Dariusz Chocyk

Stress development during evaporation of Cu and Ag on Silicon

This work presents results of stress measurements during deposition of thin silver and copper films on 100 µm Si substrate. The stress in thin films has been determined by means of an optical system for the measurement of samples curvature. This system was applied in situ in a high vacuum deposition system. For Ag films the stress occurring during deposition goes from a low compressive value to tensile for thickness less than 30 nm and to compressive above this. For Cu films we observe tensile stress for thickness less 20 nm and above 50 nm. The same general trend of stress evolution with thickness is present in all cases at initial stage. There is the same growth mode for Cu and Ag because of the similar shapes of stress curves for thickness lower than 30 nm The behavior of stress evolution was explained by island nucleation and growth, island coalescence and continuous film growth. The difference in the stress evolution above 30 nm is caused by the fact that silver may be less sensitive than copper to adsorption of impurities. Adsorbed contamination inhibits compressive stress increase generated by grain boundary and defects remaining in the film.

Comparison of the effect of dietary copper nanoparticles with copper (II) salt on bone geometric and structural parameters as well as material characteristics in a rat model

Copper is required for normal functioning of all basic biochemical and physiological processes in the body. The objective of this study was to compare the effect of two different chemical forms (carbonate and nanoparticles) of Cu administered in feed mixtures to growing rats on bone geometric and structural parameters as well as material characteristics in a rat model. For this purpose, five experimental treatments were used to evaluate the effects of different levels of Cu applied in the diet as a mineral mixture (the standard dose of 6.5mg/kg diet, half the standard dose, and no Cu in mineral mixture as a negative control) and two Cu sources (CuCO3 - commonly used in rodent laboratory diets and a Cu-NP nanoparticle preparation, 40nm). There were no changes in body weight and bone morphology, but significant alteration was noted in the geometry and mechanical parameters, which was Cu-NP-dose dependent. Our study showed an increase in the ultimate load and toughness in Cu-NP-treated rats at the standard concentration. The higher values of the studied parameters prove that there was a change in bone mineralization. Although bone mineral density and content were not changed, bone tissue density and ash increased. The XRD analysis revealed that some peaks did not originate from hydroxyapatite, and they indicated existence of other mineral phases. No studies conducted so far have provided a detailed mechanical X-ray diffraction analysis of bone tissue of growing rats administered with diet containing Cu nanoparticles. This study showed that Cu-NP given in low dose increased mechanical endurance of bone, without the changes in strain and stress compared to low dose of Cu given in traditional form.

Stress development during thin film growth and its modification under ion irradiation

The paper presents the results of average stress measurements during deposition of thin copper and silver films and during ion irradiation of molybdenum thin films. Deposition chamber and ion implanter were equipped with the same optical systems for radius of curvature measurement (scanning technique). The average stress in the 92 nm total thick Cu/Ag/Cu/Ag system on 100 μm Si substrate during deposition at room temperature is reported. Deposition process was intermitted after each material. The non-continuous changes of the stress are interpreted as differences in temperature of the sample in different deposition stages. High residual stresses up to 3 GPa were evidenced in the Mo thin films deposited on Si substrate with RF sputtering. During ion implantation with Kr and Ar ions stress relaxation effect of Mo thin films was observed. Kr ion irradiation of the silicon substrate without a film was additionally performed. After the irradiation (total dose 1.4 x 10 15 ions/cm 2 ), the implanted region of the silicon wafer was under compressive stress. A stress maximum was evidenced for a dose of 1 x 10 14 ions/cm 2 .

Influence of water addition on mechanical properties of thermoplastic starch foils

Abstract The aim of this paper is to study the influence of water on the mechanical properties of thermoplastic starch films. Experimental observations of Young modulus and the breaking force of thermoplastic starch foils with different percentages of polyvinyl alcohol and keratin additives and screw rotation speeds are reported. Thermoplastic starch foils are prepared by the extrusion method with the bowling from potato starch and glycerol as a plasticizer. Young modulus and the breaking force were determined by the random marker method. Measurements of Young modulus and the breaking force of the films were performed after their production and after dosing with water. It was observed that in all cases Young modulus decreases after dosing with water, but the breaking force lied in the same range. Thermoplastic starch foils produced at the screw rotation speed equal to 60 r.p.m. have the best mechanical properties. The highest value of Young modulus and the breaking force were obtained for samples with a 1% keratin additive.

Stress evolution during deposition of heteroepitaxial systems

Stress evolution during deposition of heteroepitaxial systems on flat and line-patterned substrates was studied by three-dimensional (3D) molecular dynamics simulation. The simulation of deposition process was carried out in a system consisting of the (001) substrate of a face-centred cubic crystal and pre-deposited atoms forming flat layers or patterned lines. Interactions between the atoms were described by the Lennard-Jones potentials. Kinematic theory of scattering was used to analyse the structures obtained from simulations. Stress evolution during the growth of thin films at different temperatures of the systems was also studied. It was found that in-plane stress is an anisotropic in heteroepitaxial systems. In the case of flat pre-deposited layers, the distribution of stress does not depend on temperature and the distribution of stress is determined by orientation of linear structures in patterned systems.

The Characteristic of the Multilayer Thin Films by X-Ray Reflectometry Method

The X-ray reflectometry (XR), as a non-destructive method, is a powerful tool in obtaining information about parameters of thin films such as thickness, average density and interface roughness. In this paper Cu/Au, Au/Cu and Cu/Ag multilayer thin films (where the total thickness is less then 1000Å) are presented. The multilayer films are obtained by thermal evaporation in a UHV system, on the silicon substrate. The experimental XR curves contained critical angle and classical Kiessig’s fringes. For these materials the density (), the thickness () and interface roughness () information for every layer separately were calculated. The experimental reflectometry curves were analyzed using the WinGixa programme X’Pert software. The values of layer density show that they are reached in neighbor density and it is connected with the creation of the Cu-Au or Ag-Cu interlayer reached into Cu, Au or Ag, respectively. The analysis of roughness show that there are comparable to roughness of substrate only for 2-3 first layers. Further the roughness of Cu, Au, Ag layers are increasing. The comparison of results show that increasing of Ag an Au roughness is bigger than Cu.

Stresses in Multilayer Systems: Test of the sin2Ψ Method

The sin 2 Ψ method based on the asymmetric X-ray diffraction is widely used to determine stresses in thin films. However, application of this method to multilayered thin films is not straightforward. In this work the authors present experimental asymmetric X-ray diffraction maps obtained for Cu/Ni and Au/Ni multilayered systems. They also describe the model based on a Monte Carlo simulation for calculating the X-ray diffraction profiles from multilayers.

Synthesis and characterization of AgFeO2 delafossite with non-stoichiometric silver concentration

Abstract The simple co-precipitation method was used to prepare AgxFeO2 delafossite with non-stoichiometric silver concentration in the range of x = 0.05-1. The obtained material was investigated using X-ray powder diffraction and 57Fe Mössbauer spectroscopy at room temperature. The structural and hyperfi ne interaction parameters were recognized in relation with decreasing silver concentration. The study revealed that the delafossite structure of AgxFeO2 was maintained up to x = 0.9; as the range of silver concentration was decreased to 0.05 ≤ x ≤ 0.8, a mixture of AgFeO2, Fe2O3 or/and FeOOH was formed.

Study of Structure and Strain in Au/Cu Systems Using Molecular Dynamics Simulation: X-Ray Scattering Analysis

The aim of this work is to investigate structure and stress evolution in Au/Cu bilayer systems during deposition. The approach used here is based on an embedded atom method (EAM). interatomic potential database for different metal elements, their alloys and multilayers. We applied the kinematical scattering theory to calculate the X-ray scattering profiles. In this case the X-ray scattering techniques are used for the structural characterization of crystal structures obtained from simulation data. This method was applied to determine the lattice parameters in any directions. The lattice parameters in deposited layers were directly determined by the analysis of X-ray diffraction profiles. Results shows that on the interface of Au/Cu system, the crystalline lattice of Au layer is fitted to crystalline lattice of Cu layer. We found that deformation of the crystal lattice near the interface has a major influence on the stress.

Molecular Dynamics Study of Adatom Size Effect on Stress Evolution in Lennard-Jones Thin Films: X-Ray Scattering Analysis

Molecular dynamic simulations are used to study the structure and the evolution of stress during the deposition of atoms with different size on the (001) FCC plane. The relative size of deposited atoms is changed in the range from 0.75 to 1.0. To calculate the X-ray scattering profiles we applied the model that is based on the kinematical scattering theory. Deformation of the lattice parameters in deposited layers were directly determined by the analysis of X-ray diffraction profiles. It was found that the crystal lattice near the surface exhibits a major influence on the stress evolution. The deposited atoms form the same structure in entire systems, regardless of the their relative size.