Fig. 1. Diagram of the experimental setup. The insert is diagram of the process method

Fig. 2. SEM images on acceptor of 20 nm copper thin film under different powers. (a) 125 mW; (b) 375 mW; (c) 500 mW; (d) 875 mW

Fig. 3. (a) SEM image and (b) detail enlarged image on acceptor under the power of 500 mW

Fig. 4. SEM images of nanostructures of 20 nm copper thin film under different powers. (a) 125 mW; (b) 250 mW; (c) 500 mW; (d) 750 mW

Fig. 5. SEM images of nanostructures of 40 nm copper thin film under different powers. (a) 125 mW; (b) 250 mW; (c) 375 mW; (d) 500 mW

Fig. 6. SEM images of nanostructures of 40 nm copper thin film under the power of 500 mW. (a) Edge of the acceptor area; (b) middle of the acceptor area

Fig. 7. SEM image of nanostructures of 200 nm copper thin film under the power of 250 mW