Origin of magnetism in low energy Ni ion implanted ZnO thin films

Abstract

ZnO films grown on Si(100) substrate through radio frequency (RF) sputtering are subjected to 100 keV Ni ion beam at different fluence (1 x 10(16), 2.5 x 10(16) and 5 x 10(16) ions/cm(2)). High resolution X-ray diffraction revealed the increase in crystallite size and development of stress gradient in the ZnO thin films with the increasing Ni ion fluence. Ni implanted ZnO/Si(100) films exhibits room temperature ferromagnetism (RTFM) which is discussed via defect induced bound magnetic polaron model. Near-edge X-ray absorption fine-structure (NEXAFS) measurements at Ni L-3,L-2-edge confirm the nature of implanted Ni ion inside the ZnO matrix. Further, NEXAFS at O K-edge revealed the onset of O(2p) with Ni(3d) orbital states, which is correlated with the observed RTFM.