Quasi-free-standing epitaxial graphene on 4H-SiC(0001) as a two-dimensional reference standard for Kelvin Probe Force Microscopy.

Kelvin Probe Force Microscopy is a method to assess the contact potential difference between a sample and the probe tip. It remains a relative tool unless a reference standard with a known work function is applied, typically bulk gold or cleaved highly oriented pyrolytic graphite. In this report, we suggest a verifiable, two-dimensional standard in the form of a photolithographically patterned, wire-bonded structure manufactured in the technology of transfer-free p-type hydrogen-intercalated quasi-free-standing epitaxial Chemical Vapor Deposition graphene on semi-insulating high-purity nominally on-axis 4H-SiC(0001). The particular structure has its hole density p S = 1.61 × 1013 cm−2 measured through a classical Hall effect, its number of the graphene layers N = 1.74 extracted from the distribution of the ellipsometric angle Ψ , measured at the angle of incidence AOI = 50 ° and the wavelength λ = 490 nm, and its work function ϕ G R = 4.79 eV postulated by a Density Functional Theory model for the specific p S and N. Following the algorithm, the contact potential difference between the structure and a silicon tip, verified at Δ V G R − Si = 0. 64 V , ought to be associated with ϕ G R = 4.79 eV and applied as a precise reference value to calculate the work function of an arbitrary material. [Display omitted] • QFS graphene on SiC as a KPFM reference standard. • Electrically verifiable and updatable. • A likely complement to HOPG and bulk gold. [ABSTRACT FROM AUTHOR]