The Ehrlich-Schwoebel barrier 𝐸 .: was determined for all step-down diffusion processes. , It corresponds to the additional energy barrier that a diffusing atom has to overcome when descending a step and was calculated by subtracting the terrace self-diffusion barrier 𝐸 $ ;"9 (>899$!8) from the barrier of the step-down process 𝐸 $ ;"9 (:%8@52"A7) :