AGING STUDIES ON DISCONTINUOUS SILVER FILMS IN ULTRAHIGH-VACUUM

The results of aging studies carried out on discontinuous silver films deposited on glass substrates held at room temperature in a vacuum of 2 x 10(-8) Torr are presented in this article. The films were prepare d by electron beam deposition at a rate of 0.2 Angstrom/s. Discontinuo us silver films show considerable aging for extended period even in a clean ultrahigh vacuum (UHV) obtained using a turbomolecular pump when the oxygen partial pressure is as low as 10(-11) Torr, thus ruling ou t the possibility of oxidation being responsible for the aging in thes e films. The coalescence rate values in UHV and in a vacuum of 2 x 10( -6) Torr obtained using an oil diffusion pump are nearly the same. Thi s indicates that the aging of island films is not due to oxidation, A film with an initial resistance of 2 M Ohm/square showed a drastic fal l in resistance after about 30 min of aging, This interesting disconti nuous-semicontinuous transition observed in a conservative system is a clear evidence for the mobility of islands. (C) 1998 Elsevier Science S.A. All rights reserved.