EQUIPMENT & ACCESSORIES CATALOG EDITION IV SPUTTER COATERS, SEM/TEM CARBON COATERS
Techniques and Applications
It was found that the resulting pale yellow solution had a pH of about 5, the same as the CO2-equilibrated tap water used for its preparation. It was unstable, losing activity and color after about two hours at room temperature.
A neutral mixture may be prepared by substituting pH 7 phosphate buffer (conveniently prepared from a BDH tablet) for water in the above dilution. However, all the tests to be described in the paper were conducted with the ordinary solution prepared with tap water.
It should be noted that calcium carbonate has a significant solubility in water. In nature, calcite microfossils are protected against percolating groundwater by the sacrificial dissolution of fossils above and around them. Once removed from this environment to the laboratory, such fossils should presumably be washed only with distilled water that has been allowed to stand in contact with CaCO (eg marble chips) and filtered. Otherwise needles and similar fine structures will be particularly at risk.
This equilibrated ‘hard’ water could be used to prepare and dilute the Farmer’s Reducer. A very brief final rinse in distilled water is probably permissible; the common practice of ‘soaking overnight’ is not.
Results — silver mirror on glass
A silver mirror was made by evaporating the metal on to a microscope slide cleaned with chromic acid. Sufficient was deposited to give a semi-transparent film: silvery when placed on a dark background and viewed by reflected light, but behaving as a blue filter when examined by transmitted light.
The coated glass slide was immersed in freshly- prepared Farmer’s Reducer. The silver was gently dissolved in a controlled manner, as shown by the gradual and uniform loss of color in transmitted light, until none remained after three minutes. No gas was evolved. It was decided that a 10 minute immersion should allow an ample margin to deal with specimens with convoluted surfaces. The reagent had no effect upon gold films. Alloys of silver and gold have not been investigated.
Magnification: Coating Time: Current Used:
No Coating 15,000 X
10 seconds 20 mA
100,000 X 10 seconds 20 mA
300,000 X 10 seconds 20 mA
Comparative Sputter Data Iridium and other materials
Samples were coated using an EMS 575X Sputter Coater and were examined using a Hitachi S-5200 Field Emission SEM.
Gold
Magnification: Coating Time: Current Used:
Gold/Palladium
15,000 X
10 seconds 20 mA
100,000 X 10 seconds 20 mA
300,000 X 10 seconds 20 mA
Magnification: Coating Time: Current Used:
Chromium
15,000 X
10 seconds 20 mA
100,000 X 10 seconds 20 mA
300,000 X 10 seconds 20 mA
Magnification: Coating Time: Current Used:
Iridium
15,000 X
30 seconds 100 mA
100,000 X 30 seconds 100 mA
300,000 X 30 seconds 100 mA
Magnification: Coating Time: Current Used:
Platinum
15,000 X N/A N/A
100,000 X N/A N/A
300,000 X N/A N/A
Magnification: Coating Time: Current Used:
15,000 X N/A N/A
100,000 X N/A N/A
300,000 X N/A N/A
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