2 research outputs found
Tuning the Electronic and Magnetic Properties of Phosphorene by Vacancies and Adatoms
We
report a density functional theory (DFT) study regarding the
effects of atomic defects, such as vacancies and adatom adsorption,
on the electronic and magnetic properties of phosphorene (a two-dimensional
monolayer of black phosphorus). A monovacancy in the phosphorene creates
an in-gap state in the band gap of pristine phosphorene and induces
a
magnetic moment, even though pristine phosphorene is nonmagnetic.
In contrast, both planar and staggered divacancies do not change the
magnetic properties of phosphorene, although a staggered divacancy
creates states in the gap. Our DFT calculations also show that adsorption
of nonmetallic elements (C, N, and O) and transition metal elements
(Fe, Co, and Ni) can change the magnetic properties of phosphorene
with or without vacancies. For example, the nonmagnetic pristine phosphorene
becomes magnetic after the adsorption of N, Fe, or Co adatoms, and
the magnetic phosphorene with a monovacancy becomes nonmagnetic after
the adsorption of C, N, or Co atoms. We also demonstrate that for
O- or Fe-adsorbed monovacancy structure the electronic and magnetic
properties are tunable via the control of charge on the phosphorene
system. These results provide insight for achieving metal-free magnetism
and a tunable band gap for various electronic and spintronic devices
based on phosphorene
Raman Radial Mode Revealed from Curved Graphene
One of the unsolved
fundamental issues of graphene is establishing
an appropriate way to discern layers of graphene structures. We report
a simple methodology to analyze graphene structures using Raman signals
in the range of ∼100 to ∼500 cm<sup>–1</sup> comprising
clear 118 or 175 cm<sup>–1</sup> peaks. We demonstrate that
the low-energy signals on Raman spectra of plasma-seeded grown graphene
sheets originated from nanocurvature (<i>c</i>) of mono-
(175 and 325–500 cm<sup>–1</sup> signals) (<i>c</i> ≈ 1 nm) and bilayer (118 cm<sup>–1</sup> peak) (<i>c</i> ≈ 2 nm) graphene with Raman simulations, based
on Raman radial mode (RM) Eigen vectors. Our RM model provides a standard
way of identifying and evaluating graphene structures