Structural study of thin MgO layers on Ag(001) prepared by either MBE or sputter deposition

Growth, morphology and structure of thin MgO films prepared on Ag(001) substrates by different preparation procedures have been investigated by AES, LEED and modulated electron emission. Oxide layers were prepared by Mg MBE in an oxygen atmosphere or sputter deposition from bulk MgO target. In both cases stoichiometric MgO forms, which initially grows in a rocksalt tetragonally distorted structure. For 3-ML films, 3.6% expansion of the interlayer spacing along the growth axis has been , measured. The misfit strain progressively reduces as the film thickness increases, and the equilibrium spacing is completely recovered at 8-10 NM thickness. In spite of the similarity in structure and strain, different deposition procedures lead to different film morphology. Sputter deposited films only partially cover the substrate, Fractional coverage (50%) has been evaluated for the 3-ML thick Mai, and full coverage only occurs at approximately 10 ML thickness. The NSE procedure results in almost complete layers. Fourfold broadening of spot profiles has been observed in LEED patterns of both MBE and sputter deposited films, indicating the occurrence of a similar large-scale atomic arrangement and surface morphology, (C) 2001 Elsevier Science B.V All rights reserved.