Une détermination du coefficient d'auto-diffusion de surface du molybdène

A recent study on the morphological evolution of a metal tip has shown that free evaporation must have a vital influence on the determination of the surface self-diffusion coefficient D_s in the high temperature region. We now present a method which enables the experimental determination of D_s: (1) in the presence of an evaporation, and (2) in a relatively great region of temperature. As an example, D_s of molybdenum has been measured. We obtain: (1) activation energy Q_s = 48.3 kcal/mole and diffusivity D_o = 0.3 cm²/sec for T < 0.6T_F (T_F melting temperature), and (2) Q_s = 76.7 kcal/mole and D_o = 690 cm²/sec for 0.65 T_F < T < 0.85 T_F; which indicate a change of the diffusion mechanism at about 0.65 T_F.