Procedure for Cleaning the $Cu(001)$ Surface

The purpose of this procedure is to produce a sample surface which is free of contaminants, and has a well-ordered crystalline structure.

1. The vacuum chamber's ion pump (figure 4.1) was isolated from the chamber using a gate valve, and switched off, to protect the pump from saturation with argon.
2. The sample was placed, according to the procedure in appendix A.1, in a position which had previously been determined as being in the path of the ion beam from a commercial argon ion sputtering gun (section 4.2,) with the sample's exposed $(001)$ face toward the gun.
3. The ion energy from the ion gun was set to $(2.8\pm{}0.029)\,\mathrm{keV}$.
4. The gas inlet valve of the ion gun was opened until the pressure in the chamber, as revealed by the ion gauge (figure 4.1,) was $(875\pm{}110)\,\mathrm{pbar}$.
5. On some occasions, a visual check was made for a blue glow at the sample surface, which would confirm that the ion beam was reaching the surface.
6. The sputtering process was allowed to continue for $(59\pm{}9)\,\mathrm{minutes}$.
7. The gas inlet valve of the ion gun was closed.
8. The power supply that provided the ion energy was switched off.
9. When the pressure in the chamber, as revealed by the ion gauge (figure 4.1,) had dropped to less than $1\,\mathrm{pbar}$, the ion pump was switched on.
10. The valve between the ion pump and the chamber was opened, and the ion pump was switched on.
11. A current of $(8.75\pm{}0.04)\,\mathrm{A}$, through the sample heating filament (figure 4.5,) was switched on.
12. When the sample temperature, as revealed by the sample thermocouple, exceeded $773\,\mathrm{K}$, the current through the sample heating filament was switched off.