| 1. |
- Hanson, Maj, 1939, et al.
(author)
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Influence of post-annealing on the properties of Fe50Pt50 film and submicron size particles
- 2004
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In: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853. ; 272-276:SUPPL. 1, s. e1297-
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Journal article (peer-reviewed)abstract
- The magnetic properties of a 48 nm thick Fe50Pt50 film and submicron size elements made of the film were investigated. The initial film was grown by DC magnetron sputtering and post-annealed during 30 min at 300°C. Arrays of circular dots with diameters d = 200, 300 and 550 nm and a reference sample (diameter 1.7mm) were made of the film by electron lithography and Ar ion milling. After structural analysis by X-ray diffraction (XRD) and characterization by magnetization measurements and magnetic force microscopy, all samples were further annealed during 30min at 600°C. The XRD scans show that this led to an improvement of the crystalline quality in all samples, to a degree depending on the size of the dots. Both the structural and magnetic measurements imply that after the second heat treatment all samples have the easy magnetocrystalline direction (c-axis) mainly in the plane of the film, while the initial structures were characterized by a random distribution of c-axes.
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| 2. |
- Hanson, Maj, 1939, et al.
(author)
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Magnetic properties of epitaxial Ni(001) films and sub-micron particles
- 2001
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In: Journal of Magnetism and Magnetic Materials. - 0304-8853 .- 1873-4766. ; 236, s. 139-50
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Journal article (peer-reviewed)abstract
- The magnetic properties of Ni particles with well-defined geometry, prepared by electron lithography from epitaxial Ni(001) films of thickness 50 and 60 nm were studied. The particles were circles with diameters 0.6 m and rectangles with sides 0.9 m and 0.3 m, that were positioned in square and rectangular lattices, having lattice constants about twice the particle dimensions. Reference samples and particles with the lattices oriented along the [100] and [110] directions were prepared. Hysteresis curves were obtained for particles and reference samples, in the field range 2T at temperatures between 50 and 300 K. The particles were further imaged by magnetic force microscopy. The coercivities of the particles are about the same as that of the reference samples, being of the order of 10 mT at room temperature and increasing with decreasing temperature. This may be explained by the temperature dependence of the magnetic anisotropy of the Ni film, estimated to K1=-12.5, -12.8 and -87.6 kJ m-3 at 295, 250 and 50 K, respectively. Whereas the hysteresis curves of the particles are governed by the intrinsic properties of the starting film in low fields, the decreased lateral size influences the behaviour in higher fields as demagnetization effects and features characteristic for annihilation and nucleation of domain walls. One of the samples, rectangles with the long axis alone the [110] direction, has a significantly higher remanence and coercivity than the others. The magnetic images show that the demagnetized state of this sample comprises both single-domain and multidomain particles. Corresponding images showed only multidomain particles in all other samples. Thus it was concluded that the actual size (0.9 m0.3 m50 nm) is close to the critical size for single domains in Ni
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| 5. |
- Madsen, L.D., et al.
(author)
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Assessment of MgO(1 0 0) and (1 1 1) substrate quality by X-ray diffraction
- 2000
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In: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 209:1, s. 91-101
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Journal article (peer-reviewed)abstract
- MgO{1 1 1} and {1 0 0} crystals are widely used as substrates for thin film growth, in many different areas of research such as superconductors, and other oxide, metal and nitride films, multilayers and superlattices. Since the quality of the thin film can be strongly dependent on that of the substrate, the optimal film properties will only be fully conceived if the substrate is well characterized in advance. The goal of this work was to create a characterization method which was inexpensive, fast, efficient, and of course nondestructive, for assessing imperfect metal-oxide substrates. X-ray diffraction (XRD) was chosen because of its low cost, simplicity, nondestructiveness, and the fact that we have access to many different parameters using the same instrument. The miscut of the MgO crystals studied herein were characterized with a high resolution of 0.01°. The number of domains, their distribution and their size were characterized by ?-f maps and topography measurements. In this case, atomic force microscopy (AFM) was found to be more appropriate for assessing roughness than X-ray reflectivity measurements.
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| 6. |
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| 7. |
- Miniotas, A, et al.
(author)
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Misfit strain induced lattice distortions in heteroepitaxially grown LaxCa1-xMnO3 thin films studied by extended x-ray absorption fine structure and high-resolution x-ray diffraction
- 2001
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 89:4, s. 2134-2137
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Journal article (peer-reviewed)abstract
- Mn-O and Mn-Mn interatomic distances were determined in LaxCa1-xMnO3 films grown heteroepitaxially on single crystal SrTiO3 and LaAlO3 substrates by molecular beam epitaxy. Mn-O bond lengths were found to be fixed at similar to1.975 Angstrom for both types of substrates, while the Mn-Mn distance was detected to be larger for films grown on SrTiO3 substrates than for films grown on LaAlO3. The deviation of Mn-Mn interatomic distances, and subsequently Mn-O-Mn bond angles, in epitaxial LaxCa1-xMnO3 films is attributed to the misfit strain: compressive for LaAlO3 and tensile for SrTiO3 substrates. (C) 2001 American Institute of Physics.
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| 8. |
- Paskova, Tanja, et al.
(author)
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Influence of growth rate on the structure of thick GaN layers grown by HVPE
- 2000
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In: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 208:1, s. 18-26
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Journal article (peer-reviewed)abstract
- Thick GaN films grown by hydride vapour phase epitaxy have been investigated by cathodoluminecsence, X-ray diffraction, and photoluminescence. Cross-sectional studies of thick GaN layers grown on sapphire without buffers reveal three zones: a highly disordered interface region, a columnar defective region and a good quality main region of the layer. The influence of the highly doped columnar region on the surface morphology and crystal structure of the layers has been studied. We show that the columnar region influences the material quality more strongly in thinner films. Thicker layers exhibit improved morphology with lower surface pit density and better crystal quality shown in photoluminescence and X-ray diffraction spectra. The relationship between the near-interface columnar structures and surface pits is revealed. A strong effect of the growth rate on the structure of thick layers is found. The results suggest that GaN layers with optimum crystalline quality may be obtained by varying the growth rate during growth.
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| 9. |
- Svedberg, E B, et al.
(author)
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Asymmetric interface broadening in epitaxial Mo/W (001) superlattices grown by magnetron sputtering
- 1998
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In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Institute of Physics (AIP). - 0734-2101 .- 1520-8559. ; 16:2, s. 633-638
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Journal article (peer-reviewed)abstract
- The interfacial structure in epitaxial Mo/W(001) superlattices, grown by magnetron sputtering on MgO(001) substrates has been studied. The films were grown in Ar and Kr discharges at a substrate temperature of 700 degrees C, and the as-deposited samples were analyzed by x-ray diffraction and found to be epitaxial with no high-angle grain boundaries. The degree of interfacial intermixing, caused by fluxes of different energetic species impinging on the growth surface, was estimated using a combination of Monte Carlo binary collision computer codes and a gas scattering computational model. In the Ar discharge case, large asymmetries in the Mo/W and W/Mo interfaces were found, with the W/Mo interface being more than a factor of 2 broader than the Mo/W interface. Simulations of x-ray reflectivity curves using the calculated interface profiles as input parameters without any additional fitting parameters agreed very well with measured data. The overall good fit between the calculated and measured reflectivity curves using the calculated compositional profiles is an indicator that the growth simulations using TRIM based codes provides interface profiles that are reasonably accurate, which can be used as a starting point for further refinements of the details of the interface structures. (C) 1998 American Vacuum Society.
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