978568.fig.003a
(a)
978568.fig.003b
(b)
978568.fig.003c
(c)
978568.fig.003d
(d)
Figure 3: Images of the samples treated for 5 ((a) and (b)) and 20 ((c) and (d)) pulses observed under SEI ((a) and (c)) and BEI ((b) and (d)) conditions.