Helium Atom Scattering Science

The Science

Step dynamics

We have recently observed new collective surface vibrational modes which propagate along the steps of our surface [59,60]. These modes provide a route to understanding forces at extended surface defects.

Oxygen-induced step doubling

When molecules such as oxygen are added, the step edges meander over the surface and can produce new surface structures. Work is now continuing on new structures that form during the initial stages of metallic oxidation [68].

Inelastic multiphonon scattering

The influence of extended surface defects on multiphonon energy exchange has been measured and compared with theoretical predictions of a classical theory [72]. There is a significant discrepancy between the predictions and our data, which is directly attributable to the modification of the surface vibrational band structure due to the steps.

Hydrogen adsorption

The addition of adsorbed hydrogen to this system brings new topics of interest. We have investigated such phase behavior as the order-disorder transition of the hydrogen overlayer and the nature of hydrogen's diffusion in the low coverage limit [76].

Overlayer templating

It is possible to guide the formation of a novel non-close-packed xenon structure on a stepped nickel surface using an intentionally atomically-patterned substrate. We first pre-adsorb a hydrogen overlayer with the desired symmetry and then use this template to shepherd subsequently adsorbed xenon atoms into a new structure [77].

Self-assembled monolayer dynamics

We have completed some preliminary structural and dynamical studies of organic molecules self-assembled on a flat gold surface [88]. Further experiments are currently underway.

SAM/Au interaction

We have discovered that, contrary to the commonly held belief, the underlying gold substrate does not deconstruct in the presence of a striped phase thiolate monolayer [95].

Oxidation history

We have shown that the oxidation history of a metallic surface has a surprisingly significant impact on its reconstruction behavior [96].

References

59. "Phonons localized at step edges: A route to understanding forces at extended surface defects"

L. Niu, D.J. Gaspar, and S.J. Sibener, Science 268, 847-850 (1995) Abstract

60. "Vibrational dynamics of a stepped metallic surface: Step-edge phonons and terrace softening on Ni(977)"

L. Niu, D.D. Koleske, D.J. Gaspar, and S.J. Sibener, J. Chem. Phys. 102, 9077-9089 (1995) Abstract

68. "Reconstruction kinetics of a stepped metallic surface: step doubling and singling of Ni(977) induced by low oxygen coverages"

L. Niu, D.D. Koleske, D.J. Gaspar, S.F. King, and S.J. Sibener, Surf. Sci. 356 144-160 (1996) Abstract

72. "Inelastic multiphonon helium scattering from a stepped Ni(977) surface"

D.J. Gaspar, A.T. Hanbicki, and S.J. Sibener, J. Chem. Phys. 109 6947-6955 (1998) Abstract

76. "Influence of steps on the interaction between adsorbed hydrogen atoms and a nickel surface"

Aubrey T. Hanbicki, S.B. Darling, D.J. Gaspar, and S.J. Sibener, J. Chem. Phys. 111 9053-9057 (1999) Abstract

77. "Rational design of interfacial structure: Adsorbate-mediated templating"

S.B. Darling, A.T. Hanbicki, T.P. Pearl, and S.J. Sibener, J. Phys. Chem. B 103 9805-9808 (1999) Abstract

88. "Surface vibrations of a highly-ordered low-density alkanethiol monolayer measured using helium atom scattering"

S.B. Darling, A.W. Rosenbaum, and S.J. Sibener, Surf. Sci. Lett. 478 L313-L319 (2001) Abstract

95. "Coexistence of the (23Дж3) Au(111) reconstruction and a striped phase self-assembled monolayer"

S.B. Darling, A.W. Rosenbaum, Yi Wang, and S.J. Sibener, Langmuir 18 7462-7468 (2002) Abstract

96. "Influence of oxygen dissolution history on reconstruction behavior of a stepped metal surface"

T.P. Pearl, S.B. Darling, L. Niu, D.D. Koleske, D.J. Gaspar, S.F. King, and S.J. Sibener, Chem. Phys. Lett. 364 284-289 (2002) Abstract

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	Return to HAS Home Page	last modified: 13-Nov-02

Step dynamics		We have recently observed new collective surface vibrational modes which propagate along the steps of our surface [59,60]. These modes provide a route to understanding forces at extended surface defects.
Oxygen-induced step doubling		When molecules such as oxygen are added, the step edges meander over the surface and can produce new surface structures. Work is now continuing on new structures that form during the initial stages of metallic oxidation [68].
Inelastic multiphonon scattering		The influence of extended surface defects on multiphonon energy exchange has been measured and compared with theoretical predictions of a classical theory [72]. There is a significant discrepancy between the predictions and our data, which is directly attributable to the modification of the surface vibrational band structure due to the steps.
Hydrogen adsorption		The addition of adsorbed hydrogen to this system brings new topics of interest. We have investigated such phase behavior as the order-disorder transition of the hydrogen overlayer and the nature of hydrogen's diffusion in the low coverage limit [76].
Overlayer templating		It is possible to guide the formation of a novel non-close-packed xenon structure on a stepped nickel surface using an intentionally atomically-patterned substrate. We first pre-adsorb a hydrogen overlayer with the desired symmetry and then use this template to shepherd subsequently adsorbed xenon atoms into a new structure [77].
Self-assembled monolayer dynamics		We have completed some preliminary structural and dynamical studies of organic molecules self-assembled on a flat gold surface [88]. Further experiments are currently underway.
SAM/Au interaction		We have discovered that, contrary to the commonly held belief, the underlying gold substrate does not deconstruct in the presence of a striped phase thiolate monolayer [95].
Oxidation history		We have shown that the oxidation history of a metallic surface has a surprisingly significant impact on its reconstruction behavior [96].