Hydrogenated microcrystalline silicon (µc-Si:H) is important in thin-film silicon solar technology where it is combined with amorphous silicon (a-Si:H) in tandem cells for enhanced light absorption. However, efficient light absorption requires thick (>1 µm) µc-Si:H films compared to thin a-Si:H (~350 nm). Since reduced absorber thickness is desired, the potential of light management, typically induced by texture-etched transparent conductive oxides (TCO), has been explored, demonstrating a strong dependence of absorber layer quality on TCO chemical nature and morphology. Generally, electrical, optical and structural properties require optimization. Due to parameter interdependence, nano-imprint lithography (NIL) was introduced to decouple electrical/optical and structural properties by inducing texture on glass prior to TCO deposition, allowing independent optimization of light diffraction and electrical/optical requirements. The potential of NIL textures has been demonstrated in this respect. However, such novel morphologies (periodic/random) impact absorber layer quality. Therefore, the nucleation of µc-Si:H thin films (~100 nm), deposited under high power-high pressure conditions in a capacitively coupled plasma reactor, has been studied on various NIL textured substrates. To replicate a solar cell structure, NIL textured and flat glass have been coated with ~500 nm magnetron sputtered aluminum doped zinc oxide (AZO). Characterization through Raman spectroscopy and crystal grain analysis has been performed. For flat glass, the crystalline volume fraction (X_c) increased a factor 2 upon AZO addition joined by a narrower phase transition. This was related to a different microstructure evolution. Introducing a NIL texture increased nucleation delay on randomly textured compared to periodically textured substrates. Since nucleation depends on process conditions, i.e. silane flow rate (Φ_SiH4), the role of ions and radicals is considered a determining factor. A reduced Φ_SiH4 enhances the ion-to-growth flux ratio and ion energy, promoting surface diffusion^[1]. However, on rough morphologies the ion contribution per unit area is reduced, therefore reducing X_c on NIL substrates. When shifting to the phase transition, preferential etching of a-Si:H by atomic hydrogen dominates while the ion contribution is reduced. This is confirmed by the microstructure parameter (R*) experiencing a transition from void-rich to (di)vacancy-dominated films. Furthermore, a direct correlation of R* and X_c was obtained. The insights obtained as such directly impact process control when dealing with challenging morphologies.

^[1] J. Palmans et al., J. Phys. D: Appl. Phys.47 (2014)