High resolution real and reciprocal space photoelectron emission microscopy on heterogeneous Graphene/SiC(000-1)

ROM 2012-4
Author: Nicholas BARRETT (1), Konrad WINKLER (2), Burkhard KROEMKER (2), Edward CONRAD (3)
Institute: ( 1) IRAMIS, Saclay, France, (2) Omicron NanoTechnology, Germany, (3) GeorgiaTech, Atlanta, GE, United States
Instrument: NanoESCA

We present energy filtered electron emission spectromicroscopy with high spatial and wave-vector resolution on few-layer epitaxial graphene on SiC(000-1) grown by furnace annealing.
Conventional electron spectroscopy methods are limited in providing simultaneous real and reciprocal or k-space information from small areas under laboratory conditions. Therefore, the characterization of materials with only micron scale sample homogeneity such as epitaxially grown graphene requires new instrumentation. Recent improvements in aberration compensated energy-filtered photoelectron emission microscopy (NanoESCA, developed in close co-operation by Omicron NanoTechnology and FOCUS GmbH) can overcome the known limitations in both synchrotron and laboratory environments.
Here we report 2D maps of the k-parallel π-π ∗ band dispersion in micron-scale regions and correlate them with spatially resolved chemical information on the same regions. Only the combination of high lateral, high energy, high k-resolution and controlled switching between real space and k-space allows detailed understanding of micron size sample sites with 1–3 layers graphene.
The experiments underline the importance of simultaneous lateral, wave vector and spectroscopic resolution on the scale of future electronic devices in order to precisely characterize the transport properties and band alignments.