Physicial Properties of Iron-Nitride Films Expitaxially Grown on Silicon (001) by Sputtering and Assessment of Giant Magnetic Moment in the Alpha-Iron-Nitride Phase;Doctoral thesis

摘要

Intense scientific and technological interest in iron nitrides has persisted since saturation magnetizations much larger than that of (alpha)-Fe (1708 emu/cm(sup 3)) were reported for the metastable (alpha)(double underline prime)-Fe(sub 16)N(sub 2) phase (2300 emu/cm(sup 3)) using technologically-relevant deposition processes and substrates have resulted in only a modest enhancement in moment, and are complicated by competition from more stable FeN phases. Furthermore, conventional band theory calculations for (alpha)(double underline prime) (1780 emu/cm(sup 3)) do not predict a 'giant' magnetic moment. The authors have grown several phases of FeN on Si(001) by lattice matching on Ag underlayers. Optimization of reactive N(sub 2) sputtering parameters has led to the growth of (alpha)-Fe, (gamma)(prime)-Fe(sub 4)N and (alpha)(prime)-Fe(sub 8)N films. Annealing of N-disordered (alpha)(prime)-Fe(sub 8)N films resulted in partial transformation to N-ordered (alpha)(double underline prime)-Fe(sub 16)N(sub 2). Quantification of X-ray diffraction peak intensities determined that the (alpha)(prime)/(alpha)(double underline prime) mixtures contained 48 vol% (alpha)(double underline prime) (remaining (alpha)(prime)). Selected-area diffraction (SAD) in the TEM determined that the orientation relationships of the (alpha), (alpha)(prime), and (alpha)(double underline prime) phases were FeN(001) double vertical bars Ag(001) double vertical bars Si(001) and FeN(100) double vertical bars Ag(110) double vertical bars Si(100), while the in-plane orientation of (gamma)(prime)(001) was FeN(110) double vertical bars Ag(110) double vertical bars Si(100). Electron energy-loss spectroscopy (EELS) determined that the FeN films were stoichiometrically correct and there was no significant change in N content with annealing.