Metal Evaporator

Every time I tell my friends about this tool, they are amazed. "What do you mean by 'metal evaporator' " they say. Well, it's as simple as it sounds... a tool that evaporates metal. The next question is "Why?". Well many jeweler or artists evaporate metals to give a nice looking coating to they're work. Me and my colleagues, however, use the tool to deposit thin metal films for electronics and research purposes. I won't go into the details though....

How the tool works is fairly simple. It's basically a giant metal incandescent light bulb (and if you are wondering, we do have a metal deposition tool that is like a giant florescent light bulb, but I won't go into that here). The metal chamber is evacuated to very high vacuum by a high speed vacuum pump. Inside the chamber is a tungsten filament on which we place chunks of the metal we want to evaporate. We then send a high electrical current through the coil heating it up and in turn heating up the metal on it. When it's hot enough, the metal melts and evaporates. In fact the metal doesn't have to melt to evaporate, but I don't have a good way to measure when this happens, so I just look for it to melt.

There are some more technical considerations with the tool, like valves, purging to open, cooling the pumps. These are solved in typical fashion for vacuum tools of this nature.

Now there is a window on the bottom, but as the metal evaporates, it would cover the glass. So I put an extension piece on the window and a small mirror in the chamber so I can see inside during the evaporation runs. Luckily, most of the metals simple make the mirror more reflective, so I rarely have to change or clean it.

So far the main metal I've evaporated is aluminum, since it is cheap, soft, and has a low melting point. I've evaporated gold, silver, and pentacene with success. Evaporating cobalt has been done, but it forms an alloy with the tungsten that melts at a lower temperature then cobalt itself. So everytime I do cobalt, I endup bring a hole in the filiment which I don't like. I was able to deposit nickel as well, but the temperatures needed pushed the limits of the tool. I tried titanium evapoaration, but couln't get it to go.