Graphene Research Support
Abstract
There was a steady increase in average flake size in the years following the initial isolation of monolayer grapheme in 2004, but even by 2008, flakes rarely exceeded 1000 sq microns. As part of the research for this grant, carefully analyzed the factors that affect flake size, including: graphite source (natural, HOPG, Kish), type of adhesive tape, number of cleaves, substrate material and roughness, substrate cleaning (sonication, piranha etch, oxygen plasma, etc.) and temperature. They found that the number of graphite cleaves and the substrate cleaning procedures were the most common factors that limited flake size. By cleaving only 5-10 times (typical number of cleaves in previous procedures was >20) and cleaning with oxygen plasma, we were able to routinely prepare flakes >100, 000 sq microns and occasionally >1 sq mm. With flakes more than 100 microns in diameter, a wider range of experiments became possible. Optical scanning measurements over large regions, ellipsometry, infra-red-spectroscopy and capacitance devices have yielded interesting results. Occasionally when preparing large flakes, air can get trapped between the substrate and the grapheme, forming bubbles. The shape of these bubbles can be controlled with a gate voltage, potentially allowing for grapheme-based adaptive focus lenses.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2012
- Accession Number
- ADA567505
Entities
People
- Craig Lang
- Da Jiang
- Peter Blake