The support consisted of a thin alumina film grown on a Ta (110) single crystal, which was mounted via heater wires to a cryostat allowing temperature control in the 120 K to 1000 K range. For cleaning, the sample could be heated by electron bombardment; from behind the cryostat, a filament allowed bombardment of electrons to the single crystal, that could heat the crystal to over 2100 K. At that temperature, the alumina film and any deposited clusters desorb, and the sample was found to be clean by X-ray photoelectron spectroscopy (XPS).