Study of structural, electrical, optical and magnetic properties of zinc oxide based films produced by magnetron sputtering

This work focused on the evaluating of the structure, optical, electrical and magnetic properties of and Zn0.90Co0.10O and Zn 0.85[Co0.50Fe0.50]0.15O thin films synthesized from ceramic targets using the magnetron sputtering technique. Given the complexity of the deposition processes and in order to optimize the quality of the films in study, the first step this work consisted in carrying out a systematic study about the structural features and optical properties of ZnO films as function of substrate to target distance and rf power considering the magnetron sputtering system used in this work. This study reveled that the substrates must be located between -1 cm and +6 cm on holder with a vertical substrate to target distance of 7.5 cm approximately. The sputtering conditions possible or range optimum for the deposition were: rf power between 80 and 125 W, argon working pressure between 8.0 x 10-3 and 9.0 x 10-3 Torr, substrate temperature between 200 and 300°C. The X-ray diffraction patterns of Zn0.90Co0.10O and Zn0.85[Co0.50Fe0.50]0.15O films showed only (002) peak indicating the strong preferred orientation along these planes. Zn0.90Co0.10O film showed transmittance above 70% with three absorption peaks in 1.89, 2.03 and 2.18 eV attributed to d¯-d transitions of tetrahedrally coordinated Co2+. Transmittance optic of Zn0.85[Co0.50Fe0.50] 0.15O film was less than Zn0.90Co0.10O film between 400-700 nm. The band gap values for Zn0.90Co0.10O and Zn0.85[Co 0.50Fe0.50]0.15O films were 2.95 and 2.70 eV respectively, which are slightly less than ZnO films found in this work. Although these films exhibited good crystallinity with a fraction of Zn atoms substituted by Co and Fe, from M-H measurements no indication of FM in both films was observed between -2000 and 2000 Oe at room temperature, indicating on the contrary, a possible character antiferromagnetic.