705803.fig.004a
(a)
705803.fig.004b
(b)
705803.fig.004c
(c)
705803.fig.004d
(d)
Figure 4: I-V curves of pure and Co-doped ZnO films. (a) 5 at % Co-doped ZnO film, (b) 0% and 2 at % Co-doped ZnO films, (c) switching cycling test of 5 at % Co-doped ZnO film, and (d) the evolution of resistance of HRS and LRS over 4000 cycles of 5 at % Co-doped ZnO film.