  We report on dynamic effects associated with thermally-annealing amorphous
indium-oxide films. In this process the resistance of a given sample may
decrease by several orders of magnitude at room-temperatures, while its
amorphous structure is preserved. The main effect of the process is
densification - increased system density. The study includes the evolution of
the system resistivity during and after the thermal-treatment, the changes in
the conductance-noise, and accompanying changes in the optical properties. The
sample resistance is used to monitor the system dynamics during the annealing
period as well as the relaxation that ensues after its termination. These
reveal slow processes that fit well a stretched-exponential law, a behavior
that is commonly observed in structural glasses. There is an intriguing
similarity between these effects and those obtained in high-pressure
densification experiments. Both protocols exhibit the "slow spring-back"
effect, a familiar response of memory-foams. A heuristic picture based on a
modified Lennard-Jones potential for the effective interparticle interaction is
argued to qualitatively account for these densification-rarefaction phenomena
in amorphous materials whether affected by thermal-treatment or by application
of high-pressure.
