Growth evolution and infrared response of thermally dewetted Au nano-structures for bolometric applications

This paper discusses the growth and characterization of thermally dewetted gold nanostructures for enhanced infrared absorption in bolometer applications. The Au nanostructures are fabricated by solid-state dewetting of ultrathin (18 nm) Au film on Si substrate. The duration of dewetting is varied from 1 min to 30 min. The Au film exhibited the highest X-ray diffraction (XRD) peak intensity along the (111) plane; while the Au nanostructure showed the rising XRD peak along the (220) plane with the dewetting duration. The dewetting process also yielded grain growth and recrystallization of Au nanostructure. The effect of the dewetting on surface morphologies of the Au nanostructure is studied. The Au nanostructures exhibited broadband infrared absorption in the 500–6500 cm−1 range. The sample dewetted for 10 min exhibited up to 200% enhanced absorbance (with respect to the silicon substrate) in the IR range due to the well-suited dimensions of the nanostructures. The hypothesis is also substantiated by examining the plasmonic response of the nanostructure by simulation. [Display omitted] •Au nanostructures showing improved (upto 200% w.r.t. Si) broadband IR absorption.•Thermal dewetting (duration: 1–30 min) of ultrathin (20 nm) Au films.•Structural and morphological studies of the Au nanostructure.•Plasmonic response simulated to validate the measured absorption spectra.•Concept of Au nanostructure for MEMS bolometer application is proposed.