Figure 4: Top view of SEM observation of silicon nanowires (SiNWs) for Cu treated samples. (a, b) 1 hour etching having concentration of Cu(NO3)2 is 0.02 M. (c-f) 2 hours etching using concentration 0.05 M with different magnification. (g-h) Planer SEM micrograph of SiNWs array for Cu treated sample with 1 hour etching time and 0.02 M Cu(NO3)2.