Monitoring of iodide titanium growth on tungsten substrates by electrical resistance measurements

An experimental apparatus has been designed to grow iodide titanium films on tungsten substrates of different geometries. The time-evolution of the deposited titanium mass has been determined considering the variation of the filament electrical resistance during the titanium deposition. To this aim, a phenomenological model has been developed based on the evolution of the filament geometry during its growth. This model provides a reliable relationship between the filament electrical resistance and the continuously deposited titanium mass. The model has been applied to both ribbon and wire tungsten filaments. The analysis of the experimental results shows that the titanium deposition rate is proportional to the surface area developed by the filament during its growth. This result suggests that the growth rate is controlled by the transport of gases in the vicinity of the filament.