bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of a Torsional Fluid Film Vibrator
Authors: Suciu C. V. , Iwatsubo T. , Pascovici M. D.
Published: July 2002

A novel hydrodynamic system, called torsional fluid film vibrator (TFFV) is proposed. This device is complementary to the Lanchester’s absorber and presents a classical response of a one-degree of freedom linear system with a periodical self-excitation. The fluid film thickness variation produces a variable viscous drag moment, which drives the elastically supported bush in a torsional oscillatory movement. The TFFV concept is connected with current research to improve the drilling technology of deep holes. The Navier-Stokes equations are solved on the particular geometry of this vibrator and the viscous drag moment is explicitly presented. The theoretical part is continued with the TFFV dynamic simulation and the analysis of the influence of the geometrical parameters on the amplitude of the viscous drag moment. Computed structural friction power and the amplitude of vibration agree reasonably well with the experimental measurements conducted on a TFFV test rig.
Combined Free and Forced Convection Film Condensation on a
Finite-Size Horizontal Wavy Plate
Authors: Wang Chi-Chang , Chen Cha'o-Kuang
Published: July 2002

Mixed-convection film condensation with downward flowing vapors onto a finite-size horizontal wavy plate is studied by a simple mathematical model and the spline alternating-direction implicit method. Effects of the wavy geometry, the interfacial vapor shear and the pressure gradient on the local condensate film thickness and the heat transfer characteristics have been studied independently. Results show that the pressure gradient tends to increase the heat transfer rate and to decrease the influence of the wavy amplitude. The appropriate wave number which can enhance the maximum condensation heat transfer rate is found in the neighborhood of lunder all circumstances.
Dynamic Characteristics and Design Consideration of a Tripad Slider in the Near-Contact Regime
Authors: Iida Kohei , Ono Kyosuke , Yamane Masami
Published: July 2002

We numerically investigated the tracking ability, the dynamic contact and friction forces of a 2-DOF model of a tripad slider over a random wavy disk surface with 1 nm rms value in the near-contact regime. The air bearing was modeled as a lumped spring and dashpot in order to consider a general design methodology of the flying slider in the near-contact regime. The nominal flying height was changed from the contact regime to the near-contact regime. We studied the effects of the front and rear air bearing stiffnesses, the nominal flying height and the friction coefficient on the tracking ability and contact force. As a result, we found that the spacing variation is caused not only by the slider dynamics but also by the micro-waviness of the disk surface and the distance of the contact pad (head-gap) position from the rear air bearing center. We also derived the closed form frequency response functions of the spacing variation to the disk surface waviness. The approximation agreed with the numerical simulation. The effect of the friction coefficient on the tracking ability can be neglected when the flying height is more than 1 nm.
Flow Visualizations and Transient Temperature Measurements in an
Axisymmetric Impinging Jet Rapid Thermal Chemical Vapor Deposition Reactor
Authors: Mathews A. G. , Peterson J. E.
Published: July 2002

Abstracts

Carrier gas flow in a rapid thermal chemical vapor deposition (RTCVD) reactor was studied using flow visualization and laser induced Rayleigh light scattering (RLS). The flow field consists of a downward axisymmetric jet of carrier gas impinging on a wafer which undergoes transient heating. Flow visualization results showed three stable flow regimes as the surface rose from ambient to high temperature: momentum dominated, buoyancy dominated, and a second momentum dominated regime at high temperature; each separated by unstable, chaotic flows. RLS temperature measurements provided transient gas temperature histories, documenting flow visualization results. Regions of momentum dominated, buoyancy dominated, and unstable flows were defined as a function of Grashof number, Reynolds number, pressure, and wafer temperature.
A Special Theory of Biphasic Mixtures and Experimental Results for Human Annulus Fibrosus Tested in Confined Compression
Authors: Klisch Stephen M. , Lotz Jeffrey C.
Published: July 2002

A finite deformation mixture theory is used to quantify the mechanical properties of the annulus fibrosus using experimental data obtained from a confined compression protocol. Certain constitutive assumptions are introduced to derive a special mixture of an elastic solid and an inviscid fluid, and the constraint of intrinsic incompressibility is introduced in a manner that is consistent with results obtained for the special theory. Thirty-two annulus fibrosus specimens oriented in axial n=16 and radial n=16 directions were obtained from the middle-lateral portion of intact intervertebral discs from human lumbar spines and tested in a stress-relaxation protocol. Material constants are determined by fitting the theory to experimental data representing the equilibrium stress versus stretch and the surface stress time history curves. No significant differences in material constants due to orientation existed, but significant differences existed due to the choice of theory used to fit the data. In comparison with earlier studies with healthy annular tissue, we report a lower aggregate modulus and a higher initial permeability constant. These differences are explained by the choice of reference configuration for the experimental studies. [S0148-0731(00)01002-5]
Editorial
Authors: Howell Jack
Published: July 2002

[S0022-1481(00)03101-7]
Flammability Measurements of Difluoromethane
Authors: Grosshandler W. L. , Donnelly M. K. , Womeldorf C.
Published: July 2002

Difluoromethane (CH2F2, or R-32) is a candidate to replace ozone-depleting chlorofluorocarbon refrigerants. Because CH2F2 is flammable, it is necessary to assess the hazard posed by a leak in a refrigeration machine. The currently accepted method for determining flammability, ASTM E 681 has difficulty discerning the flammability boundary for weak fuels such as CH2F2. This article describes an alternative approach to identify the limits of flammability, using a twin, premixed counterflow flame. By using the extinction of an already established flame, the point dividing flammable from nonflammable becomes unambiguous. The limiting extinction mixture changes with stretch rate, so it is convenient to report the flammability limit as the value extrapolated to a zero stretch condition. In the burner, contoured nozzles with outlet diameters of 12 mm are aligned counter to each other and spaced 12 mm apart. The lean flammability limit of CH2F2 in dry air at room temperature was previously reported by the authors to be a mole fraction of 0.14, using the twin counterflow flame method. In the current study, relative humidity was not found to affect the lean limit. Increasing the temperature of the premixed fuel and air to 100°C is shown to extend the flammability limit in the lean direction to 0.13. The rich limit of CH2F2 found using the counterflow method is around 0.27. The uncertainties of the measurements are presented and the results compared to data in the literature. [S0022-1481(00)02501-9]
Analysis of the Two-Flux Model for Predicting Water Spray Transmittance in Fire Protection Application
Authors: Dembele S. , Wen J. X. , Sacadura J. F.
Published: July 2002

An investigation is carried out to assess the two-flux model for evaluating the attenuation ability of a water spray curtain in fire protection. Transmittances calculated with this model are compared with the “exact” discrete ordinates solutions for a range of water curtains under practical conditions. The results show the unsuitability of the two-flux method under a collimated incidence boundary condition, even if some improvements could be expected with very small droplets. Whereas the diffuse incidence type provides relatively better results, it is more reliable for transmittance calculations. [S0022-1481(00)00101-8]
Evaluation of a Two-Dimensional Conductivity Function Based on Boundary Measurements
Authors: Tadi M.
Published: July 2002

This paper is concerned with an inverse problem for the conduction of heat in a two-dimensional domain. It seeks to recover the subsurface conductivity profile based on the measurements obtained at the boundary. The method considers a temporal interval for which time-dependent measurements are provided. It formulates an optimal estimation problem which seeks to minimize the error difference between the given data and the response from the system. It uses a combination of the zeroth-order and the first-order Tikhonov regularization to stabilize the inversion. The method leads to an iterative algorithm which, at every iteration, requires the solution to a two-point boundary value problem. A number of numerical results are presented which indicate that a close estimate of the thermal conductivity function can be obtained based on the boundary measurements only. [S0022-1481(00)00902-6]
Decoupling the Confounded Effect of Machine Error and Geometric Characteristics of Artifacts in Precision Measurement and Machine Calibration
Authors: Lee G. , Mou J. , Shen Y.
Published: July 2002

Inspection is commonly used to scrutinize the quality of manufactured products against established standards and specifications. However, the quality and reliability of many inspection processes are contaminated by various measurement errors. One of the prominent sources for measurement error is the imperfection of the measuring device and its interaction with geometric characteristics of a measured feature. To ensure the quality and reliability of any inspection process, measurement errors need to be addressed for all data acquisition activities. A method is also needed to identify and decouple the effect of confounded errors. If this can be done, then the collected data can be adjusted properly to allow a more meaningful analysis. In this paper, the issue of measurement error identification and reduction for machine calibration and dimension measurement using artifacts with spherical features is discussed. Analytical models are derived to first assess and then decouple the confounded effect of imperfect measuring device and its interaction with geometric characteristics of a measured feature. Finally, case studies are used to illustrate the use and effectiveness of the methodology. [S1087-1357(00)00402-0]
Effect of Datum Securing Method on Precision of Mechanical Alignment System
Authors: Lee Neville K. S. , Hon Keith K. C. , Cheung Venus P. Y. , Joneja Ajay
Published: July 2002

In this research, the achievable precision level using mechanical datums for manufacturing has been studied. Specifically, the effect of how a datum is secured in a mechanical alignment system was studied with the aid of a high-resolution multidimensional optical position monitoring system developed for the purpose. The study shows that the way datum is secured can be a major factor affecting the alignment precision of a mechanical alignment system. For a datum prepared by randomly inserting dowel pins into precision bored holes, a common practice in industry, the precision level was found to be worse than 10 μm. The results also show that the precision level can be readily improved by addressing this major cause of inaccuracy. Different methods depending on manufacturing requirements and constraints have been proposed. Some of these simple procedures lead to more than an order of magnitude improvement in alignment precision. [S1087-1357(00)02001-3]
Polytetrafluoroethylene by XPS
Authors: Ackeret Michael
Published: July 2002

X-ray photoelectron spectroscopy was used to analyze a 1 cm2, 0.13 mm thick coupon of polytetrafluoroethylene (PTFE). The material was examined as received from the manufacturer following a cleaning with isopropyl alcohol and trichlorotrifluoroethane. The PTFE coupon was examined with a Hewlett-Packard 5950B ESCA system. Measured atomic composition percentages closely matched the expected stoichiometry of the polymer.
GaAs(110) by XPS
Authors: Poirier D. M. , Weaver J. H.
Published: July 2002

X-ray photoelectron spectra of GaAs(110) were recorded for a single crystal cleaved in situ (Accession #00101). For comparison, spectra are included for a (110) surface cleaved ex situ and exposed to air for 1 h (Accession #00102). The electronic record includes, for each surface preparation, the valence band region, the Ga and As 3d regions, the Ga and As LMM regions, and the Ga 2p region.
Sodium Salts of Chlorine Oxyacid Anions, Cl(+3), Chlorite, XPS Comparison Spectra
Authors: Beard Bruce C.
Published: July 2002

High quality sodium chlorite has been analyzed as part of a series of chlorine oxyacid salts, chlorite to perchlorate. The spectra include survey and high resolution scans over the major photopeaks, the sodium Auger transitions and the valence band of the compound. Spectra for this compound were collected with the magnesium x-ray source. Several literature references are provided as additional sources of XPS data and description of the chemistry of chlorine oxyacid anions.
Sodium Salts of Chlorine Oxyacid Anions, Cl(+5), Chlorate, XPS Comparison Spectra
Authors: Beard Bruce C.
Published: July 2002

High quality sodium chlorate has been analyzed as part of a series of chlorine oxyacid salts, chlorite to perchlorate. The spectra include survey and high resolution scans over the major photopeaks, the sodium Auger transitions and the valence band of the compound. Spectra for this compound were collected with the magnesium x-ray source. Several literature references are provided as additional sources of XPS data and description of the chemistry of chlorine oxyacid anions.
Fresh Cleaved Single Crystal NaCl, XPS spectra, Mg Source
Authors: Beard Bruce C.
Published: July 2002

High quality single crystal NaCl has been analyzed as one in the series of Na salts (chloride to perchlorate) with the Cl anions. The spectra include survey and high resolution scans over the major photopeaks, the Na Auger transitions and the valence band of the compound. Spectra were collected with an Mg source. A companion submission shows spectra collected with a Al source.
Ar Sputtered Si by XPS
Authors: Nakajima Kazuhiro , McGinnis Sean P. , Kelly Michael A.
Published: July 2002

X-ray photoemission spectra from Si which has been physically etched by Ar ion sputtering are presented. The data include measurements of the valence band region, Si 2p region, Si 2s region, C 1s region, and plasmon structure. These data are useful for comparison to pristine and oxidized silicon.
Alternative NH4F/HCl solution for ultraclean Si(001) surface
Authors: Bok T. H. , Ye J. H. , Li Sam F. Y.
Published: July 2002

Ultraclean silicon surface after wet cleaning is extremely crucial in critical steps such as pregate clean in the next generation of electronic devices. Metallic contamination has an adverse effect on device characteristics and must be controlled as low as possible, typically less than 1010 atoms/cm2. A new solution was developed for wet chemical cleaning of silicon, which was investigated by using scanning tunneling microscope, inductively coupled plasma mass spectrometer and total reflection x-ray fluorescence spectrometry. It was found that NH4F with HCl diluted with deionized water resulted in the least surface roughness (0.16±0.02 nm) on silicon and metallic impurities adhered to the silicon surface compared to diluted HF. With the new solution, Cu impurity, the major metallic contamination, was suppressed to less than 2×109 atoms/cm2. Other metallic impurities such as Ca, Fe, Zn, and Ti on the silicon surface were at level of 1010 atoms/cm2, which were lower than that treated by diluted HF. The results suggest that the complex reactions between chloride and metal ions result in less metal deposition on silicon surfaces.
Potassium reaction on sulfur-passivated GaAs(100)
Authors: Seo J. M.
Published: July 2002

It has been confirmed by high-resolution x-ray photoelectron spectroscopy that the Fermi level of K-contacted sulfur-passivated GaAs(100) is not located at the Fermi level of the ideal Schottky contact and is pinned near the midgap, even though the initial S passivation removes the high density gap states. With K deposition the Fermi level moves to 0.5 eV above the valence band maximum for both n- and p-type surfaces. The interfacial chemical reaction shows the top As element preferentially reacts with deposited K, and the interface still has dominant Ga–S bondings. These results imply that although the reactive alkali metal such as K does not break Ga–S bondings, it induces the metallic state which pins the Fermi level at 0.5 eV above the valence band maximum.
Studies on the optimum condition for the formation of a neutral loop discharge plasma
Authors: Sung Y. M. , Uchino K. , Muraoka K. , Sakoda T.
Published: July 2002

In order to obtain guidelines for the design and operation of a new plasma source by a magnetic neutral loop discharge, electron behavior was studied experimentally and numerically. Experimentally, the magnetic field gradient was changed over a wide range, and it was found that there existed an optimum value for efficient plasma production. Analyses of the electron behavior were performed using a model that included effects of a three-dimensional electromagnetic field with spatial decay of the rf electric field, and the limitation of the spatial extent of the electron motion (the existence of walls and the electron loss at wall surfaces). These factors were found to explain the existence of the optimum magnetic field gradient.
Epitaxial growth of La–Ca–Mn–O thin film on out-of-plane twinned LaAlO3
Authors: Song J.-H. , Kim K. K. , Oh Y. J. , Jung H.-J. , Choi W. K. , Song J. H. , Choi D.-K.
Published: July 2002

La–Ca–Mn–O (LCMO) thin film with 145 nm thickness was epitaxially grown on a LaAlO3(100) substrate using radio frequency (rf) magnetron sputtering. The crystalline structure of the LCMO thin film on LaAlO3(LAO) was characterized using backscattering (BS)/channeling and four-circle x-ray diffractometer. LCMO thin film grown at 600 °C and rf power level of 100 W shows the full width at half maximum of 0.311° in the x-ray diffraction (XRD) θ-rocking curve for the LCMO (200) peak. Such a large value, however, is inconsistent with the very small BS/channeling minimum channeling yield (χmin) 4.98%. Thus, the origin of this discrepancy between the results is examined. In channeling angular scans of 〈001〉 and 〈011〉 axial direction in the (100) plane for the LCMO film on the LAO substrate, only the 〈011〉 direction showed an angular scan difference by 1.12°. In addition, it can be observed that the substrate intrinsically has the out-of-plane twin structure from the high-resolution XRD θ rocking on the LaAlO3(200) peak. From earlier results, it can be concluded the film with only the strained layer was epitaxially grown on the out-of-plane twinned substrate.
Spectra mapping of scanning tunneling microscope-induced light from electrochemically deposited Ag films on Au
Authors: Nishitani R. , Kasuya A. , Szuba S.
Published: July 2002

We have carried out spectra mapping measurements of scanning tunneling microscope (STM)-induced photon emission from electrochemically deposited Ag films on Au. The luminescence spectra for Ag and Au films are recorded at the same time as the STM topography image in air. The spectrally resolved photon intensity map is obtained from the observed 4096 spectra, which shows a correlation with the topography. The luminescence spectra observed for Ag films exhibit a broader band of spectra with a spectral shift toward a shorter wavelength compared with Au films. The spectral modes are compared with the topography of the films.
Damage in diamond produced by analysis beam
Authors: Ma Z. Q. , Liu B. X. , Naramoto H.
Published: July 2002

The lattice damage of a diamond crystal, caused by the analysis beam of helium ions with 2.0 MeV, 3 nA at room temperature, was characterized by nondestructive optical absorption topographic imaging that used position-sensitive scanning spectroscopy in the transmission mode. The result showed that the atomic structure and electronic states in diamond have been significantly changed by the ion beam, even at very low dose or dose rate. The measurement has been applied to the artificial diamond crystal (type Ib) to evaluate how the damage induced by Rutherford backscattering/channeling, and the comparison to ion implantation (H2+) is given. We found that a high column image, which reflects the defective states in irradiated synthetic diamond, provides a qualitative estimation of damage.
Determination of coupled acid catalysis-diffusion processes in a positive-tone chemically amplified photoresist
Authors: Houle F. A. , Hinsberg W. D. , Morrison M. , Sanchez M. I. , Wallraff G. , Larson C. , Hoffnagle J.
Published: July 2002

Acid diffusion during postexposure baking is viewed to be a limiting factor in the extension of lithography using chemically amplified resists to formation of nanoscale features. Quantification of thermally activated reaction-diffusion kinetics in these materials is therefore an important step in understanding the extendability of this class of resist systems. Previous investigations have addressed this issue, however there is poor agreement among them, and too few data exist in the literature to allow the systematics of the effect of polymer, photoacid generator, added base or other resist components on the diffusion process to be understood. We describe in this article a combined experimental and modeling protocol that is designed to elucidate the chemistry and physics of the reaction-diffusion process. Because it is physically based, not phenomenological, it provides a means of developing a set of predictive, mutually comparable data that will allow new insights to be developed into the nanoscale behavior of chemically amplified resist materials. We apply the protocol to a p-t-butyloxycarbonyloxystyrene/bis(t-butylphenyl)iodonium perfluorobutanesulfonate positive-tone photoresist system. The resulting kinetics measurements show that diffusion is environment sensistive and describable with two limiting diffusion coefficients. The Arrhenius parameters for the coefficients in p-t-butyloxycarbonyloxystyrene are D0=1.9×108 cm2/s and Ea=36.5 kcal/mol; those for diffusion in the deprotected polymer product p-hydroxystyrene are D0=9×10−3 cm2/s and Ea=22.1 kcal/mol. The coefficients are much smaller than previously reported, resulting in a very slow diffusion rate. The model indicates that the considerable image spreading observed during the postexposure bake process is attributable primarily to the efficiency of the catalytic chemistry. Our results suggest that numerical models currently used for prediction of imaging in chemically amplified resists may require refinement in order to be useful for feature sizes below 100 nm and for new classes of resist systems.
A study of the bonding mechanism of sprayed coatings
Authors: Kitahara Shigeru , Hasui Atsushi
Published: July 2002

The adhesive mechanism of plasma jet-sprayed nickel, chromium, molybdenum, tantalum, and tungsten coatings on aluminum and mild steel substrates was investigated. The compositions of the boundary layers between the coatings and the substrates were studied using x-ray diffraction. Experiments on the bonding behavior between substrates and nickel drops heated by the levitation melting process were also performed. The results of the experiments show that: (i) the substrate surface is melted by the sprayed particles, and a boundary layer which consists of an intermetallic compound consisting of the elements of the coating and substrate materials is formed between the coating and the substrate; (ii) this layer is necessary to improve the adhesion between the sprayed coating and the substrate; (iii) the adhesive mechanism between the sprayed coating and the substrate surface and the composition of the boundary layer were confirmed by a liquid nickel-drop experiment.
A study on the maximum tolerable pressure in a residual gas analyzer
Authors: Werner H. W. , Linssen A. J.
Published: July 2002

The tolerable pressure in a magnetic sector-type mass spectrometer with respect to an undisturbed linear relation between the ion current measured at the collector and the pressure in the mass spectrometer has been studied. The different factors contributing to a disturbance of this relation and their corresponding different values for the tolerable pressure will be discussed. It is shown that by an increase of the pressure above 10−4 Torr(≈10−2Pa) the positive space charge and scattering at the residual gas are predominant factors causing a deterioration of the performance of the instrument. The mass dependence of these two factors is discussed by comparing theoretical and experimental results.
The Reactions of Titanium and Silicon with Al2O3-CaO-CaF2 Slags in the ESR Process
Authors: Pateisky G. , Biele H. , Fleischer H. J.
Published: July 2002

The reactions of titanium and silicon with slags of the system alumina-calcium oxide-fluorspar were calculated. The calculations were confirmed by melts in a laboratory induction furnace and also through statistical calculations of 320 heats of 500 mm □ (3,6 ton) ingots for the Ti–Al2O3 reaction and of 100 ESR heats of the same ingot size for the Si–Al2O3 reaction. By statistical evaluation of all heats the dependence of the aluminum and titanium or silicon contents for different TiO2 or SiO2 contents of the slags were determined. By application of these data the losses of Ti or Si by a reaction with alumina can be prevented.
Wide dynamic range silicon diaphragm vacuum sensor by electrostatic servo system
Authors: Miyashita Haruzo , Esashi Masayoshi
Published: July 2002

A wide dynamic range silicon diaphragm vacuum sensor by an electrostatic servo system and an electrical circuit for servo control have been made. In nonservo mode, i.e., when the sensor was used as a capacitive vacuum sensor, a linear characteristic between pressure and output voltage was obtained in the pressure range from 0.1 to 100 Pa. On the other hand, the square root of the servo voltage was proportional to the pressure in a wide pressure range from 0.1 to 530 Pa in servo mode. The servo mechanism is effective for widening the dynamic range of vacuum sensors.
Theoretical and experimental characterization of a low-pressure rf plasma and its optimization in electron-gas secondary-neutral mass spectrometry
Authors: Bieck W. , Merz E. , Gnaser H. , Oechsner H.
Published: July 2002

The charge-density distribution and the respective plasma potential distribution in an electrodeless low-pressure rf plasma as it is employed in electron-gas secondary-neutral mass spectrometry (SNMS) were determined theoretically by a comparatively simple plasma model. A second-order finite element program combines a Maxwell–Boltzmann like electron density distribution with a collective drift motion of plasma ions directed from the center of the discharge to the wall of the plasma chamber and calculates a self-consistent solution of the space-charge problem by iteratively solving the appropriate Poisson equation. A comparison with the experimentally determined spatial distributions of the electron density and the plasma potential for two different geometries of the plasma chamber shows good agreement with respect to the theoretical calculations. A plasma chamber optimized via this plasma modeling was incorporated into a SNMS instrument. The new chamber’s performance was studied with respect to previously used geometries. A distinct enhancement of the intensities of postionized sputtered species was observed and ascribed to a plasma-optical focusing effect. Full exploitation of this beneficial feature appears to be partially limited by a concurrent increase of space-charge accumulation in the vicinity close to the plasma chamber’s exit aperture.
Microstructure of Fe–N thin films prepared using an atomic nitrogen beam
Authors: Telling N. D. , Jones G. A. , Faunce C. A. , Grundy P. J. , Blythe H. J. , Joyce D. E.
Published: July 2002

The formation of Fe–N thin films by exposure to an atomic (free radical) nitrogen beam is reported. This new method of preparing Fe–N films uses fluxes of highly reactive, thermal energy N atoms that do not disturb the film microstructure. It is shown that by careful control of the exposure conditions, a range of predominantly single phase films can be obtained. At low nitrogen concentrations an amorphous-like phase is observed, whereas crystalline phases of ε-Fe2-3N and ζ-Fe2N are formed at higher concentrations. Dramatic differences in the microstructure and crystallographic texture of these films reveal the inherent microstructure of the different phases rather than the influence of the growth technique.
“Standardization” of field emission measurements
Authors: Zhirnov V. V. , Lizzul-Rinne C. , Wojak G. J. , Sanwald R. C. , Hren J. J.
Published: July 2002

Interest in field emission and field emission devices has been renewed in the last 5 yr. This increase has been due to work on several new materials systems, which have shown promising field emission (FE) behavior. In turn, this interest gives impetus to the search for new FE sources. In order to move the technology ahead at a faster pace, there is a need for common ground rules and a “standardization” of the data reported so that it can be compared directly in a meaningful way and thereby accelerate the development process. In this article key factors affecting the FE data will be discussed and several parameters are suggested to initiate the process of developing a set of “standardized” FE parameters. A correct, or at least consistent, determination of characteristics such as work function, emission area, and field enhancement form the basis for developing a framework to make meaningful comparisons between different sets of data.
Damage in III/V semiconductors caused by hard- and soft-etching plasmas
Authors: Franz Gerhard
Published: July 2002

Damage in III/V semiconductors caused by processing in high- and low-density plasmas is investigated employing material-specific analytical methods. To distinguish the various regimes of damage, four different ambients out of the palette of plasma constituents were chosen: as borderline cases, argon which is associated with hard etching causing crystal lattice disordering until complete amorphization, and hydrogen which is the prototype of soft etching causing bond breaking between the lattice constituents without changing the crystal site, and the two model ambients Ar/Cl2 and Ar/CH4/Cl2/H2 which are widely used to etch Ga-containing compound semiconductors. Several probes and methods are employed which are selectively sensitive to the different kinds of damage: damage of the crystal lattice with photoluminescence, scanning electron microscopy and scanning transmission electron microscopy, and the concentration gradient of a chemically reactive species (hydrogen) with secondary ion mass spectrometry. Its reaction with lattice atoms (acceptor passivation), is recorded by capacitance/voltage and Hall measurements. For irreversible damage (knock out of atomic lattice sites), there can be detected only one damage zone reaching not deeper than 30 nm. The depth is inversely proportional to the lattice energy and proportional to the kinetic energy of the projectiles. In contrast to this rather shallow damage, the penetration depth of hydrogen amounts up to several microns. Since the subsequent passivation of acceptor atoms is a chemical reaction, it can be reverted at elevated temperatures. It has turned out, with all methods applied, that the gentlest ambient to etch Ga-containing III/V semiconductors is Ar/Cl2. This is not restricted to the smoothness of the surfaces but refers to all quantitative measurements which are applied in this study.
Comparative ion yields by secondary ion mass spectrometry from microelectronic films
Authors: Parks Christopher C.
Published: July 2002

Secondary ion mass spectrometry (SIMS) is reported from multiple-element multiple-matrix ion implants. The implants include a thirteen element metal set and a six element gas set implanted into films of interest for microelectronics (silicon, silicides, wiring layers, liner metals, inorganic dielectrics, and polymer dielectrics.) Using these standards, this study performs a broad comparison of ion yields using a metric defined as the normalized useful yield. We find that the yield of K+ with O2+ primaries is constant for almost all matrices, in keeping with a concept of ion yield saturation. The yield of Cl− with Cs+ primaries approaches a yield saturation limit for titanium but the ion yield falls for materials with higher sputter yields, becoming 3.5× lower from copper. The variations in negative ion yields from matrix to matrix are much larger, with anomalies more pronounced, for weaker-yielding ions, becoming 50× for C− from Ti to Cu. In this article we document sets of ion implants, show some of the SIMS profiles, and note trends in ion yields and implications for SIMS analysis.
Electrical properties of in situ As doped Hg1−xCdxTe epilayers grown by molecular beam epitaxy
Authors: Selamet Y. , Grein C. H. , Lee T. S. , Sivananthan S.
Published: July 2002

The electrical properties of extrinsic in situ doped mercury cadmium telluride (Hg1−xCdxTe) epilayers grown by molecular beam epitaxy on (211)B CdTe/Si and CdZnTe substrates are studied. The doping is performed with an elemental arsenic source. HgCdTe epilayers with a CdTe mole fraction between 0.23 and 0.36 are grown at substrate temperatures of 175–185 °C. The temperature dependent Hall effect characteristics of the grown samples are measured by the van der Pauw technique. A magnetic field of up to 0.8 T is used in these measurements. An analysis of the Hall coefficient in the temperature range of 40–300 K with a fitting based on a two-band nonparabolic Kane model, a fully ionized compensating donor concentration, and two independent discrete acceptor levels is reported. In addition, the fitting results of a three-band modeling of Hall effect results are compared to published data on p-type Hg1−xCdxTe. Both as-grown and annealed samples are used in this study. All of the as-grown samples showed n-type characteristics whereas annealed samples showed p-type characteristics. The minority carrier lifetimes of arsenic doped epilayers measured by a photoconductive decay method are presented. In this work, an AlGaAs laser of wavelength 850 nm with a pulse length of 10–90 ns is used. The electron lifetimes obtained from this study are compared to published minority electron lifetimes in p-type HgCdTe. Theoretical electron lifetimes of p-type Hg1−xCdxTe material are reported and a comparison to published electron lifetimes is also given.
Study of high- and low-work-function surfaces for hyperthermal surface ionization using an absolute Kelvin probe
Authors: Baikie I. D. , Peterman U. , Lägel B. , Dirscherl K.
Published: July 2002

We have performed a study of high- (>6 eV) and low- (<3 eV) work-function surfaces in order to identify suitable target materials as an ion source for a new type of mass spectrometer technique based on hyperthermal surface ionization (HSI). In this application a molecular beam of neutral gas molecules is ionized by supersonic collision on a target surface. High-work-function surfaces produce positive ions (pHSI), and low-work-function surfaces negative ions (nHSI). Analytical merits of HSI include very high sensitivity, atmospheric pressure inlet, and informative mass spectra. As this technique does not use electron-impact filaments, the amount of cracking products is substantially reduced. The ultra-high-vacuum (UHV) scanning Kelvin probe is a technique producing relative work-function topographies between a scanning reference tip and the sample in a truly noninvasive fashion with high accuracy (1–2 meV). We demonstrate a novel extension of this technique, using photoelectric determination, which produces absolute work-function data even if the tip work function is not known. Using this hybrid probe, together with scanning electron microscopy and Auger electron spectroscopy, we have followed (a) work-function topographies of clean surfaces in UHV, (b) changes in work function with oxidation that are related to surface cleaning processes, (c) the temperature-dependent oxidation kinetics of polycrystalline metal surfaces (Re, Pt, Mo, W, and Pd) for pHSI, and (d) the stability of Ca, Gd, and LaB6 under residual gases for nHSI. We will report the optimum parameters for target stability and performance under both pHSI and nHSI operating conditions. We will also illustrate informative mass spectra produced by time-of-flight HSI.
Enhanced passivity of austenitic AISI 304 stainless steel by low-temperature ion nitriding
Authors: Rudenja S. , Pan J. , Wallinder I. Odnevall , Leygraf C. , Kulu P. , Mikli V.
Published: July 2002

Low-temperature ion nitriding introduces interstitial nitrogen into the austenitic stainless steel matrix. An enhanced passivity of the nitrided stainless steel was detected by anodic potentiodynamic polarization in a 0.1 M H2SO4+0.05 M HCl electrolyte. Capacitance measurements by electrochemical impedance spectroscopy revealed a 3–4 nm thick oxide film on the surface of nitrided specimens that is two to three times thicker than on blank specimens. X-ray photoelectron spectroscopy analyses and Auger depth profiles indicate increased chromium uptake into the oxide film on the nitrided surface, supposedly through the kinetically stable oxide–metal interface enriched with nitrogen and nickel. Several possible mechanisms that influence passivation of the nitrided stainless steel may operate simultaneously. Among these mechanisms, austenite strengthening by interstitial nitrogen near the oxide/alloy interface associated with structural defects like dislocation branches and vacancies are most likely the explanation for the enhanced passivity of the nitrided stainless steel.
Optical anisotropy of organic layers on GaAs(001)
Authors: Paraian A. M. , Rossow U. , Park S. , Salvan G. , Friedrich M. , Kampen T. U. , Zahn D. R. T.
Published: July 2002

The application of the linear-optical, polarization sensitive methods, in situ reflectance anisotropy spectroscopy (RAS), and ex situ spectroscopic ellipsometry, for the characterization of organic layers is discussed and the results of the investigation of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) layers on sulfur passivated GaAs(001) surfaces are presented. The organic layers were grown via organic molecular beam deposition at room temperature. The RA spectrum of the sulfur terminated GaAs surface shows a derivative like feature at E1 gap and a feature in the higher energy range related to E2 of bulk GaAs. Upon the PTCDA deposition, additional features appear in the spectra which can be attributed to PTCDA while the GaAs feature near E1 remains unchanged indicating that the surface reconstruction stays intact. The imaginary part of the pseudo-dielectric function is found to be angular dependent. This dependence also changes as a function of azimuthal angle. While the first can be well described using existing models for optical uniaxial layers, the latter is likely to be related to in-plane optical anisotropy.
Development of 157 nm positive resists
Authors: Ito H. , Wallraff G. M. , Fender N. , Brock P. J. , Hinsberg W. D. , Mahorowala A. , Larson C. E. , Truong H. D. , Breyta G. , Allen R. D.
Published: July 2002

For adequate transparency we have selected hexafluoroisopropanol as an acid group and an α-trifluoromethylacrylic moiety as a repeat unit of our 157 nm resist polymers. The hexafluoroalcohol group is bound to norbornene or styrene. Four platforms are currently available to us: (1) all-acrylic, (2) all-alicyclic, (3) acrylic-alicyclic, and (4) acrylic-aromatic systems. While the all-alicyclic (all-norbornene) polymers are synthesized by transition-metal-initiated addition polymerization, all other polymers involving α-trifluoromethylacrylic monomers are prepared by conventional radical copolymerization. Characterization of the polymers and preliminary lithographic evaluation are reported.
Organic polymeric coatings deposited by plasma enhanced chemical vapor deposition
Authors: Sabnis Ram W. , Cazeca Mario , DiMenna William L. , Spencer Mary J. , Guerrero Douglas J. , Sheu Min-Shyan
Published: July 2002

A process of depositing thin organic polymeric coatings on electronic substrates by plasma enhanced chemical vapor deposition (PECVD) has been developed. We have designed halogenated compounds with PECVD reactive functionality attached to optically active moieties. Compounds have been screened selectively to lower the dielectric constant and enhance plasma polymerization efficiency. The chemical, optical, and mechanical properties of the deposited films such as film uniformity, film defectivity, film solubility, resist compatibility, conformality, adhesion to semiconductor substrates, refractive index, optical density, and photolithographic behavior have been studied. Plasma polymerized materials exhibit high sensitivity, excellent resolution, and good process latitude. PECVD provides a completely dry deposition process for wafer coating. The coatings possess high optical density at 193 nm.
Study on beam size correction free from Coulomb interaction
Authors: Takenaka H. , Sasago M.
Published: July 2002

The effect of Coulomb interaction in a variable shaped e-beam (EB) lithography system was studied. The effect of Coulomb interaction was estimated by a simulation. The simulation results predicted that beam blur due to Coulomb interaction in a variable shaped EB lithography system operated at the beam current density as high as 10 A/cm2 was not negligible for measurement and correction of beam size based on beam profile measurement, which deteriorates beam size accuracy by several hundredth micron. A new beam size correction method free from the effect of Coulomb interaction, which was based on beam current measurement, was implemented. The beam size accuracy of the new correction method was compared to that of conventional one, experimentally. While beam size errors exceeding 35 nm were found with the conventional correction method based on beam profile measurement, beam size errors were less than 10 nm with the new correction method based on beam current measurement. A beam size correction method based on beam current measurement is indispensable for a variable shaped EB lithography system operated at high current density in order to avoid the effect of Coulomb interactions and to attain high CD accuracy.
Lower sheet/contact resistance in shallower junction obtained by F+B mixed implant
Authors: Lee Jung-Ho , Lee Jeong-Youb , Yeo In Seok , Lee Seok-Kiu
Published: July 2002

Further reduction of sheet/contact resistance is observed and shallower junction is obtained using F+B implant instead of conventional B, BF2, or BF2+B implant. A deeper fluorine implant to increase the distance between F and B causes a higher retained boron dose while making the junction depth shallower upon annealing. Junction depth reduction is achieved by making the junction boundary abrupt near the junction depth, and higher retained boron dose leads to a reduction of sheet and contact resistance. Even if our experimental scheme practically focuses on the deep contact junction, the abrupt junction profile with high activation efficiency obtained by shifting the F implant deeper than B implant is also attractive for the ultrashallow source/drain extension technology for sub-0.1 μm p-type metal–oxide–semiconductor devices.
Effects of initial layers on surface roughness and crystallinity of microcrystalline silicon thin films formed by remote electron cyclotron resonance silane plasma
Authors: Murata Kazuya , Kikukawa Daisuke , Hori Masaru , Goto Toshio , Ito Masafumi
Published: July 2002

We have observed μc-Si:H films grown in the glass substrate in electron cyclotron resonance plasma-enhanced chemical vapor deposition employing two-step growth (TSG) method, where the seed layer was formed without charged species firstly, and subsequently, the film with charged species. The μc-Si:H films with smooth surface and high crystallinity were synthesized with a relatively high deposition rate at a low substrate temperature by TSG. By Fourier transform infrared attenuated-total reflection, it was found that the surface roughness and crystallinity of seed layer were related to the ratio of SiH bonds over SiH2 ones in the film. Consequently, the control of chemical bonds at the initial layer is of importance and TSG method is effective for the formation of μc-Si:H film with high quality.
Investigation of the silicon ion density during molecular beam epitaxy growth
Authors: Eifler G. , Kasper E. , Ashurov Kh. , Morozov S.
Published: July 2002

Ions impinging on a surface during molecular beam epitaxy influence the growth and the properties of the growing layer, for example, suppression of dopant segregation and the generation of crystal defects. The silicon electron gun in the molecular beam epitaxy (MBE) equipment is used as a source for silicon ions. To use the effect of ion bombardment the mechanism of generation and distribution of ions was investigated. A monitoring system was developed and attached at the substrate position in the MBE growth chamber to measure the ion and electron densities towards the substrate. A negative voltage was applied to the substrate to modify the ion energy and density. Furthermore the current caused by charge carriers impinging on the substrate was measured and compared with the results of the monitoring system. The electron and ion densities were measured by varying the emission current of the e-gun achieving silicon growth rates between 0.07 and 0.45 nm/s and by changing the voltage applied to the substrate between 0 to −1000 V. The dependencies of ion and electron densities were shown and discussed within the framework of a simple model. The charged carrier densities measured with the monitoring system enable to separate the ion part of the substrate current and show its correlation to the generation rate. Comparing the ion density on the whole substrate and in the center gives a hint to the ion beam focusing effect. The maximum ion and electron current densities obtained were 0.40 and 0.61 μA/cm2, respectively.
Performance Study of the Orbitron Ionization Gauge
Authors: Meyer E. A. , Herb R. G.
Published: July 2002

Recent work has provided better understanding of orbitron gauge performance and has led to substantial improvements. Coupling between the filament and the central field is a major factor controlling linearity, sensitivity, and oscillations. Positive ion emission from the filament, excess energy electrons reaching the ion collector and x-ray photocurrent are factors which can cause errors at low pressure. The present design is very simple with little structure inside the gauge to perturb pressure measurements. Gauge sensitivity has been increased by a factor of four, so only a 1-μA electron current is now required to produce the same ion current obtained from an 8-mA emission in the Bayard-Alpert gauge. Total power input to the gauge is less than 100 mW. The ion current is approximately linear with pressure from 10−11−10−5 Torr. The linear region can be extended to 10−2 Torr by operation in a non-orbiting mode.