bluuebunny/crossref_metadata_2025 huggingface dataset:
A Generalized Random Variable Approach for Strain-Based Fatigue Reliability Analysis
Authors: Zhao Jie , Tang Jun , Wu Han C.
Published: July 2002

A new reliability technique for strain-based fatigue life design is developed in this paper. An empirical mean stress modified strain-life equation is used as performance function, in which: material property parameters, as fatigue strength coefficient and fatigue ductility coefficient; and mean stress and applied strain are taken as random variables. A major feature of this work is that, in the performance function, the terms involving material property parameters are combined into one generalized random variable as “capacity,” and the terms involving mean stress and applied strain are combined into another generalized random variable as “demand.” The limit state is then analyzed by using the interference technique to evaluate the reliability under a specified life. Another significant feature is that in order to meet the need of fatigue life design application, for a given cyclic strain history, a numerical method is developed to inversely search the life when certain reliability is specified. Two numerical cases are presented to demonstrate the method. [S0094-9930(00)01202-6]
High Resolution XPS Spectrum of Calcite (CaCO3)
Authors: Baer D. R. , Moulder J. F.
Published: July 2002

Calcite is a common component of soil and a natural mineral sometimes found in the form of large high quality single crystals. The interactions of calcite with ions in groundwater affect their transport in the environment. Consequently, understanding the surface chemistry of calcite is important for environmental remediation research. The measurements reported here were conducted to provide high quality valence band and core level spectra of the clean calcite surface and for comparison with data collected on an older instrument with lower spatial and energy resolution. A single crystal was broken in vacuum to expose the (101¯4) plane of rhombohedral calcite (CaCO3) for XPS analysis. Survey and multiplex spectra were collected under standard operating conditions with a Perkin Elmer Physical-Electronics 5600 spectrometer using monochromatic Al Kα x rays. An electron flood gun was used to control surface charging during the measurements.
Palladium Chloride (PdCl2) by XPS
Authors: Militello Maria C. , Simko Steven J.
Published: July 2002

X-ray photoelectron spectroscopy (XPS) spectra of palladium chloride (PdCl2) are presented. Ground PdCl2 powder was pressed into Al foil and analyzed with a Surface Science Instruments SSX-101 M-Probe ESCA instrument using monochromatized Al Kα x rays. Spectra include a survey scan, the Pd 3d, 3p, 3s, 4s, 4p regions, the Cl 2p, 2s, and valence band regions, and the Pd MNN and MNV Auger transitions.
Analysis of Polystyrene (PS) by XPS
Authors: Girardeaux Christophe , Pireaux Jean-Jacques
Published: July 2002

We report x-ray photoemission spectra of polystyrene (PS). XPS spectra were measured with the SSI, SSX-100 model, using monochromated Al Kα x-rays. We present the survey spectrum (binding energy range of 0–1100 eV) and a narrow spectrum of C 1s. The polymer is used as a reference to study the influence of PS surface modification by rf plasma for biochemical applications.
Transient plasma-induced emission analysis of laser-desorbed species during Cl2 plasma etching of Si
Authors: Choe Jae Young , Fuller N. C. M. , Donnelly Vincent M. , Herman Irving P.
Published: July 2002

The surface during the etching of Si in a Cl2 inductively-coupled plasma (ICP) was analyzed by laser desorption (LD), followed by detection of the desorbed species by monitoring the transient changes by plasma-induced emission (PIE). Optical emission from Si, SiCl, SiCl2, and possibly other species was detected in situ using this LD-PIE method as a function of rf power, substrate bias, and pressure. The surface coverage of chlorine was determined by normalizing the LD-PIE signal by either of two ways: by the electron density, as measured by microwave interferometry, or by using the background PIE signal. Little change in surface coverage was observed as the ion density was changed by varying the rf power supplied to the ICP, confirming the observation made using laser-induced fluorescence (LIF) detection (LD-LIF). The LD-PIE signal is related to the density of species desorbed from the surface and subsequently excited by electrons. LD-PIE analysis of the surface is more versatile than LD-LIF—sometimes it can detect the desorbed species while LD-LIF cannot. Still, it requires calibration to account for the electron collision-induced excitation of the laser-desorbed species.
Observation of switching phenomena in discontinuous gold films by liquid-crystal technique
Authors: Dey S. K. , Dick G. D.
Published: July 2002

Metallic discontinuous films are known to exhibit multivalued conductivity states which are dependent on the applied voltage and deposition conditions of the films. By using cholesteric liquid crystal with controlled heating the growth of conduction passages in a discontinuous gold film is shown under magnifications of 100 and 400. By using a gap width of 12.5 μm and gold electrodes, the I–V characteristic is found to be ohmic in both low-and high-resistance states at low voltages (<3 V). The resistance increases by over five orders of magnitude after the first switching potential. A reversal to the low state then occurs at a higher potential. No evidence of the formation of a single thermal current filament during “turn-on” operation is found. The influence of deposition parameters on switching is indicated and an optimum set of values is presented.
Structural and mechanical properties of TiC and Ti–Si–C films deposited by pulsed laser deposition
Authors: Phani A. R. , Krzanowski J. E. , Nainaparampil J. J.
Published: July 2002

TiC and Ti–Si–C films have been deposited by pulsed laser deposition at substrate temperatures ranging from room temperature to 600 °C onto (111) silicon wafers and 440C stainless steel substrates. X-ray diffraction, x-ray photoelectron spectroscopy, and electron microscopy were employed for structural and compositional evaluation of the films, and nano-indentation hardness testing and pin-on-disk wear tests were used to evaluate the mechanical and tribological properties. All the TiC films were highly crystalline except the one deposited at room temperature, whereas for the Ti–Si–C films the degree of crystallinity increased with temperature, ranging from amorphous for the room temperature deposit to about 50% crystalline at 600 °C. The hardness of the TiC films was relatively constant with deposition temperature at about 25 GPa, whereas the hardness of the Ti–Si–C films increased with deposition temperature from 11 to 33 GPa. The temperature dependence of the hardness is attributed to the degree of crystallinity and the extent of phase separation in the Ti–Si–C films. The wear test data showed good results for all films up to the tested limit of 10 000 cycles at 1 N load.
Determination of electron temperature, atomic fluorine concentration, and gas temperature in inductively coupled fluorocarbon/rare gas plasmas using optical emission spectroscopy
Authors: Schabel M. J. , Donnelly V. M. , Kornblit A. , Tai W. W.
Published: July 2002

Recent advances in the interpretation of optical emission spectra from plasmas have made it possible to measure parameters such as electron temperature (Te), relative electron density, and gas temperature (Tg) with this nonintrusive technique. Here we discuss the application of trace rare gas optical emission spectroscopy (TRG-OES), optical actinometry, and N2 rotational spectroscopy to determine Te, relative electron density, fluorine atom concentration, and Tg for fluorocarbon/Ar plasmas in an inductively coupled reactor. Various etch processes, containing mixtures of a carrier gas, C2F6, and C4F8, were evaluated as a function of pressure and flowrate. Ar, Kr, and Ne were used individually or were mixed to comprise the carrier gas. In the case of TRG-OES and optical emission actinometry, a mixture containing equal parts of He, Ne, Ar, Kr, and Xe (∼1% ea.) was added. A method for correcting excitation cross sections is introduced for cases when radiation trapping affects the emission of a rare gas (Ar) that is present at high concentrations. Experiments revealed that Te can be controlled through the choice of carrier gas: Ne tends to increase Te and Kr tends to decrease Te relative to Ar. This phenomenon was verified qualitatively with a simple zero-dimensional energy balance model. Additional measurements revealed that the absolute atomic fluorine concentration, determined from calibrated F-to-Ar actinometry ratios, is roughly 20% of the total gas at 5 mTorr, and decreases to 5% at 60 mTorr. The gas temperature in the Ar-carrier plasma was measured to be ∼1200 K and was found to be insensitive to pressure whereas Tg in Kr and Ne carrier gas plasmas increased from 1500–1900 K and 700–1500 K, respectively between 5 and 30 mTorr.
Faraday cup detector array with electronic multiplexing for multichannel mass spectrometry
Authors: Scheidemann A. A. , Darling R. B. , Schumacher F. J. , Isakharov A.
Published: July 2002

A Faraday cup detector array (FCDA) and electronic multiplexing circuit have been developed for position sensitive ion beam detection. The entire FCDA always remains open to intercept the incident ion beam flux, and each cup is periodically and sequentially discharged through the electronic multiplexer. This produces true multichannel ion beam detection since none of the incident ion beam flux is lost, as is the case for scanning position sensitive detectors, and higher sensitivity detection is thus obtained. The FCDA consists of a one-dimensional or two-dimensional array of individual cups which are electrostatically isolated from each other by means of an intervening ground conductor, with resulting fill factors F of 58% to 85%. Each cup acts as a charge collector and integrator which is quickly discharged during the readout to create a time-multiplexed output signal that gives the position distribution of the ion beam. When N cups are sequentially scanned and read out, the ion collection efficiency is F(1−r/N), where r is the fraction of a clock cycle that is used for resetting the integrating capacitor. With a typical r=0.2, a 64 element array thus provides an ion collection efficiency of better than 0.997F. The device measures absolute ion currents, and has a wide dynamic range from less than 1 pA to more than 100 nA with less than 70 dB of cross talk between cups. The integration of the electronic multiplexer with the FCDA allows the combined unit to operate within a vacuum chamber by means of only a six-pin feedthrough. The FDCA and electronic multiplexer have been used as a position sensitive ion detector in a compact mass spectrometer to produce better than 1 amu resolution over a 200 amu span with a sensitivity of less than 0.8 pA at a 10:1 signal-to-noise ratio.
Characterization of platinum films deposited by focused ion beam-assisted chemical vapor deposition
Authors: Telari K. A. , Rogers B. R. , Fang H. , Shen L. , Weller R. A. , Braski D. N.
Published: July 2002

This work presents results from the characterization of ion-assisted chemical vapor deposition of platinum from trimethyl–methylcyclopentadienyl–platinum (C9H16Pt). Films were deposited in squares ranging from 50 to 200 μm on a side using a focused ion beam system. The effects of Ga+ ion flux and precursor flux on the deposited films’ composition and resistivity were determined. Films were characterized using atomic force microscopy, Rutherford backscattering spectrometry, and Auger electron spectroscopy. Results show that increasing precursor flux at constant ion flux increases Pt and C, but decreases Ga content of the film. Increasing ion flux at constant precursor flux increases Pt content, while decreasing C content of the films. Resistivity did not depend on the thickness of 50–200 nm thick films. Resistivity was shown to follow C content, with films with lower C content having lower resistivity.
Gaseous mixture flow through a long tube at arbitrary Knudsen numbers
Authors: Sharipov Felix , Kalempa Denize
Published: July 2002

The mass flow, heat flux, and diffusion flux of rarefied gas mixture through a tube caused by gradients of pressure, temperature, and concentration were calculated over a wide range of the Knudsen number on the basis of the kinetic equation. The thermodynamic fluxes are presented in the form that allows us to prove the Onsager relations and then to reduce the number of kinetic coefficients determining the solution down to six. The numerical values of the kinetic coefficients are tabulated and the velocity profiles are given in figures.
Thin Film Atomic Hydrogen Detector
Authors: Macfarlane J. C.
Published: July 2002

A means of detecting atomic hydrogen by conductance measurements on molybdenum trioxide films has been developed. The technique is applicable to quantitative measurements and atom flux levels of the order 2×1015 m−2 sec−1 are detectable. The use of the detector to evaluate the performance of an rf discharge dissociator is described.
Ion sputtering of alloys
Authors: Pickering H. W.
Published: July 2002

Based on an idealized model of ion sputtering of a binary alloy which consists of an easy-to-sputter and a difficult-to-sputter metal, a mass transfer calculation was carried out. Solutions for both the initial transient and subsequent steady-state concentration profiles, and the excess (sputtered) amounts of the easy-to-sputter component were obtained. For typical sputtering rates it is found that the sputtering enhanced diffusivity must be ≫10−17 cm2 s−1 before an interdiffusion zone can form. The analysis is of special significance since it shows that even when the alloy components have greatly different sputtering tendencies: (a) nonpreferential sputtering is always obtained after an induction period, the latter of which depends on the effective alloy interdiffusivity and the overall rate of sputtering and (b) the attainment of nonpreferential sputtering requires that the new surface continuously readjusts its composition in the direction of enriching in the difficult-to-sputter component. Similar results may be expected for oxides.
UHV facility for metal–semiconductor thin-film studies
Authors: Crider C. A. , Poate J. M. , Rowe J. E.
Published: July 2002

A unique multifunction apparatus consisting of a surface analysis chamber operating at 1×10−8 Pa connected by a 4.5-m-long beam line to a 3.75-MeV Van de Graaff accelerator operating at 1×10−4 Pa is described. The bakeable, all-metal sealed beam line contains collimating, blocking, focusing, and steering facilities for the MeV ion beam and is differentially pumped with a turbomolecular pump to 4×10−7 Pa after a mild (100°C) bakeout. The chamber contains surface preparation equipment, a double-pass CMA for AES and ELS, and facilities for metal evaporation at P?8×10−7 Pa from an electron-beam source while simultaneously performing MEED. A specially designed manipulator allows samples to be cleaned, annealed, and characterized prior to in situ evaporation. The resulting metal–semiconductor couple may also be annealed in situ and characterized by AES, MEED, and Rutherford Backscattering Spectroscopy.
Dissolution of amorphous silicon into solid aluminum
Authors: Scranton R. A. , McCaldin J. O.
Published: July 2002

The rate of dissolution of amorphous Si into solid Al is measured at temperatures below 400°C. The dissolution rate is found to be much faster than predicted by a simple model of the transport of Si through Al. This result is related to defects in the growth of epitaxial Si using the solid-phase epitaxy process.
Electrothermal model of switching in amorphous silicon films
Authors: Dey S. K.
Published: July 2002

The pulse repetition frequency dependence of the delay time, td, in amorphous silicon films produced by electron-beam evaporation in a Ti–Si–Ti sandwich structure has been found to give two opposite trends. Below about 1 kHz, td increases as the frequency is increased but is independent of the pulse duration. Above 1 kHz, td decreases with frequency and is also reduced in magnitude by increasing the pulse width. In this paper, an electrothermal mechanism of switching has been used to explain the above phenomenon satisfactorily. The predictions of the model as regards td decreasing with increasing over-voltage and increasing film thickness, the threshold voltage exhibiting a half-power law relationship with thickness and its temperature dependence, and the effect of space–charge injection around the electrodes are confirmed by experiments. Finally, a view of switching combining both thermal and electronic elements is presented.
Study of thin Nb oxide films
Authors: Karulkar Pramod C. , Nordman James E.
Published: July 2002

Niobium films oxidized to thicknesses less than 30 Å by using different oxidation techniques (e.g. thermal, dc glow discharge, and rf glow discharge) were studied by XPS. Chemical shifts in the binding energies of Nb 3d (3/2) and Nb 3d (5/2) levels were used to identify the various oxides of Nb. Niobium films oxidized by thermal or dc glow discharge oxidation showed an outermost layer of Nb2O5. A pure Nb signal could be seen when the oxide films were thin. Suboxides could not be seen directly in XPS data. The composition of the oxide films produced by an rf glow discharge oxidation was found to depend on the rf peak to peak voltage and under certain conditions the XPS spectra clearly showed the existence of NbO. A discrepancy was observed between the oxide thicknesses estimated from the XPS data and the relative values of resistances of Nb–Nb oxide–Pb tunnel junctions fabricated by using these oxide films as barriers. The results are briefly discussed in terms of the difference in the oxidation processes and their importance in junction fabrication.
Polymeric mandrels—supersmooth finish by an infusion process
Authors: Duchane D. V.
Published: July 2002

Extremely smooth surfaces (less than 1 μm maximum defect size) have been produced on acrylic polymer rods by an infusion process. The technique involves bathing the rod in a mixture of a solvent and a diluent, a nonsolvent for the polymer. This causes the rod to soften and permits limited flow and leveling of its surface. The solvent is then gradually displaced from the bath by additional diluent. As this occurs, the surface of the rod becomes rigid once more, but now with a defect-free finish. Acetone may be used as the solvent. The smoothest surfaces have been obtained using a mixture of 50% water and 50% polyethylene glycol with a molecular weight of about 4000 as the diluent.
Effects of argon pressure and substrate temperature on the structure and properties of sputtered copper films
Authors: Craig S. , Harding G. L.
Published: July 2002

The influence of substrate temperature (20 °– 450 °C) and sputter gas pressure (0.5–100 Pa) on the evolution of coating morphology during growth of magnetron deposited copper films has been investigated for film thicknesses up to 10 μm. Classification of films according to structure and surface topography yields a structure zone model with substrate temperature and argon gas deposition pressure dependence which is in basic agreement with a general model proposed by Thornton. The structural variations can be accounted for in terms of the interaction of various coating atom condensation processes and effects associated with increased water vapor partial pressure and the formation of intrinsic stress in the films.
Chlorine and hydrogen chloride on clean and oxygen-covered Fe(100): Bonding and reactions
Authors: Debnath N. C. , Anderson Alfred B.
Published: July 2002

An ASED molecular orbital study of the binding, structures, and reactions of Cl, Cl2, HCl, and HCl+O on 4–21 atom clusters in the Fe(100) structure has been made. Cl2 bonds dissociatively (as seen by Dowben and Jones in LEED and TDS studies). Coverage is limited by σ*p repulsions; orbitals of this symmetry are occupied by electron donation from iron. We find Cl favors onefold and twofold sites and discuss this unexpected result with perturbation theory. It is suggested that with decreased backbonding from iron to Cl the fourfold site can become favored. There is an absence of experimental or theoretical evidence supporting orbital reoccupations to favor the high-coordinate site. HCl dissociation is found to occur with a barrier on the surface that is roughly half the gas phase binding energy, leading to stable products. The HCl+O→Cl+OH reaction on the surface is found to be structure sensitive and the reasons are interpretable from molecular orbital theory.
A model for atomic mixing and preferential sputtering effects in SIMS depth profiling
Authors: King B. V. , Tsong I. S. T.
Published: July 2002

The development of altered surface layers due to preferential sputtering can be modeled by an algorithm based on the diffusion theory of atomic mixing using a depth-dependent diffusion coefficient. Application of the model to typical SIMS depth profiles of buried layers indicates that the effects of atomic mixing and preferential sputtering can be separated by analysis of the shift and broadening of the measured peaks.
Revised structure zone model for thin film physical structure
Authors: Messier R. , Giri A. P. , Roy R. A.
Published: July 2002

Thin films prepared under conditions of low adatom mobility are characterized by a highly anisotropic physical structure with a wide range of systematically varying column and void sizes. The structure zone models, previously developed to classify the larger sized physical structures, are revised to account for the evolutionary growth stages of structure development as well as the separate effects of thermal- and bombardment-induced mobility. The zone T introduced by Thornton is shown to be a subzone within zone 1.
Vibrational relaxation in H2 molecules by wall collisions: Applications to negative ion source processes
Authors: Karo A. M. , Hiskes J. R. , Hardy R. J.
Published: July 2002

In the volume of a hydrogen discharge, H2 molecules, excited to high vibrational levels (v″>6), are formed either by fast-electron collisions or from H+2 ions that are accelerated across the discharge-wall potential that undergo Auger neutralization prior to impact with the discharge chamber wall. We have used computer molecular dynamics to study the deexcitation and reexcitation of vibrationally excited H2 molecules undergoing repeated wall collisions. The initial translational energies range from thermal to 100 eV and the initial vibrational states range from v″=2 to v″=12. The average loss or gain of vibrational, rotational, translational, and total molecular energies and the survival rates of the molecules have been evaluated. At thermal energies vibrational deexcitation is the predominant process, and a consistent picture emerges of rapid energy redistribution into all the molecular degrees of freedom and a slower rate of loss of total molecular energy to the wall. At higher translational energies (1–100 eV) a substantial fraction of the molecules survives with large (v″>6) vibrational energy. This vibrational population provides a contribution to the total excited vibrational population comparable to that from the fast-electron collision process. Implications of these results for negative ion generation will be discussed.
A simple ionization gauge for use in a magnetic field
Authors: Stansfield B. L. , Bergevin B. , Larsen J. M.
Published: July 2002

A simple ionization gauge is described which can be used to measure fast pressure changes in a weak plasma environment in a magnetic field. The gauge has a conventional triode structure and hence can be readily constructed using commercial components. The gauge tested is, however, much less sensitive than a standard Bayard–Alpert gauge. The gauge is, however, relatively insensitive to an applied magnetic field of up to 5 kG, and will tolerate a large variation in the direction of the magnetic field.
Poisonous gas effects on the emission of oxide-coated cathodes
Authors: Itoh S. , Yokoyama M. , Morimoto K.
Published: July 2002

A study of the influence of various gases on the emission of oxide-coated cathodes is described. Particularly selected were SO2 and NO2, which are closely related to air pollution, and Cl2 gases. For comparison purposes, the poisonous effects of N2, CO2, H2O, O2, CO, H2, and Ar, which are the main components of natural atmosphere, were also examined. To study the influences of gases on the emission of oxide-coated cathodes and on oxide materials in more detail, the poisoned state of the contaminated cathode was analyzed using secondary electron microscopy and Auger electron spectroscopy. The influence of contaminated gases on the emission of the cathode in the carbonate state prior to activation was also studied.
Effects of oxygen in ion-beam sputter deposition of vanadium oxide
Authors: Chain E. E.
Published: July 2002

Oxides of vanadium, 190–310 nm thick, were deposited by ion-beam sputtering of a metallic target. The ion beam consisted of an argon–oxygen mixture where the oxygen percentage was varied from 10% to 50%. Spectrophotometry was used for infrared optical characterization, while x-ray diffractometry and scanning electron microscopy were used to examine coating structure. Results show that as the oxygen fraction of the sputtering gas is increased, the crystallography evolves from a face-centered-cubic vanadium oxide to a mixed oxide phase containing VO2 in which there is a degree of preferential grain orientation. Increase of the oxygen content above 25% leads to a mixed oxide phase containing V2O5 with a structure of long, randomly oriented grains. Changes in optical reflectance and transmittance data, which accompany the structural changes, are presented and discussed.
Industrial deposition of binary, ternary, and quaternary nitrides of titanium, zirconium, and aluminum
Authors: Knotek O. , Münz W. D. , Leyendecker T.
Published: July 2002

Improved wear behavior compared to chemically vapor deposited (CVD) and physically vapor deposited (PVD) TiN coatings have been found with (Ti,Al)N, (Ti,Zr)N, and (Ti,Al,V)N coatings using high-speed steel and cemented carbide substrates. High-speed drills coated by (Ti,Al)N films, produced from Ti:Al 50:50 at. % targets revealed in certain cases up to three times better performance than conventionally TiN ion plated tools. In the case of cemented carbides the flank and crater wear could be improved considerably also up to three times compared to CVD TiN/TiC depending on cutting conditions. Basic correlations between process and film characteristics of new multicomponent hard coating have been established. Planar magnetron sources and powder metallurgically prepared targets in an industrially useful ion plating deposition process have been developed and proved under production conditions. The first part of the paper describes the basic research and development of new coating materials. The second part involves the industrial application in batch type and in-line PVD coaters using the sputter ion plating process with magnetron sources in double-cathode arrangements. Finally, wear tests of coated cutting tools, conducted through by different institutions, show the outstanding wear behavior of the new multicomponent coatings.
Deposition of carbon, deuterium, and metals on the wall and limiters of the Tokamak Fusion Test Reactor
Authors: Wampler W. R. , Doyle B. L. , Lee S. R. , Pontau A. E. , Mills B. E. , Causey R. A. , Buchenauer D. , Dylla H. F. , Ulrickson M. A. , LaMarche P. H.
Published: July 2002

Following a two-year operational period the Tokamak Fusion Test Reactor (TFTR) graphite fixed bumper limiter has been examined by a variety of methods. The areal density of metals was mapped in situ by beta backscattering. Several tiles were examined in detail by nuclear-reaction analysis, Rutherford backscattering, and proton-induced x-ray emission to measure areal densities of deuterium and impurities. Some areas of the limiter were found to be covered by deposited material several microns thick. Other areas where the incident plasma flux is higher were much cleaner. Long-term collection coupons were also examined to characterize deposition on the wall. From these results the total amount of deuterium on the limiter and wall in TFTR is estimated to be ∼1.3×1024 atoms. The implications of this for wall-pumping effects and future tritium inventory are discussed.
A spherical ionization gauge for use in a high magnetic field
Authors: Ogiwara N. , Maeno M.
Published: July 2002

This paper describes a new type of hot filament ionization gauge for measurement of neutral gas density in a high magnetic field. The notable feature of the gauge is its spherical symmetry. The ion current varies linearly with the pressure from 10−4 to 1 Pa for N2 and Ar. The sensitivity changes by no more than +20% in a magnetic field of up to 1.2 T. The main reasons for this small change in the sensitivity are as follows: (i) The probability of ionization of gas molecules is almost independent of a high magnetic field, because the spherical symmetry causes electrons to be emitted from the filament to the region in which the electric field is almost parallel to the magnetic field; (ii) the probability of ion collection is independent of a magnetic field.
Reactively sputtered titanium boride thin films
Authors: Blom H-O. , Larsson T. , Berg S. , Östling M.
Published: July 2002

Thin films of titanium boride were deposited by reactive sputtering in a mixture of argon and 6% diborane. The use of reactive sputtering makes it possible to deposit films with different compositions. The overall composition of the films was determined by Rutherford backscattering. The crystallization of the films and the variation in resistivity with the annealing temperature have been studied. The minimum resistivity was obtained for stoichiometric TiB2. It was confirmed by both Rutherford backscattering and Auger depth profiling that titanium boride prevents reactions between silicon and aluminum up to temperatures slightly above 600 °C. Structures with TiB2 acting as a diffusion barrier between silicon and aluminum, and a more sophisticated metallization structure also containing a thin titanium layer for silicide formation during heat treatments, have been studied.
The effects of copper underlays on the stability of gold thin films during isothermal annealing
Authors: Kim J. Y. , Hummel R. E. , DeHoff R. T.
Published: July 2002

A study was undertaken to investigate the influence of a copper barrier layer on gold thin-film metallizations. It was found that Au/Cu composite films form holes in gold films during annealing for 1 h in air at temperatures between 300 and 500 °C. These holes are partially filled with copper oxide (CuO). The copper underlays which have a small tendency towards oxidation do not prevent grain growth of gold during annealing. The gold films in as-deposited Au/Cu composite films have a (111) preferred orientation parallel to the substrate which is retained after annealing regardless of the annealing temperature. The density of holes in Au/Cu composite films stays nearly constant with annealing time, at 400 °C in air, while the area fraction of holes increases with annealing time in a near parabolic manner.
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u ellipsometry as a diagnostic of thin-film growth: Studies of amorphous carbon
Authors: Collins R. W.
Published: July 2002

Amorphous carbon (a-C:H) thin-film growth, surface modification, and etching have been studied using in situ ellipsometry. Accurate values of the film thickness, deposition or etch rate, and bulk optical functions, the latter providing information on bonding configurations, can all be deduced from real time measurements during film growth or etching. Substrate modification and film–substrate reactions that occur in the initial stages of film growth upon igniting the deposition plasma or ion beam can be detected and characterized at the monolayer level. Such information is not easily accessible to ex situ measurements. In addition, ellipsometry provides monolayer-level detection of changes in the near-surface bonding. Transitions between polymer- or diamondlike and graphitic bonding caused by inert and reactive gas plasma exposure can be observed. Finally, the applicability of in situ ellipsometry is demonstrated for mapping preparation parameter space according to specific deposition regimes or film properties.
The influence of microstructure on stress state of sputter deposited chromium nitride films
Authors: Fabis P. M. , Cooke R. A. , McDonough S.
Published: July 2002

Chromium nitride films were deposited on glass and vitreous carbon substrates using reactive direct current (dc) planar magnetron sputtering. Single-phase CrN films had homogeneous microstructures composed of columnar grains with a moderate defect density of uniform arrangement and compressive stresses up to (−) 14 GPa. The dual phase CrN+Cr2N films had asymmetric grains, lower structural homogeneity, a high defect density of random arrangement, and a stress range from tensile (+) 2.15 GPa to compressive (−) 1.14 GPa. Intercrystalline and intracrystalline defects contributed to the stresses observed in the films. Generally, the synergistic effects of deposition conditions promoting high normalized energies (energetic particle bombardment of the film) produced microstructurally uniform, hard coatings which were highly stressed (compressive) with low resistivities.
Surface chemistry of monolayer metallic films on Re(0001) and Mo(110)
Authors: He J.-W. , Shea W.-L. , Jiang X. , Goodman D. W.
Published: July 2002

The overlayer growth of Fe, Ni, and Cu on a Mo(110) surface and Fe and Cu on Re(0001) as well as adsorption of D2 and CO on the prepared bimetallic surfaces have been studied in the sample temperature (Ts ) range 115–1500 K, using Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and thermal desorption spectroscopy (TDS). Fe, Ni, and Cu on Mo(110) and Fe and Cu on Re(0001) were found to grow layer by layer upon deposition at Ts =115 K whereas multilayer deposits, upon annealing to Ts >330 K, nucleate into three-dimensional (3D) clusters. The 3D clusters of Fe and Cu are shown by LEED to be epitaxial with respect to the Mo(110) and Re(0001) substrates. Fe at submonolayer coverages is believed to form a strained pseudomorphic superlattice on Mo(110) while similar coverages of Ni on Mo(110) and of Cu on Re(0001) form a superstructure. The results of chemisorption of D2 and CO on the prepared bimetallic surfaces Fe/Mo(110), Ni/Mo(110), and Cu/Re(0001) are presented and discussed. It is shown that these ultrathin metal films exhibit chemisorptive properties quite different from those of the bulk metal.
Characterization of reactive ion etching of glass and its applications in integrated optics
Authors: Ronggui Shen , Righini Giancarlo C.
Published: July 2002

We report characterization of reactive ion etching (RIE) of soda–lime glass under various conditions. Etching rates of glass and photoresist have been measured while using three different reactive gas mixtures, i.e., CHF3/Ar, CF4/O2, and CF4/Ar. Experimental results are presented referring to the RIE fabrication of periodic structures in soda–lime glass ion-exchanged waveguide, starting from gratings which had been recorded in photoresist by holographic techniques.
Modeling and performance characteristics of GaAs quantum well infrared detector structures
Authors: Coon D. D. , Bandara K. M. S. V. , O Byungsung , Choe J.-W. , Francombe M. H. , Lin Y. F. , Takei W. J.
Published: July 2002

Numerous investigations have been reported in recent months confirming the feasibility of infrared detection using optically excited intersubband transitions in GaAs quantum wells in the system GaAs/AlxGa1−xAs. In this paper we present new data on factors such as well width, barrier height, electron exchange interactions, etc. which determine the photoconductive and photovoltaic spectral response of multiquantum well structures, and discuss aspects of parameter control and analysis. Compositional and dimensional control are critically important in determining the type of response (broad or narrow), the wavelength of peak response, optimization at that wavelength, and uniformity across detector arrays. Photoconductive detectors involving transitions between bound states and between bound and free states have both been studied. Also the feasibility of infrared (IR) response in the long-wavelength infrared (LWIR) spectral range (viz. at 9.5 μm) has for the first time been demonstrated for a photovoltaic-type multiple quantum well (MQW) structure. In the case of bound-to-bound type photoconductive detectors we have observed narrow-band (Δλ∼1 μm) IR response at the longest wavelengths yet achieved, i.e., out to 12 μm. Measurements on responsivity, dark current, noise, and detectivity indicate that D* values in excess of 1010 cm Hz1/2 W−1 at 77 K (corresponding to responsivities of about 0.24 A/W) are obtainable at λp of 12 μ and beyond. Our data confirm the role of electron exchange interactions in influencing response wavelength, and indicate that excellent agreement with theory can be achieved if these effects are taken into account.
Mechanisms of the HF/H2O vapor phase etching of SiO2
Authors: Helms C. R. , Deal B. E.
Published: July 2002

In this paper we report on studies of the mechanisms responsible for HF/H2O etching and cleaning of Si surfaces. From these studies we have clearly established that the role of water is to provide a condensed solvent medium for the HF on the surface. Our results, as well as those in the literature, show that if the partial pressures of HF and H2O are too low (or sample temperature too high) condensation does not occur and little or no oxide etching is observed. Based on these ideas and vapor pressure data from the literature, we have developed a detailed model that provides for the calculation of the onset of condensation as a function of wafer temperature and reactant partial pressures. In addition, the model allows determination of the HF concentration in the condensed H2O film. Comparison of etch rates obtained for aqueous etching as a function of HF concentration and vapor phase etching as a function of calculated HF concentration show good agreement.
Annealing and activation of Si implanted InP
Authors: Akano U. G. , Mitchell I. V. , Shepherd F. R. , Miner C. J.
Published: July 2002

The recovery of implant damage, and the activation of Si implanted into InP has been studied over a range of post-implant anneal temperatures from 295 to 1095 K. 600 keV Si+ ions were implanted to doses ranging from 3.6 × 1011 to 2 × 1014 cm−2, and the resultant damage monitored by the Rutherford backscattering/channeling technique. For InP(Zn) and InP(S) wafers of (100) orientation, and undoped metalorganic chemical vapor deposition epilayers grown on InP(Fe) semi-insulating substrates, spontaneous recovery of lattice damage occurs at 295 K. For Si doses ≤ 4 × 1013 cm−2, up to 70% of the initial damage (displaced atoms) annealed out over a period of ≊85 days. The degree of recovery was found to depend on the initial level of damage. Recovery is characterized by at least two time constants; t1 < 5 days and t2 ≊ 100 days. Anneal rates observed between 295 and 375 K are consistent with an activation energy of 1.2 eV. Hall effect measurements following rapid thermal annealing of implanted epilayers, indicate that electrical activation commences at about 850 K; full activation is achieved by 1045 K, this process being characterized by an activation energy of 1.9 eV. The room temperature photoluminescence intensity, which remains almost constant for the unimplanted epitaxial InP over the full rapid thermal annealing (RTA) range, is extinguished after implantation and only recovers to about 18% of the value for the unimplanted reference material. This appears to be associated with the appearance of thermal etch pits which are most pronounced at the highest RTA temperatures and the higher implant doses. These etch pits are almost absent in the unimplanted material subjected to the same RTA cycles.
Excited state formation in low energy Li+–surface collisions
Authors: Andersson D. R. , Behringer E. R. , Cooper B. H. , Marston J. B.
Published: July 2002

The formation of multiple final electronic states in the scattering of ions from surfaces has been used to probe the dynamics of the atom-surface charge transfer process. We present measurements of the formation of the Li(2p) state when scattering 100 and 400 eV Li+ off Cs-covered Cu(001) as a function of the Cs-induced work function change ΔΦ. For an initial energy of 100 eV, the Li(2p→2s) photon emission shows an initial increase as the work function decreases and a maximum at ΔΦ≊−1.7 eV. For 400 eV Li+, the peak in the photon yield is shifted to a larger work function change (ΔΦ≊−2.0 eV) and has an approximately one order of magnitude higher intensity. The charge state fractions of Li+, Li0, and Li− in the scattered flux have been measured as functions of work function changes for a beam energy of 400 eV. At the lowest work functions (i.e., largest ΔΦ), negative ions start to appear. The data are qualitatively reproduced using a model of nonadiabatic, resonant charge transfer, which includes spin, electron–hole pairs, multiple final charge states, and excited neutral atoms. The maxima in the Li(2p) formation versus ΔΦ can partly be explained by competition from negative ion formation.
Two-dimensional mapping of plasma parameters using probes in an electron cyclotron resonance etching device
Authors: Meyer J. A. , Hamers J. S. , Kim G.-H. , Hershkowitz N.
Published: July 2002

Emissive probe measurements of plasma potentials outside the source aperture of an electron cyclotron resonance etching device have shown large radial electric fields in a nitrogen discharge. It is shown that the magnitude of the radial electric field is pressure dependent, decreasing for higher pressures. In addition to radial and axial profiles of the plasma potential, profiles of ion density, electron temperature, and floating potential were measured with Langmuir probes for several cases: Two magnetic-field configurations, with and without an insulating liner in the source, and with and without a wafer stage. It is shown that the plasma potential with the liner present is higher when there is a resonance zone close to the aperture of the source, as opposed to when the resonance zone is farther inside the source.
Multiple jets and moving substrates: Jet Vapor Deposition of multicomponent thin films
Authors: Halpern B. L. , Schmitt J. J.
Published: July 2002

We describe the physical basis of Jet Vapor Deposition (JVD), in which sonic, inert gas ‘‘jets in low vacuum’’ are used as vapor sources for depositing films. A ‘‘multiple jet, moving substrate’’ strategy enables deposition of a wide variety of multicomponent, multilayer and ‘‘host–guest’’ materials generated from metals, semiconductors, and dielectrics. We show how jet structure, behavior, and vapor transport underlie advantages of JVD such as high rate deposition and flexibility in multicomponent synthesis.
Characterization and analysis of ZnO:Al deposited by reactive magnetron sputtering
Authors: Zafar S. , Ferekides C. S. , Morel D. L.
Published: July 2002

We have deposited ZnO:Al films with state-of-the-art electro-optical properties by reactive magnetron sputtering from a zinc target. Films with resistivities of 5×10−4 Ω cm, good optical properties over the visible and near infrared, and with good uniformity are routinely produced. Resistivities down to 1.7×10−4 Ω cm have been achieved but are accompanied by expected losses in optical properties. The fundamental mechanisms driving performance are largely determined by an interplay between microstructure and ionized impurity scattering. At the deposition level the parameters which control these mechanisms are substrate bombardment and substrate temperature. At substrate temperatures of 350 °C and sufficient source-to-substrate distances doping efficiencies approaching 100% can be achieved. At carrier concentrations of 4×1020 cm3 or higher there is a crossover from defect controlled transport to ionized impurity scattering dominated transport which constrains improvements in conductivity. This combined with free carrier effects on optical properties sets the limits for the electro-optical properties of these films. This understanding can be used to further develop the deployment of these films as transparent conductors.
Spectroscopic ellipsometry of thin films on transparent substrates: A formalism for data interpretation
Authors: Yang Y. H. , Abelson J. R.
Published: July 2002

By reviewing the operational principles of modern rotating analyzer ellipsometry, we propose general analytical formalism which permits the analysis of spectroscopic ellipsometry data for thin films on transparent substrates. The inclusion of incoherent reflection from the backsurface of an optically thick substrate changes the usual definitions of Δ and ψ. Experimental data on both glass and ZnO-coated glass are modeled to confirm the validity of this new formalism. We also simulated the ellipsometry spectra of amorphous silicon on glass to show the potential for in situ studies. The results show that the accuracy of ellipsometry data can be improved by including this incoherent backsurface reflection in the measurement, as opposed to roughening the back of the substrate.
Investigation of polycrystalline CdTe thin films deposited by physical vapor deposition, close-spaced sublimation, and sputtering
Authors: Moutinho H. R. , Hasoon F. S. , Abulfotuh F. , Kazmerski L. L.
Published: July 2002

CdTe thin films, deposited on different substrate structures by physical vapor deposition, sputtering, and close-spaced sublimation, have been treated with CdCl2 at several temperatures. The morphology of the films has been studied by atomic force microscopy, and the observations were correlated to results obtained from x-ray diffraction, cathodoluminescence, and minority-carrier lifetime measurements. The samples treated at 400 °C resulted in the best device-quality films, independent of deposition method and underlying substrate structure. For the first time, a nanograin structure was observed in CdTe sputtered samples.
Mass and energy selected ion beam for deposition and ion induced surface modifications
Authors: Küttel O. M. , Groening P. , Agostino R. G. , Schlapbach L.
Published: July 2002

A mass and energy selected ion beam source, differentially pumped for ultrahigh vacuum (UHV) applications, was constructed and successfully tested. Ions with a mass up to 2048 amu and with energies of 5–500 eV can be selected from a Penning discharge chamber by a quadrupole massfilter and an electrostatic lens system. The ion gun is operated in combination with a VG ESCALAB spectrometer for x-ray photoelectron spectroscopy and diffraction working at a base pressure in the 10−11 mbar range. Two applications of low energy ion bombardment are discussed in this article: etching of PMMA with 5 eV Ar+ ions, and deposition of a-C:H films on silicon. Ar+ ions at very low energies can react with a PMMA surface by a charge exchange reaction leading to a breakup of chemical bonds and to the preferential etching of oxygen. By depositing CHx ions (x=3,4) on a silicon surface under UHV conditions an oriented SiC layer is formed upon annealing at 800 °C. The ion beam was characterized with respect to mass and energy resolution and beam spreading for different ion energies.