This paper reports the development of a VHF PECVD process at 40.68 MHz for deposition of device-grade nc-Si:H. It
further reports the evaluation of textured ZnO:Al films produced by hollow cathode sputtering as regards their suitability
to serve as a TCO substrate for a-Si:H / nc-Si:H tandem device fabrication. The tandem devices were produced using an
established VHF PECVD process at 100 MHz. Both VHF processes are capable of producing similar nc-Si:H material
based on their analysis using micro-Raman spectroscopy. For the tandem junction devices, a peak in device efficiency
was obtained at a Raman crystalline fraction of 50-52 % and a microstructure parameter of 0.60-0.68. A best tandem
cell efficiency of 9.9% was achieved on HC ZnO compared to 11.3% on a reference Type-U SnO<sub>2</sub> substrate.
We report the catalyst-free growth of ZnO nanotips by metalorganic chemical vapor deposition (MOCVD) on various substrates, including c-sapphire, (100) Si, titanium, glass and SiO<sub>2</sub>. Structural, optical, and electrical properties of ZnO nanotips are investigated. ZnO nanotips are found to be single crystalline and oriented along the c-axis normal to the growth plane. The nanotips exhibit dominant free excitonic transition and enhanced luminescence efficiency with negligible deep-level emission. Controllable <i>in situ</i> Ga doping during MOCVD growth reduces the resistivity of ZnO nanotips. Selective growth of ZnO nanotips has been achieved on patterned Ti/r-Al<sub>2</sub>O<sub>3</sub>, SiO<sub>2</sub>/r-Al<sub>2</sub>O<sub>3</sub>, and silicon-on-sapphire (SOS) substrates. It provides the potential to integrate ZnO nanotips and ZnO epitaxial films on a single patterned substrate for various device applications.