Eliminating surface cracks in metal film-polymer substrate for reliable flexible piezoelectric devices

• Published in: Engineering science and technology, an international journal Vol. 50; p. 101617
• Main Authors: Badrudin, Syazwani Izrah, Noor, Mimiwaty Mohd, Abd Samad, Muhammad Izzuddin, Zakaria, Nur Syaza Nazihah, Yunas, Jumril, Latif, Rhonira
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2024; Elsevier
• Subjects: Crystallography; Leakage current; Residual stress; Sputter-deposition; Thermal expansion; Thermal expansion; Leakage current; Sputter-deposition; Crystallography; Residual stress
• ISSN: 2215-0986; 2215-0986
• DOI: 10.1016/j.jestch.2024.101617

[Display omitted] In a flexible piezoelectric-metal-polymer device, the occurrence of surface cracks in metal-polymer interface may cause unstable metal connections, unreliable piezoelectric yield, poor passivation behaviour and metal electrode delamination. In this study, the properties of polydimethylsiloxane (PDMS) polymer substrate are optimised, and the sputter-deposition of aluminium (Al) and molybdenum (Mo) metal film layer is controlled to eradicate cracks and promote only surface wrinkles on large area metal-polymer interface. The PDMS substrate thickness of ∼123.8 µm, 20:1 prepolymer base to curing agent weight ratio, 50 °C PDMS curing temperature and 30 min of Al sputtering time have been discovered to produce crack-free wrinkle-only Al thin film layer on PDMS substrate. The Al thin film is 100 % conductive over large area and adhere well on PDMS with 0 % of Al removal. The grown zinc oxide (ZnO) and aluminium nitride (AlN) piezoelectric layer on the improved Al-PDMS are of good crystal quality, generating low leakage current and decent piezoelectric voltage. The attained crack-free wrinkled-only metal film-polymer substrate interface is vital for flexible piezoelectric-metal-polymer device to perform well as an acoustic sensor, energy harvester, or even as an insulation/buffer layer in stretchable electronics.