Search

Graphical abstract Highlights • A formula for intrinsic stress in coating deposited from mixed ion beam is proposed. • Formula accounts for deposition temperature, it is valid in DC and pulse potential mode. • Stress calculation in Ti 1−x Al x N coating in DC and pulse potential mode is carried out. • Increase content of Al reduces stress in Ti 1−x Al x N coating deposited in pulse mode. Abstract The model of the nonlocal thermoelastic peak of low-energy ion is used in deriving an expression for intrinsic stress in multi-component material deposited from mixed beam of differently charged ions in modes of the direct current (DC) and pulsed bias potential. Calculation of intrinsic stress depending on bias potential in coating Ti 1−x Al x N deposited from mixed ion beam Ti + Al with different component ratio is executed in modes of DC and pulsed bias potential at different substrate temperatures. It is shown that the increase of the content x of Al ions in the mixed beam and in deposited Ti 1−x Al x N coating reduces the maximum of the stress curve σ(U). [ABSTRACT FROM AUTHOR]

The influence of the ratio between the energy and the deposition flux, or the energy per arriving atom, on the growth of Y 2 O 3 sputter deposited thin films has been studied. The energy per arriving atom has been varied by the adjustment of the discharge power, and/or the target-to-substrate distance. The relationship between the energy per arriving atom and the phase evolution, grain size, microstructure, packing density and residual stress was investigated in detail. At low energy per arriving atom, the films consist of the monoclinic B phase with a preferential (1 1 1) orientation. A minority cubic C phase appears at higher energy per arriving atom. A study of the thin film cross sections showed for all films straight columns throughout the thickness, typically for a zone II microstructure. The intrinsic stress is compressive, and increases with increasing energy per atom. The same trend is observed for the film density. Simulations show that the momentum transfer per arriving atom also scales with the energy per arriving atom. Hence, the interpretation of the observed trends as a function of the energy per arriving atom must be treated with care. [ABSTRACT FROM AUTHOR]

Abstract: We present our recent experimental results on the formation of off-axis texture and crystallographic tilting of crystallites that take place in thin film of transition metal nitrides. For this purpose, the microstructural development of TiAlN film was studied, specially the change in texture with film thickness. Fiber texture was measured using θ–2θ and pole figure X-ray diffraction (XRD), while scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the microstructure and changes in texture with thickness. The sin2 ψ method was applied to determine the stresses on (111) and (002) plane. With deposition parameters chosen, the growth texture mechanism is discussed in three different stages of film growth. Surface energy minimization at low thickness leads to the development of (002) orientation. On the other hand, the competitive growth promotes the growth of (111) planes parallel to film surface at higher thickness. However, contrary to the prediction of growth models, the (002) grains are not completely overlapped by (111) grains at higher thickness. Rather the (002) grains still constitute the surface, but are tilted away from the substrate normal showing substantial in-plane alignment to allow the (111) planes remain parallel to film surface. Intrinsic stress along (111) and (002) shows a strong dependence with preferred orientation. The stress level in (002) grains which was compressive at low thickness changes to tensile at higher thickness. This change in the nature of stress allows the (002) planes to tilt away in order to promote the growth of 〈111〉 parallel to film normal and to minimize the overall energy of system due to high compressive stress stored in the (111) grains. The change in surface morphology with thickness was observed using SEM. An increase in surface roughness with film thickness was observed which indicates the development of (111) texture parallel to film surface. TEM observations support the XRD results regarding texture change. Film hardness was measured by nanoindentation and a correlation between (111) texture, stress and hardness is obtained. The results indicate that texture development is a complex interplay between thermodynamic and kinetic forces. An attempt is made to understand this phenomenon of off-axis accommodation of (002) at higher thicknesses, which is a new result not reported previously. [Copyright &y& Elsevier]

Abstract: Nanoscale magnesium oxide thin films have been deposited on glass substrate by thermal oxidation (in air) of vacuum evaporated magnesium films. X-ray diffraction (XRD) showed orientation along (200) and (220) directions. The mechanical properties of the MgO thin films were found to be the function of thickness (300, 450 and 600nm), oxidation temperature (573, 623 and 673K) and oxidation duration (90 and 180min). As oxidation temperature and oxidation duration increases, adhesion and intrinsic stress were found to increase. Intrinsic stress decreased whereas adhesion increased due to increase in thin film thickness. The value of intrinsic stress was in range 28.902–73.212 (×107 N/m2) and that of adhesion was 12.1–27.4 (×104 N/m2) for the thin film of thickness 300nm. [Copyright &y& Elsevier]

The growth of Ge and SiGe alloy films on Si substrates has attracted considerable interest in the last years because of their importance for optoelectronic devices as well as Si-based high speed transistors. Here we give a short overview on our recent real time stress measurements of Ge and SiGe alloy films on Si(0 0 1) performed with a sensitive cantilever beam technique and accompanied by structural investigations with atomic force microscopy. Characteristic features in the stress curves provide detailed insight into the development and relief of the misfit strain. For the Stranski–Krastanow system Ge/Si(0 0 1) as well as for SiGe films with Si contents below 20%, the strain relaxation proceeds mainly into two steps: (i) by the formation of 3D islands on top of the Ge wetting layer; (ii) via misfit dislocations in larger 3D islands and upon their percolation. [Copyright &y& Elsevier]