Clustering of chemisorbed H(D) atoms on the graphite (0001) surface due to preferential sticking

Phys Rev Lett. 2006 Nov 3;97(18):186102. doi: 10.1103/PhysRevLett.97.186102. Epub 2006 Oct 31.


We present scanning tunneling microscopy experiments and density functional theory calculations which reveal a unique mechanism for the formation of hydrogen adsorbate clusters on graphite surfaces. Our results show that diffusion of hydrogen atoms is largely inactive and that clustering is a consequence of preferential sticking into specific adsorbate structures. These surprising findings are caused by reduced or even vanishing adsorption barriers for hydrogen in the vicinity of already adsorbed H atoms on the surface and point to a possible novel route to interstellar H2 formation.