Hongli Zhao

Spatially isolated wavefunctions in different constituent layers of a heterostructure lead to forbidden optical transitions between the bands of the respective layers.

Precise control over the phase constitution and crystallographic orientation of thin films is vital for high‐performance electronics. Herein, a salt‐assisted atmospheric pressure chemical vapor deposition (SA‐APCVD) strategy is reported for the Sn–Se system. By employing a dual‐heating‐zone configuration and optimizing source‐to‐substrate distances, the Sn/Se molar flux at the growth front was continuously modulated. The substrate temperature ( T _s ) plays a critical role in governing the phase evolution of the as‐deposited films. At T _s ≤ 742 K, the films crystallize into a hexagonal SnSe ₂ phase with Lotgering factor ( F ₀₀₁ = 0.99), whereas a transition to (400)‐oriented orthorhombic SnSe occurs above 806 K. Furthermore, the (001) texture of SnSe ₂ can be effectively tailored by adjusting the precursor molar ratio, yielding a substantial ΔF ₀₀₁ of up to 0.29. This strategy facilitates deterministic modulation of carrier types and transport characteristics, providing a robust framework for the programmable synthesis of SnSe _x films with tailored phases and textures.

A BiVO ₄ /2D g‐C ₃ N ₄ direct dual semiconductor photocatalytic system has been fabricated via electrostatic self‐assembly method of BiVO ₄ microparticle and g‐C ₃ N ₄ nanosheet. According to experimental measurements and first‐principle calculations, the formation of built‐in electric field and the opposite band bending around the interface region in BiVO ₄ /2D g‐C ₃ N ₄ as well as the intimate contact between BiVO ₄ and 2D g‐C ₃ N ₄ will lead to high separation efficiency of charge carriers. More importantly, the intensity of bulid‐in electric field is greatly enhanced due to the ultrathin nanosheet structure of 2D g‐C ₃ N ₄ . As a result, BiVO ₄ /2D g‐C ₃ N ₄ exhibits excellent photocatalytic performance with the 93.0% Rhodamine B (RhB) removal after 40 min visible light irradiation, and the photocatalytic reaction rate is about 22.7 and 10.3 times as high as that of BiVO ₄ and 2D g‐C ₃ N ₄ , respectively. In addition, BiVO ₄ /2D g‐C ₃ N ₄ also displays enhanced photocatalytic performance in the degradation of tetracycline (TC). It is expected that this work may provide insights into the understanding the significant role of built‐in electric field in heterostructure and fabricating highly efficient direct dual semiconductor systems.

Crystal structure and electronic properties of SnO₂ doped with non-metal elements (F, S, C, B, and N) were studied using first-principles calculations. The theoretical results show that doping of non-metal elements cannot change the structure of SnO₂ but result in a slight expansion of the lattice volume. The most obvious finding from the analysis is that F-doped SnO₂ has the lowest defect binding energy. The doping with B and S introduced additional defect energy levels within the forbidden bandgap, which improved the crystal conductivity. The Fermi level shifts up due to the doping with B, F, and S, while the Fermi level of SnO₂ doped with C or N has crossed the impurity level. The Fermi level of F-doped SnO₂ is inside the conduction band, and the doped crystal possesses metallicity. The optical properties of SnO₂ crystals doped with non-metal elements were analyzed and calculated. The SnO₂ crystal doped with F had the highest reflectivity in the infrared region, and the reflectance of the crystals doped with N, C, S, and B decreased sequentially. Based on this theoretical calculations, F-doped SnO₂ is found to be the best photoelectric material for preparing low-emissivity coatings.

The crystal structure, electronic properties of F, S, C, B and N doped SnO₂ were studied with the First-Principle Method. The theoretical results show that doping of non-metal elements did not change the structure of SnO₂ but result in slight lattice volume expansion. The dope of the non-metal elements of B, F, and S cause the Fermi level to shift upThe most obvious finding to emerge from the analysis is that F-doped SnO₂ has the lowest defect binding energy, stable crystal structure, and the easiest doping. The B, F, and S element doped SnO₂ can modulate the fermi level. The doping of the B and S elements introduced additional defect energy levels to appear within the forbidden band-gap，which improved the crystal conductivity. Analysis of the energy band structure of SnO₂ crystals doped with C and N elements shows that the Fermi level has crossed the impurity level. The Fermi level of F doped SnO₂ is inside the conduction band, and the doped crystal has metallicity. The optical properties of SnO₂ crystals doped with non-metallic elements were analyzed and calculated. The SnO₂ crystal doped with F element had the highest reflectivity in the infrared region, and the reflectance of the crystals doped with N, C, S, and B elements decreased sequentially. Based on this theoretical calculations, F doped SnO₂ is found to be the best photoelectric material for for preparing low-e thin film.