Ü. Ugaste

Interdiffusion and Kirkendall-Effect in the Fe-Ni-Cu System

Interdiffusion and Kirkendall-effect in diffusion couples combined from the following binary .and ternary alloys: 5%Fe-65%Ni-30%Cu; 29.5%Ni-S4o/oFe-16.5%Cu; 5O%Ni-5O%Fe; 51%Ni-49%Cu; 29%Ni-71%Cu; 3%Cu-97%Fe and 84%Cu-16%Ni were studied at llOO cc. Kirkendali shift measured by means of very small Th02- was found to be up to 12 fl.Ill. in the diffusion couple So/oFe-6S%Ni-30%Cu vs 29.5%Ni-54%Fe-16.5%Cu during annealing time (196 h). The results are discussed from the viewpoint of the use of an alternative set of effective interdiffusion coefficients, which can be extracted from a single diffusion couple experiment.

Dependence of Diffusion Paths on Thermodynamic Factors in Ternary Systems

The impact of thermodynamic factors on deviation from linearity of diffusion path in the ternary system Cu-Fe-Ni is analyzed. For that the slope function of the diffusion path for the diffusion couples 65Ni30Cu5Fe –29.5Ni16.5Cu54Fe, 49.5Ni50.5Fe – 51Ni49Cu and 84Cu16Ni – 50Ni50Fe, annealed at 1000°C for 196h, were calculated by an approximate equation using only thermodynamic data. Results of the calculation were compared with the values of the slope function obtained directly from experimental data. It is shown that despite of the fact that the tracer diffusion coefficients of the components in the system Cu-Fe-Ni are not equal the coincidence between the calculated and experimental values of the slope function is remarkable. This allows us to conclude that at least in this case the deviation of the diffusion path from linearity depends mainly on the thermodynamic properties of the system.

Concentration dependence of interdiffusion coefficients in Cu-Fe-Ni system

Conventional and effective interdiffusion coefficients have been determined in a Cu-Fe-Ni system for 1000°C based on our experimental data [13] on the distribution of concentrations of components in six diffusion couples of this system. The possibilities of applying these coefficients to interpret peculiar features of interdiffusion in ternary systems are analyzed. It has been demonstrated that effective interdiffusion coefficients are in a certain correlation with thermodynamic characteristics of the system.

Hydrogen Interaction with Point Defects in the Si-SiO2 Structures and its Influence on the Interface Properties

The type and density of the point defects that are generated in the Si surface layer during thermal oxidation depend on the oxidation condition: temperature, cooling rate, oxidation time, impurity content. Interaction between the point defects with extended defects and impurities affects the SiO2 structure and Si-SiO2 interface properties. Hydrogen adsorption on n- and p- type wafers is different. One possible reason for that can be the strength of the magnetic interaction between the hydrogen and paramagnetic impurities of the adsorbent. The influence of point defects and impurities may be diminished and the interface properties improved by an appropriate choice of the oxidation conditions and postoxidation laser irradiation.

Relations between Diffusion Paths and Interdiffusion Coefficients in the Ternary System Fe-Co-Ni

Possible interrelations between diffusion paths and interdiffusion coefficients in the system Fe-Co-Ni are analyzed. It is found that the apparition of a straight line shape of diffusion paths imposes strong demands on the values of the conventional interdiffusion coefficients calculated from the experimental data. The possible consequences of this finding are discussed.

Diffusion Paths in the Ternarysystem Fe-Co-Ni: An Empirical Approach

An empirical approach to the description of diffusion paths in the ternary system Fe-Co-Ni is developed. It is shown that the experimentally determined diffusion path in this system can be described by the universal function, which contains two parameters, extracted from experimental data. The values of these parameters and their possible dependence on initial compositions of diffusion couples are discussed. Using the universal function, typical diffusion paths for the system Fe-Co-Ni have been calculated. It is shown that the calculated diffusion paths are in a qualitatively good agreement with the available experimental data.

Point Defects Interaction with Extended Defects and Impurities and Its Influence on the Si-SiO2 System Properties

The type and density of the point defects that are generated in the Si surface layer during thermal oxidation depend on the oxidation condition: temperature, cooling rate, oxidation time, impurity content. The interaction between point defects with extended defects and impurities affect the Si-SiO2 interface properties. The influence of point defects may be diminished and the interface properties improved by an appropriate choice of oxidation conditions.