Large area controllable hexagonal close-packed single-crystalline metal nanocrystal arrays with localized surface plasmon resonance response

Abstract

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 × 40 μm2 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.