Programmed Band Gap Modulation within van der Waals Semiconductor Monolayers by Metalorganic Vapor-Phase Epitaxy

Abstract

Programmed alloying within a van der Waals (vdW) semiconductor monolayer (ML) is achieved by metalorganic vapor-phase epitaxy. Specifically, two versions of on-ML alloying are demonstrated by pre-cise controls of time-lapse vapor pressures during the single-crystalline WS2xSe2(1-x) ML growth, where the alloying degree, x is either continuously or discretely directed on the MLs in the entire range of 0 ≤ x ≤ 1. With that, on-ML band-gap modulation is accomplished in the forms of either graded or discrete intra-ML junctions, leading to atomically thin multispectral photodetectors by a spatially resolved manner at the nanoscales.