Resonance colors in an amorphous-Si thin layer irradiated by an ultraviolet nanosecond laser

Abstract

The optical resonances of nanoparticles have drawn considerable attention in academia and industry; however, the formation of uniform nanoparticles has been challenging, hindering their application. Herein, we propose that reflective-type color filters can be achieved using the optical resonance effect arising from Si nanoparticles created on an amorphous Si thin film via laser irradiation. Multiple equally spaced irradiations of an amorphous-Si surface by a Gaussian laser beam created Si nanoparticles with sizes of 100–200 nm at laser fluences in the range of 150–200 mJ/cm2. Furthermore, we demonstrated that the resonance colors could be tuned to red, green, and blue by adjusting the laser fluence and scan speed. The optical properties of the nanoparticles were analyzed using dark-field microscopy, scanning electron microscopy, and transmission electron microscopy. According to the measured nanoparticle geometries and spectral data, the Si nanoparticles are spheroidal shapes embedded in the Si layer, and simulations indicate that the resonance colors originate from electric and magnetic dipoles inside the Si nanoparticles. The results could inform the fabrication of color filters in reflective display device or sensor applications through a simple laser scanning process.