Abstract
As first recognized in 2010, epitaxial graphene on SiC(0001) provides a platform for quantized Hall resistance (QHR) metrology unmatched by other two-dimensional structures and materials. Here we report graphene parallel QHR arrays, with metrologically precise quantization near 1000 Ω. These arrays have tunable carrier densities, due to uniform epitaxial growth and chemical functionalization, allowing quantization at the robust ν = 2 filling factor in array devices at relative precision better than 10−8. Broad tunability of the carrier density also enables investigation of the ν = 6 plateau. Optimized networks of QHR devices described in this work suppress Ohmic contact resistance error using branched contacts and avoid crossover leakage with interconnections that are superconducting for quantizing magnetic fields up to 13.5 T. Our work enables more direct scaling of resistance for quantized values in arrays of arbitrary network geometry.
Highlights
The von Klitzing constant, RK = h/e2, is defined in the 2019 redefinition of the SI base units as a universal reference of electrical resistance [1], and it is accessed through the integer quantum Hall effect (QHE) [2]
Optimized networks of quantized Hall resistance (QHR) devices described in this work suppress Ohmic contact resistance error using branched contacts and avoid crossover leakage with interconnections that are superconducting for quantizing magnetic fields up to 13.5 T
A single device used as a quantized Hall resistance (QHR) standard can provide only one or two highly precise resistance plateaus
Summary
If the contact resistances rc are too large, some current could flow through the final Hall contacts; the error decreases by a factor ≈ (ρxx + rc)/RK for each added edge connection to a quantized 2DEG element [15,16] provided that the metallic reservoir contacts are well separated [17]. Before all measurements, these devices were functionalized using chemical treatment to obtain η6-coordination of Cr(CO) to EG [18,19]. Gentle heating at 40 ◦C–100 ◦C provides fine adjustment of the charge functionalization by removing weakly bound molecules adsorbed from the atmosphere
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