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

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 backscattering. 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 x 1016 ions cm/sup -2/ . Uniform mixing and amorphization were achieved for both Al--Nb and Al--Ta systems. Equilibrium crystalline Al3Nb and Al3Ta phases were formed after annealing of ion mixed amorphous films at 400 0C for 6 h. Unmixed films, however, remained unreacted at 400 0C for 1 h. Partial reaction was observed in the unmixed film of Al--Nb at 400 0C for 6 h. After annealing at 500 0C 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