Thickness-dependent fracture behaviour of flexible ZnO : Al thin films

• Published in: Journal of physics. D, Applied physics Applied physics, 2011-01, Vol.44 (2), p.025401-025401
• Main Authors: Mohanty, Bhaskar Chandra, Choi, Hong Rak, Choi, Yong Muk, Cho, Yong Soo
• Format: Article
• Language: English
• Subjects: Aluminum; Applied sciences; Condensed matter: structure, mechanical and thermal properties; Crack initiation; Cross-disciplinary physics: materials science; rheology; Density; Deposition by sputtering; Exact sciences and technology; Film thickness; Fracture mechanics; Fractures; Materials science; Mechanical and acoustical properties; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Methods of deposition of films and coatings; film growth and epitaxy; Physical properties of thin films, nonelectronic; Physics; Strain; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Thin films; Zinc oxide
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/44/2/025401

The effects of thickness on flexibility and crack initiation in ZnO : Al thin films sputter-deposited on polyethersulfone substrates have been investigated. With an increase in thickness, root-mean-square roughness and average crystallite size increase linearly. It is found that the higher the thickness, the lower is the strain required to initiate cracks in the film. The thinnest film (∼240 nm) exhibits a crack-initiating critical strain of 0.96% and a saturated crack density of 0.10 µm −1 . A critical energy release rate of 68.5 J m −2 and a mode I fracture toughness of 3.2 MPa m 0.5 are estimated for the films. These parameters are found to exhibit a linear dependence on film thickness.