Anke Teichert

Surfactant Adsorption at the Metal-Oil Interface

The structure of the adsorbed palmitic acid at the iron oxide/oil interface has been investigated using polarized neutron reflectometry. The palmitic acid was found to be strongly adsorbed at the oxide/oil interface resulting in a monolayer of thickness 16 ± 4 Å for 150 and 500 ppm palmitic acid concentrations (16 ± 5 Å for the 1000 ppm solution). These layer thicknesses suggest tilt for the palmitic acid molecules with respect to the interface. The model also requires a second diffuse layer extending in the bulk oil. The thickness of this diffuse layer was 35 ± 17 Å for the 150 ppm solution and 45 ± 22 Å for 500 and 1000 ppm solution. The composition profiles at the interface suggest a depletion of the oil in the vicinity of the interface as the concentration of palmitic acid increases.

Substrate-stress-induced magnetic and nonmagnetic structural correlations in Fe/Si multilayers

Application of a bias voltage can influence the growth kinetics and thereby the stress in a magnetic multilayer. The inherent structural correlations in turn can influence the magnetic domain structures and thereby the overall device performance. Here, prototypical Fe/Si supermirrors are subjected to stress relaxation during the growth of sequential layers by applying a sufficient substrate bias voltage. A change in the coercivity associated with the grain size variation upon biasing is found. Most interestingly, using polarized neutron scattering, it is possible to identify that the conformal roughness becomes nonconformal with the relaxation of stress within the multilayers. The magnetic domains, on the other hand, always remain nonconformal (independent of the structural change) as they undergo spatial fluctuations around a mean magnetization. This study underscores the importance of the substrate biasing in affecting the structural correlation, which is detrimental to the resultant optical (e.g. supermirror) quality.

Manipulation of uncompensated moments in trained exchange bias system

In an exchange coupled trained antiferromagnet (AF)–ferromagnet (FM) system, we could directly manipulate the uncompensated moments in the AF—resulting in inducing a magnetism within the AF layer. This is made possible by applying an in-plane magnetic field perpendicular to the cooling field HFC. Depth-sensitive polarized neutron scattering experiments in specular and off-specular mode have revealed that this interfacial manipulation could neither restore the untrained state nor could it reinduce the initial asymmetry in magnetization reversal. Our results demonstrate an initiative toward user defined exchange-coupled interfaces for the future.

Stress Reduction in Multilayers Used for X-Ray and Neutron Optics

Multilayer systems have important applications in many areas of X-ray and neutron optics. For some applications the positions of the optical surfaces have to be controlled with accuracies in the sub-nanometre range. For neutron supermirrors with over a thousand layers, stresses above 1000MPa can occur. In addition to bending the substrate such stresses can lead to the films peeling from the substrate, or even to the destruction of the substrate surface, and so must be avoided. After an introduction to stress, this chapter describes how stresses can be reduced to acceptable values and discusses two examples – FeCo/Si polarizing neutron supermirrors and Mo/Si multilayer mirrors for extreme ultraviolet lithography.

Stress dependence in Fe89Co11Fe89Co11–Si multilayers on layer thicknesses

We report on a study of the stress developing in materials which are used for polarising neutron supermirrors. The stress was examined as function of the thickness of Si and Fe89Co11Fe89Co11 layers in multilayer systems. The samples were produced in a triode sputter machine. The bending of the samples was measured on a profilometer and the stress was calculated with the Stoney formula. The samples were characterized with polarized neutron and X-ray reflectometry and XRD. It was found that an increase in layer thickness leads to decreasing compressive stress for FeCo layers and to decreasing tensile stress for Si layers. A formula is given which allows to estimate the resulting stress.

Stress dependence in Fe89Co11–Si multilayers on layer thicknesses

We report on a study of the stress developing in materials which are used for polarising neutron supermirrors. The stress was examined as function of the thickness of Si and Fe89Co11Fe89Co11 layers in multilayer systems. The samples were produced in a triode sputter machine. The bending of the samples was measured on a profilometer and the stress was calculated with the Stoney formula. The samples were characterized with polarized neutron and X-ray reflectometry and XRD. It was found that an increase in layer thickness leads to decreasing compressive stress for FeCo layers and to decreasing tensile stress for Si layers. A formula is given which allows to estimate the resulting stress.

Stress dependence in –Si multilayers on layer thicknesses

We report on a study of the stress developing in materials which are used for polarising neutron supermirrors. The stress was examined as function of the thickness of Si and Fe89Co11Fe89Co11 layers in multilayer systems. The samples were produced in a triode sputter machine. The bending of the samples was measured on a profilometer and the stress was calculated with the Stoney formula. The samples were characterized with polarized neutron and X-ray reflectometry and XRD. It was found that an increase in layer thickness leads to decreasing compressive stress for FeCo layers and to decreasing tensile stress for Si layers. A formula is given which allows to estimate the resulting stress.