Grid-specimen interactions : factors affecting copper nanocluster formation on polymer thin films

SUMMARY All transmission electron microscopy (TEM) studies require the use of grids to support thin films or sections of specimens within the microscope. These grids are presumed to remain inert during sample loading and analysis, an assumption which becomes questionable when on-the-grid processing methods are employed to probe the response of a specimen to a particular stimulus, such as temperature increase. Uniform dispersions of nanoclusters were observed to develop on and undergo chemical complexation with thin cast films of a poly(siloxaneimide) copolymer supported on various copper grids during thermal annealing at temperatures of up to 200°C. The thermal conditions which promoted nanocluster formation were investigated. Experiments designed to elucidate the mechanism by which these nanoclusters develop revealed that cuprous oxide (Cu2O) from the copper support grids is deposited on these imide-bearing films from the vapour phase.