Figure 4

FESEM images of series C: (a) NWs-a grown on Si wafer without HF treatment, (b) NWs-b grown on Si wafer dipped in HF for 20min.

FESEM images of series C: (a) NWs-a grown on Si wafer without HF treatment, (b) NWs-b grown on Si wafer dipped in HF for 20min.