摘要
Surface self-diffusion anisotropy of tungsten on W(112)plane has been measured along(Ⅱ)and across(丄)channels existed on this plane by using the field emission fluctuation method in two forms of the probeholes.In the round probehole the thermal activation energy E=13.0kcal,and the prefactor of the surface self-diffusion coefficient Dq=^.5X 70_7cm2s-1;in the long narrow rectangular slit,E(Ⅱ)=13.2kcal,D0(Ⅱ)=7.1×10-7crr^and E(丄)=6.2kcal,Do(丄)=1.8×10^(-9)cm^(2)s^(-1) at T=500-700K.The experimental data suggest that a W atom diffusing across channels should not climb over the channel wall,which would certainly require a much higher activation energy,but instead,displace an atom in the wall.This process reqwes a much smaller activation energy;however,since it involves concerted motion of at least two atoms,it will also have a much smaller prefactor.
