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Effect of Annealed (0001) α-Al_2O_3 Surfaces on Heteroepitaxial Growth of Silver Nanoparticles

100%

Al-Mohammad A.

Acta Physica Polonica A

2009

vol. 115

issue 3

679-684

The effect of annealed (0001) α -Al_2O_3 surfaces on heteroepitaxial growth of silver nanoparticles were analysed by reflection high-energy electron diffraction, transmission electron microscope and selected area electron diffraction. Ag nanoparticles were deposited on 1× 1 stoichiometric and reconstructed (111)Al//(0001) α -Al_2O_3 with the Knudsen cell. The maximum cluster density method and the Lifethenz theory of Van der Waals energy were used to investigate the Ag//(0001)α -Al_2O_3 interface parameters. The growth modes, lattice parameters, nanoparticle forms and sizes are strongly dependent on the substrate surface structures. Initially, three-dimensional islands of Ag nanoparticles grow on both kinds of surfaces with partial hexagonal shapes. Ag nanoparticles on stoichiometric surface create the (111)Ag//(0001)α -Al_2O_3 interface without any preferred epitaxial direction. On this surface, Gaussian distribution is characteristic of an atom-by-atom growth mode with density of Ag nanoparticles lower than saturation density while a coalescence growth mode appears due to binary collisions between Ag nanoparticles accompanied by a liquid-like behaviour after saturation density. In case of reconstruction substrates, the epitaxial relationships between Ag nanoparticles and the surface are formed (111)Ag//(0001)α -Al_2O_3, 〈01\bar(1)〉Ag//[12\bar(3)0]α -Al_2O_3 or 〈01\bar(1)〉Ag//[1\bar(1)00]α-Al_2O_3. The Ag nanoparticles make rotation with angles between ± 6° around the epitaxial orientations 〈1\bar(1)00〉 or 〈12\bar(3)0〉. Only the atom-by-atom growth mode were found at all Ag nanoparticles growth processes.

Study of Ultrathin In-Ag Layers οn Tungsten by Means of Surface Spectroscopy Techniques

100%

Bukaluk A., Trzcinski M., Okulewicz K.

Acta Physica Polonica A

2008

vol. 114

issue S

S-17-S-28

Auger electron spectroscopy, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, scanning tunnelling microscopy, low energy electron diffraction, and thermodesorption methods were used to investigate the process of growth of ultrathin In films and formation of In-Ag surface alloys on tungsten substrate. Several indium layers, having coverage ranging from 0.2 to 0.8 ML were deposited on tungsten substrate in room temperature. It was found that at the lowest coverages (Θ= 0.1-0.3 ML) indium atoms form (3×1) structure, characterized by very sharp low energy electron diffraction patterns. With increasing Θ they tend to form densely packed islands interpreted as slightly distorted In(111) monolayers. Surface diffusion of In onto the tungsten surface was studied by using ESCA imaging property of SCIENTA ESCA200 instrument. Measuring the photoelectron intensity as a function of two spatial coordinates and the energy, we observed movement of In atoms on the tungsten surface. On the basis of the change of surface coverage with distance surface the diffusion coefficient was evaluated at the temperature range of 400-700 K. Intermixing of ultrathin films of indium and silver, after their surface diffusion from the sample edges to the centre of the tungsten surface, were observed by using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and the Auger electron spectroscopy methods. Intermixing was controlled by means of photoemission spectra from the valence states and the In 4d level, as well as by X-ray photoelectron spectroscopy studies of indium and silver core levels excited by Al K_α source.

Structural and Magnetic Properties of MBE Grown (Fe/Pt) (111) Multilayers

63%

Marynowska A., Dynowska E., Lewińska S., Seki T., Takanashi K., Kanak J., Pietruczik A., Aleszkiewicz P., Wawro A., Ślawska-Waniewska A., Baczewski L.

Acta Physica Polonica A

2016

vol. 130

issue 6

1363-1370

Series of Al₂O₃(0001)/Pt/(Fe/Pt)ₙ/Pt multilayers with variable number of bilayers n and thicknesses of individual layers were grown using molecular beam epitaxy to investigate influence of buffer layer structure, number of bilayers, and individual layer thickness on their structural and magnetic properties. Both columnar and monocrystalline 10 nm Pt (111) buffer layers were used in the experiment. Structure of Pt buffer layer determined the roughness of Fe/Pt interfaces and consequently magnetic properties of the multilayers. When multilayers were deposited on columnar Pt buffer layer, we observed increase of Fe/Pt interfaces roughness with increasing number of bilayers to values exceeding the nominal Fe/Pt bilayer thickness in the upper part of the sample volume, which resulted in the increment of coercivity in the sample with n=15 determined from hysteresis loops measured for perpendicular orientation of magnetic field. When Fe/Pt multilayers were deposited on monocrystalline Pt buffer layer, Fe/Pt interfaces were smooth regardless the number of bilayers. All samples, despite of the quality of buffer layer, number of bilayers, and individual layer thickness revealed easy magnetisation axis oriented in the sample plane.

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3 Acta Physica Polonica A

1 2016

1 2009

1 2008

1 Al-Mohammad A.

1 Aleszkiewicz P.

1 Baczewski L.

1 Bukaluk A.

1 Dynowska E.

1 Kanak J.

1 Lewińska S.

1 Marynowska A.

1 Okulewicz K.

1 Pietruczik A.

1 Seki T.

1 Takanashi K.

1 Trzcinski M.

1 Wawro A.

1 Ślawska-Waniewska A.

Search results

Effect of Annealed (0001) α-Al_2O_3 Surfaces on Heteroepitaxial Growth of Silver Nanoparticles

Study of Ultrathin In-Ag Layers οn Tungsten by Means of Surface Spectroscopy Techniques

Structural and Magnetic Properties of MBE Grown (Fe/Pt) (111) Multilayers