  We report and classify the rich variety of patterns forming spontaneously in
the oxide layer during the oscillatory photoelectrodissolution of n-type doped
silicon electrodes under limited illumination. Remarkably, these patterns are
often comprised of several dynamical states coexisting on the electrode, such
as subharmonic phase clusters and spatio-temporal chaos, and include so-called
'chimera states'. The experiments suggest that the subharmonic phase clusters
emerge from a period doubling bifurcation which, upon further parameter
changes, evolve into classical phase clusters. Experimentally the occurrence of
the patterns is controlled via two coupling mechanisms: A linear global
coupling by an external resistor and a nonlinear coupling imposed on the system
by the limitation of the illumination.
