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In recent years, the lead-free double perovskite Cs2AgBiBr6 has emerged as an appealing alternative to lead-based perovskites due to its nontoxicity and long-term stability. In this study, we employed methyl acetate as an antisolvent and prepared high-quality Cs2AgBiBr6 films by a facile one-step spin-coating method. The prepared films exhibited excellent crystallinity with densely packed crystal grains. The root mean square roughness and average roughness of the obtained Cs2AgBiBr6 perovskite films were 6.69 and 5.43 nm, respectively. Furthermore, the memory device based on the Cs2AgBiBr6 perovskite films exhibited uniform and repeatable bipolar resistive switching performance with an ON/OFF ratio of 15, an endurance of 80 cycles, and a retention time of 104 s. This work showcases a simple and convenient one-step spin-coating method for depositing high-quality Cs2AgBiBr6 thin films while highlighting their potential application in resistive switching memories based on lead-free double perovskites. [ABSTRACT FROM AUTHOR]

Previous studies have found that pure even harmonics are generated from oriented CO molecules in linearly polarized laser fields. In this work, we demonstrate multi-directions pure even harmonic simultaneous generation from planar molecules in linearly polarized laser fields using the time-dependent density-functional theory. The analysis reveals that pure even harmonic generation depends on the special symmetry of the planar molecule. In the linearly polarized laser field, it is found that only when the planar molecules have reflective symmetry direction and the molecules perpendicular to the reflective symmetry direction do not have reflection symmetry can the planar molecules generate pure even harmonics along such reflective symmetry direction. When the laser polarization is perpendicular to the planar molecule, if the molecule has several these directions of such reflection symmetry, pure even harmonics will be simultaneously generated along these symmetrical directions. Moreover, when the laser polarization is along the molecular plane and perpendicular to the direction of one such reflection symmetry, even harmonic is also generated along this reflection symmetry direction, whereas odd harmonic is generated along the direction of laser polarization. The phenomenon exists in all polyatomic planar molecules with such reflection symmetry. [ABSTRACT FROM AUTHOR]

In sodium nanoring dimers, plasmon resonances and the plasmon-induced field enhancement are investigated by time-dependent density functional theory. The optical absorption, the induced charge response, and the frequency dependent current demonstrate that the main plasmon resonance modes are the charge transfer plasmon mode and the bonding dimer plasmon mode (BDP). Moreover, there are also two small hybridized plasmon modes. The induced field enhancement of each spatial region depends on the gap distance and the plasmon mode. For the narrow gap, the field enhancement at different positions of the straight line segments between two nanorings is almost uniformly distributed. However, for large separations, along the axial direction, the field enhancement gradually decreases in the region within the radius of the sodium atom. Then, the change of the field enhancement is nonlinear. For different plasmon modes, there is a different number of field enhancement extrema. The largest extreme value is located in the middle region. These findings are expected to play an important role in designing plasmonic nanostructures for practical applications that require coupled metallic nanoparticles with enhanced electric fields. [ABSTRACT FROM AUTHOR]