Why is surface diffusion the same in ultrastable, ordinary, aged, and ultrathin molecular glasses?

Recently Fakhraai and coworkers measured surface diffusion in ultrastable glass produced by vapor deposition, ordinary glass with and without physical aging, and ultrathin films of the same molecular glass-former, N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD). Diffusion on the surfaces of all these glasses is greatly enhanced compared with the bulk diffusion similar to that previously found by others, but remarkably Read more about Why is surface diffusion the same in ultrastable, ordinary, aged, and ultrathin molecular glasses?[…]