A Comprehensive Investigation of the Mechanical and Tribological Properties of AZO Transparent Conducting Oxide Thin Films Deposited by Medium Frequency Magnetron Sputtering

Michał Mazur; Milena Kiliszkiewicz; Witold Posadowski; Jarosław Domaradzki; Aleksandra Małachowska; Paweł Sokołowski

doi:10.3390/ma17010081

A Comprehensive Investigation of the Mechanical and Tribological Properties of AZO Transparent Conducting Oxide Thin Films Deposited by Medium Frequency Magnetron Sputtering

Materials (Basel). 2023 Dec 23;17(1):81. doi: 10.3390/ma17010081.

Authors

Michał Mazur¹, Milena Kiliszkiewicz¹, Witold Posadowski¹, Jarosław Domaradzki¹, Aleksandra Małachowska², Paweł Sokołowski²

Affiliations

¹ Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Janiszewskiego 11/17, 50-372 Wroclaw, Poland.
² Faculty of Mechanical Engineering, Wrocław University of Science and Technology, Lukasiewicza 5, 50-371 Wroclaw, Poland.

Abstract

This paper presents a detailed analysis of aluminium-doped zinc oxide (AZO) thin films and considers them a promising alternative to indium tin oxide in transparent electrodes. The study focusses on critical properties of AZO, including optical, electrical, and mechanical properties, with potential applications in displays, photovoltaic cells, and protective coatings. The deposited AZO thin films are characterised by excellent optical and electrical parameters, with transparency in the visible light range exceeding 80% and resistivity of 10^-3 Ω·cm, which gives a high value of figure of merit of 63. Structural analysis confirms the nanocrystalline nature of as-deposited AZO thin films, featuring hexagonal ZnO, orthorhombic Al₂O₃, and cubic Al₂ZnO₄ phases. The study includes nanoindentation measurements, which reveal exceptional hardness (11.4 GPa) and reduced elastic modulus (98 GPa), exceeding typical values reported in the literature, highlighting their protective potential. Abrasion tests have shown extraordinary scratch resistance due to the lack of impact on topography and surface roughness up to 10,000 cycles. This comprehensive study demonstrated that as-deposited AZO thin films are multifunctional materials with exceptional optical, electrical, and mechanical properties. The findings open up possibilities for a variety of applications, especially in protective coatings, where the combination of hardness, scratch resistance, and transparency is both rare and valuable.

Keywords: AZO; figure of merit; hardness; magnetron sputtering; nanoindentation; optical properties; resistivity; scratch resistance; thin film; transparent conducting oxide.

Grants and funding

This work was financed from the internal sources of Wroclaw University of Science and Technology.