Ion beam-induced and thermal reactions at Fe:GaAs interface

Ion beam-induced and thermal reactions at Fe:GaAs interface are studied by using conversion electron Mössbauer spectroscopy and small angle X-ray diffraction measurements. A thin film of Fe (enriched to 30% in⁵⁷Fe Mössbauer isotope) was deposited in UHV environment on 〈100 〉 oriented semi-insulating GaAs substrates. Some of the samples were ion-mixed by 130 keV Ar⁺ ions at dose values of 3 × 10¹⁵ and 10¹⁶ ions/cm². The asdeposited and ion-mixed samples were annealed at different temperatures up to a maximum of 500° C. It was observed that ion mixing led to precipitation of disordered and/or defective binary phase along with ferromagnetic Fe₃GaAs ternary phase which upon vacuum annealing at 500°C for 1 h leads to a mixture of structurally well-defined Fe₃Ga, FeAs and FeAs₂ phases. The combined analysis of Mössbauer and X-ray data is shown to reveal the location of the phases below the sample surface. The mechanism for phase formation and associated reaction kinetics at Fe/GaAs interface is discussed in the light of the experimental results.