Monday, July 30, 2012

AuPd Coating Procedure Part 2: Pumping

With the sample stage height set, the samples in place, and the O-ring and chamber sealing surfaces carefully cleaned (and if needed lightly lubricated with vacuum grease)-- start pumping.

Turn the mains "A" on.  Look here if you can't find the main power switch.

Turn on the pump power by pressing "K".  Make sure "L", the pump half-speed setting, is NOT pushed in. The green LED's in the indicator "M" will start lighting. To make sure there is a good vacuum seal, trying lifting the sputter head upwards slightly. If it doesn't move-- then the chamber is sealed.  f one can lift it then there is a major leak. Turn the pump off using "K" and check for leaks.

Turn on the gauging using "H". As the system pumps one should see the pressure gauge drop on the scale "I". One is initially reading the Pirani gauge on the black scale. The indicator "J" will be off.

In time the pressure will drop below 10-3 mbar on the black scale and the gauges will switch. The indicator "J" will go on indicating that the scale "I" is reading the cold cathode gauge on the red scale.

Wait until the pressure reaches the desired base pressure. For best results, the base pressure should be < 10-4 mbar. The absolute base pressure is between 10-6 and 5x10-5 mbar. The time to reach the base pressure is determined by many factors including cleanliness while handling the components of the sputter coating (e.g. bare hands vs. gloves), the porosity of the samples (e.g. mesoporous silica), any water or solvents present in samples (e.g. clay minerals, sample mounting (e.g. Ag or C paints). An empty chamber should pump to 5x10-5 mbar in roughly 30-40 minutes.

This last photo shows the vacuum gauging at the highest base pressure recommended for AuPd sputter coating-- just above 10-4 mbar.

In summary:

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