Solitary current-density patterns in thin ZnS:Mn films

We experimentally investigate pattern formation phenomena in the electroluminescence of ac-driven ZnS:Mn thin films. Under suitable driving conditions, certain samples show a broad spectrum of patterns, which ranges from stationary filamentary distributions to traveling fronts and pulses. We present a survey of the bifurcation scenarios, choosing the frequency and amplitude of the driving voltage as bifurcation parameters. Moreover, we investigate the influence of the temperature on the dissipative current and pattern formation. The experimental results are used to identify activating and inhibiting processes, and a pattern formation mechanism based on autocatalysis and lateral inhibition is suggested.