1/f Noise During Thermal Treatment of Amorphous Films

Flicker noise is a sensitive tool for probing the dynamics of two-level systems. Herein, this technique is employed to study the dependence of conductance noise on disorder for two versions of amorphous indium oxide films. The disorder in these substances may be tuned by thermal treatment that is manifested by enhanced conductivity. Structural studies reveal that this is mainly due to densification of the material. A similar reduction of volume has been achieved in glasses when subjected to high pressures. Both protocols, pressure and heat treatment, initiate nonequilibrium state that slowly relaxes. This relaxation is reflected in the sample conductivity and its optical transmission as a monotonic change. The magnitude of 1/f noise during these events turns out to fluctuate appreciably following changes in the sample conductance caused by thermal treatment. This may overshadow the tendency of the noise level to increase with disorder. Possible reasons for the fluctuations of noise levels in highly disordered systems are discussed.