Hydrogen Inhibition of Exchange Diffusion on Pt(100)

Field ion microscope observations show that the diffusion rate of Pt atoms on Pt(100) is significantly reduced when the surface is exposed to hydrogen. A hydrogen partial pressure of 1×10^-10Torr causes the exchange diffusion rate to decrease by ~3 orders of magnitude over 2--3 hours. Higher pressures suppress exchange displacements to the point where hopping displacements become energetically accessible. The ability to influence both the displacement rate and the transport mechanism indicates that hydrogen may be used to control thin-film growth at the atomic level.