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-MoS₂ 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 MoS₂ film growth in a research-grade single-wafer reactor. Using bis­(<i>tert</i>-butylimido)­bis­(dimethylamido)molybdenum and diethyl disulfide, we deposit MoS₂ films from ∼1 nm to ∼25 nm in thickness on SiO₂/Si substrates. We show that layered 2H-MoS₂ 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 SiO₂/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′ MoTe₂ by Polarization-Resolved Second Harmonic Generation and Raman Scattering

We study the crystal symmetry of few-layer 1T′ MoTe₂ using the polarization dependence of the second harmonic generation (SHG) and Raman scattering. Bulk 1T′ MoTe₂ 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′ MoTe₂ 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