THESIS
2016
xiv, 67 pages : illustrations (chiefly color) ; 30 cm
Abstract
Atomically thin black phosphorus, which possesses high theoretical mobility and tunable bandgap
structure, has attracted much attention since its rediscovery in 2014. However, degradation of the
quality under atmospheric conditions limits its applications in nanoelectronic and optoelectronic
devices. To solve this problem, I take advantage of hexagonal boron nitride thin flakes to obtain
stable black phosphorus and investigate the electronic properties of monolayer and few-layer black
phosphorus encapsulated between hexagonal boron nitrides thin flakes. This thesis mainly involves
of three projects I have been devoted to. My first project measures the transport properties of this
sandwiched structure. It achieves a high FET mobility ( 1350cm
2V
-1s
-1 at room temperature) in
few-la...[
Read more ]
Atomically thin black phosphorus, which possesses high theoretical mobility and tunable bandgap
structure, has attracted much attention since its rediscovery in 2014. However, degradation of the
quality under atmospheric conditions limits its applications in nanoelectronic and optoelectronic
devices. To solve this problem, I take advantage of hexagonal boron nitride thin flakes to obtain
stable black phosphorus and investigate the electronic properties of monolayer and few-layer black
phosphorus encapsulated between hexagonal boron nitrides thin flakes. This thesis mainly involves
of three projects I have been devoted to. My first project measures the transport properties of this
sandwiched structure. It achieves a high FET mobility ( 1350cm
2V
-1s
-1 at room temperature) in
few-layer black phosphorus-based heterostructure and quantum oscillations at cryogenic temperatures
are observed at magnetic field~6T. This sandwiched heterostructure ensures that the quality
of black phosphorus remains high even when exposed in the air for one week. My second project
investigates the electron states of monolayer and few-layer black phosphorus at temperatures down
to 2 K through capacitance spectroscopy with a vertical heterostructure. Electron states in conduction
and valence bands are accessible within a wide range of temperature and frequencies. We have
observed the giant temperature-dependence of the electron states in few-layer black phosphorus.
Combined with the first-principle calculations, we conclude that thermal excitation of charge trap states and oxidation-induced effect are the main reasons for this phenomenon. My third project
manages to observe the negative compressibility in atomically thin black phosphorus at low carrier
density region. The encapsulation of black phosphorus by hexagonal boron nitrides with few-layer
graphene as a terminal ensures the ultraclean interfaces. This observed the negative compressibility
is explained based on the Coulomb correlation among in-plane charges and their image charges in
a gate electrode in the framework of Debye screening.
Post a Comment