ABSTRACT
A copper sample with a size of 10 mm × 10 mm × 1 mm is cleaned in an ultrasonic bath with acetone for 30 minutes and then rinsed by using deionized water. The cleaned Cu wafer is fixed on the six-axis motion stage. The fs laser is incident normally to the Cu surface and this is achieved by using a plano-convex lens (f = 100 mm) with a spot size of ∼30 μm. The total power of the fs laser used to process is 100 mW. After processing, the morphologies of the processed Cu wafer are characterized by using Scanning Electron Microscopy (SEM) and its superhydrophobicity is measured by using an optical contact angle measuring device. And then, the nanostructured Cu sample is immersed in Au nanoparticle colloids for assembly. Rhodamine 6G (R6G) with the concentration of 10−7 M is employed for the Raman signal detection. Raman spectra are obtained by using a Ramanscope (inVia, Reflex, Reinshaw) with an exciting power of 6 mW, a wavelength of 632.8 nm, and a 50 × objective.
