Raman scattering characteristics of Mn-doped ZnO films

The Raman scattering characteristics of the Zn_1-xMn_xO (x=1, 2, 3, and 5 at. %) thin films deposited by pulsed laser deposition were detailed studied. The Mn doped ZnO films had a perfect (002) orientation and presented ferromagnetism at room temperature. The magnetic moment per Mn ion decreased gradually with increasing Mn doping contents. Raman scattering showed that the vibration modes of the E₂ (low) and E₂ (high) had a close relation to the density of the defects. With increasing Mn doping, the increased grain size resulted in the decrease of full width at half maximum (FWHM) of E₂ (low) mode, and also the phonon correlation region decreased due to the destroyed periodic crystal lattice of the films. Meanwhile, the diminishment of the density of oxygen vacancy made the FWHM of E₂ (high) mode became narrow. The A₁ (LO) mode was mainly affected by the fluctuation of electrical field induced by Mn ions doped into the ZnO films. The weakening of ferromagnetism was related to the increase of the disorder and to the diminishment of the defect density such as zinc vacancy and oxygen vacancy.