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. 2021 May 3;11(5):1209. doi: 10.3390/nano11051209

Figure 9.

Figure 9

The SEM cross–section images of Sample IV after digital etching with 31.5% HNO3-dBOE q-ALE at (a) 40 cycles, (b) 100 cycles, (c) 200 cycles, and (d) 300 cycles.