The chamber (figure 4.2) contains an argon ion sputtering gun, for use in cleaning the surface of the copper crystal. The principles of this device are shown in figure 4.6.
The argon ion beam has a cleaning effect on the sample surface by removing a surface layer. The surface layer removal proceeds [76] by surface atoms and molecules, which are struck by argon ions, recoiling into the bulk of the sample. The elastic response of the bulk of the sample then expels the surface atoms and molecules.As well as removing surface impurities, the author expects the sputtering process to have removed the surface layer of amorphous copper, which is [77] likely to have formed during the polishing of the surface that took place, when the copper crystal was temporarily removed from the vacuum chamber, between the experiments in section 5.4 and those in section 5.5.
The gun was purchased commercially by the author's predecessors, and is described in more detail in its manual [78].
