A lecturer has told me that one particular method of CNT synthesis on Si substrates makes use of aluminium across one pair of electrodes and iron across the other. The substrate and the electrodes are pumped down to a very high vacuum. The first set of electrodes pass current and the aluminium is vaporised and deposited onto the substrate. The same follows for the iron.
I understand why Fe is deposited. This is well written about.
Why is the aluminium deposited though?