G. Erdélyi

Determination of diffusion coefficients of Zn, Co and Ni in aluminium by a resistometric method

Abstract The impurity diffusion parameters of Zn, Co and Ni have been determined in aluminium by measurements of electrical resistance. It is shown experimentally that in the case of Co and Ni, surface layers with constant concentrations were formed during the isothermal diffusion treatments and so the resistance measurements made possible the determination of the temperature dependence of the saturation concentrations too. It is also shown that the determination of the diffusion activation energy is possible from resistance measurements when the initial and boundary conditions are not exactly known (but when they do not vary with temperature). The measurements gave for the pre-exponential factors (D 0) and the energies of activation (Q) : D 0 Zn = (0.20 ± 0.08) cm2/s, QZn = (1.25 ± 0.02) eV; D 0co = (141 ± 137)cm2/s, Q Co = (1.75 ± 0.07) eV; D 0 Ni = (4.4 ± 3.l) cm2/s, Q N1 = (1.51 ± 0.06) eV, respectively. The diffusion parameters of Zn and Co are in good agreement with previous results in the literatur...

The temperature dependence of grain-boundary diffusion of 65Zn in polycrystalline aluminium

Abstract It is shown that the penetration plots of the grain-boundary diffusion of 65Zn in polycrystalline Al samples are curved at fixed temperatures and that this upward curvature changes with the annealing time. The penetration profiles can be interpreted in terms of sub-boundary diffusion characterized by the parameter P 1 (= D 1 K 1δ, where D 1 is the boundary diffusion coefficient, K is the segregation factor and δ is the grain-boundary width) as well as by a distribution of diffusion parameters for high-angle boundaries. The range of variation of the diffusion parameters for general large-angle grain boundaries can be characterized by the parameters P 1, P 3 and P 4. The temperature dependence of P 1, P 2 and P 3 has also been determined. It is concluded that if we approximate the penetration function by one effective slope in the B-kinetic regime of grain-boundary diffusion then the weight of different grain boundaries (with different grain-boundary diffusion coefficients) can vary greatly in the ...

On the diffusion of 59Fe into aluminium and Al Mn solid solutions

Abstract The diffusion of 59Fe into pure Al and Al Mn solid solutions has been measured by a tracer-sectioning technique. The penetration plots are fitted by a solution of the diffusion equation according to which the surface flux is controlled by a surface barrier (characterizing the dissolution of tracer atoms from the intermetallic phases formed in the near-surface layer) higher than the diffusion activation energy in the bulk. For annealing times t << τ(τ is the time required to reach the solubility limit just inside the solvent) the solution reduces to that of constant surface concentration, and at much longer t (when the surface layer is depleted) the thin-film solution can also be valid. Detailed measurements have been carried out to investigate the time dependence of the penetration plots; the diffusion coefficients calculated from the above solution were the same (within experimental error) at fixed temperature. The effect of increased grain-boundary and dislocation density in the near-surface la...

Nanoscale investigations of shift of individual interfaces in temperature induced processes of Ni–Si system by secondary neutral mass spectrometry

We describe a method for measurement of nanoscale shift of interfaces in layered systems by a combination of secondary neutral mass spectrometry and profilometer. We demonstrate it by the example of the investigation of interface shifts during the solid state reaction in Ni/amorphous-Si system. The kinetics of the shrinkage of the initial nanocrystalline Ni film and the amorphous Si layer as well as the average growth kinetics of the product phases were determined at 503 K. The results show that nanoscale resolution can be reached and the method is promising for following solid state reactions in different thin film systems.

Connections between thermodynamic quantities and vacancy and diffusion characteristics in binary metallic solid solutions

Abstract With the use of the similarity of interatomic potentials relations concerning vacancy and diffusion characteristics in disordered regular solid solutions have been derived. It has been shown that the vacancy concentration is constant along ifT c (x) = T A + (T B − T A )x + 2ΔT x (1−x), ( T A and T B are the melting points of pure components A and B respectively, and Δ T is proportional to the excess enthalpy of mixing, x is the concentration of the atoms B ) which is proportional to the binding energy of the crystal. The validity conditions of several empirical rules known in the literature are also analyzed. It has been found that the generalization of the well-known rule for self- and impurity diffusion in pure metals has the following form In D 0 z (x) ∼ p Q z (x) T c (x) ( Z = A or B ) where p is a constant for alloys having identical structures ( D 0 z ( x ) and Q z ( x ) denote the preexponential factors and the activation energies respectively). The results calculated from the relations derived were compared with experimental data for tracer diffusion in the systems AgAu, CuNi (having slight deviation from regularity), Pb-Tl (showing ordering phenomena) and AlZn (clustering effects) and a good agreement was found.

Kinetic pathways of diffusion and solid-state reactions in nanostructured thin films

Mass transport and solid-state reactions in nanocrystalline thin films are reviewed. It is illustrated that diffusion along different grain boundaries (GBs) can have important effects on the overall intermixing process between two pure films. These processes can be well characterized by a bimodal GB network, with different (fast and slow) diffusivities. First the atoms migrate along fast GBs and accumulate at the film surface. These accumulated atoms form a secondary diffusion source for back diffusion along slow boundaries. Thus the different GBs of the thin films can be gradually filled up with the diffusing atoms and composition depth profiles reflect the result of these processes. Similar processes can be observed in binary systems with intermetallic layers: instead of nucleation and growth of the reaction layer at the initial interface, the reaction takes place in the GBs and the amount of the product phase grows by the motion of its interfaces perpendicular to the GBs. Thus, the entire layer of the pure parent films can be consumed by this GB diffusion-induced solid-state reaction (GBDIREAC), and a fully homogeneous product layer can be obtained.

Investigations of diffusion kinetics in Si/Ta/Cu/W and Si/Co/Ta systems by secondary neutral mass spectrometry

Proper understanding of the degradation mechanisms and diffusion kinetics of copper and cobalt interconnections for advanced microelectronics is important from the point of view of fundamental research and technology as well. In this paper Si(substrate)/Ta(10 nm)/Cu(25 nm)/W(10 nm) and Si(substrate)/Co(150 nm)/Ta(10 nm) samples, prepared by DC magnetron sputtering, were in investigated. The samples were annealed at several temperatures ranging from 423 K to 823 K for various times. The composition distributions were detected by means of Secondary Neutral Mass Spectrometry (SNMS). Microstructural characterization of samples was carried out by means of Transmission Electron Microscopy (TEM). It is shown that the changes in the composition profiles were mainly caused by grain boundary, GB, diffusion and the effective GB diffusion coefficients of Ta in Cu were determined both by the ‘‘first appearance’’ and ‘‘centre-gradient’’ methods. The activation energy is 100 kJ/mol. The importance of the Ta penetration into the Cu and its accumulation at the Cu/W interface can lead to an increase of the Ta content in the copper film. This can be an important factor in the change/degradation of the physical parameters (e.g. the electrical resistance) of interconnects. Furthermore a Ta segregation factor in Cu was evaluated. Preliminary results in the Si(substrate)/Co(150 nm)/Ta(10 nm) indicate fast (GB) diffusion of the Si into the Co layer, formation of a cobalt silicide layer at the Co/Si interface and Si accumulation first at the Ta/Co interface and later a retarded accumulation at the free Ta surface. 2010 Elsevier Ltd. All rights reserved.

The law of corresponding states for metals

Abstract Using the similarity of the effective potentials seen by ions in metals a reduced phonon equation of state is derived. It is shown that the melting point T m (0) and the atomic volume Ω 0 at T = 0 K and at p = 0 are suitable macroscopic parameters for scaling ϵ and σ characterizing the interatomic potentials of metals having similar structures. The temperature and pressure dependence of thermodynamical quantities reduced with the above parameters are discussed and the results are compared with the experiment. It is shown that the pressure dependence of the reduced thermodynamic quantities can be described by the pressure dependence of the scaling parameters T m ( p ) and Ω 0 ( p ). The general form of the reduced equation of state (containing the electronic contributions as well) obtained gives that the reduced pressure is a universal function of the following reduced variables: the volume, temperature, de Broglie wavelength, Gibbs free energy of electrons 3 5 zE fo ϵ ( E fo is the Fermi energy at T = 0 K) and depe of the valence z as well. It is shown that E fo ϵ is a function of Ω o −1 2 and ( E fo /ϵ )Ω 1 2 is approximately constant within the same sub-group of the periodic table.

Tracer diffusion of 63Ni in Ni3(Al,Ge) ternary intermetallic compound

Abstract Radio-tracer diffusion measurements of 63Ni have been performed in Ni75AlxGe25−x ternary intermetallic compounds at various temperatures. The tracer diffusivity was found to depend exponentially on the Ge content of the alloy. These compounds are ordered with the L12 structure, where the Ni atom diffusion proceeds mainly via Ni sublattice site jumps. The change of the diffusivity can be attributed to the change in vacancy concentration on the Ni sublattice as well as to the composition dependence of the saddle-point energy of the diffusion jumps.

Diffusion of tin implanted in aluminium

Abstract The temperature and pressure dependence of diffusion of Sn113 implanted in high-purity aluminium single crystals has been investigated by means of the serial-sectioning technique. It was found that tin is a fast diffusing solute in A1. The temperature dependence of the process in the temperature range 649–906 K can be described by The activation volume of diffusion was found to be 0·87 ± 0·01 in atomic volume units at 787·5 K.