Thin Film Substrates
Nickel Evaporation Material is a hard, lustrous, silvery-white metal. It has a density of 8.91 g/cc, a melting point of 1,453¡ãC, and a vapor pressure of 10-4 Torr at 1,262¡ãC. Its key characteristics are malleability, ductility, and ferromagnetism and its polished surface resists tarnishing when exposed to air. It is the second most abundant element in earth's core next to iron. It is mainly used to make stainless steel, coins, and batteries. It can also be found in jewelry, but its presence has decreased due to skin allergies. When evaporated in vacuum, nickel can form a decorative coating on ceramic surfaces or a solder layer in circuit device fabrication. It is often sputtered to form layers in the production of magnetic storage media, fuel cells, and sens.
Thermally evaporating nickel is very difficult. Like titanium, it has a strong tendency to alloy with refractory metals. Attempting to thermally evaporate nickel out of a tungsten boat has proven futile. As the boat heats up and the nickel melts, it alloys with the boat, causing it to become brittle and crack shortly after exposure to the liquid nickel. Therefore, deposition is very limited.
we recommend an alumina coated, tungsten dimpled boat. The alumina acts as a barrier between the nickel and the tungsten, thus prolonging the life of the boat and increasing the amount of nickel deposition. Instead of wetting the boat, the nickel will form a ball on top of the alumina coating once it melts. Only four ⅛” diameter x ⅛” long pellets can be loaded safely into this boat at one time. These boats will fail often, lasting approximately 1-3 runs. Due to alumina’s limited heat conduction abilities, more power will be required to achieve evaporation.
The alternative option would be to use an Al2O3 crucible with a crucible heater. The problem is that it is very difficult to get to high enough temperatures to deposit the nickel. Crucibles rely on external heating and there is only so much power that can be applied in order to raise the temperature to achieve deposition.