STUDY OF ION-BEAM MIXING AT A FE GAAS INTERFACE/

The structural state at a Fe/GaAs interface has been investigated afte r ion-beam mixing (IBM) using X-ray diffraction, transmission electron microscopy and conversion electron Mossbauer spectroscopy. 50 and 100 nm thick Fe films were deposited on (100) GaAs substrates and the IBM was carried out at 293 K with 320 keV Kr2+ ions to doses from 1 to 8 x 10(16) ions/cm(2). The as-deposited films consisted of alpha-Fe and after mixing an amorphous Fe-Ga-As phase appeared in the subsurface zo ne. Different Fe coordination and magnetic states have been identified in the mixed layer and attributed to ferromagnetic Fe, paramagnetic F e and paramagnetic Fe-oxide respectively, the former phase being the m ost abundant. The irradiation-dose growth led to a gradual decrease of alpha-Fe content and a monotone increase of amorphous phase content. For the 50 nm thick Fe films; complete mixing was obtained at a critic al fluence of 5 x 10(16) ions/cm(2). A study of mixing efficiency perf ormed on 100 nm thick Fe films showed that the efficiency was somewhat less than I, thus suggesting the onset of demixing processes.