A method of preventing microcavity formation in a bonding layer of a composite structure resulting from creep and thermal expansion due to high temperature exposure of the composite structure. The method includes the steps of providing a thin film with a thickness of 5 micrometers or less; providing a bonding layer of oxide with a thickness that is equal to or greater than the thickness of the thin film with the bonding layer formed by low pressure chemical vapor deposition. The thin film or support substrate have a mean thermal expansion coefficient of 7×10−6 K−1 or more. The thin film, bonding layer and support substrate combine to reduce stress in and plastic deformation of the bonding layer during exposure to high temperatures of more than approximately 900° C. to thus prevent microcavities from appearing in the bonding layer.