Slide 9 of 16
Notes:
The set-up of the metallization equipment is shown in this figure. Metal contacts with an area of 0.005 cm2 were deposited on the samples through a contact mask using a Veeco model V-300 vacuum system that obtained a vacuum of at approximately 10-6 torr. A boron nitride crucible heated with a tungsten basket heating-element was used to evaporate the Al for the contacts. Tungsten heating elements are a known source of sodium (Na+) contamination due to the out-gassing of impurities. This contamination was minimized by repeatedly out-gassing the crucible and heating element before a metallization was performed and not allowing the Al to come into contact with the tungsten filament.
