title: Gate-Tunable Giant Stark Effect in Few-Layer Black Phosphorus.
abstract: Two-dimensional black phosphorus (BP) has sparked enormous research interest due to its high carrier mobility, layer-dependent direct bandgap and outstanding in-plane anisotropic properties. BP is one of the few two-dimensional materials where it is possible to tune the bandgap over a wide energy range from the visible up to the infrared. In this article, we report the observation of a giant Stark effect in electrostatically gated few-layer BP. Using low-temperature scanning tunnelling microscopy, we observed that in few-layer BP, when electrons are injected, a monotonic reduction of the bandgap occurs. The injected electrons compensate the existing defect-induced holes and achieve up to 35.5% bandgap modulation in the light-doping regime. When probed by tunnelling spectroscopy, the local density of states in few-layer BP shows characteristic resonance features arising from layer-dependent sub-band structures due to quantum confinement effects. The demonstration of an electrical gate-controlled giant Stark effect in BP paves the way to designing electro-optic modulators and photodetector devices that can be operated in a wide electromagnetic spectral range.
authors.affiliation: Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543.|Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore , Singapore 117546.
authors.forename: Yanpeng
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543.|NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore , 28 Medical Drive, Singapore 117456.
authors.forename: Zhizhan
authors.initials: Z
authors.lastname: Qiu
authors.affiliation: Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore , Singapore 117546.|Department of Physics, National University of Singapore , 3 Science Drive 2, Singapore 117542.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Carvalho
authors.affiliation: Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543.|Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore , Singapore 117546.
authors.forename: Yang
authors.identifier: 0000-0001-9868-4946
authors.initials: Y
authors.lastname: Bao
authors.affiliation: Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543.|Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore , Singapore 117546.
authors.forename: Hai
authors.initials: H
authors.lastname: Xu
authors.affiliation: Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543.|NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore , 28 Medical Drive, Singapore 117456.
authors.forename: Sherman J R
authors.initials: SJ
authors.lastname: Tan
authors.affiliation: Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543.|Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore , Singapore 117546.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore , Singapore 117546.|Department of Physics, National University of Singapore , 3 Science Drive 2, Singapore 117542.
authors.forename: A H
authors.initials: AH
authors.lastname: Castro Neto
authors.affiliation: Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543.|Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore , Singapore 117546.
authors.forename: Kian Ping
authors.identifier: 0000-0002-1491-743X
authors.initials: KP
authors.lastname: Loh
authors.affiliation: Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543.|Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore , Singapore 117546.
authors.forename: Jiong
authors.identifier: 0000-0002-3690-8235
authors.initials: J
authors.lastname: Lu
keywords: Black phosphorus; bandgap; electrostatical-gating; giant Stark effect; scanning tunnelling microscopy