Aging and Field Effect Studies of Cu and Cu/Ag Composite Discontinuous Thin Films

Post‐deposition resistance changes and effect of applied field on discontinuous films of Cu and Cu/Ag composite films deposited on clean glass substrates at room temperature and at a pressure of 3 × 10−3 Pa are investigated. Earlier studies on elemental discontinuous films of Cu and Ag reveal that while Cu films stabilised quickly in vacuum, Ag films aged faster but are more resistant to atmospheric contaminants. It is expected that a composite film of Cu/Ag would not only be stable but resistant to attack by atmospheric gases as well. It is found that the composite film is not much stabler than the elemental Cu film indicating that the Ag deposited on the Cu film does not use the existing Cu islands as nucleation centres but deposits in the gaps. The func‐tional dependence of the normalised resistance on time is of the form In (R/R0) ∝ In (t) with the constant of proportionality being called the agglomeration rate. Mobility coalescence is assumed to be responsible for the resistance increase with the average inter‐island spacing increasing logarithmically with time. Field effect studies on the Cu and Cu/Ag films show that they are ohmic in nature upto a field of 2000 V/cm. Copyright © 1986 WILEY‐VCH Verlag GmbH & Co. KGaA