Deposition of Cubic Copper Nanoparticles on Silicon Laser-Induced Periodic Surface Structures via Reactive Laser Ablation in Liquid.

We report the deposition of cubic copper nanoparticles (Cu NPs) of varying size and particle density on silicon laser-induced periodic surface structures via reactive laser ablation in liquid (RLAL) using intense femtosecond laser pulses. Two syntheses were compared: (1) simultaneous deposition, wherein a silicon wafer was laser-processed in aqueous Cu(NO3)2 solution and (2) sequential deposition, wherein the silicon wafer was laser-processed in water and then exposed to aqueous Cu(NO3)2. Only simultaneous deposition resulted in high Cu loading and cubic Cu NPs deposited on the surface. The solution pH, Cu(NO3)2 concentration, and sample translation rate were varied to determine their effects on the size, morphology, and density of Cu NPs. Solution pH near ∼6.8 maximized Cu deposition. The Cu(NO3)2 concentration affected the Cu NP morphology but not the size or Cu loading. The sample translation rate most significantly affected the Cu loading, particle size, and particle density. The observed synthesis parameter dependence of these Cu NP properties resembles results by electrodeposition to grow Cu NPs on silicon surfaces, which suggests that Cu NP deposition by RLAL follows a mechanism similar to electrodeposition.