HIGH-RESOLUTION LOW-ENERGY ELECTRON-DIFFRACTION STUDY OF PT(110)(1X2) TO (1X1) PHASE-TRANSITION

We present a high-resolution low-energy electron diffraction study of the clean Pt (110) reconstructed (1X2) to (1X1) phase transition and its critical phenomena. The phase transition is shown to he a continuous order-disorder type with critical temperature TC~960K. The critical exponents β, y and v extracted from the (01/2) superlattice beam are consistent with the 2D Ising class. The observed critical scattering maximizes around Tc and is limited by the finite size of the (1X2) ordered region. The line shape of the (01/2) beam can be described by a power Lorentzian with decreasing power m as T→ Tc. At T>TC, where only the short-range ordering exists, the structure factor of the superlattice, represented by the (01/2) beam, shows scaling and isotropic behavior even though the broadening along the [110] and the [001] directions is anisotropic. The scaling function can be well fitted by either Fisher and Burford's form or a Lorentzian. © 1990, American Vacuum Society. All rights reserved.