GROWTH OF METASTABLE HIGH-ORDER COMMENSURATE OVERLAYERS OF PB ON CU(001)

We studied the growth and ordering of a Pb layer deposited on Cu(001) at 150 K. Contrary to the case of adsorption of Pb at room temperature , islands readily form. These islands order in a high-order commensura te structure of symmetry (square-root 61 x square-root 61)R tan-1(5/6) . We followed the growth of these islands using atom beam scattering. From the measurement of the island diffraction peak profiles we found a power growth law for the mean island-size versus coverage. Upon incr easing the coverage another high-order commensurate structure is forme d, (5 x 5) R tan-1(3/4). All the ordered phases obtained by adsorption at low temperature are metastable.