Although mechanical studies of multilayer thin films are increasingly more abundant, the majority of studies merely determine film hardness using micro- or nanoindentation techniques. Actual tensile tests are still quite rare. We have therefore conducted tensile tests of free standing aluminum-titanium multilayer thin films. This system was selected for its potential use as a low density (3.3 g/cm3) structural material with potential aerospace applications. The strongest multilayers produced, with bilayer thicknesses 7nm Ti/16 nm Al, fractured at tensile stresses (UTS) of 900 MPa - well beyond the UTS of either of the constituent materials. Specimen characterization by xray diffraction as well as transmission electron microscopy (TEM) revealed near perfect texturing and an intriguing hcp to fec transformation of the titanium layers during preparation of samples for TEM viewing.

We employed nanoindentation, continuous microscratch testing, and high resolution TEM to determine the effect of structure on the properties and resistance to fracture of thin polycrystalline aluminum films deposited onto single crystal sapphire substrates at 25°C and 250°C. These films had a nominal thickness of 90 nm and a grain size of 160 nm. The elastic and plastic properties were similar for both films. The elastic moduli superimposed, increasing from bulk aluminum values at the surface to sapphire values at the interface. Hardness values also superimposed, but were constant through the film thickness at a value between aluminum and sapphire. In contrast, susceptibility to fracture varied markedly between the films with the 25°C film exhibiting abrupt failure along the film-substrate interface while the 250'C film gave no indication of fracture in the film, along the interface, or in the substrate under the conditions tested.

Microindentation experiments were carried out on 500 nm thick films of copper grown on sapphire substrates, containing titanium interlayers of different thicknesses. The films were near single crystal and were grown by molecular beam epitaxy. The width of the titanium interlayers was varied from 0.7nm to I 10nm. The load-displacement data obtained from the indentation experiments was analyzed in terms of a new model. Just 0.7nm of titanium produced a 40% increase in the interfacial shear strength. Further increase in the thickness of the titanium interlayers produced only a slightly larger increase in the interfacial strength, suggesting that the measurement reflected the influence of the atomic bonding at the interface. The technique and the model present a simple way to estimate the relative change in the interfacial strength of metal-ceramic interfaces.

The hardness dependence on grain size of a nanocrystalline iron thin film prepared by sputtering was investigated. The as-deposited film had an initial grain size of 11.4 nm and sections of the film were annealed in a reducing atmosphere furnace to increase the grain size up to 31.5 nm. Hardness was measured by nanoindentation for different grain sizes, and a Hall-Petch plot of hardness versus reciprocal square root of grain size was obtained. This Hall-Petch plot gave a positive slope that was about a factor of seven smaller than the slope obtained from ball-milled iron with grain sizes between 6.0 and 8.5 nm [8].

The electrodeposition of cobalt-copper multilayers will be described and the dependence of their magnetoresistivity on layer thickness and deposition parameters will be presented. For a wide variety of layer thicknesses electrochemically produced Co(Cu)-Cu thin polycrystalline layered alloys exhibit a giant magnetoresistivity (GMR). Further, upon annealing, the materials undergo a combination of grain growth and grain boundary diffusion. At certain conditions, this phenomena is believed to lead to a break up of the layered structure so that a magnetostatic coupling occurs and contributes to the GMR behavior. It is further shown that, by careful control of the deposition parameters, a quasilinear GMR response (low sensitivity) can be created over a large magnetic field or, conversely, a high sensitivity material can be grown, although at the sacrifice of introducing hysteresis in the response curve. The major deposition parameter affecting this behavior is mass transport in the electrolyte; however, substrate grain size, layer spacing and annealling history also play an important role.

Although methods of measuring the elastic properties of thin films have made great advances with the use of bulge testing of membranes, deflection of micromachined beams, and nanoindentation, most results are still being compared to either isotropic or single crystal elastic constants, neither of which are, in general, appropriate for textured polycrystalline films. This paper uses recent results of a self-consistent model (after Krbner and Kneer) which calculates the elastic anisotropy arising from crystallographic texture and which has been extended to predict the anisotropy resulting from grain shape. These results are compared to the various Voigt, Reuss, and Hill approximations that are appropriate for different crystallographic textures. The accuracies of the different models are evaluated in terms of their ability to predict the biaxial modulus and indentation compliance that are most commonly measured in thin films.

X-ray diffraction provides an easy and powerful method for measuring residual stress in thin films. However, nonlinearity of the d vs. sin2ψ relation can lead to the misinterpretation of results, especially when one of the measurements is made at low values of ψ relation for different combinations of ideal crystallographic textures and grain shapes are given. In all cases, a high ψ angle range exists where the d vs. sin2ψ relation in the low ψ angle range.

We investigate the variation of microstructure and electron transport with layer thickness in Mo/Si multilayer films deposited by magnetron sputtering.

BaTiO3 thin films, 50–60 nm in thickness, were evaporated in Ultra High Vacuum as well as under 1 mPa O2 pressure onto Si/SiO2 (30 nm) wafers. The substrate temperature during the evaporations was approximately 70 °C. The films were flash annealed in oxygen at 500 °C. The interfacial reactions were studied by XPS and AES Ar ion assisted depth profiling, and by RBS. Interdiffusion took place even at 70 °C. The XPS/AES depth profiles suggested strong interdiffusion, with Ba being the dominant moving species. The SiO2/BaTiO3 interface smears out with significant Ba concentrations up to half of the SiO2 thickness. Ti diffusion is remarkably lower. Barium is detected up to the SiO2/Si interface.

Aluminum thin films deposited onto silicon substrates coated with silicon dioxide or a layered structure of titanium and titanium nitride have been investigated using the combined techniques of electron backscatter diffraction and orientation imaging microscopy. By these methods the local texture and spatial distribution of texture components was established. It was observed that whereas the material exhibited an overall <111> texture with the in-plane direction <110> uniformly distributed, there were variations in the local texture and distribution of orientations with clustering of grains of similar orientation. Individual grains within the clusters were nearly perfect and varied in orientation by only a few degrees. The effective grain size differed greatly on whether the cluster size of similarly oriented grains or the diameter of individual grains within the cluster was considered to constitute the grain structure. No strong bias was found in favor of coincident site oriented grain pairs though in some cases the frequency of occurrence of low angle boundaries was less than is expected on a purely random basis. Additional experiments were carried out in order to establish the suitability of orientation imaging microscopy for microstructure characterization of interconnect lines in integrated semiconductor device technology.

The concept of fcc fiber texture is examined in the context of Rodrigues-Frank (R-F) representations. Using fiber texture in thin films as the basis of our analysis, it is shown that this approach when combined with grain specific determination of crystallographic orientation provides a useful means of detecting a number of texture components with relatively small grain sampling densities. The application of R-F representations is also shown to be a useful methodology to couple grain boundary structure information with microtexture data.

We describe spatially resolved grain orientation mapping of polycrystalline films using a synchrotron-based x-ray microdiffraction system. The system consists of a tapered glass capillary as a white x-ray concentrator, an energy-dispersive solid state detector and an x-y-z sample stage. Two mapping modes are discussed: reciprocal-space mapping and real-space mapping. Information about the orientations of grains within the irradiated volume is determined by reciprocal-space mapping. The locations of grains having a specified orientation are determined by real-space mapping. Examples are shown for blanket films of AI(4 wt.% Cu) 4μm-thick and 0.5μm thick. Results are also shown for 10μm-wide and μm-wide pure lines. X-ray beams of 10inm diameter were used for these measurements. Spatially resolved thermal strain measurements were made for a single 10μm-wide, 200μm-long passivated Al line, and they were found to be consistent with calculations based on equi-biaxial thermal stress within the line.

A proposed hard x-ray (>10 keV) telescope design uses multilayers on gold coated replica substrates. We investigated the grazing incidence x-ray reflectivity (0.154 nm) of super polished fused silica, gold coated fused silica, and mutilayers deposited on each. Gold coatings of 100 nm were deposited by both magnetron sputtering and ion beam sputtering. Carbon/nickel multilayers (20 layer pair with 4.0 nm d-spacing) were deposited by ion beam sputtering. We report the results of specular and diffuse reflectivity characterizations of these samples. The easured x-ray reflectivities are compared to model calculations evaluating film thickness, ensity, optical properties, and interface roughness/diffusion. It is concluded that substrate and film quality (roughness and density) can be determined by grazing incidence reflectivity measurements and correlated to final multilayer reflectivity and model calculations.

Multilayer carbon nitride/TiN coatings were synthesized using a dual-cathode dc magnetron sputtering system. Fully crystalline films can be obtained when the thickness of the carbon nitride component is on the order of one nm. There appears to be a strong correlation between the occurrence of strong TiN(111) texture and the hardness of these multilayer coatings, as controlled by target powers, nitrogen partial pressure and substrate bias. These coatings can be synthesized at near room temperatures, with smooth surface morphology and hardness in the range of 45–55 GPa.

The growth of polycrystalline and amorphous aluminum-oxygen alloy films using electronbeam evaporation of Al in the presence of an O2 electron-cyclotron-resonance (ECR) plasma was investigated for film compositions varying from 40% Al (A12O3) to near 100% Al (A1Ox). Processing parameters such as deposition temperature and ion energy were varied to study their effects on surface texture and film microstructure. The Al-rich films (AlOx) contain polycrystalline fcc Al grains with finely dispersed second-phase particles of γ-A12O3 (1–2 nm in size). The surface roughness of these films was measured by atomic force microscopy and found to increase with sample bias and deposition temperature. Stoichiometric A12O3 films grown at 100°C and 400°C without an applied bias were amorphous, while an applied bias of -140 V formed a nanocrystalline γ-A12O3 film at 400°C. The surface roughness of the A12O3 increased with temperature while ion irradiation produced a smoother surface

It has been experimentally and theoretically found that the critical applied stress intensity factor for indentation cracking also depends linearly on the reciprocal of the square root of crack length when the indentation fracture technique is used to measure residual stresses in thin films.

Different PVD coatings are used to reduce the wear of tools and other machine parts, and to improve their service life [1]. During the last years, a number of developments have been made in the field of carbon coatings. These coatings show a low friction coefficient, e.g. against steel, and therefore have a high potential in decreasing the friction and wear of coatings in tribological applications. This PVD process can be stabilised by using a metallic target which is vaporised in a carbon and hydrogen atmosphere. The carbon rich side of the metal/carbon system is object of this study.Slightly superstoichiometric coatings in the range of 50–60% carbon content have very good friction properties too and with the potential to better film properties (coating adhesion due to internal stress, microhardness). In this paper the mechanical properties of coatings in the systems Ti-C, Si-C and Ta-C are described and the different microstructures are discussed.

The phase transformations in a plasma sprayed zirconia-titania-yttria thermal barrier coating (TBC), subjected to different thermal treatments, in the temperature range 900–1400°C, were characterized by X-ray diffraction (XRD). Different transformation trends dependent on the cooling rate of the specimens from the treatment temperature, were observed. The study of the fracture surfaces of the as-sprayed and thermally treated ceramic coatings, using scanning electron microscopy (SEM), allows elucidation of the changes in the microstructure and the fracture mechanisms. The as-sprayed and thermally treated (1400°C) ceramic microstructures were also studied using transmission electron microscopy (TEM).

Determining the intrinsic mechanical properties of films by nanoindentation is complicated by the presence of the substrate. Generally, for very thin films (<100 nm) one unavoidably observes the properties of the film/substrate composite system. In order to determine the extent of the effect of the substrate on the mechanical properties of Ta and Ta-N thin films, we have grown these films in four different thicknesses (50, 250, 400 and 500 nm) and on three different substrates (glass, oxidized Si, and sapphire). The structure of the films was evaluated by x-ray diffraction and the mechanical properties (hardness and elastic modulus) were determined by nanoindentation.

TiB2, MoSi2, Si3N4 and Ta4N ceramic films were magnetron sputtered on oxidized Si and Coming 7059 glass substrates at ambient temperature. X-ray diffraction studies indicate that the structure of the films is very different on the two substrates, even though the surface of both substrates is amorphous. The hardness and elastic modulii of the films on oxidized Si are slightly higher than those of the films deposited on Coming glass substrate, even at indentation depths where substrate effects are considered to be negligible. A substantial increase in hardness (5–10 GPa) was observed for TiB2 films, when compared to the properties of bulk stoichiometric TiB2. Stress- temperature diagrams determined from room temperature to 250 C indicate that all the films prepared in this study display a pure elastic behavior in that temperature range.