A fabrication process that combines an ultrathin alumina membrane (UTAM) surface nanopatterning technique and a physical vapor deposition method has been designed for realizing well‐defined Au ...nanoparticle arrays for sensitive, uniform, and stable surface‐enhanced Raman scattering (SERS)‐active substrates. High Raman signals are obtained by adjusting the structural parameters of the metallic nanoparticles when rhodamine 6G (R6G) and 4‐mercaptopyridine (4‐MP) are used as the probe molecules. The corresponding estimated enhancement factors (EFs) are 6.5×106 (R6G) and 6.8×105 (4‐MP), respectively. The simulated distributions of the electric field of SERS substrates coincide with the experimental results. Raman measurements at randomly selected spots on a substrate show a standard EF deviation of about 5 %, which indicates a desirable SERS uniformity. An advantageous feature of our SERS substrate is its long‐term stability of enhanced Raman signals. Raman measurements on a substrate after one year show almost the same magnitude of Raman signal (106 for R6G and 105 for 4‐MP) as that of the original measurement. Such substrates with good SERS sensitivity, uniformity, and stability should have high potential for SERS‐related applications.
Insane for the membrane: Surface‐enhanced Raman scattering (SERS) substrates with high uniformity and stability have been achieved based on large‐area well‐defined gold nanoparticle arrays, which can be obtained by a fabrication process that combines an ultrathin alumina membrane surface nanopatterning technique and physical vapor deposition (see figure). An advantageous feature of such a SERS substrate is its long‐term stability.
Aiming to unravel the relationship between chemical configuration and electronic structure of sp
defects of aryl-functionalized (6,5) single-walled carbon nanotubes (SWCNTs), we perform ...low-temperature single nanotube photoluminescence (PL) spectroscopy studies and correlate our observations with quantum chemistry simulations. We observe sharp emission peaks from individual defect sites that are spread over an extremely broad, 1000-1350 nm, spectral range. Our simulations allow us to attribute this spectral diversity to the occurrence of six chemically and energetically distinct defect states resulting from topological variation in the chemical binding configuration of the monovalent aryl groups. Both PL emission efficiency and spectral line width of the defect states are strongly influenced by the local dielectric environment. Wrapping the SWCNT with a polyfluorene polymer provides the best isolation from the environment and yields the brightest emission with near-resolution limited spectral line width of 270 μeV, as well as spectrally resolved emission wings associated with localized acoustic phonons. Pump-dependent studies further revealed that the defect states are capable of emitting single, sharp, isolated PL peaks over 3 orders of magnitude increase in pump power, a key characteristic of two-level systems and an important prerequisite for single-photon emission with high purity. These findings point to the tremendous potential of sp
defects in development of room temperature quantum light sources capable of operating at telecommunication wavelengths as the emission of the defect states can readily be extended to this range via use of larger diameter SWCNTs.
The realization of on-chip quantum networks ideally requires lossless interfaces between photons and solid-state quantum emitters. We propose and demonstrate on-chip arrays of metallo-dielectric ...antennas (MDA) that are tailored toward efficient and broadband light collection from individual embedded carbon nanotube quantum emitters by trapping air gaps on chip that form cavity modes. Scalable implementation is realized by employing polymer layer dry-transfer techniques that avoid solvent incompatibility issues, as well as a planar design that avoids solid-immersion lenses. Cryogenic measurements demonstrate 7-fold enhanced exciton intensity when compared to emitters located on bare wafers, corresponding to a light collection efficiency (LCE) up to 92% in the best case (average LCE of 69%) into a narrow output cone of ±15° that enables a priori fiber-to-chip butt coupling. The demonstrated MDA arrays are directly compatible with other quantum systems, particularly 2D materials, toward enabling efficient on-chip quantum light sources or spin-photon interfaces requiring unity light collection, both at cryogenic or room temperature.
Two-dimensional semiconductors, including transition metal dichalcogenides, are of interest in electronics and photonics but remain nonmagnetic in their intrinsic form. Previous efforts to form ...two-dimensional dilute magnetic semiconductors utilized extrinsic doping techniques or bulk crystal growth, detrimentally affecting uniformity, scalability, or Curie temperature. Here, we demonstrate an in situ substitutional doping of Fe atoms into MoS
monolayers in the chemical vapor deposition growth. The iron atoms substitute molybdenum sites in MoS
crystals, as confirmed by transmission electron microscopy and Raman signatures. We uncover an Fe-related spectral transition of Fe:MoS
monolayers that appears at 2.28 eV above the pristine bandgap and displays pronounced ferromagnetic hysteresis. The microscopic origin is further corroborated by density functional theory calculations of dipole-allowed transitions in Fe:MoS
. Using spatially integrating magnetization measurements and spatially resolving nitrogen-vacancy center magnetometry, we show that Fe:MoS
monolayers remain magnetized even at ambient conditions, manifesting ferromagnetism at room temperature.
A fabrication process that combines an ultrathin alumina membrane (UTAM) surface nanopatterning technique and a physical vapor deposition method has been designed for realizing welldefined Au ...nanoparticle arrays for sensitive, uniform, and stable surface-enhanced Raman scattering (SERS)-active substrates. High Raman signals are obtained by adjusting the structural parameters of the metallic nanoparticles when rhodamine 6G (R6G) and 4-mercaptopyridine (4-MP) are used as the probe molecules. The corresponding estimated enhancement factors (EFs) are 6.5 x 10^sup 6^ (R6G) and 6.8 x 10^sup 5^ (4-MP), respectively. The simulated distributions of the electric field of SERS substrates coincide with the experimental results. Raman measurements at randomly selected spots on a substrate show a standard EF deviation of about 5%, which indicates a desirable SERS uniformity. An advantageous feature of our SERS substrate is its long-term stability of enhanced Raman signals. Raman measurements on a substrate after one year show almost the same magnitude of Raman signal (10^sup 6^ for R6G and 10^sup 5^ for 4-MP) as that of the original measurement. Such substrates with good SERS sensitivity, uniformity, and stability should have high potential for SERS-related applications.
Magnetic and thermal microscopy can be performed concurrently to probe physical performance of integrated circuits. We present wide-field imaging of current-induced magnetic and thermal patterns ...using optically-detected magnetic resonance of NV − centers in nanodiamond ensembles.
Single spin arrays can serve as a scalable qubit platform. Here, we report the observation of arrays of single spins which are optically accessible through strain-induced localized positive trions ...residing in WSe 2 /CrI 3 heterostructures.
The negatively-charged nitrogen vacancy (NV\(^-\)) centre in diamond is a remarkable optical quantum sensor for a range of applications including, nanoscale thermometry, magnetometry, single photon ...generation, quantum computing, and communication. However, to date the performance of these techniques using NV\(^-\) centres has been limited by the thermally-induced spectral wandering of NV\(^-\) centre photoluminescence due to detrimental photothermal heating. Here we demonstrate that solid-state laser refrigeration can be used to enable rapid (ms) optical temperature control of nitrogen vacancy doped nanodiamond (NV\(^-\):ND) quantum sensors in both atmospheric and \textit{in vacuo} conditions. Nanodiamonds are attached to ceramic microcrystals including 10\% ytterbium doped yttrium lithium fluoride (Yb:LiYF\(_4\)) and sodium yttrium fluoride (Yb:NaYF\(_4\)) by van der Waals bonding. The fluoride crystals were cooled through the efficient emission of upconverted infrared photons excited by a focused 1020 nm laser beam. Heat transfer to the ceramic microcrystals cooled the adjacent NV\(^-\):NDs by 10 and 27 K at atmospheric pressure and \(\sim\)10\(^{-3}\) Torr, respectively. The temperature of the NV\(^-\):NDs was measured using both Debye-Waller factor (DWF) thermometry and optically detected magnetic resonance (ODMR), which agree with the temperature of the laser cooled ceramic microcrystal. Stabilization of thermally-induced spectral wandering of the NV\(^{-}\) zero-phonon-line (ZPL) is achieved by modulating the 1020 nm laser irradiance. The demonstrated cooling of NV\(^-\):NDs using an optically cooled microcrystal opens up new possibilities for rapid feedback-controlled cooling of a wide range of nanoscale quantum materials.
Creating exciton localization via covalent sp
3
functionalization of single-walled carbon nanotubes (SWCNTs) is a promising route to enhance the optical quantum yield and can furthermore lead to ...single-photon emission at room temperatures 1. Of recent interest are aryl-functionalized SWCNTs that are protected by polyfluorene, for which we have recently shown that a variety of chemically and energetically distinct defect state exist that have their origin in topological variation in the chemical binding configuration of the monovalent aryl groups 2. Here we extend our study by embedding aryl-functionalized SWCNTs into metallo-dielectric antennas that provide broadband coupling with near-unity light collection efficiencies by trapping air gaps on chip that form cavity modes. Scalable implementation is realized by employing polymer layer dry-transfer techniques that avoid solvent incompatibility issues, as well as a planar design that avoids solid-immersion lenses, resulting in a narrow output cone of ±15° that enables a priori fiber-to-chip butt coupling. In these devices the exciton emission from the aryl-functionalized sides (E
11
*) remains spectrally sharp with linewidth values near the resolution limit of about 35 meV. Interestingly, we find that the pump-induced dephasing for E
11
* exciton (0D exciton) is significantly reduced by more than 300% as compared to the E
11
exciton (1D exciton), thereby preserving exciton coherence even into the high pump power regime, as needed for practical devices in quantum photonics. We will discuss how these findings provide a foundation to build unified descriptions on emergence of novel optical behavior from the interplay of covalent dopants, dispersants, and excitons in SWCNTs.
1 He, X.
et al.
Tunable room-temperature single-photon emission at telecom wavelengths from sp
3
defects in carbon nanotubes.
Nature Photonics
11
, 577–582 (2017).
2 He, X.
et al.
Low-Temperature Single Carbon Nanotube Spectroscopy of sp
3
Quantum Defects,
ACS Nano
, Articles ASAP (2017); DOI:10.1021/acsnano.7b03022
In a unique interplay of excitons, phonons, and plasmons, we demonstrate plasmonic thermometry at the single-molecule level by detecting the plasmonically induced heat from SWCNT excitons coupled to ...plasmonic nanocavity arrays.
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