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MA: Fachverband Magnetismus

MA 24: Magnetic Semiconductors

MA 24.9: Vortrag

Mittwoch, 25. März 2009, 16:45–17:00, HSZ 401

On the formation of secondary phases in Fe implanted GaN — •Georg Talut¹, Helfried Reuther¹, Joerg Grenzer¹, Carsten Baehtz¹, Dmitri Novikov², and Bente Walz² — ¹Institute of Ion Beam Physics and Material Research, Forschungszentrum Dresden-Rossendorf e.V., P.O. Box 510119, 01314 Dresden — ²Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg

The request for room-temperature diluted magnetic semiconductors resulted in a large interest in GaN doped with transition metals. Recent investigations have shown that beside of the real dilute state spinodal decomposition as well as the formation of secondary phases may play an important role in the discussion of the origin of the ferromagnetism in GaN [1,2]. In this study, the formation of secondary phases was investigated in GaN epilayers deposited on sapphire and implanted with ⁵⁷Fe ions (3, 8 and 16×10¹⁶ cm⁻²) at room temperature. Samples were annealed at 750^∘ - 1200^∘ C in N₂ and Ar flow for durations between some ms and some minutes. The formation of secondary phases in Fe implanted GaN upon annealing a N₂-flow was detected ex-situ by means of x-ray diffraction and Mössbauer spectroscopy and supported by SQUID magnetometry. During annealing in reduced N₂ atmosphere the reverse phase change from Fe₃N at room temperature to Fe_2.4N at 1023 K was observed by means of in-situ x-ray diffraction. Samples, annealed by a flash lamp illumination in an Ar flow showed the formation of different secondary phases depending on annealing time and temperature. [1] Bonanni et al., PRL 101, (2008) 135502; [2] Li et al., Journal of Crystal Growth 310,(2008) 3294