Ultra-high molecular weight polyethylene (UHMW-PE) has a highly chain-extended and crystalline structure which is functionally inert and requires surface-modification before it can successfully operate as a reinforcement in polymer-matrix composites. Although plasma treatments are adequate for this purpose, recent work has shown that irradiation with low-energy inert gas ions can produce increases in interfacial shear strength (ISS), in epoxy matrices, which exceed those of commercial plasma treatments, and cause little degradation in tensile properties. Low energy ions are readily produced in high-current beams using gridded sources having moderate cost, and processing times may be a short as a few seconds. In this paper, we present results of recent experiments using argon ions accelerated to energies between 100 eV and 1 keV to irradiate 20–30 μm diameter UHMW-PE fibers to doses between 1×1016 and 1×1017 cm−2, and compare our findings with previous work at higher accelerating potentials. At the optimum dose (which increases with decreasing energy), greater than 9-fold improvements in ISS level, measured in epoxy-resin droplet pulloff tests, were found for ion irradiation at 0.25 keV. Scanning electron microscopy of fiber surfaces, of ion irradiated as well as commercial oxygen plasma-treated materials, revealed small crack-like pits in both cases, with the pits smaller and more uniformly distributed on the ion-irradiated fibers. Surface chemistry studies using X-ray photoelec-tron spectroscopy (XPS) and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) indicate that irradiation resulted in high surface concentrations of polar functional groups, and extensive surface oxidation. This was accompanied by a substantial increase in the polar component of surface energy, which resulted in improved fiber wetting by the resin.

Thin films of SiO2 were deposited on Si substrates by remote PECVD following an in-situ cleaning/surface passivation with atomic-H. Si-N bonds were found in the immediate vicinity of the SiO2/Si interface when nitrous oxide, N2O, was used as O-atom source gas in the remote PECVD process. Si-N bonds, as well as Si-surface roughening produced by H-atom etching, contribute to the formation of high densities of midgap trapping states, Dit ∼1011 cm−2 eV−1, at the SiO2/Si interface. Eliminating the H-atom processing step, and exposing the Si surface to plasma-generated O-atoms prior to the SiO2 deposition: i) eliminated Si-N bonding at the Si/SiO2 interface; ii) reduced midgap Dit to ∼ 1–3×1010 cm−2eV−1 iii) eliminated surface roughening; and iv) improved process latitude and reproducibility.

Silicon epitaxial growth on silicon wafers were investigated by using plasma enhanced chemical vapor deposition from SiH4/He/H2. The epitaxial layers were growm at temperatures of 350°C or lower. The base pressure of the chamber was greater than 2 × 10−5 Torr. Prior to epitaxial growth, the wafer was in-situ cleaned by H2 baking for 30 min. The epi/substrate interface and epitaxial layers were observed by cross-sectional transmission electron microscopy (XTEM). Finally, the influence of the ex-situ and in-situ cleaning processes on the qualities of the interface and epitaxial layers was discussed in detail.

Remote Plasma-enhanced Chemical Vapor Deposition (RPCVD) has been used to grow GexSi1−x/Si heteroepitaxial thin films at low temperatures (∼450°C). In situ RHEED has been used to confirm that smooth, single crystal heteroepitaxial films can be grown by RPCVD. Plan-view and cross-sectional TEM have been employed to study the microstructure of the heteroepitaxial films. Lattice imaging high resolution TEM (HRTEM) has shown perfect epitaxial lattice alignment at the heterojunction interfaces. GexSi1−x/Si films which exceed their CLT's appreciably show dense Moiré fringes under plan-view TEM. The spacings between the fringes have been used to estimate the relaxed lattice constants. In addition to the inhomogeneous strain observed in-XTEM, Selected Area electron Diffraction (SAD) analysis of the interfaces displays two split patterns. The spacings between the diffraction spots have been used to calculate the lattice constants in the epitaxial films in different crystal directions, which agree very well with the prediction by Vegard's law as well as the estimate from plan-view TEM analysis. HRTEM analysis also reveals the crystallographic nature of the interfacial misfit dislocations in the relaxed films.

Angular-resolved time-of-flight (ARTOF) studies have been performed on ablation plumes of copper generated by excimer laser fluences just above threshold in vacuum. Positive ions, Rydberg atoms and ground-state neutrals are observed. Relative concentrations, angular intensity distributions and angular-resolved velocity distributions are measured for ground state neutrals and ions.

Ions have the highest kinetic energies ( 20–80 eV). Their angular distribution is isotropic. Their concentration at the substrate is very low ( ≤ 10−6). Ground state neutrals have lower energies ( ≈ 1 eV). Their intensity and velocity is a strongly decreasing function of the polar angle. Rydberg-atoms have energies in between those of ground-state neutrals and ions. Their angular distribution is also dependent on the polar angle.

The concentration, kinetic energy and angular distribution of the ionised species arc very well explained by a mechanism of thermal ionization and subsequent space-charge induced repulsion. The velocity distributions and angular intensity distributions of the ground-state neutrals are quantitatively predicted by a model for the flow dynamics of pulsed laser generated gas clouds.

Speed distributions were determined for the ions, ground state and electronically-excited neutrals ejected from a graphite target by 248 nm laser ablation. Mass distributions were measured for the laser-ejected ions. The measurements were carried out normal to the graphite target as well as at an angle of 45°. Significant differences were observed in both the speed and mass distributions at the two angles.

In the paper the results of a theoretical investigation of the growth process of laser-plasma deposited thin films are discussed. A kinetic approach has been used to establish direct relation between experimental conditions (laser flux density, substrate temperature) and film properties (thickness, structure). The results of some experimental investigations of the deposition process are presented confirming the general conclusions of the developed theoretical model.

Ellipsometry is normally used to characterize layered structures that have uniform properties laterally across the area of the probe beam. In this study, pulsed laser deposition of ZnO films was found to have highly nonuniform growth properties in the lateral directions. We were able to account for the effects of the nonuniform growth on in-situ ellipsometric data, by considering two dynamic growth models.

Systematic experiments have been carried out to characterize the yttria containing zirconia thin films on sapphire substrates by 248nm KrF excimer laser ablation. The deposition rate as a function of laser fluence and O2 pressure at room temperature was measured with a quartz crystal microbalance. The results show different threshold fluences for deposition in vacuum vs. oxygen. While the deposition rate increases with increasing fluence at a given oxygen pressure, the rate eventually saturates at a higher laser fluence. At a given fluence, the oxygen pressure dependence of the deposition rate shows a radical reduction when the O2 pressure increases from 10 mTorr to 1 Torr. Rutherford backscattering spectrometry (RBS) and x-ray photoelectron spectroscopy were used to obtain stoichiometric information. A very strong pressure dependence of the O/Zr ratio was observed. While the trend of increasing O/Zr and Zr/Y ratio with increasing O2 pressure is apparent, the correlations between O/Zr as well as Zr/Y ratio and other processing conditions are less obvious. RBS results indicate an increasing roughness at the interface between the ZrO2 film and the sapphire substrate as the oxygen pressure exceeds 50 mTorr. The structural information obtained from x-ray diffraction patterns indicates broadening of peak width with increasing laser fluence as well as decreasing substrate temperature. For the film deposited at a lower substrate temperature, a strong (002) texture was observed.

Lead monoxide (PbO) is a potential solid lubricant for use at elevated temperatures in oxidizing environments. The objective of this research was to grow thin films of PbO by Pulsed Laser Deposition (PLD). Film stoichiometry, crystallinity, and chemistry were adjusted by varying substrate temperature and O2 partial pressure during deposition and the effects of changes in film properties on friction coefficients and wear lives were investigated. Chemistry and crystallinity were evaluated using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and glancing angle X-ray diffraction (XRD). Friction coefficients and wear lives were measured in dry nitrogen and at room temperature using a ball-on-flat tribometer. Films deposited at room temperature retained the crystal structure of the target material, but were oxygen deficient. The O/Pb ratio was increased by raising the O2 partial pressure and by increasing the substrate temperature during deposition; the crystal structure and orientation changed with stoichiometry. Friction coefficients ranged from 0.20 – 0.45 and the wear lives were typically less than those obtained from MoS2 films.

High temperature superconducting Y1Ba2Cu3O7−x(YBCO) thin films have been grown on GaAs substrates by in situ laser deposition with a double buffer layer of yttrium-stabilized ZrO2(YSZ)/Si3N4. A barrier layer using a combination of YSZ/Si3N4 was used to grow high quality YBCO thin films without the degradation of the GaAs during YBCO film deposition. Strongly c-axis oriented superconducting YBCO thin films with a zero resistance temperature of 85.5 K and a critical current density of 1.9×103 A/cm2 at 77 K have been obtained. The electrical properties of the YBCO thin films were mainly dependent on YSZ buffer layer deposition condition.

We have measured the complex dielectric function of BizSr2Ca1Cu2Ox samples in the near infrared region directly by spectroellipsometry. As for both single crystal and thin film, superconducting samples have a zero point in the real part (ε1) of the complex dielectric function (ε*) and a clear peak of the imaginary part of the inverse ε* at almost the same frequency. On the other hand, non-superconducting samples have no such ei zero point, and the peak height of (-Im(1/ε*)) becomes small. Then we can determine the superconductivity of samples by this spectroellipsometry measurement at room temperature.

Pulsed Laser Deposition (PLD) has been proven as an effective means of depositing films from refractory targets. In our earlier work, either Nd/YAG or excimer lasers, interacting directly with target surfaces, were used to deposit thin films of high Tc superconductors, high dielectric constant BaTiO3 and ferroelectric PbZr0.53Ti0.47Os3 (PZT). Time-resolved molecular beam mass spectrometry and optical emission spectroscopic techniques have been developed to characterize the vapor plumes responsible for film formation. More recently, this work has been extended to the PLD of magnetic thin films of Ag-Fe3O4 nanocomposites using excimer (ArF*, 193 nm) laser excitation. Optical emission spectra of the excited vapor phase species, formed during the plume generation and material deposition process, indicate that physically compressed powdered metal targets have inadequate homogeneity for film production, compared to targets that are chemically produced. An in situ Laser-induced Vaporization Mass Spectrometry (LVMS) technique utilizing a Nd/YAG (1064 nm) laser has been used to determine Time-of-Arrival (TOA) profiles of the atomic, molecular, and ionic species produced in the plumes of Ag-Fe3O4 The neutral species TOA profiles indicate velocity distributions that are multimodal and not Maxwellian. These observations are in contrast to the TOA profiles observed from one-component targets (Ag or Fe3O4), where a single Maxwellian velocity distribution is found. Mossbauer effect measurements of the thin films have been made for correlation with the gas phase studies.

Thin films of titanium carbide (TiC) and boron carbide (B4C) were grown by excimer pulsed laser deposition (PLD) at room temperature (RT) and 300°C. Films were deposited using the output of an excimer laser operating with KrF gas (γ = 248 nm, 15 ns pulse duration) to ablate hot-pressed targets. Film chemistry, morphology, and crystallinity were investigated. Stoichiometric, crystalline TiC films were grown on 440C stainless steel and NaCl substrates at room temperature and at 300°C. The films grown on NaCl were nanocrystalline, cubic TiC, with a grain size ranging between 2 and 10 nm in diameter. Boron carbide films were grown on silicon {100} substrates at room temperature and at 300°C. Film chemistry and stoichiometry duplicated that of the B4C target, which contained B4C and a mixed C-B-O-N binder phase. SEM analysis indicated that the morphology of the films was uniform, non-porous, and fine-grained. The films exhibited good adhesion and wear resistance, based on friction and wear data collected with a ball-on-disc tribometer.

Thin films have been grown on Si (100) substrates by pulsed laser evaporation of graphite using both IR and UV radiation. The character of the resulting film is found to be independent of the presence of H°. Diamond-like films are found to be a result of low (RT) temperature deposition of the higher energy incident particles of the UV (versus IR) laser ablation process.

A new UHV system for pulsed laser deposition of materials is described, together with results from preliminary experiments for depositions of BN on Si. The system is designed to allow for in-situ diagnostics of the ablation plasma, as well as UHV preparation and characterization of clean sample substrates. The room temperature depositions of BN result in amorphous, B-rich films, whose particle content is a strong function of laser wavelength.

A series of experiments have been conducted which probe the origin of the polyatomic ions (e.g., Sr2O+, BiCu+) measured following the low fluence, pulsed UV laser irradiation of crystalline Bi2Sr2CaCu2O8 (BiSrCaCuO). The photoejection of polyatomic species presents a problem for the pulsed laser deposition (PLD) technique. The deposition of polyatomic products could limit epitaxial growth during thin film material processing. Our results indicate that the polyatomic species are not the consequence of a gas phase recombination, but are in fact directly produced. All experiments are done at laser fluences below that required for above surface plasma formation. As such, our results do not address the formation of large clusters within the dense plume in high fluence laser ablation.

A systematic study of the surface morphology and chemical composition of several ceramic targets after pulsed laser ablation has been conducted using a scanning electron microscope with x-ray energy dispersive spectroscopy. We have examined single crystal LaAlO3 and NdGaO3 disks, as well as powder sintered LaAlO3 and SrTiO3 discs. These targets were rotated during laser ablation and concentric trenches were formed with distinctive surface morphologies due to different doses of laser energy. We observed varied light-solid surface interactions on the targets prepared by different methods. The sintered targets exhibited surface explosions after long period laser ablation, presumably due to sub-surface overheating [1]. The single crystal targets have smoother surface morphology and the resulting films have much fewer particles on the surface. As such, they are preferred for laser ablation applications.