Influence of annealing on the local structure, magnetic and transport properties of Mn-doped SiC films

Mn-doped SiC films are deposited on Si (1 0 0) substrates by the RF-magnetron sputtering technique. The influence of annealing on the local structure, magnetic and transport properties of the films is investigated systematically by x-ray diffraction, x-ray photoelectron spectroscopy, x-ray absorption fine structure, transport and magnetic measurements. The results show that for the as-deposited and 800 degrees C annealed films, the doped Mn atoms occupy the C sites of the 3C-SiC lattice, only semiconducting behaviour is observed in the whole temperature range and the transport property is governed by Mott variable range hopping behaviour, suggesting that the carriers are strongly localized. After 1200 degrees C annealing, the majority of Mn atoms form Mn4Si7 secondary phases and a crossover from semiconducting to metallic transport behaviour with transition temperatures occurring at 134 K is detected in the film. Magnetic characterization shows that all the films are ferromagnetic with a Curie temperature of above 300 K and the saturated magnetic moment increases monotonically with increasing annealing temperature. It is speculated that the ferromagnetism of the films is intrinsic and can be ascribed to rely on the percolation of bound magnetic polarons for the as-deposited and 800 degrees C annealed films. After 1200 degrees C annealing, the carbon-incorporated Mn4Si7 compounds can be considered to be the origin of ferromagnetism in the film.