305 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
Polytype control of spin qubits in silicon carbide
Crystal defects can confine isolated electronic spins and are promising
candidates for solid-state quantum information. Alongside research focusing on
nitrogen vacancy centers in diamond, an alternative strategy seeks to identify
new spin systems with an expanded set of technological capabilities, a
materials driven approach that could ultimately lead to "designer" spins with
tailored properties. Here, we show that the 4H, 6H and 3C polytypes of SiC all
host coherent and optically addressable defect spin states, including spins in
all three with room-temperature quantum coherence. The prevalence of this spin
coherence shows that crystal polymorphism can be a degree of freedom for
engineering spin qubits. Long spin coherence times allow us to use double
electron-electron resonance to measure magnetic dipole interactions between
spin ensembles in inequivalent lattice sites of the same crystal. Together with
the distinct optical and spin transition energies of such inequivalent spins,
these interactions provide a route to dipole-coupled networks of separately
addressable spins.Comment: 28 pages, 5 figures, and supplementary information and figure
- …