Dynamics and control of thin film growth process from a multicomponent gas

Abstract

The control of a model system describing thin film growth processes from a multicomponent gas with chemical reactions occurring between components of source phase is studied. It is shown that condensation of thin films may be realized by different ways. In particular, for a low rate of particles arriving on a substrate the stable condensation mode occurs and any deviations from equilibrium are dumped. For a medium arrival rate, phase transitions take place in the oscillation mode (stable limit cycle). For a large arrival rate the stable limit cycle is destroyed and new phase condensation takes place in saw-tooth (accumulative) mode. A method of adaptive control of this oscillatory process - by varying the external parameters - is described based on recursive goal inequalities and an input - output linearized Poincaré map. The controlled system behaviour is analysed by means of computer simulations. It is found that the system being investigated has a peculiar memory because film condensation occurs in a different way for the same parameters but with differences in prehistory. It is noted that even small differences in the prehistory of the external parameters can lead to different modes of settling.