Sputter coaters

After critical point drying, samples are sputter-coated with a thin layer of precious metal (gold, platinum) in the nanometer range through target ionization. The metal layer makes the samples conductive and results in high yields of secondary electrons in the SEM, giving rise to a better signal to noise ratio and generating a higher stability of the sample in the electron beam. The Balzers SCD 004 sputter coater holds up to 18 samples and has a fixed stage. The Polaron SC 7640 sputter coater accomodates 6 samples and is fitted with a rotating sample stage. Rotation of the sample during sputtering enables the deposition of a more uniform conductive layer, especially onto samples with a pronounced three-dimensional surface structure. In contrast to cryofixed samples, critcal point dried samples can be used several times and can be stored for extended periods of time.