ABSTRACTS

The following is a list of the abstracts for papers which will be presented in the THIRD INTERNATIONAL SYMPOSIUM ON ADHESION ASPECTS OF THIN FILMS(INCLUDING ADHESION MEASUREMENT AND METALLIZED PLASTICS). The listing is alphabetical by presenting author. This list is updated continually to add abstracts as they become available and make appropriate corrections. This list may be conveniently searched by using the editor provided with most popular browsers (e.g. Microsoft Explorer, Netscape, ... etc.)

Investigation of interfacial interactions between polymer and ceramic coatings

(Abstract not yet available)

Musashino, Tokyo 180-8633 JAPAN

Two Critical Events Observed on Cu Films on Glass Substrate in the Micro- Scratch Test

Copper films of 100-200nm thick were deposited on the glass substrate of Corning 7059. The adhesion was examined with a vibrating microscratch tester, employing the diamond stylus whose radius was 15 and 100 um(micrometer). The adhesive failure can be observed in the friction-load curve. Before the film suffered from the adhesive failure, another critical point was observed at a light load in the Cu/glass system. Dependence of the two critical points on the film thickness and the stylus radius was studied in detail. When the stylus of 100um was employed, both the critical loads increased as the film thickness increased. However, when the stylus of 15 um was employed, while the final critical load increased in the same manner, the first critical point moved to a lighter load as the film thickness increased. A nano-hardness tester was applied to this copper/glass system to study the surface hardness. The film surface was found harder for thinner films, which suggests that the first critical load corresponds to the fracture at the film surface and the second failure corresponds to the adhesive failure at the film-substrate interface.

Hard and Elastic Carbon Nitride Films for Tribological Applications

During the last decade, carbon nitrides (CN_X) have been discussed as a potential material for many tribological uses because of their particular mechanical properties. Although the synthesis of single-phase crystal films remains a open challenge, amorphous CN_X film with low N concentration are already industrially applied and many patents of products using CN_X films have been claimed.

A new kind of carbon-based material deposited by PVD, the "fullerene-like" carbon nitride has been recently reported. Due to its unique microstructure, consisting of bent, cross-linked and frequently intersecting nitrogen-containing graphite sheets, this CN_X phase has interesting mechanical properties, such as high hardness (40-60 GPa) and an extreme elastic recovery (90%) in indentation experiments.

In this work, a study of "fullerene-like" CN_X films deposited by dc magnetron sputtering on different substrates is presented. The effects of the deposition parameters on mechanical and tribological properties have been investigated; the results are correlated to changes in microstructure and morphology. Adhesion aspects of films deposited on steel substrates are particularly discussed. Furthermore, a novel application for medical implants is also reported.

Thin Film Residual Stress: Theory and Experiment

Almost all films grown on solid substrates are deposited in a state stress. The origin of these stresses include thermal stresses owing to a difference in thermal expansion coefficients of the film and substrate, epitaxial stresses owing to lattice matching at the film-substrate interface when the bulk equilibrium lattice spacings of the film and substrate are different, and residual (or growth) stresses resulting from processes that occur during film growth. Recently there has been a great deal of experimental and theoretical study of residual stresses, particularly for films that deposit by island (Volmer-Weber) growth. These stresses can become quite large, of order the yield stress, and contribute to a loss of thin film adhesion. The stress generated during growth can display a great deal of structure as a function of thickness, and a particular film can be under compression or tension depending on the stage of growth. Also, discontinuous changes in the film stress have been observed during deposition interrupts. The experimental aspects of residual stress generation for films produced by physical vapor deposition and by electrochemical deposition will be review. This will be followed by a discussion of the different mechanisms that have been proposed to explain the observed behavior.

Laminated Composite Coatings: a Solution for Improved Adhesion

In cutting applications involving thin film coated tools, the coatings are expected to be hard, wear and oxidation resistant, as well as strongly adhesion to the bulk material. In fact, due to the high loads involved in the contacts, the main efforts are supported by the substrates and it was supposed that the coatings follow their elastic or plastic deformation, with a subsequent delay of the crack propagation.

The commercial coatings used for these applications are generally monolithic or compositional gradient films. Even the multilayer nanostructured coatings will behaviour under these loads as monolithic coatings and the crack generation and propagation will be ruled by the same mechanisms as in the monolithic coatings. Hence, the coatings to behave satisfactorily, they must be able to deflect along the substrate without cracking, and to exhibit different fracture mechanisms with a subsequent increase of the adhesion. In order to promote such an increase of the adhesion of the monolithic coatings, such as the very common Ti-Al-N, thin ductile metal layers (few tenths of nanometres) were introduced among thick Ti-Al-N layers as long period multilayer coatings. The thin metal layers (interlayers) will be able to increase the coating deformation and will dissipate part of the energy generated during the load, which will decrease the crack propagation and ensure the highest adhesion. And finally, these interlayers will behaviour as energy sinkers without decrease the other relevant mechanical properties such as hardness.

1) Unité de Physico-Chimie et de Physique des Matériaux, Université catholique de Louvain, Croix du Sud 1, Louvain-la-Neuve, B-1348, BELGIUM

2) Neurotech SA, Louvain-la-Neuve, BELGIUM

Adherence Improvement for Metallized Silicone Films

Silicone rubber is routinely used for biomedical applications and, in several cases, the polymer surface has to be covered with a thin layer of a biocompatible metal such as titanium or platinum. The adhesion of a metal film on a silicone surface, however, constitutes a challenging issue.

In this contribution, we propose several strategies for the adherence improvement of evaporated titanium on a polydimethylsiloxane (PDMS) film. In particular, the 2 keV Ar pre-bombardment of the PDMS film proves to be very efficient, as indicated by adherence (Scotch) tests. Complementary treatments involve the thermal annealing of the PDMS film and its cleaning with selected solvents. At each step of the study, time-of-flight secondary ion mass spectrometry (ToF-SIMS) is used as a diagnostic tool for the assessment of the sample surfaces.

Via a procedure involving the deposition of minute amounts of gold on the samples to enhance ionization,¹ ToF-SIMS reveals the presence of short PDMS chains on the surface of the received films. In particular, the positive mass spectra exhibit a well-defined distribution of intact oligomers extending between 800 and 4000 Da, a molecular weight beyond which entanglement is expected to prevent entire molecule desorption. The argon bombardment/ hexane cleaning treatments of the films remove this oligomer overlayer and, in parallel, lead to a significant adherence improvement of the titanium layer. Therefore, the ToF-SIMS results strongly support a scenario in which the adhesion of titanium on the untreated films is limited by the presence of short, mobile oligomers on the polymer surface. They also suggest that, in addition to the oligomer layer removal, Ar pre-bombardment creates reactive sites that induce a stronger binding of the evaporated metal atoms on the surface and a two-dimensional growth of the metal film.

[1] Delcorte, A.; Médard, N.; Bertrand, P. Anal. Chem. 2002, 74, 4955-4968.

1715 Dell Ave., Campbell, CA 95008,

Scratch-adhesion Testing of Display Coatings

To study mechanical properties of thin conductive coatings, a novel test procedure has been developed using the Micro-tribometer mod. UMT-2 with electrical surface resistance measurements. Each display sample is cut into 10 x 50 mm test specimens and clamped between two electrical connectors on a lower stage. A constant normal load is applied via a close-loop feed-back servo control. In scratch and adhesion tests, the lower stage is stationary, the upper tool is a diamond indenter making unidirectional linear motions. In wear tests, the lower stage is either stationary or linearly reciprocating, the upper tool is either same diamond indenter or sapphire ball, either linearly reciprocating (when stage is stationary) or stationary (when stage is reciprocating). During testing, normal load and electrical surface resistance (ESR) are monitored and recorded. When the conductive coating is present, ESR is at its low level reflecting the coating resistivity; when the coating is completely cut (worn) through , ESR is at its maximum level corresponding to dielectric properties of the substrate. A number of LCD and LED displays samples with different coating materials and deposition technologies were tested, three times each. This test procedure, based on the precision servo-control of normal load and simultaneous measurements of surface electrical resistance, allows for accurate and repeatable quantitative evaluation of scratch, adhesion and wear of information display and other conductive coatings.

Measurements of Interfacial Fracture Toughness Between Zno Film and Si Substrate by the Indentation Delamination Test*

To measure interfacial fracture toughness or the nominally called adhesion energy of a thin film attached to a substrate by the indentation delamination test, one has to determine the compressive stress induced by an indentation load. The indentation load-induced compressive stress can be calculated from the indentation volume, which is usually determined from the indentation displacement in the instrumented indentation test. However, there are still many micro-indentation systems, which are lack of displacement measurement devices. We developed a new method to determine the indentation volume without measurements of the indentation displacement. The indentation volume is determined from the geometry of an indentor tip, the indentation load and the composite hardness of a film/substrate system. Combining the composite hardness model into the delamination model, we therefore derived a formula to determine the critical strain energy release rate from the delamination radius and the indentation load. Applying this novel method to the systems of ZnO thin films sputtering-deposited on Si substrates with film thicknesses ranging from 0.832 to 1.535 µm, we determined the adhesion energies to be about 12.2 J/m² in the absent of buckling of delaminated films. The measured adhesion energy decreased from 11.7 J/m² to 9.2 J/m² with increasing the applied indentation load when buckling occurred, which was attributed to the change in the phase angle between the mode I and II stress intensity factors at the interfacial crack. The pure mode I adhesion energy was thus evaluated to be 10.4 J/m² for the investigated ZnO/Si systems. This novel method is particularly useful in measurements of adhesion energies of thin films with indentation equipment without any displacement measurement devices.

* This project was supported by the Hong Kong Research Grants Council.

** Corresponding author, Tel. (852) 2358-7192, Fax (852) 2358-1543, E-mail: mezhangt@ust.hk

Mechanical Stability of a TiO2 Coating Deposited on a Polycarbonate Substrate

Various experimental methods have been developed to determine the adhesive properties of a thin film or coating on a substrate. These techniques differ in the way a controlled force is applied to cause directly, or indirectly an interfacial failure. For example reasonable precise measurements of adhesion energies have been obtained recently by methods such as the buldge test, but applications remain limited to suitable systems, as the ones generally including a ductile thin layer. For brittle films, other techniques are needed. In our case, for analysing the mechanical stability of a TiO₂ coating on a polycarbonate substrate, we choose to apply a tensile force to the system, then follow the evolution of damage resulting from increasing the imposed strain. Film cracking was observed first, then debonding. Critical parameters associated with these observations are deduced through models based on fracture mechanics concepts, namely the cracking energy of the coating, a dimensionless cracking number and the critical interfacial energy for film debonding. A sequential recording of the events activated under tension will be presented and discussed.

ANSTO Materials & Science Engineering; PMB 1 Menai

NSW 2234 AUSTRALIA

Long-Sustaining Hydrophilic Modification of PET Surface for Artificial Ligament

A hydrophilic group was substituted photo-chemically on PET (polyethylene terephthalate) surface with an ArF excimer laser irradiation. Furthermore, the hydrophilic surface was maintained for a long-time in order to transplant in human bodies.

PET has been widely used for an artificial ligament because of its mechanical strength and immune reaction. However, it has poor affinity with biological tissues. In generally, the plasma irradiation has been used for hydrophilic treatment of PET surface. But in this method, hydrophilic property cannot be maintained for one hour or more.

Then, the OH group was substituted on the PET surface with ArF laser irradiation and in the presence of water. By this photochemical reaction, hydrophilic property was maintained for 24 hours. In this treatment, several substrate temperatures were examined.

As a result, the contact angle with water became to 24 degrees at the laser shot number of 500 with the laser fluence of 10mJ/cm² at 50 degrees centigrade of substrate temperature. And the contact angle was kept for less than a week. In case of 10 degrees centigrade substrate temperature, the contact angel with water became 38 degrees and it was maintained for a week or more. The results revealed that the hydrophilic property was maintained by lowering the temperature of the substrate.

Faculty of Engineering, Kanazawa University, 2-40-20, Kodatsuno,

Kanazawa 920-8667, JAPAN

Mechanical Property of the Sputtered Ptfe Thin Film

Mechanical properties of polytetrafluoroethylene (PTFE) thin films sputtered on the metal substrates were evaluated using two pin-on-disk type apparatuses. The sputtered PTFE thin film had a plane and uniform structure. The scratch durability of the PTFE thin film deposited on the copper substrate showed higher value than that on the nickel substrate. The friction and scratch durability related with hardness of the metal substrates. In addition, we found that this durability related with the adhesion to the substrate due to the calculation of the mean contact pressure and measurement of the adhesion strength. The adhesion strength between the PTFE film and evaporated metal films was higher than that between the bulk PTFE and the metal thin films. This difference was estimated to be due to the difference of chemical bonding state between the PTFE thin film and the bulk PTFE. In order to increase adhesion strength between the PTFE thin film and metal substrate, copper (Cu)-polytetrafluoroethylene (PTFE) thin film was deposited by RF sputtering with PTFE-Cu composite target. Although the sputtering rate of the PTFE slightly decreases with increase of the pressure during the sputtering, this rate of the Cu drastically decreases. This drastically decrease would be related with the Cu oxidation when it is sputtered at higher pressure. Electric resistance of the PTFE-Cu thin film sputtered on the glass substrate drastically increases with increase of the pressure when it is sputtered at the pressure beyond 5 mTorr. The PTFE-Cu thin film was introduced between the PTFE thin film and the Cu substrate (PTFE / PTFE-Cu / Cu substrate), and evaluated its tribological property. The friction and scratch durability of the PTFE / PTFE-Cu / Cu substrate improved compared to that of the PTFE thin film sputtered on the Cu substrate. The PTFE-Cu layer would act as a functional gradient material layer.

Characterization of Polyethylene-metal Thin Films by Vapor Deposition

Polyethylene (PE) thin film, gold (Au) thin film, aluminum (Al) thin film, PE/Au composite (PE-Au) thin film and PE/Al composite (PE-Al) thin film were deposited by conventional vapor deposition apparatus. The PE thin film deposited at low temperature had a plane and uniform structure. A lot of particles were observed at the surface of the PE thin film deposited at high temperature. The deposition rate of the PE shows two orders higher value than that of these metal thin films. The deposition rates of these metal thin films show almost the same value with increase of the pressure during vapor deposition. The deposition rate of the PE decreases with increase of the pressure. The resistivity of the PE-Au and PE-Al thin films decreases with increase of the pressure. But the resistivity of the PE-Al thin film decreased drastically with increase of the pressure. This drastically decrease is due to the oxidation of the Al in the PE-Al thin film. The PE-Au and PE-Al thin films were introduced between the PE thin film and the Al substrate. Although the scratch durability of the PE thin film deposited on the Al substrate deteriorates due to the introduction of the PE-Au layer, it improves due to the introduction of the PE-Al layer. The PE-Al layer would act as a functional gradient material layer.

1) Materials Centre, National Physical Laboratory - NPL, Queens Road, Teddington, Middlesex, UK TW11 0LW, UK

2) Materials Technology Centre, Flemish Institute for Technological Research - VITO, Boeretang 200, B-2400 Mol, BELGIUM

Advances in Adhesion Measurement Good Practice: Use of a Certified Reference Material for Evaluating the Performance of Scratch Test Instrumentation

Adhesive bonding of a coating to its substrate is routinely tested using the scratch test in which a Rockwell C diamond stylus is drawn across the surface of the coating-substrate system to be tested, under progressive load. A scratch track is formed in which a number of consecutive failure events occur at particular critical loads, Lc. Scratch test calibration, cleaning and test procedures are defined by a European Standard prEN 1071-3 established by the European Standards Committee CEN TC184 WG5 [1]. Pre-normative research revealed that a damaged or incorrect stylus tip shape was a major source of error in the scratch test method [2]. An EC funded project - REMAST - developed and certified a reference material (CRM) as a quality control tool for the testing and qualification of scratch test instruments [3, 4].

This paper reviews the certification and shows how the multiplicity of scratch test data obtained could be statistically analysed to unravel the effects of stylus, lab and specimen on Lc. This ability of the CRM to diagnose the causes of differences between scratch test results led to the publishing of a Measurement Good Practice Guide (GPG) [5]. This paper will summarise the strategies, described in the GPG, for using the CRM to evaluate the performance and maintain quality control of a scratch test instrument and also for comparing results from two different instruments.

references

[1] European Standard prEN1071-3:2000:E, Advanced technical ceramics - Methods of test for ceramic coatings - Part 3: Determination of adhesion and other mechanical failure modes by a scratch test, CEN Management Centre, Stassartstraat 36, B-1050 Brussels, Belgium.

[2] European Commission - Measurements and Testing Programme, 'Development and Validation of Test Methods for Thin Hard Coatings (FASTE)', contract MAT1-CT94/0045, completed 31/12/97.

[3] European Commission - Standards, Measurements and Testing Programme, Project 'A Certified Reference Material for the Scratch Test - REMAST', contract SMT4-CT98/2238, completed 31/12/2001.

[4] Certified Reference Material for the Scratch Test - BCR-692, available from the Institute for Reference Materials and Measurements, European Commission, Directorate General, Joint Research Centre, http://www.irmm.jrc.be

[5] NPL Measurement Good Practice Guide No.54 "The Scratch Test: Calibration, Validation and the use of a Certified Reference Material.", N. M. Jennett and S. Owen-Jones, NPL Materials Centre.

Recent Developments in Instrumented (Nano)indentation for the Measurement of Coating Mechanical Properties and Adhesion

Instrumented (Nano)indentation (IIT) is one of the very few techniques that can measure both the elastic and plastic properties of very small volumes of materials. Recently an EC Funded project - INDICOAT- has shown that the properties of thin coatings can be determined by nanoindentation, even when the normal indentation response includes a significant component due to the substrate. This method is currently being drafted into an international standard (ISO/CD 14577 part 4). This paper describes the INDICOAT method and shows how the results are in agreement with those obtained by acoustical test methods (in particular Surface Acoustic Wave Spectroscopy, SAWS, and Impact Excitation). Indeed the combination of acoustical and nanoindentation information enables a validated set of values for the thickness, Young's modulus and Poisson ratio for a coating to be obtained.

A further development is also described in which the pendulum design of a MicroMaterials Nanotest IIT instrument is exploited to enable single and repeated nano-impact testing. Precise and accurate measurements of impact energy are possible and there is potential to develop new test methods to evaluate the damage tolerance and adhesion of coatings.

Hardness Effect on Adhesion Strength of Tio₂ Films on Glass Substrates Measured by Scratching Test

The effect of film hardness on the evaluation of scratch adhesion strength of TiO₂ thin films on glass substrates was investigated. The adhesion is essentially the character peculiar to the interface between the film and the substrate, but the value of the adhesion strength evaluated by the scratching test has been observed to depend on the hardness of the film. In order to investigate the hardness effect on the value of scratch adhesion, multi-layers of Ti/TiN were deposited on top of the TiO₂ sample. The hardness of the multi-layer has been found to change with the period of the Ti/TiN combination. We have used the multi-layer of various periods as the overcoat of various hardness. The adhesion evaluated by scratching approximated to show a monotonous increase with the hardness of the overcoat. The scratching is supposed to include two processes, namely, indentation and plowing of the film materials. In the present report, the indentation is assumed to be a main factor to detach the film from the substrate. The elastic deformation effect in the indentation is separated and the peeling of the film is discussed by the elastic energy stored during the deformation.

Deposition of Aluminum on Three Dimensional Polymer Substrates

In recent years an increasingly integration of additional electronics in cars like navigation systems or Electronic Stability Programme (ESP) can be noted. By the integration of many electronic devices the question of protection against electromagnetic influences is important. An EMC compatible component can be realized by a multifunctional polymer component which supports even the low weight construction aspects. Polymer components with EMC coatings offer a cheap, large scale production capable alternative. In the presented investigations 3D polymer samples were coated with an aluminum coating which has good properties for EMC protection. The aim was to reach a dense and uniformly deposited aluminum layer all over the polymer substrates with regard to their geometry. The samples were coated in low temperature magnetron sputter processes, with either pulsed or DC power management. In Calo tests the layer thickness of samples were evaluated. Following, the density of aluminum layer was proofed by light microscopy. An analysis of the layer uniformity was made by SEM takings of cross section polishes. Furthermore, adhesion is an important factor of polymer coating. An evaluation of adhesion took place by scratch testing, applied tape tests and lattice cut tests. The results showed no adhesion problems between aluminum layer and polymer substrate. Comprising, a dense aluminum layer was deposited all over the different geometric specifications of polymer samples. The layer thickness could align over the geometric conditions in various deposition processes.

F. Klocke, D. Lung and J. Grams; Laboratory for Machine Tools and Production Engineering (WZL), Aachen University, Steinbachstrasse 53, 52074 Aachen, GERMANY

Selection of Efficient Coatings for Milling Inconel 718 Considering its Adhesion Properties

The main goal of the co-operative research centre SFB 442 are environmentally compatible tribological systems in the machine tool. Due to the different physical properties of biodegradable synthetic esters in comparison to a water based emulsion the diminished cooling of the cutting process is supposed to be compensated by the application of PVD-coatings.

Ni-alloys like Inconel 718 are rated difficult to machine materials due to their low thermal conductivity, tendency to cold hardening and forming of material adhesion on the cutting tools. Wear-resistant coatings may improve the tribological properties of cutting tools for milling Inconel 718, but the efficiency of them depends considerably on the adhesion between the coating and the tool substrate.

In this work three different tests are compared for the investigation of the adhesion properties of promising PVD- and CVD-coatings. Concentrated attention was given to the impact test, being a convenient method for the characterization of coating fatigue properties as well as coating adhesive and cohesive failure modes.

The results shall serve as a prediction of the cutting properties of as such coated cutting tools. Furthermore, coatings have been analyzed concerning their lubricating function in cutting and in a pin-on-disc tribological test. All results will be presented in this paper.

Acknowledgments:

The results of this paper were obtained at the Aachen University of Technology (RWTH) within the SFB442 corp. research centre on "Environmentally Compatible Tribosystems". The authors wish to record their gratitude to the Deutsche Forschungsgemeinschaft (DFG) for its generous support.

State-of-the-art Overview: Surface Modification of Polymers by Ion Assisted Reaction

Research on surface modification of polymers using ion assisted reaction (IAR) is reviewed with outstanding results regarding the hydrophilicity and adhesion of polymers. The IAR is an emerging technology in the field of surface modification of polymers which gives stable functional groups on surfaces and accomplishes permanent hydrophilicity and strong adhesion of polymers. The low contact angles below 30° and high surface energies 60-70 mJ/m² are achieved on the IAR treated thermoplastic and thermosetting polymers such as polyethylene (PE), poly(propylene) (PP), poly(vinylidenefluoride) (PVDF), poly(tetrafluoroethylene) (PTFE), poly(carbonate) (PC), poly(ethersulfone) (PES), poly(imide) (PI), etc. In this paper, the experimental results of IAR treated polymers are presented in detail and the changes in physical and chemical properties on the IAR treated polymer surfaces are investigated by XPS, SEM, AFM, etc. On the bases of these results, the interaction mechanisms among energetic ions, reactive gas molecules, and polymer molecules involved in the IAR treatment are discussed. The review shows breakthroughs of IAR treatment in various industrial fields which include PVDF thin film speaker, conductive silicon rubber tape for plasma display panel (PDP), PTFE adhesive tapes, cell culture dishes, ITO film on plastics. This paper also describes the pilot production systems for IAR the treatment which are batch type for sheets and roll-to-roll type for web. Finally, the future applications of the IAR technique are to be suggested in the high tech area such as opto-electronic devices, semiconductors, biomaterials, etc.

Department of Electrical Engineering, Tokai University, 1117 Kitakaname, Hiratsuka Kanagawa 259-1292, in JAPAN

SiO₂ Film Lamination on Nonlinear Optical Crystal with Photochemical Oxidization of Silicone Oil

A SiO₂ film was formed on KDP crystal with ArF laser induced photochemical oxidization by using silicone oil. The silicone oil was spin-coated on the KDP surface, and an ArF laser was irradiated in oxygen atmosphere. By this treatment, the organic silicone oil was oxidized with O₂ and turn to the ceramic of SiO₂ film. The chemical reaction and photochemical reaction are given in the following chemical equation: (-O-Si(CH₃)₂-O-)n + O₂ + hv --- SiO₂ +CO₂ + H₂O

Infrared spectroscopy analysis (FT-IR) was carried out to investigate the laminating film. The peak of CH3 band decreased as the laser shots number increased. On the other hand, the peak of Si-O increased.

Adhesion of SiLK^TM Dielectric in Semiconductor Interconnects

Interfacial adhesion of dielectric materials in semiconductor devices is important to their reliabilities. SiLK^TM is an aromatic hydrocarbon thermosetting polymer from Dow Chemical, it is applied to a substrate by spin-coating and curing, and its typical dielectric constant is 2.65. In semiconductor industries, SiLK^TM has been studied as a possible dielectric layer in the back-end-of-line (BEOL) of an ultra-large-scale integrated (ULSI) microprocessor chip. Adhesion of SiLK^TM has been investigated in this study. An adhesion promoter, a silane coupling agent, is employed to enhance the interface fracture toughness for the SiLK^TM-to-SiO₂ (or Si₃N₄) interface while inorganic dielectric materials are applied to SiLK^TM without treating its surface. Practical adhesion strength is determined by 90^o peel test for which a thin (~20 m) layer of polyimide is employed as a peel-backing layer. Locus of failure usually determined with XPS is indicative of poor or strong adhesion. Wetting issues will also be discussed.

A Investigation on Tissue and Blood Compatibility of Dlc and Cnx Coatings

Despite promising studies of diamond-like carbon (DLC) supporting their biomedical applications, few data on its blood compatibility are reported. Carbon nitride (CNx) has similar structural characterization to DLC. Its excellent mechanical and tribological properties are comparable to that of DLC. However, it is difficult to find the reports on the investigations of the biocompatibility of CNx so far. In this work, tissue and blood compatibility of CNx and DLC coatings prepared by DC magnetron sputtering were studied. The effects of CNx and DLC coatings on cultures of mouse fibroblasts and human endothelial cells were determined by scanning electron microscopy. The results showed that the coatings caused no adverse effects on the cells. CNx coating provided a comparable or better surface for the normal cellular attachment, growth, and morphology as compared to DLC. At the same time, both coatings exhibited lower platelet adhesion and longer blood-clotting time compared with the control silicon wafer. The coatings also exhibited strong corrosion resistance. These results support the tissue and blood compatibility of CNx and DLC and should initiate an interest in the biomedical applications of CNx coating.

# This work is supported by NSFC under Grant No.10075034 and SRF for ROCS, SEM. This work is also jointly supported by Ministry of Education of China and Tianjin Municipality.

A Study on Cell Attachment of Ti-containing Coatings

Ti-containing coatings such as TiN, TiC, and TiCN are appropriate materials for use in protective and biocompatible ones on artificial implants, due to their desirable wear performance, high hardness, low coefficient of friction, and strong adhesion on a range of materials. In this work, TiN, TiC, and TiCN coatings were synthesized by means of multi-arc ion-plated. The Auger analysis gave the surface element constituents of TiN, TiC, and TiNC coatings and their depth distribution. XRD analysis indicated a strong (111) preferred orientation for TiN and TiCN coatings. High negative bias and low deposition temperature resulted in a positive effect on the referred orientation. The attachment of 3T3 mouse fibroblasts and human endothelial cells on TiN, TiC, TiCN coatings were discussed. The results showed that the coatings provided the surfaces for the normal cellular attachment, growth, and morphology, which support the tissue compatibility of the Ti-containing coatings.

# This work is supported by SRF for ROCS, SEM and jointly supported by Ministry of Education of China and Tianjin Municipality.

P.O. Box 999, MS K3-59, Richland, WA 99352

Adhesion Issues with Polymer/Oxide Barrier Coatings on Organic Displays

Multilayer polymer/oxide coatings are being developed to protect sensitive organic display devices, such as OLED's, from oxygen and water vapor permeation. The coatings have permeation levels ~ 10^-6 g,cc/m²/d, and are deposited by vacuum polymer technology (VPT). The coatings consist of either a base Al₂O₃ or acrylate polymer adhesion layer followed by alternating Al₂O₃/polymer layers. The polymer is used to decouple the 300 Å-thick Al₂O₃ barrier layers. Adhesion of the barrier coating to the substrate and display device is critical for the operating lifetime of the device. The substrate material could be PET, PEN, PNB, or XXX. Plasma pretreatment with either Ar or N₂ is also needed for good adhesion to the substrate, but if too aggressive, will damage the organic display device. We report on the effects of plasma treatment on the adhesion of barrier coatings to plastic substrates and the performance of OLED devices after plasma treatment and barrier coating deposition. We find that initial OLED performance in not significantly affected by the VPT process and plasma treatment, as demonstrated by luminosity and I-V curves. Adhesion of the barrier coatings will be related to surface modification of the plastic substrate by formation of new functional groups and destruction of ester and ether groups.

1) Thin Film Physics Lab., Dept of Physics, Rajarshi, Shahu Mahavidyalaya,

Latur - 413512, M.S., INDIA.

2) Thin Film & Solar Studies Research Laboratory, Department of Phsycis (Appl. Elect.), Shivaji University Centre for P.G. Studies, Solapur - Pune Road, Kegaon, Solapur413002, M.S., INDIA.

Optical and Electrical Transport Properties of Chemically Grown Antimony - Cadmium Selenide Thin Film Structures

CdSe : Sb thin films with Sb3+ doping concentration varied from 0 to 5 mol% were obtained onto the amorphous glasses by a chemical bath deposition. The deposits were smooth, well adherent to the substrate support, uniform and diffusely reflecting with colour changing from dark-orange red to yellowish orange as doping concentration was increased from 0 to 5 mol%. The XRD studies revealed polycrystalline nature of the samples. The optical gaps were determined and found to be decreased from 1.79 eV to 1.61 eV for the increase in Sb3+ doping concentration from 0 to 0.1 mol% and further it increased with increase in doping concentration. The transitions in these films were of the band-to-band direct type. The electrical conductivity is found to be enhanced with Sb3+ doping concentration from 0 to 0.1 mol% and then decreased with further addition of antimony content in CdSe. The activation energies were calculated in both the conduction regions. The other material characteristics such as thermoelectric power, carrier concentration (n), mobility (m), barrier height (FB) were studied as a function of working temperature and antimony doping concentration in CdSe.

Contribution of Chemical Interactions Between Different Types of Functional Groups and Metal Atoms to the Adhesion of Metal-polymer Composites

The retention of chemical structure and functional groups during the pulsed plasma polymerisation was used for producing adhesion-promoting plasma polymer layers with high concentrations of exclusively one sort of functional groups such as OH, NH₂, or COOH. The maximum content of functional groups was 31 OH using allyl alcohol, 18 NH₂ using allyl amine, or 24 COOH groups per 100 C atoms using acrylic acid. To vary the density of functional groups a chemical copolymerisation with ethylene as "chain-extending" comonomer or butadiene as "chemical crosslinker" was initiated in the pulsed plasma.

Metal-polymer composites were produced depositing such monotype functional groups-carrying plasma polymers onto PP substrates. Then, the aluminium was evaporated thermally or by electron beam. In general, the measured peel strengths of aluminium deposits increase linearly with the concentration of functional groups. Near the maximum concentration of OH (>27 OH per 100 C atoms) or COOH (>10 COOH per 100 C atoms) constant peel strengths were measured. The failure of peeling the metal layer changed from an interface failure to a cohesive failure within this plateau. In the case of OH group carrying interlayers the peel strength decreases dramatically at maximum OH concentrations (31 OH per 100 C atoms) because of the poor cohesive strength of the adhesion promoting plasma polymer layer. The nature of interactions between aluminium and different functional groups was reflected in the respective peel strengths. The succession of the adhesion-promoting effect was derived from the slope of the linear increase of the peel strengths vs. concentration of functional groups: CH₂-CH₂<NH₂«OH<COOH. The mode of failure, either interface or cohesive, was inspected by microscopy and also by XPS. The results were also compared with those of aluminium-polypropylene composites, which were pretreated by oxygen plasma exposure and (facultative) converting the various oxygen containing functionalities to OH groups by post-plasma chemical reduction with vitride, B₂H₆ or LiAlH₄.

Adhesion Properties of Diamondlike Carbon/Hydroxyapatite Nanocomposites

Studies of orthopaedic implant failures have shown that the mechanical failure of an implant almost exclusively occurs at the biomaterial-tissue interface. Hydroxyapatite (HA) mimics the behavior of natural bone, and provides a strong, long-lasting adhesive interface between a bone replacement implant and the surrounding tissue. Currently, thin film HA is not commonly used because it exhbits poor adhesion, defects, porosity, and cracks. One method to improve the tribological properties of a bioactive coating is to strengthen the microstructure of the coating through the placement of a DLC interlayer. DLC coatings possess properties close to diamond in terms of hardness, atomic smoothness, and chemical inertness. We have developed a diamondlike carbon/HA bilayer, in which the bilayer surface (nano-HA) is bioactive and the interlayer (DLC/metal nanocomposite) is biocompatible, wear resistant, and corrosion resistant. The hydroxyapatite and DLC films were deposited by ablating a hydroxyapatite target and a graphite target using a KrF laser. A novel target design was adopted to incorporate alloying atoms into the films during pulsed laser deposition. These alloying elements possess unique biological properties. These DLC/HA films were studied using scratch adhesion testing, wear testing, nanoindentation, SEM, TEM, STEM-Z, XRD, and Raman spectroscopy. The DLC/nanocrystalline HA bilayer material is potentially useful for several orthopedic implant designs.

A Procedure for Using a Stud-Pull Device for Measuring The Adhesion of Kinetic Spray Coatings on Metals

Research in kinetic spray technology is increasing in many parts of the industrial world. In this paper we explore the means of accurately measuring the adhesion of these coatings on metal substrates using a stud-pull device. Our objective is to determine the limitations of the experimental setup and to establish the appropriate procedures to overcome these limitations.

Three different methods have been examined for measuring the adhesion of kinetic sprayed Cu on aluminum and copper substrates. The first method uses the stud-pull device without a retaining cylinder pushing against the coating. The second method utilizes the retaining cylinder. In the third method the coating is machined using a controlled rotary-disc cutter using a SiC slurry to form a disc-like structure in the coating. These results are compared to tests similar to the ASTM C633 standard for adhesion testing of coated metal substrates.

Excimer Lamp-Induced Photochemical Bonding of Fused Silica Glass and Fluorocarbon Film by Using Organic Silicon Oil for Photochemical Polishing of SiC

Fused silica glass was photo-chemically bonded with Fluorocarbon (FEP) by using silicon oil as adhesives. In this study, the new bonding method of optical materials, which was penetrated UV rays, was developed using silicone oil and UV photon. This new method is needed for the fluorocarbon-polishing pad, which is bonded with the silica glass, employed in our PCP (Photo-Chemical Polishing) method in hydrofluoric acid ambience. Moreover, the nano scale polishing of silicon carbide (SiC) conducted by using the PCP method.

The result shows, transmittance of the silicon oil was measured at the 193 nm of ArF laser wavelength. The transmittance of the silicon oil, which was 29.2 [%, was increased to 71.4 [%] with ArF laser irradiation and 90.6[%] with Xe₂* excimer lamp irradiation. The adhesion strength of the silicon oil without UV photon was nil. That of the treatment sample was obtained 0.353 [kgf/cm²] with laser irradiation and 3.104 [kgf/cm²] with lamp irradiation. It was clarified that Xe₂* excimer lamp was more effectively than ArF excimer laser for bonding of fluorocarbon and fused silica glass. In conclusion, the silicon oil was employed as adhesives because silicon oil was turned to SiO₂ thin layer.

Synthesis of Hexafluoroisopropylidene-Containing Polyimide-Silver Nanocomposite Films Evolving Specularly Reflective Metal Surfaces

(Abstract not yet available)

Role of Chemical Bond in Adhesion of Thin Films Deposited by Plasma Processes

It is well known that the plasma processes such as sputter deposition, ion irradiation and plasma treatment for cleaning substrate, are useful for enhancing adhesion strength of films to glass substrates. In this talk, we present our results that the chemical bonding formed by a plasma plays an important role in the adhesion of films deposited using the plasma processes.

1) Adhesion strength of Ti film sputtered onto glass was enhanced by nitrogen or argon ion irradiation at an acceleration voltage of 10keV. The enhancement of the adhesion was due to Si-Ti bonds formed at the Ti/glass interface by the ion irradiation.

2) Adhesion strength of sputtered carbon film was stronger for plasma treated glass substrates than for non-treated ones. The plasma treatment created broken bonds of Si on the substrate surface and the Si-C bond formed at the film/substrate interface enhanced the adhesion.

3) Adhesion strength at the interface of sputtered titanium nitride (TiN) top layer and metal oxide (MO) under layer increased with decreasing strength of M-O chemical bond in the MO under layer. This was explained in that the surface of the MO under layer was deoxidized and broken bonds of metal and oxygen were created at an onset of the deposition of TiN top layer, and the larger number of interface bonds were generated at the TiN/MO interface for MO under layer with weaker MO bond.

Photochemical Lamination of Transparent SiO₂ Thin Film on PMMA Surface at Room Temperature

A Polymethyl Methacrylate(PMMA) is widely used for plastic lens. It needs antireflection film to make use of the optical characteristic. But it is difficult to laminate the SiO₂ film on the PMMA surface less than 100 . Thus, a transparent SiO₂ film with low refractive index was laminated on the PMMA surface at room temperature by photochemical reactions with the Xe₂ excimer lamp. Therefore, antireflective effect was obtained to PMMA with this film lamination.

The PMMA substrate and the Si wafer were placed in the reaction chamber, which was filled in NF₃ and O₂ gases. The Xe₂ excimer lamp was irradiated into the chamber. The SiO₂ film was grown self-laminated on the PMMA surface by photochemical etching and oxidation. As a result the SiO₂ film thickness was grown to 260nm per an hour, and the refractive index of this film was obtained 1.36.

1) Department of Chemistry, College of William and Mary, Williamsburg, VA 23187

2) NASA Langley Research Center, Mail Stop 227, 6A West Taylor Street, Hampton, VA 23681

Synthesis of Hexafluoroisopropylidene-Containing Polyimide-Silver Nanocomposite Films

Highly reflective surface-metallized flexible polyimide films have been prepared by the incorporation of the soluble silver ion complex (1,1,1-trifluoroacetylacetonato)silver(I) into dimethylacetamide solutions of the poly(amic acid) prepared from 2,2-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride (6FDA) and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoro-propane (4-BDAF).  Thermal curing to 300 °C of solution cast silver(I)-poly(amic acid) films leads to cycloimidization of the amic acid with concomitant silver(I) reduction and formation of a reflective surface-silvered film from 2-13% weight percent silver.  The reflective surfaces evolve only when the cure temperature reaches 300 °C.  After achieving a maximum value the reflectivity abruptly drops with further heating at 300 °C and the polyimide suffers oxidation degradation.  The metallized films are thermally stable and maintain mechanical properties similar to those of the parent polyimide.  TEM reveals that the interior of the composite films have ca. 5-20 nanometer-sized silver particles.  SEM shows surface silver particles time from ca. 50-1000 nm whose size varies with cure time at 300 °C.  Neither the bulk nor the surface of the films is electrically conductive.  There is strong interfacial adhesion of metal to polyimide.  Other metallized polyimide systems will also be discussed.

1) Langley Research Center, National Aeronautics and Space Administration, Hampton, VA;

2) Dept of Chemistry, William and Mary, Williamsburg, VA

Synthesis of HexafluoroisopropylideneContaining PolyimideSilver Nanocomposite Films Evolving Specularly Reflective Metal Surfaces

Surface and bulk silver-metallized polymeric membranes are of interest for solar sail technology, anti-infective medical devices, solar concentrators, thermal blankets, integrated circuitry, gas permeation selective barriers, etc. Here we describe the synthesis of highly reflective flexible polyimide films by a single-stage auto-metallization process involving the {hexafluoroacetylacetonato}- and (trifluoroacetato)silver{I} complex dissolved in solutions of poly(amic acid)s and polyimides which are formed from 2,2-bis{3,4-dicarboxyphenyl}hexafluoropropanedianhydride {6FDA} and 2,2-bis{4-{4-aminophenoxy}hexafluoropropane {4-BDAF}. Thermal curing of cast silver{I}-poly{amic acid} films leads to cycloimidization with concomitant Ag{I} reduction and nano-aggregation giving a reflective film for Ag concentrations from 2-13 weight percent. A 2% Ag film gives specular reflectivies of ca. 80% of vapor deposited Ag. The metallized 6FDA-based films retain the mechanical properties of undoped films and have excellent thermal stability. The bulk of the membrane also contains nanometer-sized Ag particles. TEM and SEM establish that films have surface layers of Ag 30-100 nm thick. In general, films prepared with the silver{I}-hexafluoroacetylacetonate complex are reflective but not conductive, the metallized surface being composed of closely packed nanometer-sized spheres. This is to be contrast with our earlier work with BTDA/ODA that gave both reflective and conductive films. Films prepared from the soluble fully imidized form of 6FDA/4-BDAF rather than from the amic acid were generally less reflective and more irregular in surface morphology than those prepared from the poly{amic acid}. The metallized films were characterized with respect to conductivity, reflectivity, surface morphology, thermal, chemical, and mechanical properties.

Metallized Liquid Crystalline Polymer Reliability

(Abstract not yet avaialble)

HOLDING

Asa H. Barber, Sidney R. Cohen and H. Daniel Wagner; Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel

Measurement of Carbon Nanotube-polymer Interfacial Strength

The force required to separate a carbon nanotube from a solid polymer matrix has been measured by performing reproducible nano-pullout experiments using atomic force microscopy. The separation stress is found to be remarkably high, indicating that carbon nanotubes are effective at reinforcing a polymer. These results imply that the polymer matrix in close vicinity of the carbon nanotube is able to withstand stresses that would otherwise cause considerable yield in a bulk polymer specimen.

1) School of Mechanical and Materials Engineering, University of Surrey, Guildford, Surrey, GU2 7XH, UK

2) School of Engineering, Oxford Brookes University, Gipsy Lane Campus, Headington, Oxford, OX3 0BP, UK

A Finite Element Study on the Effect of Hostile Environment on the Strength of Adhesion

In this paper finite element diffusion and stress analyses of adhesively bonded joints aged in hostile environment are presented. Transient finite element analyses have been first performed in order to determine the moisture distribution in the adhesive layer at different time intervals. The results of these simulations were coupled to non-linear stress finite element analyses in which the constitutive data of the adhesive was defined as a function of moisture concentration. In order to study the stress distribution at different moisture level, four different time intervals have been considered for each joint, namely, 0, 6, 12 weeks and fully saturated condition. The swelling strains have been taken into account in the stress analysis and have been introduced to the adhesive layer according to the moisture distribution at a particular time. Two bonded joints have been considered in this study, namely, single lap joint and butt joint. The joints were immersed in water at 60 C for up to 60 weeks. The FE simulations can explain the experimental results of the effect of moisture on joint strength. Further, FE diffusion simulations have been carried out on various configurations of adhesive resin diffusion discs. It is concluded that the differences in moisture uptake between adhesive and laminated diffusion discs must be due to interfacial moisture transport.

Clear Water Bay, Kowloon, Hong Kong, CHINA

The Role of Plastic Deformation of Rough Surfaces in the Size-Dependent Hardness

In this study, we propose a bearing ratio model for nanoindentation of rough surfaces. During an indentation test, the work done by an applied indentation load contains the bulk work and the surface work. The surface work causes plastic deformation of an indented rough surface and thus dissipates energy, which is necessary to form an impression on a solid. The energy dissipation occurring at the indented surface is among the factors that cause the Indentation Size Effect (ISE) at the micro/nanometer scales. In particular, the surface effect predominates when the indentation depth is shallow. Good agreement is found between the theoretical and experimental results of the size-dependent hardness, indicating that the surface effect plays an important role in size-dependent hardness.