Residual Strain and residual Stress in Ultra-thin Films

Techniques for the measurement and prediction of stress and stress relaxation in ultra-thin films are being developed. For example:-

• The shift of the silicon Raman peak position is being used to determine the stress in strained silicon on silicon-germanium. To achieve this, techniques for deconvolution of the strained silicon and SiGe Raman peaks are necessary.
• The stress in aluminium metallisation is being measured in the as-processed state by a rotation beam sensor which has been designed as part of an EPSRC-funded project.
• The stress in individual layers of low emissivity and solar control coatings on glass is being measured by a combination of x-ray diffraction, Raman spectroscopy and indentation methods

The modelling of stress generation and relaxation using finite element analysis has been used to develop a thermomechanical history model of the coatings in such applications.