Histogram method for reliable thickness measurements of graphene films using atomic force microscopy (AFM)

Atomic force microscopy (AFM) is a commonly used technique for graphene thickness measurement. However, due to surface roughness caused by graphene itself and variation introduced in AFM measurement, graphene thickness is difficult to be accurately determined by AFM. In this paper, a histogram method was used for reliable measurements of graphene thickness using AFM. The influences of various measurement parameters in AFM analysis were investigated. The experimental results indicate that significant deviation can be introduced using various order of flatten and improperly selected measurement parameters including amplitude setpoint and drive amplitude. At amplitude setpoint of 100 mV and drive amplitude of 100 mV, thickness of 1 layer (1L), 2 layers (2L) and 4 layers (4L) graphene were measured. The height differences for 1L, 2L and 4L were 1.51 ± 0.16 nm, 1.92 ± 0.13 nm and 2.73 ± 0.10 nm, respectively. By comparing these values, thickness of single layer graphene can be accurately determined to be 0.41 ± 0.09 nm.