Abstract
Aluminum was deposited on epitaxial monolayer-grown graphene on SiC(0001). The effects of annealing up to 1200 °C on the surface and interface morphology, chemical composition, and electron band structure were analyzed in situ by synchrotron-based techniques at the MAX Laboratory. After heating at around 400 °C, Al islands or droplets are observed on the surface and the collected Si 2p, Al 2p, and C 1s core levels spectra indicate Al intercalation at the graphene SiC interface. Also, the original single π-band splits into two, indicating decoupling of the carbon buffer layer and the formation of a quasi-free-standing bilayer-like electronic structure. Further heating at higher temperatures from 700 to 900 °C yields additional chemical reactions. Broader core level spectra are then observed and clear changes in the π-bands near the Dirac point are detected. More electron doping was detected at this stage since one of the π-bands has shifted to about 1.1 eV below the Fermi level. Different ordered phases of (7 × 7), (4 × 4), (1 × 1)Al, and (1 × 1)G were also observed on the surface in this temperature range. The original single π-band was restored after heating at ~1200 °C, although an Al signal was still able to be detected.
Highlights
Graphene, one single layer of graphite, is one of the most promising candidate materials for future electronic devices [1, 2]
Our results show that no change in the electronic π-band structure and no chemical reaction occurred after Al deposition on graphene at room temperature
low energy electron microscopy (LEEM) shows changes of the surface morphology directly after Al deposition, as illustrated by the image in figure 1(d), which was collected at a field of view (FOV) of 25 μm
Summary
One single layer of graphite, is one of the most promising candidate materials for future electronic devices [1, 2]. Al is easy to use, abundant in nature and inexpensive It has, not yet been revealed if Al provides a good choice of contact material for graphene-based electronic devices. Single layer, (i.e., single π-band) electronics or bi-layer graphene (i.e., two π-bands) electronics are typically carefully selected for specific devices If this property can be changed just by varying the temperature by a few hundred degrees, the device may be unreliable. Further heating at temperatures from 700 °C to 1200 °C induced more changes in the chemical composition, and in the electronic band structure and graphene doping level concentration. These findings are presented and discussed below
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