We have synthesized novel diamondlike carbon coatings with silver nanoparticles embedded into the DLC film. The size of silver nanoparticles that are confined into layered structures has been varied from 5 nm to 50 nm using an ingenious pulsed laser deposition technique. The size of nanoparticles was found to be remarkably uniform within 15%. We have characterized these samples using high-resolution cross-section TEM and STEM-Z contrast techniques, electron energy loss spectroscopy (EELS), Raman, nanohardness, adhesion, and biocompatibility measurements. In the STEM-Z, where the contrast is proportional to atomic number2, we have obtained the details of the atomic structure of silver particles. We have correlated the microstructure with hardness and adhesion properties. The EELS was used in conjunction with STEM-Z to obtain sp3/sp2 bonding ratio. This ratio was compared with Raman result to provide an average bulk value. The role of silver nanoparticles is surmised to provide a reservoir of electrons for antimicrobial activity on the surface, as revealed by our biocompatibility tests.

Cubic boron nitride (cBN) thin films were deposited on silicon wafers by low-pressure inductively coupled plasma-enhanced chemical vapor deposition (ICP-CVD). By using special substrate pre-treatment processes including positive biasing treatment in H2 plasma or 1200 K pre-heating in H2 atmosphere followed by an N2 plasma treatment, turbostratic BN (tBN) intermediate layer was revealed to directly grow on Si substrates without an initial amorphous layer. The thickness of the tBN transition layer can be reduced to less than 3 nm.

The possibilities of SILD (successive ionic layer deposition) technology for modification of surface properties of nano-scaled SnO2 films for gas sensor applications were studied and are discussed in this article. Samples of SnO2 with thickness ranging from 30–40 nm were deposited by spray pyrolysis from SnCl4-water solutions. Nano-clusters of Pd and Ag, deposited by the SILD method were applied for surface modification. PdCl2 and AgNO3 were used as precursors for Pd and Ag deposition on the SnO2 surface.

It was found that the method of surface modification by SILD can be used for improving both the sensitivity and the rate of gas response of SnO2-based gas sensors to CO and H2. At the same time, the presence of Pd and Ag clusters on the surface of SnO2 depresses the gas response to ozone.

The frictional behavior of a C60 monolayer film between graphite substrates is studied using a homebuilt surface force apparatus. The mean frictional force from the C60 monolayers is estimated to be approximately 2mN, which is one-fifth that of C60 thin films. The C60 monolayer films exhibit a low frictional force of 2mN up to one hundred scans under a normal stress of 8MPa, which indicates that the C60 monolayer film is highly promising for use as a lubricant. Key words, C60 monolayer film, Lubrication, Mechanical properties, Micromachines

A mechanism is presented for the gas-phase chemistry and surface reactions describing the growth of boron nitride films. The gas phase mechanism includes 33 species and 216 elementary reactions. Rate parameters for 117 elementary reactions were obtained from published experimental/theoretical data and those for the other 99 were determined using transition state theory. The mechanism examined here is an extension and update of a previous mechanism that contained 26 species and 67 elementary reactions. Standard reaction flux/pathway and gradient sensitivity analysis techniques are used to identify important reaction pathways. The calculations were handled through the use of the ChemKin software package. The model was applied to the growth of hexagonal boron nitride in an arcjet plasma source operating on mixture of BF3, H2 and N2. From the growth rate and experimental conditions for such reactors, this work demonstrates that species with mole fractions in the range of 1 × 10-10 − 2 × 10-4 (easily generated by gas-phase conditions) can account for the measured growth rate. A comparison of the predicted mole fractions of the gas-phase species present for the experimental residence times with those required to account for the measured film growth rates allows us to identify possible growth precursors. At the experimental settings, it is found that the residence time of the reacting species does not allow the flow to reach the chemical equilibrium, and that many radicals other than the source gases can account for the measured BN growth rate. The gas-phase is shown to be removed from thermodynamic equilibrium. For comparison, the equilibrium mole fractions were also calculated using an available equilibrium chemistry solver, STANJAN. Growth rates of 10-9 to 10-6 kg m-1 s-1 were measured for a wide range of H2, BF3 and NF3 flux. Both the finite-rate kinetics and equilibrium calculations confirm the importance of added hydrogen to facilitate boron nitride condensation from the gas phase. A simple surface mechanism with 7 steps is proposed with rate constants chosen to best fit the experimental growth kinetics. The results of the model, with surface rate coefficients determined from analogous gas-phase reactions, tuned slightly to agree with the experimental growth rates for BFx, x = 1, 2 or 3, as the rate-limiting growth precursor. It is also shown that the hydrogen atom has a great influence in the growth rate and that fluorine atom etches the hBN films.

Crack formation in hard thin films and the influence of nanostructuring on nucleation and propagation of different crack types were studied using TiAlSiN-based multicomponent nitrides. Thin films of about 2 μm thickness were deposited onto tungsten carbide-cobalt substrates using cathodic arc PVD method. By rotation of samples and changing deposition parameters and chemical composition of target materials, various nanostructured thin films were obtained including: nanocomposite films made of nanocrystallites about 10–30 nm, chemically modulated layers with the bilayer thickness at the range of 10 nm, iso-structured TiAlN/TiAlSiN multilayers with variable bilayer thickness, and finally monolithic single layer with columnar structures of different size. Depth sensing nanoindentation was used to measure hardness and modulus of thin films and to activate several failure modes in order to provide an estimation of the fracture toughness and interfacial fracture energies. Morphology of cracks mainly consist of successive microcracks nucleated at the contact edge periodically under stretching tensile stress upon displacement of indenter. These cracks are almost straight, parallel to each other, regularly distributed at the contact site in fine structure films. They appear discontinuous and irregular in coarse columnar monolithic and in multilyers with larger bilayer periods. The annular cracks appear at greater loads due to tensile peaks caused by bending stresses generated from the substrate depression and coating deflection. These can be accompanied by the interface fracture and delamination. The radial cracks emanating from the corner of indenter appear in high stress films and extend to the neighbouring zones of the contact area. In addition to geometrical cracks, nanoscale cracks frequently appear around the contact area leading to the formation of small discontinuities on the load-displacement curves.

Activation volumes for plastic deformation of fcc metals are measured using nanoindentation. Materials include bulk, polycrystalline aluminum and α-brass, and sputtered copper and nickel thin films on silicon substrates. From a hardness measurement, V* is defined as 9kBT/∂H/∂ln , where H is the hardness and is a representative strain rate beneath the indenter. Data obtained using nanoindentation are consistent with those obtained using more conventional experiments based on uniaxial loading.

We investigate mechanisms of stress corrosion cracking in Si using a hybrid quantum-mechanical/molecular-dynamics simulation code developed recently for parallel computers. We perform the simulation for a cracked Si-model under tension (mode-I opening) with three H2O molecules around the crack front to investigate possible effects of both saturation of dangling bonds of Si with hydrogen atoms and environment molecules on the fracture initiation. Our results demonstrate existence of a path for an H2O molecule to react with Si-Si bonds at the crack front in contrast to a previous theoretical study based on the molecular orbital theory [W. Wong-Ng et al., Comp. Mater. Sci. 6, 63 (1996)].

Pure copper films have been deposited on <100> Si substrates either at the floating potential or biased to various dc voltages ranging from 0 to - 125 V. Argon ions from the discharge produced in a distributed electron cyclotron resonance microwave plasma reactor were used for sputtering of a copper target biased to various dc voltages. For sputter deposition, the Si substrates placed on a water-cooled substrate holder were maintained at ambient temperature. The argon pressure was 0.13 Pa and the dc target voltage was fixed at - 600 V. The deposition rate of films was investigated as a function of the substrate bias voltage. The crystallographic structure of films and size of copper crystallites were determined by x-ray diffraction analyses. The surface morphology of films was examined by atomic force microscopy. The electrical resistivity of films was deduced from the thickness and sheet resistance of films determined by profilometry and four point probe measurements, respectively. The magnitude of residual stresses in copper films was calculated from the radius of curvature of Cu/Si samples deduced from profilometry measurements. The evolution of the microstructure, surface morphology and electrical resistivity of films as well as the magnitude of residual stresses developed in these films were studied as functions of the substrate bias voltage. These major characteristics of films were found to be dependent on the energy of argon ions impinging on the surface of films grown on biased substrates. The effect of the ion energy on the physical features of films is analyzed and discussed in this paper.

This study reports on the microfrictional properties under reciprocating sliding of different types of commercially available diamond-like carbon (DLC) films, prepared using low and high frequency plasma-assisted chemical vapor deposition (PACVD) and the vacuum arc method. Silicon and sapphire balls were used as counterbodies. Friction-load curves suggest that, for applied forces in the N to μN regime, two properties have a strong influence on the microfriction: First, the chemical composition plays a dominant role and second, the film roughness. With silicon against DLC, microfriction of hydrogen-free DLC films was greater than the hydrogen containing films. With sapphire counterbodies, microfriction was inversely proportional to film roughness. For all films tested, microfriction was independent of the sliding velocity. Mild wear in the form of scratches was observed only on silicon, while no wear could be detected on any of the DLC films. These results illustrate the utility of implementing microtribological testing in a coating development for microsystems.

We have used a recently developed x-ray structural microscopy technique to make nondestructive, submicron-resolution measurements of the deformation microstructure below a 100mN maximum load Berkovich nanoindent in single crystal Cu. Direct observations of plastic deformation under the indent were obtained using a ∼0.5 μm polychromatic microbeam and diffracted beam depth profiling to make micron-resolution spatially-resolved x-ray Laue diffraction measurements. The local lattice rotations underneath the nanoindent were found to be heterogeneous in nature as revealed by geometrically necessary dislocation (GND) densities determined for positions along lines beneath a flat indent face and under the sharp Berkovich indent blade edges. Measurements of the local rotation-axes and misorientation-angles along these lines are discussed in terms of crystallographic slip systems.

Carbon nanotubes (CNTs) have been significantly used for the field emitters for display applications. It is necessary to investigate the process variables affecting the screen printing of carbon nanotubes for the fabrication of good-quality field emitter devices with uniformity. Screen printing techniques have some advantages such as the short processing time and lower processing cost. The carbon nanotube pastes for screen printing are normally composed of organic binders, carbon nanotubes, and some additive materials. In this study, the carbon nanotube emitters for field emission displays were fabricated with different processing variables such as paste viscosity, paste composition, screen mesh, etc. The CNT pastes were printed on Cr-coated/Ag-printed soda-lime glass substrates. As a result, the processing variables were optimized for the good screen printing. From the I-V characteristics, the turn-on field of single-walled nanotubes was lower than that of multi-walled nanotubes. The decrease in the mesh number of screen masks resulted in decreasing the turn-on field and increasing the electron emission current due to the higher density and vertical alignment of printed-CNTs.

Diamond films were implanted with Au or O ions at multiple energies in order to produce a uniform region of C vacancies. Analysis of the implanted films by Raman spectroscopy has shown that the proportion of non-diamond or amorphous carbon increased with dose (5 × 1013 − 5 × 1015 ions/cm2). For implantation with Au ions, a complete amorphisation near to the surface was evident at a dose of 5 × 1015 ions/cm2. We have examined the ion beam etch (IBE) rate of the films as a function of the implant species and dose. The etching experiments were performed using either Ar or Ar/O2 gases at a bias energy of 500 -1,000 eV. In Ar gas, the process of sputter etching has produced a similar increase in etch rate with dose for both the Au and O implants. In Ar/ O2 gases, the process of ion-enhanced chemical etching produced greater etch rates than obtained in Ar gas with higher rates for the Au than the O implants.

Guided by recent parametric studies of laser-induced tensile spallation, we successfully developed a new test method for studying mixed-mode interfacial failure of thin films. By allowing an initial longitudinal wave to mode convert at an oblique surface, a high amplitude shear wave is generated in a fused silica substrate and propagated toward the thin film surface. A shear wave was generated with amplitude large enough to fail an Al film/fused silica interface and the corresponding shear stress was calculated from high-speed interferometric displacement measurements. Examination of the interfaces failed under mixed-mode conditions revealed significant wrinkling and tearing of the film, in great contrast to blister patterns observed in similar Al films failed under tensile loading. Slightly higher interfacial strength was measured for the same Al film/fused silica substrate under mixed-mode loading than under tensile loading. The mixed-mode loading experiment developed in the current work provides a new tool to explore a range of thin film interfacial failure modes as well as the role of extrinsic effects such as residual stress, surface roughness, and imperfections.

Deformation behavior of the BN film was dynamically observed by high-resolution transmission electron microscopy. BN thin films were deposited on a narrow edge of Si flakes, using inductively coupled plasma-enhanced chemical vapor deposition. High-resolution observation of the sample revealed that the BN film was possibly deposited on the edge of the Si thinned to less than 10 nm in thickness, whose morphology varied depending on the thickness of the Si edge. Intriguing mechanical properties of the BN films, especially relating their dynamic behavior, were clearly verified by the high-resolution observation with piezo-ceramic tube for three-axis positioning of an indenter.

Hot work tool steel was plasma nitrided in a PVD apparatus. Phases occurring and nitrogen depth profiles were assessed for the nitrided specimens. In all cases bright nitriding was achieved. Increasing the nitriding time from 15 to 120 min yielded a nitriding depth increasing from about 15 to 35 μm, whereas the nitrogen flux decreased from 8.0 to 5.5 × 10-7 kg s-1m-2. Results from an existing model, predicting nitrogen depth profiles due to plasma nitriding, did not accurately describe the experimental data. Therefore the existing model cannot be used straightforwardly to predict the formation of iron nitrides. The discrepancies of model results and experimental results are discussed in view of the assumptions underlying the model for plasma nitriding.

A strong attenuation of surface acoustic waves in the range of 30 to 100 MHz by singlewalled carbon nanotube layers deposited on the surface of piezoelectric lithium niobate single crystal has been observed. The attenuation exhibits non-monotonous dependence on nanotube density. This attenuation is attributed to the acoustoelectronic interaction between electric fields of the SAW and charge carriers in the nanotubes. The experimental results are in the qualitative agreement with the theory of acoustoelectronic interaction in inhomogeneous structures.

Tantalum, a tough refractory metal with excellent corrosion resistance, is an attractive protective coating material for steel subjected to mechanical wear in harsh chemical environments. The coatings deposited by sputtering usually contain a hard and brittle tetragonal phase mixed with the desirable tough and ductile bcc phase of Ta. One of the methods of promoting the growth of the bcc phase at a moderate substrate temperature is deposition of an interfacial or seed layer of tantalum nitride. Ta coatings were deposited by dc magnetron sputtering in argon, and the interfacial nitride layers by reactive sputtering performed in the same chamber with nitrogen gas added to argon. The critical thickness, stoichiometry, and structure of the seed layer required for bcc Ta growth were studied by scanning electron microscopy and X-ray diffraction. The results of adhesion testing of the Ta coatings deposited on the interfacial layers are also reported.

Molybdenum nitride thin film was deposited on silicon wafer with the reactive sputter deposition. γ-Mo2N thin film was obtained with nitrogen content in sputtering gas varying from 10% to 30%. An amorphous structure was observed in the thin film deposited at 50% nitrogen. Crystallinity of Mo-N thin film decreased as the total sputtering gas pressure increased. SEM examinations showed that the surface morphology of Mo-N thin films varies with the nitrogen content in the sputtering gas. The sheet resistivity of as deposited thin film increases with increasing nitrogen content in sputtering gas. The amorphous thin film deposited at 50% nitrogen survived 700°C/5min thermal annealing without obvious crystallization but failed after 800°C/5min thermal annealing, in which the crystalline γ-Mo2N and h-MoSi2 phases were observed. Sheet resistivity measurement showed a decrease in thin film resistivity with increasing thermal annealing temperatures.

Detailed finite-element modeling of nanoindentation data is used to obtain the micromechanical properties of Ni implanted with ∼5 at.% He to a depth of 600–700 nm. Properties of He-containing metals have implications for studies of radiation damage and for fundamental issues of dislocation pinning. Cross-section TEM shows the implantation produces a highly damaged layer containing a fine dispersion of He bubbles with diameters of ∼1 nm or smaller, with some evidence for interconnection between bubbles. Nanoindentation of the Ni(He) layers gave a fairly hard, stiff response to depths of 100–120 nm, beyond which the layer failed. By modeling the layer as an isotropic, elastic-plastic solid with the Mises yield criterion, the Ni(He) is shown to have a hardness nearly 7 times that of untreated Ni. However, unlike other treatments that we have used to produce very hard Ni-based layers, the Ni(He) layer fails at relatively modest shear stress levels.