Fig. 3. In situ mechanical cleaning approach in the TEM.

a TEM image of a graphene membrane with residual contamination. b, c Consecutive cleaning from both sides results in an atomically clean membrane (d). HRTEM (e) confirms the level of cleanliness and pristine state of the graphene. The FFT (inset) confirms to the graphene structure. Only intrinsic defects such as divacancies (f) are found on the membrane with no additional defects being introduced by the cleaning method. g EELS spectra of as-prepared and (SEM) cleaned graphene membranes. The oxygen signal from the PMMA residuals disappears after cleaning. Moreover, the plasmon loss peak decreases in intensity and shifts to lower energies.