MONITORING OF IODIDE TITANIUM GROWTH ON TUNGSTEN SUBSTRATES BY ELECTRICAL-RESISTANCE MEASUREMENTS

An experimental apparatus has been designed to grow iodide titanium fi lms on tungsten substrates of different geometries. The time-evolution of the deposited titanium mass has been determined considering the va riation of the filament electrical resistance during the titanium depo sition. To this aim, a phenomenological model has been developed based on the evolution of the filament geometry during its growth. This mod el provides a reliable relationship between the filament electrical re sistance and the continuously deposited titanium mass. The model has b een applied to both ribbon and wire tungsten filaments. The analysis o f 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. (C) 1998 Elsevier Science S.A. All rights reserved.