Large-scale fabrication and observation of self-assembled silica nanospheres on GaN

A simple and efficient spin coating method for large-scale fabrication of self-assembled silica nanospheres on Gallium Nitride (GaN) substrates is reported. A Matlab-based Nomarski image processing method was developed to calculate the surface coverage of silica nanospheres on GaN surface and allows large-scale observation of two-dimensional (2D) and three-dimensional (3D) ordering of silica nanospheres on GaN. With Nomarski image processing and a scanning electron microscope (SEM), the optimal spin coating condition and sodium dodecyl sulfate (SDS) concentration were investigated. A ∼70% monolayer coverage of silica nanospheres was demonstrated on GaN substrates ranging in size from 10 mm square to 51 mm (2″) diameter. This paper discusses the details of the spin coating process parameters and SDS concentration vs. surface coverage of silica nanospheres on GaN substrate, along with a theoretical evaluation of the effects of nanosphere patterning on photonic crystals fabricated using this method.

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► A spin coating technique has been used to fabricate the large-area self-assembled monolayer of silica nanospheres on GaN.
► The authors developed a Matlab-based Nomarski image processing for large-scale observation of silica nanosphere on GaN.
► 2D ordering of silica nanospheres was obtained with the optimal spin coating condition and the use of SDS as a surfactant.
► A theoretical calculation using FDTD has examined the effects of nanosphere patterning on PhC fabricated using this method.