Plasmon-enhanced fluorescence is demonstrated in the vicinity of metal surfaces due to strong local field enhancement. Meanwhile, fluorescence quenching is observed as the spacing between fluorophore molecules and the adjacent metal is reduced below a threshold of a few nanometers. Here, we introduce a technology, placing the fluorophore molecules in plasmonic hotspots between pairs of collapsible nanofingers with tunable gap sizes at sub-nanometer precision. Optimal gap sizes with maximum plasmon enhanced fluorescence are experimentally identified for different dielectric spacer materials. The ultrastrong local field enhancement enables simultaneous detection and characterization of sharp Raman fingerprints in the fluorescence spectra. This platform thus enables in situ monitoring of competing excitation enhancement and emission quenching processes. We systematically investigate the mechanisms behind fluorescence quenching. A quantum mechanical model is developed which explains the experimental data and will guide the future design of plasmon enhanced spectroscopy applications.

inherent drawbacks of transmissive displays. First, all light from a transmissive display is provided by an active light source that consumes energy continuously when the display works. Besides, the display can be quite dim under direct sunlight. Compared to transmissive display, reflective display is illuminated by ambient light. Therefore, it does not consume energy for backlight and is readable under bright sunlight. Then, we invented a "perfect" display by stacking a full-color reflective display on top of a transmissive display ( Figure S1, Supporting Information). This hybrid display can operate in either transmissive or reflective mode. It has not only low power consumption by staying at low-power reflective mode most of the time, but also superior display quality in both low-light and bright sunlight environments. While there are mature transmissive display technologies, reflective display technologies that satisfy hybrid display requirements are still unavailable. One fundamental issue is that the parallel architecture is currently adopted in full-color reflective display technologies [1] (Figure S2, Supporting Information). Even in the ideal case, the optical efficiency of a parallel architecture is limited to a poor value of 33% owing to the filling ratio of each subpixels. Additionally, none of the proposed color reflective displays could be switched into a transparent state, [2] which is critical in a hybrid display.Fortunately, the breakthroughs of nanophotonics [3] and nanofabrication technologies [4] in past decades have vigorously promoted the development of optical metasurfaces, which provide an opportunity to get a "perfect" hybrid display. With the help of precisely designed metasurfaces, incident light can be effectively manipulated. [5] Compared to metallic metasurfaces, all-dielectric metasurfaces have higher optical efficiency and broader bandwidth. [6] However, the difficulty in finding highindex and low-loss dielectrics in near-IR or visible wavelength range limited the application of all-dielectric metasurfaces to longer wavelengths. To solve this problem, we recently pioneered hybrid all-dielectric metasurfaces for efficient ultrabroadband reflector and spectrum splitting. [7] In parallel, we also tailored nanoimprint lithography (NIL) to fabricate largearea metasurfaces in near-IR or visible ranges. [8] Based on these, we proposed a novel application of all-dielectric metasurface High energy consumption and lack of readability under bright sunlight of conventional transmissive display technology greatly limit the user experience of mobile and wearable devices. To solve this issue, a hybrid display by overlaying a full-color reflective display on top of a transmissive display is invented.The key component of this technology is a full-color reflective display based on tandem switchable all-dielectric metasurfaces. The switchable all-dielectric metasurfaces in large size (average area ≈5 cm 2 ) are invented and fabricated by low-cost and high-throughput nanoimprint lithography. Each ...

Memristive devices (i.e., memristors) can be highly beneficial in many emerging applications that may play important roles in the future generations of electronic systems, such as bioinspired neuromorphic computing, high density nonvolatile memory, and field programmable gate arrays. Therefore, the memristor characteristics (such as operation voltage, on/off ratio, and the number of conductance states) must be engineered carefully for different applications. Here, we demonstrate a method to modify the memristor characteristics specifically by controlling the crystallinity of the switching layer material. Through setting the temperature of atomic layer deposition, the crystallinity of deposited Al 2 O 3 can be controlled. Using different crystalline Al 2 O 3 as the memristor switching layer, the characteristics of the corresponding Pt/Al 2 O 3 /Ta/Pt cross-point memristors can be modified precisely. The high I-V linearity, high on/off ratio (around 10 8 ), low pulse operation voltage (2.5 V), and multilevel conductance states (314 states) of the Pt/Al 2 O 3 /Ta/Pt cross-point memristor are demonstrated. More importantly, the mechanism behind this phenomenon is studied. This work deepens our understanding of the working mechanism of memristors and paves the way for using memristors in a broad spectrum of applications.

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