September 17, 2009
Graphene and gallium arsenide
PTB Physikalisch-Technische Bundesanstalt has for the first time made graphene visible on gallium arsenide.
Scientists of the Physikalisch-Technische Bundesanstalt (PTB) have now, with the aid of a special design, succeeded in making graphene visible on gallium arsenide. Previously it has only been possible on silicon oxide. Now that they are able to view with a light optical microscope the graphene layer, which is thinner than one thousandth of a light wavelength, the researchers want to measure the electrical properties of their new material combination.
They use the principle of the anti-reflective layer: If on a material one superimposes a very thin, nearly transparent layer of another material, then the reflectivity of the lower layer changes clearly visibly. In order to make their lower layer of gallium arsenide (plus graphene atomic layer) visible, the PTB physicists chose aluminium arsenide (AlAs). However, it is so similar to gallium arsenide (GaAs) in its optical properties that they had to employ a few tricks: They vapour-coated not only one, but rather several wafer-thin layers.
Applied Physics Letters : Graphene on gallium arsenide: Engineering the visibility