4, and 0.5) nanoparticles were synthesized by the wet chemical sol–gel method. The substitution of Ba²⁺ at the Bi³⁺ site was meant to improve the resistivity, enhance magnetic properties, and suppress the impurity phases of BiFeO₃. The samples synthesized were later subjected to X-ray diffraction (XRD) analysis, Field emission scanning electron microscope (FESEM) with energy dispersive spectroscopy (EDS), Magnetic measurements using a vibrating sample magnetometer (VSM) and dielectric analysis along with ferroelectric measurements. XRD patterns obtained at room temperature revealed that the obtained samples are single-phase materials. The crystallite size showed a decrease from 46 to 24.58 nm and the unit cell volume was found to increase following Vegard’s law. The increase in tolerance factor from 0.855 to 0.908 was reported for increasing doping concentrations. The FESEM and SEM micrographs indicate that the particles are rhombohedral-hexagonal in shape. The EDS results confirm the presence of the desired elements Ba, Bi, Fe, and O and the proportionate composition of various elements present as well. The room temperature M–H curve and the M–H curve at 3 K also confirm the enhancement in magnetization with increasing doping concentration. The room temperature dielectric measurements reveal the improving resistivity of the samples with increasing doping concentrations. The increasing grain resistance as revealed by the Cole-Cole plots indicate the decreasing conductivity of doped BFO samples. The P–E measurements confirm the ferroelectric nature of the material.

One-dimensional (1D) zinc oxide (ZnO) nanostructures (NSs) as nanowires (NWs) and columnar nanoflakes (NFs) were prepared by atmospheric pressure chemical vapor deposition (APCVD) system. The effect of different thermal treatment times (0, 1, 2, and 3 h) on the physical properties of the grown ZnO NWs was methodically investigated. Further, the surface morphology of such 1D ZnO NSs was studied under different substrates (glass and silicon (Si)). The samples revealed that the synthesized ZnO NWs strongly depended on the thermal treatment time. Prepared samples were well characterized using ultraviolet visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and energy-dispersive X-ray (EDX) spectroscopy. The optical band gap (E_g) widened from 3.2 to 3.3 eV as the thermal treatment time increased and the transmittance of the NWs improved to approximately 75%, accompanied by a blue-shift at the UV absorption edge. FTIR results disclosed that ZnO absorption bands in the region between 445.5 and 478.3 cm^–1 have appeared from interatomic vibrations owing to the stretching of the Zn–O bond. XRD findings of the studied samples disclosed the polycrystalline hexagonal wurtzite structure with preferred orientation along the c-axis. According to the FESEM images, the morphological transition of the hierarchical ZnO NWs to individual NWs architectures was accomplished by increasing the treatment time from 0 to 3 h. Also, FESEM images indicated that the substrate type played a crucial role in determining the morphologies of 1D ZnO NSs. EDX outcomes showed a little Zn deficiency in the prepared samples with slightly different stoichiometric ratios between Zn and O atoms. Our current work could form the foundation for fabricating future nano-optoelectronic devices.

Nowadays, the identification of hepatotoxic compounds is necessary for clinical diagnosis as well as quantity management of their pharmaceutical formulations. In this study, silver oxide modified glassy carbon electrode synthesized using leaf extract of Ocimum tenuiflorum is adopted for sensing of (N-(4-hydroxyphenyl)acetamide). This drug molecules has regularly used pain killer that might cause liver injury under specific conditions. In addition, their physiochemical properties of bio-synthesized AgO nanoparticles have been examined with appropriate characterization techniques. Crystalline characteristic of AgO was non-destructively examined by the XRD-structural analysis. Structural examination claimed that the bioconstitutents of Ocimum tenuiflorum was effectively governs silver oxide formations from metal ions. The FT-IR vibrational assignments illustrate the AgO nanoparticles surface was influenced by some of the phytocompounds. Moreover, the overall particle’s uniformity and their distribution has been considerably controlled by the biomolecules. When oxidizing (N-(4-hydroxyphenyl)acetamide) in 0.1 M H₂SO₄, AgO NPs demonstrated superior electrocatalytic activity compared to bare SPE, and the separated oxidation peak potentials permitted simultaneous detection of the targets with broad linear ranges from 5 × 10^–6 to 3.4 × 10^–6 mol L^–1 low detection limit 8.5 × 10^–6 mol L^–1, and outstanding precision and accuracy (S/N = 3). The approach has been effectively used to identify ACOP in pharmaceutical pills because AgO nanoparticles demonstrate good stability, reproducibility, and repeatability.

“Stretching” and “shearing” are two basic types of depriving neutral matter from a solid. In principle, depriving charged matter from a solid also have similar counterparts. By now, most investigations on electron emission, which is a typical example of depriving charged matter, from a solid are focused on the “stretching” type while another type is rarely considered. The purpose of this work is to explore the possibility and feasibility of another type of depriving charged matter from a solid. Based on quantum many-body theory, this work reveals a feasible technique route of “shearing” electrons from the surface of a metal. Exchange potential among surface electrons can significantly modify dispersion relation curve of the surface 2D band and hence its electronic structure. Flatten dispersion relation curve near the highest occupied state enables a small scalar potential perturbation (at eV-level) to induce a large increment in parallel-to-surface momentum (hbar {{k}_{{||}}}) as well as that in kinetic energy (KE) (at tens eV-level). Such a high KE is sufficiently to warrant emitted electrons to surpass, rather than tunnel, barrier in vacuum. This can be achieved even for external DC fields at very low strengthes such as 1 V/mm level and 10^–4 Tesla-level. Independence of high-voltage component/element implies a broad application prospect of this phenomenon, especially as an electron source. Targeted designing electrodes enables such a route to yield a practical electron emission source.