Mechanical properties of thin films differ significantly from those of bulk materials due to the effects of interfaces, microstructure and thick underlying substrates. In this study we will present the results of nanoindentation tests to evaluate mechanical properties of nitride (TiN, ZrN, CrN, TiCN and TiAlN) thin films. Films were coated on steel substrates using cathodic arc deposition technique. Surface morphology and roughness of the samples are investigated using atomic force microscopy (AFM). Films were also characterized by x-ray diffraction (XRD) technique. Nanoindentation technique along with AFM and XRD methods are very useful for characterizing hard thin coatings.

The long-term oxidation behavior on a Ti-2Al-2.5Zr alloy with and without pre-oxidation oxidized at 300 in an alkaline steam for about 13000h were studied. Some of the samples were subjected to 400°C deionized water steam at a pressure of 10MPa for 72 hours for pre-oxidation. A comparison study has been carried out between the pre-oxidized and without pre-oxidized Ti-2Al-2.5Zr to determine the influence of pre-oxidation upon the properties of oxidation resistance. The result analysis showed that the oxide scales on the Ti-2Al-2.5Zr alloy consisted of Al2TiO5, TiO2, Ti3O5, Ti2O3, Al2O3 and TiO. The oxidation kinetics showed that the weight gains of the pre-oxidized samples were much less than that of the without pre-oxidized samples. The AES results showed that the whole thickness of the pre-oxidized sample thinner than that of the without pre-oxidized one, in contrast the pattern for the stable oxide scale was reversed, i.e. the pre-oxidized sample was much thicker. It is thought that pre-oxidation is an effective method to enhance the oxidation resistance of Ti-2Al-2.5Zr.

TiC/C/Ag coatings were deposited by magnetron sputtering pulsed laser deposition (MSPLD) combining sputtering from a custom made Ti-Ag (60:40) target with the ablation of carbon. Energy disperse spectroscopy (EDS) was used to determine the elemental composition, and x-ray diffraction (XRD) and cross-sectional scanning electron microscopy (XSEM) to examine the structure of the films. Hardness and reduced modulus measurements were acquired using a nanoindentation technique. The pin-on-disk friction test was used to study the friction behavior of the deposited samples in high vacuum and ambient conditions. Variations in the laser energy and the power of the sputtering gun yielded a set of samples with carbon content that ranged from 15.0 to 95.6 percent. The hardest samples with the highest reduced modulus were those with a moderate carbon content and that were shown to form a titanium carbide phase. Tribological results indicated that there is an optimum composition of a TiC/C/Ag coating (~25 at.% carbon) for which it can be reversible and provide lubrication in both ambient and vacuum.

The item of the paper is focussed on some bio-compatible coatings for rare earth based permanent magnets, which are used as dental materials for prosthetic devices as retention units. The studied alloy belongs to Nd-Fe-B system with some Dy and Al content. The double-layer coatings had different chemical compositions; first layer: Ag30-Cr70, Co30-Cr70, Stainless Steel and the second layer: titanium nitride (TiN). Data about corrosion behavior, wear resistance and adhesion are presented. The corrosion resistance of these coatings was tested in artificial saliva, using electrochemical potentiostatic and potentiodynamic polarization techniques. The stability in the corrosion media, the localized corrosion susceptibility and the corrosion rates were determined. It resulted that the Nd30-Dy5-Fe-Al0.4-B alloy with Ag30-Cr70 + TiN film is very stable in artificial saliva. The wear behavior of the coatings in different conditions of contact and load was tested, also. The adhesion was determined by scratching test.

Silicon carbide (SiC) films have been successfully deposited on various substrates by oligomer thermal chemical vapor deposition (OTCVD) from a novel, halogen free, oligomer precursor family of polysilyenemethylenes (PSMs) called SP-4000. The high quality films were grown at substrate temperatures in the range of 620°C to 850°C and at process pressures in the range of 1 - 200Torr. SP-4000 is a silicon carbide precursor with formula [-SiH2-CH2-]n, n=2-8, composed of an alternating silicon and carbon backbone with hydrogen side groups. Depositions on Si and graphite substrates yielded SiC films with Si/C ratios in the range 1.1 to 1.2 and thicknesses in the range 0.3 to 50μm.

Structural and chemical characterizations were performed by Auger electron spectroscopy (AES), x-ray diffraction (XRD), nuclear reaction analysis (NRA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM).

The SiC coatings deposited at substrate temperatures below 1100°C were found to be amorphous. Ex-situ, post deposition annealing in inert gas ambient above 1100°C converted the SiC films to a polycrystalline phase.

Magnetron sputtering has been used to deposit metal-containing, diamond-like-carbon (Me-DLC) coatings onto substrates composed of AISI 52100 steel in quenched-and-tempered condition. Coatings of two distinctly different compositions, one containing Was the metallic constituent and the second containing Cr, have been deposited in a plasma containing Ar and C2H2.Interrupted, unidirectional sliding experiments of the block-on-ring type have been conducted in a poly-alpha-olefin (PAO) lubricant at a load of 667 N for discrete numbers of cycles, N, of between 10 and 1000. Focused-ion-beam, scanning electron microscopy (FIB/SEM) has been applied to characterize the morphology of as-deposited and worn Me-DLC coatings. This technique has resulted in the determination that the Cr-DLC coating, deposited using the investigated processing parameters, fractures in a brittle manner through the formation and propagation of “tunnel cracks,” which unzip in a direction parallel to the grinding direction outside of the region of contact. Conversely, the application of specific processing parameters to deposit W-DLC produces a coating that wears by gradual recession, consistent with polishing wear. First-principles-based analysis shows that the state of residual stress is critically important in the behavior of the coating.

We report on the fabrication, characterization, and processing of boron nitride films for use in high temperature applications such as field passivation, capping layers for thermal annealing of SiC, and protecting metallic filaments from their working environments. The BN films have been fabricated by pulsed laser deposition and spray techniques. The deposited films were characterized by X-ray Diffraction, Fourier Transform Infrared Spectroscopy, Ultraviolet-Visible Spectroscopy, Rutherford Backscattering Spectrometry and Transmission Electron Microscopy. The BN films deposited in the temperature range of 200-500°C have been found to be poorly crystalline, whereas the films fabricated above 600°C have been found to be microcrystalline. The as-deposited films were annealed at various temperatures ranging from 900°C to 1700°C in order to densify the films and study the applicability of the coatings. An AlN buffer layer was also applied in a few cases to improve chemical bonding with the substrate. Adhesion of the films with the heater components was greatly improved for high temperature annealed samples due to good interfacial bonding with the substrate material. Our results on the properties of BN films with an emphasis on characterization, processing, and implications for high temperature applications are discussed.

To study structural and transport properties of the surface phases on silicon, a number of adsorbate/silicon systems on Si(100) and Si(111) surfaces has been investigated using scanning tunneling microscopy (STM), reflection-high-energy-electron diffraction (RHEED) and in-situ electrical resistance measurements. Results of investigations of formation and electrical properties of Si-Al, Si-Na, Si-Ag and Si-In surface structure are presented.

We investigated the deposition, structure and mechanical properties of a-C:H films grown in Ar-CH4 mixtures with the Ar partial pressure ranging from 0 to 99 %. The deposition rate strongly decreased with progressive Ar dilution of the CH4 atmosphere. Films deposited in pure CH4 atmospheres have a hydrogen content of 20 at.% that showed a trend to decrease for lower CH4 partial pressures, while the density remained nearly constant at around 1.4x1023 at./cm3. Raman spectroscopy and x-ray diffraction revealed the amorphous character of the films. The compressive internal stress remained constant around 2.5 GPa and the hardness decreases for Ar rich precursor atmospheres.

TiSiN films grown by chemical vapor deposition were characterized to evaluate the properties relevant to the application as a diffusion barrier in Cu-based interconnects. The films were grown using TiI4 + SiI4 + NH3 + H2 chemistry at substrate temperature, 370°C, and SiI4 - to-TiI4 precursor flow rate ratio of 30. The combined results from x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) revealed that the bulk of Ti32Si21N42 films were predominantly consisted of a mixture of cubic TiN and amorphous SiNx phases. The specific electrical resistivity of the films was about 2000 μΩcm which is a few times higher than that of sputtered TiSiN films having similar composition and thicknesses. The 40 nm-thick barrier appeared to be thermally stable against Cu diffusion at the annealing temperatures up to 550°C. Breakdown of this diffusion barrier occurred at 600°C and was accompanied by the formation of Cu3Si protrusions at the TiSiN/Si interface.

Pulsed laser deposition is a unique technique for the deposition of a wide variety of thin films. These films include magnetic and optical films, novel semiconductors, high temperature superconductors, and diamond-like carbon films. Amorphous Carbon material is evaporated from a solid target and ionized by a high-energy KrF laser and ejected as a plasma plume. The plume expands outwards and deposits the target material on a silicon substrate. Plasma and flow parameters in this plume determine the quality of the film deposited on the substrate. In these experiments, a quadruple Langmuir probe is used to determine various plasma properties in the plume as a function of laser energy density on target, laser spot size on the target and probe position from target. These properties include electron temperature, ion flow speed, ion kinetic energy, plume peaking parameter, and ion density. Film analysis was conducted by electron energy loss spectroscopy (EELS) indicating that DLC films have been successfully deposited with an sp3 concentration as exceeding 72%.

Initial nucleation of Al in chemical vapor deposition (CVD) using dimethyl-aluminum- hydride was observed in order to obtain a principle for enhancing the nucleation density. The analysis employed in situ surface reflectivity measurement combined with X-ray photoelectron spectroscopy and scanning electron microscopy at the typical stage of reflectivity behavior. During the incubation period between the injection of DMAH and the nucleation of Al, a constant amount of Al existed on the surface while no nuclei was observed. The precursor of the nuclei seemed not DMAH itself but the reaction product of the adsorbed DMAH. The activation energy for reciprocal of the incubation period, which may be an index of the reaction rate of the adsorbed layer, is slightly larger than for the continuous growth of Al.

Peel test methods are assessed through being applied to a peeling analysis of the ductile film/ceramic substrate system. Through computing the fracture work of the system using the either beam bend model (BB model) or the general plane analysis model (GPA model), surprisingly, a big difference between both model results is found. Although the BB model can capture the plastic dissipation phenomenon for the ductile film case as the GPA model can, it is much sensitive to the choice of the peeling criterion parameters, and it overestimates the plastic bending effect unable to capture crack tip constraint plasticity. In view of the difficulty of measuring interfacial toughness using peel test method when film is the ductile material, a new test method, split test, is recommended and analyzed using the GPA model. The prediction is applied to a wedge-loaded experiment for Al-alloy double-cantilever beam in literature.

The mechanical properties of silicon crystals are important from the viewpoint of wafer and device fabrication processes. It is now widely recognized that silicon undergoes a series of phase transformations when subjected to high pressures, using conventional high pressure devices, such as diamond anvils or hydrostatic pressure cells, or under indentation. Scratching on a silicon surface in the various conditions introduces various kinds of mechanical damage and stressed states. Micro-Raman spectroscopy was used to observe the phase transition of single crystal silicon. Several different phases were observed depending on scratching speed and scratched locations.

The unusual constitutive behavior of NiTi alloys that display shape memory and transformational superelasticity may impart useful tribological properties. This paper presents some preliminary results on nanoindentation and pin-on-disk wear experiments that suggest potential tri-bological applications of NiTi alloys. It is shown that high levels of spring-back reversibility together with high hardness, as measured by nanoindentation experiments, correlate with improved wear resistance in bulk Nitinol alloys. Amorphous thin films of equiatomic NiTi, which are readily produced by physical vapor deposition, were found to be especially hard and wear resistant. Finally, stress induced B2-B19' transformation is shown to occur during wear-loading of martensitic NiTi, indicating that wear processes are capable of inducing superelastic effects in B2 NiTi alloys.

Using intense pulsed ion-beam evaporation technique, we have succeeded in the preparation of polycrystalline silicon thin films on silicon substrate without impurities. Good crystallinity and high deposition rate have been achieved without heating the substrate. The crystallinity of poly-Si film has been improved with increasing the density of the ablation plasma. The intense diffraction peaks of poly-Si thin films can be obtained by using the substrate bias system. The crystallinity and the deposition rate of poly-Si thin films are increased by negative bias voltage for the substrate.

2-μm thick structural films of polycrystalline silicon are shown to display “metal-like” stress-life fatigue behavior in room air, with failures occurring after > 1011 cycles at stresses as low as half the fracture strength. Using in situ measurements of the specimen compliance and transmission electron microscopy to characterize such damage, the mechanism of thin-film silicon fatigue is deduced to be sequential oxidation and moisture-assisted cracking in the native SiO2 layer. This mechanism can also occur in bulk silicon but it is only relevant in thin films where the critical crack size for catastrophic failure can be exceeded within the oxide layer. The fatigue susceptibility of thin-film silicon is shown to be suppressed by alkene-based self-assembled monolayer coatings that prevent the formation of the native oxide.

The purpose of this paper is to investigate the piston temperature and stress distribution resulting from varying coating thicknesses of Partially Stabilized Zirconia (PSZ) thermal barrier coatings for the performance in diesel engine applications. This analysis is based on the premise that coating thickness affects the heat transfer and temperature distribution in the piston. A gas dynamic engine cycle simulation code was used to obtain thermal boundary conditions on the piston then, a 2-D axisymmetric Finite Element Analysis (FEA) using ANSYS was performed to evaluate the temperature and stress distributions in the piston as a function of coating thickness. Coating thicknesses studied include 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, and 2.0mm. The results indicate increased piston surface temperature with increasing coating thickness. The maximum stress on the coated piston surface was high while the substrate stress was less than the coating yield stress for all coating thicknesses. Further, the analysis showed that the interface stress at all coated conditions is low enough such that no separation of the coating is expected. The FEA results suggest an optimum coating thickness of 0.1 to 1.5 mm for diesel engine application to avoid unduly high stress in the ceramic.

ZrO2 films were investigated as high-k gate insulators for possible gate dielectric applications. These thin films were deposited by chemical vapor deposition (CVD). We had investigated kinetics of ZrO2-CVD reaction system and thermal stability of ZrO2 film deposited from zirconium-tetra-tertiary-butoxide (ZTB) and tetrakis-diethylamio-zirconium (TDEAZ) as Zr source. In the case of ZTB, ZTB decomposed into two active intermediate precursors by gas phase reaction. These intermediate precursors also contributed to the film growth. The step coverage, the contents of carbon and oxygen, and film structures depended on the growth precursor contributed to the film growth. Film structures also depended on the deposition temperature. As the films subjected to the rapid thermal oxidation annealing, the film structure changed amorphous into cubic and then into monoclinic. However, in the case of the films deposited at 300°C, the film structure kept amorphous state after 900°C annealing. On the other hand, in the case of TDEAZ, TDEAZ directly deposited on the growing surface and the decomposition of TDEAZ by gas phase reaction did not exist. The films deposited by TDEAZ contained more carbon than by ZTB. The film structure kept amorphous state independent of the deposition temperature. As the films subjected to the rapid thermal oxidation annealing, the film structure changed amorphous into monoclinic and then into amorphous again. This structural change resulted from the decrease of the impurity contents of the residual nitrogen and the residual carbon and the increase of the content of silicon diffused from the substrate in the ZrO2 films.

Recently, we have investigated the electrostatic layer-by-layer (ELBL) deposition of polycation and clay platelet ultrathin films. We have investigated the properties of these films using techniques such as ellipsometry, X-ray diffraction and atomic force microscopy (AFM). In this work, we report our results regarding the formation of this type of hybrid ultrathin films focusing on their mechanical properties as probed by nanoindentation experiments. Structural information such as film thickness, platelet coverage, surface morphology, roughness, etc., is important parameters for their potential use as coatings. We have investigated the relationship of several of these parameters with their mechanical hardness and modulus properties as a function of indentor probe depth in nanoindentation experiments. The ultrathin films have remarkable mechanical properties very different from most polymer ultrathin films.