(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
Figure 2: SEM micrographs of the cross section of (a) N0.001E0, (b) N0.001E5, (c) N0.001E10, (d) N0.01E0, (e) N0.01E5, (f) N0.01E10, (g) N0.1E0, (h) N0.1E5, and (i) N0.1E10 films.