engleski

Delamination buckling of thin metallic film studied by digital holographic light microscope interferometry

Here, we present an application of our Digital Optical Holographic Microscope (DOHM) [1] in the study of morphology and topography of buckling patterns that can be observed on thin film, during or after its delamination from thick substrate [2]. For deposition of tungsten thin films by magnetron sputtering [3], it is well known that argon pressure significantly affects the film internal stress. In the case of tensile residual stress a network of through-thickness cracks forms in the film, while the residually compressed thin films may delaminate from substrate and buckle [4]. As it is shown in Figure 1, buckling of thin tungsten film can result in a number of topographical patterns such as disordered surface wrinkles, regular herringbone, straight-sided or telephone cord buckles and circular blisters [5]. The associated mechanics has been studied [6] and evaluated for a number of cases of all types of buckles (circular, straight-sided, ...), but for the telephone cord (TC) ones, more precise microscopic observation (complemented by topographic measurements) are still needed for testing the corresponding models [6]. Delamination usually starts as straight-sided linear blisters, but then deviate to the TC periodic wavy geometry due to the fact that the compressive residual stress in the film is biaxial. In general, buckling profiles can be characterized depending on scale, by mechanical or laser-scanning profilometry, optical interferometer microscopy, or by using an atomic force microscope [7].

holographic interferometry; thin film delamination pattern

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