Vibrational properties of ultrathin Ga2O3 films grown on Ni(100)

Growth and vibrational properties of ultrathin films of Ga2O3 on Ni(100) were investigated in the temperature range of 80-1200 K by using electron energy loss spectroscopy (EELS), Auger electron spectroscopy, and low energy electron diffraction (LEED). At 80 K, a 30 Angstrom thick Ga layer was deposited on the c(2 x 2)-oxygen structure prepared on Ni(I 00). Afterwards, the Ga layer was oxidized with oxygen until saturation. At 80 K, both the Ga layer and the oxidized Ga layer are amorphous. After annealing to room temperature a energy loss at similar to640 cm(-1) occurs. This loss is assigned to a vibrational excitation of Ga-O bonds in the Ga-oxide structure. Further annealing up to 700 K leads to the characteristic Fuchs-Kliever phonons of Ga2O3 at 305, 470 and 745 cm(-1) in the EEL spectrum and the LEED pattern of Ga oxide shows a weak diffuse ring structure of domains with long-range order but random orientation with respect to the substrate. The lattice constant is determined to be 2.8 Angstrom which corresponds to the distance between two O2- ions in the oxide lattice. (C) 2002 Elsevier Science B.V. All rights reserved

Growth of ultra thin Ga and Ga2O3 films on Ni(100)

The growth of ultra-thin films of Ga2O3 on Ni(1 0 0) was investigated in the temperature range of 300-800 K by using Auger electron spectroscopy, low energy electron diffraction (LEED) and scanning tunneling microscopy. In addition, the growth of Ga at 300 K was also studied. For the formation of Ga2O3, first at 300 K, a 15 Angstrom thick Ga layer was deposited on the Ni(1 0 0) surface. Oxygen adsorption until saturation leads to the formation of a thin amorphous Ga oxide on the top of a metallic Ga interlayer. Annealing up to 700 K leads to the formation of a well-ordered thin film of gamma'-Ga2O3 which is accompanied by a coalescence and ordering of the Ga2O3 islands. Large terraces are found which are separated by step heights of 2 Angstrom. The LEED pattern shows a 12-fold ring structure, which originates from two domains with hexagonal structure, which are rotated by 90degrees with respect to each other. The lattice constant of the hexagonal unit cells is determined to be 2.8 Angstrom. (C) 2003 Elsevier Science B.V. All rights reserved

The growth of ultrathin Al2O3 films on Cu(111)

The growth of ultrathin films of Al2O3 on Cu(111) in the temperature range 300-1200 K was investigated by using Auger electron spectroscopy (AES), low-energy electron diffraction (LEED) and high-resolution electron energy loss spectroscopy (HREELS). Eight monolayers of a mixture of nickel and aluminum (Ni:Al = 1:2) were deposited on Cu(l 1 1) at 300 K by simultaneous evaporation of both Ni and Al from NiAl crystal material. The bimetal layer was oxidized at 300 K until saturation and annealed gradually to 1200 K. During oxygen adsorption, only aluminum is oxidized. Annealing of the oxidized layer to 1200 K leads to the formation of a well-ordered aluminum oxide. The HREEL spectra show the characteristic Fuchs-Kliever phonons of Al2O3 (410, 620 and 885 cm(-1)). During annealing, Ni diffuses into the Cu(I 1 1) substrate. The LEED pattern of the ultrathin oxide layer has a hexagonal structure with a lattice constant of 3.1 Angstrom, which corresponds to the distance between two oxygen ions in the aluminum oxide. (C) 2002 Elsevier Science B.V. All rights reserved

Growth and oxidation of a Ni3Al alloy on Ni(100)

The growth and oxidation of a thin film of Ni3Al grown on Ni(1 0 0) were studied using Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and high resolution electron energy loss spectroscopy (EELS). At 300 K. a 12 Angstrom thick layer of aluminium was deposited on a Ni(1 0 0) surface and subsequently annealed to 1150 K resulting in a thin film of Ni3Al which grows with the (10 0) plane parallel to the (10 0) surface of the substrate. Oxidation at 300 K of Ni3Al/Ni(1 0 0) until saturation leads to the growth of an aluminium oxide layer consisting of different alumina phases. By annealing up to 1000 K, a well ordered film of the Al2O3 film is formed which exhibits in the EEL spectra Fuchs-Kliewer phonons at 420, 640 and 880 cm(-1). The LEED pattern of the oxide shows a twelvefold ring structure. This LEED pattern is explained by two domains with hexagonal structure which are rotated by 90degrees with respect to each other. The lattice constant of the hexagonal structure amounts to similar to2.87 Angstrom. The EELS data and the LEED pattern suggest that the gamma'-Al2O3 phase is formed which grows with the (1 1 1) plane parallel to the Ni(1 0 0) surface. (C) 2003 Elsevier Science B.V. All rights reserved