Ion-beam mixing and thermal annealing of Al–Nb and Al–Ta thin films

Abstract

Ion-beam mixing and thermal annealing of thin, alternating layers of Al and Nb, as well as Al and Ta, were investigated by selected area diffraction and Rutherford backscattcring. The individual layer thicknesses were adjusted to obtain the overall compositions as Al₃Nb and Al₃Ta. The films were ion mixed with 1 MeV Au⁺ ions at a dose of 1 × 10¹⁶ ions cm⁻². Uniform mixing and amorphization were achieved for both Al−Nb and Al−Ta systems. Equilibrium crystalline A₁₃Nb and Al₁₃Ta phases were formed after annealing of ion mixed amorphous films at 400 °C for 1 h. Unmixed films, however, remained unreacted at 400 °C for 1 h. Partial reaction was observed in the unmixed film of Al–Nb at 400 °C for 6 h. After annealing at 500 °C for 1 h, a complete reaction and formation of Al₃Nb and Al₃Ta phases in the respective films were observed. The influence of thermodynamics on the phase formation by ion mixing and thermal annealing is discussed.