Residual stress is known to affect significantly the mechanical fracture behavior of flexible thin films. Here, an in situ chemical deposition process that allows for control of extra compressive or tensile stress in PbS thin films is suggested. This process uses the fixed convex or concave surface of a flexible substrate to impart compressive or tensile stress, respectively, after the releasing step to the flat mode. Using two technical evaluations of mechanical fracture behavior, the existence of extra stress is verified with expected enhancements of the fracture resistance only in the case of compressive stress. For example, a ≈36% improvement of the elastic modulus is confirmed by nanoindentation testing for compressively stressed PbS thin films. The bending fracture resistance is also enhanced for the compressively stressed films, as evidenced by a ≈18.5% improvement in the crack-initiating critical strain and a ≈121% increment in the fracture energy under the bending motion.
Bibliographical noteFunding Information:
DBK and SML contributed equally to this work. This work was financially supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of Korea (20173010013340), and the Creative Materials Discovery Program by Ministry of Science and ICT (2018M3D1A1058536).
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics