Samples with a 100nm Co over-layer, which had been subjected to rapid thermal annealing (400 to 650C, 60s), were analyzed by using mass and energy dispersive recoil spectrometry. Separate characterizations of the C, O, Co, Ga, and As depth distributions were carried out. It was found that As migrated to the surface at annealing temperatures which were higher than 450C. The composition at various depths was determined at a number of temperatures. On the basis of Arrhenius plots, the apparent activation energies were estimated to be equal to about 0.6eV for phase formation and equal to 1.3eV for diffusion. The X-ray diffraction data indicated that CoGa and CoAs were present in all of the annealed samples. Scanning electron microscopy showed that the surface was reticulated after heat treatment, and that grain growth occurred at higher temperatures.

M.Hult, H.J.Whitlow, M.Ostling, M.Andersson, Y.Andersson, I.Lindeberg, K.Stähl: Journal of Applied Physics, 1994, 75[2], 835-43