Physics of the Solid State最新文献

In recent years, two of the most pressing problems in the world have become the rising need for energy and the degradation of the environment. Industrialization’s discharge of organic and metal ion waste into water systems has created a critical demand for efficient removal and degradation of organic waste. Due to their superior optical and electrical properties, semiconductors like metal oxides and mixed metal oxides have attracted a lot of attention for photocatalysis. The majority of these semiconductors, however, lack the ideal band alignment necessary for effective sun/solar light absorption. FeVO₄ can be a useful tool for band tuning for visible light photocatalysis in order to get around this problem. Many attempts have been made over the years to increase FeVO₄’s photocatalytic performance. It has been postulated and put into practice that a number of different modification strategies, including element doping and composite fabrication, can be utilized to increase the efficiency of photocatalysts based on FeVO₄. The photocatalytic degradation of harmful organic pollutants by various metal- and non-metal-doped FeVO₄-based materials is highlighted in this review paper. In recent years, significant progress has been made in understanding the core problems and creating effective photocatalysts.

In this article we have studied, using the Scanning Electron Microscopy SEM LEO 440, the surface electrical properties of MgO (111) irradiated with 30 keV electrons. The study of the evolution of the secondary electronic emission of MgO (111) shows that (ln sigma ) increases and reaches a value lower than zero. After an injection of 5000 pC, we observe a pseudo mirror, which is due to a very negative surface potential. Finally, we have shown the very high stability of charges within MgO (111) thanks to the use of Atomic Force Microscopy coupled with Scanning Electron Microscope. We can then conclude that MgO (111) is a good trapping insulator.

Hematite (α-Fe₂O₃) has received a lot of attention and has potential use in a variety of applications such as energy storage and photovoltaic solar cells despite its short diffusion length and extremely low conductivity. A possible strategy to enhance its structural and optoelectronic properties is element doping. In this work, we report on the successful preparation of α-Fe₂O₃ nanorods thin film via a simple low-cost hydrothermal process, and the crucial effect of yttrium doping. We analyzed the effects of Y-doping of α-Fe₂O₃ by varying the amount of yttrium 1, 3, 5, and 8 at %. The optical study revealed that Y-doping reduces the optical band gap, with a shift from 2.11 eV for pure hematite NRs films to 1.94 eV for 5 at % Y-doped NRs. Our study proved that Y-doping obviously reduced the recombination activities in α-Fe₂O₃ as demonstrated by the photoluminescence study. Amongst all doped α-Fe₂O₃ NRs films with different Y dopant concentration, the 5 at % exhibited best structural and optoelectronic properties with the highest photocurrent density and incident photon to current efficiency (IPCE). The photocurrent density was increased from 0.25 (undoped) to 1.25 mA/cm² in the doped NRs with 5 at % Y content at 0.4 V vs. (Ag/AgCl) under illumination, which is 5 times higher than that measured in the pristine α-Fe₂O₃. The high photo-response of Y-doped NRs in the visible range suggests that the grown NRs thin films are excellent candidates for optoelectronic applications, particularly in solar cells and large light-harvesting devices.

The elaboration and characterization of transparent electrodes of ZnO:Al type (aluminum-doped zinc oxide) are crucial steps in the development of organic photovoltaic cells (OPV) due to their essential role in collecting the current generated by the organic active layer. In this work, we have make realization and electrically characterized of transparent electrodes based on ZnO at various doping levels of Al. Subsequently, we created different metal-semiconductor polymer junctions (PV cells) and determined their I(V) characteristics in both darkness and under illumination.

The surface modification to nanodiamond (ND) powder was performed through air oxidation to avoid the nanoscale particle aggregation of suspension. The ND powders treated for varied oxidation duration were analyzed by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and laser particle size analysis. The results show that the best effect was achieved when the ND powder was subjected to air oxidation at 450°C for 12 h. A ND suspension was prepared using the ND powder oxidized in air for 12 h, resulting in an average particle size of 11.8 nm. This ND suspension was then used for seed crystal formation on silicon substrates via ultrasonic treatment, with a seeding density of 10¹¹ achieved.

Electronic, optical, and photocatalytic characteristics of monolayer bismuthene nanosheets have been investigated as a function of their sizes. It is shown that bismuthene nanosheet photocatalytic characteristics are comparable with the currently available high-ranked photocatalysts. The mentioned characteristics are enhanced by the extension of nanosheet along both edges. The nonlinear optics (NLO) analysis for a variety of nanosheet sizes displays a wide range of absorption on the solar spectrum. This would be another fascinating characteristic of water-splitting. The stability of the bismuthene nanosheet falls by widening the nanosheet from both sides of armchair and zigzag edges. The dependency of the energy gap of HOMO and LUMO levels regarding the nanosheet size along either of armchair and zigzag boundaries has been investigated up to 388 atoms. Regions of chemical activity in bismuthene are mainly focused in the middle of nanosheets. This means that either of armchair and zigzag edges in bismuthene nanosheet demonstrate a negligible chemically activity.

The magnesium doped yttrium barium zirconate, YBa₂Zr_3 – xMg_xO_9.5 – δ (0 ≤ x ≤ 0.5) has been prepared by the standard solid-state reaction method and the room temperature X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), particle size analysis (PSA) and thermogravimetric analysis (TGA) have been investigated for phase purity, structural and thermal characterizations. The XRD data of the materials have been indexed with the winXpow software and Rietveld refinements have been done by FullProf suite programarend is found to be double phase of cubic perovskite and a small amount of cubic fluorite. The microstructural parameters such as size, stress, strain, crystal energy are obtained from XRD line broadening data using different models and found that the cubic perovskite phase contributed a large part to the solid solution shows a larger crystallite size of ~212 nm (±13 nm) than its fluorite counterpart which is found to be ~132 nm (±1 nm). The TEM analyses confirm the presence of both phases. The TGA scans in nitrogen environment exhibits stability up to 1000°C. The sizes of the particles from 9 to 13 μm. Scanning electron microscope images reveals that the materials sintered at 1450°C are porous.

In this article, magnetic nanocomposite photocatalysts based on carbon nanotubes, coated with cobalt ferrite and zinc oxide were prepared using hydrothermal synthesis method. Then, their physical and chemical properties have been investigated using various techniques such as X-ray diffraction, scanning electron microscope, vibrating sample magnetometer and visible-ultraviolet spectroscopic analysis (UV-Vis). In the next step, the photocatalytic activity of the prepared photocatalysts for the removal of toxic dyes under visible light has been investigated. For this purpose, toxic dyes have been removed in the presence of photocatalyst and visible light under specific experimental conditions. It was found that under visible light, longer time is required, but under UV analysis, they degrade within 60 min. Then, using techniques such as UV electron absorption spectroscopy, the extent of dye removal has been measured. The results show that the magnetic nanocomposite photocatalysts based on carbon nanotubes, coated with cobalt ferrite and zinc oxide have high photocatalytic activity for the removal of toxic dyes under visible light. Also, the results show that coating the carbon nanotube with cobalt ferrite has a significant improvement in photocatalytic activity and increasing the amount of cobalt ferrite shows a substantial perfection in the removal of toxic dyes. Also, the magnetic nature of the prepared photocatalysts allows their easy recovery after use.

We investigated the phonon and thermal properties of the silicon- and germanium-nanowires, covered by Si_xGe_1–x, plastic, diamond and SiO₂ shells as well as Si-based segmented nanowires, consisting of segments of different sizes and/or materials. Acoustic phonon energies were calculated in the framework of the face-centered cubic cell model of the lattice vibrations, while thermal conductivity was investigated in the framework of Boltzmann transport equation approach within the relaxation time approximation. It was shown, that claddings with higher (lower) sound velocity strongly affect the phonon energy spectra and increase (decrease) the average phonon group velocity in core nanowire. It was demonstrated, that redistribution of the phonon modes in Si/Ge and Si/SiO₂ segmented nanowires leads to a localization of the great amount of the phonon modes in nanowire segments, resulting in exclusion of such modes from the heat flow and suppression of the phonon thermal conduction (by a factor of 2–8) in comparison with generic silicon nanowires. Low values of the thermal conductivity of segmented nanowires make them prospective for thermoelectric and thermoinsulating applications.

This study investigated the structural, mechanical, piezoelectric, and electromechanical properties of AlScN thin films using density functional theory (DFT) under varying levels of applied pressure, ranging from 0 to 20 GPa. The primary focus of this research is to explore the feasibility of optimizing AlScN thin films for surface acoustic wave (SAW) applications through pressure-induced modifications. Our findings reveal two significant outcomes. First, we observe a notable increase in the elastic constant C₃₃ as a function of pressure. This increase signifies a substantial enhancement in material stiffness, directly influencing wave propagation and velocity within the thin films. Second, a remarkable 68% improvement in the piezoelectric constant, d₃₃, is identified for Al_0.75Sc_0.25N at an applied pressure of 20 GPa compared to Al_0.75Sc_0.25N at 0 GPa. This enhancement has a profound impact on the electromechanical coupling characteristics of the material. These results underscore the potential for tuning the piezoelectric response of AlScN thin films using applied pressure, offering a promising avenue for enhancing the performance of SAW-based AlScN devices.