In-Line Sputtered Copper/Aluminum-Doped Zinc Oxide Films on Glass Prepared for Energy-Saving and Antibacterial Function

Energy-saving glass is designed to minimize heat transfer between the interior and exterior of a building, resulting in reduced energy consumption. Low-emissivity (low-e) glass is a type of Energy-saving glass. It offers superior insulation by reducing heat loss or gain through windows. Both energy-saving and low-e glass are widely used in buildings to improve energy efficiency, and contribute to improve the sustainability of buildings. If energy-saving glass in public facilities has antibacterial functionality, it can provide the public with a healthy and comfortable environment. This study reports the feasibility of copper/aluminum-doped Zinc Oxide (Cu/AZO) films applied in energy-saving glass. Cu/AZO films have been deposited on glass substrates via in-line sputtering system. Antibacterial effects are provided by Cu layer, while AZO layer offers thermal insulation capabilities. In-line sputtering is a process used for depositing thin films onto a continuous substrate. It offers high throughput, uniform coating, and precise control over film properties. It is commonly employed in manufacturing industries for applications such as architectural glass. Thus, this instrument is used in the study. In this study, Cu/AZO films were directly deposited by in-line sputtering with a Cu and AZO target, respectively. In addition, we manufactured a single-layer AZO films for comparison with Cu/AZO films. The structure, visible transmittance, adhesion test and antibacterial activity of the AZO films and Cu/AZO films were compared. The experimental results indicate that the single-layer AZO exhibits low resistivity and low emissivity but lacks antibacterial function. In comparison to AZO, Cu/AZO demonstrates lower resistivity and emissivity. The electrical resistivity of Cu/AZO samples are 1.08x10
^–3
Ω-cm, which decreases 49% compared with that of the AZO. According to the Hagen-Rubens relation, the reduction in electrical resistivity corresponds to the decrease in material emissivity. The emissivity of Cu/AZO films and AZO films were 0.22 and 0.43 respectively. The average transmittance in visible wavelength (400–800 nm) of Cu/AZO films and AZO films were 56% and 74% respectively. The antibacterial testing was conducted in accordance with the JIS Z2801:2000 standard. Cu/AZO films exhibited a pronounced antibacterial effect against E. coli, displaying an antimicrobial activity level of about 8. Copper material provides antibacterial property, possibly due to its contact killing mechanism. Copper ions cause the destruction of the cell membrane. Furthermore, the addition of copper further reduces the material's resistivity and emissivity. The Cu/AZO proposed in this study has antibacterial and thermal insulation functions. In the future, this can be applied in the mass production of energy-saving glass and the field of green materials.