The analytical solution for a “rigid” axisymmetric indenter penetrating an elastic half-space has been investigated as it pertains to the techniques used in the analysis of experimental nanoindentation data. It is observed that the analytical Sneddon solution and finite element simulations, with the same boundary conditions, deviate significantly from the physical interpretation of a rigid conical indenter. The severity of the deviations depends on both the half-included angle of the indenter and the Poisson ratio of the material being indented. The solution is found to underestimate the actual contact radii by up to 9% and 27% for rigid conical indenters with half-included angles of 70.32° and 42.28°, respectively. Approximate analytical corrections to the Sneddon relationships are presented for the case of a right circular cone of arbitrary included angle. Finite element simulations of a rigid indenter corroborate the deviations of the Sneddon solution, and provide support for the modified solutions.

The microstructure and mechanical properties of sputtered Cu/Ta multilayers were studied. X-ray diffraction and transmission electron microscopy characterization indicate that both the Ta and Cu in the 2 nm period multilayer are predominantly amorphous, while in longer period samples, the layers are crystalline, with the metastable tetragonal β-Ta observed. No observable microstructure changes upon annealing at 300°C were found. An average Vickers micro-hardness value of about 5.5 GPa was measured, which increases about 5% upon annealing at 300° C. Residual stress in the multilayers and its dependence on thermal annealing are reported. The relationships between microstructure and mechanical properties in the multilayers are discussed.

Nanoindentation was performed on layered structure materials to determine values for stiffness and hardness perpendicular to the layers. In order to establish the validity of this technique for anisotropic materials, layered minerals with known elastic constants were tested, including brucite and muscovite mica. A layered ceramic oxide of interest, KCa2Nb3O10, was also investigated. A Berkovich diamond tip was used to carry out the indentations. Indents were made on atomically flat surfaces of crystals, as observed in-situ with an atomic force microscope. Analysis of load versus displacement data showed that the elastic constant C33 for muscovite and brucite agreed to within five percent of literature values. In the case of KCa2Nb3O10, average values of 57.0 GPa for C33 and 3.8 GPa hardness were obtained.

In this study, we employed nanoindentation testing to determine load rate and load rate change effects on the plastic response of a single crystal aluminum sample and of an 80 nm thick vapor deposited aluminum film on a sapphire substrate. The load rate tests showed that the thin film plastic properties exhibited a much stronger dependence on loading rate than the properties of the aluminum single crystal. In contrast, the load rate change data indicated a weak dependence of thin film plastic properties on loading. Scanning probe microscopy showed that the difference in behavior can be attributed primarily to pileup effects on contact area which increased with contact depth and loading rate. When contact area was corrected for increased pileup height, plastic properties were reduced to single crystal aluminum values.

Micro-mechanical techniques were used to introduce tailored deformations to a pre-written magnetic disk. Atomic force microscopy (AFM) and magnetic force microscopy (MFM) were then used to map out the topography of the indentations and their effects on the underlying magnetic layers. The tailored deformation included pyramidal and conical indents, scratches and micro-wear tracks. The extent of topographic damage assessed by AFM was correlated with the carefully monittored normal and tangential forces of the microindenter. Sub-surface ‘damage’ was assessed by MFM, monitoring for loss of resolution in pre-written magnetic data tracks in the underlying magnetic layer. From the combination of micro-mechanical and MFM techniques, we have found that magnetic bit contrast degradation can be mechanically introduced by either physical damage or by shape modification of the magnetic coating. The indentation and scratch tests both confirm that static pressure alone is not sufficient to cause the magnetic bit degradation; however, wear is capable of introducing bit damage at much lower contact pressures. Surface corrugation generated by the wear process alters the geometry of the magnetic coating, thereby causing magnetic bit pattern degradation. Good correlation was found between the degree of disk surface damage and the degree of magnetic bit contrast degradation.

Nanoindentation experiments have been performed to characterize the mechanical properties of very thin amorphous carbon films. Amorphous carbon films on the order of 10 nm or less are required on magnetic thin-film discs to maintain the mechanical integrity of the substrate. In this study, three films in the 10 nm to 80 nm thickness range were studied. The films were sputtered onto an electroless nickel substrate. The primary objective was to use nanoindentation to reliably characterize the elastic modulus and hardness of these very thin films. By making very shallow indents and by using appropriate film-substrate deconvolution techniques, film moduli and hardness in the 75–85 GPa range and 10–11 GPa range were measured, respectively. Finally, shear stresses for nucleation of yielding in the substrate as well as the improved elastic recovery afforded by the amorphous carbon overcoats are discussed.

The nanoindentation technique was used to determine the hardness and Young's modulus of thin C60 films irradiated with N ions. The pristine film, with thickness of 170 nm, was grown on a Si (111) substrate, with an intermediary layer of SiO2 50nm thick. An X-ray analysis reveals a fcc structure for the pristine C60 films. The N irradiation was performed with energy of 170 keV (Rp of 380nm) and fluences ranging from 5×1011 to 5×1015 ions.cm−2 . The loads used in the nanoindentation tests were from 0.05 to 16 mN in order to obtain information about the film, the interface and the substrate. The hardness and Young's modulus, for the pristine and irradiated films were compared considering normalised values at tip penetrations of 70 nm. For the C60 non-irradiated film, the hardness and the Young's modulus were 0.31 GPa and 23 GPa respectively. After N irradiation at fluences greater than 1013 ions.cm −2, the hardness and Young's modulus changed drastically, rising to 15 GPa and 170 GPa respectively at fluence of 5×1015. These results are discussed in terms of the energy transference mechanisms by the N ions into the C60 film.

Transition metal carbides of the VI Group of the Periodic Table (M-C where M = Cr, Mo, W) doped with iron were deposited as thin films on glass substrates by magnetron sputtering and were structurally and mechanically analysed by X-ray diffraction, laser interferometry and ultramicrohardness. The results show that the structures of the M-C binary systems depends on the position of the element M in the Periodic Table. Both W-C and Mo-C systems are crystalline (fcc structure) while the Cr-C is amorphous. The hardness and Young's modulus of the films increase from the carbides of the 1st to the 3rd long period. The addition of iron decreases the degree of structural order of the films as well as their Young's modulus. The films with higher hardness are those with a transition structure between crystalline and amorphous.

Increasing demands on production processes in terms of performance, reliability and environmental compatibility shape the specification profile for modem wear resistant coating systems. The behavior of PVD coated cutting tools are determined by a large number of characteristics and mechanical properties like hardness, residual stresses, coefficient of friction, density, surface roughness etc. For application of coated tools the knowledge of film hardness and residual stresses are also of a great interest.

For the present work, three different substrate materials, high speed steel, cemented carbides and cermets, were coated with TiN or Ti(C, N). The deposition processes were carried out with the Cathodic Arc Ion Plating process (AIP). During the coating processes, the layer thicknesses were varied. The film hardness and the intrinsic stresses are consequences of deposition conditions, e.g.ion bombardment, external heating during deposition and residual layer thickness after coating. This paper reveals first results of film hardness and intrinsic stresses and shows correlations of these effects with the layer thickness. A NanoindenterTM XP was used to evaluate the film hardnesses. The residual stresses were determined using the stripe bending test.

Measuring material properties of sub-micron layers is an important yet a difficult task due to unavailability of proper instrumentation. Techniques such as Dynamic mechanical analysis has been used heavily in the last few years to measure modulus and glass transition temperature. But sample arrangement in this technique makes it impossible to use when thicknesses are smaller than 100 μm.After carefull study of number of different techniques availbale in different laboratories nanoindentation was selected as one of the most suitable, hence this technique can measure mechanical properties without removing the film from the substrate and also at various points of the film. This paper discusses the modulus measurement of thin poymeric films. A possible application of this technique as an adhesion tester will also be highlighted.

In this work, the effect of composition and crystal orientation relationship on theinterface fracture toughness of niobium/sapphire system was studied. Interfaces were synthesized by either physical vapor deposition or ion beam assisted deposition. Silver was deposited to weaken the interface and crystal orientation was used to strengthen it. Several techniques were used to assess the interface fracture toughness, including microscratch, nanoindentation, microwedge scratch, and delamination of patterned lines. Results showed a general trend in which the interface fracture toughness decreased with the amount of silver. Ion bombardment during film deposition significantly increased the interface fracture toughness through a combination of interface mixing and a controlled orientation relationship.

Nanoindentation testing was used to obtain mechanical properties on realistic Sn-Ag solder joints made with (i) eutectic Sn-3.5Ag solder and (ii) in-situ Cu6Sn5 particle reinforced, eutectic Sn-Ag matrix composite solder. The composite solder joint contained ˜20 volume percent of intentionally-added Cu6Sn5 intermnetallic particles which were ∼5 microns in size. The Cu6Sn5 particles were dispersed in-situ in eutectic Sn-3.5Ag matrix alloy as a reinforcement phase to stabilize the microstructure by acting as a non-coarsening microconstituent phase. Mechanical properties characterization and deformation behavior were assessed on the bulk microstructure and on microconstituents in the actual solder joints. Mechanical property data obtained on constituents included hardness, elastic modulus, strain rate, and creep behavior. The pushing and rotation of the reinforcement particles that often occurred when contacted by the indenter provided a means for evaluating the interfacial shear strength of reinforcement particles in the solder matrix.

The adhesion of aluminum (Al) films onto sapphire substrates in the presence of controlled contaminants is being investigated. In this study, adhesion strength is evaluated by continuous nanoindentation tests to induce delamination of the Al film from the sapphire substrate. Typically it is difficult to increase the elastic strain energy stored in the film to levels sufficient to promote indentation delaminated blistering in thin ductile films on hard substrates. One method that appears promising is the use of highly stressed overlayers deposited over the Al. An overlayer of sputtered tantalum (Ta) was deposited on 500 rn thick Al films with and without 10 nm of sputtered carbon on the sapphire surface. With Ta overlayers, continuous nanoindentation techniques induced larger diameter delamination blisters in the specimens with carbon, than in the specimens without carbon, indicating a lower resistance to fracture or interfacial strength.

The microscratch behavior of poly(methyl methacrylate) (PMMA) coatings on flexible substrates of cellulose acetate (CA) and poly(ethylene terephthalate) (PET) was evaluated using the NanoTest 550 microscratch device with a 3-micron radius, 60-degree conical-angle diamond stylus in ramped load from 0.3 to 10 mN. Tensile surface cracking was observed within 6–8 mN for all coatings regardless of coating thickness (from 0.2 to 3 microns). For the same coating thickness, PMMA on PET cracked at lower loads than PMMA on CA because of PET substrate deformation. Coating removal of PMMA was also found, but at higher loads following the tensile cracking. Onset of severe coating damage/removal in PMMA coatings was found to be dependent on coating thickness. The ranking of various PMMA coatings in terms of their extent of microscratching damage was comparable to their rankings based on Taber abrasion results. This suggested that only the severe coating damage on PMMA could be detected by the Taber abrasion test.

The issue of multiple cracks in materials and their interaction is central in understanding the overall fracture behaviour of materials. In the case of materials used in the microelectronics industry, indentation cracking has been extensively used for the measurement of fracture toughness due to its small sample size requirements as well as a relatively good correlation with values obtained from traditional fracture mechanics tests. The majority of these studies have focused on the fracture behaviour of a single indent. The present study was aimed at understanding the effect of interaction between the cracks generated on Si from a pair of sequential indents as well as a set of four sequential indents placed at the comers of a square. The distance between the indents was varied from a level comparable to the crack size to a level where interaction could be ignored. This paper discusses the changes in the nature as well as the sizes of cracks due to interaction between the stress fields of the indents.

Nanoindentation of thin films is an especially attractive technique for the quantitative assessment of the adhesion energy of thin films, in that the film can be measured in the asprocessed condition with almost no sample preparation. Linear elastic fracture mechanics calibrations have been previously developed to quantify the strain energy release rate as a function of film properties, film residual stress and indentation volume. However, this test is limited by the practical difficulty of producing a suitable delamination for either strong interfaces or ductile films. Modified mechanics suitable for a multilayer film have recently been developed. One particularly useful application of this calibration is discussed, namely the use of a highly stressed refractory superlayer that acts to promote delamination of the underlying film (assuming said interface is the weaker). Delamination is ensured by triggering the fracture process through nanoindentation. Such superlayers can be deposited over the as-processed film of interest, producing no significant changes in that film's microstructure or interfacial character. Experimental results using this method are reviewed with particular attention to experimental consideration, along with recent results using copper and tungsten thin films on SiO2.

Scratch testing was performed on the poly(n-butyl acrylate) (PnBA) films using a spherical indenter. For the uncrosslinked PnBA film, the horizontal force during scratching increases with the normal load and has a residual value (˜ 0.6 g) as the normal load approaches zero. The relation can be fitted by using the JKR theory. With increasing driving speed, the coefficient of friction increases but the rate of increase becomes less. For the crosslinked PnBA film which behaves like an elastomer, the horizontal force approaches zero at zero normal load. Below a critical normal load, which depends on the failure mechanism and the thickness of the film, the crosslinked film recovers elastically after being scratched. Above the critical load, the film is damaged and, depending on the film thickness, shows two distinct damage mechanisms.

Metallic coatings on glass substrates are widely used in various microelectronic components. However, sometimes high residual stress generated in the deposition process or after leads to the loss of adhesion between the coating and the substrate, posing a threat to the reliability of the whole device. In this paper we showed results of our study of Cr and Cu metallizations on glass, which are of technological interest as conductors in the flat panel displays. Stress measurement and nanoindentation techniques are used to find out the stress state and probe the interfacial adhesion properties of the thin metallizations. Ways to increase the practical adhesion of the metallization to ceramic substrates will be discussed.

Using large-scale molecular-dynamics simulations in two dimensions, we have observed interesting dislocation generation and dynamics at the interface between two smooth metallic surfaces. sliding relative to one another. The early-time behavior is related to later-time nanocrystalline structure at the interface whose formation is related to velocity-weakening in the coefficient of friction. We discuss the differences between frictional dislocation behavior in two and three dimensions.

Previous experimental and theoretical work in plowing phenomena have primarily focused on the effects of many asperities and hence wear phenomena due to a single asperity have not been adequately investigated. In response to this apparaent lack of information around single asperity plowing effects, two of the authors [1] developed an experimental technique wherein the plowing motion of a pyramidal diamond indentor affixed to a stainless steel cantilever is controlled by the piezoelectric transducers of an atomic force microscope and appropriate software macros. Using the mathematical model of Azarkhin and Richmond [2], they were able to estimate the friction stress developed between the substrate and the indentor as well as the material flow stress for selected aluminum alloys. In particular, the measured ridge heights gave an estimate of friction factor for a particular plow track, and the measured normal and plowing forces lead to an estimate of flow strength. The plow track morphologies were found to depend upon material hardness and specific alloying agents in the material, with the softer materials exhibiting oscillatory ridges due to the development of a built-up edge of the indentor, and the harder materials exhibiting detached ridges due to their reduced fracture toughness [3].

The purpose of the present article is to present an overview of recent developments in single asperity plowing of selected metal surfaces in an atomic force microscope. We shall discuss results from dry plowing experiments as well as plowing experiments in the presence of selected boundary additives. Corresponding theoretical modeling developments will also be discussed as well as the roll of indentation size effect in single asperity plowing. We shall also present results of plowing experiments on HMWPE which is used in orthopaedic prostheses. Finally, some discussion about ongoing work will be presented.