Thin films of La on polycrystalline Mo surfaces were investigated by using combined Auger electron spectroscopy and Ar sputtering, quadrupole mass spectrometry, neutron activation analysis, small-angle X-ray diffraction, field emission microscopy, and scanning electron microscopy. A detailed analysis of depth profiles for 800 to 1300K indicated that this could be attributed to both bulk and grain boundary diffusion. The grain boundary diffusivity in this range could be expressed by:

D (cm2/s) = 1.2 x 10-6 exp[-1.07(eV)/kT]

G.S.Rao, C.V.Dharmadhikari, A.S.Nigavekar: Journal of Vacuum Science and Technology A, 1989, 7[5], 3005-12