Raman mapping and XPS spectra. Raman mapping of (a) 1,583-cm−1 peak and (b) 202-cm−1 peak. (c) XPS spectra of Ga2p and (d) XPS spectra of C1s. The black curve is the original data, and the red is the fitting curve. The pink, dark blue, and sky blue curves are the fitting peaks on 284.7, 285.7, and 286.2 eV, respectively.