Nanomaterials

First-principles FP-LAPW calculations were used to investigate the structural, mechanical, electronic, optical, and thermoelectric properties of the double halide perovskites Rb₂NaTaBr₆ and Rb₂LiTaBr₆. Structural optimization confirmed their stable cubic phase. Elastic analysis shows they are mechanically stable, ductile, and anisotropic. Spin-polarized calculations reveal that both compounds are half-metallic ferromagnets with an integer total magnetic moment of 2 μB per formula unit, dominated by the Ta-d states. They exhibit strong dielectric response and strong UV light absorption originating from interband electronic transitions, despite their intrinsic metallic ground state. Boltzmann transport theory revealed a temperature-dependent enhancement of electrical conductivity and power factor. Both materials, especially Rb₂LiTaBr₆, show promise for high-temperature thermoelectric and UV optoelectronic applications.

Access to clean and safe water remains a major environmental challenge due to the increasing release of organic pollutants, dyes, nutrients, microorganisms, and persistent contaminants into aquatic environments [...]

Maintaining low leakage current with high capacitance density in metal–insulator–metal (MIM) capacitors is essential for next-generation dynamic random-access memory (DRAM) scaling. Rutile TiO₂ is a promising high-k dielectric; however, its narrow bandgap causes high leakage, while defect-free stabilization in ultrathin films remains challenging. RuO₂/TiO₂/Ru MIM capacitors were fabricated using a reactive direct current (DC)-sputtered RuO₂ bottom electrode, followed by TiO₂ growth by direct plasma atomic layer deposition (DP-ALD) or remote plasma atomic layer deposition (RP-ALD) and rapid thermal annealing in O₂ to reduce defects. Rutile TiO₂ was deposited directly on highly crystalline RuO₂ under both plasma modes, suggesting that RuO₂ crystallinity governs TiO₂ phase evolution. The RP-ALD film replicated the RuO₂ grain morphology, yielding higher roughness than that of the DP-ALD film. Moreover, the RP-ALD film exhibited lower oxygen-vacancy density and improved stoichiometric stability. The RP-ALD-fabricated capacitors exhibited a higher dielectric constant and lower leakage current density at 0.8 V than the DP-ALD-fabricated capacitors (~100 and ~1.76 × 10⁻⁶ A/cm² vs. ~97 and ~1.41 × 10⁻⁴ A/cm², respectively). Ion bombardment during DP-ALD likely promoted oxygen-vacancy-related defect formation, whereas RP-ALD mitigated such damage, improving leakage characteristics. This work highlights the potential of RP-ALD-based RuO₂/TiO₂/Ru MIM capacitors for next-generation DRAM.