Fig. 1. Surface topographies under different scanning times. (a) 1 time; (b) 2 times; (c) 3 times; (d) small scan spacing and low energy; (e) excessive scanning spacing; (f) excessive scanning times

Fig. 2. Surface topographies of laser etched copper. (a) SEM of low magnification; (b) SEM of mastoid structure; (c) micro-nano structure of mastoid surface

Fig. 3. Surface topographies after thermal oxidation by water vapor and ethanol assisted annealing. (a) 500 mL/min dry air; (b) 300 mL/min water vapor; (c) 600 mL/min water vapor; (d) 900 mL/min water vapor; (e) 1200 mL/min water vapor; ethanol assisted annealing for (f) 5 min, (g) 10 min, and (h) 15 min

Fig. 4. Experimental results. EDS spectra of samples surfaces after (a) thermal oxidation and (b) ethanol assisted annealing; XRD patterns of sample surface after (c) thermal oxidation and (d) ethanol assisted annealing

Fig. 5. Water contact angle on red copper surface. (a) Relationship between water contact angle and water vapor flow; (b) relationship between water contact angle and placement time in laboratory environment