bluuebunny/crossref_metadata_2025 huggingface dataset:
Redesign of Submerged Structures by Large Admissible Perturbations
Authors: Blouin Vincent Y. , Bernitsas Michael M.
Published: July 2002

The method of large admissible perturbations (LEAP) is a general methodology, which solves redesign problems of complex structures without trial and error or repetitive finite element analyses. When forced vibration constraints are incorporated into the redesign problem, damping and added mass due to the presence of fluid must be included into the model. The corresponding terms introduce theoretical and numerical difficulties, which are treated in this paper. The LEAP method has been implemented into a Fortran computer code RESTRUCT, developed at the University of Michigan. The redesign process is mathematically formulated as an optimization problem with nonlinear constraints, called general perturbation equations. First, a finite element analysis of the initial structure is executed. Then, the results are postprocessed by code RESTRUCT using an incremental scheme to find the optimum solution for the problem defined by the designer. Accurate determination of nonstructural terms, such as fluid added mass, is generally detrimental as far as forced response analysis is concerned. In redesign problems, however, simple but realistic models can be used. A simple transformation of the structural mass matrix is used to compute the added mass matrix and its dependency on the redesign variables. The presence of non-structural terms in the general perturbation equations requires the development of a new LEAP algorithm for solution of the optimization problem. A simple cantilever beam with 100 degrees of freedom is used to validate the fluid added mass model. The developed method and algorithm are then applied to a partially submerged 4,248 degree of freedom complex structure modeled with beam elements.
Improving Formability in Sheet Metal Stamping With Active Drawbead Technology
Authors: Bohn M. L. , Xu S. G. , Weinmann K. J. , Chen C. C. , Chandra A.
Published: July 2002

Aluminum is expected to gain popularity as material for the bodies of the next generation of lighter and more fuel-efficient vehicles. However, its lower formability compared with that of steel tends to create considerable problems. A controllable restraining force caused by adjusting the penetration of drawbeads can improve the formability. This paper describes the effects of temporal variations in drawbead penetration on the strain distribution in a symmetric stamped part. Comparison of the results of numerical simulations with the corresponding experimental results shows that the predictions of strain distribution on the panel are in very good agreement. Furthermore, forming limit diagram analysis indicates that the active drawbead concept is beneficial to the formability of AA 6111-T4.
Dynamic Analysis and Diagnosis of a Cracked Rotor
Authors: Zhou, Tong , Xu, and Jianxue , Sun Zhengce
Published: July 2002

In this paper, the nonlinear dynamical behavior of a horizontal Jeffcott rotor system with a transverse crack is analyzed numerically. A new acceleration scheme is suggested to reduce shocks to the rotor and diagnose the existence of cracks. Particular stress is laid on the analysis of the spectrum of transient and stable response by using a new approach of signal processing, which could erase both the gravitational effect and the free vibration with inherent frequency for the purpose of accurate crack detection.
Finding Nonconvex Hulls of QFT Templates
Authors: Boje Edward
Published: July 2002

To reduce the computational overhead in quantitative feedback theory (QFT) bound computation, only the (nonconvex) outside edge of a template should be used. This note presents an algorithm to calculate the nonconvex hull with minimum concave radius defined by the feedback system specifications. [S0022-0434(00)01301-0]
Prediction of the Circumferential Film Thickness Distribution in Horizontal Annular Gas-Liquid Flow
Authors: Hurlburt Evan T. , Newell Ty A.
Published: July 2002

This paper develops a liquid film symmetry correlation and a liquid film thickness distribution model for horizontal annular gas-liquid pipe flows. The symmetry correlation builds on the work of Williams et al. (1996) (Droplet Flux Distributions and Entrainment in Horizontal Gas-Liquid Flows,” Int. J. Multiphase Flow, Vol. 22, pp. 1–18). A new correlating parameter is presented. The liquid film thickness model is based on the work of Laurinat et al. (1985) (Film Thickness Distribution for Gas-Liquid Annular Flow in a Horizontal Pipe,” PhysicoChem. Hydrodynam., Vol. 6, pp. 179–195). The circumferential momentum equation is simplified to a balance between the normal Reynolds stress in the film’s circumferential direction and the circumferential component of the weight of the film. A model for the normal Reynolds stress in the circumferential direction is proposed. The symmetry correlation is used to close the model equations. The model is valid for films with disturbance waves, and is shown to be applicable to air-water flows over a range of conditions from low velocity asymmetric to high velocity symmetric annular flows. [S0098-2202(00)02102-7]
Editorial
Authors: Katz Joseph
Published: July 2002

[S0098-2202(00)03202-8]
Numerical Simulation of Plastic Deformation of Pressurized Oblate Spheroid-Inscribed Single-Curvature Shells
Authors: Zhang S. H. , Danckert J. , Wang Z. R. , Nielsen K. B.
Published: July 2002

The integral hydro-bulge forming (IHBF) technology is used for manufacturing oblate spheroidal shells. A mild steel oblate spheroidal shell and a stainless steel shell were manufactured by using this new technology. The IHBF processes of the experimental shells are simulated by using an explicit finite element code, the numerical results are discussed and compared with the experimental results. Based on the numerical simulations and experimental results, a few suggestions are made for improving the new technology. [S1087-1357(00)71201-9]
AES Study of the First Row of Transition Metals
Authors: Duarte Jorge , Ray M. A.
Published: July 2002

AES spectra were obtained from elements of the first row of the transition metals using a Perkin Elmer 595 Scanning Auger Microprobe. The goal was to obtain spectra which represented what would normally be obtained under typical operating conditions. Auger spectra were take from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, and Ge samples under identical conditions. Each elemental spectrum was obtained with electron beam energies 3, 5, and 10 keV using a 1 μA electron beam. A Cu sample was also used to obtain data in calculating the signal-to-noise ratio and in checking instrument calibration. Signal-to-noise ratios were obtained using the primary Cu LMM peak located at 916 eV. The signal-to-noise ratios were measured before and after analysis and were 20, 30, and 70 for electron beam energies of 3, 5, and 10 keV, respectively. The instrumental energy resolution used for all of these measurements was 0.6% ± 0.03%.
Characterization of Polyethylene by XPS
Authors: Mansour Azzam N. , Beard Bruce C.
Published: July 2002

X-ray photoemission spectra of the core and valence levels for high density polyethylene are presented. Low resolution (i.e., pass energy of 89.45 eV) XPS survey scan and higher resolution (i.e., pass energy of 35.75 eV) multiplexes of the C 1s, C KLL (x-ray induced Auger lines), and valence band region were collected on a Perkin-Elmer/Physical Electronics model #5400 spectrometer using non-monochromated Mg x rays. These spectra serve as reference for identifying the chemistry and thickness of hydrocarbon contaminants present on most surfaces studied by XPS.
6063 Aluminum Alloy by XPS
Authors: Rosenberg R. A. , McDowell M. W.
Published: July 2002

A sample of the extruded 6063 aluminum alloy used for the vacuum chamber of the Advanced Photon Source was analyzed by x-ray photoelectron spectroscopy. The surfaces were prepared by detergent cleaning followed by in situ Ar+ ion bombardment.
2219 Aluminum Alloy by XPS
Authors: Rosenberg R. A. , McDowell M. W.
Published: July 2002

A sample of the 2219 aluminum alloy used for the flange assemblies of the Advanced Photon Source was analyzed by x-ray photoelectron spectroscopy. The surfaces were prepared by detergent cleaning followed by in situ Ar+ bombardment.
High Resolution XPS Study of a Thin Cr2O3(111) Film Grown on Cr(110)
Authors: Hassel M. , Hemmerich I. , Kuhlenbeck H. , Freund H.-J.
Published: July 2002

Transition metal oxides are important materials in heterogenous catalysis, as supporting materials as well as active components. The catalytic activity of Cr2O3 for IE polymerization of olefines or hydrogenation of alkenes is well known and rather high. Therefore, it is important to get information on the surface electronic structure of Cr2O3. Here we report high resolution XPS measurements of a thin epitaxial Cr2O3(111) film grown on Cr(110). The oxide films have been prepared by in situ oxidation of a Cr(110) single crystal disk (12 mm diameter, 1.5 mm thickness, purity 5n) at elevated temperatures (540 K to 780 K) in an atmosphere of 10−6 mbar of O2. The oxygen doses have been typically in the range of a few thousand Langmuirs. Under these conditions a Cr2O3(111) layer [Cr2O3(0001) orientation in hexagonal notation] forms on the surface as confirmed via low energy electron diffraction IV analysis. The film thickness ranges from about 2.5 nm to 8.0 nm under the chosen preparation conditions, allowing electron spectroscopy to be performed without charge compensation. The studies of Cr2O3(111) have been performed as part of a project aimed at investigating idealized catalytic systems under ultrahigh vacuum conditions.
Ru and RuO2 Thin Films by XPS
Authors: Kaga Yukinao , Abe Yoshio , Yanagisawa Hideto , Kawamura Midori , Sasaki Katsutaka
Published: July 2002

Ru and RuO2 thin films are considered to be new electrode materials for dynamic random access memories (DRAMs) and ferroelectric nonvolatile memories because of their low resistivity and good thermal and chemical stabilities. In this study these thin films were pepared by reactively sputtering a Ru metal target (99.9% purity) in an argon and oxygen atmosphere. XPS spectra were collected with a PHI 1600 spectrometer equipped with a monochromatic Al Kα x-ray source and a multichannel detector. This report includes XPS spectra of Ru 3d and O 1s core regions for these samples. The binding energy of Ru 3d5/2 is determined as 280.0 and 280.8 eV for Ru and RuO2 films, respectively. The presence of a small amount of Ru with higher oxidation states, such as Ru6+ and Ru8+, is shown at the surface of the RuO2 thin film.
Growth of diamond films on Ti–6Al–4V substrates and determination of residual stresses using Raman spectroscopy
Authors: Kumar Ashok , Ahmed I. , Vedawyas M.
Published: July 2002

Diamond films were deposited on Ti–6Al–4V substrates using the hot filament chemical vapor deposition method. Improvement in film adhesion was achieved by controlling the methane ratio and surface treatment of the substrate. The quality of film adhesion was established by measuring the residual compressive stress in between the film and substrate. A general model is used for examining the micro-Raman spectrum in order to measure the residual biaxial stress. The as-grown films have shown residual compressive stress from 1.782 to 7.25 GPa, coming very close to the theoretically predicted value.
ZnO:Zn phosphor thin films prepared by ion beam sputtering
Authors: Li W. , Mao D. S. , Zhang F. M. , Wang X. , Liu X. H. , Zou S. C. , Zhu Y. K. , Li Q. , Xu J. F.
Published: July 2002

ZnO:Zn phosphor thin films used in field emission displays were prepared by ion beam sputtering. Postdeposition annealing of these films was performed at temperatures ranged from 100–1000 °C in N2 atmosphere. Several techniques, including Rutherford backscattering spectroscopy (RBS), x-ray diffraction, atomic force microscopy, Hall effect measurement, and photoluminescence spectra, were employed to characterize these films. RBS results showed there was an amount of excess Zn in the films. The as-deposited films were found to contain both amorphous and crystalline phases. The morphology of the films consisted of several structures. It was detected that the free carrier concentration of these films decreased by increasing annealing temperature, indicating the elimination of excess Zn. Meanwhile, the Hall mobility increased quickly if the annealing temperature exceeded 400 °C, showing the improved crystallinity. Two categories of photoluminescent peaks, ultraviolet/violet and blue/green, were detected in ZnO:Zn films. The singly ionized oxygen vacancies were responsible for the visible luminescence which was strongly affected by the annealing processes. The possible reasons may include recovery of structural defects, homogenization of the films, and evaporation of the excess Zn with different contributions at different temperature ranges.
Studies on the interaction between thin film materials and Mo field emitter arrays
Authors: Chalamala Babu R. , Reuss Robert H.
Published: July 2002

A simple method for the evaluation of materials suitable for the fabrication of field emission vacuum microelectronic devices is presented. Since there can be a wide range of electron and ion interactions with the device, it is important to be able to quickly assess if a material may have a particular adverse effect on emission performance under operational conditions. The technique is based on the sensitivity of a large field emitter array to the outgassing or desorption of gas species from thin films under electron beam excitation. We found that Mo field emitter arrays degraded rapidly with stainless steel anodes coated with various oxide materials. The extent of degradation was found to be the most rapid with SiO2, Si3N4, and MoO3 thin films. Stainless steel anodes with Mo and Nb thin films show a faster degradation rate than stainless steel anodes, most likely because of native oxides grown during processing and handling. The emission behavior in the presence of Ir, Pd, Al, Zn, and Ti metal films and barrier materials like C and TaN is similar to stainless steel reference data. We find that once the oxide films are covered with barrier layers like C and TaN, emission decay rates approach the values obtained with stainless steel reference anodes. The observed emission current degradation is consistent with a model based on the liberation of oxygen from the surface of electron beam bombarded materials. Using controlled oxygen exposure experiments, we have determined the equivalent local oxygen pressures in the presence of various thin films. We found that with thin films of Nb, ZrO2, Ta2O5, MgO, Nb2O5, and Al2O3, the emission degradation is akin to having a local O2 partial pressure in the 1×10−7–1×10−6 Torr range and with Mo, MoO3, Si3N4, and SiO2, this is equivalent to having local O2 pressures of 1×10−5 Torr.
Self-Contamination and Environment of an Orbiting Satellite
Authors: Scialdone John J.
Published: July 2002

The flux of molecules emitted by the satellite and subsequently returning to its surface is investigated. The reflection occurs upon collision of these with ambient molecules. The evaluation of this flux is carried out from a knowledge of the outgassing rate of the satellite, its dimensions, and the orbit parameters. Condensation rates and adsorption layers on critical surfaces are calculated from the knowledge of this flux, and from the natures and temperatures of the gas and the surface. The calculation of these parameters, based on estimated and in some cases measured emission rates, has been carried out for a number of satellites. These developed relationships and graphs allow the estimation of several important parameters for an orbiting satellite. This report presents the pressures and densities at various distances from the satellite as produced by the surrounding ambient molecules and by the outgassing of the satellite. The pressure and density produced by the outgassing can be obtained as a function of time if the behavior of the outgassing with time is known.
Direct pattern etching for micromachining applications without the use of a resist mask
Authors: Cho Byeong-Ok , Ryu Jung-Hyun , Hwang Sung-Wook , Lee Gyeo-Re , Moon Sang Heup
Published: July 2002

The method of direct pattern etching without the use of a conventional resist mask has been developed. This method takes advantage of the field-shielding effect of a Faraday cage, inside which the substrate is located. A stainless-steel stencil mask, constituting the upper plane of the cage fixed on a cathode in a plasma etcher, was used as a pattern mask in reactive ion etching. A CF4 plasma at 5 mTorr was used to etch the initially bare substrate of a Si wafer covered with a 1-μm-thick blanket SiO2 film. The mask patterns with the minimal dimension of 40 μm were accurately transferred to the substrate with the etch profiles vertical to the substrate surface. When the gap distance between the stencil mask and the substrate surface was as small as 0.5 mm, the ratio of the etch rate below an opening to that below a blocking portion of the mask was over 5600. On the other hand, the etch rate ratio fell virtually to unity when the substrate was apart from the mask by 10.5 mm. The simulation study of ion trajectories showed that the ion beams were increasingly diverged as ions traveled away from the mask inside the cage. That is, the beams were well separated from each other in close proximity to the stencil mask, resulting in fine pattern etching. At positions sufficiently far from the mask, however, the deviated ion beams extensively overlapped with each other to yield the uniform ion flux.
New combination of four-component gas He–Ne–Xe–Ar for high efficiency plasma display panel
Authors: Min Byoung-Kuk , Choi Hoon-Young , Lee Seok-Hyun , Tae Heung-Sik
Published: July 2002

The improvement of luminous efficiency is one of the most important issues in making a plasma display into a large flat panel device. Accordingly, a new combination of a four-component gas, He–Ne–Xe–Ar, is proposed in order to achieve a high luminous efficiency in color plasma display panels (PDP). The densities of 32 species and electron temperature were calculated using a zero-dimensional simulation. The results were then compared with measurements of brightness and luminous efficiency to identify the optimum mixing condition of He(7): Ne(3)–Xe(4%)–Ar gas for a color PDP. The reaction mechanism was computationally analyzed to comprehend the discharge mechanism in He–Ne–Xe–Ar as well as in He–Ne–Xe. By simulation, the maximum peak point of the Xe*(1S4) state was obtained between a 0.1% and 0.5% Ar mixing ratio and the maximum luminous efficiency was measured with a 0.3% Ar mixing ratio in the PDP. As a result, the luminous efficiency was considerably improved (about 20%) with a 0.3% Ar addition, compared with the conventional He–Ne–4% Xe mixing gas.
Optimizing high-current yields from diamond coated field emitters
Authors: Zhirnov V. V. , Lizzul-Rinne C. , Wojak G. J. , Sanwald R. C. , Cuomo J. J. , Hren J. J.
Published: July 2002

The data for the maximum emission currents from needle-shaped emitters with differing diamond coatings were empirically analyzed. The coatings studied were chemical vapor deposition diamond, natural diamond, and nanodiamond. Two parameters were chosen to characterize the emissive properties: (1) the dependence of the maximum current (Imax) on the coating thickness (D), i.e., I(D)=ΔImax/ΔD, and (2) the dependence of the threshold voltage Vth on [(D);ΔVth/ΔD]. The dependence of Imax(D) and Imax/Vmax(D) were determined from the experimental data for the three different diamond coatings. The maximum current Imax is very different for these three different coatings and is also a function of the coating thickness, D. Both the maximum current and the transconductance of field emission tips can be increased significantly by diamond coatings. A strong, nearly linear, dependence of Imax on diamond thickness was found. An empirical estimate of the thermal conductivity of nanodiamond, based on the field emission data, gave 2.71 W/cm K. The maximum current output from multitip arrays was also analyzed and an optimization procedure was devised that suggested a route to “engineered coatings.”
Modeling of the electron field emission from carbon nanotubes
Authors: Filip V. , Nicolaescu D. , Okuyama F.
Published: July 2002

Using a tunneling approach for the field emission from a single carbon nanotube, expressions for the emission current as a function of the anode voltage and of the emitted electron energy spectrum are obtained. The low dimensionality of the electronic system of a carbon nanotube is taken into account. The extraction field on the nanotube’s tip is evaluated using numerical computations. For nanotubes of practical interest, having large enough diameters, it is demonstrated that the influence of the detailed form of the electron energy dispersion relations is not of major importance. This influence could be generally embedded in a numerical factor entering the expression of the emission current. The influence of the various tube parameters on the characteristics is also identified and analyzed. An approximate formula for use in practical analysis in field emission is deduced and its validity for different nanotube sizes is verified.
Characteristics of fluorinated amorphous carbon films and implementation of 0.15 μm Cu/a-C:F damascene interconnection
Authors: Shieh Jia-Min , Suen Shich-Chang , Tsai Kou-Chiang , Dai Bau-Tong , Wu Yew-Chung , Wu Yu-Hen
Published: July 2002

Fluorinated amorphous carbon films (a-C:F) deposited by plasma enhanced chemical vapor deposition with low dielectric constant (K∼2.3), thermal stability (higher than 400 °C) and acceptable adhesion to a cap layer such as SiOF or SiO2 were obtained by varying the range of content ratios between carbon and fluorine, the rf power, the process pressure and the base temperature. Standard x-ray photoelectron spectroscopy and thermal desorption spectroscopy metrologies were employed to characterize the deposited a-C:F films. The damascene pattern with 0.15 μm and an etching selectivity of more than 50 (a-C:F/SiOF, SiO2) was implemented by a mixture of etching gases of N2+O2. The bias power, rf power and gas flows were incorporated to optimize the etching recipe for achieving a damascene profile with a high aspect ratio. The scanning electron microscope results showed that a better etch profile can be obtained at higher bias power. In our damascene architecture, the etching stop layer or hard mask of both SiOF and SiO2 was studied. The SiOF, providing a lower dielectric constant than SiO2, would especially reduce the entire effective dielectric constant. Furthermore, we integrated electroplated copper into trenches or vias as small as 0.15 μm, with aspect ratio of 6.
Improved performance of nonevaporable getter activated by a continuous wave infrared laser
Authors: Cha S. N. , Choung J. Y. , Song B. G. , Choi J. M. , Han I. T. , Park N. S. , Jung J. E. , Lee N. S. , Kim J. M. , Chee J. K. , Hong J. P.
Published: July 2002

We demonstrate a simple and efficient activation method of nonevaporable getter where a local heating is provided by a laser source. Dependence of various parameters such as laser power, scan speed, and irradiation time by the degree of getter activation was experimentally examined in detail. It is shown that the laser irradiation enhances the getter activation process considerably by shortening the time and increasing the gas absorption capacity required to achieve a desired vacuum level for flat panel display application. The degree of laser activation is compared to that of the conventional thermal heating method. Under the optimized activation conditions, we achieved a vacuum level of 2×10−6 Torr from the initial value of 4×10−4 Torr. Therefore, the laser irradiation method is a very promising technology for nonevaporable getter activation which overcomes a number of problems resulting from the conventional method.
Changes in surface states during epitaxial growth of BaTiO3 on SrTiO3 substrate in connection with composition deviation
Authors: Shimoyama K. , Kubo K. , Iida M. , Yamabe K. , Maeda T.
Published: July 2002

We have investigated the changes caused by composition deviation at growing surfaces during epitaxial growth of BaTiO3 in terms of morphology and oxidation state of cations. Surface morphology was significantly changed by the Ba/Ti ratio. Ba- and Ti-rich surfaces were roughened by three-dimensionally grown islands. An atomically flat surface and well-oxidized cations were obtained at the stoichiometric surface. Surface lattice parameters of the stoichiometric (Ba/Ti=1) sample during epitaxial growth of BaTiO3 on SrTiO3 substrate have been investigated by in situ reflection high-energy electron diffraction (RHEED) observation. We found that the oxygen partial pressure significantly influenced the surface lattice strain relaxation and RHEED oscillation.
Secondary electron emission characteristics for sol–gel based SiO2 thin films
Authors: Jeong Taewon , Lee Jeonghee , Yu SeGi , Jin Sunghwan , Heo Jungna , Yi Whikun , Jeon D. , Kim J. M.
Published: July 2002

We have fabricated six SiO2 thin films by the spin coating of tetraethyl orthosilicate (TEOS) sol–gel solutions of different concentrations. It was found that the thickness of SiO2 film decreased as the concentration of TEOS decreased. Among six samples, 9 nm thick SiO2 film exhibited the highest secondary electron emission (SEE) yield. Moreover, SEE yields for sol–gel based SiO2 films were found to be higher than those for thermal SiO2 films. In order to confirm the applicability of this method, electron-amplifying microchannel plates (MCPs) with a sol–gel based SiO2 layer as an electron emissive layer were fabricated and their amplifying characteristics were investigated. Reasonably good current gains were obtained for those MCPs suggesting that this SiO2 layer formed by the sol–gel method was a good candidate for a SEE layer.
Real-time/in situ diffraction study of phase and microstructural evolution in sputtered β-Ta/Ta2O5 films
Authors: Whitacre J. F. , Yalisove S. M. , Bilello J. C.
Published: July 2002

The evolution of texture, grain size, and phase content in sputtered β-Ta/Ta2O5 films was studied and controlled in situ using a laboratory-based real-time x-ray diffraction system. The films were dc magnetron sputter deposited using sputter gas (Ar) pressures ranging from 2 to 20 mTorr. To collect diffraction data during growth, a grazing incidence x-ray scattering (GIXS) configuration was necessary. Because this configuration complicated the interpretation of texturing data, complete Schultz geometry pole figures were also used to characterize the films after growth, and the relationship between pole figure and GIXS data was examined. The film composition was evaluated using sputter profile x-ray photoelectron spectroscopy and secondary ion mass spectroscopy. It was found that the degree and rate of (002) out-of-plane texturing was systematically stronger in films grown at lower Ar pressures (< 10 mTorr). These films were predominantly β-Ta in composition and had relatively large grains (∼50 nm in diameter). Films grown using progressively higher Ar pressures had increasing amounts of Ta2O5, developed a (002) out-of-plane texture more slowly, and were nanocrystalline/amorphous in nature. Data from depositions where the Ar pressure was changed during growth showed that the deposition environment at the instant of layer formation determined the phase content, degree of texture, and grain size in the developing film; the characteristics of previous layers had little bearing on subsequent growth. This shows that tailored multilayer β-Ta/Ta2O5 films may be created and monitored in situ.
Two-dimensional effects on ultralow energy B implants in Si
Authors: Giannazzo F. , Priolo F. , Raineri V. , Privitera V. , Picariello A. , Battaglia A. , Moffat S.
Published: July 2002

A systematic work has been carried out in order to optimize sample preparation and scanning capacitance microscopy (SCM) on double beveled samples. The method allowed us to enhance depth and lateral resolution and it has been applied to characterize two-dimensional profiles of ultralow energy B implants in Si after diffusion. Implants have been performed into patterned wafers with different stripe widths ranging from 0.5 to 5 μm. B transient enhanced diffusion is strongly reduced with decreasing feature size below about 2 μm. This effect has been related to the high interstitial diffusivity with respect to B. It is even enlarged for lateral diffusion due to the interstitial recombination under the SiO2 mask at the Si/SiO2 interface. The implications for the formation of ultrashallow junctions in device structures are also discussed.
Electron temperatures of inductively coupled Cl2–Ar plasmas
Authors: Fuller N. C. M. , Donnelly Vincent M. , Herman Irving P.
Published: July 2002

Trace rare gases optical emission spectroscopy has been used to measure the electron temperature, Te, in a high-density inductively coupled Cl2–Ar plasma at 18 mTorr as function of the 13.56 MHz radio frequency power and Ar fraction. Only the Kr and Xe emission lines were used to determine Te, because of evidence of radiation trapping when the Ar emission lines were also used for larger Ar fractions. At 600 W (10.6 W cm−2), Te increases from ∼4.0±0.5 eV to ∼6.0±2.0 eV as the Ar fraction increases from 1% to 96%. In the H (inductive, bright) mode, Te, for a “neat” chlorine plasma (including 1% of each He/Ne/Ar/Kr/Xe) increases only slightly from ∼3.8 to 4.0 eV as power increases from 450 to 750 W. This increase is much larger for larger Ar fractions, such as from ∼4.0 to 7.3 eV for 78% Ar. Most of these effects can be understood using the fundamental particle balance equation.
Electrical spin injection into In0.4Ga0.6As/GaAs quantum dots using (Ga,Mn)As
Authors: Ghosh S. , Bhattacharya P.
Published: July 2002

Electrical injection of spin polarized holes from a Ga0.974Mn0.026As layer into In0.4Ga0.6As/GaAs quantum dots is achieved for temperatures up to 40 K. The spin injection efficiency at 4.5 K is ∼26%. The temperature behavior of spin injection agrees with the measured temperature dependence of the magnetization in the (Ga,Mn)As layer. Control samples with Be doped GaAs contact layers do not exhibit similar polarization behavior.
Nanofabrication of photonic crystal membrane lasers
Authors: Cao J. R. , Lee Po-Tsung , Choi Sang-Jun , Shafiiha Roshanak , Choi Seung-June , O’Brien John D. , Dapkus P. Daniel
Published: July 2002

We present techniques for fabricating photonic crystal (PC) membrane defect lasers. These nanostructures operate as optically pumped lasers under pulsed conditions at room temperature. The thin membrane PC defect structures are formed by transferring an electron-beam lithographically defined lattice pattern into an epitaxial layer structure by a sequential process of ion beam etching, reactive ion etching, and electron cyclotron resonance etching steps. A V-shape undercut channel is formed by a wet chemical etching using a 4:1 mixture of HCl and H2O to create the suspended membrane. We include a detailed description of a dependable and repeatable HCl undercut process for the PC structure.
Spatially selective single-grain silicon films induced by hydrogen plasma seeding
Authors: Bo Xiang-Zheng , Yao Nan , Wagner Sigurd , Sturm J. C.
Published: July 2002

The enhancement of a hydrogen plasma treatment on the solid-phase crystallization of hydrogenated amorphous silicon has been applied to form single crystalline silicon islands at designed locations. Holes with diameters from 0.4 to 1.8 μm were opened in silicon nitride, and then amorphous silicon films within the holes were exposed to a hydrogen plasma to create microcrystalline seeds. After furnace annealing, the relationship between the size of holes and number of grains in the holes has been investigated. It is found that a single nucleus cannot be induced until the diameter of holes decreases below 0.6 μm. Further annealing enlarges the grain size by lateral growth but does not increase the number of grains in the hole.
Characterization by medium energy ion scattering of damage and dopant profiles produced by ultrashallow B and As implants into Si at different temperatures
Authors: Van den Berg J. A. , Armour D. G. , Zhang S. , Whelan S. , Ohno H. , Wang T.-S. , Cullis A. G. , Collart E. H. J. , Goldberg R. D. , Bailey P. , Noakes T. C. Q.
Published: July 2002

High depth resolution medium energy ion scattering (MEIS) has been used to examine the influence of dynamic defect annealing on the damage formed in silicon substrates irradiated with ultralow energy ions (1 keV B+, 2.5 keV As+). Samples were implanted to doses ranging from 3×1014 to 2×1016 cm−2 at sample temperatures −150/−120, 25, and 300 °C. For all doses examined, B implantation at 25 and 300 °C produced a near-surface disordered layer 3–4 nm thick. For doses above 1×1015 cm−2, a second, deeper damaged layer was resolved at a depth greater than the peak of the projected range (Rp) of the implanted ions. For irradiations at −150 °C, MEIS and transmission electron microscope studies indicated the formation of a continuous amorphous layer, extending from the deeper damage region to the surface. However, epitaxial regrowth of this layer was not complete after a 30 s anneal at 600 °C, being arrested near Rp by clusters containing B. The dependence of B transient enhanced diffusion on the implant temperature as observed in secondary ion mass spectrometry (SIMS) measurements is discussed in terms of different dynamic annealing conditions and the subsequent availability of interstitials that result from implantation at different temperatures. MEIS studies of the damage formation and rapid thermal annealing due to the heavier As implants, carried out at 2.5 keV to a dose of 1.5×1015 cm−2 at room temperature, confirmed that all the implanted As was trapped up to this dose. Following epitaxial regrowth at 600 °C for 20 s, approximately half of the As was observed to be in substitutional sites, consistent with the reported formation of AsnV clusters (n⩽4), while the remainder had segregated to and become trapped at the oxide interface. The damage produced by the As implant also displayed a strong dependence on the substrate temperature. Irradiation with 2.5 keV ions at −120 and 25 °C resulted in amorphous Si layers. In contrast, the damaged Si remained crystalline below the near-surface damage layer, when irradiated under the same conditions at 300 °C. Notably different As distributions were observed by SIMS in these samples following high temperature (900–1100 °C) annealing. The significant influence of complex defect agglomeration during ion bombardment on the subsequent annealing behavior is discussed.
Molecular-beam epitaxy production of large-diameter metamorphic high electron mobility transistor and heterojunction bipolar transistor wafers
Authors: Baklenov O. , Lubyshev D. , Wu Y. , Fang X.-M. , Fastenau J. M. , Leung L. , Towner F. J. , Cornfeld A. B. , Liu W. K.
Published: July 2002

Manufacturable process for the growth of metamorphic InGaAs/InAlAs/InP heterostructures has been realized on a large-scale production molecular-beam epitaxy reactor capable of growing on multiple 4 in. or 6 in. GaAs wafers. Developed metamorphic buffer technology is based on graded InAlAs layer with In composition changing from <5% up to the desired composition to be used in the device layers. Both metamorphic high electron mobility transistors and heterojunction bipolar transistors (on GaAs substrates) as well as their lattice-matched counterparts (on InP substrates) were grown and characterized. Photoluminescence mapping and multipoint Hall measurements demonstrate excellent cross-wafer uniformity and electronic transport properties. Fabricated large-area devices show no significant difference in current gain or linearity characteristics for the metamorphic structures compared to their lattice-matched counterparts.
Angular Distribution of Flow from Orifices and Tubes at High Knudsen Numbers
Authors: Stickney R. E. , Keating R. F. , Yamamoto S. , Hastings W. J.
Published: July 2002

The flow of cesium vapor from orifices and tubes into vacuum was investigated experimentally. Using a surface ionization gauge, the intensity of the flow field was measured at various angular positions from the center line for Knudsen numbers ranging from approximately 1 to 100. The dependence of the angular distribution and center-line intensity on Knudsen number is reported for cylindrical apertures having length-to-diameter ratios of 0.04, 1.15, 3.03, and 5.63.
Equivalent dc Sputtering Yields of Insulators
Authors: Davidse P. D. , Maissel L. I.
Published: July 2002

Radio-frequency sputtering cannot be used for absolute measurements of sputtering yields because of the spread in energies of the bombarding ions. This paper describes how these yields can be studied by simultaneously sputtering with the insulators other materials with known dc sputtering yields. Silicon and germanium were selected as reference materials. The dielectric materials studied were fused quartz, Pyrex 7740 glass, Pyrex 7059 glass, soda lime glass, and aluminum oxide (Lucalox). The experiments were performed in an Argon atmosphere at 3 × 10−3 Torr and at rf electrode potentials between 1.3 and 3.9 kV peak-to-peak. The frequency in all experiments was 13.56 MHz. Sputtering yields were found to be highest for fused quartz (0.16 to 0.5 molecules/ion) and lowest for aluminum oxide (0.04 to 0.17 molecules/ion). The data for fused quartz were found to fall between published low-energy yields determined by Langmuir probe and very high-energy yields determined by ion beams.
Pressure Conversion Constants for Magnetron Ionization Gauges
Authors: Pelz David , Newton George
Published: July 2002

The gas calibrations of the Explorer 32 satellite atmospheric density experiment provided comparisons of the operation of the following five kinds of ionization gauges: (1) flight type, glass enveloped, cold cathode, magnetron gauge (model NRC-528), (2) flight type, metal enveloped, cold cathode, magnetron gauge (model GCA-R5), (3) commercially available, glass enveloped, “Redhead gauge” (model NRC-552), (4) flight type, metal enveloped, warm cathode, magnetron gauge (WCM), and (5) commercially available, metal enveloped, Penning-type gauge (model GE-22GT210).

The nitrogen pressure responses of these gauges are compared in terms of the conversion constant (C). C is the ratio of the cathode current to the pressure and is related to the number of ions produced per neutral particle in the gauge. The 552 and R5 gauges exhibit values of C which axe maximum between 10−10 and 10−9 Torr and decrease at higher pressures. In contrast to this behavior the 528 and 22GT210 gauges exhibit primarily increasing C values with pressure, and the C values of the warm cathode magnetron are constant at low pressures. Experimental results which can be interpreted in terms of the behavior of the negative space charge in the gauges are briefly discussed. A high sensitivity of the R5 gauge response characteristics to anode voltage is demonstrated in terms of C values, oscillation regions, and discontinuities.
Solid Amorphous Bi, Ga, and Fe as Examples of Liquid-Like Amorphous Substances
Authors: Richter H.
Published: July 2002

Experiments show that two structures simultaneously occur in liquid-like solid amorphous and in molten Bi and Ga, i.e., the spherical close packing in the form of a straight atomic chain and the layer lattice structure. In Bi the layer lattices are derived from the respective lattice and in Ga they are remainders of the lattice. In solid amorphous Fe the spherical close packing shows up as a zigzag chain in the atomic distribution curve as in molten Na. Differing from Bi and Ga, in amorphous Fe the layer lattices are parts of the lattice.
Liquid-phase epitaxial growth of stepwise-graded InAs1−xSbx–InAs heterostructures
Authors: Andrews A. M. , Cheung D. T. , Gertner E. R. , Longo J. T.
Published: July 2002

To alleviate the lattice mismatch for InAs1−xSbx (0<x<0.2) deposited on InAs we have employed a multilayer structure of incrementally increasing compositional steps grown by a steady state liquid-phase epitaxial growth technique. Etch pit densities and surface morphology for various substrate orientations have been studied. The resultant films possess surface cross-hatch patterns with etch pit densities of ?3×104 cm−2 for growth on (100) substrates.
Comparison of Auger signals measured using differential and integral Auger spectra from C and O adsorbed on W
Authors: Ishikawa Kazuo , Tomida Yasushi
Published: July 2002

Comparison was made experimentally with carbon and oxygen atoms on tungsten between the widely used peak-to-peak height measurements in dEN (E)/dE mode spectra, A, and the rarely used Auger peak heights and areas in EN (E) mode spectra, H and S, respectively, as measures of the signal in Auger electron spectroscopy. The proportionality between A and S was found to hold or not depending on whether chemical changes of the elements did not or did occur, respectively. As a quantitative example, carbide was found to have A-values about 3.5 times larger than graphite for the same atomic concentration. For carbon, the H-values gave better indications of concentration than A. An example is presented in which the observation of an A vs S relation provides a means to detect the chemical change of specimens more sensitively than by observing Auger peak shapes.
Polyimide membrane x-ray lithography masks—Fabrication and distortion measurements
Authors: Flanders D. C. , Smith Henry I.
Published: July 2002

A process for fabricating polyimide membrane x-ray lithography masks is described in detail. Thin membranes of polyimide are formed by spinning polyamic acid on Corning 0211, or other glass substrates, and polymerizing in situ. The glass substrate acts as a holder and an efficient heat sink during formation of gold absorber patterns on top of the polyimide, a procedure that usually includes ion beam etching. A support ring is then bonded to the polyimide, and the glass etched in dilute HF. Optically smooth polyimide membranes with thicknesses from 0.5 to 5 μm are readily achieved. Measurements of the distortion of polyimide membrane x-ray lithography masks have been made using a holographic moiré method and a method based on measuring the spread in the angle of diffraction from gold-grating patterns. These indicated a distortion less than two parts in 105 over the central 7.5-mm-diam area of a 19-mm-diam membrane.
Regrowth of amorphous films
Authors: Lau S. S.
Published: July 2002

In this review, we emphasize three aspects of the regrowth of ion-implanted amorphous Si layers: (1) orientation dependence of the regrowth kinetics, (2) impurity effects on the regrowth kinetics, and (3) impurity distribution due to regrowth. To account for the orientation dependence there are at least three proposed models: (1) geometric model, (2) stress relaxant model, and (3) surface reconstruction model. Each of these models is discussed here. For amorphous Ge regrowth, the characteristics are similar to those of Si. Parallels are drawn whenever possible. An example is given to illustrate the use of ion-implanted-regrowth process to modify the crystallinity of thin layers.
An ELS vibrational study of carbon monoxide adsorbed on the Cu(110) surface
Authors: Wendelken J. F. , Úlehla M. V. K.
Published: July 2002

The adsorbate site location for CO on Cu(110) has been investigated with electron energy loss vibrational spectroscopy. With low coverage at 80 K vibrational energies of 85 and 258 meV are observed. At high coverages and/or near the thermal desorption temperature of 170 K, only a single peak at 260 meV is observed. A simple spring model analysis of the vibrational energies indicates that a bridge position is occupied by CO in the first case and the on-top position in the second case although LEED results indicate that CO cannot be highly localized at any one site in the high coverage case.
Photoluminescent properties of GaAs–GaAlAs, GaAs–oxide, and GaAs–ZnS heterojunctions
Authors: Woodall J. M. , Pettit G. D. , Chappell T. , Hovel H. J.
Published: July 2002

The band edge photoluminescence of GaAs structures has been studied as a function of greater than band edge excitation energies. For p–p–n, GaAlAs–GaAs–GaAs, and p–n GaAs solar cell structures, it was found that the photoluminescent response curves were similar to the short circuit current response curves. A computer simulation program was developed to extract information about minority carrier diffusion lengths and surface and interface method for both qualitative and quantitative evaluation of processing and fabrication steps on GaAs based structures. For example, it was found that ZnS–GaAs heterostructures showed an increase in photoluminescent response with annealing time at 500°, and that anodized GaAs showed a higher response than ’’bare’’ GaAs which then decreased after a 450° anneal.
Two-dimensional effects and effective masses of the InAs/GaSb (001) superlattices
Authors: Madhukar A. , Dandekar N. V. , Nucho R. N.
Published: July 2002

The tight binding method is employed to study the two-dimensional aspects of the electronic structure of InAs/GaSb(100) superlattices. Results are presented which show the spatially confined nature of the light hole, heavy hole and conduction bands. The hole states are found to be confined primarily on the GaSb side, whereas the conduction bands are confined to the InAs side. Effective masses in the plane of the superlattice are calculated. The conduction band mass is found to compare well with the appropriate value extracted from recent magnetoresistance measurements. Optical absorption data is used to determine the InAs conduction band to GaSb valence band edge discontinuity at the Γ-point. It is found that the former lies below the latter, qualitatively consistent with the electron affinity rule, but only by ∠ 60 meV. Reduction to this value from the affinity value of ∠ 140 meV is consistent with the affect of charge transfer. Finally, some comments regarding the variation, with thickness, of the relative and absolute positions of energies are made, particularly in light of the prevalent, though often ambiguous, practice of comparing projected regions of bulk energies with finite slab or superlattice band structures.
Measurements of the axial density profiles of sputtered cathode atoms in a dc glow discharge
Authors: Elbern Alwin
Published: July 2002

In a low pressure dc argon–iron glow discharge we measured the axial density distribution of sputtered cathode atoms for different discharge conditions. The density distribution of sputtered Fe was measured in the ground state and in low lying metastable states for the different pressures of the discharge gas. These measurements were done by dye laser fluorescence spectroscopy with space resolution of 1 mm in the axial direction. The results show a density maximum near the cathode which depends strongly on the discharge current as well as on the electronic excitation state of the diffusing atoms. The results have been compared with distributions calculated from existing theoretical treatments.