Electro-Fragmentation Analysis of Dielectric Thin Films on Flexible Polymer Substrates
A novel electro-fragmentation method was developed as a fast alternative to the time consuming fragmentation test carried out in situ in a microscope, to investigate the failure of dielectric inorganic coatings on polymer substrates. An ultrathin conductive layer was used to probe the onset of tensile failure in the dielectric coating through changes of its electrical resistance. A careful selection of the conductive layer has been carried out to avoid artifacts resulting for instance from a change of the cohesive properties (e.g. internal stress state) of the investigated structures. Au layers were found to be too ductile, contrary to Al-Ti layers that were too brittle, which invalidated the use of both materials to probe the failure of the dielectric coatings. In contrast, for structures on high-temperature polymer substrates, a 10 nm thick amorphous graphite (a-G) layer was found to accurately reproduce the cracking of the coating. The Young’s modulus and coefficient of thermal expansion of the a-G layer are low enough not to impact the internal strain, hence the crack onset strain of the dielectric coating. The a-G layer is also sufficiently brittle, and its cohesive failure and resulting increase of electrical resistance is triggered by the failure of the dielectric coating. The a-G electrofragmentation method is presently limited to polymers substrates with a glass-transition temperature higher than 100 °C.
Keywords: flexible electronics ; mechanical integrity ; electrical resistance ; amorphous graphite ; ULTRATHIN OXIDE COATINGS ; CARBON-FILMS ; POLY(ETHYLENE-TEREPHTHALATE) ; DISPLAYS ; ADHESION ; STRAIN ; LAYERS ; MECHANICS ; STRESSES ; CRACKING
[Pinyol, Albert Meylan, Bastian Gilleron, Damien Mewani, Vinodh Leterrier, Yves Manson, Jan-Anders E.] Ecole Polytech Fed Lausanne, Lab Technol Composites & Polymeres, CH-1015 Lausanne, Switzerland. Leterrier, Y, Ecole Polytech Fed Lausanne, Lab Technol Composites & Polymeres, CH-1015 Lausanne, Switzerland. email@example.com
ISI Document Delivery No.: 402NH
Times Cited: 1
Cited Reference Count: 45
Pinyol, Albert Meylan, Bastian Gilleron, Damien Mewani, Vinodh Leterrier, Yves Manson, Jan-Anders E.
EU-funded Flexidis Project [IST - 004354]; XRD analysis
The authors are grateful to the EU-funded Flexidis Project (IST - 004354) for funding this work, and to the companies Unaxis Balzers Ltd., Displays Division, Philips and Tetra Pak Suisse S.A. for supplying samples. Victor Fernandez-Altable is acknowledged for support in XRD analysis.
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Record created on 2009-01-13, modified on 2016-08-08