Supplementary Information

Chemical reduction dependent dielectric properties and

dielectric loss mechanism of reduced graphene oxide

Fig. S1 The SEM of (a) ultrasonic treated GO; (b) untreated rGO-90; (c) ultrasonic

treated rGO-90 and (d) the red square area in (c) in larger magnification.

Fig.S2 The TEM images of rGO-60.

Fig.S3 XRD (a) and Raman (b) patterns of rGO-120, rGO-140 and rGO-160.

Fig.S4 C1s peak XPS spectra of rGO-120 (a), rGO-140 (b) and rGO-160 (c). The

peaks 1, 2, 3 and 4 correspond to C=C/C-C in aromatic, C-O (epoxy and

hydroxyl), C=O (carbonyl) and O-C=O (carboxyl) groups, respectively