A suspended InSe membrane-based metal-semiconductor junction with excellent performance via flexoelectricity

Abstract

Two-dimensional semiconductor (2DS) materials exhibit immense potential for flexible electronic and photoelectronic devices due to their ultra-thin structural features. This paper proposes a suspended 2DS-InSe membrane-based metal-semiconductor junction (MSJ) structure, specifically designed to induce non-uniform tensile strain. This configuration enables a significant flexoelectric-induced in-plane polarization field while mitigating substrate effects. The effect of strain-gradient-induced flexoelectric polarization field on the performance of the proposed 2DS-InSe membrane-based MSJ is investigated using the CAFM, PFM and KPFM modules to characterize current-voltage (I-V) characteristics, out-of-plane electromechanical response, and surface potential. The suspended 2DS-InSe with thickness of 60 nm demonstrates enhanced electromechanical and photoelectric responses, as well as increased output current, compared to the supported 2DS-InSe, attributed to the larger in-plane polarization induced by non-uniform tensile strain. Additionally, the in-plane ($f_{1111}=f_{2222}=3.053$ nC/m, $f_{1221}=f_{2112}=-9.374$ nC/m) and the out-of-plane ($f_{3113}=f_{3223}=-0.0188$ nC/m, $f_{3333}=-0.1407$ nC/m) flexoelectric coefficients of the used 2DS-InSe are evaluated. This study demonstrates that that the electrical, electromechanical, and photoelectric properties of membrane-based MSJs can be mechanically tuned through the flexoelectric-induced polarization fields, offering valuable insights for the development of novel membrane-based devices utilizing 2DS materials.