#
APS March Meeting 2016

## Volume 61, Number 2

##
Monday–Friday, March 14–18, 2016;
Baltimore, Maryland

### Session L16: Black Phosphorus Device Physics

11:15 AM–2:15 PM,
Wednesday, March 16, 2016

Room: 315

Sponsoring
Unit:
DMP

Chair: Yuanbo Zhang, Fudan University, China

Abstract ID: BAPS.2016.MAR.L16.5

### Abstract: L16.00005 : \textbf{Nanoscopy Reveals Surface-Metallic Black Phosphorus}.

12:27 PM–12:39 PM

Preview Abstract
Abstract

####
Author:

Yohannes Abate

(Georgia State University)

\textbf{Nanolayer and two-dimensional (2D)
materials.............}$^{\mathrm{\mathbf{1}}}$\textbf{ such as
graphene...}$^{\mathrm{\mathbf{2,3}}}$\textbf{, boron
nitride...}$^{\mathrm{\mathbf{1,4}}}$\textbf{, transition metal
dichalcogenides...}$^{\mathrm{\mathbf{1,5-8}}}$\textbf{ (TMDCs), and black
phosphorus (BP)...}$^{\mathrm{\mathbf{1,9-13}}}$\textbf{ have intriguing
fundamental physical properties and bear promise of important applications
in electronics and optics...}$^{\mathrm{\mathbf{9,14,15}}}$\textbf{. Of
them, BP...}$^{\mathrm{\mathbf{11,12,16}}}$\textbf{ is a novel layered
material that has been theoretically
predicted...}$^{\mathrm{\mathbf{10}}}$\textbf{ to acquire plasmonic behavior
for frequencies below \textasciitilde 0.4 eV when highly doped. The
electronic properties of BP are unique due to its anisotropic
structure}\textbf{. }\textbf{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
chemical or electrostatic gating, which has been demonstrated by its use in
field-effect transistors....}$^{\mathrm{\mathbf{9,14,15}}}$\textbf{ 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 below critical
frequency }$\mathbf{\omega }_{\mathbf{m}} \mathbf{\approx 1176}$\textbf{
cm}$^{\mathrm{\mathbf{-1}}}$\textbf{. This has allowed us to estimate plasma
frequency }$\mathbf{\omega }_{\mathbf{p}} \mathbf{\approx
}\mathbf{0.4}$\textbf{ eV, carrier density }$\mathbf{n}\approx {\rm {\bf
1}}.{\rm {\bf 1}}\times {\rm {\bf 10}}^{{\rm {\bf 11}}} {\rm {\bf
cm}}^{-{\rm {\bf 1}}}$\textbf{ and the thickness of the surface metallic
layer of }${\rm {\bf \sim }}\mathbf{1 nm}$\textbf{. We have also observed
similar behavior in other nanolayer semiconductors such as TMDC
MoS}$_{\mathrm{\mathbf{2}}}$\textbf{ and topological insulator
Bi}$_{\mathrm{\mathbf{2}}}$\textbf{Te}$_{\mathrm{\mathbf{3}}}$\textbf{ but
not in insulators such as boron nitride. This new phenomenon is attributed
to surface band-bending and charging of the semiconductor nanofilms. The
surface plasmonic behavior has been found for 10-40 nm BP thickness but
absent for 4 nm BP thickness. This discovery opens up a new field of
research and potential applications in nanoelectronics, plasmonics, and
optoelectronics.}

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2016.MAR.L16.5