Electrical behaviour of discontinuous silver films deposited on softened polystyrene and poly (4-vinylpyridine) blends

Results of the studies carried out on the electrical behaviour of silver island films deposited on the blends of polystyrene (PS) and poly (4-vinylpyridine) (P4VP) are presented here. The substrates were held at 457 K, much above the glass transition temperature of both the polymers to ensure sufficient polymer fluidity during deposition, to obtain a sub-surface particulate film. A constant deposition rate of 0.4 nm/s was used throughout the study. Films on softened PS gives rise to a very high room temperature resistance approaching that of the substrate resistance due to the formation of a highly agglomerated structure. On the other hand, films on softened P4VP gives rise to a room temperature resistance in the range of a few tens to a few hundred MΩ/, which is desirable for device applications. The blends of PS and P4VP show room temperature resistances in the desirable range even at a PS/P4VP ratio of 75:25. The films show an increase in resistance when they are exposed to atmosphere. This is attributed to the oxidation of silver islands. The film resistances in the desired range could be obtained even after exposure to atmosphere up to a PS concentration of 50%.