Nanoscopy Reveals Metallic Black Phosphorus

Abstract

Layered and two-dimensional (2D) materials such as graphene, boron nitride, transition metal dichalcogenides(TMDCs), and black phosphorus (BP) have intriguing fundamental physical properties and bear promise of numerous important applications in electronics and optics. Of them, BP is a novel 2D material that has been theoretically predicted to acquire plasmonic behavior for frequencies below ~0.4 eV when highly doped. The electronic properties of BP are unique due to an anisotropic structure, which could strongly influence collective electronic excitations. Advantages of BP as a material for nanoelectronics and nanooptics are due to the fact that, in contrast to metals, the free carrier density in it can be dynamically controlled by electrostatic gating, which has been demonstrated by its use in field-effect transistors. Despite all the interest that BP attracts, near-field and plasmonic properties of BP have not yet been investigated experimentally. Here we report the first observation of nanoscopic near-field properties of BP. We have discovered near field patterns of outside bright fringes and high surface polarizability of nanofilm BP consistent with its surface-metallic, plasmonic behavior at mid-infrared (mid-IR) frequencies. This behavior is highly frequency-dispersive, disappearing above frequency, ω =1070 cm-1, which allowed us to estimate the plasma frequency and carrier density. We have also observed similar behavior in other 2D semiconductors such as TMDCs but not in 2D insulators such as boron nitride. This new phenomenon is attributed to surface charging of the semiconductor nanofilms. This discovery opens up a new field of research and potential applications in nanoplasmonics and optoelectronics.

arXiv comment9 pages, 5 figures

References in corpus (17)

• Two-Dimensional Gas of Massless Dirac Fermions in Graphene
• Black phosphorus field-effect transistors
• Rediscovering Black Phosphorus: A Unique Anisotropic 2D Material for Optoelectronics and Electronics
• Two-Dimensional Material Nanophotonics
• Tunable Band Gap and Anisotropic Optical Response in Few-layer Black Phosphorus
• Strain-induced gap modification in black phosphorus
• Effective Passivation of Exfoliated Black Phosphorus Transistors against Ambient Degradation
• Graphene Plasmonics for Terahertz to Mid-Infrared Applications
• Electric field effect in ultrathin black phosphorus
• Strong light-matter coupling in two-dimensional atomic crystals
• Probing Excitonic Dark States in Single-layer Tungsten Disulfide
• Observation of tunable bandgap and anisotropic Dirac semimetal state in black phosphorus
• Waveguide-integrated black phosphorus photodetector with high responsivity and low dark current
• Plasmons and screening in monolayer and multilayer black phosphorus
• Infrared nanoscopy of Dirac plasmons at the graphene-SiO2 interface
• Device Perspective for Black Phosphorus Field-Effect Transistors: Contact Resistance, Ambipolar and Scaling
• Unusual Scaling Laws of the Band Gap and Optical Absorption of Phosphorene Nanoribbons

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• Comprehensive ab initio study of effects of alloying elements on generalized stacking fault energies of Ni and Ni${}_3$Al