Abstract
Micro four-point probes (M4PP) provide rapid and automated lithography-free transport properties of planar surfaces including two-dimensional materials. We perform sheet conductance wafer maps of graphene directly grown on a 100 mm diameter SiC wafer using a multiplexed seven-point probe with minor additional measurement time compared to a four-point probe. Comparing the results of three subprobes we find that compared to a single-probe result, our measurement yield increases from 72%–84% to 97%. The additional data allows for correlation analysis between adjacent subprobes, that must measure the same values in case the sample is uniform on the scale of the electrode pitch. We observe that the relative difference in measured sheet conductance between two adjacent subprobes increase in the transition between large and low conductance regions. We mapped sheet conductance of graphene as it changed over several weeks. Terahertz time-domain spectroscopy conductivity maps both before and after M4PP mapping showed no significant change due to M4PP measurement, with both methods showing the same qualitative changes over time.
Highlights
Graphene is an atomically-thin two-dimensional material [1,2,3] which has properties suitable for a large number of practical technologies from corrosion protection [4,5,6] to OLEDS [7,8,9] to sensors [10,11,12]
We perform sheet conductance wafer maps of graphene directly grown on a 100 mm diameter SiC wafer using a multiplexed seven-point probe with minor additional measurement time compared to a fourpoint probe
M4PP data from this wafer was compared with a Terahertz time-domain spectroscopy (THz-TDS) conductance map [28]
Summary
Graphene is an atomically-thin two-dimensional material [1,2,3] which has properties suitable for a large number of practical technologies from corrosion protection [4,5,6] to OLEDS [7,8,9] to sensors [10,11,12]. That the capability of large-scale growth [13,14,15], transfer [16,17,18], and lithography techniques [19, 20] of Nanotechnology 31 (2020) 225709 graphene are well established, methods for assessing the quality [21, 22] and homogeneity of wafer-scale graphene are required to mature graphene-based technologies. Finding accurate strategies to probe thin-film properties is important for future research into the optimisation and commercialisation of graphene These methods should not require any wafer dicing (so the characterized wafer can be further processed), or contact with liquids or polymers so to not change the properties of the material [29].
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