bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermoeconomic Considerations in the Optimum Allocation of Heat
Transfer Inventory for Refrigeration and Heat Pump Systems
Authors: Antar Mohamed A. , Zubair Syed M.
Published: July 2002

Thermoeconomics is defined as attaching monetary values to heat exchanger conductances of a given plant. In this study, optimum allocation of heat transfer inventory for heat exchangers in a refrigeration system with specified power input or cooling capacity, and for a heat pump with specified heating capacity is investigated. The ratio of hot- to cold-end conductance unit cost ratio, G, was considered in the analysis as an additional parameter of considerable importance to the designer. A closed-form expression is given in terms of unit cost of conductances of both the heat exchangers. The results show a strong dependence of the total cost on the absolute temperature ratios as well as the hot- to the cold-end conductance cost ratio. It is demonstrated in the illustrative example that for G=0.1, the conductance of the hot-end heat exchanger is about three times the cold-end heat exchanger.
A Comparison of Data-Reduction Methods for a Seven-Hole Probe
Authors: Sumner David
Published: July 2002

Two data-reduction methods were compared for the calibration of a seven-hole conical pressure probe in incompressible flow. The polynomial curve-fit method of Gallington and the direct-interpolation method of Zilliac were applied to the same set of calibration data, for a range of calibration grid spacings. The results showed that the choice of data-reduction method and the choice of calibration grid spacing each have an influence on the measurement uncertainty. At high flow angles, greater than 30 deg, where flow may separate from the leeward side of the probe, the direct-interpolation method was preferable. At low flow angles, less than 30 deg, where flow remains attached about the probe, neither data-reduction method had any advantage. For both methods, a calibration grid with a maximum interval of 10 deg was recommended. The Reynolds-number sensitivity of the probe began at Re=5000, based on probe diameter, and was independent of the data-reduction method or calibration grid spacing.
On the Reverse of One Property of Involute Gears
Authors: Fayet Michel
Published: July 2002

The author deals with the property of involute gears according to which the velocity ratio is constant for any distance between axes. It is known that the involute is the only shape which has this property, but it is not well known in a detailed way, and the only complete demonstration dates from Bricard. For this reason the present paper has an historical interest and, on the other hand, it proposes a new proof better understandable nowadays for it is based on Euler-Savary properties only.
Measurement of Dynamic Warpage During Thermal Cycling of Dielectric Coated SS Substrates for Large Area MCM-D Packaging
Authors: Dang Anh X. H. , Ume I. Charles , Bhattacharya Swapan K.
Published: July 2002

Potential application of stainless steel (SS) as a base substrate material for a large area MCM-D packaging is reported in this paper. A test vehicle was fabricated using 0.008 in. thick and 12 in.×12 in. SS panel with laser drilled 0.01 in. vias. A dielectric material (Parylene N) was deposited on the SS panel and around the inside via walls in order to electrically isolate the via filling material from the body of the SS substrate and also making the SS surface non-conductive. Vias were filled using a commercially available conductive via-plug material. The test structure was exposed to elevated temperatures to simulate the thermal excursion the substrate would be subjected to during the MCM-D thin film process. The end objective of this work is to be able to fabricate large area (24 in.×24 in.) SS substrates for next generation MCM-D packaging with reduced warpage. This paper reports results of the dynamic warpage measurement during thermal cycling of a 12 in.×12 in. Parylene N coated SS substrate. [S1043-7398(00)00602-2]
Estimation of Local Thermophysical Properties of a One-Dimensional
Periodic Heterogeneous Medium by Infrared Image Processing and Volume Averaging
Method
Authors: Varenne M. , Batsale J.-C. , Gobbé C.
Published: July 2002

The estimation of local thermophysical properties can be of paramount importance in the study of heterogeneous media. The volume averaging method, here reduced to a one-dimensional line averaging, is used to implement an estimation method of local thermal resistivity field, for a stratified medium. The method is tested with experimental transient temperature fields obtained with a calibrated stratified sample by an infrared camera. A large number of images are processed at the transient state. The same intrinsic stationary field is estimated from each image. By repeated estimations, this method reduces the measurement noise influence. [S0022-1481(00)01701-1]
Key Issues Associated With Development of Reassessment and
Requalification Criteria for Platforms in the Bay of Campeche, Mexico
Authors: Bea R. G. , Valle O.
Published: July 2002

Petroleos Mexicano (PEMEX) and Instituto Mexicano del Petroleo (IMP) have developed and issued Transitory Criteria for reassessment and requalification of platforms and pipelines in the Bay of Campeche (1998). The purpose of this paper is to highlight some of the key issues that were associated with development of the PEMEX-IMP guidelines and to identify some of the future efforts that are intended to extend the technology of platform reassessment and requalifications. It is hoped that the open exchange and discussion of this experience will help promote worldwide cooperation and development of this important technology. [S0892-7219(00)00801-3]
Developments of Subsea Pipeline Technology for Norwegian Waters
Authors: Lund Sverre
Published: July 2002

Norwegian waters have been a main arena for development of subsea pipeline technology over the last 25 yr. The gas transportation systems from Norway to continental Europe comprise the largest and longest subsea pipelines in the world. The challenges of pipeline projects in and from Norwegian waters include large water depths, large diameters, long distances, uneven seabed, rocky landfalls, and hostile environmental conditions, all within strict requirements for safety, regularity, cost efficiency, and environmental impact. This paper provides an overview of the technology developments performed in this period, initially focusing on ability to cross the deep waters of the Norwegian trench by large-diameter pipelines, then on subsea design aspects such as stability, free span design, and mapping technology, and in recent years also on improvements in transportation efficiency, cost reductions, and operational issues. The paper is based on a Plenary Lecture presented at the 1998 OMAE Conference in Lisbon, Portugal. [S0892-7219(00)00601-4]
Finite Element Analysis of Thermoelastic Instability With Intermittent Contact
Authors: Geijselaers Hubert J. M. , Koning Annette J. E.
Published: July 2002

The equations that describe the development of corrugations on block braked wheel treads caused by thermoelastic instability are discretized using the finite element method. The perturbations of temperatures and distortions are described by an amplitude function, which is spatially fixed multiplied by a sinusoidal running wave term of fixed wavelength. The governing equations are such that the wave term cancels out. Only the amplitude functions are discretized in the finite element model. The intermittent nature of the contact is directly specified through the boundary conditions. Results are obtained for a simplified two-dimensional model of a train wheel. These results agree with analytical results. [S0742-4787(00)00701-3]
Influence of Internal Flow on Film Cooling Effectiveness
Authors: Wilfert Gu¨nter , Wolff Stefan
Published: July 2002

Film cooling experiments were conducted to investigate the effects of internal flow conditions and plenum geometry on the film cooling effectiveness. The film cooling measurements show a strong influence of the coolant inlet conditions on film cooling performance. The present experiments were carried out on a flat plate with a row of cylindrical holes oriented at 30 deg with respect to a constant-velocity external flow, systematically varying the plenum geometry and blowing rates 0.5⩽M⩽1.25. Adiabatic film cooling measurements using the multiple narrow-banded thermochromic liquid crystal technique (TLC) were carried out, simulating a flow parallel to the mainstream flow with and without crossflow at the coolant hole entry compared with a standard plenum configuration. An impingement in front of the cooling hole entry with and without crossflow was also investigated. For all parallel flow configurations, ribs were installed at the top and bottom coolant channel wall. As the hole length-to-diameter ratio has an influence on the film cooling effectiveness, the wall thickness has also been varied. In order to optimize the benefit of the geometry effects with ribs, a vortex generator was designed and tested. Results from these experiments show in a region 5⩽X/D⩽80 downstream of the coolant injection location differences in adiabatic film cooling effectiveness between +5 percent and +65 percent compared with a standard plenum configuration. [S0889-504X(00)01102-8]
Editorial
Authors: Zamrik Sam Y.
Published: July 2002

[S0094-9930(00)00803-9]
Robust Active Vibration Control of a Bandsaw Blade
Authors: Damaren Christopher J. , Le-Ngoc Lan
Published: July 2002

An analytical study of a vibrating bandsaw blade is presented. The blade is modeled as a plate translating over simply-supporting guides. Gyroscopic effects due to the blade’s axial motion as well as in-plane forces resulting from tensioning and the influence of the cutting force are included in the model. The latter is modeled as a nonconservative follower force on the cutting edge of the blade and shown to be destabilizing. A state-space model is developed which includes the effects of time-varying cutting forces and exogenous disturbances. Feedback control via a collocated force actuator/rate sensor is introduced and recent advances in robust control theory are used develop controllers which achieve robust stability and performance with respect to the time-varying model. [S0739-3717(00)01101-6]
Characterization of W84.9Ni9.5Fe5.6 Superalloy by XPS
Authors: Mansour Azzam N. , Vasanth K. L.
Published: July 2002

X-ray photoemission spectra of the core and valence levels for crystalline W–Ni–Fe superalloy are presented. Tungsten alloys are referred to as “superalloys” because of their high density and strength and are important engineering materials for numerous military and industrial applications [see D. J. Jones and P. Munnery, Powder Metall. 10, 156 (1967)]. These alloys are prepared by liquid phase sintering [see P. N. Jones, Proceedings of the Second International Tungsten Symposium, San Francisco, CA, 1982 (unpublished), pp. 81–90] resulting in tungsten particles being cemented together by a solid solution of W–Ni–Fe with W being present in small quantities in the solid solution. The bulk composition of 84.9 W, 9.5 Ni, and 5.6 Fe at. % or 98.4 W, 3.4 Ni, and 1.9 Fe wt % [see K. L. Vasanth and C. M. Dacres, Proceedings of the 1987 Tri-Service Conference on Corrosion, WP AFB, OH, 1987 (unpublished), AFWAL-TR-87-4139, Vol. II, p. 165] was determined by EDAX analysis in a scanning electron microscope. XPS low resolution survey scan and higher resolution scans of the C 1s, O 1s, Si 2p, Fe 2p, Ni 2p, Ni L3VV, W 4f, and valence band region were collected on a Perkin Elmer/Physical Electronics model # 5400 spectrometer using nonmonochromated Mg x rays. Analysis of XPS data reveals the following chemistries in the near surface region: (i) Fe is present in the form of Fe3O4, a highly oxygen deficient form of Fe2O3, and/or Fe2O3, (ii) Ni is mainly present as in Ni(OH)2, and (iii) the W metallic particles are covered with thin native oxide films of both WO2 and WO3. The excellent corrosion resistance of both nickel and tungsten metals is due, respectively, to the presence of Ni(OH)2 and WO2 and WO3 coatings on their surfaces.
Characterization of KNiIO6 by XPS
Authors: Mansour A. N. , Melendres C. A.
Published: July 2002

We report x-ray photoemission spectra (XPS) of potassium nickel (IV) hexaoxidoiodate (VII). XPS spectra were measured with the Physical Electronics Model 5400 x-ray photoelectron spectrometer using unmonochromated Mg Kα x rays at two pass energy settings corresponding to analyzer energy resolutions of 1.34 and 0.54 eV. We present the survey spectrum (binding energy range of 0–1100 eV) measured at an analyzer energy resolution of 1.34 eV. Multiplexes of the C, O, K, Ni, and I photoemission lines, valence band region, as well as the Ni LVV and I MN4,5N4,5 Auger lines were measured at an analyzer energy resolution of 0.54 eV.
Vacuum Cleaved Calcium Carbonate by XPS
Authors: Engelhard Mark , Baer Don
Published: July 2002

Calcite is a common mineral phase found in pure and mixed phase systems. The data reported here was collected for comparison with data collected on other systems and to determine the relative sensitivity for various Ca photopeaks that we were using for the analysis of other Ca-containing mineral phases. This data was collected on a PHI Quantum Scanning ESCA Microprobe. This instrument is unique in that the x-ray beam is focused and can be scanned over the sample. A single crystal of calcite was broken in vacuum (exposing the 101¯4 cleavage plane) and analyzed using monochromatic Al Kα x-rays. The sample was neutralized using both low energy ions and electrons.
Etching chemistry of benzocyclobutene (BCB) low-kdielectric films in F2+O2 and Cl2+O2 high density plasmas
Authors: Vitale Steven A. , Chae Heeyeop , Sawin Herbert H.
Published: July 2002

The etching chemistry of benzocyclobutene (BCB) low-k dielectric films was studied in a high density plasma etcher using F2+O2 and Cl2+O2 plasmas. The etching rate in F2+O2 plasmas exceeded 1.2 μm/min with selectivity over oxide and nitride of 16 and 32, respectively. The etching rate in Cl2+O2 plasmas exceeded 0.6 μm/min with selectivity over oxide and nitride of 40 and 80, respectively. BCB films do not etch in pure Cl2 or pure O2 plasmas without ion bombardment, but etching rates of 1000 Å/min were observed using F2 plasmas without ion bombardment. The ion flux in F2+O2 plasmas is primarily O2+ and O+, whereas in Cl2+O2 the dominant ion is ClO+. BCB etching yields in F2+O2 plasmas were measured with a plasma beam/quartz crystal microbalance system. The etching yields suggest that the neutral fluxes and surface chemistry control the etching rates under these conditions, not the ion flux. Using x-ray photoelectron spectroscopy, it was determined that oxygen plasmas preferentially remove the carbon content of BCB, leaving behind a silicon oxide surface. Chlorine plasmas preferentially remove the silicon, leaving behind a carbon surface. F2+O2 plasmas etch BCB through a fluorocarbon film layer, the thickness of which increases with increasing fluorine concentration in the plasma.
Prospect for high brightness III–nitride electron emitter
Authors: Machuca Francisco , Sun Y. , Liu Z. , Ioakeimidi K. , Pianetta P. , Pease R. F. W.
Published: July 2002

We describe p-type gallium nitride (GaN) as a candidate for high brightness photocathodes. Experiments utilizing photoemission spectroscopy and quantum yield measurements were performed on GaN films to characterize various cesium and oxygen activations. Quantum efficiencies of 0.1%–4% were obtained in reflection for the cesiated p-type 0.5 μm thick GaN films and 25%–50% on the 0.1 μm thick GaN films. The corresponding emission currents are 142–300 nA for 0.5 μm thick films and 0.7–1.3 μA for the 0.1 μm thick films. This results in an increase of several orders of magnitude in the emission current from the starting GaN films. Furthermore, an initial desorption measurement was performed in order to evaluate the Cs binding strength to GaN relative to GaAs. We observe Cs was bound to the GaN surface (0001_) at 700 °C and completely desorbed at 450 °C for a (100) GaAs surface. Finally, an alternate barium activation on GaN is included for preliminary comparison with the various cesium activations.
Sidewall-angle effect on the bottom etch profile in SiO2 etching using a CF4 plasma
Authors: Lee Gyeo-Re , Cho Byeong-Ok , Hwang Sung-Wook , Moon Sang Heup
Published: July 2002

The dependence of the bottom etch profile on the sidewall angle in the CF4 plasma etching of an SiO2 film was investigated using a Faraday cage, which allowed ions to impinge on the sidewall at specified angles. The bottom etch profile obtained at −500 V was not affected by the sidewall when the angle between the sidewall and the bottom surface was 45° but showed microtrenching when the angle was greater than 60°. The microtrench depth increased until the angle reached 80°, beyond which the local etch rate was drastically reduced to allow the corner rounding of the bottom profile. As the sidewall angle increases, the etch rate of the bottom surface near the corner is controlled by two opposing factors. The decreasing number of incident ions on the sidewall surface and the increasing shadowing of the bottom surface from ions and neutrals by the sidewall contribute to the reduced etch rate, whereas the increasing kinetic energy and the narrower ion-angular distribution of the ions reflected from the sidewall contribute to the enhancement of the etch rate. In addition to these factors, the enhanced roughness of the sidewall surface due to the fluorocarbon film deposition plays the critical role of suppressing the microtrench formation. Microtrenching was not observed when the sidewall surface was covered with rough fluorocarbon film but was observed when the surface was smooth due to the energy transferred by ions higher than the threshold energy for the fluorocarbon film sputtering.
Efficient and ballistic cold electron emission from porous polycrystalline silicon diodes with a porosity multilayer structure
Authors: Sheng Xia , Kojima Akira , Komoda Takuya , Koshida Nobuyoshi
Published: July 2002

Based on the previous investigations of the cold electron emission from porous silicon and porous polycrystalline silicon (PPS) diodes, we have fabricated PPS diodes with a porosity multilayer structure and evaluated the emission characteristics. The multilayer structure has functions of reforming the electric field distribution and improving the thermal conductivity of the PPS layer. It is demonstrated here that the multilayered sample exhibits high emission current density of ∼0.8 mA/cm2 and high efficiency of ∼1%, which are close to values required for practical use. The emission is quite stable even with a high emission current density. Ballistic electron emission mechanism is discussed in relation to the energy distribution of emitted electrons.
Observation of the bone matrix structure of intact and regenerative zones of tibias by atomic force microscopy
Authors: Baranauskas Vitor , Garavello-Freitas I. , Jingguo Z. , Cruz-Höfling M. A.
Published: July 2002

Atomic force microscopy (AFM) was used to comparatively study the structure of the bone matrix of rat tibia from an intact region with that from regions submitted to surgical injury. We used young male adult rats (Wistar), with corporal masses between 250 and 300 g. Each injury was provoked by drilling a 1.5-mm-diam hole in one cortical tibia surface. The healing course was monitored at 8 and 15 days after the injury. Atomic force microscopy images, at different magnifications, allowed the identification of the time dependence of the osteoblast activity, measured by the increase in the area of neoformed primary bone and in the organization of the collagen fibers of the bone matrix. Characterization of the natural recovery of the damaged bone tissue by AFM is potentially of great importance because it allows the comparison of natural recovery processes with those induced by medicines and other therapeutic procedures.
Multilayer coating and test of the optics for two new 10× Microstepper extreme-ultraviolet lithography cameras
Authors: Montcalm Claude , Spiller Eberhard , Weber Frank J. , Wedowski Marco , Folta James A. , Gullikson Eric M.
Published: July 2002

Two new sets of projection and condenser optics for our prototype 10× reduction extremeultraviolet lithography (EUVL) system were coated with Mo/Si multilayers. The coating thickness was graded across the optics by using shadow masks to ensure maximum throughput at all incidence angles in the camera. The overall deviation of the (normalized) wavelength response across the clear aperture of each mirror is negligible, i.e., below 0.005% root mean square for each optic. However, the wavelength mismatch between two optics coated in different runs is up to 0.07 nm. Nevertheless, this is still within the allowed tolerances, and the predicted optical throughput loss in the camera due to such wavelength mismatch is about 4%. EUV reflectances of 63% and 65% were measured around 13.40 nm for the two secondary optics, which is in good agreement with the expected reflectance based on the substrate finish as measured with atomic force microscopy.
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u slow extension rate fracture stage for Auger electron spectroscopy
Authors: Was G. S. , Tischner H. H. , Martin J. R.
Published: July 2002

A fracture stage is designed to permit slow strain-rate tensile fracture of metallic samples inside the Auger vacuum chamber. The fracture stage consists of two crossheads, one fixed and one moveable. A small electric motor drives the moveable crosshead to separate from the fixed crosshead at a constant rate down to 7×10−4 cm/s. Samples remain attached to the sample carousel stage during loading and following fracture, they can be quickly translated and rotated into alignment with the Auger analyzer. Tests on hydrogen charged Inconel 600 result in fracture times of 2–3 min and fracture strains of 4%–6% yielding a fracture surface that is in excess of 75% intergranular. This technique is recommended for grain boundary analysis of ductile austenitic alloys.
Magnetically confined sputter source with high ion flux
Authors: Window B. , Sharples F. , Savvides N.
Published: July 2002

A magnetically confined deposition source based on the Penning geometry is described. The discharge characteristics for various gas pressures and magnetic fields resemble those of conventional magnetrons, and it is shown using probes that the ion flux approaches the deposition flux at typical target-to-substrate distances. The ion flux can be varied by changing the magnetic field, and the ion energy by biasing the substrates. The system has been used to deposit TiN by sputtering Ti in a reactive Ar–N2 gas mixture. Results are reported for the properties of the films (resistance, hardness, structure) for various substrate temperatures and ion bombardments and demonstrate the usefulness of this source for hard tool coating. The source is readily scaled to production applications.
Influence of preadsorbed oxygen on the sign and magnitude of the chemisorption-induced resistance change for H2 adsorption onto Fe films
Authors: Shanabarger M. R.
Published: July 2002

Measurements have been made of the chemisorption-induced resistance change for H2 adsorbed onto Fe film substrates predosed with fixed coverages of chemisorbed oxygen. The measurements were made at temperatures from 295 to 340 K and for estimated oxygen coverages of less than 0.1 monolayers. Two distinct resistance change components were observed in both the adsorption kinetics and the equilibrium isotherms: a positive component which is associated with the adsorption of H2 onto a clean Fe surface, and a negative component which was correlated with the presence of the chemisorbed oxygen. The resistance change isotherms can be fit with a model which assumes that each of the resistance change components result from dissociative chemisorbed hydrogen. Possible mechanisms for the chemisorbed-oxygen-induced negative resistance change are discussed.
Effect of grain size on the oxidation kinetics of sputtered titanium nitride films
Authors: Thorpe T. P. , Morrish A. A. , Qadri S. B.
Published: July 2002

The oxidation kinetics of sputtered titanium nitride films has been studied as a function of as-deposited grain size. Films of varying grain size have been heated in air at 200 and 300 °C for 24-h time periods. Resulting oxide layers have been measured by Auger depth profiling, and the rate of oxidation related to average grain diameter. Single-crystal films grown on MgO have also been oxidized to provide a comparative end point. Grain diameters have been determined from measurement of the breadth of observed x-ray diffraction peaks, with calculated diameters ranging from 133 to 545 Å. A strong dependence of oxidation rate on as-deposited grain size is observed.
Secondary ion mass spectrometry depth profile of CaF2/Si(100)
Authors: Hopkins L. C. , Cerullo M.
Published: July 2002

Secondary ion mass spectrometry (SIMS) has been used to investigate the depth profiles of calcium (Ca) and fluorine (F) in CaF2 grown on Si(100) by molecular-beam epitaxy. SIMS depth profiles are used to study the effects of in situ rapid thermal annealing on CaF2/Si(100). Finally, the appropriate conditions needed to perform a SIMS analysis for CaF2/Si(100) have been characterized.
Stimulated emission from a Hg1−xCdxTe epilayer and CdTe/Hg1−xCdxTe heterostructures grown by molecular beam epitaxy
Authors: Mahavadi K. K. , Sivananthan S. , Lange M. D. , Chu X. , Bleuse J. , Faurie J. P.
Published: July 2002

We present the results of stimulated emission experiments performed on a Hg0.54Cd0.46Te epilayer, a CdTe/Hg0.48Cd52Te/CdTe double heterostructure, and a CdTe/Hg0.45Cd0.55Te/ Hg0.67Cd0.33Te multiquantum well separate confinement heterostructure grown by molecular beam epitaxy. The epilayer and the double heterostructure were found to lase continuously up to 40 K. Pulsed stimulated emission was observed from the multiquantum well separate confinement heterostructure up to 77 K.
Experiments on helicon plasma sources
Authors: Chen Francis F.
Published: July 2002

This work concerns a search for novel plasma generators with applications to materials processing and advanced accelerators and radiation sources. Experimental measurements, together with a summary of the theory, are presented on the production of high-density plasmas using radio-frequency (rf) excitation of helicon waves. Plasma densities above 3 × 1013 cm−3 have been achieved with 2 kW of rf power. The required power agrees with classical diffusion theory. The scaling of density with magnetic field agrees with the theory of helicon waves. The effect of different antenna designs is demonstrated. Unexpected observations include: (a) a density maximum occurring at very low magnetic fields, (b) an increase in peak density with nonuniform fields, and (c) the strong effects of dc wall potentials on the behavior of the discharge. Tentative explanations of these phenomena are presented.
Particle growth of palladium on epitaxial tin oxide thin films
Authors: Poirier G. E. , Cavicchi R. E. , Semancik S.
Published: July 2002

Thin films of SnO2 were deposited on r-axis Al2O3 and characterized using scanning tunneling microscopy (STM), low energy electron diffraction, and x-ray photoelectron spectroscopy (XPS). The films grew in an epitaxial, layer-by-layer mode. A small miscut of the Al2O3 substrate (0.2°) resulted in parallel, uniformly-spaced, monatomic steps on the SnO2 film surface. Pd was deposited on the SnO2 films and characterized by STM and XPS. Below 2 monolayers, the Pd formed 10–20 nm islands with an apparent height of 0.5 nm. Increasing the Pd coverage eventually results in a continuous metal film that retains the granular surface topography of the isolated particle film. Annealing the films created a population of reduced metallic Sn that we attribute to Sn–Pd alloying but no significant change in the palladium particle morphology was observed.
Investigation of the growth and structure of aluminum overlayers on TiO2 (100) by scanning tunneling microscopy
Authors: Carroll D. L. , Liang Y. , Bonnell D. A.
Published: July 2002

The deposition of ultra thin films of Al on TiO2 (100) rutile has been studied in UHV using scanning tunneling microscopy. Annealing of the (100) surface to temperatures around 1000 °C produces a stable, microfaceted morphology with the facets oriented along the c axis. Aluminum deposited at room temperature appears to grow in islands, in contrast to observations on (110). Tunneling spectroscopy indicates the nature of the deposited material to be metallic. After annealing, the submonolayer Al film interacts with the surface of the TiO2 by reconstruction. This may indicate a thermodynamic energy barrier to the incorporation of the Al into the cation terminated (100) surface.
Fabrication and measurement of one-dimensional arrays of small capacitance Josephson junctions
Authors: Haviland D. B. , Persson S. H. M. , Delsing P. , Chen C. D.
Published: July 2002

We describe the fabrication and measurement of one-dimensional series arrays of small capacitance Josephson junctions and superconducting quantum interference devices. These arrays exhibit a Coulomb blockade of Cooper pair tunneling when the Josephson coupling energy is the order of the charging energy. The effectiveness of a resistive coaxial cable (ThermocoaxTM made by Philips) for attenuation of high frequency electromagnetic noise is demonstrated. This noise influences the measured dc current–voltage characteristic of the array, having qualitatively the same effect as raising the temperature.
Formation of nanoscale cobalt silicide and gold wires using electron beam and chemically enhanced vapor etching
Authors: Allgair J. , Rack M. J. , Whidden T. K. , Kozicki M. N. , Ferry D. K.
Published: July 2002

We report on the successful use of electron-beam patterning of ambient hydrocarbon residues on silicon dioxide as a patterning tool for the formation of nanoscale conductors. This chemically enhanced vapor etching (CEVE) was employed for the production of lithographic masks for the formation of nanoscale wires on the silicon substrates. Cobalt silicide nanowires were formed by using the CEVE-produced mask in combination with conventional metallization and silicidation procedures. Cobalt silicide wires ranging in width from less than 50 up to 125 nm were produced in this study. Nanoscale wires of chromium/gold were also produced using a variation on the procedure employed in the cobalt silicide process. Using identical approaches to mask production and employing a liftoff of the oxide mask by HF solution etching, chromium/gold wires as narrow as 26 nm were produced.
Novel scheme to fabricate SiGe nanowires using pulsed ultraviolet laser induced epitaxy
Authors: Deng C. , Sigmon T. W. , Giust G. K. , Wu J. C. , Wybourne M. N.
Published: July 2002

A novel scheme is employed to fabricate SiGe nanowires in a Si(100) substrate using pulsed ultraviolet (UV) laser induced epitaxy. In particular, Si(100) substrates are patterned with arrays of Ge wires ∼60 nm in width and ∼6 nm in thickness. A thin film low temperature silicon oxide is then deposited on the substrate. SiGe nanowires with a cross section of ∼25×95 nm2 are formed using pulsed UV laser induced epitaxy. The structures are analyzed using scanning electron microscopy and cross-sectional transmission electron microscopy. Potential applications of the wire structure include base formation in a lateral SiGe heterojunction bipolar transistor and direct formation of SiGe/Si quantum wire structures in a silicon chip.
Investigation of multipolar electron cyclotron resonance plasma source sensors and models for plasma control
Authors: Mak P. , Tsai M.-H. , Natarajan J. , Wright B. L. , Grotjohn T. A. , Salam F. M. A. , Siegel M. , Asmussen J.
Published: July 2002

The sensors and models needed for the control of a high-density, multipolar, electron cyclotron resonance (ECR) plasma source have been studied for an argon soft-sputter clean process for semiconductor wafers. The ECR plasma source studied had a discharge diameter of 12.5 cm, a processing chamber diameter of 40 cm, and an excitation frequency of 2.45 GHz. The implementation of control on this plasma machine has been investigated by characterizing the machine using plasma diagnostic measurements, by implementing and testing sensors, and by developing both analytical and statistical models of the machine operation. The real-time usage of sensor data together with input parameter adjustments has been used to obtain predictable soft-sputter/etch rates in the process.
Numerical ellipsometry: Real-time solutions using mapping onto the complex index plane
Authors: Barton D. , Comfort J. C. , Urban F. K.
Published: July 2002

While in situ ellipsometry measurements can be made on growing films, real-time solutions for thickness and optical properties remain challenging. Numerical techniques are necessary because for practical material systems, the equations are not generally invertible. In the absorbing film on a known substrate problem, the typical real number unknowns (film n1, k1, and d) outnumber the real parameters (Ψ and Δ) obtained in a single measurement. Although it is known that two intersecting sets of n1, k1, and d values are established from two measurements, in the past these sets have not been well understood. The work here is a thorough investigation of such curves and explores all theoretically possible intersections for metals depositing onto an oxide substrate. Mathematical and material considerations identify the solution intersection in a few milliseconds for real-time monitoring and control.
Endpoint prediction for polysilicon plasma etch via optical emission interferometry
Authors: Wong K. , Boning D. S. , Sawin H. H. , Butler S. W. , Sachs E. M.
Published: July 2002

In semiconductor manufacturing, the completion or “endpoint” of a plasma etch is typically controlled as a timed process, or monitored by use of optical emission spectroscopy. As etch process requirements and complexity increase (sequences of discrete recipe changes during the etch), consistency in timing changes is becoming an important issue. Newly developed full wafer interferometry sensors enable real-time monitoring of the entire wafer surface during an etch. In this article, endpoint prediction (or film thickness estimation) for etching polysilicon is considered. For the etch of a specific film structure, the interferometric signal is cyclical with a known number of cycles. Similar to the phase angle of a cosine function, data points of an interferometric curve can be associated with a linear phase function. If the phase at endpoint is known, in situ film thickness can be obtained by determining the phase of the incoming signal in real-time. Simulations show that the proposed film thickness estimation algorithm has good accuracy in the face of etch rate drift and variation in film structure. We also find that estimation is more robust if shorter wavelength signals are used. Finally, experimental data verifies that remaining film thickness can be estimated within reasonable accuracy, and endpoint effectively predicted for blanket and patterned films. These methods provide the critical information needed to make control decisions (e.g., when to switch to a more selective chemistry) based on reaching a desired known film thickness.
Growth mechanism and structural studies of sputtered PbTiO3 thin films
Authors: Wasa Kiyotaka , Haneda Yoko , Satoh Toshifumi , Adachi Hideaki , Setsune Kentaro
Published: July 2002

The surface of sputtered PbTiO3 thin films, 5–200 nm in thickness, epitaxially grown on miscut (001) SrTiO3 substrates with miscut angle of 1.7° comprised a periodic striped pattern which was reflected in the initial surface structure of the substrates. The electron microscopic analysis suggests that the film growth is governed by a step-flow model which corresponds to Frank–van der Merwe mode. The surface was extremely smooth with surface roughness less than 3 nm for a film thickness of 200 nm. The sputtered films showed a homogeneous microstructure with three-dimensional epitaxy. The deposition on miscut substrates realizes the growth of perfect single crystal perovskite thin films, having full in-plane alignment together with a continuous film through a large area.
Role of steady state fluorocarbon films in the etching of silicon dioxide using CHF3 in an inductively coupled plasma reactor
Authors: Rueger N. R. , Beulens J. J. , Schaepkens M. , Doemling M. F. , Mirza J. M. , Standaert T. E. F. M. , Oehrlein G. S.
Published: July 2002

It has been found that in the etching of SiO2 using CHF3 in an inductively coupled plasma reactor of the planarized coil design, a thin steady state fluorocarbon film can play an important role in determining the rate of etching. This etching is encountered as the amount of bias power used in the SiO2 etching process is increased, and a transition from fluorocarbon film growth on the SiO2 to an oxide etching rate which is consistent with reactive sputtering theory is made. The observed presence of an intermediate region where etching occurs, although a steady state fluorocarbon film suppresses the etch rate from that expected for a reactive sputtering process, has been referred to as the fluorocarbon suppression regime. This work demonstrates the role of the steady state fluorocarbon film present on silicon dioxide during etching within the fluorocarbon suppression regime. X-ray photoelectron spectroscopy studies of the surfaces of partially etched SiO2 have shown a thinning of this film with increasing rf bias power, as well as a decrease in the fluorine content of the surface film as a function of increasing rf bias power. We have found that slight variations in the film thickness, on the order of 1 nm, can result in large variations, approximately 400 nm/min, in the silicon dioxide etch rate. The presence of the film within the suppression regime appears to be due to the overwhelming polymerization ability of high density plasmas, coupled with the inability of the oxide to react sufficiently with the total fluorocarbon particle flux in order to completely remove this film. For this reason these types of reactors exhibit a regime where oxide etching occurs in the presence of a surface film. The film appears to be directly responsible for the observed suppression of the oxide etch rate from that expected for a reactive sputtering process by dissipating the bombarding ion energy, and thereby suppressing the energy flux arriving at the oxide surface.
Dry etching of InGaP in magnetron enhanced BCl3 plasmas
Authors: McLane G. F. , Wood M. C. , Eckart D. W. , Lee J. W. , Lee K. N. , Pearton S. J. , Abernathy C. R.
Published: July 2002

Magnetron enhanced reactive ion etching of In0.5Ga0.5P was investigated in BCl3 plasmas. Etch rates were determined as a function of cathode power (0.2–0.5 W/cm2), BCl3 flow rate (3–12 sccm), and pressure (2–10 mTorr), with rates as high as 0.35 μm/min achieved. The addition of N2, O2, and Ar to BCl3 was ineffective in producing an etch rate increase. Changes in sheet resistance and photoluminescence of n- and p-type InGaP exposed to BCl3 plasmas were also investigated as a function of power, pressure, and etch duration. The n-type material was more susceptible to etch-induced damage than p-type material, suggesting that electron traps are produced by ion bombardment. Scanning electron micrographs showed etched surfaces to be smooth, with vertical sidewalls free of undercut.
Diagnosing SiO2 contact etch stop with optical emission
Authors: McNevin S. C. , Cerullo M.
Published: July 2002

The variation over time of the etch rates in <0.5 μm diameter contacts is a serious manufacturing concern. This etching variation originates in a deposition variation resulting from changes in the chamber’s temperature and carbon species coverage. This article reports on a real time optical emission method for monitoring this varying deposition, which is directly related to the contact etch rate. Etch rate variation has been deliberately induced by varying the amount of the oxygen postetch treatment. With insufficient O2 cleaning, the optical emission indicates that the photoresist residue is not completely removed from the chamber. This leads to decreasing contact etch rate as the cassette of wafers is etched. This can be detected by noting the variation in the time dependence of either the C2 or SiF optical emission signal. The work reported here was done in an Applied Materials HDP 5300, but the authors have confirmed that a similar optical emission technique can be used to determine contact etch rate variation in the LAM TCP.
Homogeneity characterization of a large microwave plasma
Authors: Béchu S. , Boisse-Laporte C. , Leprince P. , Marec J.
Published: July 2002

Microwave plasma reactor without magnetic field has been designed for large surface treatment or deposition. Using the surfaguide principle, a 2.45 GHz wave is coupled to the plasma created in a 12 cm tube diameter surrounded by a metallic cylinder of 18.8 cm diameter. The aim of this article is to characterize this plasma, particularly the spatial homogeneity, along the tube and mainly over its section. Argon and oxygen gases have been used. Pressure and microwave power were in the range 0.01–5 Torr and 200–2000 W. Wave propagation study has shown that mainly a plasma mode (surface wave) of azimuthal hexapolar symmetry (π/3 periodicity) propagates. In argon gas, electron and ion densities (1011–1012 cm−3), and electron mean energy (1–4 eV) locally measured by probes, are quite homogeneous over the plasma section. Emission spectroscopy provides excited states repartition. These external diagnostics have been performed along several axes to obtain quasi local information. Azimuthally, the excited states are quite homogeneous at low pressure, and weakly modulated (π/3 periodicity) at higher ones. Radially, the profile depends on the electric field repartition. Actinometry has shown that the atomic oxygen density is rather homogeneous over the section, promising for future surface treatment applications.
Electrical characterization of Uromyces germ tubes grown on integrated circuit substrates
Authors: McNally Helen A. , Kozicki Michael N. , Roberson Robert W. , Whidden Thomas K.
Published: July 2002

The electrical characterization of a biohybrid integrated circuit is described. Uromyces appendiculatus is the biological moiety and an integrated circuit provides the electrical interface between the biological element and the test equipment. Direct current characterization has shown the current flow to be nonlinear with a time constant of 30–60 s. The conductivity is believed to be ionic through intracellular ions of the fungal cell. Locations of the germ tube which have different ion compositions have shown contrasting responses to testing over time. Potential applications are reviewed.
Microstructure and surface morphology of cryogenic processed thin metal films studied by atomic force microscope
Authors: He L.
Published: July 2002

Thin metal films of Au and Al were deposited by thermal evaporation at a substrate temperature of 77 K [low temperature (LT)]. For comparison purposes, the same films were also prepared with the substrates at room temperature (RT) of 300 K. The surface morphology and microstructure of these films were studied by atomic force microscope. The film thicknesses used were 100 and 200 Å. At a thickness of 100 Å, the LT Au film consisted of smaller-sized grains showing smoother surface morphology, whereas the RT Au film appeared to have a rougher surface. At a thickness of 200 Å, the LT Au film showed much larger-sized grains. The 200 Å RT Au film showed surface morphology similar to that of the 100 Å RT Au film. For Al films, the 100 Å film showed smaller-sized grains for both LT and RT depositions. As the thickness increased, the 200 Å Al LT film showed much larger-sized grains, similar to that of the 200 Å Au LT film. Since the larger-sized grains were observed in both 200 Å Au and Al LT films, less surface scattering was expected which resulted in the low resistivity in the LT films.
SiGe/Ge heterojunction infrared detector
Authors: Jiang R. L. , Gu S. L. , Jiang N. , Li Z. , Xu J. , Zhu S. M. , Hu L. Q. , Zheng Y. D.
Published: July 2002

Novel SiGe/Ge heterojunction infrared detectors have, for the first time, been fabricated with Si1−xGex–Si heterostructures epitaxially grown on Ge substrates by rapid thermal process/very low pressure-chemical vapor deposition. The peak value of the spectrum response ranges from 1.3 to 1.55 μm. The responsivity at 1.55 μm is higher than 0.7 A/W at zero bias. The dark current density is as low as 4×10−7 A/mm2 at −5 V.
Polymerization of fluorocarbons in reactive ion etching plasmas
Authors: Stoffels W. W. , Stoffels E. , Tachibana K.
Published: July 2002

Polymerization reactions in radio frequency fluorocarbon plasmas of CF4, C2F6, and C4F8 have been studied by electron attachment mass spectrometry (EAMS). In these plasmas polymerization occurs readily and molecules containing up to ten carbon atoms (the mass limit of the mass spectrometer) have been found. The densities of large polymers increase with increasing size of the parent gas. In a fluorine-rich environment like a CF4 plasma the detected polymers are mainly fully saturated with F (CnF2n+2). As the amount of fluorine in the parent gas decreases, also the degree of saturation of the polymers decreases, which is clearly seen in C2F6 and C4F8 plasmas. The unsaturated polymers are more reactive, so they can stick more easily to surfaces and possibly create thick polymer films, which are often observed after discharge operation. The polymerization rate depends on the chemical activity of the plasma, which can be easily enhanced by increasing the radio frequency power. The positive ions, extracted from the plasma, are generally somewhat smaller than the neutral polymers and their fluorine content is lower. This is probably due to dissociation of neutrals during their ionization by plasma electrons and to ion collisions in the sheath region. Finally, we have shown that EAMS has considerable advantages in the study of electronegative plasmas and polymerization processes in comparison with traditional mass spectrometry. Unlike the traditional mass spectrometry, employing ionization by high energy electrons, EAMS much better preserves the structure of high polymers, allowing us to detect them as large negative ions.
Penning type magnetron sputtering source and its use in the production of carbon nitride coatings
Authors: Murphy M. J. , Monaghan J. , Tyrrell M. , Walsh R. , Cameron D. C. , Chowdhury A. K. M. S. , Monclus M. , Hashmi M. S. J
Published: July 2002

This article describes the design and construction of a Penning type sputter magnetron which is referred to as the Dimag source. This device is capable of producing intense discharges at pressures well below those obtainable using a conventional magnetron source. Expressions used to describe the associated magnetic field are highlighted. An account of the effective potential well as seen by charged species within the plasma is given. Various operational parameters are described. The device is used to produce carbon nitride coatings with high atomic percent nitrogen incorporation.