Ion induced modifications of Mn-doped ZnO films

We have studied ion impact effects on atomic structure in terms of X-ray diffraction (XRD), optical absorption and electrical resistivity of Mn(6%)-doped ZnO films under 100 MeV Xe ion impact at room temperature. We find the monotonic reduction of the XRD intensity to 1/50 of that of unirradiated film at 5 × 1014 cm−2 and the lattice compaction of 0.6% for the ion fluence >1013 cm−2, little bandgap change (<0.02 eV) and decrease of the resistivity by 4 order of magnitude. The resistivity modification has been compared with that by irradiations of low energy ions such as 100 keV Ne and N, which show more effective decrease of resistivity. We also find that temperature (T) dependence of the magnetic susceptibility (χ) of Mn-doped ZnO follows the Curie law: χ = χo + C/T (i.e., paramagnetic) and the Curie constant C decreases to a half of that before irradiation (CO = 0.012 emu cm−3 K) at 100 MeV Xe ion fluence of 1012 cm−2. Relationship is discussed between modifications of the magnetic property and change in the valence of Mn, using a simple and crude argument.