6,212 research outputs found
Environmental, Thermal, and Electrical Susceptibility of Black Phosphorus Field Effect Transistors
Atomic layers of black phosphorus (P) isolated from its layered bulk make a
new two-dimensional (2D) semiconducting crystal with sizable direct bandgap,
high carrier mobility, and promises for 2D electronics and optoelectronics.
However, the integrity of black P crystal could be susceptible to a number of
environmental variables and processes, resulting in degradation in device
performance even before the device optical image suggests so. Here, we perform
a systematic study of the environmental effects on black P electronic devices
through continued measurements over a month under a number of controlled
conditions, including ambient light, air, and humidity, and identify evolution
of device performance under each condition. We further examine effects of
thermal and electrical treatments on inducing morphology and, performance
changes and failure modes in black P devices. The results suggest that
procedures well established for nanodevices in other 2D materials may not
directly apply to black P devices, and improved procedures need to be devised
to attain stable device operation.Comment: in Journal of Vacuum Science & Technology B (2015
Resolving and Tuning Mechanical Anisotropy in Black Phosphorus via Nanomechanical Multimode Resonance Spectromicroscopy
Black phosphorus (P) has emerged as a layered semiconductor with a unique
crystal structure featuring corrugated atomic layers and strong in-plane
anisotropy in its physical properties. Here, we demonstrate that the crystal
orientation and mechanical anisotropy in free-standing black P thin layers can
be precisely determined by spatially resolved multimode nanomechanical
resonances. This offers a new means for resolving important crystal orientation
and anisotropy in black P device platforms in situ beyond conventional optical
and electrical calibration techniques. Furthermore, we show that
electrostatic-gating-induced straining can continuously tune the mechanical
anisotropic effects on multimode resonances in black P electromechanical
devices. Combined with finite element modeling (FEM), we also determine the
Young's moduli of multilayer black P to be 116.1 and 46.5 GPa in the zigzag and
armchair directions, respectively.Comment: Main Text: 13 Pages, 4 Figures; Supplementary Information: 5 Pages, 2
Figures, 2 Table
First Principles Study of Adsorption of on Al Surface with Hybrid Functionals
Adsorption of molecule on Al surface has been a long standing puzzle
for the first principles calculation. We have studied the adsorption of
molecule on the Al(111) surface using hybrid functionals. In contrast to the
previous LDA/GGA, the present calculations with hybrid functionals successfully
predict that molecule can be absorbed on the Al(111) surface with a
barrier around 0.20.4 eV, which is in good agreement with
experiments. Our calculations predict that the LUMO of molecule is
higher than the Fermi level of the Al(111) surface, which is responsible for
the barrier of the adsorption.Comment: 14 pages, 5 figure
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