Antibacterial and physicochemical properties of co-sputtered CuSn thin films

Copper-tin thin films (CT TFs) were deposited on p-type Si(100) by radio frequency (RF) magnetron co-sputtering method. The atomic ratio of Cu and Sn showed complementary tendency with various RF powers on metal targets. Antibacterial test was conducted with Gram-negative Escherichia coli. The ratio of Cu and Sn ions and the contact time with E.coli affected the antibacterial efficiency. Increasing the ratio of Cu ions and contact time showed higher antibacterial activity. Cu20Sn6 called as bronze structure, metallic Cu, and copper oxide phases were identified from X-ray diffraction data after sterilization. The lattice strain that was changed due to the substitution of Cu and Sn was also calculated. The surface morphology of CT TFs was entirely grown to round shape when the dominant element was Sn. But, as the content of Cu increased, the surface morphology was changed from ball shape to sharp column shape. When fixed contact time, the intensities of Cu 2p increased but the intensities of Sn 3d decreased as increasing the atomic ratio of Cu. The oxidation of Cu was more sharply progressed as the RF power on Cu target increased. When fixed CT TFs, the intensities of Cu 2p were consistent but the intensities of Sn 3d(3/2) decreased as increasing contact time between CT TF and E.coli.