Signals of chaos in the transient current through As2S3(Ag) and As2Se3(Al) thin films

Abstract

The transient current through a sample of As<inf>2</inf>S<inf>3</inf>(Ag) and As<inf>2</inf>Se<inf>3</inf>(Al) glass substrate has been analyzed in order to study possible chaotic behavior using methodology similar to that in work on polymers [1,2]. Rescaled range analysis (R/S) shows the presence of two regimes of fractal behavior, one of which can be attributed to short time scale relaxation and the other can be attributed to long term chaotic behavior. The mutual information data indicates the necessity of noise reduction using a moving average. Extending the moving average window gives correspondingly large delay times as expected. The indicated delay time starts at 20s and grows up to 250s. The false nearest neighbor results also indicate a value around 10. A robust increase in the Lyapunov exponent stretching graphs confirm long term chaos; the result is not sensitive to the precise values of the delay time and embedding dimension. Possible relaxation mechanisms [3] in the short time range include parametrizations involving stretched exponential relaxation and logarithmic relaxation, the latter suggested by a proposal of Trachenko [4,5]. © 2020 Elsevier B.V., All rights reserved.