We study origin, parameter optimization, and thermodynamic efficiency of isothermalrocking ratchets based on fractional subdiffusion within a generalized non-MarkovianLangevin equation approach. A corresponding multi-dimensional Markovian embedding dynamicsis realized using a set of auxiliary Brownian particles elastically coupled to the centralBrownian particle (see video on the journal web site). We show that anomalous subdiffusivetransport emerges due to an interplay of nonlinear response and viscoelastic effects forfractional Brownian motion in periodic potentials with broken space-inversion symmetry anddriven by a time-periodic field. The anomalous transport becomes optimal for asubthreshold driving when the driving period matches a characteristic time scale ofinterwell transitions. It can also be optimized by varying temperature, amplitude ofperiodic potential and driving strength. The useful work done against a load shows aparabolic dependence on the load strength. It grows sublinearly with time and thecorresponding thermodynamic efficiency decays algebraically in time because the energysupplied by the driving field scales with time linearly. However, it compares well withthe efficiency of normal diffusion rocking ratchets on an appreciably long time scale.

We compare the deposition rate, hydrogen incorporation and optoelectronic properties of hydrogenated polymorphous silicon films produced either by the decomposition of silane-hydrogen or of silane-helium mixtures. Our results clearly show that He dilution allows to drastically reduce the RF power needed to achieve the same deposition rate as in the case of H2 dilution. Infrared spectroscopy and hydrogen effusion experiments show clear differences in the hydrogen bonding and content in both series of films. Interestingly, both He and hydrogen dilution result in films with improved transport properties, in particular the hole diffusion length, with respect to standard amorphous silicon. These results indicate that He dilution is a good alternative to H2 dilution to prepare intrinsic layers for solar cells.