Multiple reflections in an optical retarder investigated by spectroscopic transmission ellipsometry

The response of the ellipsometric parameters as a function of wavelength has been derived for an optical retarder. Experimental results in the wavelength region 400–1000 nm are given, these are in agreement with the derived formalism

The influence of cell window imperfections on the calibration and measured data of two types of rotating-analyzer ellipsometers

A graphical method has been developed to determine the plane of incidence in the presence of cell windows with small retardation. For two types of rotating-analyzer ellipsometers, expressions have been derived that relate the experimental parameters and the elements of the Mueller imperfection matrices of the windows. These matrices can be determined by measuring with and without cell windows. Measurements have been performed with three samples with different optical constants

Spectroscopic ellipsometric investigation of the clean and oxygen exposed Ni(110) surface

Dynamical ellipsometric investigations of the initial oxidation of the Ni(110) surface have been performed. Ellipsometry appears to be well suited to distinguish between chemisorbed oxygen and nickel oxide on the surface. Annealing at 740 K causes the nucleation of nickel oxide to proceed faster than at 570 K. After equal exposures however, the nucleation is slower with an oxygen pressure of 2 × 10−7 Torr than with a pressure of 1.3 × 10−8 Torr. Spectroscopic ellipsometric measurements (400–800 nm) have been performed on clean and oxygen-exposed (at saturation) Ni(110) surfaces. The complex dielectric function of the clean surface has been determined. To explain the results of the oxygen exposed surface a model is discussed — a surface layer with a thickness of 6 Å and a mixture of 90% NiO and 10% Ni — in which changes with substrate optical properties are taken into account

On the kinetics of oxidation of austenitic stainless steels AISI 304 and incoloy 800H

The interaction of oxygen with clean surfaces of stainless steels has been studied by spectroscopic ellipsometry and AES. The reaction involves chemisorption and dissolution of oxygen into the surface of the metal via a place-exchange mechanism. Oxide thickening occurs via cation and anion migration under the influence of an electric field. The activation energy increases with increasing oxide thickness and the final activation energy equals the energy needed to break the bonds between oxygen and metal ions in the oxide, suggesting diffusion via lattice sites

Development and application of an experimental concept for surface characterization of semiconductor based substrates using scanning electrochemical microscopy

In this work, evaluation of the applicability of electrochemical scanning microscopy (SECM) for semiconductor industry-relevant thin film materials was carried out. These investigations were focused on the local electrochemical characterization of electrodeposited copper layers and their growth behavior on a variety of barrier materials such as Pt, Ru, TiN, TaN, Ta, Ti, W, and TiW. A special holding device for wafer-based samples was developed to be able to handle this combined task on a laboratory scale. This multipurpose cell provided electrical contact for the thin films deposited on the silicon substrate while simultaneously sealing the sample with only a small exposed area without any complex sample preparation. Based on preliminary studies, it could be shown that local surface characterization by means of SECM as well as electrochemical copper deposition in a commercial laboratory tool on the aforementioned materials with this cell was feasible. Consequently, deposition protocols for electroplating of dense Cu films with good adhesion on various barrier materials were developed for surface characterization studies with SECM. It became apparent that conventional commercial acidic copper electrolytes were only suitable for deposition of dense and adherent films on Cu or platinoids such as Ru or Pt. In contrast, direct electroplating on Ta-, Ti- and W-based barrier thin films had shown that the deposition of dense and adherent layers was heavily dependent on potential, on electrolyte composition and process handling and was therefore inappropriate for galvanic coating on a wafer scale. On the other side, implementation of the multipurpose cell into the SECM setup revealed that the local surface characterization of semi-precious metals in conventional feedback mode was strongly restricted. It could be shown, that oxide formation and corrosion of the thin film surface on the basis of surface interaction effects in aqueous solution had a strong influence on the measurement results. Moreover, the local resolution of this technique is limited, since materials with similar conductivity cannot be distinguished as shown by approach curves studies on different metallic thin films such as Ru, Pt, Cu, TiN, TiW, W and TaN. Based on these results a non-destructive measuring concept was developed which would ensure a high electrochemical contrast between different metallic materials without mediator-based surface interferences on the measured signal. It was demonstrated that the hydrogen evolution reaction had the necessary material selectivity according to the results of chronoamperometric studies on different barrier thin films. Therefore, a mediatorless SECM concept in SG/TC mode was characterized from these findings, which showed that the aforementioned requirements were achieved. In the next step, the measurement concept was used for the electrochemical characterization of the growth of direct electroplated Cu on Ru thin films. This model system was selected since Ru did not restrict the composition of the Cu electrolyte. Therefore, it was possible to study the influence of a grain refiner such as citric acid on the early electrocrystallization stage of Cu on Ru. In a preliminary SEM-supported study, it was shown that citric acid had a strong impact on the nucleation since it effectively inhibited grain growth in the deposition process. Thus, nanocrystalline and adherent Cu layers with a grain radius of 10 nm could be formed on pure Ru surface. Since the local resolution of the SECM is dependent on the probe size, ultramicroelectrodes with a size of rtip < 10 nm are required. The fabrication of electrodes of this dimensions cannot be accomplished with existing methods. In order to electrochemically characterize the nucleation behavior of Cu on foreign substrates electrochemically, new manufacturing processes for ultramicroelectrodes in the lower nanometer range have to be developed

On the oxide formation on stainless steels AISI 304 and incoloy 800H investigated with XPS

The influence of cold work on the initially formed oxide layer on the stainless steels AISI 304 and Incology 800H has been studied by XPS. Oxidations were performed at pressures of 10-6-10-4 Pa and temperatures of 300–800 K. All samples showed a similar oxidation behaviour. The oxidation rates of iron and chromium are of the same order of magnitude at temperatures below 650 K. Subsequent oxidation results in an iron oxide on top of a chromium oxide layer. At temperatures above 650 K the metal surface becomes enriched in chromium, which is preferentially oxidized at these temperatures and pressures. Even prolonged oxidation does not result in an iron-rich oxide surface. Nickel has never been found in its oxidized form. The binding energy of oxygen, in the various oxide layers, is independent of the extent of oxidation and is 530.6 eV

Progesterone receptors in development and metatstais of endometrial cancer

Many women may acquire endometrial cancer during their life. The vast majority of these women will be cured because of early detection of the disease. As in most types of cancer however, the main cause of death lies in metastasis of the primary tumor to other sites in the body. In approximately 25% of endometrial cancer patients, the tumor has spread beyond the uterus at the time of initial surgical treatment. During endometrial carcinogenesis, the balance between estrogen and progesterone is of great importance. This is indicated by the fact that virtually all risk factors for endometrial cancer are linked to a surplus of estrogenic effects that are not balanced by appropriate progestagenic effects. Also during further development and progression of endometrial cancer, steroid receptor signaling has many important effects. The major research question of this thesis is summarized as follows: what is the effect of loss of progesterone regulation due to loss of PR expression during development of endometrial cancer? More specifically, the questions that this thesis addresses are: 1) Is loss of PR expression in endometrial cancer linked to development of endometrial cancer to a more advanced stage? 2) What are the effects of changes in expression of PRA and PRB on invasion and metastasis of endometrial cancer? 3) What is the effect of progesterone on invasion and metastasis of endometrial cancer cells that express different PR isotypes? 4) Does any crosstalk exist between PR signaling and Wnt signaling