Acetone on Si(001) - an adsorption study for siliconbased molecular electronics

The ability to covalently attach organic molecules to semiconductor surfaces in a controllable and selective manner is currently receiving much attention due to the potential for creating novel molecular-electronic devices such as resonant tunneling diodes. Scanning tunnelling microscopy (STM) is ideally suited for such studies as it can provide information on the geometric and electronic structure of individual adsorbates on surfaces, and can also serve as an electrical contact to the molecule for conductance measurements. However, it has been reported several times that surface adsorbed organic molecules containing C=C double bonds are unstable when under the influence of the applied biases and currents of an STM tip. Here the authors use STM and density functional theory calculations to study the adsorption of acetone [(CH₃)₂CO] to the silicon (001) surface, and the stability of the resulting adsorbate structures. The authors show good agreement between experimental STM images, total energy DFT calculations and simulated STM images.