bluuebunny/crossref_metadata_2025 huggingface dataset:
Vacuum vapor deposited thin films of a perylene dicarboximide derivative: Microstructure versus deposition parameters
Authors: Debe M. K. , Kam K. K. , Liu J. C. , Poirier R. J.
Published: July 2002

The microscopic physical structure in thin films of vapor deposited, large heterocyclic organic molecules is strongly dependent on the deposition parameters. The scale of the microstructure can vary enormously compared to inorganic systems, strongly affecting the macroscopic properties. Multiple polymorphs frequently characterize these systems. We have extended our previous work with the perylene dicarboximides to include a phenethyl derivative. Films in the 300–1000 Å thickness range, deposited on metal and transparent substrates at varying rates and substrate temperatures from −165 to 155 °C, with and without vacuum annealing, have been characterized by scanning electron microscopy, ultraviolet/visible, and infrared (IR) spectroscopies, and polarization modulation reflectivity changes. Evidence is presented for a critical substrate temperature between −22 and −32 °C. Also a polymorphic phase sensitivity to deposition substrate temperature and rate is demonstrated, consistent with an exothermic peak observed by differential scanning calorimetry of the vapor deposited material, and an annealing induced molecular reorientation observed by reflection absorption IR.
Transient fluorocarbon film thickness effects near the silicon dioxide/silicon interface in selective silicon dioxide reactive ion etching
Authors: Jaso Mark A. , Oehrlein Gottlieb S.
Published: July 2002

We have utilized an on-line ellipsometer to perform real time measurement of the thickness of fluorocarbon films formed on Si during overetching in selective silicon dioxide reactive ion etching (RIE) using CF4/H2. Employing an ultrahigh vacuum surface analysis system interfaced via a transfer chamber to the RIE system, x-ray photoelectron spectroscopy analysis was also performed on reactive ion etched SiO2 just before the encounter of the SiO2/Si interface (≂3-nm SiO2 remaining) during etching and for Si just after etching through the interface (overetch time <15 s). The SiO2 surface was essentially free of fluorocarbon film. The formation of the fluorocarbon film on Si after etching through the SiO2/Si interface was shown to occur very fast and achieve a near steady-state thickness value within ≂15 s for our etching conditions.
Determination of the power and current densities in argon and oxygen plasmas by i
n s
i
t
u temperature measurements
Authors: Visser R. J.
Published: July 2002

I n situ temperature measurements of silicon wafers in argon and oxygen plasmas are presented. The processes which determine the heat flow from and to the wafer have been established. It is found that conduction of heat to the electrode does not contribute to the heat loss of the wafer. Radiation of heat and conduction of heat by the gas are the main loss processes. The heat flux qp from the plasma to the wafer is independent of time and temperature. This is attributed to the flux of high-energy ions to the wafer. By measuring the plasma potential, the energy of the ions is estimated. The ion current density is calculated from qp and the energy of the ions. The value which is obtained is compared to those obtained with other methods. It is concluded that the power density on the electrode can differ by almost an order of magnitude from an estimation using the dissipated rf power and the electrode area.
Nucleation of misfit dislocations in strained-layer epitaxy in the GexSi1−x/Si system
Authors: Hull R. , Bean J. C.
Published: July 2002

We describe theoretical and experimental investigations of the nucleation of lattice mismatch-accommodating dislocations in the strained GexSi1−x /Si(100) system. Experimentally it is found that at lower mismatches nucleation appears to be associated with growth defects, while at higher x, surface loop nucleation is favored. Theoretical predictions of the magnitude of activation barriers for homogeneous nucleation of dislocation half-loops at the growth surface decline dramatically with increasing lattice mismatch (higher x), with nucleation of mixed climb and glide (90°) loops favored to pure glide (60°) loops. These activation barriers for surface half-loops are shown to be lower than previously calculated due to consideration of the random alloy nature of the GexSi1−x epilayer.
Plasma characterization for a divergent field electron cyclotron resonance source
Authors: Forster John , Holber William
Published: July 2002

A set of experiments has been carried out in order to characterize the plasma extracted from a divergent magnetic field electron cyclotron resonance plasma source. Langmuir probe and Faraday cup measurements have been used to measure the electron temperature, plasma density, and plasma uniformity in the extracted plasma. Plasma production efficiencies of better than 1 A of extracted plasma per 300 W of microwave power have been observed. Electron densities greater than 3×1011 cm−3 have been measured over a range of pressures. A strong correlation is found between the radial dependence of the ion saturation current and the resultant rates and uniformity of photoresist etched with O2 gas.
Review of hydrogen pellet injection technology for plasma fueling applications
Authors: Milora S. L.
Published: July 2002

In the past several years, steady progress has been made worldwide in the development of high-speed hydrogen pellet injectors for fueling magnetically confined plasmas. Several fueling systems based on the conventional pneumatic and centrifuge acceleration concepts have been put into practice on a wide variety of toroidal plasma confinement devices. Long-pulse fueling has been demonstrated in the parameter range 0.8–1.3 km/s, for pellets up to 6 mm in diameter, and at delivery rates up to 40 Hz. Conventional systems have demonstrated the technology to speeds approaching 2 km/s, and several more exotic accelerator concepts are under development to meet the more demanding requirements of the next generation of reactor-grade plasmas. These include a gas gun that can operate in tritium, the two-stage light gas gun, electrothermal guns, electromagnetic rail guns, and an electron-beam-driven thruster. Although these devices are in various stages of development, velocities of 3.8 km/s have already been achieved with two-stage light gas guns, and the prospects for attaining 5 km/s in the near future appear good.
Investigation of the behavior of a plasma-arc armature inside a two-stage railgun and methods for preventing arcing
Authors: Kim Kyekyoon , Zhang David J.
Published: July 2002

Results from a recent hydrogen pellet acceleration study using a 3.2-mm-diam two-stage electromagnetic railgun are reported. By installing a pressure-relieving coupling piece between the first-stage gas gun and the second-stage railgun and thereby controlling the pressure distribution inside the railgun bore, spurious arcing that prevented operation of the railgun at high voltages (and therefore high currents) was eliminated. Consequently, voltages and currents as high as 10 kV and 23.5 kA, respectively, could be used to operate the gun. A record output velocity of 2.2 km/s and an acceleration of 2.92×106 m/s2 were achieved for a solid hydrogen pellet, 3.2 mm in diameter and 4 mm in length, using a railgun of 1-m length.
Characterization of as-prepared and annealed hydrogenated carbon films
Authors: Gonzalez-Hernandez J. , Chao B. S. , Pawlik D. A.
Published: July 2002

Hydrogenated amorphous carbon films were obtained from the decomposition of methane using a rf-couple glow-discharged system at power densities ranging from 0.4 to 4.8 W/cm2 . The structure of as-prepared and annealed films were characterized by Raman spectroscopy, infrared absorption, photoluminescence, energy-loss spectroscopy, and x-ray diffraction. The results indicate that the incorporated hydrogen concentration is an important parameter in determining the structure and properties of the films. Carbon films deposited at a lowest rf power density contain a large amount of hydrogen with most of the C–H bonds in CH3 configurations, whereas films produced at higher rf powers reveal dominant CH2 bonding structures. According to Raman scattering measurements the sp2 domains in as-prepared samples are disordered due perhaps to bond-angle distortions. Upon annealing, hydrogen leaves the film at a temperature that depends on the initial hydrogen concentration. Once most of the hydrogen has been driven out, crystallization into the graphite phase takes place. The microcrystallite size was measured by Raman and x-ray diffraction.
Rotational dynamics of desorption and inelastic scattering for the NO/Pt(111) system
Authors: Jacobs D. C. , Kolasinski K. W. , Madix R. J. , Zare R. N.
Published: July 2002

The rotational population and alignment distributions of NO are measured subsequent to the molecule’s interaction with a clean Pt(111) surface. Two distinct dynamical regimes of trapping/desorption and inelastic scattering are studied over the temperature range 375–550 K. For the case of molecular desorption, molecules which desorb with a large amount of angular momentum (J>12.5) prefer to rotate in the plane of the surface. Those molecules which scatter from the surface show the opposite preference for rotational alignment, i.e., they preferentially rotate in a plane perpendicular to the surface. The non-Boltzmann rotational distribution reveals that a large fraction of the scattered molecules contain more energy in rotation than initially exists as total energy in the beam. This observation indicates the important role of surface vibration to rotational energy transfer in this system. A quasiclassical stochastic trajectory model is able to account for much of the observed phenomena.
Magnetic ultracentrifuge with a microshell rotor
Authors: Moroz Pavel E. , Weber F. Neff
Published: July 2002

Study was conducted in two directions with regard to the possibilities of the giga-g centrifuging of liquids and other experimental samples: (i) The first was initial development of a magnetic ultracentrifuge for small ferromagnetic rotors suspended in a vacuum, including systems of electromagnetic suspension, spinning, stabilization of the rotor position, laser illumination of the rotor for its microscopical examination in the process of rotation, and measurement of the speed of rotation. (ii) The second direction was a review of the literature of various types of (sub)millimeter hollow microspheres (microshells) which might serve as rotor prototypes, including metallic, glass, carbon, and plastic microshells, approaches to their ferromagnetic coating, drilling an opening, filling, and sealing, as major steps of preparation of a rotor from a microshell.
Scanning tunneling spectroscopy on cleaved silicon p
n junctions
Authors: Kordić S. , van Loenen E. J. , Dijkkamp D. , Hoeven A. J. , Moraal H. K.
Published: July 2002

Scanning tunneling microscope (STM) I–V experiments in air on freshly cleaved Si pn junctions, are presented. It is shown that the interaction between the tip and the sample may cause the whole structure to behave as a solid-state device. With the tip in the vicinity of the pn junction the junctions depletion layer may pinch off the tip current, in much the same way as the increasing gate bias of a junction field-effect transistor reduces the channel current. Under other bias conditions, the STM tip may locally forward bias the pn junction causing a sharp increase in the tip current. Using this mode of operation the pn junction was localized to within 50 nm. A dependence of the tip-sample I–V characteristic on the local impurity concentration of the sample was also observed. A simple qualitative model consisting of a diode, which represents the tip–Si junction, in series with the resistance of the underlying material, explains these measurements.
Performance of a scanning force microscope using a laser diode
Authors: Sarid Dror , Iams Douglas A. , Ingle Jeffery T. , Weissenberger Volker , Ploetz Josef
Published: July 2002

We demonstrate a scanning force microscope using a laser diode with a sensitivity of 3 pm per (Hz)1/2 in the vertical direction. The system, which contains no optical elements other than the laser diode and its integrated photodiode, is currently used to image magnetic domains.
On the temperature dependence of the deposition rate of amorphous, hydrogenated carbon films
Authors: Kersten H. , Kroesen G. M. W.
Published: July 2002

The temperature behavior of the deposition rate of amorphous, hydrogenated carbon films is analyzed both experimentally and theoretically. A reactor based on the supersonic expansion of an arc plasma is used. The film thickness is measured using in situ He–Ne ellipsometry. The surface temperature is measured with thermocouples. Comparison of the presented model with the experimental results suggests that the deposited atoms and radicals diffuse over the surface in a weakly bound, adsorbed layer before they are incorporated in the film. Direct incorporation upon chemisorption is improbable.
A compact flange-mounted electron beam source
Authors: Jonker B. T.
Published: July 2002

A compact rod-fed electron beam source is described which provides clean and controlled deposition of high-temperature materials at relatively low rates. The source is inexpensively fabricated as a flange-mounted, bolt-on accessory to a surface analysis or deposition chamber, requires only two commonly available power supplies to operate, and does not interfere with the use of surface electron spectroscopies during operation.
Wall conditioning and leak localization in the Advanced Toroidal Facility
Authors: Langley R. A. , Glowienka J. C. , Mioduszewski P. K. , Murakami M. , Rayburn T. F. , Simpkins J. E. , Schwenterly S. W. , Yarber J. L.
Published: July 2002

The Advanced Toroidal Facility (ATF) vacuum vessel and its internal components have been conditioned for plasma operation by baking, discharge cleaning with hydrogen and helium, and gettering with chromium and titanium. The plasma-facing surface of ATF consists mainly of stainless steel with some graphite; the outgassing area is dominated by the graphite because of its open porosity. Since this situation is somewhat different from that in other fusion plasma experiments, in which a single material dominates both the outgassing area and the plasma-facing area, different cleaning and conditioning techniques are required. The situation was aggravated by air leaks in the vacuum vessel, presumably resulting from baking and from vibration during plasma operation. The results of the various cleaning and conditioning techniques used are presented and compared on the basis of residual gas analysis and plasma performance. A technique for detecting leaks from the inside of the vacuum vessel is described. This technique was developed because access to the outside of the vessel is severely restricted by external components.
Surface studies of polyether–polyester copolymers and blends
Authors: Burrell Michael C. , Bhatia Qamar S. , Chera John J. , Michael Raj S.
Published: July 2002

The surface composition and morphology of a series of thermoplastic elastomers based on polyester (PBT)–polyether (PPG) copolymers have been studied using x-ray photospectroscopy (XPS) and static secondary-ion-mass spectroscopy (SIMS). In all cases, an enrichment of the polyether soft block at the surface is observed. The degree of preferential surface adsorption is greater for molded specimens compared ot the solvent cast films. The enrichment factor (surface content/bulk content) is greater for speciment of highest PBT content. Angle-dependent XPS measurements are fit with an enriched overlayer model and a continuous profile model. Static SIMS measurements are consistent with the XPS results for molded versus solvent cast films, but indicate that some PBT is present at the outer surface of all specimens analyzed.
Scanning tunneling potentiometry studies of Y1Ba2Cu3O7−x and gold thin films
Authors: Kent A. D. , Maggio-Aprile I. , Niedermann Ph. , Renner Ch. , Fischer O/.
Published: July 2002

We have used a scanning tunneling microscope to study the local electrostatic potential distribution and topography of thin films of gold at room temperature and high-Tc superconducting thin films at low temperature in the presence of a transport current. On continuous gold thin films (85 Å thick), high resolution scans often show abrupt changes in the potential, which are clearly associated with topographic features. On a relatively large scale (1 μm), a more uniform potential drop is observed but locally these scans also reveal small steps in the potential. These steps may be a characteristic property of transport in these thin polycrystalline films or, alternatively, could be artifacts due to discontinuous changes in the tunneling position on the sample during scanning. On high-Tc superconducting thin films , a thin gold overlayer permits potentiometry studies at low temperature. The first low-temperature potentiometry studies show a clear change in behavior at the normal-superconductor transition.
Magnetron sputtered TiAlON composite thin films. II. Optical and electrical properties
Authors: Luthier R. , Lévy F.
Published: July 2002

The optical and electrical properties of well characterized composite TiAlON thin films are presented. The samples display a low reflectance in the visible–near-UV spectral range (below 16%) and high absorption coefficients (1–4×105 cm−1). Standard deposition conditions, defined with respect to the desired functional properties as decorative coatings, yield the darkest shades with flat reflectance spectra (between 10% and 12%). Spectroscopic ellipsometry studies show that these features are intrinsically related to the two-phase structure. Differences among the samples result from the porosity level inherent to columnar microstructures. The generalized Maxwell Garnett theory is used to estimate the level of porosity in standard TiAlON. A void fraction of 0.15 is calculated, well correlated with the available microstructural observations. The electrical resistivities of 2 μm thick TiAlON films are determined by the van der Pauw method. At room temperature, values between 10−3 and 10−2 Ω m are measured for the different samples. The negative temperature coefficients of resistivity support the description as a separate grain structure. The conduction mechanism can be postulated as thermally activated tunnelling from one conductive (Ti,Al)Nx grain to the next, across the dielectric barrier formed by the oxide matrix. However, the temperature dependence of log(ρ/ρ0) does not follow a simple T−1/2 power law. The observed exponent increases continuously from this limiting value as the temperature is raised.
The electrostatic nature of contaminative particles in a semiconductor processing plasma
Authors: Nowlin R. N. , Carlile R. N.
Published: July 2002

Two models are presented to describe the immediate environment surrounding negatively charged contaminants in an idealized argon plasma. The first model uses Poisson’s equation to determine the contaminant charge and voltage. This model predicts a critical radius of the order of the Debye length below which Poisson’s equation is no longer valid. Below the critical radius and for contaminant radii much less than the Debye length, the Coulomb potential is used to find the contaminant charge and voltage. Both models predict negative charges on the order of 10−14 C, and voltages on the same order of magnitude as the electron energy.
Deposition of transparent ZrO2 on polyetherimide using a KrF excimer laser
Authors: Chuang Mei-Chen , Smith Gary A.
Published: July 2002

The laser ablative deposition technique was used to deposit thin films of ZrO2 on polyetherimide. The microstructure of the film was studied by x-ray diffraction, XPS, and SEM.
Nonisotropic deposition from a 304 stainless-steel cathodic arc source
Authors: Poirier D. M. , Lindfors P. A.
Published: July 2002

Films deposited via cathodic arc technology from a 304 stainless-steel cathode were investigated as a function of angle measured from the normal to the surface of the cathode. The composition of the films as measured via energy dispersive x-ray analysis was found to vary with the position of the substrate. In addition the top and bottom layers of the films at all positions were found to be rich in chromium. These results can be understood as stemming from preferential evaporation of Cr from the droplets that are a part of the cathodic arc emission process.
Ion plating as an industrial manufacturing method
Authors: Pulker H. K.
Published: July 2002

Plasma-supported reactive deposition technologies set up possibilities to produce high-quality compound films for various applications. In the Balzers activated reactive ion plating (ARIP) system the hot filament cathode of a non-self-sustaining arc source provides electrons directed to an anodic crucible to evaporate Ti. On their way, the low-voltage electrons produce a magnetically confined discharge plasma in the working and reactive gas and in the coating material vapor. Ionization, dissociation, and excitations occur. By acceleration to negatively biased, precleaned substrates, the kinetic and potential energy of the positive ions and excited species is responsible for the formation of well adherent, hard, dense, and stoichiometric compound films such as TiN and TiCxNy. ARIP is used worldwide in an economic high-volume production of wear-resistant coatings on steel tools and machine parts. Another commercial system was obtained by combining a 270° e-beam evaporator with the thermionic arc source. Using self-biasing of insulators, unheated glass substrates can be coated by this reactive low-voltage ion plating process with hard, dense, generally amorphous oxide and nitride films for particularly optical applications. Multilayers with stable optical characteristics have been obtained showing excellent mechanical and environmental resistivity.
C–H bond activation on metals: A quantum dynamics model of direct and precursor mediated dissociation
Authors: Luntz A. C. , Harris J.
Published: July 2002

We summarize here a recently developed quantum dynamical model to describe the dissociation of small alkanes on metal surfaces. This model is based on solving the dissociation dynamics quantum mechanically for a quasidiatomic R–H interacting with a metal surface through a reduced dimensionality potential energy surface. We find that for typical thermal conditions, both the direct (on-impact) dissociation and that due to precursor processes are dominated by tunneling, albeit in a somewhat more complicated form than usually envisioned in simple models. Because of this, we contend that traditional classical kinetic interpretations are not valid, e.g., an Arrhenius analysis of rates does not measure barrier parameters.
Low-energy electron diffraction studies of atomic step transitions on a Ni(111) vicinal surface
Authors: Chang Jae P. , Blakely Jack M.
Published: July 2002

A low-energy electron diffraction system with a two-dimensional position sensitive detector was used to investigate the step clustering phase transition on a Ni surface vicinal to (111), i.e., Ni (111) 5° [112̄]. The directions parallel and perpendicular to the step edges were [112̄] and [11̄0], respectively, and the surface was miscut by 5° about the [112̄] axis. Split beams at high temperature, indicative of a single atomic height step structure, coalesced to single beams as the temperature was lowered. The transition occurred around 560 K, and was reversible with some hysteresis. Scans along the [111] truncation rod were performed by changing the incident beam energy. Beam profile analysis was done to quantitatively analyze the change of step and terrace distributions on the surface. Kinematic calculations of intensity distributions were made for a two phase model, in which the surface was taken to consist of different areas, one type with large terraces and the other with small terraces, and compared with the experimental data. Two gamma functions were used for the terrace distribution and one exponential function for the step distribution. Fitting of experimental results to the calculation showed that step clustering and (111) faceting occurred as temperature decreased. The measured hysteresis in the heating and cooling cycles might be due to nucleation in a first order phase transition involving coexistence of regions with single atomic height steps and regions with double atomic height steps. The present result is consistent with our previous reported observation on a Ni vicinal surface tilted by 5° about the [11̄0] axis, i.e., Ni(111) 5° [11̄0], using glancing incidence x-ray diffraction.
Iodomethane dissociation on Cu(111): Bonding and chemistry of adsorbed methyl groups
Authors: Lin Jong-Liang , Bent Brian E.
Published: July 2002

The chemistry of iodomethane on a Cu(111) surface has been studied by a combination of work function measurements, Auger electron spectroscopy, high-resolution electron energy-loss spectroscopy, and temperature programmed reaction spectroscopy. Our results show that iodomethane dissociates below 200 K to form iodine atoms and methyl groups, which are stable up to 400 K. At low coverages, the methyl groups bond with Cs symmetry and at high coverages with C3v symmetry. The methyl group stretching frequency on the surface is redshifted by ∼150 cm−1 compared to that of iodomethane. Possible bonding sites as well as reasons for the stretching mode softening and coverage-dependent orientation of methyl groups are discussed. The surface reactions of methyl groups on Cu(111) are coverage dependent. At low coverages, CH3(a) decomposes at 450 K to evolve methane, ethylene, and propylene. α elimination from methyl groups to produce CH2 and H is the rate-determining step in forming these products. At higher coverages, methyl coupling also occurs to evolve ethane.
Defects in hard coatings studied by positron annihilation spectroscopy and x-ray diffraction
Authors: Schaffer James P. , Perry Anthony J. , Brunner Jean
Published: July 2002

TiNx (0.5<x<1.1) thin films, grown on stainless steel substrates via reactive sputtering, have been studied using positron annihilation spectroscopy and x-ray diffraction techniques. The deposition parameters investigated include nitrogen partial pressure, deposition power, substrate bias, film thickness, and substrate condition. The synergistic effects of using multiple techniques to characterize the same or similar samples is emphasized.
Fast pump-down aluminum ultrahigh vacuum system
Authors: Ishimaru H. , Itoh K. , Ishigaki T. , Furutate M.
Published: July 2002

An extremely fast pump-down aluminum ultrahigh vacuum system has been developed, with an evacuation time of less than 5 min from atmosphere to pressures in the 10−9 Torr range. Key elements of the system are: (1) a moisture trap (three-stage sintered metal filter) to produce super-dry nitrogen gas, with a water content of about 10 parts per billion, and (2) a cryogenic aluminum alloy panel. A 50 ℓ/s turbomolecular pump is initially used to evacuate the chamber, followed by a 300 ℓ/s turbomolecular pump as the main pump, which immediately operates with normal its full speed. The system can be vented to atmospheric pressure, with the use of super-dry nitrogen gas at a flow rate of 10 ℓ/min, without degradation of the fast pump-down time.
Photoemission studies of zinc-noble metal alloys: Zn–Cu, Zn–Ag, and Zn–Au films on Ru(001)
Authors: Rodriguez José A. , Hrbek Jan
Published: July 2002

Zn and the noble metals alloy when coadsorbed on Ru(001). The properties of Zn–Cu, Zn–Ag, and Zn–Au alloys have been studied using core- and valence-level photoemission and temperature programmed desorption. Alloy formation induces only small shifts (−0.2 to −0.3 eV) in the position of the Zn 2p, 3s, and 3d levels. In contrast, the core and valence levels of the noble metals show large shifts toward higher binding energy. For small amounts of Cu, Ag, and Au dissolved in Zn multilayers, the shifts in the core levels of the nobel metals follow the sequence: Cu(2p3/2), 0.8 eV≊Ag(3d5/2), 0.8 eV<Au(4f7/2), 1.4 eV. The magnitude of the shift increases as the Pauling electronegativity of the noble metal increases. However, the sign of the shifts for the Cu(2p3/2), Ag(3d5/2), or Au(4f7/2) levels is not directly determined by the direction of charge transfer within the corresponding Zn-noble metal bond.
Growth of plasma-generated particles and behavior of particle clouds during sputtering of silicon and silicon dioxide
Authors: Yoo W. J. , Steinbrüchel Ch.
Published: July 2002

We have observed particles nucleated and grown in an Ar sputtering plasma from Si and SiO2 substrates. With both materials, particle clouds forming near the plasma sheath boundary were studied by laser light scattering. Roughly spherical particles ranging down to 70 nm were collected on transmission electron microscopy grids installed downstream from the wafer even before the onset of laser light scattering. Electron microscopy revealed the structure as well as the size distribution of the particles. The size distribution is essentially monodisperse for very small particles but becomes much wider and spatially varying as the average particle size increases with time. Pressure and flow rate determined the spatial position and the extent of development of the particle cloud above the wafer. Spatial dependence of clouds on pressure and flow rate can be used to control particle formation or particle deposition on the wafer.
Surface structure of SrTiO3(001) with various surface treatments
Authors: Hikita Tokihisa , Hanada Takashi , Kudo Masahiro , Kawai Maki
Published: July 2002

Three kinds of SrTiO3(001) surfaces, TiO2 terminated, SrO terminated, and a mixture of these surfaces, are selectively formed and their surface structures are examined by means of reflection high energy electron diffraction, x-ray photoelectron spectroscopy, and x-ray photoelectron diffraction. The TiO2 terminated surface is obtained under a moderate temperature (<700 K) cleaning by the Bi deposition/desorption method and subsequent oxidation, where the distance between the first TiO2 plane and the SrO plane underneath is 1.95+0.07 Å and the oxygen of the first TiO2 plane is pulled out 0.10 Å. The SrO terminated surface is obtained by growing one monolayer of SrO on the TiO2 terminated surface, where the distance between the first SrO plane and TiO2 plane underneath is 1.95+0.10 Å and the oxygen of the first SrO plane is pulled out 0.16 Å. These two surfaces are different from the surface obtained by Ar+ sputtering and annealing, which is found to be the mixture of TiO2 and SrO terminated surfaces.
Hydrogen atom detection by H− conversion
Authors: Samano E. C. , Carr W. E.
Published: July 2002

Surface ionization on a commercially available barium oxide converter has been used to find the total beam intensity in the forward direction of hyperthermal hydrogen atoms dissociated by an arc discharge. The H− ions are selected by a mass spectrometer and measured by a Faraday cup in a high vacuum system. A Monte Carlo simulation is used to calculate the H− yield of low-energy atoms perpendicularly reflected from the converter as a model for atom-surface ionization. A beam intensity of approximately 4×1017 atoms/sr s is found by means of the calculated H− yield and the measured H− current. The results of this experiment are compared with the characterization of the same atom beam achieved by other methods and similar atom beams published in recent literature.
Time-resolved spectroscopic studies of the ultraviolet-laser photolysis of aluminum bromide for Al film growth
Authors: Karasawa T. , Bramblett T. R. , Lubben D. , Greene J. E. , Carlsson J.-O.
Published: July 2002

Time-resolved optical emission spectroscopy, with a resolution of ≂10 ns, was used to investigate the formation of excited photofragments during pulsed ArF excimer-laser irradiation of gaseous aluminum bromide. The solid Al2Br6 source was maintained at 50 °C and Ar used as a carrier gas to provide an aluminum bromide partial pressure of ≂3×10−6 Torr (4×10−4 Pa). The total pressure in the reactor was typically 300 mTorr (40 Pa). Following the laser pulse, emission was observed from the Al 4s 2S1/2→3p 2P1/2 and 4s 2S1/2→3p 2P3/2 transitions at 394 and 396 nm, respectively. The decay of the Al emission intensity IAl was convoluted with the temporal shape of the excitation pulse since the radiative lifetime of the Al 2S state, 6.8 ns, was less than the laser pulse width, ≂20 ns. The rise time of IAl, on the other hand, was <10 ns, indicating that Al was formed photolytically rather than through subsequent collisions involving photofragments. IAl varied with the ArF laser intensity Ihν as IAl∝I2hν for Ihν≲4.5 MW cm−2 and IAl∝Ihν at higher laser fluences. Raising the source gas temperature to increase the AlBr3 to Al2Br6 ratio in the feed gas, at constant total pressure, dramatically increased IAl.
Electric current oscillations in a parallel-plate plasma reactor
Authors: Seeböck R. J. , Deutsch R. , Räuchle E.
Published: July 2002

In a radio-frequency plasma reactor excited at low frequencies (30–300 kHz), disturbances of the voltage signal and nonlinear oscillations in the current signal were observed. It is shown that the disturbances of the voltage signal can be used to determine the plasma potential and the negative bias. From the nonlinear oscillations of the current signal, the electron density and the electron temperature can be derived by two different methods. One uses the numerical simulation of the voltage and current signals and is described in detail. The other method is based on the analysis of fast current oscillations and is used as a cross check.
Angular impact energy distributions of argon ions at the powered electrode of a helicon plasma source
Authors: Janes Joachim
Published: July 2002

A radio frequency excited helicon plasma is generated by coupling externally generated electric and magnetic fields into the plasma confined by an axial magnetic field. The 13.56 MHz rf power provided via an antenna is varied between 100 and 500 W. The axial magnetic field strength is varied between 25 and 150 G. The substrate electrode is independently powered with 13.56 MHz radio frequency. A 100 μm orifice in the substrate electrode allows a small sample of argon ions bombarding the substrate electrode to enter a detection chamber. In the detection chamber a quadrupole mass spectrometer equipped with an energy filter is used to measure mass selected ion energy distributions and by tilting the quadrupole analyzer with the vertex lying in the orifice ion angular distributions are investigated. The ion energy distributions at the powered electrode mainly consist of either a single peak or they consist of the well known bimodal structure caused by rf splitting. For some source parameter a continuous energy distribution is detected for lower bombardment energies, which is interpreted as the result of scattering of ions with the background gas during their transport to the substrate electrode. The variation of the total flux intensities, the dc bias potentials, and the plasma potentials are evaluated and are interpreted as a result of mode transitions of the helicon plasma. The ion angular distributions are unstructured and show angular widths in the range between 2° and 3° full width at half-maximum. Some aspects concerning the application of the source for semiconductor etching processes are discussed.
Deposition of silicon dioxide films using the helicon diffusion reactor for integrated optics applications
Authors: Giroult-Matlakowski G. , Charles C. , Durandet A. , Boswell R. W. , Armand S. , Persing H. M. , Perry A. J. , Lloyd P. D. , Hyde S. R. , Bogsanyi D.
Published: July 2002

Silicon dioxide thick films (1–18 μm) have been deposited at very reasonable deposition rates (20–80 nm/min) with no intentional heating of the substrate (T∼200 °C) using SiH4/O2 plasmas coupled in a new type of plasma reactor: The radio frequency plasma excitation used in the helicon diffusion reactor induces the formation of high-density plasmas (∼1012 cm−3) with low plasma potentials. Three main parameters have been investigated; the total gas flow, the oxygen/silane gas flow ratio, and the magnetic confinement in the diffusion chamber. An in situ control of the refractive index and deposition rate has been obtained and correlated to an ex situ analysis of the deposited films (infrared transmission spectroscopy and chemical etch rate measurements) and the effects of the deposition kinetics on the film properties such as the hydrogen content and the voids fraction have been analyzed.
Low-frequency dynamics of CO/Cu breakdown of Born–Oppenheimer approximation
Authors: Hirschmugl C. J. , Chabal Y. J. , Hoffmann F. M. , Williams G. P.
Published: July 2002

Synchrotron infrared studies of adsorbates on surfaces offer the possibility of probing low-frequency vibrational modes and dynamics at high resolution (1 cm−1, 125 μeV). Extensive experiments have been performed for ordered submonolayers of CO on low index Cu surfaces [(√3×√3)R30° CO/Cu(111), c(2×2) CO/Cu(100) and (1×2) CO/Cu(110)], in the 100–2500 cm−1 (∼12.5–312.5 meV) range. These are the first IR experiments to directly probe the adsorbate-substrate vibrations for this system. In addition, however, several surprising features are observed including the dipole-forbidden hindered rotation and an unexpected broadband absorption. Two theories have been motivated by this work, and will be compared to our experimental results. The first theory is a cluster calculation by Tully, Gomez, and Head-Gordon, which takes into account the breakdown of the Born–Oppenheimer approximation and predicts lifetimes and frequencies of the vibrational modes for CO/Cu(100). Another Drude-based theory, proposed by Persson, considers the coupling of the conduction electron current to the vibrations of the adsorbates, accounting for the observation of both the broadband absorption and dipole-forbidden peak.
Dissociative chemisorption of oxygen on the Ru(001) surface: Spectroscopic identification of precursor intermediates at low surface temperatures
Authors: Mitchell William J. , Xie Jun , Lyons Kevin J. , Weinberg W. Henry
Published: July 2002

The adsorption of oxygen on the Ru(001) surface at 30 K has been investigated by high-resolution electron energy loss spectroscopy. Dissociative chemisorption occurs up to the saturation atomic coverage [ν⊥(Ru–O)=595 cm−1], after which a small amount of a molecularly chemisorbed peroxide species was isolated [ν(O–O)=790 cm−1]. After saturation of these atomic and molecularly chemisorbed states, physically adsorbed oxygen with a vibrational frequency close to the gas phase value of 1555 cm−1 was observed. The physically adsorbed oxygen was found to exhibit a resonance in the electron scattering cross section at an electron beam energy of about 5.5 eV. Heating the surface to 55 K leads to desorption of the physically adsorbed overlayer. The peroxide species, on the other hand, dissociates between 100 and 450 K. Although the initial precursors to dissociative chemisorption were not isolated, the peroxide identifies an intermediate precursor state, and the physically adsorbed oxygen identifies an extrinsic precursor state.
Two-dimensional self-consistent fluid simulation of radio frequency inductive sources
Authors: DiPeso G. , Vahedi V. , Hewett D. W. , Rognlien T. D.
Published: July 2002

The two-dimensional (R−Z) electromagnetic code fmrz has been used to model inductive sources self-consistently in time. The code models an argon plasma with momentum transfer, excitation, and ionization as electron–neutral reactions and momentum transfer for the ion–neutral reactions. The electrons and ions are treated as fluid species and a reduced set of Maxwell’s equations is used to advance the electromagnetic fields. The set of equations used in fmrz is not subject to typical numerical constraints present in many time dynamic codes, allowing one to choose appropriate time and space scales to resolve only the frequencies and scale lengths of interest. The model retains nonlinear driving terms which give rise to a ponderomotive force that distorts the density profile. Density and power profiles show the physical effects of various terms in the equations. Trends in average density and temperature compare well with an analytic model and other simulation models.
Structuring of various materials using cluster ions
Authors: Henkes P. R. W. , Krevet B.
Published: July 2002

The sputtering yield of accelerated CO2 cluster ions impinging on surfaces of various materials is investigated. For copper, it varies proportionally to the second power of the energy between 156 and 260 keV. The rate of erosion for different target materials varies by two orders of magnitude from tungsten to polymethylmethacrylate. Diamond is eroded fairly quickly, while aluminum is eroded less than corundum (Al2O3). No simple correlation of the sputtering yield on the bulk properties of target materials is found. For copper, the angular distribution of sputtered material is measured and found to be following a roughly cosine distribution. By using masks, different microstructures have been produced in cobalt–samarium magnets, diamond, and glass.
Hot scanning tunneling microscope study of B type step edges and small silicon islands on Si(001)
Authors: Pearson Chris , Krueger Michael , Curtis Robert , Borovsky Brian , Shi Xin , Ganz Eric
Published: July 2002

We have used a scanning tunneling microscope to image step edges as well as small Si islands on the Si(001)-2×1 reconstructed surface at temperatures up to 700 K. We count the changes in the step edge configuration and extract activation energies for the dominant processes. We also observe fluctuations in Si island size at rates that are higher than those we observe on step edges. To aid visualization of the dynamics, we display consecutive images of fluctuating islands and step edges as movies.
Magnetic and structural properties of ultrathin Mn and Fe films on Ir(111)
Authors: O’Brien W. L. , Tonner B. P.
Published: July 2002

We have measured the structural and magnetic properties of ultrathin Mn and Fe films grown on Ir(111). For Mn films a (1×1) to (√3×√3) phase transition is observed by low energy electron diffraction (LEED) at 4 monolayers coverage. The average magnetic moment in the Mn films was measured by both Mn 3s photoemission and Mn L2,3 absorption. The average Mn moment was found to decrease for thicker films. This decrease in the moment continues smoothly through the (1×1) to (√3×√3) phase transition, showing that the change in magnetic moment is not due to the phase change. A simple model, which assumes an enhanced moment in a single layer, explains the decrease in the magnetic moment well. For Fe films, changes in the LEED patterns at 5 ML are consistent with a face-centered-tetragonal to body-centered-cubic (fct to bcc) phase transition. Ferromagnetic ordering in the Fe thin films is observed by x-ray magnetic circular dichroism (XMCD) for films thicker than 5 ML. The onset of ferromagnetic ordering at 5 ML is due to the fct to bcc phase transition. The Fe L2,3 XMCD intensity is saturated at 10 ML showing that the entire film is magnetized and that no magnetic dead layer is present.
Energetic condensation: Processes, properties, and products
Authors: Colligon John S.
Published: July 2002

When film deposition is accompanied by bombardment by low energy (less than a few 100 eV) particles, the resulting film nucleation, growth, stress content, adhesion, density, composition, morphology, and crystal structure may be significantly altered. Current methods for providing the energy-assisted conditions for film growth are described. Recent selected results are given demonstrating all the above features together with a discussion of the fundamental reasons for the improved film quality. Selected applications of the novel materials that can now be created on various substrates to improve friction, wear, corrosion resistance, and optical qualities are presented. The review concludes with an outline of future trends.
Temperature dependent vacancy concentrations on InP(110) surfaces
Authors: Heinrich M. , Ebert Ph. , Simon M. , Urban K. , Lagally M. G.
Published: July 2002

The thermal formation of P monovacancies is studied as a function of time and temperature between 293 K and 480 K on InP(110) surfaces using scanning tunneling microscopy. The formation rate of the P vacancies increases up to 435 K. Above 435 K both the vacancy formation rate and the maximum vacancy concentration decrease. The highest vacancy concentration is 5×1012 cm−2. Annealing the samples at temperatures higher than 480 K reduces the vacancy concentration to values observed at room temperature. The results are explained in terms of two activated mechanisms with different rates: thermal vacancy-adatom pair formation with subsequent desorption of phosphorus from the surface and anion outdiffusion from the bulk.
Chemical vapor deposited TiCN: A new barrier metallization for submicron via and contact applications
Authors: Eizenberg M. , Littau K. , Ghanayem S. , Liao M. , Mosely R. , Sinha A. K.
Published: July 2002

High quality chemical vapor deposited (CVD) TiCN films were produced in a single wafer reactor using a metalorganic precursor (tetrakisdimethylamino titanium). The films have excellent step coverage (≳80%) over high aspect-ratio contacts as well as a very low particle level. These properties are obtained because the films were deposited under surface-reaction controlled conditions; the measured activation energy is 0.9 eV. The stress levels of the films are relatively low, below 5×109 dyn/cm2 compressive. The films also show good barrier properties against Al, Cu, and WF6 attack, that are attributed to their amorphous component, to the high C content of the films, and to the high step coverage. The electrical properties of the CVD TiCN films were evaluated at the via level, and the resistance contribution was shown in many cases to be comparable to that of sputtered TiN. These properties make this material a suitable barrier material for contact and via applications in sub-0.5 μm devices.
Real-time spectroscopic ellipsometry monitoring of Si1−xGex/Si epitaxial growth
Authors: Pickering C. , Hope D. A. O. , Carline R. T. , Robbins D. J.
Published: July 2002

Real-time spectroscopic ellipsometry has been used to monitor oxide desorption and Si1−xGex/Si multilayer growth. A database of dielectric function spectra at the growth temperature has been determined for x=0.07, 0.11, 0.15. Real-time data obtained during growth have been analyzed using spectral fitting techniques to determine composition at selected growth times, and by using time-dependent data to determine optical constants and growth rates. The pseudosubstrate approximation has been used to determine layer parameters from the growing surface and information on interface widths obtained.
Plasma-induced gate-oxide charging issues for sub-0.5 μm complementary metal–oxide–semiconductor technologies
Authors: Stamper A. K. , Lasky J. B. , Adkisson J. W.
Published: July 2002

Gate dielectric charging issues which occurred during the development of IBM’s 200 mm wafer sub-0.5μm 16-Mbyte dynamic random access memory (DRAM) and logic processes are discussed. Using polysilicon conductor antenna structures and fully integrated DRAM test sites, we investigated three reactive ion etching (RIE) processes: SiO2, Si3N4, and polysilicon etch; argon sputter; and tetraethylorthosilicate (TEOS) and silane-based plasma enhanced chemical vapor deposition (PECVD). The most charging-sensitive processes were SiO2 RIE, argon sputter, and phosphorus-doped TEOS-based PECVD. In particular, we show that gate-oxide degradation is caused by gate dielectric tunneling current throughout plasma exposure and that it can be modulated by systematically changing the plasma properties.