bluuebunny/crossref_metadata_2025 huggingface dataset:
Emission spectroscopy and actinometry in a magnetized low pressure radio frequency discharge
Authors: Kuypers A. D. , Koch A. , Hopman H. J.
Published: July 2002

A low pressure 13.56 MHz radio frequency (rf) discharge is generated between two coaxial cylindrical electrodes, and is confined by two different types of magnetic field. A plasma electron temperature Te of typically a few electron volts is estimated from experimental spectroscopic data. Application of a homogeneous magnetic field appears to lower this Te by a few tenths of electron volts. Spatially resolved emission spectroscopy in an argon disharge shows that the magnetic confinement of plasma electrons leads to nonuniform emission intensities. The observed distributions can be related to ion density profiles, which have been measured with a Langmuir probe. It is shown that, at the low gas pressures considered here (several milliTorr), metastable states play an important role in the excitation and ionization mechanisms sustaining the discharge. Both experimental and theoretical arguments are presented to support this view. Actinometric measurement of the relative fluorine density in a magnetized CF4 discharge indicates a high density of fluorine radicals. Only at low pressures an additional increase of the fluorine density is observed for higher magnetic field strengths.
Outgassing properties of a commercial fiber fabric material for high temperature use in high vacuum
Authors: Sinharoy S. , Lange W. J. , Freidhoff C. B.
Published: July 2002

The outgassing properties of baked and unbaked NextelTM 440 (style BF–30) ceramic fiber fabrics manufactured by the 3M company have been measured to determine their suitability for high vacuum, high temperature, use as vacuum furnace lining materials. The results show that the as-received, prebaked material is suitable for use in high vacuum at temperatures up to 1150 °C (the highest attainable temperature in the experimental set up). However, the as-received unbaked fabric is totally unsuitable for vacuum use at any temperature higher than room temperature, due to the decomposition of the organic sizing in the fabric.
An ultrahigh vacuum scanning tunneling microscope for the investigation of clean surfaces
Authors: Wiesendanger R. , Buergler D. , Tarrach G. , Anselmetti D. , Hidber H. R. , Güntherodt H.-J.
Published: July 2002

An ultrahigh vacuum (UHV) scanning tunneling microscope (STM) has been built into a VG surface analysis system consisting of a VG Escalab and three additional UHV chambers. Samples and tips can be prepared in UHV. Surface analysis can be performed by low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), UV-photoelectron spectroscopy (UPS), and scanning electron/Auger microscopy (SEM/SAM). The STM design is based on an electromagnetically driven approach system. Easy exchange of samples is possible since the scanner is incorporated in a scan head which can be flipped backwards. The performance of the STM was tested by resolving the surface structure of graphite and Si(111)7×7. However, the main application will be the investigation of well characterized metal surfaces. We have studied the Au(111) surface where series of monoatomic steps could be imaged. In addition, we resolved the atomic surface structure. The conditions for atomic resolution imaging on close-packed metal surfaces are discussed. For comparison, we have also studied polycrystalline Au films vacuum deposited onto various substrates. For the first time, atomic resolution could also be obtained on these polycrystalline films. Finally, we present preliminary results of STM studies on a gallium single crystal.
X-ray photoelectron spectroscopy study of the formation of the merocyanine/aluminum interface
Authors: Zhang Yadi , Huang Songyu
Published: July 2002

High-resolution x-ray photoelectron spectroscopy has been applied to study the formation of the merocyanine/aluminum interface. It is concluded that merocyanine exists in zwitterionic form and aluminum bonds with merocyanine at −O–C– and C=O in carbonyl group, forming the complex compound of C–O–Al. The attenuation curves of C,N,O,S exhibit the cluster growth of aluminum, which preferentially resides on heterocycles. The temperature effect on merocyanine/Al interface is also investigated in detail.
A new electron beam evaporation source for Si molecular beam epitaxy controlled by a quadrupole mass spectrometer
Authors: Peter G. , Koller A. , Vazquez S.
Published: July 2002

A new electron beam source was developed according to ultrahigh vacuum design rules. It is rate controlled by means of a quadrupole mass spectrometer based flux meter. Preprogrammed and stored wobble patterns with a large frequency range prior and (for most materials) during evaporation improve the performance of operation and enable a high utilization of the material. A very stable operation is achieved by simultaneously controlling not only the power but also the power density. Long term stability, material utilization, dynamic range, minimum controllable rate and reproducibility were investigated especially for Si molecular beam epitaxy.
Sliding friction measurements of molecularly thin films
Authors: Krim J. , Chiarello R.
Published: July 2002

Slippage behavior of Xe and Kr monolayers and bilayers adsorbed on gold substrates has been investigated by means of a quartz crystal microbalance. The experiments have been carried out for both solid and liquid layers, and also for films which solidify as the surrounding vapor pressure is increased. Measurements carried out on bilayer films indicate moderate increases in slippage for both liquid and solid films as the second layer condenses. Solid films are observed to exhibit greater slippage than liquids on smooth substrates.
Photodesorption of CO, NO, and O2 from modified Ni(111) surfaces
Authors: Yoshinobu Jun , Guo Xingcai , Yates John T.
Published: July 2002

Photodesorption of CO, NO, and O2 from modified Ni(111) surfaces has been studied. Both direct observation of photodesorption and postirradiation thermal desorption measurements have been carried out. In each case, the photodesorption process is first order in photon flux and first order in the coverage within particular chemisorption states. The photon energy dependence of the photodesorption cross section was measured in the energy range from ∼1.4 to 5.4 eV using a filtered Hg lamp. The CO photodesorption was observed only on the oxidized Ni(111) surface: no CO photodesorption was observed on the clean Ni(111) surface nor Ni(111) containing chemisorbed O and S. The photon energy dependence of the cross section for CO and O2 photodesorption resembles the optical absorption spectrum of NiO. We propose that, in the case of chemisorbed CO and O2 on NiO, photodesorption is induced by the NiO band gap interband transition. However, NO photodesorption occurs not only on the oxidized Ni(111) surface but also on the Ni(111) surfaces containing chemisorbed O and S. This observation suggests that NO photodesorption is induced by valence electron excitation in the NO-metal complex, but does not exclude the possibility of a contribution also from hot electron excitation in the substrate.
Plasma desorption mass spectrometry with coincidence counting for the analysis of polymer surfaces
Authors: Park M. A. , Cox B. D. , Schweikert E. A.
Published: July 2002

Coincidence counting techniques were used in conjunction with plasma desorption mass spectrometry (PDMS) for the analysis of polymer surfaces. Both single-component and polymer-blend surfaces were examined. All of the polymers investigated yield characteristic PDMS spectra. By observing the correlations between secondary ions in the PDMS information normally not available was obtained on the chemical structure of the polymers. Also, we were able to determine the yield of various secondary ions without knowledge of the number of primary ions striking the surface. The yield information was useful for determining the surface and bulk concentrations of the components of the blends. It was found that the surface concentration of poly(styrene) in the miscible poly(styrene)/poly(vinyl methyl ether) blends was the same as that in the bulk.
Core level and valence band x-ray photoelectron spectroscopy of gold oxide
Authors: Aita Carolyn Rubin , Tran Ngoc C.
Published: July 2002

Reactive sputter deposition was used to grow a phase-separated 0.40 Au/0.56 Au2O3/0.04 Au-hydroxide cermet film and x-ray photoelectron spectroscopy was used to examine the Au 4f and O 1s core electron binding energy of each phase. The valence band structure of Au2O3 is reported here for the first time, and consists of an O 2p electron-derived peak centered at 5.5 eV and a density of states that approaches zero at the Fermi energy, characteristic of a semiconductor. The results are compared to other third long period conducting and semiconducting oxides.
Molecular beam studies of adsorption dynamics
Authors: Arumainayagam Christopher R. , McMaster Mark C. , Madix Robert J.
Published: July 2002

We have investigated the trapping dynamics of C1-C3 alkanes and Xe on Pt(111) using supersonic molecular beams and a direct technique to measure trapping probabilities. We have extended a one-dimensional model based on classical mechanics to include trapping and have found semiquantitative agreement with experimental results for the dependence of the initial trapping probability on incident translational energy at normal incidence. Our measurements of the initial trapping probability as a function of incident translational energy at normal incidence are in agreement with previous mean translational energy measurements for Xe and CH4 desorbing near the surface normal, in accordance with detailed balance. However, the angular dependence of the initial trapping probability shows deviations from normal energy scaling, demonstrating the importance of parallel momentum in the trapping process and the inadequacy of one-dimensional models. The dependence of the initial trapping probability of Xe on incident translational energy and angle is quite well fit by three-dimensional stochastic classical trajectory calculations utilizing a Morse potential. Angular distributions of the scattered molecules indicate that the trapping probability is not a sensitive function of surface temperature. The trapping probability increases with surface coverage in quantitative agreement with a modified Kisliuk model which incorporates enhanced trapping onto the monolayer. We have also used the direct technique to study trapping onto a saturated monolayer state to investigate the dynamics of extrinsic precursor adsorption and find that the initial trapping probability onto the monolayer is higher than on the clean surface. The initial trapping probability onto the monolayer scales with total energy, indicating a highly corrugated interaction potential.
Comparison of stress and structural composition of sputter deposited thick coatings of TiB2+Ni on polymeric composites
Authors: Taylor K. A. , Emrick A. J.
Published: July 2002

The total induced stresses in Ni–TiB2 coatings with chromium interfacial coatings deposited on fiber impregnated polymer matrix composites by magnetically enhanced direct-current sputtering was determined. The thickness of the Ni–TiB2 coatings was approximately 25.4 μm and the thickness of the chromium interfacial coatings ranged from 5.1 to 12.7 μm. Stress values were obtained using the bending-beam method where stress is calculated from the measured deflection of the composite beam formed by the coating and substrate combination using the equivalent stiffness method. The structural composition of the coatings was examined by scanning electron microscopy, energy dispersive analysis by x ray, and x-ray diffaction techniques. Intrinsic, thermal, and shear stress values are compared with the structural composition of the coatings and their resistance to a pressure driven flow of abrasive alumina particles.
Characterization of TiN films deposited using multicathode unbalanced magnetrons
Authors: Rohde S. L. , Nelson A. J. , Mason A. , Sproul W. D.
Published: July 2002

Unbalanced magnetrons can be very effectively utilized to provide enhanced ion bombardment of the substrate/film couples during deposition, and in multicathode systems it should be feasible to coat complex three-dimensional components uniformly and reproducibly. In this research, titanium nitride films were deposited using multicathode unbalanced, reactive, magnetron sputtering under a variety of ion bombardment fluxes, ion energies, nitrogen partial pressures, and total system pressures. In addition, several titanium aluminum nitride films were deposited for comparison. Through the use of carefully characterized magnetic field geometries, ion current densities ranging from 2 to 6 mA/cm2 have been generated, giving rise to ion-to-deposited Ti-atom ratios ranging from approximately 1.4:1 to 6.3:1. The films have been characterized in terms of their physical properties, chemical composition, crystallographic orientation, and film structure. Most of the films are approximately 3 μm thick, exhibit critical adhesive loads in excess of 5 kg, and have Vicker’s microhardness values of 2000 or more. Chemical characterization was performed using a scanning electron microscope with energy dispersive x-ray analysis (EDAX), a scanning transmission electron microscope with EDAX, and an electron microprobe. The majority of the films examined showed (111) preferred orientations and distinct columnar grain structures. No layering or shadowing effects were observed in cross section transmission electron microscopy studies.
In situ measurement of temperature uniformity of disk substrate in an in-line sputtering system
Authors: Fujita E. , Furusawa K. , Kataoka H. , Tsumita N. , Yonekawa T. , Shige N.
Published: July 2002

Thin films of Co-alloy/Cr are currently used in magnetic disks for high density recordings. Recent studies have clarified that deposition temperature exerts a profound affect on the coercive force of these Co-alloy/Cr films. Thus, it is important that substrate temperatures should be kept as uniform as possible both within and between the substrates. However, it is difficult to measure the temperature of Ni–P-plated Al substrates using thermocouples or radiation thermometers, because the substrates are moving in a vacuum in an in-line sputtering system, and because the substrates have reflective surfaces of low emissivity. This report describes a thermal video system that was applied to measure the temperature uniformity of the substrates during transport. It is well known that infrared images are greatly degraded by stray infrared rays. Therefore, we developed a sputtering system with a duct in which the optical path was designed to restrict the infrared image and thereby reduce the stray infrared radiation. The duct was equipped with a window highly transmissive with respect to infrared rays, and was shaped so as to shield the duct from the stray infrared radiation sources. The duct was also plated with blackbody material to absorb stray infrared radiation and water cooled so as not to emit such radiation. Using this scheme, the temperature uniformity of the substrates was measured over a relatively large area including several substrates at deposition temperatures of about 250 °C with an accuracy of ±5 °C.
Design and development of a vortex amplifier for pressure regulation of glove boxes
Authors: Balakrishnan M. G. , Mahule K. N. , Narayan Surya
Published: July 2002

Vortex amplifiers are fluidic devices which can be used for pressure regulation of glove boxes, radioactive cells, and other similar ventilated enclosures. This article describes the design and development of a vortex amplifier for use as a pressure regulator for glove boxes in which radioactive materials are handled. The vortex amplifier has several advantages over other types of pressure regulators like fast response, no electrical power supply, no friction or inertia as in the case of valves, and no mechanical moving parts.
Compositional dependence of stress in silver copper alloys prepared by direct current magnetron sputtering
Authors: Kazakos A. M. , Fahnline D. E. , Messier R. , Pilione L. J.
Published: July 2002

Metal thin films were prepared by dc magnetron sputtering in an argon plasma at a pressure of 2.5 mTorr and ambient temperatures. Alloy films of Ag–Cu were deposited by simultaneous sputtering of the two elemental targets, as well as metal films of Ag and Cu by sputtering from the appropriate pure target. Cosputtering provides a simple, direct method of preparing alloy films across the entire compositional range, as an alternative to sputtering from diphasic targets of single compositions. The low sputtering pressure utilized in this study insured the preparation of dense, smooth, highly reflective films, indicative of energetic ion bombardment. Total film stress was evaluated as a function of atomic composition and thickness (500, 1000, and 1500 Å). Extensive x-ray diffraction (XRD) analysis was performed to identify the alloy phases present, calculate their lattice constants, and determine orientation. The film stress became more compressive with increasing film thickness for each of the films studied. In addition, the film stress was found to vary as a function of film composition. The oscillation of the stress curve between tension and compression is explained by the atomic peening, increased grain boundary, phase separation, and plastic flow models.
Influence of recrystallization on the outgassing characteristics of copper
Authors: Kurosaka Akihito , Nakao Osamu , Yoshikawa Toshiaki , Ueki Masao
Published: July 2002

Disk specimens were prepared from high-purity copper and oxygen-free copper, which had a residual resistance ratio (RRR; p298 K/p4.2K) of 5450 and 207, respectively, and thermal desorption spectroscopy (TDS) measurement was applied for evaluating outgassing characteristics of those. For these types of pure copper, outgassing was encouraged by primary and secondary recrystallization. Particularly, the TDS spectra of H2, CO, CH4 and CO2, obtained from an as-rolled specimen of the high-purity copper, exhibited sharp peaks at the primary recrystallization stage. The outgassing characteristics of these pure copper depended on their recrystallized textures, so the amount of outgassing became lower with growing of recrystallized grains. With the high-purity copper, whose recrystallized grains were grown even by low-temperature annealing, secondary recrystallization progressed more rapidly than that with the oxygen-free copper.
Reactive ion etching of poly(tetrafluoroethylene) in O2–CF4 plasmas
Authors: Egitto F. D. , Matienzo L. J. , Schreyer H. B.
Published: July 2002

Films of poly(tetrafluoroethylene) (PTFE) were etched in O2–CF4 rf plasmas. The dependence of the etching rate of PTFE on the relative concentrations of these two gases was compared with data from optical emission spectra and measurements of peak-to-peak rf voltages Vpp indicative of relative sheath potentials. At a constant rf power (Vpp varied), etching rates were the greatest when using pure O2 and decreased with the addition of CF4. For Vpp held fixed (rf power varied), rates were invariant over a wide range of gas compositions. Ion bombardment-induced polymer radical generation is proposed as the initiating step in the PTFE etching sequence. Increases in etching rates with load size, contrary to conventional loading effect behavior, is attributed to a corresponding increase in Vpp for larger loads. Surface roughening induced by etching is more pronounced in oxygen-rich gas mixtures.
Core level x-ray photoelectron spectroscopy of AuxGay alloys
Authors: Jayne D. T. , Fatemi N. S. , Weizer V. G.
Published: July 2002

Five Au–Ga alloys have been studied using x-ray photoelectron spectroscopy as part of the program to determine alloy effects on core level binding energies and identify thin film and bulk compositions of unknown AuxGay alloys. The binding energies and peak intensities of the Au 4f, Ga 2p3/2, Ga 3p3/2, and Ga LMM core levels were determined for pure Au and Ga along with bulk alloy compositions of α-Au0.88Ga0.12, β-Au0.78Ga0.22, γ-Au9Ga4, AuGa, and AuGa2. These values were determined for surfaces scraped in situ to expose the bulk composition. The Au 4f7/2 binding energies were 83.95 eV for pure Au and 84.4, 84.6, 84.9, 85.2, and 85.5 eV for each of the respective alloys, while the Ga core levels and Auger energy shifted less than 0.3 eV over the range of alloy compositions. These results exhibit the same trend as the previously studied Au–In system and furnish calibration values that allow determination of the composition of unknown alloys.
Influence of the defects of a thin NiO(100) film on the adsorption of NO
Authors: Bäumer M. , Cappus D. , Illing G. , Kuhlenbeck H. , Freund H.-J.
Published: July 2002

Defects often play an important role for the adsorption and reaction behavior of a surface. This, however, is not the case with the adsorption of NO on NiO(100), as our experiments with a thin NiO(100) film grown on a Ni(100) substrate demonstrate. This film possesses a three-dimensional band structure, which is comparable to that of a NiO(100) single crystal. A spot profile analysis low-energy electron diffraction investigation shows that the film consists of crystallites, which are tilted with respect to the Ni substrate. The film must exhibit a high defect density where the crystallites border on each other. Moreover, x-ray photoelectron spectroscopic (XPS) measurements indicate the presence of O− or OH species on the surface. We have studied the adsorption of NO on a NiO(100) film via high-resolution electron energy-loss spectroscopy (HREELS), thermal desorption spectroscopy (TDS), and XPS. With HREELS and TDS we could only detect one kind of NO species on the surface. Comparing the TD and XP spectra of NO adsorbed on the film and on a bulk NiO(100) surface, which exhibits a much lower defect density, we can show that this species is NO adsorbed on regular, nondefect NiO sites.
Electron- and photon-stimulated desorption as a probe of the dynamics of molecules on surfaces
Authors: Xu Jun , Barnes Alan , Tolk Norman
Published: July 2002

This work examines the properties of excited molecules emitted from gas-dosed alkali-metal and alkali-halide surfaces due to electron- and photon-stimulated desorption (ESD and PSD) to elucidate molecular surface dynamical processes. Our measurements indicate that (1) CN adsorbates are generated when alkali-rich surfaces are exposed to gaseous CO2 and N2 molecules, (2) OH adsorbates are generated from exposure of the surfaces to gaseous H2 and CO2, (3) cross sections for CN* ESD and excitation functions for CN* PSD depend on alkali-CN parent bonds on the surface, and (4) rotational distributions of the electronically desorbing excited CN exhibit temperature-independent non-Boltzmann features which systematically depend on substrates. This research demonstrates that desorbing molecules, arising from ESD and PSD, constitute an internal-state-resolved and surface-bond-sensitive probe which gives information on the static and dynamic properties of surface molecular systems.
Modification of Schottky barrier heights at InP(110) interfaces using Sb interlayers
Authors: Yamada Masao , Green Albert M. , Wahi Anita. K. , Kendelewicz Tom , Spicer William E.
Published: July 2002

A Schottky barrier height of 0.82 eV is reported on n-InP. This is obtained by a new technique which may have much more general applications. In order to control the Fermi level at InP interfaces, we propose a new method using Sb interlayers at metal-InP interfaces. The deposition of two monolayers of Sb followed by annealing near 300 °C gives nearly the flatband condition for both n- and p-type InP indicating that there is no significant density of Sb-induced states in the gap. Au and Ag are nonreactive on these Sb-passivated surfaces, while Pd, Cu, and Al are reactive. Although Schottky barrier heights on n-InP without Sb interlayers range from 0.3 to 0.55 eV, those with Sb interlayers fall in a range from 0.45 to 0.85 eV. The modification of the Schottky barrier heights by the Sb is striking especially in nonreactive cases (Au and Ag). In this case, the surface Fermi level shows a tendency to converge at about 0.55 eV (±0.05 eV) above the valence-band maximum for both n- and p-type InP. A defect model is proposed to explain these phenomena self-consistently.
Vacuum behavior of the x-ray lithography source
Authors: Halama H. J. , Murphy J. B.
Published: July 2002

Photon stimulated desorption (PSD) is the major source of the gas load in electron storage rings and therefore strongly influences both beam lifetime and beam quality. The 200 MeV compact ring at the National Synchrotron Light Source is an ideal tool to study PSD since its energy can be varied from 60 to 200 MeV and the photoelectrons produced by synchrotron radiation can be measured in clearing electrodes installed to collect trapped ions. Using these electrodes we show: [a] photoelectrons are produced only by photons having energy above 10 eV and [b] desorption is proportional to the number of photoelectrons. Using calibrated gauges we conclude that (a) time-integrated beam current of 10–20 A h is needed for initial vacuum chamber clean up, (b) venting the chamber to dry nitrogen has a negligible effect on subsequent desorption, and (c) venting to air requires about 10 A h of beam conditioning.
Cu/PI and Cu/PET adhesion: Influence of Si+ ion mixing
Authors: Galuska A. A.
Published: July 2002

The adhesion and interfacial chemistry of 50 nm Cu films on poly[N,N- (p,p′-oxydiphenylene) pyromellitimide] (PI) and poly(ethylene terephthalate) (PET) substrates were examined as a function of 28Si+ implantation through the interfaces. The implantation was performed with 70 keV 28Si+ to doses between 1 and 10×1016 Si/cm2, while the substrate temperature was kept between 50 and 80 °C. The implantation induced extensive interfacial mixing and interfacial chemistry changes in both the Cu/PI and Cu/PET specimens. X-ray photoelectron spectroscopy analysis of the ion-induced Cu/PI interfacial chemistry indicated that the implanted 28Si+ had reacted with both the film substrate species to form Cu–Si, Si–O, and Si–C bonding, which suggested the formation of interfacial complexes, such as Cu–Si–C and Cu–Si–O–C. Similar interfacial chemistry was produced in the Cu/PET specimens by the implantation. However, additional Cu 2p3/2 and O 1s peaks associated with Cu–O–Si bonding were observed, suggesting the formation of Cu–O–Si–C interfacial complexes. Despite these changes in interfacial chemistry, only small (factor of 2) changes in adhesion were observed upon scratch testing. The absence of larger adhesion increases was attributed to the rather weak bonding between Cu and Si.
Robust rim phase shifting masks by selective diamond deposition
Authors: Lee G. S. , Zhang C. J. , Choi S. Y. , Feldman M.
Published: July 2002

Diamondlike films were selectively deposited on the chromium of optical masks by hot filament and ac discharge plasma chemical vapor deposition. The deposited films were characterized by scanning electron microscopy and Auger electron spectroscopy. Because of their robust nature and the ease of control of their thickness, such films are promising candidates for rim phase shifting masks.
Heteroepitaxial growth of alkali halides on a GaAs(001) substrate
Authors: Nakamura Yuji , Saiki Koichiro , Koma Atsushi
Published: July 2002

Heteroepitaxial growth of alkali halides on GaAs(001) substrates was studied by use of reflection high-energy electron diffraction and electron energy loss spectroscopy (EELS). In the case of NaCl growth on a GaAs(001) substrate (misfit 0.40%), epitaxial growth occurred when the substrate temperature was between 100 and 300 °C. EELS revealed that the NaCl film thicker than 3 nm completely covers the substrate and that the grown film is stoichiometric. This contrasts with the case of KBr growth on a GaAs(001) substrate, where epitaxial growth was not observed. The latter result seems to be due to the large misfit (16.8%). However, KBr was found to grow epitaxially on a NaCl-on-GaAs(001) substrate. The NaCl epilayer enables heteroepitaxial growth of another foreign alkali halide.
Electronic and geometric effects in tunneling images of silicon based heteroepitaxial growth
Authors: Kubby J. A. , Greene W. J.
Published: July 2002

The tunneling microscope is used to investigate heteroepitaxial growth of germanium on a silicon substrate. Deposition of a few monolayers of germanium on the Si(111)-7×7 surface leads to the formation of a Ge/Si(111)-5×5 surface, that at some biases has the appearance of an ordered Ge–Si alloy. We consider the mechanisms that could give rise to the appearance of an ordered surface alloy, and find that the most likely mechanism is not surface alloying, but rather an electronic effect associated with a buried stacking fault defect.
On electron-beam-induced charging effects in Cu- and Y-deposited LaAlO3 surfaces
Authors: Andersen Jens E. T. , Mo/ller Preben J.
Published: July 2002

Electron-impact experiments on insulator and wide-band-gap semiconductor surfaces are disturbed by charging effects, particularly in cases of stoichiometric surfaces. We have studied the shift in kinetic energy of Auger electrons from 1×1 LaAlO3(100) surfaces as a function of Cu coverage, time of electron-beam bombardment, heat treatment, and−also for an Y deposited 1×1 LaAlO3(100) surface−of primary beam energy. The energy shift is found to increase with metal coverage and with primary beam energy. It is suggested that at a particular energy the incident electrons result in a repulsive potential from which escaping Auger electrons gain kinetic energy, and that the initially deposited metal atoms may cause moving of electrons into valence-band states created by hybridization of surface metal and oxygen states. For comparison, the energy shifts in nondeposited LaAlO3(100), MgO(100), and SrTiO3(100) were also investigated.
Graded refractive index silicon oxynitride thin film characterized by spectroscopic ellipsometry
Authors: Snyder Paul G. , Xiong Yi-Ming , Woollam John A. , Al-Jumaily Ghanim A. , Gagliardi F. J.
Published: July 2002

A graded refractive index silicon oxynitride (SiOxNy) thin film was prepared on a silicon substrate by ion assisted deposition. Spectroscopic ellipsometry (SE) was used to optically analyze the film. The measured SE spectra (2500–8200 Å) were analyzed with several fitting models, whose construction was based on an Auger depth profile of the film. In each model, the optical response of SiOxNy was described using the Bruggeman effective medium approximation, by modeling it as a physical mixture of two distinct phases: silicon dioxide and silicon nitride. Grading was modeled by varying the silicon nitride volume fraction with depth below the surface, according to an assumed profile. Fitting results were very sensitive to the profile chosen, which was different for each model. Experimentation with the profile led to a model which produced a remarkably good fit, over the entire spectral range. As a result, the film thickness and its refractive index profile were determined. The index profile determined by SE analysis was found to be consistent with the Auger profile.
Fabrication of waveguides using low-temperature plasma processing techniques
Authors: Bulat E. S. , Tabasky M. , Tweed B. , Herrick C. , Hankin S. , Lewis N. J. , Oblas D. , Fitzgerald T.
Published: July 2002

The proliferation of the use of light as the transfer medium in communications has brought about some unique technical challenges. Among these is the development of devices that route optical signals at points where optoelectronic conversions are necessary. In this article we discuss the fabrication of silicon oxide waveguides on silicon substrates, describing low-temperature plasma deposition processes and the relationship between crucial optical parameters of the films and the significant processing parameters. The waveguides are buried-ridge, single-mode waveguide structures fabricated using two deposition techniques: plasma-enhanced chemical vapor deposition and low-pressure chemical vapor deposition. We will present the plasma deposition conditions established to control the two refractive index differences (Δn) of 0.065 and 0.020 between the guiding and cladding layers for two different waveguide designs. Uniformity of the Δn as a function of plasma conditions and dopant species will be presented for the guiding layer. The analytical techniques used to evaluate the properties of the guiding layers doped with fluorine and nitrogen consisted of Auger spectroscopy, infrared spectroscopy, ellipsometry, and prism coupling techniques. In addition, we will present the plasma etching conditions required to fabricate of the waveguiding ridge structures. The etch rates and uniformities obtained in two different reactors using either SF6 or CF4 chemistries will be discussed.
Differential pumping of Ar/H2 gas mixtures and carbon film deposition
Authors: Coffey Kevin R. , Reith Timothy M.
Published: July 2002

The deposition of hydrogenated carbon thin films is currently of technological interest to thin film disk manufacturing. The use of Ar/H2 gas mixtures to deposit these films is complicated by the differences in molecular flow properties of Ar and H2. As a result, the hydrogen concentration in the deposition chamber is not necessarily equal to that of the supply gas. The difference can be significant and is variable. The variation is due to vacuum pumping system design and adjustment, as well as carbon film deposition conditions. The need to control this variation is based upon the desire to provide hydrogenated carbon films with controlled composition.
Fluorocarbon high density plasma. V. Influence of aspect ratio on the etch rate of silicon dioxide in an electron cyclotron resonance plasma
Authors: Joubert O. , Oehrlein G. S. , Zhang Y.
Published: July 2002

Etching of high aspect ratio patterns induces a phenomenon known as reactive ion etching (RIE) lag, i.e., a large feature etches faster than a smaller one. This effect is studied for oxide etched in a high density plasma excited by electron cyclotron resonance using different fluorocarbon gases. The magnitude of the RIE lag is correlated with the deposition rate of fluorocarbon film on an unbiased sample, showing that chemical effects are important to understand the mechanisms of RIE lag in high density plasmas.
Preparation of highly oriented thin film of nonlinear optical material by vacuum deposition
Authors: Inoue Atsuhisa , Okamoto Mariko , Akagi Yoshiro , Koba Masayoshi
Published: July 2002

Highly (001)-oriented thin films of 4-(N,N-dimethylamino)-3-acetamidonitrobenzene were prepared on a thermally oxidized silicon substrate using vapor deposition. The degree of (001) orientation depends considerably on the substrate temperature (Ts) and deposition rate (R), which determines the kinetic energy (Ek) of the molecules in a flux. Under the optimized experimental parameters of Ts=30 °C and R=600 nm/min, we fabricated the (001)-oriented thin film showing the full width at half-maximum of x-ray rocking curve of 1.6°. Surface flatness was also improved as the deposition rate increased. It became clear that kinetic energy (Ek) of the molecules in an evaporating flux strongly promoted (001) preferred orientation as could be seen by observing the surface morphology and a cross-sectional view of the samples at their initial stage of growth.
Plasma fluorination of graphite
Authors: Merfeld Glen D. , Petrich Mark A.
Published: July 2002

Fluorinated graphites are low surface energy, thermally stable solids that have applications as moisture resistant lubricants, water repellents, release agents, and lithium battery cathodes. Conventional methods of synthesizing fluorinated graphite, however, make inefficient use of fluorine feed stocks, are time consuming and limited by safety considerations. In this article, we demonstrate that plasma processing techniques can be used to fluorinate graphite surfaces and thereby reduce the surface free energy from an untreated value of 50 mJ/m2 to as low as 7 mJ/m2. Pressed graphite pellets and graphite foils are exposed to nitrogen trifluoride and sulfur hexafluoride plasmas. Fluorination is monitored with x-ray photoelectron spectroscopy (XPS), while liquid contact angle measurements are used to assess the free energy of the treated surfaces. Results indicate that significant surface fluorination can be achieved in exposure times of 10–15 min and with only modest plasma energies of 0.2 W/cm2. X-ray photoelectron spectroscopy (XPS) confirms the formation of CF2 and CF covalent bonds. Fluorine depth profiles show that CF2 species predominate on the fluorinated graphite surface, while CF species are found in the subsurface at depths less than 100 Å.
Etching of aluminum alloys in the transformer-coupled plasma etcher
Authors: Ra Yunju , Bradley Stephen G. , Chen Ching-Hwa
Published: July 2002

Transformer-coupled plasma (TCP) technology has been applied to the etching of aluminum alloys. High density plasmas can be obtained at low pressures (∼10 mTorr) by inductive coupling of externally applied radio frequency (rf) power at the frequency of 13.56 MHz. The energy of the ions incident to the substrate is controlled by a separate capacitively coupled rf power supply. Cl2 and BCl3 gas chemistries were used for the etching. The characteristics of the plasma have been studied with a Langmuir probe and the ‘‘complex conjugate method.’’ The ion current density is mainly dependent on the rf power to the coil and gas pressure. The energy of ions bombarding the substrate surface can be controlled by changing the rf power to the bottom electrode and the coil. A statistical experimental method and optical emission spectroscopy were used to study the etching of the aluminum alloys with a TCP source. The results indicate that etching of aluminum alloys is dominated by chemical interaction with Cl2 gas whereas photoresist is etched by the bombardment of energetic ions.
Substrate amorphization induced by the sputter deposition process: Geometrical aspects
Authors: Valeri S. , Altieri S. , Di Domenico T. , Verucchi R.
Published: July 2002

Sputter deposition of thin films and multilayers involves, in the initial stage, the energetic interaction of reflected ions and/or sputter ejected target particles with the substrate surface and with the overlayer-substrate interface.The present work reports on the c-Si(111) surface amorphization when Ge is deposited by 4 keV Ar+ ion sputtering in different experimental geometries. The incidence angle of the Ar+ beam was 65°, with respect to the surface normal, to emphasize prompt collision sputtering. Attempts have been made to clarify the role of the different particles involved in the process. New, unconventional approaches to Auger spectroscopy were used for this study. Substrate structural characterization during overlayer growth has been performed by primary-beam diffraction modulated electron emission (PDMEE) technique, a powerful tool for the investigation of ‘‘buried’’ surfaces. Auger electron kinetic emission from the growing interface was used to determine the occurrence and importance of the different collisional processes. The high average kinetic energy of the Ge atoms ejected from the target in prompt, first-order collisions was found to be responsible for the large substrate amorphization we observed with a specular geometry but not on off-specular geometry. Reflected, energetic Ar+ ions do not play a relevant role.
Structure and morphology of microprotrusions grown on Ar+-sputtered InP
Authors: Kato J. , Nozu M. , Fujimoto Y. , Tanemura M. , Okuyama F.
Published: July 2002

Ar+ sputter-induced microprotrusions on monocrystalline InP at −100 °C, room temperature, and 100 °C were investigated by scanning and transmission electron microscopy. On a target cooled down to −100 °C, the protrusions were of dual structure, having an amorphous layer thickly covering the monocrystalline core. At room temperature, the protrusions that formed involved randomly oriented domains at the tip area, suggesting a recrystallization process occurring under ion impact. Heating the target to 100 °C resulted in a dramatic change in protrusion morphology and structure. Typically, the protrusions on the heated target could be classified as fibrous or whiskerlike protrusions or short ones topped with metallic crystallites. Crystal growth processes thus appeared to be involved in sputtering at 100 °C.
Nuclear microprobe analysis of Hg1−xCdxTe metal–semiconductor–metal detectors on substrates of GaAs and GaAs/Si
Authors: Leech Patrick W. , Witham Lachlan A. , Dooley Sean P. , Jamieson David N.
Published: July 2002

The ability of the nuclear microprobe with a 2 μm focused beam of MeV He+ ions to analyze the active region of individual Hg1−xCdxTe metal–semiconductor–metal (MSM) detectors has been demonstrated. Details of the channeling of Hg1−xCdxTe by Rutherford backscattering spectrometry and the incidence of defects imaged by channeling contrast microscopy were correlated with the performance of devices in a number of arrays. A series of linear growth defects was identified in the active region of some devices using channeling contrast microscopy. The channeling spectra that were extracted from these defective regions have shown a higher value of χmin=24% (the ratio of backscattered particle yield with the crystal 〈100〉 axis aligned with the beam to the yield for a random alignment) than the surrounding crystal χmin=9%–15%. The presence of these linear defects was linked to a degradation in the performance of the corresponding devices in an array. MSM detectors fabricated on Hg1−xCdxTe/GaAs/Si were lower in breakdown voltage than equivalent devices on Hg1−xCdxTe/GaAs. This trend corresponded to a higher value of χmin for the Hg1−xCdxTe on GaAs/Si than with the epitaxial layer grown on GaAs.
Desorption of positive and negative fluorine ions from BaF2 surfaces by core level excitation under electron bombardment
Authors: Petravić M. , Williams J. S.
Published: July 2002

Electron stimulated desorption of negative and positive fluorine ions from BaF2 surfaces has been studied as a function of impact electron energy. Thresholds observed for F+ and F− are correlated with core-level binding energies of Ba atoms. We propose that core level ionization of Ba ions, followed by an interatomic Auger decay involving halogen ions, can initiate F+ desorption, while the formation and subsequent breakup of superexcited molecular complexes containing a core hole can lead directly to the ejection of negative ions.
Characterization of low-resistivity indium oxide films by Auger electron spectroscopy, x-ray photoelectron spectroscopy, and x-ray diffraction and correlation between their properties, composition, and texture
Authors: Jeong J. I. , Moon J. H. , Hong J. H. , Kang J.-S. , Fukuda Y. , Lee Y. P.
Published: July 2002

Auger electron spectroscopy, x-ray photoelectron spectroscopy, and x-ray diffraction (XRD) were employed to investigate the stoichiometry and texture of the indium-oxide films. The films were prepared by the reactive evaporation and reactive ion plating of pure indium in an oxygen atmosphere of ∼10−4 Torr. Standard In and In2O3 grains were used to estimate the atomic concentration of the indium-oxide films and to identify the film orientation. We correlated the electrical and optical properties of the films with their atomic concentration and texture. It was found that the films exhibiting low resistivity have atomic ratios of O to In of 1.29–1.31 and full widths at half-maximum for (222) XRD peaks of 0.32°–0.34°.
High-pressure effects in miniature arrays of quadrupole analyzers for residual gas analysis from 10−9 to 10−2 Torr
Authors: Ferran R. J. , Boumsellek S.
Published: July 2002

The design, construction, and characterization of a miniature array of 16 rods forming nine quadrupole mass analyzers for residual gas analysis are presented. The novel design takes advantage of the reduction of the dimensions and hence the mean free path to broaden the dynamic range by extending the operating pressure range up to 10 mTorr at the high end while maintaining the low-end sensitivity and mass resolution. The small size, low weight, low power consumption, and low cost of this mass analyzer enable many new applications such as in situ process control in high pressure processes. Applications which take advantage of the capability of operating the source pressure two orders of magnitude higher than conventional devices such as high-pressure contaminant monitoring are discussed. Data on high-pressure effects on the ionizer lifetime in various atmospheres and nonlinearities of the signal are presented and correlated with theoretical analysis. Ray tracing simulations and Monte Carlo statistical calculations are used to provide an understanding of the sensitivity reduction at pressures substantially higher than 10 mTorr. These calculations take into account the ion charge density in the source and the dissociation, charge exchange, and energy loss by the ions when colliding with residual molecules along the length of the rods.
Measurements of spatial and temporal sheath evolution inside tubular material for inner surface ion implantation
Authors: Sun Mu , Yang Si-ze , Chen Xi-chen
Published: July 2002

Tubular target of aluminum (inner radius=5 cm, length=15 cm) was immersed in a nitrogen plasma with plasma densities of 6.8×109–5×1010 cm−3 and biased negatively (10–30 kV). A Langmuir probe was used to detect the propagating sheath edge. A comparison of experiment measurements and numerical calculations of temporal and spatial sheath evolution is presented. Experiment measurements of sheath edge position were in good agreement with those determined by numerical calculations.
Study on the interfaces of Cu/PA-N and PA-N/Si by secondary ion mass spectroscopy and scanning electron microscopy
Authors: Yang G.-R. , Mathur D. , McDonald J. F. , Lu T.-M.
Published: July 2002

For microelectronics applications, it is important to have good interfacial properties between copper and parylene-N (Cu/ PA-N), and parylene-N and silicon (PA-N/ Si). Two of the relevant interfacial properties studied in this article are diffusion of the individual layers into the other layer at application temperatures and adhesion between these layers. The interface between copper and parylene-N, and parylene-N and silicon has been studied using secondary ion mass spectroscopy (SIMS). Scanning electron microscopy (SEM) has also been used to study the PA-N/Si interface. SEM revealed the microstructure at the interface. SIMS was used to tunnel through the composite film in the cross section and get the various elemental concentrations. This gave the average concentrations prevailing, at a particular depth. It was observed that copper diffuses, from the top, through the PA-N film to the silicon substrate at 350 °C. Gettering of copper was observed, leading to high concentration of copper at the Cu/PA-N and PA-N/Si interface. A high distribution of silicon was observed in PA-N at the PA-N/Si interface. X-ray photoelectron spectroscopy studies showed that no new chemical bonds were formed. Thus, diffusion resulted in a mixing layer which led to good interfacial adhesion.