The adhesion of iron films to single crystal Al2O3 substrates was investigated using a pull test. Chromium (300 keV) or nickel (340 keV) ions were implanted to a fluence of 1 × 1015 ions-cm-2 after film deposition. The adhesion test results were widely scattered due to a random distribution of interfacial flaw sizes controlling the failure nucleation. Because Weibull statistics were developed to describe the failure probability due to a population of flaw-initiated cracks, the Weibull distribution was chosen to analyze the data. Modifications in the adhesion strength due to the ion implantation were reflected in the failure distributions. It was found that the chromium ions improved the adhesion of the Fe/Al2O3 system while the implantation of nickel did not.

Fracture energy (Ga) of BPDA-PDA polyimide (PI) on modified and unmodified Si surfaces was measured by the “blister” test as a function of final cure temperature. It is proven quantitatively that surface modification prior to thin film deposition enhances adhesion. Metal adhesion to PI was also measured by the same method. Reproducibility of the data was found to be exceptionally good for both cases. The linear elastic model is quite valid for the test of thin film adhesion. Therefore, it is believed that this test is best suited for Ga measurements in the study of thin film adhesion for microelectronic packaging.

Brittle films of ceramics on metal substrates become mechanically unstable when a critical thickness is exceeded. Experiments have been carried out to investigate this instability for films under tension and compression. Films of cerium oxide gel under tension were prepared by spin-coating a ceria sol onto stainless steel substrates. Films exceeding a critical thickness failed by through-film cracking. The relationship between crack spacing and film thickness was consistent with partial interfacial delamination accompanying film cracking. Films of nickel oxide under compression were prepared by the oxidation of nickel and NiAl and NiCr alloys. The adhesion of the films to the substrates was measured in a double bending beam configuration and by scratch testing. A critical thickness was observed at which adhesion became very low and which depended on the composition of the metal substrate. The observed behaviour is consistent with a buckling instability in the film. In both types of film the conditions for crack propagation appear to determine instability, but the nature of the failure-initiating defects remains obscure.

The fracture behavior of CVD diamond is examined by indentation experiments in which slow crack growth has been observed. Diamond films of 400μm thickness were prepared by plasma-enhanced CVD on a silicon substrate, subsequently removed from the substrate, and polished for indentation testing. A microhardness tester was used to produce Vickers indentations under low load. Crack length measurements over time revealed susceptibility to slow crack growth in ambient testing conditions. The stress-corrosion susceptibility coefficient, N, was measured as 9.3.

A crack terminating perpendicularly at the bimaterial interface is analyzed. Stress distributions for a broad range of elastic moduli and yield strength mismatch are discussed. These results can be used to understand the effect of mechanical properties mismatch on the competition between crack deflecting into the interface and crack penetrating into the base material. The role of microdefects near the interface is explored.

Molecular dynamics simulations which make use of a many-body analytic potential function have been used to study the nanometer-scale indentation of diamond and graphite. We find that the simulation correctly reproduces experimentally determined trends in load versus penetration data. As a result, trends in mechanical properties, e.g. Young's modulus, are also reproduced.

As a film in residual compression delaminates from a substrate, the post-buckling response of the film tends to drive it into the substrate in the region directly behind the delamination front. We consider the process of frictional interaction between the film and the substrate during the delamination process in order to assess the effect of Coulomb friction on the energy release rate, G, driving the delamination. For the case in which the film and the substrate have identical elastic properties, we derive a singular integral equation to determine the relative sliding displacement of the opposing faces of the interface. Using an analytical model, we find that G decreases by about 35% when the coefficient of interfacial friction is equal to one. Using finite element methods, we then investigate the effects of compliance differences between the film and the substrate. We find that, when the film is more compliant than the substrate, frictional interaction is enhanced and the calculated energy release rate decreases substantially. We conclude that frictional effects can account for a significant portion of the energy dissipation during the delamination process, and thus can play an important role in the observed arrest of spreading delaminations.

By using the elastic singular field as a prescribed loading condition, small scale yielding solutions are obtained for a crack normal to the interface between a brittle and a ductile material. Results for both a crack in the brittle material and one in the ductile material are obtained by finite element analysis. The crack tip fields obtained by the finite element analysis are compared with the asymptotic solutions. It is found that near the tip the stress fields approach the asymptotic solutions. If the crack is in the brittle material, the high triaxial stresses are developed near the interface ahead of the crack tip.

To investigate the effect of heat-treatment on the adhesion of Pt thin films to NiO substrates, the strain energy release rate, interfacial fracture toughness and interfacial shear strength were determined from continuous microscratch and continuous microindentation experiments. Samples were prepared by sputtering Pt onto single crystals of NiO, followed by a heat-treatment at temperatures of 300, 500 and 800°C and an oxygen partial pressure of either 0.21 or 10-5 atm. Continuous microscratch tests were performed by driving a conical indenter with either a 1 or 5 μm tip radius simultaneously into and across the Pt film. From the magnitude of the critical load at the point of film delamination and the area of the delaminated piece of the thin film, the strain energy release rate (practical work of adhesion) and interfacial fracture toughness were calculated. The practical work of adhesion and interfacial fracture toughness increased from 0.2 J/m2 and 0.2 MPa√m, respectively, for as-sputtered samples to 4.6 J/m2 and 1 MPa√m for samples heat-treated at 500°C and 10-5 atm. Preliminary analysis of continuous microindentation results for Pt/NiO samples yielded interfacial shear strengths of 270 MPa for as-sputtered samples and 725 MPa for samples heat-treated at 500°C and 10-5 atm. While these values are in good agreement with those determined by other methods for metal-ceramic systems, there are sufficient differences in test method for a single system to require additional analysis of the proposed models.

The adhesion of Au, Ag, Pb, Sn, In, Cu, Cd, Mg, Ca films to vacuum-cleaved Al2O3, MgO and SiO2 single crystals has been studied. It is shownf -4hat for botn Al2O3 and MgO the level of adhesion is slightly higher than that for SiO2 and tends to increase with chemical activity of deposited metals. As a result, the adhesion varies from the level of van der Waals forces to the level of chemical interaction.

The effects of forming interlayers and/or bombarding with ions on the tribological properties of the sputter-deposited MoS2 films were investigated. The MoS2 films on substrates of Ti-alloy, martensitic stainless steel and high speed tool steel with TIN interlayers were evaluated by ball/disk sliding tests under ultra-high vacuum condition. Furthermore, nitrogen- or sulfer-ion-bombarded MoS2 films tested too. The test results showed correlation between the surface hardness of substrates and the wear life of MoS2 films. The wear life of the ion-bombarded MoS2 films was improved by mixing film/substrate interface.

Molecularly doped polymers are widely used in copiers and printers. During the imaging process, toner particles and the cleaning blade wear the photoconductor drum as it rotates. This paper quantizes the abrasive wear of molecularly doped polycarbonate coatings. No clear correlation is found between the wear rate and measured mechanical properties. The surface topography is dominated by a series of parallel grooves with a spacing of approximately 0.1 pm.

A surface acoustic wave (SAW) sensor is used to study the relative humidity response of polyimide films where interfacial and surface properties are varied. The relationship between these responses and the relative adhesion strength of these films is of particular interest since it could have application as a nondestructive, quantitative measure of adhesion strength. The results show clear differences in the SAW humidity response for cured and uncured films. There are also significant differences in the SAW humidity response for films applied with and without adhesion promoter. In addition the humidity response has proven to be particularly sensitive to the surface treatment of the polyimide film. These results suggest applications of the SAW sensor as a cure indicator, an in-situ sensor for the monitoring of film surface properties in process control applications and as an adhesion sensor.

The adhesion of a sputtered titanium-tungsten gold (Ti-W/Au) thin film on alumina substrates is found to be weakened after being stressed at temperatures above 575°C, due to depletion of the Ti-W base metal. Thin films deposited on substrates having a fine grain structure and as fired surfaces, however, maintained their adherence at temperatures up to 650°C.

Ag and Ag/Ti films were deposited on ZrO2 substrates by ion-beam-assisted deposition. Adhesion of these films was measured before and after heat treatment at 250°C in air. The results show that a graded interface between Ag and Ti was necessary for the Ag films to survive the heat treatment. Reciprocating pin-on-disc tests were performed at 150°C after heat treatment to investigate the relationship between adhesion and tribological properties. The failure of Ag and Ag/Ti (without graded interface) films was also observed during wear tests. However, this Ag film failure did not result in negative effects. All three Ag-coated substrates show better tribological behavior.

Amorphous “Diamond-like” carbon films were deposited on plasma-free substrates at low temperature by the Facing Targets Sputtering (FTS) method. Tribological characteristics determined by tap, scratch and slide tests were much better than those for amorphous carbon films deposited by the conventional Magnetron Sputtering (MS) method. Consequently, these films deposited by the FTS method were surely useful for protective layers in rigid magnetic disk.

Tribological troubles and tape-curling of perpendicular magnetic recording tapes are critical for their practical use. Thin films of a wear resistant and electrically conductive Fe-Mo-B based alloy were prepared on plasma-free tape substrates by the facing targets sputtering (FTS) method for applying them as protective layers in the magnetic tapes. The films were perfectly amorphous, very flexible and almost non-magnetic. The alloy targets for these films contained molybdenum atoms at a concentration as high as 24 at%. The Mo atomic weight is higher than that of working gas atoms Ar and Kr. Accordingly, not only Ar but also Kr atoms were recoiled from the target planes and then bombarded the growing layers to cause large compressive stress in the deposited films. Therefore, these protective films must be very thin to avoid tape-curling. Protective films as thin as 100 Å could largely reduce the dynamical friction coefficients of the surfaces of magnetic tapes owing to the hardness of their ceramic phase. In addition to this merit they possessed electrical resistivity as small as 1.2×10-4 Ω·cm. owing to their metallic binder phase. Consequently they are applicable as protective layers of curl-free magnetic tapes.

We report on a recently commercialized Diamond-Like Carbon (DLC) coating that has been deposited on polycarbonate at near room temperature, via a unique ion beam system. Aspects of high speed impact behavior, chemical resistance, abrasion resistance, and thermal stability of the coating are examined. Results of scanning electron microscopy studies indicate that adhesion of the DLC coating is very good; no delamination of the coating was found on ballistically tested specimens. The well-bonded DLC coating did not cause the impact performance of polycarbonate to become brittle. Chemical exposure test results show that the DLC coating is capable of protecting polycarbonate from chemical attack by aggressive organic liquids. These ion beam deposited DLC coatings have considerable potential as protective coatings for optical systems.

The tribological properties and the slid surface profiles of Co-Cr thin films deposited by Facing Targets sputtering and Magnetron sputtering methods were investigated in regard to the durability of flexible disks. Co-Cr thin films with columnless microstructure and homogeneously packed particles were much tougher than ones with columnar microstructure for tribological test. The Co-Cr films deposited by conventional Magnetron sputtering method revealed typically columnar structure, while ones deposited by Facing Target sputtering method did columnless microstructure. This indicates probably homogeneous distribution of strong bonding forces between grain boundaries throughout the films, because no brittle fracture was observed even after the delamination between a plastic substrate and the CoOx/ Co-Cr / Ni-Fe triple layers took place by application of excess stresses. It was found that difference in morphology of Co-Cr thin film between Facing Target sputtering and conventional Magnetron sputtering methods was much significant.

Fundamental mechanical properties of a-C:H (amorphous or “diamond-like” carbon, DLC) thin film coatings have been investigated. Coatings were deposited by a methane-argon RF plasma on polycarbonate films. Tensile stress-strain behavior of the coated polymer was studied using an extensometer to monitor strain. The differences in moduli between uncoated and coated samples were used to calculate apparent coating moduli, which varied from 1 GPA to 82 GPa. The mode of failure was observed via in-situ optical microscopy during deformation. Intrinsic bond strength of the coating/substrate interface was estimated from crack spacings in the deformed coating.