X-ray study of molecular oxygen adsorbed on graphite

P. A. Heiney, P. W. Stephens, S. G J Mochrie, Jun Akimitsu, R. J. Birgeneau, P. M. Horn

Research output: Contribution to journalArticle

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Abstract

We have performed a detailed X-ray diffraction study of O2 adsorbed on UCAR-ZYX and Le Carbon Lorraine vermicular exfoliated graphite between 15 and 50 K. At least four phases of physisorbed oxygen are found. The monolayer δ phase consists of a centered parallelogram lattice, with the molecular axes parallel to the graphite surface. The data are consistent with a triple point at 26 K. The melting transition at a coverage of one monolayer appears to be first order. At higher coverages the molecules undergo a lying-down to standing-up transition; the higher coverage ζ phase froms an approximately triangular lattice with the molecular axes perpendicular to the graphite surface. Satellite peaks around the (1, 0) Bragg peak indicate, however, that this cannot be a simple triangular lattice; possible explanations include successively incommensurate layers or a sinusoidal density modulation. For coverages in the two-layer region the ζ phase modulation peaks disappear at 37 K, and at 40 K the adsorbed oxygen appears to undergo a first order melting transition into a fluid phase. With increasing coverage, the 2D X-ray diffraction profiles and phase boundaries do not connect smoothly onto those of the 3D α and β phases. At low temperatures (T <30 K) the ζ phase always coexists with bulk crystallites; for temperatures near the 2D melting transition the 3D peaks are not observable. These data, taken together with the heat capacity results, suggest a wetting transition with only the bilayer lamellar phase or bulk O2 being stable at low temperatures.

Original languageEnglish
Pages (from-to)539-564
Number of pages26
JournalSurface Science
Volume125
Issue number2
DOIs
Publication statusPublished - Feb 2 1983
Externally publishedYes

Fingerprint

Graphite
Molecular oxygen
Melting
graphite
X rays
Monolayers
oxygen
Oxygen
melting
X ray diffraction
x rays
Phase modulation
Phase boundaries
Crystallites
Temperature
Specific heat
Wetting
parallelograms
Carbon
Modulation

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Condensed Matter Physics
  • Surfaces and Interfaces

Cite this

Heiney, P. A., Stephens, P. W., Mochrie, S. G. J., Akimitsu, J., Birgeneau, R. J., & Horn, P. M. (1983). X-ray study of molecular oxygen adsorbed on graphite. Surface Science, 125(2), 539-564. https://doi.org/10.1016/0039-6028(83)90584-8

X-ray study of molecular oxygen adsorbed on graphite. / Heiney, P. A.; Stephens, P. W.; Mochrie, S. G J; Akimitsu, Jun; Birgeneau, R. J.; Horn, P. M.

In: Surface Science, Vol. 125, No. 2, 02.02.1983, p. 539-564.

Research output: Contribution to journalArticle

Heiney, PA, Stephens, PW, Mochrie, SGJ, Akimitsu, J, Birgeneau, RJ & Horn, PM 1983, 'X-ray study of molecular oxygen adsorbed on graphite', Surface Science, vol. 125, no. 2, pp. 539-564. https://doi.org/10.1016/0039-6028(83)90584-8
Heiney PA, Stephens PW, Mochrie SGJ, Akimitsu J, Birgeneau RJ, Horn PM. X-ray study of molecular oxygen adsorbed on graphite. Surface Science. 1983 Feb 2;125(2):539-564. https://doi.org/10.1016/0039-6028(83)90584-8
Heiney, P. A. ; Stephens, P. W. ; Mochrie, S. G J ; Akimitsu, Jun ; Birgeneau, R. J. ; Horn, P. M. / X-ray study of molecular oxygen adsorbed on graphite. In: Surface Science. 1983 ; Vol. 125, No. 2. pp. 539-564.
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