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Glassy carbon (GC) is usually considered the prototypical super-elastic material, which can almost fully recover its shape after compression of several gigapascals (GPa). In this work, nanoindentation is used to study the mechanical response of GC, which was subjected to a range of high pressures using a diamond anvil cell (DAC). We show that GC starts to lose its elasticity after compression to 6 GPa and becomes clearly mechanically anisotropic after being compressed beyond ∼30 GPa. Molecular dynamics (MD) simulations are used to calculate Young's modulus before and after compression. Through our experimental results and MD simulations, we show that the elasticity of GC is at a minimum around 30 GPa but recovers after compression to higher pressures along the DAC compression axis. [ABSTRACT FROM AUTHOR]

We compare the use of externally applied pulsed and steady magnetic fields for the enhancement of deposition rate in reactive High Power Impulse Magnetron Sputtering (HiPIMS), using the deposition of amorphous hafnium oxide (a-HfO2) on Si as an example. The external magnetic fields were applied by a solenoidal coil, placed above the magnetron target. In the case of a steady magnetic field, a higher voltage was required to initiate the HiPIMS discharge, a longer delay time was observed for current onset, and the films became substoichiometric. For the pulsed magnetic field, film stoichiometry was maintained under all applied external magnetic field strengths. Varying the duration and delay times of the magnetic field after the application of HiPIMS voltage pulse revealed that the afterglow of the plasma between HiPIMS pulses was actively quenched by the presence of the magnetic field. Therefore, the optimum operation with the highest plasma density was obtained by applying the external magnetic field only when the plasma was established and removing it at the end of the HiPIMS pulse. A model to explain the findings is presented in which the target poisoning by oxide formation is determined by the conditions in the afterglow. We describe an approach to achieve maximum deposition rate while maintaining film stoichiometry and high film quality. Amorphous HfO2 films with leakage current through the film of less than 5 × 10-5 A/cm² at 0.1MV/cm were obtained at the maximum deposition rate. The refractive index, at a wavelength of 500nm, of the film prepared with pulsed magnetic field was 2.05 with a very low extinction coefficient of 8 × 10-5. [ABSTRACT FROM AUTHOR]

High-power impulse magnetron sputtering (HiPIMS) is used to deposit amorphous carbon thin films with sp3 fractions of 13% to 82%. Increasing the pulse length results in a transition from conventional HiPIMS deposition to a "mixed-mode" in which an arc triggers on the target surface, resulting in a large flux of carbon ions. The films are characterized using X-ray photoelectron spectroscopy, Raman spectroscopy, ellipsometry, nanoindentation, elastic recoil detection analysis, and measurements of stress and contact angle. All properties vary in a consistent manner, showing a high tetrahedral character only for long pulses, demonstrating that mixed-mode deposition is the source of the high carbon ion flux. Varying the substrate bias reveals an "nergy window" effect, where the sp3 fraction of the films is greatest for a substrate bias around -100V and decreases for higher or lower bias values. In the absence of bias, the films' properties show little dependence on the pulse length, showing that energetic ions are the origin of the highly tetrahedral character. [ABSTRACT FROM AUTHOR]

Using density functional theory and guided by extensive scanning tunneling microscopy (STM) image data, we formulate a detailed mechanism for the dissociation of phosphine (PH3) molecules on the Si(001) surface at room temperature. We distinguish between a main sequence of dissociation that involves PH2+H, PH+2H, and P+3H as observable intermediates, and a secondary sequence that gives rise to PH+H, P+2H, and isolated phosphorus adatoms. The latter sequence arises because PH2 fragments are surprisingly mobile on Si(001) and can diffuse away from the third hydrogen atom that makes up the PH3 stoichiometry. Our calculated activation energies describe the competition between diffusion and dissociation pathways and hence provide a comprehensive model for the numerous adsorbate species observed in STM experiments. [ABSTRACT FROM AUTHOR]

The intrinsic stress of carbon thin films deposited by filtered cathodic arc was investigated as a function of ion energy and Ar background gas pressure. The microstructure of the films was analyzed using transmission electron microscopy, electron energy loss spectroscopy, and Raman spectroscopy. The stress at given substrate bias was reduced by the presence of an Ar background gas and by the presence of a Cu underlayer deposited onto the substrate prior to deposition. Auger electron spectroscopy depth profiles showed no evidence of Ar incorporation into the films. A sharp transition from a sp2 to sp3 rich phase was found to occur at a stress of 6.5±1.5 GPa, independent of the deposition conditions. The structural transition at this value of stress is consistent with available data taken from the literature and also with the expected value of biaxial stress at the phase boundary between graphite and diamond at room temperature. The microstructure of films with stress in the transition region near 6.5 GPa was consistent with a mixture of sp2 and sp3 rich structures. [ABSTRACT FROM AUTHOR]

Ti/C and TiC/C multilayers with periods ranging from 2 to 18 nm were grown by filtered high current pulsed cathodic arc. The growth was monitored in situ by ellipsometry and cantilever stress measurements. The ellipsometry results reveal that the optical properties of the carbon vary as a function of thickness. Correspondingly, the stress in each carbon layer as measured in situ exhibits two well defined values: initially the stress is low and then takes on a higher value for the remainder of the layer. Transmission electron microscopy shows that the initial growth of carbon on Ti or TiC layer is oriented with graphitic basal planes aligned parallel to the interface. After 2–4 nm of growth, the graphitic structure transforms to amorphous carbon. Electron energy loss spectroscopy shows that the carbon layer simultaneously undergoes a transition from sp2 rich to sp3 rich material. [ABSTRACT FROM AUTHOR]

Using first-principles density functional theory, we discuss doping of the Si(001) surface by a single substitutional phosphorus or arsenic atom. We show that there are two competing atomic structures for isolated Si–P and Si–As heterodimers, and that the donor electron is delocalized over the surface. We also show that the Si atom dangling bond of one of these heterodimer structures can be progressively charged by additional electrons. It is predicted that surface charge accumulation as a result of tip-induced band bending leads to structural and electronic changes of the Si–P and Si–As heterodimers which could be observed experimentally. Scanning tunneling microscopy (STM) measurements of the Si–P heterodimer on a n-type Si(001) surface reveal structural characteristics and a bias-voltage dependent appearance, consistent with these predictions. STM measurements for the As:Si(001) system are predicted to exhibit similar behavior to P:Si(001). [ABSTRACT FROM AUTHOR]

The authors report molecular dynamics simulations of alumina (Al2O3) during crystallization from the melt. Using liquid quench methods, they investigate the effect of cooling rate on the structural evolution of the α, κ, and the bixbyite phases. A critical temperature window is identified, where the time spent in this window is crucial in determining the extent to which the systems approach crystallinity. A strong dependence is observed between the final structure and the quench rate, which is most pronounced for the α phase and to lesser extent for the other phases. The results show that the different phases have different tendencies to crystallize that are determined by energetics, complexity of crystal structure, and the number of metastable states. [ABSTRACT FROM AUTHOR]

The structure and magnetic properties of Fe–C films synthesized using dual cathodes and coaxial cathodes in a filtered high current pulsed cathodic vacuum arc were studied. By altering the experimental parameters such as the trigger sequence, period, and pulse length, a series of single and multilayered Fe–C films were deposited. X-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy were utilized to study the composition and microstructure of the films. The magnetic properties were studied using a superconducting quantum interference device magnetometer. The hysteresis loops show that the magnetic properties are controlled by the pattern of the layers and Fe concentration in the films. The reduction in the coercive field when Fe layers are mixed with ta-C layers is a key result and confirms that magnetically soft materials can be created by the multilayer method. The relationship between the magnetic properties and the structure of single and multilayered Fe–C films is discussed. [ABSTRACT FROM AUTHOR]

Al/AlN multilayers with bilayer thicknesses ranging from 10 to 50 nm were fabricated using a filtered cathodic arc deposition system. The effects on the microstructure of using two different deposition rates and applying an 8 kV pulsed voltage (plasma immersion ion implantation or PIII) to the substrate were explored. The microstructure was found to undergo a transition in which the Al transformed from layers to an aggregated phase under some conditions. This behavior is explained by a model in which the aggregation process is limited by diffusion. High deposition rates and the application of PIII were both found to encourage the transition by increasing diffusion. The model defines a phase diagram which predicts whether a multilayer or an aggregated structure will occur. A maximum in intrinsic stress was found to occur when the average feature size was 15 nm for both layers and aggregates. [ABSTRACT FROM AUTHOR]

The early stages of the expansion of fully ionized cathode spot cathodic arc plasmas from a localized initial volume are simulated by an all particle molecular dynamics model. The particles are given an initial temperature and interact by Coulomb forces. Although there are limits on the number of particles and the starting density, the model is relevant in describing processes occurring in cells that are the smallest structures of a cathodic arc. Our model predicts that a cell undergoes an explosive expansion leading to a halo of electrons surrounding an ion-rich core. The ion kinetic energies are lower than experimental observation but may be consistent with them after extrapolation to higher initial densities. For mixed charge state plasmas, the ion kinetic energy increases with ion charge state. [ABSTRACT FROM AUTHOR]

We examine the effect of ion impact energy on the intrinsic stress and microstructure of aluminum nitride thin films deposited using a filtered cathodic arc. The dependence of intrinsic stress on ion impact energy is studied over the range from 0 to 350 V using dc bias and up to several kV for a fraction of the ions using pulse bias. For dc bias, the stress reaches a maximum at 200 V and decreases with further increase in ion bias. The preferred orientation of the crystallites was studied by cross-section transmission electron microscopy and diffraction. We found that there is a preference for the c crystallographic axis to lie in the plane of the film under high intrinsic stress conditions (4 GPa), whereas a c-axis orientation perpendicular to the plane of the film was observed for low intrinsic stress (0.25 GPa). We carried out calculations of the expected distribution of intensity in cross-sectional electron diffraction patterns to predict the effect of rotation freedom of crystallites with the c axis pinned. The calculated patterns agreed well with experiment. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Polycrystalline and microcrystalline materials grown as thin films often exhibit a preferred crystallographic orientation. The mechanism by which this preferred orientation develops has been the subject of some debate. In this article we present the results of electron microscopy and diffraction experiments examining preferred orientation in titanium-nitride (TiN) films deposited by physical vapor deposition with bombardment energies up to 18 keV using plasma immersion ion implantation. We show that as the bombardment energy increases the intrinsic stress is reduced. For example, at 3 kV more than a 50% reduction in stress is achieved. The results are consistent with a model in which the preferred orientation is the result of minimizing the energy, which includes both surface energy and bulk strain energy terms. [ABSTRACT FROM AUTHOR]

Discusses findings of an ab initio study of structure in boron nitride, aluminum nitride and mixed aluminum boron nitride amorphous alloys. Structural and elastic properties; Use of first principles quantum mechanical molecular dynamics; Use of density functional theory to calculate interatomic forces.

Reports that thin tungsten nitride films were produced by reactive dc magnetron sputtering of tungsten in an Ar-N2 gas mixture. Effects of the variation of nitrogen partial pressure on the composition, residual stress and structural properties of the thin films; Analysis of the films in situ by a cantilever beam technique.

When plasma immersion ion implantation is performed in the condensable plasma stream produced by a cathodic vacuum arc, deposition as well as implantation usually occurs. In this article we describe a method of achieving pure implantation by orienting the substrate so that it is shadowed from the plasma beam. Implantation depth profiles measured in glassy carbon and CR39 polymer using Rutherford backscattering are compared to illustrate the effectiveness of the technique for conducting and insulating substrates. Charging of the insulating substrate was found to cause a reduction in implantation depth compared to a conducting substrate. The depth profiles in glassy carbon were comparable to those achieved by conventional extracted ion beam implantation. Implantation of magnesium into hydroxyapatite and alumina was carried out to improve the bone cell adhesion onto these materials for prosthetic applications. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents a study which examined the properties of titanium nitride films deposited at low temperature in a plasma-based chemical vapor deposition system. Application of stoichiometry in deposition techniques; Advantages of the configuration; Optical properties of the thin films.

Presents information on a study that investigated the optical and structural SiO[sub2] films as a function of the energy of the ion bombardment applied during plasma-enhanced chemical-vapor deposition. Experimental procedure; Results and discussion on the study; Conclusions.