A vitrifying structure transition in the Dy/Mo(112) adsorption system

Annealing-driven irreversible structural transitions are studied by low-ene rgy electron diffraction in submonolayer Dy films adsorbed on the Mo(112) s urface. In a wide coverage range theta >0.07, Dy overlayers deposited at lo w temperatures (T approximate to 100 K) are ordered and keep their structur e upon annealing up to 350-600 K. Near theta =0.68, the overlayers are stab le to high-temperature annealing (T-a=1000 K) as well, whereas the denser f ilms are metastable and transform to more stable ordered structures. An unu sual annealing effect is found for theta <0.58: the initially ordered metas table phases are replaced by phases having no extended order, which are ass umed to be two-dimensional glasses. (C) 2001 American Institute of Physics.