Electrical Stabilization of Surface Resistivity in Epitaxial Graphene Systems by Amorphous Boron Nitride Encapsulation

Abstract

Homogeneous monolayer epitaxial graphene (EG) is an ideal candidate for the development of millimeter-sized devices with single-crystal domains. A clean fabrication process was used to produce EG-based devices, with n-type doping level of the order of 1012 cm−2. Generally, electrical properties of EG, such as longitudinal resistivity, remain unstable when devices are exposed to air due to adsorption of molecular dopants, whose presence shifts the carrier density close to the Dirac point (<1010 cm−2) or into the p-type regime. Here, we report experimental results on the use of amorphous boron nitride (a-BN) as an encapsulation layer, whereby EG can maintain its longitudinal resistivity and have its carrier density modulated. Furthermore, we exposed 12 devices to controlled temperatures of up to 85 °C and relative humidity of up to 85% and reported that an approximately 20 nm a-BN encapsulation thickness is sufficient to preserve their longitudinal resistivity to within 10% of the previously measured value. We monitored the electronic properties of our encapsulated and nonencapsulated EG samples by magnetotransport measurements, using a neodymium iron boron magnet. Our results have essential importance in the mass production of millimeter-scale graphene devices, with stable electrical properties.

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

“…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 grown EG was evaluated with confocal laser scanning and optical microscopy as an efficient way to identify large areas of successful growth 37 . Using photolithography, both the Hall bar geometry and the contact pads are fabricated in steps that are presented in detail in other works 5 , 38 . In summary, protective layers of Pd and Au are deposited on the EG to prevent organic contamination.…”