In this study, we investigated the interfacial adhesion strength (σint) of transparent conductive oxide (TCO) coatings on polymer substrates using a nanosecond Nd:YAG pulsed laser. We compared our results with those achieved using conventional testing methods such as bending and fragmentation tests as well as theoretical calculations. In the fragmentation and bending tests, mechanical compressive stress is induced in the film due to mismatches in Poisson's ratio and Young's modulus between the substrate and film. But, the incident laser makes the film under compression due to the mismatch in thermal expansion between the TCO and the polymer substrate. With a pulse incident to the substrate, the TCO rapidly expands by laser-induced instant heating while the transparent polymer does little, which causes the TCO to buckle and delaminate over the critical pulse energy. The critical compressive stress that scales with σint was calculated using simple equations, which agreed well with the results from previous theoretical calculations. Because the films preferentially delaminate at the defects and grain boundaries, this technique also provided useful information regarding the interface microstructures. Moreover, because the laser can scan over large areas, this method is suitable for flexible substrates that are produced by a roll-to-roll process. Nevertheless, the mechanical stress introduced by the bending and fragmentation tests causes the TCO to buckle without interfacial delamination. Hence, the stresses at the buckling disagreed with the results obtained from the laser test and the theoretical calculations.
Bibliographical noteFunding Information:
This research was supported by a grant from the Fundamental R&D Program for Technology of World Premier Materials (WPM), which was funded by the Ministry of Knowledge Economy and Seoul RNBD Program (JP110041) of the Seoul Development Institute, Republic of Korea. We thank Professor Myeongkyu Lee, his students at Yonsei University, and undergraduate research assistants Han-Ghil Jeong and Young-Joo Lee at Yonsei University for their support on this work.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)