Go and visit your customers.. they have your machines, and they will tell you what they need. a perfect and independent control of plasma density, ion bombardment energy, substrate temperature, electron temperature (plasma chemistry) and very large surfaces and very high deposition rates.. well the last two is what the bankers want.
the perfect microstructure of a-Si:H or uc-Si to almost avoid degradation is still not clear to my knowledge, despite the good progresses.