| Title |
Deposition of ZnO Thin Films by RF Magnetron Sputtering and Cu-doping Effects |
| Authors |
이진복(Lee, Jin-Bok) ; 이혜정(Lee, Hye-Jeong) ; 서수형(Seo, Su-Hyeong) ; 박진석(Park, Jin-Seok) |
| Keywords |
ZnO ; Cu-doping effect ; RF magnetron sputtering ; structural and electrical properties, SAW device |
| Abstract |
Thin films of ZnO are deposited by using an RF magnetron sputtering with varying the substrate temperature(RT~390°C) and RF power(50~250W). Cu-doped ZnO(denoted by ZnO:Cu) films have also been prepared by co-spputtering of a ZnO target on which some Cu-chips are attached. Different substrate materials, such as Si, SiO_{2}/Si, sapphire, DLC/Si, and poly-diamond/Si, are employed to compare the c-axial growth features of deposited ZnO films. Texture coefficient(TC) values for the (002)-preferential growth are estimated from the XRD spectra of deposited films. Optimal ranges of RF powers and substrate temperatures for obtaining high TC values are determined. Effects of Cu-doping conditions, such as relative Cu-chip sputtering areas, O_{2}/(Ar+O_{2}) mixing ratios, and reactor pressures, on TC values, electrical resistivities, and relative Cu-compositions of deposited ZnO:Cu films have been systematically investigated. XPS study shows that the relative densities of metallic Cu(Cu^{0}) atoms and CuO(Cu^{2+})-phases within deposited films may play an important role of determining their electrical resistivities. It should be noted from the experimental results that highly resistive(> 10^{10}{Ω}cm ZnO films with high TC values(> 80%) can be achieved by Cu-doping. SAW devices with ZnO(or Zn):Cu)/IDT/SiO_{2}/Si configuration are also fabricated to estimate the effective electric-mechanical coupling coefficient(k_{eff}^{2}) and the insertion loss. It is observed that the devices using the Cu-doped ZnO films have a higher k_{eff}^{2} and a lower insertion loss, compared with those using the undoped films. |