Pattern formation of hydrogen adatom density on Cu(111) using patterns of xenon adatoms as templates.*

We formed grating-like patterns of hydrogen adatom density on Cu(111) by using complementary patterns of xenon adatom density as the template. The template was pre-formed by laser-induced thermal desorption of a Xe monolayer on Cu(111) using the interference pattern of two coherent laser pulses. The ``patterned'' surface was subsequently exposed to hot hydrogen molecules which dissociate and adsorb preferentially on the uncovered part of the surface. We removed the Xe template by laser-induced thermal desorption which left behind a grating-like hydrogen density pattern intact on Cu(111). By following the evolution of hydrogen density gratings on Cu(111) from 153 to 183 K with linear optical diffraction, we found that the diffusion of hydrogen atoms on Cu(111) in this temperature range was characterized by an activation energy barrier E$_{diff}$ = 6.4 kcal/mol (or 279 meV) and a pre-exponential factor D$_{0}$ = 2.0 $\times $ 10$^{-3}$ cm$^{2}$/sec.