Among various 2D materials, graphene has become the focus of extensive research. Electrical characterisation of graphene such as measurement of work function, sheet resistance, carrier concentration and mobility in macro-, micro- and nano-scale as well as large-area mapping of electrical properties are essential factors in developing the new generation of graphene-based electronic devices.
In this study, by the combination of magneto-transport in the van der pauw geometry, tHz time-domain spectroscopy mapping and calibrated Kelvin probe force microscopy a new methodology in measurements of the electrical properties of graphene is developed. Das-Nano Onyx 2D materials quality-inspector system was applied for the THz-TDS measurement to generate maps of sheet resistance of a whole sample area in a contactless non-destructive measurement.
This figure shows the maps of the local sheet resistance obtained using the Onyx THz-TDS system. From the maps it is evident that the sheet resistance features some spatial inhomogeneities, which highlights the need for a weighted average in order to compare the values to the vdP method. Average conductance and resistance values extracted from the THz maps and their standard deviations are summarised in the Table.
Reference: C.Melios, et al. towards standardisation of contact and contactless electrical measurements of cVD graphene at the macro-, micro- and nano-scale. 2019