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The first-principles electronic structure calculation was applied to investigate the electronic properties of the LaAlO 3 /SrTiO 3 (001) heterostructure system (HSs) under strain. The results show that the distorted structure at the interface determines the occupied orbitals of 2DEG, further resulting in different sensitivities of interfacial charge carrier density, electron effective mass, electron mobility, and electrical conductivity on strain. The interfacial metallic states of tensile-strained and biaxial-compressive-strained LaAlO 3 /SrTiO 3 (001) HSs mainly occupy Ti 3d x y orbitals, which is the same for unstrained HSs. Then, the electron effective mass slightly decreases with tensile strain, which leads to a higher electrical conductivity. Different from biaxial-compressive-strained LaAlO 3 /SrTiO 3 (001) HSs with Ti 3d x y occupied orbitals, the Ti 3d y z orbitals are occupied for uniaxial-compressive-strained HSs, thus leading to a remarkably increased electron effective mass and sharply decreased electrical conductivity. These results give us a guidance to effectively modify the interfacial electronic characteristics of LaAlO 3 /SrTiO 3 (001) HSs by strain. [ABSTRACT FROM AUTHOR]

BaSnO3 thin films have attracted significant attention due to their exceptional properties, specifically high electron mobility at room temperature, for optoelectronic applications, such as pn diodes and field-effect transistors. However, the dominant surface terminations of these films, particularly their dependence on growth conditions and water leaching, remain elusive. Here, we studied the impacts of growth conditions and water leaching on the dominant surface terminations of BaSnO3 thin films by modeling oxygen vacancies and water adsorption using first-principles calculations. Our calculations show that, in the BaSnO3 model without oxygen vacancies (corresponding to an oxygen-rich condition), the required cleavage energy to remove the surface SnO2 (BaO·H2O) layer is lower than that required to remove the BaO (SnO2·H2O) layer. This implies that BaSnO3 thin films subjected to O2 annealing display a Ba-excess surface without H2O leaching, whereas they have a Sn-excess surface with H2O leaching. In contrast, the calculated results for the BaSnO3 model with oxygen vacancies (corresponding to an oxygen-deficient condition) show that the required cleavage energy to remove the surface SnO2 (SnO2·H2O) layer is less than that required to remove the BaO (BaO·H2O) layer, suggesting that BaSnO3 thin films prepared under oxygen-deficient conditions should exhibit Ba-excess surfaces regardless of H2O leaching. This study offers useful insights into achieving precise control over the surface properties of BaSnO3 films. [ABSTRACT FROM AUTHOR]

Karst areas are widespread in China and can be divided into southern karst and northern karst based on the geographical boundary of Qinling Mountains and Huaihe River. In northern karst regions, karst springs are the predominant landform. Previous studies on karst springs have predominantly focused on macroscopic perspectives, such as water chemistry characteristics, with less attention given to the microscopic characteristics of springs. Therefore, this study focused on the Jinan Baotu Spring area, representative of a typical northern karst region, and investigated the natural nanoparticles present in different aquifers at various depths from a microscopic point of view. Through the observation of nanoparticle tracking analyzer (NTA), numerous nanoparticles were identified in the groundwater samples. The particle size range of the particles contained in groundwater is mainly concentrated in the range of 150–500 nm, and the particle concentration is mainly concentrated in the range of 1.5–5.0 × 105 Particles/L. The microstructure, chemical composition, and element distribution of these nanoparticles were analyzed using TEM-EDS techniques. The results unveiled the presence of Ti-bearing nanoparticles in various groundwater layers, including both crystalline and amorphous states, as well as nanoparticles exhibiting the coexistence of crystal and amorphous structures. By comparing the measured lattice spacing with PDF cards, the crystalline Ti-bearing nanoparticles were identified as rutile, brookite, anatase, ilmenite, pseudorutile, and ulvospinel. Furthermore, the main components of the amorphous Ti-bearing nanoparticles predominantly consisted of Ti or a mixture of Ti and Fe. EDS analysis further indicated that the Ti-bearing nanoparticles carried additional metal elements, such as Zn, Ca, Mn, Mo, Cr, and Ni, suggesting their potential role as carriers of metal elements during groundwater transportation. This discovery provided new insights into the migration of metal elements in groundwater and underscores the capacity of nanoparticles to enhance the mobility of inorganic substances within the water environment. Notably, brookite was detected in three different areas, including the direct discharge area, indirect recharge area, and discharge area, which may indicate that some special natural nanoparticles could serve as natural mineral tracer particles in the process of groundwater migration. [ABSTRACT FROM AUTHOR]