R. Černý

Structure of TiN coatings deposited at relatively high rates and low temperatures by magnetron sputtering

Abstract Titanium nitride coatings were deposited at an average deposition rate ranging from 0.1 to 0.5 μm min -1 onto steel substrates maintained at 50 or 150 °C. The hardest coatings in each of the three sets investigated contained 36–38 at.%N and are thus significantly substoichiometric. The microstructure of the hardest coatings is characterized by the highest compressive stress, the greatest amount of strain, the minimum preferred orientation and the minimum volume fraction of crystalline phase in each set. A compressive stress was observed in the cubic phase layers and a tensile stress in the hexagonal phase layers. The stress and strain observed in the hardest TiN x coatings were approximately one order of magnitude higher than those of ordinary metals. With increasing nitrogen content the 〈111〉 texture in the cubic phase layers is gradually replaced by the 〈100〉 texture. It was found that the lattice parameters of the TiN x coatings exceed the bulk values.

Ion-assisted sputtering of TiN films

Abstract Ion bombardment of growing films is one of the possible ways to produce films with specific properties. As yet there are no general rules for the production of these films. The quality of TiN films produced depends on the deposition conditions. A sharp transition from porous, black TiN films to compact, dense, bright gold TiN films is observed at a substrate bias U s of about -40 V. Recent experiments have indicated that the microstructure of TiN films and the transition mentioned above can be controlled by the ion energy delivered to the growing film per deposited particle E p = eU s v i / v m . This paper investigates the transition from porous, soft TiN films with a zone I microstructure to compact, hard TiN films with a zone T microstructure as a function of i s , U s and the deposition rate a D at constant temperature T s = 350 °C and pressure p T = 5 Pa. Correlations between the microhardness HV, the macrostress σ, the microstrain e , the lattice parameters, the intensities of the X-ray reflections and the colour and appearance of the film are discussed. The zone I to zone T transition is observed at E p ≈ 150 eV atom -1 .

Dependence of microstructure of TiN coatings on their thickness

Abstract Two sets of TiN coatings containing 34.5 at.% N and 50.3 at.% N, on average, were investigated by X-ray diffraction. No systematic changes in strain and microhardness were observed as the layer thickness was varied from 1 to 12.5 μm, with the exception of the influence of the substrate on the microhardness measurements in layers thinner than about 4 μm. A general tendency of the lattice parameters to decrease with increasing layer thickness was found together with their systematic dependence on the orientation of grains in the coatings. These results and the observed decrease in stress with increasing layer thickness are explained by a gradual improvement in the structure of the layers with increasing thickness and by the heterogeneous nature of the structure. A change in the preferred orientation of crystallites with the layer thickness was also registered.

Complex XRD microstructural studies of hard coatings applied to PVD-deposited TiN films Part I. Problems and methods

Abstract Conventional X-ray powder diffractometry is often insufficient for the study of the specific microstructure of hard coatings. It should be complemented at least by XRD geometries giving other information. Therefore the following geometries are compared: conventional powder diffractometry in Bragg-Brentano geometry, asymmetric diffraction used for stress measurement in the so-called ohm- and ψ- goniometer geometries, and Seemann-Bohlin diffractometry. Advantages and drawbacks of the methods are briefly estimated. A short review of basic methods for the characterization of texture, stress and lattice defects is given. Specific effects frequently observed for hard coatings (e.g. the anisotropy of lattice parameters and XRD line broadening) are discussed, together with some of the possible reasons. Quantitative estimations are given for different types of lattice defects and elastic anisotropy. The crystallite group method is found to be useful for thin films.

X-ray analysis of heat-treated titanium nitride films

Abstract Titanium nitride films deposited onto steel substrates maintained at 423 K were heat treated in the temperature interval 773–1173 K. Samples were studied by electron probe microanalysis and X-ray diffraction. The high values of the microhardness observed for the as-deposited films decreased after annealing for 3 h at 973 K to nearly bulk values. This decrease is mainly due to the improvement in the microstructure of the films. It is accompanied by strong decreases in strain, stress and the lattice parameter of δ-TiN x . Growth of the ϵ-Ti 2 N phase at the expense of the δ-TiN x phase was observed in a film with 34 at .% N when it was annealed for 3 h at 973 K. The lattice parameter and strain in the substrate increased after film deposition, most probably due to a dissolution of nitrogen or titanium atoms in the lattice of α-Fe.

Structural analysis of tin films by Seemann-Bohlin X-ray diffraction

Abstract The accuracy of the Seemann-Bohlin method has been improved by usinginternal standards and a new calibration function. Experimental results illustrated by four typical examples show that the stress and stress-free lattice parameter values determined by this method are crystallographically averaged quantities convenient for an overall characterization of lattice distortions. Combination of the method with the Bragg-Brentano technique and with sample annealing or substrate dissolution can be used for the separation of particular structural effects on the properties of TiN hard films.

ε-Ti2N phase growth control in titanium nitride films

Etude detaillee de la formation de la phase Ti 2 N−e et determination de criteres permettant de prevoir la creation de couches a phase Ti 2 N−e

Complex XRD microstructural studies of hard coatings applied to PVD-deposited TiN films Part II. Transition from porous to compact films and microstructural inhomogeneity of the layers

Abstract Transition from porous to compact microstructure of magnetron deposited TiN films with increasing energy of incoming particles is associated with the changes of stress and strain. This is studied by conventional powder diffractometry in Bragg-Brentano geometry, by asymmetric diffraction used for stress measurement in the so-called Ω-and ψ-goniometer geometries and by the Seemann-Bohlin diffractometry. The changes of lattice parameters and preferred orientation are investigated as well. The results are discussed from several points of view: elasticity theory, lattice defects and heterogeneous microstructure of the films. The heterogeneity seems to be an important reason for specific effects of lattice parameters and X-ray diffraction line broadening anisotropy. The crystallite group method (CGM) is used for the evaluation of stress and crystallite size and reveals the microstructural inhomogeneity. The importance of the orientation of crystallite with respect to the surface for its real structure is further confirmed by the measurement on freestanding film.

Microstructure of titanium nitride thin films controlled by ion bombardment in a magnetron-sputtering device

Abstract The structure of titanium nitride thin films deposited by unbalanced magnetron sputtering on high chromium steel substrates was studied by X-ray diffraction. In order to characterize relations between the microstructure of sputtered TiN films and the deposition conditions, the parameter Ep was introduced as the average energy transmitted from bombarding particles (ions, electrons, neutrals, photons) to one condensing particle of the film. A transition from a porous to a compact microstructure was found with increasing Ep. The possible inhomogeneity of titanium nitride films is discussed.

X-ray diffraction investigations of adherent and free standing TiN coatings deposited by magnetron sputtering

Abstract TiN coatings deposited on steel substrates at different biases and temperatures, and with different nitrogen contents, were studied by conventional X-ray powder diffractometry. The diffraction peaks were separated by profile fitting. In adherent films different kinds of texture and a large anisotropy of lattice parameters ( a(hhh) a ( h00 ) a ( hh0 )) were detected. In corresponding free-standing films lower average values of lattice parameters were found and their anisotropy decreased considerably. The microstrain determined from X-ray line broadening remained unchanged, which proves its inelastic nature owing to the lattice defects.