Titanium aluminide and nickel aluminide-based thin coatings were synthesized by magnetron sputtering from intermetallic TiAl and Ni3Al alloy targets on nickel substrates. Both types of aluminide coatings exhibited high surface hardness values that varied with the degree of heat treatment. The hardness of the coatings was investigated using micro- and nano- indentation techniques. In order to estimate the intrinsic strength of the films, the indentation size effects of the apparent hardness were analyzed by the Jönsson-Hogmark model and a model recently proposed by the authors. The analysis indicated that the strengths of the aluminide coatings may considerably exceed their strengths in bulk.

The mechanical performance of thin carbon nitride (CNx) films deposited onto Si(100) substrate by sputtering, was investigated in the load range of 2-20 mN using nanoindentation and nanoscratch techniques. The microstructure of these films was characterized by the inhomogeneous embedding of crystalline grains into a N-poor amorphous matrix. A load dependent transition was found in both the scratch, as well as the friction responses. Below 5 mN, nanoscratching showed completely elastic behavior of the film, while above 10 mN a mixed elastic-plastic behavior was identified. Testing under a normal load of 20 mN resulted in local grooving at the film surface; however, in-situ profiling of the scratch trace showed no evidence of film failure. Both the coefficient of friction (μ), as well as the plastic deformation of the films were found increasing with the normal load applied following an exponential low.

In this work diamond-like carbon films deposited via plasma enhanced chemical vapor deposition with a thickness of 250nm on different substrates are characterized by nanoindentation and microscratching in combination with scanning probe microscopy. The substrates (SU8 photoresist, quartz glass, Si(100) and AlTiC ceramic) provide a wide range of combinations between film and substrate properties. The experimental configuration allows the testing of samples with loads between 1μN and 10mN and a high local resolution. The tribological response of the various film/substrate systems is analysed in two different ways. A single scratch test with linear increasing load and an oscillating wear tests at constant loads is used. The tip radii of the conical diamond tips utilized vary between 0.6 and 6μm. Both, the substrates as well as the tip radii, show a significant influence on the tribological behavior of the systems.

In this study we used nanoindentation to determine mechanical properties and combined nanoindentation with stressed overlayers to determine interfacial fracture energy of a 164 nm thick film of Epon 828/T403 on an aluminized glass substrate. The combination of nanoindentation and a tungsten overlayer was required to trigger delamination of the epoxy film from the aluminized substrate. Mechanics-based models for circular blister formation were then used to determine residual stresses and interfacial fracture energies. This approach showed that the tungsten overlayer had a compressive residual stress of 1.9 GPa which drove blister formation at a fracture energy of 1.9 J/m2 with a phase angle of loading equal to –62°.

Nanoindentation with spherical tipped indenters provides a powerful technique for exploring surface mechanical properties through the application of Hertzian mechanics. The full range of mechanical response can be obtained from elastic, through the yield point to a range of permanent deformation. However, the successful application of the technique requires accurate calibration of the indenter tip geometry. In this paper methods based on indentation into a number of reference materials are used to characterise a range of spherical tipped indenters with nominal radii from 5 to 50 microns. A traceably calibrated metrological AFM is also used to determine the actual shape of one of the indenters. The sensitivity of each method to test parameters is discussed. Coincidence of the data from both methods validates the determined shape of the indenter and offers the opportunity to cross-correlate the calibration of both instruments with high sensitivity.

It has been proposed that with the appropriate models, instrumented indentation test (IIT) data can be reduced to yield the uniaxial stress-strain behavior of the test material. However, very little work has been done to directly compare the results from uniaxial tension and spherical indentation experiments. In this work, indentation and uniaxial tension experiments have been performed on the aluminum alloy 6061-T6. The purpose of these experiments was to specifically explore the accuracy with which the analytical models can be applied to IIT data to predict the uniaxial stress-strain behavior of the aluminum alloy.

Discontinuities during both load and depth controlled continuous indentation tests have been ascribed to dislocation nucleation or multiplication and film fracture. In materials which exhibit permanent deformation prior to a discontinuity in loading, it is more likely that the phenomena is indeed controlled by film fracture, and not the rapid generation of dislocations. The current study has been undertaken to examine the properties of passivating films on engineering alloys. An electrochemical cell coupled with a scanning probe microscope and nanoindentation system allows growth and mechanical testing of passive films on an austenitic stainless steel as well as a titanium alloy. A complementary set of ex situ experiments shows the presence of deformation prior to film fracture with both load – depth sensing techniques as well as imaging the surface topography. The occurrence of excursions is shown in these materials to be linked directly with film fracture, rather than dislocation multiplication.

A new method has been developed to map cracks in 3D using focused ion beam (FIB) microscopy. Using the FIB, many parallel 2D slices are cut in the specimen. Imaging each 2D slice down several directions enables the 3D co-ordinates of features in the slice to be determined. Computer alignment and reconstruction of the 2D slices generates a 3D data set of the analysed zone. The 3D mapping method has been applied to the analysis of the cracks around an indentation site in a Al2O3-5vol.%SiC nanocomposite. This reveals the 3D location and morphology of radial and deep lateral cracks at the indent periphery, surface localised crack clusters, and a crack deficient zone close to the indent centre.

Cyclic nanohardness tests of Al65Cu23Fe12 quasicrystal reveals a different mechanism of plastic deformation as compared with a regular metal. For a polycrystalline metal, the indent depth increases monotonically with load, while for a quasicrystal, it increases stepwise. Probably, the step formation in the Al-Cu-Fe quasicrystal loading curve is due to the structural transformation in the indent. It is known that the quasicrystal structure destroys at high pressure and transforms into a regular crystalline structure. Therefore, it is possible to attribute the pressure drop in the indent to the transformation of the quasicrystalline structure into the crystalline one and extrusion of the plastic polycrystalline metallic phase out from indent. The observation of thin layers extruded out of the indent in Al-Cu-Fe quasicrystal supports this assumption.

Copper films of different thicknesses of 0.2, 0.5, 1 and 2 microns were electroplated on top of the adhesion-promoting barrier layers on <100> single crystal silicon wafers. Controlled Cu grain growth was achieved by annealing films in vacuum.

The Cu film microstructure was characterized using Atomic Force Microscopy and Focused Ion Beam Microscopy. Elastic modulus of 110 to 130 GPa and hardness of 1 to 1.6 GPa were measured using the continuous stiffness option (CSM) of the Nanoindenter XP. Thicker films appeared to be softer in terms of the lower modulus and hardness, exhibiting a classical Hall-Petch relationship between the yield stress and grain size. Lower elastic modulus of thicker films is due to the higher porosity and partially due to the surface roughness. Comparison between the mechanical properties of films on the substrates obtained by nanoindentation and tensile tests of the freestanding Cu films is made.

Nanoindentation testing of amorphous Si layers, formed by self-ion implantation, has been performed, and their mechanical properties compared to crystalline Si. The data was analyzed using finite element modeling of the indentation measurement, allowing the properties of the thin amorphous layers to be separated from those of the underlying material. By modeling the materials as isotropic, elastic-plastic solids with the Mises yield criterion, the amorphous Si is shown to have a hardness about 15% lower than crystalline Si and an elastic modulus about 10% lower. Electron and atomic force microscopies of the indents indicate that the amorphous Si does not undergo phase changes during indentation, and that it may be somewhat more ductile than crystalline Si.

The adhesion between a rigid cylindrical particle with a flat end of radius a and an incompressible elastic film of thickness h deposited on a rigid substrate was studied. The contact surfaces between the particle and the film and between the film and the substrate are either frictionless (slip) or perfectly bonded (stick). Using integral equations, the stress distribution in the contact area was solved and used to obtain the load required to press the particle onto the thin film. Using a thermodynamic method, the pull-off force to separate the particle from the film was obtained numerically and analytically. For a>>h, the pull-off force is proportional to a2/h1/2 if it is frictionless on both contact interfaces and is proportional to a3/h3/2 if it is frictionless between the particle and thin film and bonded between the thin film and the substrate. For a<h/2 the pull-off force is proportional to a3/2 independent of h and the boundary conditions. To verify this the self adhesion of PDMS [poly(dimethylsiloxane)] was determined experimentally and the a3/2 relation was confirmed. The self-adhesion of PDMS was found to increase with the square root of contact time suggesting molecular diffusion as the dominant mechanism.

Nanoindentations resulting from STM tungsten tip contacts with the 5×20 reconstructed surface of a Au(001) crystal around the indentation point have been studied by Scanning Tunnel Microscopy (STM). A novel defect structure is recognised: a row of hillocks extending along more than a hundred nm along the <110> directions stemming from the indentation point. These hillocks have about 7 nm of side and 0.06 nm of height. With the help of simulation models we identify individual hillocks as dislocation configurations consisting of two stacking fault ribbons encompassed by Shockley partials having a stair-rod dislocation as a ridge. It is proposed that hillocks are generated by plastic flow, from an initially nucleated V-shaped dislocation loop intersecting the surface.

Nucleation of dislocations during nanoindentation is a prime example of how nanoscopic details play an important role in the evolution of macroscopic mechanical behavior. Experimental studies of nanoindentation show that surface irregularities, such as steps, alter the mechanical response during indentation. Atomistic simulations using the embedded atom method are used to examine the indentation of a Au(111) crystal with a surface step. The amount of force needed to nucleate dislocations decreases significantly for indentation close to the step. A recently formulated atomistic deformation metric, the slip vector, is used to quantify dislocation content. This metric is used with the local atomic stress to determine the critical resolved shear stress necessary for dislocation nucleation. Atomic stress fields are also compared with continuum calculations performed using non-linear elasticity with a constitutive relation based on the same interatomic potential. This constitutive model shows good agreement of indentation forces and stresses with the atomistic simulations.

Thermomechanical writing occurs as Joule-heated, cantilevered tips imprint nanometer-scale inden (bits) in a 50-nm-thick polymer (PMMA) film. Thermal data reading incorporates the same cantilevers operated in a mode to detect a temperature change when a tip follows the contour of a previously written bit. Binnig et.al [1] demonstrated single-cantilever writing and rading density at 400 Gbit/in2. A micromachined 32 × 32 cantilever array has been fabricated [2] and has demonstrated parallel read/write operation at 150 Gbi/in in2 [3]. Although much progress has been made to develop a thermomechanical data storage device [4], the fundamental process of thermomechanical storage processes by applying atomic force microscope (AFM)-based force detection during thermal operation. We examined the thermomechanics of polymer indentation with respect to time and temperature of interaction. This work impacts the operation of AFM cantilevens for combined thermal writing and reading and understnding of fundamental polymer mesoscopic transport.

During the unloading segment of nanoindentation, time dependent displacement (TDD) accompanies elastic deformation. Consequently the modulus calculated by the Oliver-Pharr scheme can be overestimated. In this paper we present evidences for the influence of the measured modulus by TDD. A modification method is also presented to correct for the effects of TDD by extrapolating the TDD law in the holding process to the beginning of the unloading process. Using this method, the appropriate holding time and unloading rate can be estimated for nanoindentation test to minimise the effects of TDD. The elastic moduli of three materials computed by the modification method are compared with the results without considering the TDD effects.

In this paper a critical comparison of different kinds of surface metrological methods like atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical interferometric profilometry is made, as well as analytical investigations based on both Hertz and Sneddon theories of pure elastic contact, to qualify the real indenter shape function. The results obtained show the advantages and disadvantages of the respective methods by describing a rounded indenter tip.

Deformation during spherical and pointed indentation in (100) crystalline silicon usig a UMIS-2000 nanoindenter has been studied using cross-sectional transmission electron microscopy (XTEM), atomic force microscopy (XTEM), atomic force microscopy and Raman microspectroscopy. XTEM samples were prepard by focused ion beam milling to accurately position the cross-section through the indentations. Indentation loads were chosen below an above the yield point for silicon to investigate the modes of plastic deformation. Slip planes are visible in XTEm micrographs for all indentation loads studied but slip is not the main avenue for plastic deformation. A thin layer of poly-crystalline material has been identified (indexed as Si-XII from diffraction patterns) on the low load indentation, just prior to yield (pop-in during loading). For loading above the yield point, a large region of amorphous silicon was observed directly under the indenter when fast unloading conditions were used. The various microstructures and phase observed below indentations are correlated with load/unload data.

For the indentation of an elastic-plastic homogeneous half-space with a pyramidal indenter, the load theoretically increases with the square of the total penetration depth. Experimental data are presented in the current paper that demonstrate the validity of this relationship for an organic polymer and a Berkovich indenter, provided that appropriate account is taken of the tip defect and viscoplasticity. It is also shown that a simple analytical solution exists for the ratio of the contact depth to the total penetration depth. These findings assist in identifying procedures for obtaining the rate-dependent mechanical properties of thin polymer coatings or polymeric materials with depth-dependent mechanical properties.

A novel technique has been developed to examine site-specific, subsurface microstructures in three dimensions. A 3D data set is collected by successive cross-sectional slicing using a gallium focused ion beam (FIB) and imaging using ion-induced secondary electrons, enabling a 3D microstructure map to be generated using computer-based reconstruction techniques. In the first instance, this 3D FIB mapping technique has been applied to copper-based epitaxial metal multilayer coatings which have been deformed by nanoindentation. It is possible to produce 3D profiles of the deformed subsurface interfaces. These individual interface maps allow analysis of the deformation in terms of both the thickness of individual layers and that of the entire film. Material flow, which is seen as pile-up and residual indent zones around the indent, can thus be precisely characterised. The site at which the sectioning is to be carried out can be chosen with high spatial resolution; consequently, nanoscale mechanical properties can be linked directly with an area's microstructure.

In an attempt to examine the errors involved in this 3D mapping method the 3D FIB map of the surface of a residual indent has been compared to an atomic force microscopy (AFM) scan of the same region. The sources and significance of the errors are discussed with reference to ways in which they might be reduced.