Microscopic mechanism of tunable band gap in potassium doped few-layer black phosphorus

Abstract

Tuning band gaps in two-dimensional (2D) materials is of great interest in the fundamental and practical aspects of contemporary material sciences. Recently, black phosphorus (BP) consisting of stacked layers of phosphorene was experimentally observed to show a widely tunable band gap by means of the deposition of potassium (K) atoms on the surface, thereby allowing great flexibility in design and optimization of electronic and optoelectronic devices. Here, based on the density-functional theory calculations, we demonstrates that the donated electrons from K dopants are mostly localized at the topmost BP layer and such a surface charging efficiently screens the K ion potential. It is found that, as the K doping increases, the extreme surface charging and its screening of K atoms shift the conduction bands down in energy, i.e., towards higher binding energy, because they have more charge near the surface, while it has little influence on the valence bands having more charge in the deeper layers. This result provides a different explanation for the observed tunable band gap compared to the previously proposed giant Stark effect where a vertical electric field from the positively ionized K overlayer to the negatively charged BP layers shifts the conduction band minimum ${\Gamma }_{1c}$ (valence band minimum ${\Gamma }_{8v}$) downwards (upwards). The present prediction of ${\Gamma }_{1c}$ and ${\Gamma }_{8v}$ as a function of the K doping reproduces well the widely tunable band gap, anisotropic Dirac semimetal state, and band-inverted semimetal state, as observed by angle-resolved photoemission spectroscopy experiment. Our findings shed new light on a route for tunable band gap engineering of 2D materials through the surface doping of alkali metals.

arXiv comment7 pages, 5 figures

References in corpus (19)

• Electric Field Effect in Atomically Thin Carbon Films
• Two-Dimensional Gas of Massless Dirac Fermions in Graphene
• Experimental Observation of Quantum Hall Effect and Berry's Phase in Graphene
• Black phosphorus field-effect transistors
• Phosphorene: A New 2D Material with High Carrier Mobility
• High-mobility transport anisotropy and linear dichroism in few-layer black phosphorus
• Strain-induced gap modification in black phosphorus
• The Renaissance of Black Phosphorus
• Strain-Engineering Anisotropic Electrical Conductance of Phosphorene and Few-Layer Black Phosphorus
• Graphene field-effect-transistors with high on/off current ratio and large transport band gap at room temperature
• Observation of tunable bandgap and anisotropic Dirac semimetal state in black phosphorus
• Direct Observation of Layer-Dependent Electronic Structure in Phosphorene
• Electric Field Induced Topological Phase Transition in Two-Dimensional Few-layer Black Phosphorus
• Ambipolar Insulator-to-Metal Transition in Black Phosphorus by Ionic-Liquid Gating
• Carrier Plasmon Induced Nonlinear Band Gap Renormalization in Two-Dimensional Semiconductors
• Emergence of Two-Dimensional Massless Dirac Fermions, Chiral Pseudospins, and Berry's Phase in Potassium Doped Few-Layer Black Phosphorus
• Generation of Anisotropic Massless Dirac Fermions and Asymmetric Klein Tunneling in Few-Layer Black Phosphorus Superlattices
• Unconventional topological phase transition in two-dimensional systems with space-time inversion symmetry
• Equivalence of Electronic and Mechanical Stresses in Structural Phase Stabilization: A Case Study of Indium Wires on Si(111)

Cited by in corpus (8)

• Anisotropic two-dimensional screening at the surface of black phosphorus
• Non-equilibrium Band Broadening, Gap Renormalization and Band Inversion in Black Phosphorus
• Ultrafast Dynamics of the Surface Photovoltage in Potassium Doped Black Phosphorus
• Electronic structure and conductivity in functionalized multilayer black phosphorene
• Alkali-metal induced band structure deformation investigated by angle-resolved photoemission spectroscopy and first-principles calculations
• Gating orbital memory with an atomic donor
• Effect of the sample work function on alkali metal dosing induced electronic structure change
• Low-frequency interlayer phonon dynamics and photoinduced terahertz absorption in black phosphorus