Interface engineering of ferroelectricity in thin films of thiophosphate ABP 2 X 6 (A = Cu, Ag; B = In, Bi, Cr, V; and X = S, Se)
arXiv:2112.04077 · doi:10.1103/PhysRevB.104.224102
Abstract
Two-dimensional ferroelectrics (FEs) are promising in the miniaturization of memory devices with ultra-high-density data storage and low power consumption. However, many thiophosphate monolayers, i.e., analogs of CuInPS and referred to as ABPX, lose ferroelectricity and instead exhibit an antiferroelectric (AFE) or paraelectric ordering. We propose to tune the AFE ABPX monolayers into the FE ordering through interface engineering. The mechanism is that there are couplings between the charge polarizations of the ABPX monolayers and the local dipoles as well as the induced electronic polarizations in the substrate which have a tendency to stabilize the FE ordering. We further perform first-principles calculations for CuInPSe and CuCrPS monolayers and their van der Waals heterostructures. We find that an AFE CuInPSe monolayer becomes FE as interfaced with graphene, MoS, and h-BN monolayers. In contrast, the CuCrPS monolayer remains AFE since there is a large energy difference between the AFE and FE phases. Interfacing it with a MoTe monolayer induces a metal-insulator transition for the heterostructure, whereas interfacing with a polar surface MgO(111) can drive it into FE. The interfacing effect can also be used to manipulate the FE properties of ABPX multilayers. We further find that the AFE-to-FE transition is electrically switchable in these systems. In particular, it is accompanied by an indirect-direct band-gap transition for the CuInPSe monolayer. Our study offers an effective approach to tune the FE and electronic properties of ABPX thin films for applications in electronics and optoelectronics.
arXiv comment10 pages, 16 figures
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