4 research outputs found
Direct On-Chip Optical Plasmon Detection with an Atomically Thin Semiconductor
The determination to develop fast,
efficient devices has led to vast studies on photonic circuits but
it is difficult to shrink these circuits below the diffraction limit
of light. However, the coupling between surface plasmon polaritons
and nanostructures in the near-field shows promise in developing next-generation
integrated circuitry. In this work, we demonstrate the potential for
integrating nanoplasmonic-based light guides with atomically thin
materials for on-chip near-field plasmon detection. Specifically,
we show near-field electrical detection of silver nanowire plasmons
with the atomically thin semiconductor molybdenum disulfide. Unlike
graphene, atomically thin semiconductors such as molybdenum disulfide
exhibit a bandgap that lends itself for the excitation and detection
of plasmons. Our fully integrated plasmon detector exhibits plasmon
responsivities of ∼255 mA/W that corresponds to highly efficient
plasmon detection (∼0.5 electrons per plasmon)
Nanoscale Fluorescence Lifetime Imaging of an Optical Antenna with a Single Diamond NV Center
Solid-state quantum emitters, such
as artificially engineered quantum
dots or naturally occurring defects in solids, are being investigated
for applications ranging from quantum information science and optoelectronics
to biomedical imaging. Recently, these same systems have also been
studied from the perspective of nanoscale metrology. In this letter,
we study the near-field optical properties of a diamond nanocrystal
hosting a single nitrogen vacancy center. We find that the nitrogen
vacancy center is a sensitive probe of the surrounding electromagnetic
mode structure. We exploit this sensitivity to demonstrate nanoscale
fluorescence lifetime imaging microscopy (FLIM) with a single nitrogen
vacancy center by imaging the local density of states of an optical
antenna
Rapid Wafer-Scale Growth of Polycrystalline 2H-MoS<sub>2</sub> by Pulsed Metal–Organic Chemical Vapor Deposition
High-volume
manufacturing of devices based on transition metal
dichalcogenide (TMD) ultrathin films will require deposition techniques
that are capable of reproducible wafer-scale growth with monolayer
control. To date, TMD growth efforts have largely relied upon sublimation
and transport of solid precursors with minimal control over vapor-phase
flux and gas-phase chemistry, which are critical for scaling up laboratory
processes to manufacturing settings. To address these issues, we report
a new pulsed metal–organic chemical vapor deposition (MOCVD)
route for MoS<sub>2</sub> film growth
in a research-grade single-wafer reactor. Using bisÂ(<i>tert</i>-butylimido)ÂbisÂ(dimethylamido)molybdenum and diethyl disulfide, we
deposit MoS<sub>2</sub> films from ∼1 nm to ∼25 nm in
thickness on SiO<sub>2</sub>/Si substrates. We show that layered 2H-MoS<sub>2</sub> can be produced at comparatively low reaction temperatures
of 591 °C at short deposition times, approximately 90 s for few-layer
films. In addition to the growth studies performed on SiO<sub>2</sub>/Si, films with wafer-level uniformity are demonstrated on 50 mm
quartz wafers. Process chemistry and impurity incorporation from precursors
are also discussed. This low-temperature and fast process highlights
the opportunities presented by metal–organic reagents in the
controlled synthesis of TMDs
Characterization of Few-Layer 1T′ MoTe<sub>2</sub> by Polarization-Resolved Second Harmonic Generation and Raman Scattering
We study the crystal
symmetry of few-layer 1T′ MoTe<sub>2</sub> using the polarization
dependence of the second harmonic
generation (SHG) and Raman scattering. Bulk 1T′ MoTe<sub>2</sub> is known to be inversion symmetric; however, we find that the inversion
symmetry is broken for finite crystals with even numbers of layers,
resulting in strong SHG comparable to other transition-metal dichalcogenides.
Group theory analysis of the polarization dependence of the Raman
signals allows for the definitive assignment of all the Raman modes
in 1T′ MoTe<sub>2</sub> and clears up a discrepancy in the
literature. The Raman results were also compared with density functional
theory simulations and are in excellent agreement with the layer-dependent
variations of the Raman modes. The experimental measurements also
determine the relationship between the crystal axes and the polarization
dependence of the SHG and Raman scattering, which now allows the anisotropy
of polarized SHG or Raman signal to independently determine the crystal
orientation