We report the preparation of aand k-phase In 2 Se 3 nanowires by thermal evaporation and investigation of their phase transformations in situ by synchrotron radiation X-ray diffraction (XRD) during a thermal annealing process. The k-phase transformed into the a-phase at 500 C and eventually transformed to high temperature a-phase with a layered structure of 5 atoms-5 atoms at 700 C irreversibly. Different atomistic structures of In 2 Se 3 were modeled and optimized by DFT, which correlate well with the XRD results. The In 2 Se 3 nanowires also exhibit a large difference in resistivity before and after annealing.

No abstract

The combination of graphene (GR) and monolayer MoSi2N4 has attracted much attention; however, the comprehension of its electrical contact modulation is still not fully explored. Herein, the influence of the interlayer spacing and external electric field on the interfacial characteristic and electronic structure of the GR/MoSi2N4 heterojunction was systematically investigated using first-principles calculations. It is found that a stable van der Waals heterojunction forms when GR incorporates on the MoSi2N4 sheets. The results indicate that both the type and height of the Schottky barrier could be tuned by altering the interlayer spacing between GR and MoSi2N4 sheets or applying a vertical external electric field on the GR/MoSi2N4 heterojunction. Noteworthily, the Schottky barrier height markedly changes about 0.2–0.3 eV with the increase of external electric field per 0.1 V·Å–1. It is confirmed that the change of energy bands is caused by the charge redistribution with the interlayer spacing and external electric field. These findings will provide rational evidence for the design of next-generation field-effect transistors.

Hunting for high-performance photocatalysts to achieve efficient solar conversion is still far from ideal goals. Here, a kind of Janus structure, ASSiN2 (A = Cr, Mo, W) monolayers, is first proposed to explore their photocatalytic activity using the first-principles calculations. It is found that the Janus ASSiN2 monolayers are structurally stable and exhibit semiconductor behaviors with indirect bandgaps of 1.47, 2.86, and 3.02 eV, respectively. According to the comprehensive analysis of charge density difference, it is confirmed that an enhanced intrinsic electric field exists in the Janus structures, which could facilitate the separation of photogenerated carriers. Noteworthily, only the band-edge potentials of the WSSiN2 monolayer fully satisfy the redox conditions of photocatalytic water splitting. Meanwhile, the high electron mobility up to 1098.36 cm2·V–1·s–1 and strong visible-light absorption ability can be obtained in the WSSiN2 monolayer, indicating its great application potential in photocatalysis. The findings will offer reliable evidence for further developing 2D Janus materials as high-performance photocatalysts.