A remarkable refinement in the optical behavior of two-dimensional transition metal dichalcogenides (TMDs) has been brought to light when cleaved from their respective bulks. These atomically thin direct bandgap semiconductors are highly responsive to optical energy which proposes the route for futuristic photonic devices. In this manuscript, we have substantially focused on the optical study of MoS₂ and WS₂ nanosheets and comparative analysis with their bulk counterparts. The synthesis of nanosheets has been accomplished with liquid exfoliation followed by fabrication of thin films with drop-casting technique. X-ray diffraction and field emission scanning electron microscopy affirmed the morphology, whereas, UV–visible spectroscopy served as the primary tool for optical analysis. It was observed that several parameters, like optical conductivity, optical band-gap energy etc. have enhanced statistics in the case of exfoliated nanosheets as compared to their respective bulks. Some researchers have touched upon this analysis for MoS₂, but it is completely novel for WS₂. We expect our work to clearly distinguish between the optical behaviors of nanoscale and bulk TMDs so as to intensify and strengthen the research related to 2D-layered materials for optoelectronic and photovoltaic applications.

The optimization of a SiO₂/TiO₂, SiO₂/ZnS double layer antireflection coating (ARC) on Ga_0.5In_0.5P/In_0.02Ga_0.98As/Ge solar cells for terrestrial application is discussed. The Al_0.5In_0.5P window layer thickness is also taken into consideration. It is shown that the optimal parameters of double layer ARC vary with the thickness of the window layer.

Based on the first-principles pseudopotentials and the plane wave energy band method, the supercells of perfect crystal 4H-SiC and those with intrinsic defects V_C, V_Si, V_C-C and V_C-Si were calculated. Ignoring the atomic relaxations, the results show that the formation energy of intrinsic defects is ranked, from low to high, as V_C, V_C-C, V_Si to V_Si-Si at 0 K. The equilibrium concentration of each intrinsic defect can be deduced from the formation energy of each intrinsic defect. The concentration ranks, from high to low, as V_C, V_C-C, V_Si, V_Si-Si, which is in accordance with the ESR and PL results. The stabilizing process of metastable defects V_Si converting to V_C-C was explained by formation energy.

This paper reviewed the advances in fluorescent SiC codoped with nitrogen, boron and aluminum dopants applied to optoelectronics in recent years. The progress aspects in research of the fluorescent property, recombination theory, experiment, and construction design were discussed. The advantages that fluorescent SiC based white LEDs compared with conventional white LEDs were analyzed. It was confirmed that fluorescent SiC is a promising material to replace phosphor in the luminous field. Finally, the problems in the study of fluorescent 4H-SiC were pointed out.

We investigate the dispersion properties of nanometer-scaled silicon nitride suspended membrane waveguides around the communication wavelength and systematically study their relationship with the key structural parameters of the waveguide. The simulation results show that a suspended membrane waveguide can realize anomalous dispersion with a relatively thinner silicon nitride thickness in the range of 400 to 600 nm, whereas, for the same membrane thickness, a conventional rib or strip silicon nitride waveguide cannot support anomalous dispersion. In particular, a waveguide with 400 nm silicon nitride thickness and deep etch depth (r=0.05) exhibits anomalous dispersion around the communication wavelength when the waveguide width ranges from 990 to 1255 nm, and the maximum dispersion is 22.56 ps/(nm·km). This specially designed anomalous dispersion silicon nitride waveguide is highly desirable for micro-resonator based optical frequency combs due to its potential to meet the phase-matching condition required for cascaded four-wave-mixing.

Compared to the conventional phase change materials, the new phase change material Ta-Sb₂Te₃ has the advantages of excellent data retention and good material stability. In this letter, the etching characteristics of Ta-Sb₂Te₃ were studied by using CF₄/Ar. The results showed that when CF₄/Ar = 25/25, the etching power was 600 W and the etching pressure was 2.5 Pa, the etching speed was up to 61 nm/min. The etching pattern of Ta-Sb₂Te₃ film had a smooth side wall and good perpendicularity (close to 90°), smooth surface of the etching (RMS was 0.51nm), and the etching uniformity was fine. Furthermore, the mechanism of this etching process was analyzed by X-ray photoelectron spectroscopy (XPS). The main damage mechanism of ICP etching in CF4/Ar was studied by X-ray diffraction (XRD).

The unique structure and exceptional properties of two-dimensional (2D) materials offer significant potential for transformative advancements in semiconductor industry. Similar to the reliance on wafer-scale single-crystal ingots for silicon-based chips, practical applications of 2D materials at the chip level need large-scale, high-quality production of 2D single crystals. Over the past two decades, the size of 2D single-crystals has been improved to wafer or meter scale, where the nucleation control during the growth process is particularly important. Therefore, it is essential to conduct a comprehensive review of nucleation control to gain fundamental insights into the growth of 2D single-crystal materials. This review mainly focuses on two aspects: controlling nucleation density to enable the growth from a single nucleus, and controlling nucleation position to achieve the unidirectionally aligned islands and subsequent seamless stitching. Finally, we provide an overview and forecast of the strategic pathways for emerging 2D materials.

Owing to the conductivity modulation of silicon carbide (SiC) bipolar devices, n-channel insulated gate bipolar transistors (n-IGBTs) have a significant advantage over metal oxide semiconductor field effect transistors (MOSFETs) in ultra high voltage (UHV) applications. In this paper, backside grinding and laser annealing process were carried out to fabricate 4H-SiC n-IGBTs. The thickness of a drift layer was 120 μm, which was designed for a blocking voltage of 13 kV. The n-IGBTs carried a collector current density of 24 A/cm² at a power dissipation of 300 W/cm² when the gate voltage was 20 V, with a differential specific on-resistance of 140 mΩ·cm².

Based on first-principle calculations, the electronic structures and optical properties of a single-walled (7, 0) SiC nanotube (SiCNT) with a carbon vacancy defect or a silicon vacancy defect are investigated. In the three silicon atoms around the carbon vacancy, two atoms form a stable bond and the other is a dangling bond. A similar structure is found in the nanotube with a silicon vacancy. A carbon vacancy results in a defect level near the top of the valence band, while a silicon vacancy leads to the formation of three defect levels in the band gap of the nanotube. Transitions between defect levels and energy levels near the bottom of the conduction band have a close relationship with the formation of the novel dielectric peaks in the lower energy range of the dielectric function.

Yttrium-doped IZO (YIZO) thin films with different thickness have been prepared on soda-lime glass (SLG) and P-Si substrates by radio frequency magnetron sputtering at room temperature. Structural morphology and optical properties of the films have been investigated. YIZO thin film transistors (TFTs) with the bottom-gate-structure are fabricated on P-Si substrates. The output and transfer characteristics of YIZO-TFT have been studied. It has been found that all YIZO thin films prepared at room temperature are amorphous, and the YIZO TFTs exhibit n-channel depletion mode. YIZO-TFT with active layer thickness of 20 nm shows an on/off ratio over 10⁵, a sub-threshold swing of 2.20 V/decade at a low operating voltage of -1.0 V, and saturation mobility values over 0.57 cm²/(V· s).