Preparation of indirect carbon films.
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Materials -
a. 300 or 400 mesh copper grids. (400M is stronger)
b. Mica sheets (from PELCO, INC.)
c. Edward's Vacuum Evaporator, using Indirect Film Holder (Ruben, G., 1984 "Parallax Measurements of single Molecules", J. of E.M. Technique 1:373-385)
d. LADD Cat. #30265 carbon rod point (5/16"{7.9 mm} X 0.045"{1.14 mm}); burning the full 7 mm of carbon will yield a 90-100 Å film.
Prepare Carbon Film. (Indirect Film Making):
1. Cut mica sheet in half (1.5" X 2"); cleave off a thin sheet and place clean side up in steel trough. Make sure the glass slides are in place on the side of the trough.
2. Center TOP SURFACE OF TROUGH under carbon rod by eye. Insert flat carbon rod on right, carbon point on left. Make sure there is enough contact tension to yield sparking down full length of rod. Evaporation assembly should be @17cm above the base plate (6 inches above the mica surface). YOU WANT THE TOP SURFACE OF THE TROUGH TO BE 2 1/2" for 2 sided holder; 3" for four sided) BELOW THE CARBON TIP Make sure 4 glass slides are in place. Make sure electrodes are connected.
3. Turn on power strip. Pump chamber for at least 1 hour. Pumping sequence is roughly this:
5min - 1/2 speed - 10-3
10 min - 3/4 speed - 3x10-4
15 min - full speed - 2x10-4
25 min - 5x10-5
40 min - 3x10-5
1 hour - 2x10-5
2 hours - 1x10-5 or into 10-6 range
4. Switch to C electrode and LT setting.
5. Bring up amperage slowly, until just sparking (@100 AMPS as shown on dial - meter does not work).
6. Back off slightly and fire off full length of carbon rod. This will take 30 seconds or so - burn slowly for best results.
7. Store carbon-coated mica in a glass dish in a vacuum desiccator.
8. Clean slotted glass shield (LADD, INC.) with water and detergent after two runs. Be sure to coat cleaned shiels with Bell Bright to prevent carbon buildup.
9. Turn off power strip.
10. Replace glass and plastic shields. Close top.
Placing films on grids:
1. Rinse clean grids in methanol.
2. Rinse with dH2O. Fill glass 100mm Petri-dish w dH2O & 5-7 drops of ETOH to reduce surface tension.
3. Cut mica sheet in half {1.5" X 1"}.
4. Cut square of #50(Q2) ashless filter paper that is slightly smaller than mica sheet. Place on top of small Teflon plate, at the bottom of the Petri dish.
5. Place grids on submerged filter paper - shiny side up - close together. Go across row by row with no overlap.
6. Slide carbon off mica (as with formvar slides) onto surface of water.
7. Slowly siphon off water with a 60-ml. syringe. Maneuver film over grids, using the flat Teflon paddle (cell scraper). Carefully remove excess water from carbon film (i.e. make sure film is adhered to filter paper, before moving).
8. Remove, let dry on filter paper and store in a desiccator since carbon films are very hygroscopic.