X-ray study of molecular oxygen adsorbed on graphite

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


78 被引用数 (Scopus)


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.

ジャーナルSurface Science
出版ステータスPublished - 2月 2 1983

ASJC Scopus subject areas

  • 凝縮系物理学
  • 表面および界面
  • 表面、皮膜および薄膜
  • 材料化学


「X-ray study of molecular oxygen adsorbed on graphite」の研究トピックを掘り下げます。これらがまとまってユニークなフィンガープリントを構成します。