Au nanocrystal array/silicon nanoantennas exhibiting wavelength-selective photocurrent enhancement were successfully fabricated by a facile and inexpensive method combining colloidal lithography (CL) and a metal-assisted chemical etching (MaCE) process. The localized surface plasmon resonance (LSPR) response and wavelength-selective photocurrent enhancement characteristics were achieved by tuning the depth of immersion of Au nanocrystal arrays in silicon through a MaCE process. The wavelength selectivity of photocurrent enhancement contributed by LSPR induced local field amplification was confirmed by simulated near-field distribution. In addition, it can be integrated to well-developed Si-based manufacturing process. These characteristics make Au nanocrystal array/Si nanoantennas promising as low power-consumption photoswitches and nano-optoelectronic and photonic communication devices.
We demonstrated large-area, high density, hexagonal close-packed, single crystalline metal (Au, Ag) nanocrystal arrays with controllable crystal sizes of tens of nanometers, center-to-center spacing and uniform size distribution by colloidal lithography and the surface energy driven dewetting process. Larger than 30 Â 40 mm 2 single superlattice domain metal nanocrystal arrays were formed on Si and can be transferred to flexible substrates, illustrating the versatility to realize metal nanocrystal arrays on various substrates. The large-area hexagonal close-packed metal (Au, Ag) nanocrystal arrays with various sizes and center-to-center spacings were prepared and manipulated by regulation of the thickness of metals and the size of colloidal spheres. Appropriate surface treatments and the metal deposition method were shown to be critical for obtaining metal nanocrystal arrays with uniform size and reduced crystal size. Localized surface plasmon resonance (LSPR) responses of these nanocrystal arrays were systematically measured and exhibited high consistency with simulation based on Mie theory, implying that the high controllability of the LSPR wavelength can be achieved by these methods. The process provides an inexpensive and easy route to fabricate a large-scale close-packed single crystalline metal nanocrystal array with controllable sizes compared to the e-beam lithography method for precise regulation of the LSPR wavelength and light scattering cross-sections. It exhibits excellent versatility and controllability to fabricate large-scale metal nanocrystal arrays with various sizes, compositions, morphologies and structures on different substrates. Single crystallinity and long-range order of metal nanocrystal arrays can be achieved to enhance LSPR performance and benefit directional propagation, which can lead to significant applications in surface-enhanced Raman scattering (SERS) based biosensors, nanoantennas and other plasmonic optoelectronics.
For future all-soluble organic thin film transistor (OTFT) applications, a new soluble n-type air-stable perylene diimide derivative semiconductor material with (trifluoromethyl)benzyl groups (TC-PDI-F) is synthesized. The film is formed by spin-coating in air and optimized for OTFT fabrications. The transistor characteristics and air-stability of the TC-PDI-F OTFTs is measured to investigate the feasibility of using solution-processed TC-PDI-F for future OTFT applications. For all-solution OTFT process applications, the transistor characteristics are demonstrated by using TC-PDI-F as an n-type semiconductor material and liquid-phase-deposited SiO(2) (LPD-SiO(2) ) as a gate dielectric material. All processes (except material synthesis and electrode deposition) and electrical measurements are conducted in air.
The wavelength of localized surface plasmon resonance (LSPR) peak can be specifically tuned by precise control of the diameter and intersphere spacing of hexagonal close-packed metal nanosphere arrays (MSA). Large-area hexagonal close-packed metal nanosphere arrays with controllable spherical diameter and intersphere spacing are fabricated. The resonant peak locations for the maximun absorption of the localized surface plasmon were systematically measured and exhibited strong dependency on the diameter and intersphere spacing. This work demonstrates not only an inexpensive and easy route to fabricate a large-scale close-packed metal nanosphere arrays with controllable sizes compared to that can be achieved by the e-beam lithography method but also a platform for biosensor and plasmonic waveguide applications using localized surface plasmon resonance, surface-enhanced Raman scattering.
Three-dimensional silicon phononic crystal comprising periodic hexagonal-close packed nanotubular structures was fabricated by metal nanosphere patterning and metal-assisted chemical etching. Hexagonal-close packed metal nanosphere arrays fabricated by colloidal lithography and metal dewetting process were well-defined on the surface of silicon as patterns with controllable nanosphere size and intersphere spacing. Metal-assisted chemical etching were consequently implemented by exposing patterned silicon to etching solution composed of H2O2, H2O and HF for several minutes to etch silicon. The diameter and intertube spacing of nanotubes of silicon phononic crystal can be precisely regulated by the metal nanosphere arrays pattern.These silicon phononic crystals exhibited excellent absorption and thermoelectric properties can be applied and integrated into solar cell and realized Si-based thermoelectric devices.
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