We have developed an optical instrument for real-time overall stress as well as local stress relaxation measurements. The physical principle of the instrument is based on the fact that when a sample is exposed to heating the overall film stress bends the substrate and hillocks, the evidence of the local stress relaxation, form on the surface. Early hillock formation can be observed in real-time with integrated scattering technique, but the overall stress can be readily observed by laser beam deflection. Our instrument integrates laser beam deflection and light scattering techniques to achieve simultaneous overall stress and local stress relaxation measurements. A stress study is presented for an aluminium thin film on a silicon substrate.

Molecular dynamics computer simulations are used to study the effect of substrate temperature on the microstructure of deposited amorphous hydrogenated carbon (a:CH) films. A transition from dense diamond-like films to porous graphite-like films is observed between substrate temperatures of 400K and 600K for a deposition energy of 20 eV. The dense a:CH film grown at 300K and 20 eV has a hardness (˜50 GPa) about half that of a pure carbon (a:C) film grown under the same conditions.

Using the micro-contact printing method we prepared patterned self-assembled monolayers (SAMs) consisting of methyl-terminated alkanethiols of different chain lengths. The samples were characterized using lateral force microscopy (LFM) and the force modulation technique (FMT). In general, higher friction is observed over the short chain regions than over the long chain regions when a low or moderate load is applied to the scanning force microscopy (SFM) tip. For such cases the high friction (short chain) regions are also “softer” as measured by FMT. At high loads, a reversal of the image contrast is observed and the short chain regions show a lower friction than the long chain regions. This image contrast is reversible upon reduction of the applied load.

Carbon nitride (CNx) thin films (0.18<x<0.43), deposited by magnetron sputtering of C in a N2 discharge, have been observed to be extremely resistant to plastic deformation during surface contact (i.e. exhibit a purely elastic response over large strains). Elastic recoveries as high as 90% have been measured by nanoindentation. This paper addresses the problems of estimating Young's modulus (E) and hardness (H) in such cases and shows how different strategies involving analysis of both loading and unloading curves and measuring the work of indentation each present their own problems. The results of some cyclic contact experiments are also presented and possible deformation mechanisms in the fullerene-like CNx structures discussed.

Diamond-Like Carbon films with thicknesses controlled in the 10 to 100 nm range were sputter-deposited on single crystals of MgO. The substrates were prepared with varying roughness from 5 to 50 nm and varying surface dislocation densities from 100 to 2000 disl./μ2. Mechanical properties of the film and film-substrate interactions were investigated with an atomic force microscope retrofitted with a diamond indenter.

The load bearing capacity of the substrate increased with increasing film thickness. As the indenter approached the film-substrate interface, load excursions occurred for the thinner films. No excursion was found for the thick film. Load excursions may be attributed to dislocations nucleating at the interface and/or film delamination.

Diamondlike amorphous hydrogenated carbon is deposited from an expanding thermal argon/acetylene plasma. It is observed that the film quality improves with increasing deposition rate. To obtain the best material quality the admixed acetylene flow has to be of comparable magnitude as the argon ion flow from the plasma source (critical loading). A new method to determine the ion density in an argon/acetylene plasma, by probe measurements, is presented. They reveal that the deposition during critical loading is governed by radicals. It is suggested that acetylene is dissociated once and that the C2H radical is formed dominantly.

Ta-C films have been deposited using FCVA technique. The hardness and Young's modulus of the films on both silicon and sapphire substrates are determined by an ultra low load depth sensing nanoindenter to examine their dependence on the carbon ion energy. An optimum ion energy around 80 to 90 eV has been found, which coincides with the energy at which the sp3 content and film density reach maximum values. At this ion energy, the hardness, modulus and critical load of a 60 nm film on sapphire exhibit maximum values of 60 GPa, 580 GPa and 7 mN, respectively, whilst the frictional coefficient shows a minimum of 0.16.

Hard amorphous hydrogenated carbon, also referred to as diamond-like carbon films, are of technological interest as protection coatings due to their special properties such as high hardness, low friction, low wear, chemical inertness and electrical insulation. In this paper a study of the adhesion properties of multilayer structures composed of DLC/Metal/DLC/substrate is presented. As substrates a ball and roller bearing steel (DIN 1.3505, AISI 52100) was used. After Ar plasma cleaning of the substrate, DLC films were deposited from acetylene gas by rf plasma chemical vapor deposition at a self-bias of -600V. Metal films were deposited in the same chamber by DC magnetron sputtering.

Adhesion of the different layers on the underlying layer was investigated by optical analysis of the coating at the border of Rockwell C indentations made into the substrate. If necessary, additional thin layers are deposited at the particular interface to ensure good adhesion. Further information on the interface quality and hence the adhesion is gained by a second optical analysis of the Rockwell indentation after exposure to ambient air for two weeks.

The multilayer structure containing titanium as the metal layer showed no ablation of the coating around the indentation even after two weeks of exposure to ambient air. Chromium on the other hand already showed some ablation immediately after the indentation as well as still ongoing ablation after two weeks. These results are further corroborated by pin-on-disc tests.

Samples of steel with high chrome content were implanted separately with 75 keV nitrogen ions and with 75 keV boron ions. Implanted doses of each ion species were 2-,4- and 8 × 1017 /cm2. Retained doses were measured using resonant non-Rutherford Backscattering Spectrometry. Tribological properties were determined using a pin-ondisk test with a 6-mm diameter ruby pin with a velocity of 0.94 m/min. Testing was done at 10% humidity with a load of 377g. Wear rate and coefficient of friction were determined from these tests. While reduction in the wear rate for nitrogen implanted materials was observed, greater reduction (more than an order of magnitude) was observed for boron implanted materials. In addition, reduction in the coefficient of friction for high-dose boron implanted materials was observed. Nano-indentation revealed a hardened layer near the surface of the material. Results from grazing incidence x-ray diffraction suggest the formation of Fe2N and Fe3N in the nitrogen implanted materials and Fe3B in the boron implanted materials. Results from transmission electron microscopy will be presented.

D.C. magnetron sputtering from a CVD β-SiC target has been utilized to deposit amorphous SiC thin films on various substrates (Coming 7059 glass, unoxidized Si (111), and sapphire). The approximately 1 μm thick films were grown under various Ar sputtering pressures and flow rates. In situ annealing during deposition in vacuum and ex situ post-deposition annealing in air, both at 500°C for two hours, were implemented to determine their effects on the properties of the films. The mechanical properties were assessed via nanoindentation. An accelerated sphere-on-flat(tape) wear tester was administered to measure the wear volume losses and resultant wear rates under 0.1 and 0.2N loads, a 0.024m/s tape speed, and a 1mm ruby sphere diameter. An atomic force microscope (AFM) established the wear scar volume losses as well as the surface arithmetic roughness (RA) and root mean square roughness (RMS) of the films. The amorphous microstructure was verified by X-ray diffractometry. There was a decreasing trend in the plastic contact damage resistance, hardness, elastic modulus, and wear resistance of the films with increased amounts of Ar gas pressure; on the other hand, annealing of the lower Ar content films generated an increase in these properties compared to the as-deposited films. Atomic force microscopy revealed a more pronounced change in surface features and roughness for the in situ annealed films.

Increasing demands on production processes in terms of performance, reliability and environmental compatibility shape the specification profile for modem wear resistant coating systems. The specification of PVD coated cutting tools by the parameters hardness, wear and frictional behavior, chemical structure or chemical resistance are already known and inspected by small scale tests, e.g. pin on disc or taber abraser test. Hitherto the thermophysical properties of thin film PVD coatings were not characterized completely although the investigation of the thermal diffusivity of coated substrates give information about the thermal barrier function of the deposited coating.

To determine the thermophysical properties of PVD coatings the Jenoptik Thermal Wave Inspection (TWIN) can be used. This nondestructive and contactless measuring system is based on the photothermal spectroscopy. In this paper fundamentals of the TWIN measuring technique are presented as well as first TWIN results of investigated MSIP TiN and TiAlN coated and oxidized high speed steels.

Diamond has been synthesised on copper using Microwave Plasma Chemical Vapour Deposition (MPCVD). The effect of substrate pre-treatment including different polishing and cleaning on diamond nucleation was investigated. It has been found that the residues from the polishing process played an important role in the diamond nucleation. Diamond films synthesised under optimised conditions presented a narrow 1332cm-1 Raman peak. During the ramp down procedure, diamond films usually cracked due to the large thermal mismatch between copper and diamond. To avoid this problem, the effect of growth temperature and deposition time was investigated and a two-step-growth method for stress relief is proposed.

In this study, bismuth dioctyldithiocarbamate has been synthesized, and Its tribological behaviors, such as friction-reducing ability, antiwear property and extreme pressure performance have been respectively evaluated with a ring-on-block test rig and a fourball machine. In addition to correlate its tribological behaviors with the film formed on the metallic rubbing surface under boundary lubrication conditions, surface analyses have been conducted to characterize the surface film by means of Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy(XPS) and energy dispersion of X-ray (EDX).

Test results show the additive compound can effectively improve the friction and wear of the rubbing couples. On the other hand, EDX confirmed the presence of carbon, oxygen, sulfur, nitrogen, bismuth and iron on the surface; AES revealed their depth distribution of atomic concentration percentages. Whereas XPS further disclosed that the composition of the surface film was composed of organic and inorganic species including iron sulfide and sulfate, metallic bismuth, bismuth oxide and sulfide etc. which are conducive to the reduction of friction and wear.

Thin carbon films were grown on Si (111) substrates by ablating a graphite target utilizing an excimer pulsed laser in a UHV Riber © LDM-32 system. Two kinds of films were produced, a highly oriented pyrolytic graphite (HOPG) type and a diamond-like carbon (DLC) type. A relationship of the films microstructure with laser power density and substrate conditions was observed. The HOPG films were homogeneous but the DLC films were heterogeneous, as shown by micrographs. The thin films are monitored and analyzed in situ during the first stages of the deposition process. The monitoring was done by RHEED and the characterization by several surface spectroscopic techniques, AES, XPS and EELS. The formation of a SiC interface was observed for both films due to the reaction of the first carbon species with the substrate surface.

The mechanical properties of pure carbon (C) and carbon-nitrogen (C:N) coatings on thin film head sliders were investigated by continuous drag testing (CDT) and nano-indentation. Comparisons were made in terms of wear protection, elastic modulus and hardness of these two types of carbon films. The C and C:N thin films with various thickness were deposited on thin film head sliders using a facing target sputtering (FTS) system. After 23,000 revolutions of CDT tests, all the testing head sliders which were uncoated and coated with 90 Å C or C:N exhibited some degree of wear damage as indicated in AFM micrographs where that of the uncoated head was the most severe and that of the C:N coated head was the least. Head sliders coated with 1000Å C and C:N were studied under the TriboscopeTM nano-indenter, where load-displacement curves at different maximum loads were recorded. Elastic modulus and hardness were determined from those curves. The results show that elastic modulus and hardness of C:N are greater than that of C. Therefore, one may conclude that both C and C:N behave like a protective coating for the head slider where C:N is better than C, which could be well related to the larger elastic modulus and hardness of C:N.

Using an Atomic Force Microscope with an attachment for indentation, we have measured local, in vitro mechanical properties of healthy femoral artery tissue held in saline solution. The elastic modulus (34.3 kPa) and viscoelastic response (τɛ = 16.9 s and τσ = 29.3 s) of the unstretched, intimal vessel wall have been determined using Sneddon theory and a three element model (standard linear solid) for viscoelastic materials. The procedures necessary to employ the indenting attachment to detect elastic moduli in the kPa range in liquid are described.

A sensitive method to characterize the inelastic deformation of solids is to measure the thermodynamic response of the deforming volume by applying an inelastic strain rate change. Using the step ramp technique on a displacement controlled micro-indentor with Berkovich tip, the apparent activation volumes were determined for linear low density polyethylene, and eutectic Pb-Sn solder for depths less than 10 μm. The results show that the activation volume is a unique measure of a given microstructure.

Silicon bulk micromachined piezoresistive pressure sensors are very sensitive to applied stresses: that is, applied pressure and/or packaging-related stresses. Device encapsulation has been observed to affect the electrical output of the pressure sensor significantly. The magnitude of the zero applied pressure output voltage (i.e., the offset voltage) that can be attributed to a thin film encapsulant is proportional to the magnitude of the roomtemperature thermal stress of that film. Parylene C coatings have been used as encapsulants in this work. Finite element and analytical modeling techniques were used to evaluate the effect of material property variation on the offset of a pressure sensor. A simple, linear expression of offset as a function of a material property parametric group, that includes: parylene thickness, parylene biaxial modulus, parylene CTE, silicon thickness, and annealing temperature; has been established. Experimental analysis of parylene coated pressure sensors and parylene coated silicon and gallium arsenide wafers was performed to confirm the resulting model. Known variations in parylene material properties caused by processing (i.e., uncontrolled deposition, annealing, and high temperature storage) have been used as an experimental vehicle for this purpose. An empirical relationship between offset voltage on parylene coated devices and room-temperature thermal stress on parylene coated wafers that have been exposed to the same processing is a linear expression with a similar slope to the modeling results. Furthermore, stress measurements from parylene coated silicon wafers and parylene coated gallium arsenide wafers have been used to estimate the parylene biaxial modulus (approximately 5000 MPa) and the parylene CTE (approximately 50 ppm/°C) independently. These material properties were observed to shift following parylene annealing and high temperature storage exposure experiments in a manner that is consistent with the established model.

Development of capillary stress in porous xerogels, although ubiquitous, has not been systematically studied. We have used the beam bending technique to measure stress isotherms of microporous thin films prepared by a sol-gel route. The thin films were prepared on deformablesilicon substrates which were then placed in a vacuum system. The automated measurement was carried out by monitoring the deflection of a laser reflected off the substrate while changing the overlying relative pressure of various solvents. The magnitude of the macroscopic bending stress was found to reach a value of 180 MPa at a relative pressure of methanol, P/Po = 0.001. The observed stress is determined by the pore size distribution and is an order of magnitude smaller in mesoporous thin films. Density Functional Theory (DFT) indicates that for the microporous materials, the stress at saturation is compressive and drops as the relative pressure is reduced.

Four-point bending method offers significant advantages over more traditional techniques in measuring adhesion properties of thin polymer films. The former utilizes sandwich structure beams where the polymer film and the interface of interest are placed at the center of two elastic bulks. Such confined geometry closely resembles applications where polymer films are used as dielectric layers in IC interconnect technology. In this work, the bonding between a poly(arylene ether) (PAE) based polymer film and an Al film was studied. Ti layers of several different thickness were used as adhesion promoter. The sandwich samples were made by bonding bulk wafers using an epoxy. Fracture energies were seen to increase with the thickness of the Ti layer. Effects of heat treatment were also studied.