Analysis on the local structure and its implication on the magnetic properties of Si1−xMnx thin films

Si1−xMnx diluted magnetic semiconductor films were deposited on p-type Si(1 0 0) substrate by radio frequency magnetron sputtering method. Post thermal annealing was performed in an argon atmosphere at 1073 K for 300 s and at 1473 K for 120 s. The as-grown sample exhibits ferromagnetism at room temperature. Ferromagnetism is enhanced after annealing treatment. High resolution transmission electron microscopy shows that only Mn4Si7 compound formed in all samples. X-ray diffraction patterns and Fast Fourier Transform image indicate Mn atoms incorporated into Si lattice upon annealing. X-ray absorption fine structure suggests the formation of substitutional-tetrahedral interstitial Mn-Mn and tetrahedral interstitial-substitutional-tetrahedral interstitial Mn-Mn-Mn complexes in the 1473 K annealed sample, which possesses the strongest ferromagnetism.