Kirigami, with facile and automated fashion of three-dimensional (3D) transformations, offers an unconventional approach for realizing cutting-edge optical nano-electromechanical systems. Here, we demonstrate an on-chip and electromechanically reconfigurable nano-kirigami with optical functionalities. The nano-electromechanical system is built on an Au/SiO2/Si substrate and operated via attractive electrostatic forces between the top gold nanostructure and bottom silicon substrate. Large-range nano-kirigami like 3D deformations are clearly observed and reversibly engineered, with scalable pitch size down to 0.975 μm. Broadband nonresonant and narrowband resonant optical reconfigurations are achieved at visible and near-infrared wavelengths, respectively, with a high modulation contrast up to 494%. On-chip modulation of optical helicity is further demonstrated in submicron nano-kirigami at near-infrared wavelengths. Such small-size and high-contrast reconfigurable optical nano-kirigami provides advanced methodologies and platforms for versatile on-chip manipulation of light at nanoscale.

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Photodetection based on two-dimensional (2D) SnS has attracted growing interest due to its superiority in response rate and responsivity, but high-quality growth and high performance photodetection of 2D SnS still face great challenges. Here, high-quality SnS nanoflakes with large-size and high-production are vertically grown on an Si substrate by a modified CVD method, having an average size of 30 μm with different thicknesses. Then a single SnS nanoflake-based phototransistor was fabricated to obtain a high current on/off ratio of 10 and excellent performance in photodetection, including fast response rates, low dark current, and high responsivity and detectivity. Specifically, the SnS nanoflakes show thickness-dependent photodetection capability, and a highest responsivity of 354.4 A W is obtained at the average thickness of 100.5 nm. A sensitized process using an HfO nanolayer can further enhance the responsivity up to 1922 A W. Our work provides an efficient path to select SnS crystal samples with the optimal thickness as promising candidates for high-performance optoelectronic applications.

Considering the technological difficulties in the existing approaches to form nanoscale gaps, a convenient method to fabricate three-dimensional (3D) sub-10 nm Ag/SiN gap arrays has been demonstrated in this study, controlled by a combination of stress-induced nanocracking of a SiN nanobridge and Ag nanofilm deposition. This scalable 3D plasmonic nanogap is specially suspended above a substrate, having a tunable nanogap width and large height-to-width ratio to form a nanocavity underneath. As a surface-enhanced Raman scattering (SERS) substrate, the 3D Ag/SiN nanogap shows a large Raman enhancement factor of ∼10 and extremely high sensitivity for the detection of Rhodamine 6G (R6G) molecules, even down to 10 M, indicating an extraordinary capability for single-molecule detection. Further, we verified that the Fabry-Perot resonance occurred in the deep SiN nanocavity under the Ag nanogap and contributed prominently to a tremendous enhancement of the local field in the Ag-nanogap zone and hence ultrasensitive SERS detection. This method circumvents the technological limitations to fabricate a sub-10 nm metal nanogap with unique features for wide applications in important scientific and technological areas.