Flame Annealing Kit
Supplied by user:
Hydrogen tank, gas regulator, flame arrestor and tubing.
Flamed gold (111) mica substrates have a number of applications in a large portion of AFM laboratories. Unfortunately, their shelf life is very short since they tend to contaminate quickly no matter how hard one tries to protect them and keep this from happening.
SPI Supplies attempts to ship only fresh substrates and when purchased from SPI Supplies, because of our high turnover, you are guaranteed to receive fresh uncontaminated substrates. But not everyone in the world is able to purchase fresh substrates (e.g. sitting on the shelf of a distributor) or the substrates might sit for longer than anticipated in their own laboratory. But if one is set up to re-flame their substrates, they can "bring them back to life" and remove the contamination that would otherwise render them useless. There is a point in time, however, after several months of storage, when no amount of flame annealing will restore the surface of the substrate to "fresh" condition.
If the surface is rough because the underlying substrate is rough, then no amount of annealing is going to help you. If it is rough because of foreign material or oxides (unlikely on a freshly made substrate), then the hydrogen anneal should help. If it is rough because of locally uneven rates of deposition, the hydrogen anneal is unlikely to help. The idea of hydrogen annealing is to clean the surface and encourage the formation of large crystals in the thin film; it is not a "reflowing" process which will even out irregularities in deposition.
Hydrogen Flame Annealing
The Au (111) substrates are high purity gold epitaxially grown onto green mica in a high vacuum. The resulting gold surface is 150 nm thick and composed of flat Au (111) terraces up to 280,000 nm2. Hydrogen flame annealing produces contaminant-free reconstructed Au (111) surfaces.
Hydrogen is a flammable gas that burns with oxygen to form water. The flame is bright and colorless. Make sure that all of the safety requirements are met before starting.
Tools and Materials required
Flame annealing kit
In order to make it easier for our customers to more easily set up to do their own flame annealing, we offer the SPI Supplies Brand Flame Annealing Kit.
A clean environment is required for proper annealing. Preferably, the annealing counter should be placed in a very clean room or flow hood. The gas cylinder should be mounted to the wall or counter, the backflash valve and regulator should be attached according to manufacturer instructions. The PTFE tubing should then be attached to the regulator and the quartz-tube torch.
Place the quartz plate on the counter, with the gold substrate on top. Make sure that the letters MI are facing down, so that you anneal the gold coated side. Place the small quartz piece on the edge of the substrate to hold it in place.
Adjust the flow regulator to let just enough hydrogen pass through so that it is audible. Note that you may not see a reading on your flow regulator. Turn off all the lights (the darker the room, the better). Light the torch and adjust so that the flame is about 4 cm long. Gently heat the quartz plate around the substrate to assure even heating. When water vapor no longer condenses on the quartz, then it has been heated enough.
Now, bring the flame tip to the film at about a 30 degree angle. Sweep back and forth (at approx. 1 Hz freq.) for 30 to 60 seconds, keeping the small flame spot on the film a dim orange color. The optimum brightness will depend on the lighting of the room. In a normally lit room, you should not see the film glow at all. In an extremely dark room, the spot will become much more distinct. Do not overheat the film. The darker the room, the less chance of over heating and burning the sample.
Blow out the flame and turn off the regulator. Let the film cool off for a minute.