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Flexible photodetectors are pivotal in contemporary optoelectronic technology applications, such as data reception and image sensing, yet their performance and yield are often hindered by the challenge of heterogeneous integration between photoactive materials and flexible substrates. Here, we showcase the potential of an electrostatic force-assisted transfer printing technique for integrating Si PIN photodiodes onto flexible substrates. This clean and dry process eliminates the need for chemical etchants, making it a highly desirable method for manufacturing high-performance flexible photodetector arrays, expanding their widespread applications in electronic eyes, robotics, and human-machine interaction. As a demonstration, a 5 × 5 flexible Si photodetector focal plane array is constructed for imaging sensors and shaped into a convex semicylindrical form to achieve a π field of view with long-term mechanical and thermal stability. Such an approach provides a high yield rate and consistent performance, with the single photodetector demonstrating exceptional characteristics, including a responsivity of 0.61 A/W, a response speed of 39.77 MHz, a linear dynamic range of 108.53 dB, and a specific detectivity of 2.75 × 10 12 Jones at an applied voltage of -3 V at 940 nm.

Surface-enhanced Raman spectroscopy has emerged as a powerful spectroscopy technique for detection with its capacity for label-free, nondestructive analysis, and ultrasensitive characterization. High-performance surface-enhanced Raman scattering (SERS) substrates with homogeneity and low cost are the key factors in chemical and biomedical analysis. In this study, we propose the technique of atomic force microscopy (AFM) scratching and nanoskiving to prepare periodic folded gold (Au) nanostructures as SERS substrates. Initially, folded Au nanostructures with tunable nanogaps and periodic structures are created through the scratching of Au films by AFM, the deposition of Ag/Au films, and the cutting of epoxy resin, reducing fabrication cost and operational complexity. Periodic folded Au nanostructures show the three-dimensional nanofocusing effect, hotspot effect, and standing wave effect to generate an extremely high electromagnetic field. As a typical molecule to be tested, p -aminothiophenol has the lowest detection limit of up to 10 -9 M, owing to the balance between the electromagnetic field energy concentration and the transmission loss in periodic folded Au nanostructures. Finally, by precisely controlling the periods and nanogap widths of the folded Au nanostructures, the synergistic effect of surface plasmon resonance is optimized and shows good SERS properties, providing a new strategy for the preparation of plasmonic nanostructures.

Two-dimensional In 2 Se 3 , an unconventional phase-change material, has drawn considerable attention for polymorphic phase transitions and electronic device applications. However, its reversible thermally driven phase transitions and potential use in photonic devices have yet to be explored. In this study, we observe the thermally driven reversible phase transitions between α and β' phases with the assistance of local strain from surface wrinkles and ripples, as well as reversible phase changes within the β phase family. These transitions lead to changes in the refractive index and other optoelectronic properties with minimal optical loss at telecommunication bands, which are crucial in integrated photonic applications such as postfabrication phase trimming. Additionally, multilayer β'-In 2 Se 3 working as a transparent microheater proves to be a viable option for efficient thermo-optic modulation. This prototype design for layered In 2 Se 3 offers immense potential for integrated photonics and paves the way for multilevel, nonvolatile optical memory applications.

Hybrid integration of van der Waals materials on a photonic platform enables diverse exploration of novel active functions and significant improvement in device performance for next-generation integrated photonic circuits, but developing waveguide-integrated photodetectors based on conventionally investigated transition metal dichalcogenide materials at the full optical telecommunication bands and mid-infrared range is still a challenge. Here, we integrate PdSe 2 with silicon waveguide for on-chip photodetection with a high responsivity from 1260 to 1565 nm, a low noise-equivalent power of 4.0 pW·Hz -0.5 , a 3-dB bandwidth of 1.5 GHz, and a measured data rate of 2.5 Gbit·s -1 . The achieved PdSe 2 photodetectors provide new insights to explore the integration of novel van der Waals materials with integrated photonic platforms and exhibit great potential for diverse applications over a broad infrared range of wavelengths, such as on-chip sensing and spectroscopy.

Due to the excellent electrical and optical properties and their integration capability without lattice matching requirements, low-dimensional materials have received increasing attention in silicon photonic circuits. Bi 2 O 2 Se with high carrier mobility, narrow bandgap, and good air stability is very promising for high-performance near-infrared photodetectors. Here, the chemical vapor deposition method is applied to grow Bi 2 O 2 Se onto mica, and our developed polycarbonate/polydimethylsiloxane-assisted transfer method enables the clean and intact transfer of Bi 2 O 2 Se on top of a silicon waveguide. We demonstrated the Bi 2 O 2 Se/Si waveguide integrated photodetector with a small dark current of 72.9 nA, high responsivity of 3.5 A·W -1 , fast rise/decay times of 22/78 ns, and low noise-equivalent power of 15.1 pW·Hz -0.5 at an applied voltage of 2 V in the O-band for transverse electric modes. Additionally, a microring resonator is designed for enhancing light-matter interaction, resulting in a wavelength-sensitive photodetector with reduced dark current (15.3 nA at 2 V) and more than a 3-fold enhancement in responsivity at the resonance wavelength, which is suitable for spectrally resolved applications. These results promote the integration of Bi 2 O 2 Se with a silicon photonic platform and are expected to accelerate the future use of integrated photodetectors in spectroscopy, sensing, and communication applications.

Although mesocrystals with ordered building units have great potential in many fields because of the large amount of organic molecules used as structure-directing agents during their synthesis process, severe matrix interference makes their surface-enhanced Raman scattering (SERS) properties rarely understood. Herein, a rapid (20 s) and green microwave synthetic route is developed for the 100 g scale preparation of plasmonic W 18 O 49 mesocrystals with no additives. The ultrathin (1.5 nm) and oxygen vacancy-rich W 18 O 49 nanowires as a building unit greatly improve the interface charge transfer, while the periodic mesocrystal structure significantly enhances the localized surface plasmon resonance effect and creates high-density electromagnetic hot spots among the nanowires. An outstanding enhancement factor of 1.2 × 10 7 and an ultralow detectable limit of 10 -11 M are achieved, and the single-molecule imaging is also realized on this mesocrystal-based SERS substrate. Moreover, the relative standard deviation of the fabricated large-area (2.2 cm 2 ) SERS substrate is only 6.8%.