Ricerc@Sapienza

Cellular Automata are discrete--time dynamical systems on a
spatially extended discrete space which
provide paradigmatic examples of
nonlinear phenomena.
Their stochastic generalizations, i.e.,
Probabilistic Cellular Automata,
are discrete time Markov chains
on lattice with finite single--cell states whose
distinguishing feature is the \textit{parallel} character of the updating rule.
We review the some of the results obtained about the metastable
behavior of Probabilistic Cellular Automata and we try to

Recently a-SiOx:H has attracted interest in heterojunction solar cells fabrication, because of its effective crystalline silicon surface passivation and larger optical bandgap than a-Si:H. Both amorphous layers are commonly deposited by PECVD from silane dissociation in hydrogen dilution. to obtain a-SiOx:H film, CO2 as source of oxygen is added to gas mixture, that heavily modifies the film growth, the composition and hydrogen inclusion, which influence the passivation properties.

The adoption of a-SiOx:H films obtained by PECVD in heterojunction solar cells is a key to further increase their efficiency, because of its transparency in the UV with respect to the commonly used a-Si:H. At the same time this layer must guarantee high surface passivation of the c-Si to be suitable in high efficiency solar cell manufacturing. On the other hand the application of amorphous materials like a-Si:H and SiNx on the cell frontside expose them to the mostly energetic part of the sun spectrum, leading to a metastability of their passivation properties.