Effect of molecular and atomic layer deposition thickness in zinc oxide hybrid films on surface cracks and mechanical properties of ultra-high molecular weight polyethylene

Abstract

The integration of molecular/atomic layer deposition (MLD/ALD) techniques offers a versatile platform for the fabrication of functional organic-inorganic hybrid thin-film structures. In this study, we utilized a hybrid thin-film approach comprising of a zinc oxide (ZnO) ALD layer and a diethylzinc (DEZ) + hydroquinone (HQ) MLD layer to enhance the surface quality and mechanical properties. The objective of this research was to investigate the changes in surface crack pattern and mechanical properties of the hybrid thin films by varying the composition and number of MLD/ALD layers while maintaining a fixed MLD/ALD ratio of 1:5. The hybrid films were synthesized using the [(DEZ + HQ) m + (DEZ + H2O) 5 m]n structure, where the value of mxn was fixed at 200, and the value of m was varied between 5, 10, 20, 100, and 200. The hybrid films were designated as Hm, and their surface morphology was observed by scanning electron microscopy to identify the presence of cracks. The mechanical properties of the films were evaluated by measuring the hardness and elastic modulus of an ALD-coated ultra-high molecular weight polyethylene using nano-indentation examinations, and the films' behavior in the wear environment was studied through micro-scratch testing. The results indicate that H5 and H10 hybrid films exhibited no surface cracks, while serious surface cracks were observed in H20 and H100 films. X-ray diffraction analysis showed that structural changes occurred in the hybrid films, and it was speculated that this was related to surface failure. The hardness and elastic modulus values increased with an increase in the m value and showed significant differences between hybrid films. This study demonstrated that the MLD/ALD-based hybrid thin-film approach is an effective means of enhancing surface quality and mechanical properties. The findings of this study have significant implications for the development of advanced materials and coatings for various industrial applications.