bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron-Beam Float Zone and Vacuum Purification of Vanadium
Authors: Reed R. E.
Published: July 2002

Electron-beam float zone melting vanadium three passes at 3.9 in./h in 4×10−10 Torr vacuum resulted in resistance ratios of about 700 and a total impurity content of 50 wt ppm. The zoning reduced both carbon and oxygen content. However, while carbon removal was always accompanied by a lowering of the oxygen content, the reverse was not true. The removal of oxygen was probably accomplished by the formation and volatilization of VO. The mechanism for carbon removal was not clearly resolved. Nitrogen was not appreciably affected by electron-beam float zone melting. All metallic impurities, with the exception of Ta and W and possibly Si, were effectively volatilized. No evidence was found for zone refining action on any impurity. Vacuum outgassing further reduced the carbon and oxygen level. However, the oxygen removal was far more effective than the carbon. The nitrogen content increased, particularly on the specimens that lost about 40% in weight due to vanadium evaporation. However, the effect of vacuum outgassing was less on the highest purity as-zoned specimens. The same purification mechanisms apparently operated.
Quench Atomization of Iron-Base Alloys into Metal Powders
Authors: Rao Pradip , Grandzol Richard , Schulz Norbert , Tallmadge John
Published: July 2002

Quench atomization is discussed as a powder formation step used in the production of structural shapes by powder metallurgy. Emphasis is placed on the continuing study of atomization of liquid metals by the two-fluid nozzle method. The influence of atomization control variables on powder properties is considered, where the important characteristics include particle size, chemistry, grain size, and particle shape. Results from a 3–20 kg pilot unit are reported for the case of nitrogen atomization with an annular nozzle. Size, shape, and other powder properties are compared for the case of low and high carbon iron alloys. Some of the interrelationships between atomization and concurrent parts of the powder metallurgy study include fundamental mechanisms and process optimization as well as powder production and experimental studies.
Computer Simulation in Metals Research
Authors: Oldfield W.
Published: July 2002

The role of computers in applied research is discussed. Computer simulation is considered as a new set of mathematical techniques which augments and goes beyond the older analytic techniques. The major challenge of simulation methods is scientific rather than computational in the selection of models to represent a physical process. Models are discussed in the context of the problems of applied science. The simulation approach differs from conventional methods in that several models are combined to represent the one physical process. The role of the computer is to fit the models together in an interactive ensemble. Simulation techniques are exemplified first by a simulation of the bending and fracture of a Charpy impact specimen. The simple simulation is shown to be a powerful technique for automatically analyzing the data output from an automated test system. Two applications of simulation techniques to solidification processes are next described. The first deals with dendrite growth. A computer simulation shows that models for heat (or solute) flow coupled with a model for the solid-liquid interface are adequate to account for the branching and growth velocity of dendrites. The second deals with a solidifying casting aud illustrates the way additional models can be added to allow the description given by the simulation to resolve finer details of behavior. The wide scope of simulation techniques is illustrated by reference to the simulation of transmission electron micrographs. In conclusion, the sequential approach to simulation is recommended. In this approach, the simplest possible simulation is developed first. Then, additional models are added to refine the original treatment and improve its resolution.
Thermospheric Temperature Measurement Technique
Authors: Hueser J. E. , Fowler P.
Published: July 2002

A method for measurement of temperature in the earth’s lower thermosphere from a high-velocity probe is described. All undisturbed atmospheric sample is admitted to the instrument by means of a free molecular flow inlet system of skimmers which avoids surface collisions of the molecules prior to detection. Measurement of the time-of-flight (TOF) distribution of an initially well-localized group of nitrogen metastable molecular states produced in an open, crossed electron-molecular beam source, yields information on the atmospheric temperature. It is shown that for high vehicle velocities, the time-of-flight distribution of the metastable flux is a sensitive indicator of atmospheric temperature. The temperature measurement precision should be greater than 94% at the 99% confidence level over the range of altitudes from 120–170 km. These precision and altitude range estimates are based on the statistical consideration of the counting rates achieved with a multichannel analyzer using realistic values for system parameters.
On Electron Projection Systems
Authors: Koops H.
Published: July 2002

Demagnifying EPS have the capacity to generate as much as 5000 line pairs per diameter at a resolution as small as 0.1 μ. The diameter of the recorded image and the maximum number of line pairs per diameter decrease with increasing values of the chromatic field aberrations of the lens system, and with increasing relative energy width of the electron beam. The optimum aperture yielding maximum probe current at a given resolution and image field diameter depends mainly on the value of the coefficients of image curvature and isotropic and anisotropic astigmatism of the lens system.
Thick ion-vapor-deposited aluminum coatings for irregularly shaped aircraft and spacecraft parts
Authors: Steube K. E. , McCrary L. E.
Published: July 2002

Ion vapor deposition (IVD) is the same as the familiar physical vapor deposition (PVD) with one major difference—the substrate is held at a high negative potential with respect to the vapor source. This potential when applied at the proper system pressure improves adhesion and uniformity of the plating. Because the IVD process is not confined to line-of-sight deposition, parts with very complex shapes can be plated with a reasonably uniform coating. The deposit readily extends into the recesses and holes of the part due to the excellent throwing power of the process. Although IVD has been found superior to PVD, industry has not used IVD extensively in production applications. Recently McDonnell Aircraft Company has concentrated on applying IVD techniques to meet protective coating requirements of aircraft and spacecraft components. This technique has been used for applying coatings for corrosion prevention, aluminum coatings to replace cadmium coatings in contact with titanium to eliminate galvanic corrosion, and coatings for braze wettability. It is the purpose of this paper to present successful applications of the IVD process in coating production parts.
In situ characterization of residues formed on a plasma-etching chamber
Authors: Kawada Hiroki , Yamane Miyuki , Kitsunai Hiroyuki , Suzuki Shinichi
Published: July 2002

The chemical reaction of residues formed on a quartz surface in an electron cyclotron resonance plasma during the etching of Al and resist film by Cl2 and BCl3 plasma was characterized in situ by infrared reflection absorption (IRA) spectroscopy and quadrupole mass spectrometry (QMS). The plasma was generated in a chamber with a structure similar to a conventional production machine. Incident ions and molecules impacting onto a quartz surface at the chamber wall were analyzed by QMS. Then the residue formed on a quartz film on a sample mounted on the chamber wall was analyzed by IRA spectroscopy. The residue was identified as B2O3 which is formed by incident boron chloride ions that diffuse down through the B2O3 residue to the quartz surface and, there, thermally react with OH in the quartz. The residue film produced on the quartz surface could be identified by etching a 1-μm-thick Al film ten times at the etching rate of 12 nm/s. This combination of IRA and QMS is a promising technique for refining on-line etching by residue control.
Atomic force microscopy observation of layer-by-layer growth of ultrathin silicon dioxide by ozone gas at room temperature
Authors: Maeda T. , Kurokawa A. , Sakamoto K. , Ando A. , Itoh H. , Ichimura S.
Published: July 2002

Atomic structures on active oxidized silicon films by an ozone gas at room temperature are investigated by an atomic force microscopy. A step-terrace structure similar to that on a clean Si (001) prepared by a silicon homoepitaxy is preserved on the ozone oxidized surface. These atomically regulated structures are also discernible on the SiO2/Si interface when a 1.0-nm-thick SiO2 film oxidized by an atmospheric ozone is removed by a diluted HF etching. It is revealed that the homogeneous lateral oxide growth, i.e., layer-by-layer growth, proceeds at room temperature by an active oxidant such as ozone.
Silicon based quadrupole mass spectrometry using microelectromechanical systems
Authors: Taylor S. , Tindall R. F. , Syms R. R. A.
Published: July 2002

The conventional quadrupole mass spectrometer (QMS) arrangement uses circular metallic rods as the mass filter excited electrically at voltages up to 1 kV depending upon the application. If the size and voltages can be reduced then the range of applications for QMS instruments would increase. The application of microelectromechanical systems (MEMS) technology allows the fabrication of submillimeter versions of such structures. In this article the development of a miniature QMS is reported in which the conventional rod arrangement has been replaced with a microengineered version. The structure is made in silicon with metallized specially drawn glass fibers of length 20–30 mm and diameter 0.5 mm to act as the quadrupole rods. This is about one order of magnitude smaller than most conventional QMS filters, with the potential for further reduction in size. The MEMS mass filter was mounted onto a commercial ion source, which was in turn attached to a vacuum flange and supplied by an electronic drive circuit at 6 MHz. Mass spectra in the range 0–50 amu for a range of operating conditions have been obtained indicating a linear mass scale and a best resolution at 10% peak height of around 30. The use of pole bias applied to the rods is shown to be beneficial. Reliable QMS operation was obtained up to a pressure of 10−2 mbar.
Metallic electronic states on SrTiO3 (110) surface: Anin situconduction measurement
Authors: Bando Hiroshi , Ochiai Yuichi , Aiura Yoshihiro , Haruyama Yuichi , Yasue Tomoyoshi , Nishihara Yoshikazu
Published: July 2002

An in situ conduction measurement of metallic electronic states on the SrTiO3 (110) surface is reported. The electronic states were observed on the SrTiO3 (110) surface in our previous work after annealing in ultrahigh vacuum (UHV) at relatively low temperature, 800 °C, based on a sharp Fermi edge detected by ultraviolet photoemission spectroscopy and finite zero-bias differential conductance by scanning tunneling spectroscopy. The electric conductance measurement is performed in order to verify the metallic feature of the surface as a macroscopic property. For the measurement, a sample holder is designed which enables both annealing in UHV by electron beam and four-probe electric conduction measurement with uniform electric field. Conductance contributed by bulk is separated by measuring the decrease of total conductance by adsorption of oxygen at room temperature, which is supposed to modify only the surface electronic states. Surface conductance is deduced between 150 to 300 K and showed a metallic feature. Moreover, the surface conductance during exposure to oxygen is monitored in situ, and shows a reversible-like change depending on the oxygen pressure. This possibly evidences that the oxygen molecules which temporarily stay on the surface suppress the conduction by surface electrons.
Molecular dynamics simulations of ion self-sputtering of Ni and Al surfaces
Authors: Hanson D. E. , Stephens B. C. , Saravanan C. , Kress J. D.
Published: July 2002

We present results of molecular dynamics simulations of Ni+ impacting Ni(111) and Al+ impacting Al (111) and amorphous Al surfaces. Sputter yields and sticking probabilities were calculated as a function of ion fluence, impact angle (0–90°) and energy (25–150 eV). We find that the simulated sputter yields are in reasonable agreement with experiments and a commonly used empirical formula. For Al+ impacting at normal incidence, sputter yields were approximately the same for both Al(111) and amorphous Al. The initial penetration depth exhibited a linear dependence with velocity, and was approximately the same for both Al+/Al(111) and Ni+/Ni(111) if the distances were scaled by the lattice constants. The average calculated time between ion impact and atom ejection was less than 25 fs for 100 eV Ni+/Si(111) sputter events.
Investigations of effects of bias polarization and chemical parameters on morphology and filling capability of 130 nm damascene electroplated copper
Authors: Chang Shih-Chieh , Shieh Jia-Min , Lin Kun-Cheng , Dai Bau-Tong , Wang Ting-Chun , Chen Chia-Fu , Feng Ming-Shiann , Li Ying-Hao , Lu Chih-Peng
Published: July 2002

Through elucidating the effects of current density, cupric ion concentration, bath temperature, and air agitation on plating uniformity and filling capability of copper electroplating, the deposition of copper in an acid copper electrolyte will be illustrated to scale down to the sub-0.13 μm features with uniform plating, which is required by chemical mechanical polishing in current damascene techniques. In order to achieve the defect-free filling in sub-0.13 μm vias and trenches, the electrolyte must be composed of proper amounts of cupric ions, sulfuric acid, chloride ions, wetting agent, and filling promoter. The supplied current controlled at a lower current density, agitation acceded to the electroplating process were found as further keys. In the electrolyte, the filling promoter was consisted essentially of thiazole derivatives with benzyl groups and amino-group (−NH2) offering sufficient inhibition on copper depositing and selective inhibition gradient. Moreover, a lower resistivity film and higher filling capability could be obtained by using periodic pulse current plating as compared with direct current plating.
InP (110) by Time-resolved XPS
Authors: Deng Z. W. , Kwok R. W. M. , Lau W. M. , Cao L. L.
Published: July 2002

Time-resolved binding energy (BE) changes of the In 3d5/2 level of heavily doped n-InP (100) (S-doped with a carrier density of 2.4 × 1017 cm−3) and p-InP (100) (Zn-doped with a carrier density of 3.9 × 1018 cm−3) after cleaving in UHV were measured by XPS. Also presented are spectra of survey, In 3d5/2 and P 2p levels after the BE stopped shifting. Measurements were carried out on the in situ cleaved (110) facets. The results show nearly flat band surface as cleaved in UHV. The subsequent binding energy changes reflected the Fermi level shift in the band gap relative to the valence band maximum induced by surface states which are believed to be a consequence of surface lattice relaxation after cleavage. The accurate BE of the as cleaved P 2p level can be obtained via interpolation according to the BE changes of In 3d5/2.
Development of tin oxide synthesis by plasma-enhanced chemical vapor deposition
Authors: Robbins Joshua J. , Alexander Robert T. , Bai Mailasu , Huang Yen-Jung , Vincent Tyrone L. , Wolden Colin A.
Published: July 2002

Transparent conducting oxide (TCO) thin films have been synthesized to date primarily by either physical vapor deposition or thermal chemical vapor deposition. Plasma-enhanced chemical vapor deposition (PECVD) offers potential advantages over these techniques, but it has not been applied extensively to TCO synthesis. In this article we report on the use of PECVD to deposit transparent, conducting tin oxide films from mixtures of SnCl4 and O2. These films were deposited on glass substrates at temperatures between 150 and 350 °C. The growth rate, optical, electrical, and structural properties were examined as a function of plasma power, substrate temperature, and gas composition. Increasing rf power revealed a rise in deposition rate with no effect on electrical properties, while both substrate temperature and oxygen flow rate were found to significantly influence resistivity. The effect of annealing was also examined, and it was found that annealing at 250 °C significantly improved the electrical properties. The optical transparency of all films was greater than 86% in the visible spectrum, and electrical resistivities as low as 2.1×10−3 Ω cm have been achieved.
Chemical composition, morphology, and deep level electronic states of GaN (0001) (1×1) surfaces prepared by indium decapping
Authors: Young A. P. , Brillson L. J. , Naoi Y. , Tu C. W.
Published: July 2002

Ordered GaN (0001) (1×1) surfaces are prepared after removal from the growth chamber via thermal desorption of a thin In cap layer at 650 °C in combination with one thermal flash of Ga metal to reduce residual O and C contamination. Auger electron spectroscopy (AES) and low energy electron-excited nanoscale luminescence (LEEN) spectroscopy results show that In can prevent contamination during atmospheric exposure if it can cover the surface uniformly. LEEN spectra of the ordered surface show that the In capping layer is desorbed from the GaN without reacting to produce InxGa1−xN or diffusing into the GaN to produce new localized states. Subsequent atomic force microscopy (AFM) measurements reveal an atomically smooth film plus Ga droplets residual to the flash annealing. These results suggest that In decapping may be useful in obtaining clean, LEED-ordered GaN surfaces after transport in air with a minimum of UHV treatment.
Simple design for the transportation of ex situ prepared hydrogen passivated silicon
Authors: MacLaren D. A. , Curson N. J. , Atkinson P. , Holst B. , Johnson D. J. , Allison W.
Published: July 2002

We present a design for a simple, reliable, and robust storage container suitable for the transportation of silicon crystals between clean room and experiment after hydrogen passivation by a “wet-chemical” process. The container stores the crystal in an inert atmosphere that is depleted of the water and oxygen responsible for surface oxidation. An atomic-force microscopy study of the surfaces of stored crystals confirmed that the storage method was successful and that surface oxidation can be impeded for at least 24 h. Our design is also suitable for the storage of other systems that degrade under atmospheric conditions.
Growth and characterization of Fe(100)/InAs(100) hybrid structures
Authors: Ohno Hiroshi , Yoh Kanji , Doi Toshihiro , Subagyo Agus , Sueoka Kazuhisa , Mukasa Koichi
Published: July 2002

We report on the growth of planar/patterned Fe thin films on InAs(100) substrates and their subsequent characterization using reflection high-energy electron diffraction, low-energy electron diffraction, superconducting quantum interference device, and four-terminal contact resistance measurements. Epitaxial growth of body-centered-cubic Fe crystal on InAs(100) was verified for growth temperatures of 23 °C and 175 °C. A patterned Fe wire array showed clear uniaxial shape anisotropy with the easy axis along the wire direction. Its coercive force was found to depend on the growth temperature and the width of the Fe wires. Four-terminal contact resistance measurement of Fe/n-InAs revealed that Fe forms decent ohmic contact to the InAs substrate with a resistivity of the order of 10−6 Ω cm2. Samples grown at room temperature showed equally decent or even better magnetic and electrical characteristics than those obtained by higher temperature growth. These results indicate that the Fe/InAs hybrid structures have definite potential for spin-related semiconductor devices with practical process sequences.
Characterization of annealing effects of low temperature chemical vapor deposition oxide films as application of 4H-SiC metal–oxide–semiconductor devices
Authors: Cho Won-ju , Kim Young-cheol
Published: July 2002

The characteristics of charge trapping and interface states for low temperature chemical vapor deposition (LTCVD) oxide formed on 4H-SiC as carbon-free gate oxide has been studied. Observation of a large flatband voltage shift indicated the presence of many negative oxide charges in the as-deposited LTCVD oxide. Heat treatment was carried out to improve the quality of the LTCVD oxide in various conditions. Interface state density, flatband voltage, and effective oxide charge were decreased with the heat treatment. The heat treatment also greatly improved charge trapping characteristics against electron injection.
Diamond nucleation enhancement on reconstructed Si(100)
Authors: Van Chiem Chu , Kim Jung-Hyun , Shin Hyung-Shik , Seo J. M.
Published: July 2002

Diamonds have been efficiently nucleated on the flash-annealed and reconstructed silicon (100) substrate by hot filament chemical vapor deposition. A relatively high diamond nucleation density of about 1010 cm−2 in the nucleation time of only 20 min was confirmed by a Raman peak at the wave number of 1332 cm−1 and a scanning electron microscope image of the oriented nuclei with square-like shapes. The core-level spectra of C1s and Si2p using x-ray photoelectron spectroscopy indicated that the diamond had been nucleated on the C-modified substrate believed to be a SiC layer. If so, this study demonstrates that the diamond can be efficiently nucleated on a high quality SiC surface.
Technology CAD: Device simulation and characterization
Authors: Grasser T. , Selberherr S.
Published: July 2002

State-of-the-art devices are characterized by the occurence of large gradients in the electric field. Due to the complex doping profiles which utilize ultrashallow junctions to obtain an optimum tradeoff between short-channel effects and parasitic resistances, two-dimensional numerical simulation of these structures is mandatory. From the modeling point of view, nonlocal and quantum effects gain more and more importance which need to be properly accounted for. We review the requirements for successful numerical simulation of these semiconductor devices. In addition, we give an overview of recent activities concerning device calibration and inverse modeling since inverse modeling of the doping profile in conjunction with calibration of the model parameters has proven to be an effective method of two-dimensional doping profile extraction.
Effects of multilayer mask roughness on extreme ultraviolet lithography
Authors: Deng Yunfei , Pistor Tom , Neureuther Andrew R.
Published: July 2002

Effects of multilayer roughness are explored based on rigorous electromagnetic simulation with TEMPEST and aerial image calculation with SPLAT. The TEMPEST simulation on small roughness features using an average material properties technique is validated by comparison with the simulation using finer gridding and approximate analytical methods. Simulations for rms roughness from 0 to 1.4 nm show a reflectivity reduction, a phase shift, and a polarization dependence. Midsize Gaussian defects are shown to be slightly less printable in the presence of roughness. For extreme ultraviolet lithography systems with roughness rms of 0.15 nm, the above effects are very second order.
Magnetic and structural properties of Fe, Ni, and Mn-implanted SiC
Authors: Theodoropoulou N. , Hebard A. F. , Chu S. N. G. , Overberg M. E. , Abernathy C. R. , Pearton S. J. , Wilson R. G. , Zavada J. M. , Park Y. D.
Published: July 2002

Direct implantation of Fe, Ni or Mn at doses of 3–5×1016 cm−2 into p-type 6H-SiC substrates was carried out at a sample temperature of ∼350 °C. Subsequent annealing was performed at 700–1000 °C for 5 mins. Residual damage in the form of end-of-range defects and dislocation loops in the region from the surface to a depth of ∼0.20 μm were examined by transmission electron microscopy. To the sensitivity of both x-ray diffraction and selected area diffraction pattern analysis, no secondary phases could be detected. Signatures of ferromagnetism were observed in all the highest dose samples, with apparent Curie temperatures of 50 K (Ni), 250 K (Mn), and 270 K (Fe).
Three-dimensional site control of self-organized InAs quantum dots by in situ scanning tunneling probe-assisted nanolithography and molecular beam epitaxy
Authors: Kohmoto S. , Nakamura H. , Nishikawa S. , Asakawa K.
Published: July 2002

Self-organization sites of InAs quantum dots (QDs) are arranged to form three-dimensional (3D) lattices by ultrahigh vacuum in situ processing. In-plane QD arrangement in the 3D lattices is initially defined by site-controlled InAs QD arrays fabricated by a scanning tunneling microscope probe-assisted technique. With the QD arrays used as strain templates, self-organized InAs QDs are vertically aligned by multistacking, resulting in the 3D QD lattices. The photoluminescence from the 3D QD structures is investigated at room temperature.
Vacuum system design for the 3 GeV-proton synchrotron of JAERI-KEK joint project
Authors: Kinsho Michikazu , Nishizawa Daiji , Saito Yoshio , Suzuki Hiromitsu , Yokomizo Hideaki
Published: July 2002

A rapid-cycling magnetic field is necessary to operate a synchrotron with a high repetition rate for the 3 GeV proton synchrotron of JAERI-KEK joint project. Since an eddy-current effect in a metal duct would produce an unacceptable perturbation of the magnetic field and unnecessarily large ohmic losses, an alumina ceramic is a candidate material for vacuum ducts in the dipole and quadrupole magnets. The required beam apertures, being a circular cross section, are 187 and 247 mm in diameter for the vacuum ducts to be installed in the dipole and quadrupole magnets, respectively. The duct lengths for each magnet are 3.5 and 1 m. Since such a long duct is difficult to make with accuracy in the radial dimension, when sintered at once, it can only be manufactured by jointing duct segments of about 0.5 m long. The mechanical strength and deterioration under a high level of radiation were examined for various kinds of alumina ceramic and for the joint. Almost all of the ceramics to be tested have a sufficiently high flexural strength of 300 MPa, or more, before irradiating with a 2.5 GeV-electron beam, and they did not show any significant deterioration in the flexural strength as far as an absorption dose is up to 1000 MGy.
Low-energy electron point source microscope as a tool for transport measurements of free-standing nanometer-scale objects: Application to carbon nanotubes
Authors: Dorozhkin P. , Nejoh H. , Fujita D.
Published: July 2002

We have developed a simple and reliable technique for two-terminal transport measurements of free-standing wire-like objects. The method is based on the low-energy electron point source microscope. The field emission tip of the microscope is used as a movable electrode to make a well-defined local electrical contact on a controlled place of a nanometer-size object. This allows transport measurements of the object to be conducted. The technique was applied to carbon nanotube ropes.
Penning source for ion implantation
Authors: Flemming J. P.
Published: July 2002

A cold-cathode Penning-type ion source with axial extraction has been developed to provide the milliampere ion currents needed for high volume, high throughput ion implantation. For solid feed material, the source is fitted with an oven that is concentric with the anode. The oven windings heat the anode to prevent condensation of feed vapor in the source. The ion beam is extracted through a three-element electrode assembly which provides lens action. The optical effect of space-charge forces completes beam formation. The output consists of up to 12 mA ion current in the form of a beam that is parallel to better than 10 mR and of diameter less than 2.5 cm. The beam contains 15% boron, 30% phosphorus, 50% arsenic when the source is run on BF3, 10% PH3, or solid arsenic. The source allows analyzed currents in the 1–3-mA range to be produced for periods of about 40 h.
Thickness determination of ultrathin films by Auger electron spectroscopy
Authors: Holloway P. H.
Published: July 2002

The feasibility of using Auger electron peak-height ratios for film thickness determination has been demonstrated for ultrathin films of chromium oxide on gold substrates. The range of equivalent film thicknesses determined was from 3 to 67 Å, but the technique can measure thicknesses up to ∠100 Å. Using peak-height ratios from Auger electrons of different energies, the uniformity of the chromium oxide film was demonstrated. It was also demonstrated that argon-ion sputtering removed the chromium oxide in a nonuniform manner. The mean free path lengths of 70-, 527-, and 2024-eV electrons in chromium oxide were determined to be 4.3, 14, and 28 Å, respectively.
Abstract: Microstructure and tensile properties of low-oxygen electrodeposited Cu
Authors: Schuler F.T. , Mansfeld F.
Published: July 2002

The relationships between microstructure, strength, and ductility of electrodeposited copper (EDCu) has been studied for EDCu in the as-deposited condition. Tensile testing was performed at 25 ° and 370 °C. The EDCu was made from a reagent-grade copper sulfate, 225±10 g/liter, reagent-grade sulfuric acid, 68±5 g/liter, and an electrolyte containing 0.4–0.8 g/liter pentose. The electrolyte temperature was 27 °–32 °C. Anodes were high-purity OFHC copper. Deposition rates were varied from 0.015 to 0.075 mm/h, which is equivalent to current densities of about 1.1–5.5 A/dm2. The EDCu produced under these conditions was very pure (99.995%).

Sheets of EDCu approximately 30×22 cm × 0.125–0.15 cm thick were made on a stainless-steel mandrel, separated from the mandrel, and machined into standard, flat-type tensile coupons having a reduced section 0.635 cm in width and 0.125–0.15 cm thick. Overall sample length was about 11.4 cm.

The ultimate tensile strength at room temperature of the EDCu changed directly with increased deposition rate. A four- to five-fold increase in deposition rate, 0.015 mm/h up to 0.075 mm/h, corresponding to a four- to five-fold increase in current density, produced an increase of 25% or more in tensile strength (242–310 MN/m2). The 0.2% offset yield strength was increased by 40% (105–147 MN/m2) by this same increase in deposition rate. Microstructure of the deposit decreased in size from a large columnar duplex structure to an extremely fine columnar structure as a result of the increased deposition rate. Elongation over a 0.5-in. (1.27-cm) gauge length decreased from over 50% to about 25%.

Tensile strength of the EDCu when tested at 370 °C was 70–90 MN/m2, while yield strength is 35–41 MN/m2, with no assignable effect from the deposition rate. The microstructure shows little or no change after the 370 °C exposure during testing, indicating that increases in as-deposited, room-temperature strength were induced by the deposition process, most likely by internal stresses. However, elongation of the EDCu was consistently higher at 370 °C (15%–20%) for the material deposited at 4–5 A/dm2 than for material deposited at 1–3 A/dm2, which exhibits only 1%–5% elongation.

Impurities such as dissolved organics or fine particulates increase strength above that for pure material, with some EDCu having tensile strength as high as 520 MN/m2. Such material was very brittle when tested at 25 ° and 370 °C. Primary usage of the EDCu has been in electroformed rocket-engine combustion chambers and as a barrier to embrittlement of nickel and nickel alloys used in high-pressure gaseous hydrogen environments.
Simultaneous observations of partially oxidized surfaces by AES and SIMS for Al, Si, Ti, V, and Cr
Authors: Komiya S. , Narusawa T. , Satake T.
Published: July 2002

The advantage of performing simultaneous SIMS and AES analysis together with measurements of sputtering rates is demonstrated by studies of oxidized Al on Si. As the OKLL Auger peak increases, due to increased oxygen coverage, there is enhanced emission of metal ions. Normalized SIMS and Auger signals for Al, Si, Ti, V, and Cr are intrinsic to each metal−oxygen system. From estimates of the escape depth of OKLL Auger electrons, the mean escape depths of metal ions from oxide were estimated. A step−like decrease in sputtering rate is observed and correlated with the thickness of the oxide layer. The Ag−O system was also studied and found to give an anomalous effect.
Sputtering in the surface analysis of solids: A discussion of some problems
Authors: Coburn J.W.
Published: July 2002

Ion-bombardment sputtering is used in combination with various analytical approaches in the surface analysis of solid samples. Although the advantages of sputter etching in this application far outweigh the disadvantages, there are several ways in which the sputter-etching process can cause interpretational difficulties. The characteristics of the sputter-etching process which are responsible for these difficulties include: (a) the fact that the elemental composition of a sputter-etched surface will in general be different from that of the bulk solid, (b) the tendency of certain materials to develop extensive microtopographical structure when they are subjected to ion bombardment, and (c) the fact that ion bombardment can cause motion of atoms in the sample by direct momentum transfer, cascade mixing, enhanced diffusion, or, in the case ofionized species, enhanced drift motion. A discussion of these effects wil be presented and an attempt will be made to assess their significance in the analysis of solid samples.
Problems with turbomolecular pumps in magnetic fields
Authors: Becker W. , Henning J.
Published: July 2002

With the increase of the application of turbomolecular pumps in plasma physics the problem of strong magnetic fields in the vicinity of the turbomolecular pumps comes up more and more frequently. If the rotor of a turbomolecular pump turns with high speed in a magnetic field eddy currents in the rotor will cause undesirable heating of the pump. The maximal magnetic flux density specific for each turbomolecular pump is determined by experiment for a series of pumps. For higher densities of the magnetic field shielding elements must be applied, because excessive heating of the pump rotor would cause destruction of the pump.
Surface electronic structure studies of GaAs (110)
Authors: Knapp J. A. , Eastman D. E. , Pandey K. C. , Patella F.
Published: July 2002

Angle-resolved photoemission using synchrotron radiation from GaAs (110) has been studied in conjunction with tight binding calculations of the surface electronic structure. Emission from two new surface resonances−which were predicted to exist only for a relaxed surface-have been identified near the edges of the surface Brillouin zone at ? and ?′. Also, measurements of the dispersion of the As-derived surface state near the valence band maximum, first reported elsewhere, have been extended from ? to the zone edge ? and a band width of 0.6 eV has been determined. All of these observations, including those reported elsewhere of intrinsic surface states on GaAs (110) are accounted for by a tight binding model calculation for a relaxed surface (∠19° bond angle rotation).
Wave functions and (110) surface structure of III–V compounds
Authors: Miller D. J. , Haneman D.
Published: July 2002

New electron paramagnetic resonance determinations of the dangling orbital on Ga atoms on the cleavage surfaces of GaP are compared with corresponding data for GaAs and A1Sb. Using a bond-orbital approach the (110) surface structure for all three compounds is reconstructed, with the surface cation withdrawing towards a near planar configuration with its three neighbors. The EPR results provide the first opportunity of experimentally evaluating surface-charge densities calculated by the pseudopotential method. Surface wavefunctions determined from the measurements are compared with the results of self-consistent pseudopotential calculations of GaAs surfaces, with and without the above reconstruction. It is concluded from this and other information, that current pseudocharge densities for surfaces are not reliable, due in part to the use of a local form of the pseudopotential.
Intrinsic surface states and Fermi-level pinning at metal–semiconductor interfaces
Authors: Mele Eugene J. , Joannopoulos J. D.
Published: July 2002

We find that the well-known transition in the Fermi-level pinning behavior of metal–semiconductor contacts can be quantitatively characterized in a fundamental way. Our model makes use of the clean semiconductor surface state energies, predicts the onset of the covalent–ionic transition, and explains strong Fermi-level pinning at metal contacts to covalent materials with large optical gaps and low bond polarizabilities.
Copper–polyvinyl alcohol interface: A study with XPS
Authors: Burkstrand James M.
Published: July 2002

It has been known for some time that oxygen treatment of a polymer surface can lead to enhanced adhesion with metals. This has prompted us to investigate the metal–polymer interface of an oxygen-containing polymer, polyvinyl alcohol. We have vapor-deposited copper on the clean polymer surface and examined the interface with x-ray photoemission spectroscopy (XPS). At very low copper coverages, about 0.005 monolayer, the copper 2p3/2 core level binding energy is 1.2 eV larger than the bulk copper value. As the copper coverage increases, this core level shift decreases; at a coverage of one monolayer this shift is sometimes as large as 0.2 eV. At a copper coverage of two monolayers, the 2p3/2 core binding energy is the same as it is in bulk copper, 932.85 eV. In addition to these changes, the carbon 1s and oxygen 1s core levels are observed to change with the addition of copper. The intensity of the C 1s level at 286.6 eV, associated with a C–O group, is observed to decrease faster than that at 285.0 eV which is associated with a CH2 group. At the same time a new peak in the 0 1s spectrum is formed at 530.6 eV, 2.4 eV less than the original level. These changes indicate the formation of a copper–oxygen–carbon complex at the interface.
Preferential lateral chemical etching in reactive ion etching of aluminum and aluminum alloys
Authors: Schaible P. M. , Schwartz G. C.
Published: July 2002

Reactive ion etching of aluminum and its alloys in CCl4/argon plasmas produces vertical etch profiles and residue-free etched regions. However, under certain conditions, preferential lateral chemical etching occurs, which produces pits in the surface of the metal along the edges of the lands. The lateral etching is due to a thermally activated process and is related to the structure of the films. The extent of attack can be reduced by annealing the films at 450°C before etching. Al–Cu films deposited onto heated substrates are more susceptible to attack than those evaporated at lower temperatures. This apparent contradiction has not been resolved. The effects of etching temperature, plasma parameters, and film structure will be discussed. Scavenging of the responsible species by additions of H2 or O2 to the plasma is not successful.
Effect of periodic chemical variation on the mechanical properties of Ta foils
Authors: Springer R. W. , Ott N. L. , Catlett D. S.
Published: July 2002

It is known from previous work [R. W. Springer and D. S. Catlett, J. Vac. Sci. Technol. 15, 210 (1978)] that the residual gases can play a significant role in determining the resultant chemical purity of vacuum-deposited films. The ability to alter the chemical composition and structure of a solid on a microdimensional scale can provide a means to tailor and control the mechanical properties of the material [see R. W. Springer and D. S. Catlett, Thin Solid Films 54, 197 (1978)]. Acetylene gas was admitted to the chamber over approximately two orders of magnitude of pressure during Ta deposition. Residual gas analysis was used to verify that a reaction between the Ta film and the gas occurred. Subsequent Auger analysis showed that the carbon in the films could be predicted using a simple pressure-versus-rate equation. The pulsed gas process (PGP) has been applied to the electron beam gun deposition of Ta. Tensile test specimens a few μm thick have been produced show fracture strengths varying from ∠ 170 to ∠860 mPa for pure to highly pulsed runs. The fracture strength loosely follows a Hall–Petch relation relating fracture strength to the time between pulses. Although diffusion of the carbon smoothes out the chemical period, it is thought that the remaining structure accounts for the strength enhancement.
Quantitative characterization of high strength aluminum foils vapor deposited on curved surfaces
Authors: Springer R. W. , Barthell B. L. , Rohr D.
Published: July 2002

The pulsed Gas Process (PGP) has been used to produce Al/AlxOy The pulsed Gas Process (PGP) has been used to produce Al/AlxOy layered coatings on a cylindrical surface. Previous work1 has shown that the yield strength and surface morphology of aluminum films deposited at normal incidence is quite sensitive to the spacing of the oxygen gas pulse. The mechanical testing data follow a Hall–Petch equation for the yield strength. This gives an ideal range of conditions for test on curved surfaces. Free standing aluminum foils on the order of 20–35 μm thick have been deposited using PGP variations on a rotating cylindrical substrate with varying angles of deposit. The results show porosity in the unpulsed material, and fully dense material in highly pulsed material deposited at ±60° or less settings. The fully dense material shows ductility and the yield strength is reduced by a factor of 0.84 over the predicted flat plate strength.
Dry etching for pattern transfer
Authors: Lehmann H. W. , Widmer R.
Published: July 2002

Dry etching or plasma-assisted etching (ion beam milling, plasma etching and reactive sputter etching) has become an indispensable preparation technique for high resolution pattern transfer in IC manufacturing and other areas of microfabrication. Etching can either be due to the purely physical process of momentum transfer from ions to the solid surface (e.g. inert ion etching) or due to chemical reactions of reactive species, produced in the plasma, with the solid surface resulting in a volatile reaction product (e.g. plasma etching in a barrel reactor). However, in most dry etching methods both effects play a major role and it is possible to optimize etch selectivity and the shape of the etched profile by a proper choice of parameters.
Correction for loss effects in valence-band XPS spectra by deconvolution
Authors: Davis G. D. , Lagally M. G.
Published: July 2002

We present XPS valence band spectra for GaAs (110) and GeSe (001) that have been corrected for coherent loss effects by deconvolution of an instrument/loss function that includes a source function for an unmonochromatized source, a backscattered-electron spectrum to account for energy losses, and an analyzer function. The results are compared with background-subtracted spectra. The deconvolution yields spectra that have significantly greater intensity deep in the band, bringing measurements into closer agreement with theory than is achieved with background subtraction.
Technology challenges for ultrasmall silicon MOSFET’s
Authors: Dennard R. H.
Published: July 2002

Work on silicon MOSFET devices scaled down to half-micron dimensions is gathering momentum in research labs for VLSI applications. Further reductions in device geometries by only a factor of two will bring us to the edge of some fundamental barriers to miniaturization. Design requirements for very thin layers in the device structure lead to resistance effects, statistical fluctuation of doping impurities, and increased concern for interface properties. Scaling down of applied voltage is difficult because built-in junction potentials and other small voltage terms are no longer negligible. Increased susceptibility to spurious operation or permanent damage from alpha particles, cosmic particles, or other high-energy radiation is reviewed.
FET fabrication using maskless ion implantation
Authors: Kubena R. L. , Anderson C. L. , Seliger R. L. , Jullens R. A. , Stevens E. H. , Lagnado I.
Published: July 2002

Focused ion beams from Au–Si, Au–Be, and B–Pt liquid–metal–alloy ion sources have been used to implant GaAs and Si. An Al stopping layer on the wafers was used to trap the Au and Pt ions. Hall mobilities consistent with those in bulk materials have been obtained for B-doped Si and Be-doped GaAs. In addition, a 2000-Å-diam Au–Si focused ion beam was used to implant the doped regions of GaAs metal-semiconductor gate field-effect transistors. The 140-keV Si++ beam component was deflected under computer control to implant 8×50 μm active channel regions and 16×50 μm contact regions. The devices were metalized using conventional lithography. DC electrical characteristics of the 1.5-μm-gate-length devices are comparable to those of conventionally processed devices of identical geometry.
Proximity parameters determination for electron beam lithography using a novel technique
Authors: Shaw Ching-Hao
Published: July 2002

A technique of acquiring proximity parameters is presented. This technique utilizes a design pattern of line-density exposure wedge. The pattern was written with electron-beam line scans of line densities ranging from 500 Å to 5-μm spacings. With small spatial scales built-in, the proximity data are obtained through a supplemental, qualitative end point detection scheme. The end point is determined by the clearance of resist between scan lines. Since there are many scan lines in every exposure, each datum is a statistical average. Examples of using this technique are presented to determine proximity parameters for proximity corrections. In addition, they may be determined as a function of the condenser lens setting, which relates to the electron probe diameter. A variation of the technique described above indicates that the forward scattering parameter is dependent upon resist development time.
A simple optical thin film deposition monitor using LED’s and fiber optics
Authors: Gale M. T. , Lehmann H. W. , Heeb E. , Frick K.
Published: July 2002

A thin film deposition monitor is described which can be used to monitor the rf-sputter deposition of dielectric and thin metallic films on transparent substrates in a multi-target system. The monitor uses a green and a red LED as a light-source, a bundle of optical fibers to transmit the light into and out of the sputtering chamber and Si-photocells as detectors. The LED’s are pulsed at two different frequencies and phase-sensitive detection allows the simultaneous monitoring of the substrate reflectivity at two different wavelengths. Applications of the deposition monitor include the exact control of individual layers in multilayer dielectric filter structures and monitoring the deposition of very thin, semitransparent metallic films.