Physical realization of two-dimensional Ising critical phenomena: Oxygen chemisorbed on the W(112) surface

The continuous reversible order-disorder phase transition of oxygen chemisorbed on the W(112) surface at half-monolayer coverage was studied by low-energy electron diffraction (LEED). The critical phenomena associated with this phase transition are shown to belong to the two-dimensional Ising universality class. An attempt has been made to extract the critical exponents, and the limitations of the LEED system presently used are discussed.