||This work investigated pure, conductivity and transparency zinc oxide (ZnO) thin films on the polymer substrates at a low temperature (< 75℃) by using cathodic vacuum arc deposition (CVAD) system. We reported the material, optical, electrical and mechanical properties of ZnO thin film with various processing conditions. |
The pure ZnO thin films were deposited on the various polymer substrates such as PET, PVB and PI substrate and the properties of the deposited ZnO tin films were investigated. The figure of merit (FOM) based on the transparent and conductive property was used to determine the quality of the deposited ZnO thin film on the various polymer substrate. The FOM for PET, PVB and PI were 1E-3, 8E-4 and 8.2E-4. Therefore, the PET substrate was selected in the following research.
The ZnO/Al/ZnO multistructure is a good transparent and conductive thin film with Al is a seed buffer layer. The Al thickness of 20 nm was a fixed and the thickness of the ZnO film were varied with 50, 100,150 and 250 nm. When the thickness of ZnO thin film was in the 50 nm, the ZnO/Al/ZnO multistructure has a value of FOM (50 nm：3.4E-4, 100 nm：2.3E-5, 150 nm：2.2E-5, 200 nm：1.9E-5).
ZnO thin films were deposited with the different O2/Ar gas flow ratio (6：1, 7：1, 8：1, 9：1 and 10：1, Ar gas flow in 20 sccm). The average transmittance of 86.38% in the visible region and the resistivity (ρ) of 3.65 x10-3 Ω-cm with the mobility (μ) of 4.83 cm2/V·s was obtained for the ZnO thin film under O2/Ar 8：1.
With arc current in 60 A and the O2/Ar gas flow ratio in the 8：1, the effect of various arc currents (40、50、60、70 and 80 A) on the properties of the pure ZnO film were investigated. Under the arc current of 60 A, the deposited thin film had a high average transmittance of 86.38% in the visible region and the resistivity (ρ) of 5.88 x10-3 Ω-cm with the mobility (μ) of 11.24 cm2/V·s.
Finally, the mechanical properties of the deposited ZnO thin film on the PET substrate were investigated. It was found that the deposited ZnO thin film could bear under the load in 1980 uN and was cracked under the scratch load in 40 mN. Compared with the reference sample, the crack of sputtered Al-doped ZnO (AZO) film was appeared in the load of 800 uN as the AZO thin film thickness was 664 nm. The scratch load of sputtered ZnO thin film on PET substrate with 300 nm thickness was 30 mN. Thus, the deposited ZnO thin film by using CVAD system had better hardness and adhesion than those using sputtering system.