Electrical behaviour of discontinuous silver films deposited on softened polyvinylpyridine substrates

Results of the investigations carried out on the electrical behaviour of discontinuous silver films deposited on poly(2-vinylpyridine) (PVP) coated substrates held at temperatures in the range 410-475 K in a vacuum of 8 × 10^-6 Torr are reported. Both the resistance immediately after deposition and the room temperature resistance show a regular dependence on thickness, for films deposited at a substrate temperature of 425 K. The films deposited at this temperature show almost zero temperature coefficient of resistance (TCR) near room temperature, whereas films deposited at higher temperatures show large negative TCR and the magnitude of TCR decreases with increasing thickness. The films show an irreversible increase of resistance during exposure to atmosphere beyond a pressure of about 5 × 10^-2 Torr. A film deposited on PVP held at room temperature is more sensitive to exposure. The reduced aging in vacuum following deposition and improved stability against exposure to atmosphere of the films deposited on PVP at 425 K, in comparison with the film deposited on a rigid substrate, suggest the formation of subsurface particulate silver films. This can account for the high resistance observed, even for a 2000 Å thick film deposited on softened PVP substrates.