Thin film scratch testing in two dimensions - Experiments and analysis

Maarten P. De Boer, John C. Nelson, William W. Gerberich

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

We have modified the microscratch test to create a near plane strain loading condition. In the Microwedge Scratch Test (MWST), a wedge-shaped diamond indenter tip is drawn along a fine line (i.e., narrow strip of film), while simultaneously being driven into the line. We compare microwedge scratching of zone 1 (voided grain boundaries) and zone T (metallurgical grain boundaries) thin film specimens of sputtered tungsten on thermally grown SiO2. Symptomatic of its weak grain boundaries, the zone 1 film displays three separate crack systems. Because of its superior grain boundary strength, the zone T film displayed only one of these - an interfacial crack system. By correlating fracture phenomena to signature events in the load-displacement curve, we develop governing equations for propagating interfacial cracks, including expressions for strain energy release rate, bending strain, and mode mixity. Grain boundary fracture causes zone 1 films to spall before a stable crack is formed. Zone T films survive the bending strains, and hence adhesions may be inferred from stable crack growth mechanics. We conclude by contrasting and comparing experimental results for plane strain indentation versus plane strain scratching.

Original languageEnglish (US)
Pages (from-to)1002-1014
Number of pages13
JournalJournal of Materials Research
Volume13
Issue number4
DOIs
StatePublished - Apr 1998

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