Surface morphology and transport studies of epitaxial graphene on SiC( 000 1 ̲ )

• Published in: Physical review. B, Condensed matter and materials physics Vol. 83; no. 19
• Main Authors: Creeth, G. L., Strudwick, A. J., Sadowski, J. T., Marrows, C. H.
• Format: Journal Article
• Language: English
• Published: United States 31-12-2011
• Subjects: ANNEALING; COALESCENCE; COHERENCE LENGTH; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DIMENSIONS; ELECTRONS; GRAIN SIZE; MORPHOLOGY; PYROLYSIS; SILICON CARBIDES; TRANSPORT
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.83.195440

Annealing conditions are critical to the properties of epitaxial graphene formed by thermal decomposition of silicon carbide. Here, we report the evolution of coherent electronic transport with increasing anneal temperatures, combined with low energy electron micrographs of equivalent surfaces showing corresponding structural coherence. Ultrahigh vacuum conditions and temperatures in the range of 1250-1300 C produce granular films with a lateral grain size of {approx}20 nm, while temperatures of 1400 C or higher result in grains with progressively larger lateral dimensions in the micron range. Transport measurements show how the electronic coherence length increases as a result of the more coherent physical structure, with a crossover from two-dimensional variable range hopping to the weak localization regime. Here, we show that while the duration of the anneal affects coverage and clustering of grains, the size of individual grains is determined by anneal temperature, with evidence of coalescence of smaller grains into larger domains, suggesting that multistage anneals at different temperatures may yield high-quality graphene.