Structural changes occurring during the stripping of thin films of silver, copper, gold and nickel from their substrates

Abstract

Thin films of silver, copper, gold and nickel (island, coalescence and channel stage) were evaporated in high and ultrahigh vacuum onto cleavage faces of NaCl, KCl, MgO and mica and were backed with a supporting layer of SiO or carbon. The films were stripped in water or acidic media and the resulting morphology and structure were examined by transmission electron microscopy and transmission electron diffraction. A close examination of the microstructure of the replicating film and a comparison with over-growths that had been prepared simultaneously but shadowed with platinum or Pt-C revealed that the original film structure is generally not retained during chemical detachment from the substrate. Inter alia, the contraction of particles, coalescence, agglomeration and a loss of particles were observed. These artefactual changes were examined in detail for different substrate-overgrowth combinations and were found to be particularly significant on silver films. The results are compared with those of other workers, and possible mechanisms for the formation of artefacts as well as the means of their prevention are discussed.