Integration of hexagonal boron nitride with quasi-freestanding epitaxial graphene: toward wafer-scale, high-performance devices.

Hexagonal boron nitride (h-BN) is a promising dielectric material for graphene-based electronic devices. Here we investigate the potential of h-BN gate dielectrics, grown by chemical vapor deposition (CVD), for integration with quasi-freestanding epitaxial graphene (QFEG). We discuss the large scale growth of h-BN on copper foil via a catalytic thermal CVD process and the subsequent transfer of h-BN to a 75 mm QFEG wafer.

Characterization of graphene films and transistors grown on sapphire by metal-free chemical vapor deposition.

We present a novel method for the direct metal-free growth of graphene on sapphire that yields high quality films comparable to that of graphene grown on SiC by sublimation. Graphene is synthesized on sapphire via the simple decomposition of methane at 1425-1600 °C. Film quality was found to be a strong function of growth temperature.

Epitaxial graphene transistors: enhancing performance via hydrogen intercalation.

We directly demonstrate the importance of buffer elimination at the graphene/SiC(0001) interface for high frequency applications. Upon successful buffer elimination, carrier mobility increases from an average of 800 cm(2)/(V s) to >2000 cm(2)/(V s). Additionally, graphene transistor current saturation increases from 750 to >1300 mA/mm, and transconductance improves from 175 mS/mm to >400 mS.

Enhanced transport and transistor performance with oxide seeded high-κ gate dielectrics on wafer-scale epitaxial graphene.

We explore the effect of high-κ dielectric seed layer and overlayer on carrier transport in epitaxial graphene. We introduce a novel seeding technique for depositing dielectrics by atomic layer deposition that utilizes direct deposition of high-κ seed layers and can lead to an increase in Hall mobility up to 70% from as-grown. Additionally, high-κ seeded dielectrics are shown to produce superior transistor performance relative to low-κ seeded dielectrics and the presence of heterogeneous seed/overlayer structures is found to be detrimental to transistor performance, reducing effective mobility by 30-40%.

Epitaxial graphene materials integration: effects of dielectric overlayers on structural and electronic properties.

We present the integration of epitaxial graphene with thin film dielectric materials for the purpose of graphene transistor development. The impact on epitaxial graphene structural and electronic properties following deposition of Al(2)O(3), HfO(2), TiO(2), and Ta(2)O(5) varies based on the choice of dielectric and deposition parameters. Each dielectric film requires the use of a nucleation layer to ensure uniform, continuous coverage on the graphene surface.

Nucleation of epitaxial graphene on SiC(0001).

A promising route for the synthesis of large-area graphene, suitable for standard device fabrication techniques, is the sublimation of silicon from silicon carbide at elevated temperatures (>1200 degrees C). Previous reports suggest that graphene nucleates along the (110n) plane, known as terrace step edges, on the silicon carbide surface. However, to date, a fundamental understanding of the nucleation of graphene on silicon carbide is lacking.