J. Dudonis

Physical properties of zirconium oxynitride films deposited by reactive magnetron sputtering

The purpose of the present investigation is to analyze structural, optical, and electrical properties of transition zirconium oxynitride thin films deposited by direct current reactive magnetron sputtering. Films were prepared on Si(111) and glass substrates in an argon/nitrogen+oxygen atmosphere. The oxygen flow increased stepwise from 0 to 10 sccm, while at the same time the nitrogen flow decreased from 10 to 0 sccm. Working pressure was kept constant to reach 1.510-2 Pa pressure in the vacuum chamber by adjusting argon gas flow. Depending on the nitrogen-oxygen flow rates, cubic ZrN:O, cubic ZrO2:N, tetragonal ZrO2:N, and monoclinic ZrO2:N phases films were prepared. Optical and electrical properties depend on reactive gas (nitrogen+oxygen) flow. Refractive index vary from 2.13 to 2.38, band gap vary from 2.84 to 4.75. The electrical conductance of ZrNxOy films shows semiconductor-like behaviour.

Changes in surface composition induced by ion bombardment of multicomponent alloys

Abstract The surface composition of Ag x Au y Pd z ( x =0.1−0.6, y =0.3−0.8 and z =0.1−0.5) alloys affected by 2 keV argon ion bombardment were investigated as a function of alloy bulk composition. It was found that the ratio of component sputtering yields of tertiary alloys depends on the bulk composition of the alloy. The characteristics influences needed to achieve the steady state surface concentration are different for different types of atoms in the alloy and experimentally measured values are in the range (7.3−23.3)×10 15 cm -2 .

Mass-Transport in an Austenitic Stainless Steel Under High-Flux, Low-Energy Nitrogen Ion Bombardment at Elevated Temperature

The kinetics of nitriding has been the focus of much research since the introduction of the process [1, 2, 3]. Due to unusually advantageous combination of properties the nitriding of an austenitic AISI 304 stainless steel is widely studied. It is shown that ion nitriding provided by ion beam/plasma techniques at elevated temperature (∼400°C) is a potential candidate to overcome the problem of enhancing surface hardness and wear resistance of an austenitic stainless steel without decreasing their corrosion resistance. Gas and liquid nitriding need temperatures between 500 and 600°C, which are detrimental to the corrosion resistance due to structural transformation of alloys.

Mass-transport driven by atomic relocations under high-flux ion irradiation at elevated temperatures

Experiments with nitrogen torch at atmospheric pressure have been performed in order to identify the role of surface processes in the mechanism of nitrogen transport during nitriding of stainless steel AISI 304. The unusually thick (approximately 175 micrometers ) layers of supersaturated N solid-solution f.c.c. phase have been obtained for 10 min 450 degrees C. Radically different structure have samples treated for 550 degrees C. The scanning electron microscopy (SEM) surface and cross-sectional micrographs reveal that surface topography is indicator of the degree of modification occurring in the nitrided layer. Surface vacancies generated by surface instabilities move deeply into the bulk at elevated temperatures and form highly defected layer with pores and microcracks. The transport of nitrogen in austenitic stainless steel is driven by the fluxes of matrix atoms directed to stabilize surface instabilities. Nitrogen depth profiles simulated on the basis of the model with surface atom relocation process and activation energy 1.1-1.5 eV and including balanced fluxes of atoms in the bulk for relaxation of surface energy are in quantitative agreement with experimental results.