Subsurface Manipulation

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Science  09 Dec 2005:
Vol. 310, Issue 5754, pp. 1587
DOI: 10.1126/science.310.5754.1587d

The movement of hydrogen into and out of the bulk regions of metals is important in hydrogen storage, metal embrittlement, and fuel cell reactions. Sykes et al. used voltage pulses delivered via a scanning tunneling microscope tip to manipulate subsurface hydrogen atoms. They applied bias pulses of >0.5 V to a Pd(111) surface held at 4 K that had had hydrogen removed from its near-surface region by oxygen treatment. These bias pulses were able to excite residual hydrogen atoms in the bulk (which has a population of one H atom per 2000 Pd atoms) and allowed these atoms to move into more energetically favorable subsurface sites. The subsurface hydride depleted the surface Pd atoms of charge and caused an outward surface relaxation of Pd atoms of 0.1 to 0.6 Å. Surface hydrogen also tended to move away from these regions to leave behind ordered arrays of overlayer vacancies. — PDS

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.0506657102 (2005).

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