Parla con un Esperto

Hydrogen Flame Annealing

Keysight Technologies Au (111) substrates are high purity gold epitaxially grown onto green mica in a high vacuum. The resulting gold surface is 1500 angstroms thick and composed of flat Au (111) terraces up to 280,000 nm 2. Hydrogen flame annealing produces contaminant-free reconstructed Au (111) surfaces.

Safety considerations:

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:

  1. Pressurized H 2 gas cylinder
  2. Single stage high purity flow regulator
  3. Anti-backflash arrester
  4. Square quartz plate
  5. Small quartz piece (1 cm 2 )
  6. Goggles or safety glasses
  7. Torch: Quartz tube narrows to a fine tip with inner diameter less than 0.25 mm

Procedure

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 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 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 OVER HEAT THE FILM. The darker the room, lessens the chance of over heating and burring the sample.

Blow out the flame and turn off the regulator. Let the film cool off for a minute.

Safety reminders:

  • Be sure to wear goggles while annealing
  • Direct the flame away from yourself and anyone else
  • Do not ignite the flame before you turn off the lights
  • When done, blow out the flame, turn off the tank, vent the rest of the gas, and turn off the regulator.