The PE-CVD is a unique technique for thin film deposition, since it provides a good control over several parameters (time, plasma power and reactive gas composition) and therefore over the properties of the resulting films. In addition PE-CVD processes show a high reproducibility and they are scalable for large area productions. It finds applications in growth and processing of nano-materials, such as semiconductor thin films or carbon structures like graphene, carbon nanotubes (CNT), or DLC. Since the PE-CVD is a low temperature process it is possible to deposit under mild conditions onto sensitive materials like polymers.
In this study, we have focused on Interfacial modification of α-metal oxide multilayer photoanodes deposited by plasma enhanced chemical vapor deposition (PE-CVD). Different mechanisms such as heterostructuring (Fe2O3//TiO2), nano-structuring, patterning of multilayering with different structure (bar structure or line structure) or graphene supporting were examined in this study. The bilayer electrode exhibited enhanced PEC responses in terms of a lower onset potential and a higher photocurrent density when compared to the single layer α-Fe2O3 electrode. This enhancement was observed to be due to synergistic light absorption with the bilayer electrode, although charge carrier recombination occurred faster due to interfacial defect states. The incorporation of a graphene layer between the α-Fe2O3/TiO2 double layer and the FTO substrate resulted in a doubling of the photocurrent, but lead to a loss of the synergistic effect between the two active metal oxide layers. However, depositing the graphene between the two metal oxide layers resulted in an even higher photocurrent, while retaining the enhanced onset potential of the double layer electrode. This enhancement was observed to be due to either the passivation of the oxide defect states or enhancement of the charge transfer between the two oxide layers.