Kinetics of defect formation in thin-film vacuum condensates

Principal factors responsible for ageing of thin-film vacuum condensates on a glass base are considered. A hypothesis concerning the relation between the change in the relative defected area of thin-film coatings and a decrease in internal stresses in these coatings with time is proposed. Assuming that the film material is viscoelastic and obeys the Maxwell-Thompson rheological relation, a mathematical model of the kinetics of defect formation in thin-film vacuum condensates under normal conditions of storage and operation is developed on the basis of this hypothesis. Satisfactory agreement between calculated and experimental data suggests that this model can be recommended for qualitative and quantitative assessment of ageing of thin-film coatings obtained by condensation in vacuum.