Enhanced visible-light-driven photocatalytic activity in SiPGaS/arsenene-based van der Waals heterostructures.

Van der Waals heterostructures (vdWHs) showcase robust and tunable light-matter interactions, establishing an intriguing realm for investigating atomic-scale photocatalytic properties. Here, we employ ab initio methods to study the photocatalytic and optical properties of semiconducting SiPGaS/arsenene-based vdWHs with a type-II band alignment. Across the heterointerfaces, there exists significant built-in electric fields and large potential drop, in turn facilitating the spatial separation of photo-generated electron-hole pairs. These vdWHs further possess high carrier mobility in the order of 102 cm2V⁻1S⁻1, which combining with appropriate band edge positions, endow the vdWHs an absorption coefficient of ∼105 cm⁻1 to harvest a maximal portion of the solar spectrum for visible-light-driven photocatalytic applications. Our findings also reveal transition of the type-II band alignment in a type-III configuration via compressive strain for tunneling field-effect transistor application. Furthermore, both types of vdWHs exhibit enhanced suitability for photocatalysis under conditions with a pH of 2.

Nanopore-Patterned CuSe Drives the Realization of the PbSe-CuSe Lateral Heterostructure.

Monolayer PbSe has been predicted to be a two-dimensional (2D) topological crystalline insulator (TCI) with crystalline symmetry-protected Dirac-cone-like edge states. Recently, few-layered epitaxial PbSe has been grown on the SrTiO3 substrate successfully, but the corresponding signature of the TCI was only observed for films not thinner than seven monolayers, largely due to interfacial strain. Here, we demonstrate a two-step method based on molecular beam epitaxy for the growth of the PbSe-CuSe lateral heterostructure on the Cu(111) substrate, in which we observe a nanopore-patterned CuSe layer that acts as the template for lateral epitaxial growth of PbSe. This further results in a PbSe-CuSe lateral heterostructure with an atomically sharp interface. Scanning tunneling microscopy and spectroscopy measurements reveal a fourfold symmetric square lattice of such PbSe with a quasi-particle band gap of 1.8 eV, a value highly comparable with the theoretical value of freestanding PbSe. The weak monolayer-substrate interaction is further supported by both density functional theory (DFT) and projected crystal orbital Hamilton population, with the former predicting the monolayer's anti-bond state to reside below the Fermi level. Our work demonstrates a practical strategy to fabricate a high-quality in-plane heterostructure, involving a monolayer TCI, which is viable for further exploration of the topology-derived quantum physics and phenomena in the monolayer limit.