Intrinsic ferromagnetism at room temperature has been observed in ZnO/sapphire films by implantation of 200 keV Ni2+ ions with fluences 6× 1015, 8× 1015, 1× 1016, and 2× 1016 ions/ cm2. Crystalline phases are identified by glancing angle x-ray diffraction, which shows no extra phase in the implanted films. Highest saturation magnetization (Ms) is observed in the film implanted with the fluence of 8× 1015 ions/ cm2 as examined by superconducting quantum interference device magnetometry. This film has almost 80% transmittance across visible wavelength range and hence a potential candidate of transparent ferromagnetic semiconductor. Defectlike oxygen vacancies in the films are studied by x-ray photoelectron spectroscopy. Ferromagnetism of the films is explained on the basis of bound magnetic polaron model.
Bibliographical noteFunding Information:
The authors are grateful to Department of Physics, IIT Delhi, LEIBF group IUAC, New Delhi and FZD, Dresden for providing experimental support. We also acknowledge some financial support provided by DST and UGC, New Delhi. One of us (B.P.) thanks Dr. R. Singh of IITD and Semiconductor Physics Group, Leipzig University, Germany for providing ZnO/sapphire films.