Investigation of Antibacterial Efficacy of CuCrO2 Delafossite Thin Films Against E. coli

Abstract

Terminals used in hospitals, information systems displaying patient information, and smartphones use touch panels that incorporate n and p transparent conducting oxide (TCO) layers [1]. There are a lot of pre-existing research present on n-type TCO while at the same time similar research interest related to p-type TCOs has been lacking. This is due to the inherently high electrical resistivity or low optical transparency of p-type TCOs. Recently, there has been a spike in research related to p-type delafossite thin films, owing to their excellent electrical and optical properties as compared to the other p-type counterparts. Cu-based p-type delafossite materials exhibit low resistivity and at the same time good optical transparency in the visible region. Among the Cu-based delafossites, copper chromium oxide (CuCrO2) exhibits the lowest electrical resistivity reported yet. Use of CuCrO2 as the p-type TCO along with a suitable n-type TCO might demonstrates significant potential to be used for optoelectronic applications.In this work, CuCrO2 thin films have been deposited on quartz substrates using dual target RF magnetron sputtering technique. This involved dual sputtering of 3- inch Cu2O and Cr2O3 targets. The substrate temperature was maintained at 400 °C during the deposition with Ar used as the sputtering gas. This was followed by post deposition annealing. Previous research carried out by our group has indicated that single-phase CuCrO2 was obtained at an annealing temperature of 650 °C in N2 ambiance for 4 hours [2, 3]. Successful synthesis of single-phase CuCrO2 has been confirmed using XPS and XRD study. The resistivity of CuCrO2 was obtained as 0.652 Ω-cm, which is the lowest reported so far. The optical study denoted an average optical transmission of > 60% in the visible wavelength spectrum and a high optical bandgap of 3.2 eV. The antibacterial efficacy of different thickness of CuCrO2 thin films was tested against E. coli bacterial strain and compared against the efficacy of plain quartz in this research work. Results showed that with an increase in the thickness of CuCrO2 thin films, the efficacy against E. coli increases. The highest antibacterial efficacy of 78.07 % was shown by 2000 A° CuCrO2 thin film.[1] Chiu T-W, Yang Y-C, Yeh A-C, Wang Y-P, Feng Y-W. Antibacterial property of CuCrO2 thin films prepared by RF magnetron sputtering deposition. Vacuum. 2013;87:174-177.[2] Sundaresh S, Bharath AH, Sundaram KB. Effect of Annealing Temperature on Radio Frequency Sputtered p-Type Delafossite Copper Chromium Oxide (CuCrO2) Thin Films and Investigation of Diode Characteristics Forming Transparent pn-Heterojunction. Coatings2023.[3] Sundaresh S, Bharath AH, Sundaram KB. Effect of Cu2O Sputtering Power Variation on the Characteristics of Radio Frequency Sputtered p-Type Delafossite CuCrO2 Thin Films. Coatings2023.