Tensile Stress as a Factor of Deformation and Failure of Thin Films and Coatings

The paper provides analysis of literature data regarding reasons for development of tensile stresses in continuous thin films and coatings, in the process of their formation and under various external influences, as well as study of main mechanisms of their deformation and failure under tensile stresses. Special focus is drawn to the role of film/substrate interface in failure of thin-film structures. Factors controlling initiation and propagation of failure throughout film-substrate system are considered. Main reasons for emergence of the most common models of failure of thin-film structures - edge delamination from the base and film cracking - are demonstrated. In the process of film failure, each of these mechanisms can contribute to the development of the other one, and on the other hand, they both provide relaxation of tensile stresses, thereby competing and suppressing the development of each other. Study of stress relaxation is important for obtaining new structures and certain physical and mechanical properties of coatings. Determining the critical values of stresses that lead to failure is an urgent task, regardless of the method of obtaining coatings and thin films. Development of theoretical basis for predicting and regulating values and sign of stresses that occur during the formation of nanostructures in a plasma environment complement existing models for obtaining these structures in order to further study the plasma methods of growing nanostructures.