Preservation of Surface Conductivity and Dielectric Loss Tangent in Large‐Scale, Encapsulated Epitaxial Graphene Measured by Noncontact Microwave Cavity Perturbations

Abstract

Regarding the improvement of current quantized Hall resistance (QHR) standards, one promising avenue is the growth of homogeneous monolayer epitaxial graphene (EG). A clean and simple process was used to produce large, precise areas of EG. Properties like the surface conductivity and dielectric loss tangent remain unstable when EG is exposed to air due to doping from molecular adsorption. Experimental results are reported on the extraction of the surface conductivity and dielectric loss tangent from data taken with a non-contact resonance microwave cavity, assembled with an air-filled, standard R100 rectangular waveguide configuration. By using amorphous boron nitride (a-BN) as an encapsulation layer, stability of EG’s electrical properties under ambient laboratory conditions is greatly improved. Moreover, samples were exposed to a variety of environmental and chemical conditions. Both thicknesses of a-BN encapsulation thickness are sufficient to preserve surface conductivity and dielectric loss tangent to within 10 % of its previously-measured value, a result which has essential importance in the mass production of millimeter-scale graphene devices demonstrating electrical stability.

Hexagonal MoTe2 with Amorphous BN Passivation Layer for Improved Oxidation Resistance and Endurance of 2D Field Effect Transistors

“…While there were no systematic studies to determine a-BN inertness, the earlier explorations with a-BN/graphene heterostructures had shown a significant increase of mobility in graphene monolayers when it was sandwiched with a-BN, relating this to a-BN inertness, similar to monolayer thin h-BN 32 . Stabilization of charge transport characteristics of epitaxially grown graphene in air by the application of a capping a-BN layer was also reported 40 , 41 . We then reasonably expected a similar effect with MoTe 2 devices, and such is explored for the first time in this study at elevated temperatures in air.…”

Atypical quantized resistances in millimeter-scale epitaxial graphene p-n junctions

“…The growth of high-quality epitaxial graphene can be found in Refs. 9,13,22,36 EG is formed Si atoms sublimate from the silicon face of SiC. Samples were grown on square SiC chips diced from on-axis 4H-SiC(0001) semi-insulating wafers (CREE) [see notes].…”

“…20 EG pnJs can be utilized to circumvent most of the technical difficulties resulting from the use of metallic contacts and multiple device interconnections. Research in developing materials for gating and preserving properties of large devices has seen limited success with amorphous boron nitride, [21][22] atomicallylayered high-k dielectrics, [23][24][25][26] Parylene, [27][28][29] and hexagonal boron nitride, [30][31] whereas other materials have been more successful, such as (poly)-methyl methacrylate ((P)MMA), ZEP520A photoresist, tetrafluoro-tetracyanoquinodimethane (F4TCNQ), and chromium tricarbonyl. 16,[32][33] For millimeter-scale constructions, one major issue was fabricating correspondingly large pnJs.…”

Towards epitaxial graphene p-n junctions as electrically programmable quantum resistance standards

“…The methods for growing high quality epitaxial graphene are well-reported 5 , 6 , 11 , 36 . EG is formed by sublimating Si atoms from the silicon face of SiC as part of an annealing process.…”