X-ray study of W(001) with and without hydrogen

Technical Report · Thu Jun 01 04:00:00 EDT 1989

OSTI ID:5215787

Evans-Lutterodt, K; Birgeneau, R J; Specht, E D; Chung, J W; Brock, J D

The authros carried out synchrotron x-ray-diffraction studies of the clean W(00 1) metal surface reconstruction transition as a function of temperature, and of the room-temperature phases and phase transitions of W(001) with submonolayer coverages of hydrogen. They were able to measure one and one-half decades of change in diffraction line width, and three decades in the amplitude. The detailed dependences of the surface peak widths are consistent with the predictions of the two-dimensional XY model with cubic anisotropy to leading order. They also found that the clean surface structure is commensurate at all temperatures measured, above and below the transition temperature. For hydrogen covered W(001), the data suggest a simple picture in which at very low coverages there is a trade-off with increasing coverage, analogous to that in a two-phase coexistence region, between hydrogen-poor and hydrogen-rich regions. With further increase in coverage, the surface layer exhibits a commensurate-incommensurate transition which, rather than being a solid-solid transition as previously assumed, is actually a lattice-gas melting transition into a domain-wall fluid phase. Such surface domain-wall fluid phases should occur commonly in chemisorbed systems.

• Research Organization: Massachusetts Inst. of Tech., Cambridge, MA (USA). Research Lab. of Electronics
• OSTI ID: 5215787
• Report Number(s): AD-A-212278/6/XAB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
CHEMICAL REACTIONS
COHERENT SCATTERING
DIFFRACTION
ELEMENTS
HYDROGENATION
LAYERS
METALS
MOLECULAR STRUCTURE
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
SCATTERING
SOLIDS
SURFACES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENTS
TRANSITION TEMPERATURE
TUNGSTEN
X-RAY DIFFRACTION