## 3 Results and Discussion
The fitting results from the current-voltage characteristics of the GO sample in the N\({}_{2}\) ambient (not shown) indicate that the conduction mechanisms of the HRS and the LRS were both dominated \begin{table}
\begin{tabular}{c c c c} \hline
**Peak** & **Assignment** & **GO on SiO\({}_{2}\)** & **GO between Cu/SiO\({}_{2}\)** \\ \hline C-C & sp\({}^{2}\) carbon & 19.0\% & 51.8\% \\ C-C & sp\({}^{3}\) carbon & 20.5\% & 28.5\% \\ C-OH/C-O-C & hydroxyl/epoxide & 18.2\% & 5.1\% \\ C=O & carbonyl & 29.6\% & 5.5\% \\ O=C-OH & carboxyl & 12.7\% & 9.1\% \\ \hline \end{tabular}
\end{table} 
Table 1: The calculated proportion of C-containing components of the C1s spectra. Figure 3: (**a**) Resistive switching (RS) properties of the control and (**b**) GO samples in the N\({}_{2}\) ambient. LRS: low-resistance state; IRS: initial-resistance state; HRS: high-resistance state. by ohmic conduction. The temperature coefficient of the LRS resistance for the GO sample in the N\({}_{2}\) ambient was 4.0 \(\times\) 10\({}^{-3}\) K\({}^{-1}\) (not shown), which is close to the value of the Cu bulk. Therefore, the RS was dominated by the rupture and formation of Cu filaments. In the RS process, Cu ions were dissolved from the Cu electrode into the SiO\({}_{2}\) layer, and then Cu ions migrated to the Pt electrode and were reduced on the Pt electrode. Subsequently, the Cu filaments grew from the Pt electrode toward the Cu electrode; thus, the resistance state was switched from the IRS to the LRS [24]. However, the Cu ionization process must be assisted by H\({}_{2}\)O molecules [25]. Therefore, the control sample did not possess the RS property in the N\({}_{2}\) ambient. Figure 4 shows the cumulative probabilities of switching the parameters of the GO sample in the atmosphere and the N\({}_{2}\) ambient. Figure 4a indicates that the HRS/LRS ratios of the GO sample in the atmosphere and the N\({}_{2}\) ambient were 3176 and 4647, respectively. The HRS exhibited a higher dispersion in the N\({}_{2}\) ambient than in the atmosphere, whereas the LRS demonstrated similar values and dispersion in the two ambients. This is because the LRS resistance was dominated by the current compliance. Figure 4b indicates that the Reset voltages were almost the same in the two ambients, whereas the Set voltage in the N\({}_{2}\) ambient was larger than that in the atmosphere. In addition, the Set voltage exhibited a much larger dispersion in the N\({}_{2}\) ambient than in the atmosphere. Because the LRS resistance demonstrated more stability than the HRS resistance did, the Reset voltage was also more stable than the Set voltage was in the N\({}_{2}\) ambient. All switching parameters in the N\({}_{2}\) ambient exhibited a larger dispersion than those in the atmosphere, especially the HRS resistance and the Set voltage. Although the GO layer can assist the dissolution process of Cu ions into the SiO\({}_{2}\) layer in the N\({}_{2}\) ambient to enable RS, the dissolution process of Cu ions should be facilitated by the additional O\({}_{2}\) and H\({}_{2}\)O molecules in the atmosphere [25]. The GO sample would then easily form Cu conducting filaments in the atmosphere. Therefore, the GO sample had a lower Set voltage in the atmosphere than in the N\({}_{2}\) ambient. Fewer possible paths were formed and can be selected for successive RS cycles, which reduced the switching dispersion [12]. Different statuses of oxygen functional groups within the GO layer [26] would cause different statuses of the Cu\({}_{x}\)O interface. More oxygen functional groups within the GO layer would lead to a thicker Cu\({}_{x}\)O layer. However, a thicker Cu\({}_{x}\)O layer might retard the migration of Cu ions and a thinner Cu\({}_{x}\)O layer might not assist Cu dissolution effectively. Therefore, an optimized Cu\({}_{x}\)O thickness within the GO sample would have a better RS property. Figure 5 demonstrates that the GO sample can be reversibly switched in the atmosphere and the N\({}_{2}\) ambient for more than 3000 cycles.