Plasma generation through vapor breakdown during ablation of a Si target by nanosecond KrF laser pulses is modeled using 0-dimensional rate equations. although there is some previous work on vapor breakdown by microsecond laser pulses, there have been no successful attempts reported on the same subject by nanosecond laser pulses. This work intends to fill the gap. a kinetic model is developed considering the following factors: (1) temperatures of both electrons and heavy-body particles (ions, neutrals, and excited states of neutrals), (2) absorption mechanisms of the laser energy such as inverse bremstrahlung (IB) processes and photoionization of excited states, (3) ionization acceleration mechanisms that include electron-impact excitation of ground state neutrals, electron-impact ionization of excited states of neutrals, photoionization of excited states of neutrals, and all necessary reverse processes. the rates of various processes considered are calculated using a second order predictor-corrector numerical scheme. the rate equations are solved for five quantities, namely, densities of electrons, neutrals, and excited states of neutrals, and the temperatures of electrons and heavy-body particles. the total breakdown times (sum of evaporation time and vapor breakdown time) at different energy fluences are then calculated. the results are compared with experimental observations of Si target ablation using a KrF laser.

ArF excimer laser-induced photolytic chemical vapor deposition of W on etched Si substrates using tungsten hexafluoride has been studied. Our experimental results show that tungsten film thickness is proportional to the laser irradiation time and fluence, and that the deposition rate initially increases, then decreases with increasing WF6 pressure. the activation energy obtained from an arrhenius plot is much less than that for conventional CVD. a deposition mechanism has been proposed which yields results in good agreement with the experimental dat A. the absorption cross section of WF6 is determined to be 2.75xl0-18 cm2/molecule.

A comparative study of arF- and KrF-laser deposition of amorphous diamond-like carbon (DLC) films and relevant carbon plasmas has been performed. Spectroscopic ellipsometry and EELS analysis of the DLC films deposited on Si <100> and NaCl substrates were utilized to characterize the high quality arF- and KrF-laser deposited films (up to 84% of sp3 bonded carbon in 7 J/cm2 -ArF-laser DLC film). Gated ICCD imaging, luminescence and ion current probe diagnostics of the carbon plume have revealed quite different properties of carbon plasmas generated by arF- and KrF- lasers. KrF-laser (6.7 J/cm2) irradiation produces a less energetic carbon plasma containing larger amounts of C2 and probably larger clusters compared with arF-laser irradiation at the same energy fluence. We conclude that the more energetic and highly-atomized arF-laser carbon plasma results in the better diamond-like properties.

Over the past few years Pulsed Laser Deposition (PLD) has become a popular technique for the deposition of a wide variety of thin films, and PLD systems are currently found in numerous industrial, government, university, and military laboratories. At present, it is estimated that well over 200 different materials have been deposited by PLD and the list keeps growing. However, even with all the interest in laser deposition the technique has not yet emerged as an industrial process. At the moment, industry still prefers standard thin film growth techniques such as magnetron and ion beam sputtering, chemical vapor deposition, and electron beam evaporation for production applications. These processes have been in use for decades and have demonstrated the ability to deposit films of most materials over large areas with excellent uniformity at reasonable cost and deposition rates. Furthermore, an entire infrastructure has been built up to support these processes including standardization of deposition rate monitors, power sources, target and crucible sizes, etc. On the other hand, laser-deposition is still an emerging technology, and relatively little infrastructure exists to adequately support either research or industrial applications. Since there are several materials which are difficult if not impossible to grow in thin-film form by more conventional techniques, it is expected that as pulsed laser-deposition matures this unique process will take its rightful place on the manufacturing line.

Boron nitride films grown by ion-assisted pulsed laser deposition have been characterized by infrared absorption, auger electron pectroscopy, and transmission electron microscopy. Elemental bonding and the crystallinity of BN films grown in three nitrogen ion energy regimes:high (2500 eV), low (700 eV), and without ions (0 eV) are examined, and the results interpreted within the framework of a compressive stress mechanism for cBN film growth.

Diamond-like Carbon(DLC) films have been deposited at Los alamos National Laboratory by pulsed ion beam ablation of graphite targets. the targets are illuminated by an intense beam of hydrogen, carbon, and oxygen ions at a fluence of 15-45 J/cm2. Ion energies are on the order of 350 keV, with beam current rising to 35 kA over a 400 ns ion current pulse.

Raman spectra of the deposited films indicate an increasing ratio of sp3 to sp2 bonding as the substrate is moved further away from the target and further off the target normal. Using a thin film platinum resistor at various positions, we have measured the heating of the substrate surface due to the kinetic energy and heat of condensation of the ablated material. Plume power density and energy input are inferred from the temperature measurements. This information is used to determine if substrate heating is responsible for the lack of DLC in positions close to the target and near the target normal.

Ion-surface interactions are thought to play a role in bias enhanced nucleation of diamond. To explore this hypothesis and understand the mechanisms, surface studies of hydrogen and hydrocarbon ion interactions with silicon and silicon carbide have been performed. the experiments were carried out at room temperature and used in-situ auger analyses to monitor the surface composition of thin films produced or modified by the ions. Ion energies ranged from 10 to 2000 eV. Hydrogen ions were found to modify silicon carbide thin films by removing silicon and converting the resulting carbon-rich layers to a mixture of sp2- and sp3-C. the interaction of hydrocarbon ions with silicon was shown to produce a thin film containing SiC-, sp2-, and sp3-C species. IN general, the relative amount of each species formed was dependent upon ion energy, fluence, and mass. the results of these studies, interpreted in terms of chemical and energy transfer processes, provide key insights into the mechanisms of bias enhanced nucleation.

Analysis of the phase behavior, structure, and composition of aluminum nitride thin films with up to 22% boron prepared by ion-beam assisted deposition is presented. the c-lattice constant of the film decreased with increasing boron content as expected from the formation of an aIN - wurtzite BN alloy. there was no evidence for separate boron nitride precipitation from either X-ray diffraction or FTIR. IN contrast, auger electron spectroscopy of the boron present in the films suggested that two types of boron bonding was present.

Epitaxial layers of Si1-x-yGexCy on Si(100) (x=0.13 and y=0.014 at peak concentration) were formed by ion implantation of Ge ions and C ions at room temperature (RT) and by subsequent IBIEC (ion-beam-induced epitaxial crystallization) process with 400keV Ge and ar ions at 300-400°C and SPEG (solid phase epitaxial growth) process up to 840°C. Crystallization up to the surface both by IBIEC and SPEG processes has been confirmed with RBS-channeling analysis. X-ray diffraction experiments have demonstrated strain compensation by incorporation of C atoms for IBIEC-grown Si1-x-yGexCy/Si samples, whereas strain accommodation due to C precipitation has been observed for SPEG-grown Si1-x-yGexCy/Si samples. Photoluminescence (PL) observed at 2K from IBIEC-grown samples has shown intense I1 peak with/without I1 related (Ar) peak and that from SPEG-grown samples has shown G line emission. these optical properties could suggest that small vacancy agglomeration is dominant in IBIEC-grown samples and C agglomeration is dominant in SPEG-grown samples, respectively.

Si1-x-yGexCy/Si heterostuctures were formed on Si (100) surface by Ge and C implantation with a high dose rate MEtal - Vapor Vacuum arc (MEVVA) ion source and subsequent Solid Phase Epitaxy (SPE). after thermal annealing in the temperature range from 600 °C to 1200 °C, the implanted layer was studied using Rutherford Back-scattering Spectrometry (RBS), cross-sectional High Resolution Transmission Electron Microscopy (HRTEM) and fourbounce X-ray Diffraction (XRD) measurement. Due to the small lattice constant and wide bandgap of SiC, the incorporation of C into Si-Ge can provide a complementary material to Si-Ge for bandgap engineering of Si-based heterojunction structure. Polycrystals are formed at temperature at and below 1000 °C thermal growth, while single crystal epitaxial layer is formed at 1100 °C and beyond. XRD measurements near Si (004) peak confirm the compensation of the Si1-x Gex lattice mismatch strain by substitutional C. C implantation is also found to suppress the End of Range (EOR) defect growth.

We report the results of an investigation to grow thin Si films on Si substrates at low substrate temperatures using ionized SiH4 gas generated with a Kaufman type ion gun. This investigation shows island-growth at higher substrate temperatures (500-700°C) in the form of square-based pyramids. by lowering the substrate temperature to 300°C, we were able to achieve a planar growth. the growth rate can be enhanced by introducing elemental Si from a thermal evaporation source. Scanning electron microscopy, transmission electron microscopy and electron diffraction analysis were used to study the crystalline quality of the samples prepared at different temperatures.

A beam of metal cluster ions of variable size is deposited with variable kinetic energy on a substrate. Mirror-like and strongly adhering films are produced on unheated substrates for sufficiently high cluster impact energies. Numerical simulations provide the physical insight why this novel technique gives different, and sometimes superior results compared to conventional methods. Several examples are presented.

Cathodic arc plasma deposition was used to coat Al2O3 powder (mesh size 60) with platinum. the power particles were moved during deposition using a mechanical system operating at a resonance frequency of 20 Hz. Scanning electron microscopy and auger electron microscopy show that all particles are completely coated with a platinum film having a thickness of about 100 nm. the actual deposition time was only 20 s, thus the deposition rate was very high (5 nm/s).

We present a review of our recent work concerning supersonic molecular beam scattering of thin film precursors from the Si(100) and Si(111) surfaces. Both SiH4 and Si2H6 exhibit translationally activated dissociation channels at sufficiently high incident kinetic energies, (E┴) 0.5 eV. the dominant variables under our reaction conditions are the incident kinetic energy and the angle of incidence, whereas mean internal energy and substrate temperature play relatively minor roles. the former two variables couple to produce a universal relationship between the reaction probability and a scaled kinetic energy given by (E┴) = Eі[(l-Δ)cos2θі + 3Δsin2θі], where θі is the angle of incidence, a is a corrugation parameter, and 0 ≤ Δ ≤ 1. IN addition to the reaction probability, the reaction mechanism for Si2H6 is also dependent upon incident kinetic energy and surface structure, where a SiH4(g) production channel is observed on the Si(111)-(7x7) surface at low to moderate incident kinetic energies. the reactions of SiH3CH3 and PH3 provide convenient comparative examples. Methylsilane, reacting on a β-SiC surface, exhibits a translationally activated dissociation channel, similar to what is observed for SiH4 and Si2H6. Phosphine, on the other hand, exhibits the characteristics of trapping, precursor-mediated dissociative chemisorption. these results act to underscore the important role played by the frontier orbital topology, even at hyperthermal incident kinetic energies.

A photolytic source of H atoms is used to probe abstraction and adsorption reactions on the D/Si(100) monodeuteride surface. Surface H and D coverages are determined for H atom exposures, with incident average kinetic energies of 1.0 and 2.8 eV. the D atom depletion probability per incident H atom is 0.3±0.2 for both kinetic energies, and is likely due to abstraction. these results, together with previous studies, indicate that the rates of depletion of surface D and the uptake of H are nominally independent of H atom kinetic energy over the range of about 0.3 to nearly 3 eV.

Pulsed, supersonic jets of CBr4 seeded in a hydrogen bath gas have been used to deposit films on silicon at low temperatures (c A. 100° C) in a high vacuum chamber. IN situ analysis of the films using x-ray photoelectron spectroscopy (XPS) and depth profiling indicate a surface composition of 34% Br and 66 % C and a bulk composition of 88% C and 12% Br. the deposition efficiency of CBr4 was found to drop dramatically when seeded in bath gases of deuterium, helium, and argon, suggesting that the film growth is an activated process, requiring precursor energies of at least 3.6 eV.

Carbon ion (C+) irradiation during molecular beam epitaxy (MBE) growth of GaAs/GaAs and in0.53.Ga0.47As/InP layers was carried out using CIBMBE (combined ion beam and molecular beam epitaxy) method as a function of wide acceleration energy (Ea=30 eV-30 keV) at a constant ion beam current density. Judging from the monitored current density and the net hole concentration (INA-ND|) obtained from Hall effect measurements, activation rate as high as 88% was achieved for as-grown GaAs layers by C+ ion irradiation of Ea=~170eV. It was revealed that by annealing at 800°C, a slight enhancement (~ 10%) of INA-ND| is practiced for Ea <~ 130eV but a significant increase of INA-ND| is realized for Ea>~lkeV. IN in0.53Ga0.47As/InP layers with increasing Ea, a type conversion of electric conduction from n to p was found to occur at Ea= ~70~100eV. these observations describe that Ea plays a vital role to determine the location of incorporated electrical and optical active impurities in GaAs and inGaAs. Further for comparison, C+-implanted GaAs layers were prepared by high-energy (400 keV) ion-implantation as a function of substrate temperature (T1=RT-600 °C). For C dose concentration of lxl018cm-3\ the highest activation rate of ~20 % was obtained at T1=~150 °C. This result states that CIBMBE method is a superior doping method in view of activation rate of introduced dopants and the formation of damage-free ion-irradiated layers.

Si ion implantation followed by thermal annealing has been used to synthesize luminescent nanometer-sized Si crystals in an amorphous Si02 matrix. Transmission electron microscopy indicates the formation of Si nanocrystals by annealing at 1100 °C, and the growth in average size of Si nanocrystals with increasing annealing time. the shape of the emission spectrum of the photoluminescence is found to be independent of both excitation energy and annealing time, while the excitation spectrum of photoluminescence increases as the photon energy increases and its shape depends on annealing time. the results indicate that the photons are absorbed by Si nanocrystals, for which the band-gap energy is modified by the quantum confinement effects, and the emission of photons is not due to direct electron-hole recombination inside Si nanocrystals but is related to defects probably at the interface between Si nanocrystals and Si02.

Initial nitridation of molecular beam epitaxially (MBE) grown GaAs surfaces by means of an electron cyclotron resonance (ECR) microwave plasma source is investigated in situ through time-resolved reflection high energy electron diffraction (RHEED), and ex situ high-resolution X-ray diffraction (HRXRD) techniques. Brief (< 8-10 s) plasma exposure of GaAs (100) surfaces results in surface N-for-As anion exchange and a new, specular, commensurate (3x3) RHEED pattern which appears to correspond to up to 1 monolayer of coherently strained GaN on GaAs. anion exchange kinetics is studied through the time-dependence of the onset and decay of the (3x3) RHEED pattern as a function of substrate temperature. For the first time, coherently strained GaNyAs1_y /GaAs heterostructures are grown and characterized. Direct evidence for thermally activated processes from both RHEED and HRXRD observations is presented, and N desorption and surface-segregation phenomena are proposed to explain the experimental results.

GaN films were deposited on sapphire (0001) from triethylgallium (TEG) and NH3 seeded in separate He free jets. as the dissociative chemisorption of NH3 is expected to be rate-limiting in GaN growth, the NH3/He nozzle temperature was varied to control the incident kinetic energy of the NH3 molecules. Using an NH3/TEG flow ratio of 205 and an NH3/He nozzle temperature of 400°C, stoichiometric films were deposited at substrate temperatures ≥530°C. Scanning electron microscopy revealed that films deposited at 580°C are polycrystalline α-GaN with randomly oriented 0.5-μm grains. Films with a closely similar morphology are deposited by using an NH3/He nozzle temperature of 90°C. IN contrast, films deposited at 580°C using an NH3/He nozzle temperature of 510°C consist of whiskers (aspect ratio = c A. 4) which exhibit a-GaN (0001)/sapphire (0001) heteroepitaxy, as evidenced by X-ray diffraction and reflection high-energy electron diffraction.