Crystallinity improvement of room-temperature PLD-deposited ZnO thin films on cyclo-olefin polymer substrates subject to surface-pretreatment with vacuum-UV-light irradiation

• Published in: Journal of crystal growth Vol. 603; p. 127012
• Main Authors: Oga, Tomoaki, Kai, Ryoya, Kaneko, Naho, Miyazaki, Hisashi, Kaneko, Satoru, Matsuda, Akifumi, Yoshimoto, Mamoru
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2023
• Subjects: A1. Crystallites; A1. Surface processes; A3. Physical vapor deposition processes; B1. Oxides; B1. Polymers; B1. Zinc compounds; A1. Crystallites; A3. Physical vapor deposition processes; B1. Polymers; A1. Surface processes; B1. Oxides; B1. Zinc compounds
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2022.127012

•VUV-irradiation of COP surface increased crystallinity of ZnO thin film on COP.•TEM revealed atomically sharp interface between ZnO thin film and VUV-treated COP.•Resistivity of ZnO thin film grown on VUV-treated COP substrate was reduced by 40%. The effect of the surface-pretreatment of cyclo-olefin polymer (COP) substrates with vacuum-ultraviolet (VUV) light irradiation on the crystal growth of ZnO thin films deposited by room-temperature pulsed laser deposition (PLD) was investigated for development of flexible optical devices. 172-nm-excimer light irradiation with durations of 60 to 600 s in air was found to make the COP surface more hydrophilic and smooth. It was verified from measurements of X-ray diffraction, atomic force microscope and high-resolution transmission electron microscope that the ZnO thin films grown on the VUV-light-pretreated COP substrates exhibited enhanced (0001) orientation growth and increased crystallinity compared with the samples grown on substrates not subject to the pretreatment; the samples on the pretreated substrates also showed a smooth surface and atomically sharp interface between the thin film and the substrate. The electrical resistivity of the ZnO thin film grown on the VUV-light-pretreated COP substrate was estimated to be 2.3 × 10−3 Ωcm, which was 40% lower than that of the film grown on the untreated substrate.