Two-dimensional (2D) materials like arsenene and Al2S3 hold promise for optoelectronics but are limited by wide bandgaps and large exciton binding energies. Here, we design an Arsenene/Al2S3 van der Waals heterostructure and systematically investigate its stability, electronic structure, and optoelectronic properties via first-principles calculations. Our results reveal that the heterostructure exhibits high stability and forms a typical type-II band alignment, which facilitates effective spatial separation of photogenerated carriers. Remarkably, the heterostructure possesses a reduced band gap of 0.81 eV, a high hole mobility reaching the order of ∼104 cm2 V−1 s−1. This mobility value originates from an ideal acoustic deformation-potential model and serves only as a theoretical upper limit rather than a practical device transport parameter, and a significantly decreased exciton binding energy of 310 meV, substantially lower than those of the isolated monolayers. Moreover, the heterostructure demonstrates strong optical absorption across both the visible and ultraviolet regions. These properties position the arsenene/Al2S3 heterostructure as a promising candidate for high-performance optoelectronic applications.
Molecular dynamics simulations are performed to investigate the impact of irradiation-induced point defects on the uniaxial tensile mechanical properties of single-crystal aluminum nitride (AlN). Cascade collision simulations reveal that the number of point defects increases linearly with primary knock-on atom (PKA) energy. Within the PKA energy range of 1–4 keV, the defect recombination rate exceeds 98%, demonstrating that AlN possesses excellent radiation resistance. Tensile simulations show that unirradiated AlN exhibits homogeneous fracture, with cracks propagating obliquely along the [21‾1‾0] orientation at approximately 60° to the tensile direction [12‾10]. At a PKA energy of 1 keV, corresponding to the formation of one Frenkel pair (FP), cracks initiate at the defect center and propagate along [21‾1‾0], accompanied by secondary cracks along [101‾0], yielding a fracture mode similar to unirradiated AlN. A critical transition occurs when the number of FPs reaches or exceeds three: the crack propagation path becomes more concentrated and localized, extending rapidly along the single [101‾0] direction until penetrating the entire workpiece. Irradiation-induced point defects reduce both the tensile strength and fracture strain. As the number of FPs increases from 0 to 7, the tensile strength decreases from 24.38 to 19.55 GPa, while the fracture strain drops from 0.236 to 0.134. In-depth analysis reveals that point defects trigger localized stress concentration, altering the atomic displacement vector field and modulating crack propagation paths, ultimately reducing the deformation capacity and accelerating brittle fracture. This study provides a theoretical guidance for evaluating mechanical properties and designing irradiation-resistant AlN under irradiated environments.
Experimental observations have shown that during Czochralski β-Ga2O3 crystal growth, the shape of the crystal-melt (CM) interface shifts from convex curvature to concave towards the melt, and this transformation is associated with the emergence of spiral structures. This study employs numerical methods to explore the effects of RF-coil position, crystal rotation and absorption coefficient on the CM interface during β-Ga2O3 crystal growth. The RF-coil position determines the heat distribution within the crucible, thereby controlling the temperature field and melt flow pattern, and shaping the CM interface. In the early stages of growth, placing the RF-coil center near the melt-depth center creates a convex CM interface towards the melt; lowering it makes the interface concave. Crystals with lower absorption coefficients exhibit more pronounced convexity due to enhanced thermal radiation from the crystal interior to the surface. Higher rotation rates lead to the formation of vortices below the CM interface, which transfer heat upward from the crucible bottom to the interface, reducing the convexity. Adjusting the position of the RF-coil or the rotation rate accelerates the convex to concave transition in high-absorption-coefficient crystals. As the crystal grows in length, the size and intensity of the rotation-induced vortex increase, eventually causing the interface to become concave. The convex-to-concave CM interface transition occurs more quickly in high-absorption-coefficient crystals. The present findings are consistent with the growth conditions under which the spiral structures appear in the experiments. These results can provide practical guidance for the positioning and rotation rate selection of RF coils during β-Ga2O3 crystal growth, in order to delay the emergence of spiral structures.
The influence of sputtering pressure on the structural and electrical properties of In–Ga–Zn–O (IGZO) thin films deposited by high-power pulsed magnetron sputtering (HPPMS) was systematically investigated. By controlling the deposition pressure between 0.65 and 3.0 Pa, the plasma characteristics during HPPMS deposition were significantly modified. Optical emission spectroscopy revealed that lower pressures increased the relative contribution of emissions from ionized species, suggesting enhanced plasma activity during film growth. Despite substrate temperatures remaining below 70 °C throughout deposition, X-ray diffraction analysis showed the emergence of structurally ordered and partially crystallized IGZO phases within an optimized pressure region around 1.5 Pa. X-ray photoelectron spectroscopy further demonstrated that the optimized growth condition promoted metal-oxygen bonding while reducing the higher-binding-energy O 1s component associated with oxygen-deficient bonding environments. Following post-deposition annealing, IGZO thin-film transistors fabricated from films deposited at 1.5 Pa exhibited the smallest subthreshold swing among all investigated conditions. These improvements are associated with enhanced structural ordering and reduced defect density resulting from pressure-controlled film growth. The present results demonstrate that sputtering pressure plays a critical role in governing the structural evolution of IGZO thin films during HPPMS deposition and provide further insight into pressure-controlled growth behavior under low-temperature deposition conditions.
