bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibrations in turbomolecular pumps: Spectra and source location
Authors: Casaro F.
Published: July 2002

The most common vibration sources for turbomolecular pumps together with their characteristic spectra are considered in this paper. In general, for a brand new pump, the largest contribution to vibrations comes from the residual unbalance of the rotor, which has been reduced below the maximum specified value after the balancing process. Moreover, other pump elements can become vibration sources during operation, normally because of the changed operating conditions of these elements. When this happens, the vibration level and noise of the pump tends to grow and reach values many times higher than those due to unbalancing. A typical case considered is bearing damage, detected by monitoring the pump vibration spectra. Damaged bearings produce vibration levels at different frequencies than those due to unbalancing (e.g., 0.5 to 5 times the rotational frequency, depending on the bearing failure position). Often this occurs a long time before the pump failure.
Ultrathin film growth of silicides studied using microprobe reflection high-energy electron diffraction and Auger
Authors: Bennett P. A. , Butler J. R. , Tong X.
Published: July 2002

The generic parameters and processes involved in solid phase epitaxial growth of ultrathin films by contact reaction are discussed. The particular strengths of quantitative reflection high-energy electron diffraction (RHEED) and Auger line-shape analyses for separating coexisting phases are demonstrated with examples from the Ni/Si(111) system. Using RHEED Kikuchi patterns and rocking curves, we identify the ordered structures NiSi2 (mixed A and B type) and Ni2Si-θ. From the Auger line shape we find that the low-coverage room-temperature material is disordered Ni2Si, the NiSi2 epitaxial layers are capped with a layer of excess silicon, and the surface layers pass through a NiSi-like phase in the transformation from Ni2Si to NiSi2.
Dispersion in the loss spectra from Na overlayers on Al(111)
Authors: Tsuei K.-D. , Heskett D. , Baddorf A. P. , Plummer E. W.
Published: July 2002

The dispersion of the energy-loss peaks for the ordered system, (√3×√3)R30° Na adsorbed on Al(111) surface, has been measured using angle-resolved electron energy-loss spectroscopy (EELS). We have created a simple but realistic model to evaluate the dispersion of EELS in terms of an interband transition in the Na layer. The previously published inverse photoemission data are used to determine the dispersion of the unoccupied Na bands. Our analysis indicates that the dispersion seen in the EELS measurements is inconsistent with a single-particle picture of interband transitions. We find that it is impossible to create any simple parabolic initial-state band capable of yielding the loss dispersion. One possible explanation is that as q∥ increases the interband transition couples to the collective excitation of the Na electrons, leading to a stonger dispersion of the measured energy loss than predicted by a single-particle picture.
A new method for analysis of reactive adsorbed intermediates
Authors: Campbell Charles T. , Rodriguez J. A. , Henn F. C. , Campbell J. M.
Published: July 2002

A new method for identification and quantitative analysis of adsorbed molecular intermediates will be described, and its first applications presented. Reactive adsorbed intermediates often dissociate upon heating. Since dissociation generally requires additional free sites on the surface, dissociation can be suppressed and desorption correspondingly enhanced if the free sites on the surface can be properly poisoned. We have found that bismuth adatoms are very good inert site blockers, which can be postdosed to the surface of a transition metal containing an adsorbed hydrocarbon without destroying the hydrocarbon. Whereas many hydrocarbons normally dehydrogenate during thermal desorption spectroscopy and liberate only H2 gas, after bismuth postdosing the hydrocarbon quantitatively desorbs intact for mass spectral identification and quantitation. This method has been used to prove that adsorbed benzene is the product of the dehydrogenation of cyclohexane on Pt(111) at ∼235 K. By briefly heating an adsorbed intermediate to increasing temperatures prior to Bi deposition, its thermal stability limits and dissociation kinetic parameters can be established. This is demonstrated for the dehydrogenation of adsorbed cyclopentene on Pt(111). Bismuth postdosing in thermal desorption mass spectroscopy may be a very useful but inexpensive addition to surface analytical capabilities.
Passivation of mercury cadmium telluride surfaces
Authors: Nemirovsky Y. , Bahir G.
Published: July 2002

The practical aspects of HgCdTe surface passivation, as related to devices and applications, are reviewed. Currently used technologies are classified in two categories: thick deposited dielectrics and a two-layer combination of a thin native film with a thick deposited dielectric film. The first category includes ZnS, low-temperature photochemical vapor deposited SiO2 (photox), and electron cyclotron resonance plasma deposited SiNx. The second category includes anodic oxide, plasma oxide, photochemical native oxide, anodic sulfide, and anodic fluorides. The unique behavior of HgCdTe surfaces, metal-insulator semicoductor structures, and gate-controlled p–n junctions are reviewed. The surface requirements of HgCdTe devices of interest for present and next-generation focal plane arrays are discussed in terms of the reviewed technologies.
Glow-discharge removal of codeposited carbon films in graphite-lined tokamak reactors
Authors: Hsu Wen L.
Published: July 2002

In a graphite-lined tokamak reactor, the interaction of the plasma with the graphite first wall will result in the formation of carbon deposits that are highly rich in tritium. This mechanism of tritium retention will be a major contributor to the in-vessel tritium inventory. In this paper, the glow-discharge technique is proposed for removing these films to reduce the inventory buildup. Glow-discharge runs were performed with feed gases of H2, He, N2, and O2. The results show that only oxygen glow discharges can remove carbon films at sufficiently large rates. The impact of this study on the Tokamak Fusion Test Reactor (TFTR) and the Compact Ignition Tokamak (CIT) is discussed. A recipe for effective glow-discharge operation on TFTR and CIT is also described.
Tritium retention on the Tokamak Fusion Test Reactor neutral beam components
Authors: Causey R. , Jalbert R.
Published: July 2002

When the Tokamak Fusion Test Reactor begins tritium operations in 1990, two of the neutral beams will operate with tritium. In addition, the cryogenic panels in all of the beams will provide most of the pumping for the torus. Measurements were conducted at two different laboratories to measure the tritium retention on materials used in these beam lines. Experiments were performed at Los Alamos National Laboratory and Sandia National Laboratories at Livermore to examine the room-temperature adsorption of tritium on materials such as thermocouple wires, insulation, epoxy, bare metals, and painted metals. Results show the tritium retention in the neutral beams will occur primarily on the painted liquid-nitrogen-cooled panels.
Aluminum sputtering with intermittent pulse bias application
Authors: Shimamura Hideaki , Fujita Shoyo , Sakata Masao , Kamei Tsuneaki , Kobayashi Shigeru
Published: July 2002

dc aluminum bias-sputter deposition was studied to develop a process which better fits the requirements of very large scale integration applications such as improvements in the step coverage, control of film stress, and hillock formation. Intermittent negative bias voltage pulses were applied with a cycle period of 1 ms during the deposition of an aluminum film. The pulse has two voltage levels: Vd (deep) and Vs (shallow). The duty factor was defined as the ratio of time during which the bias voltage is Vd to the cycle period. It was found that a Vd greater than −115 V was needed to attain an appreciable improvement in the step coverage. For a duty factor of 15%, a maximum was found in the peak intensity ratio I(111)/I(200) with x-ray diffractometry at Vd=−120 V. Minima for the film stress at room temperature and the hillock formation density after annealing at 475 °C for 30 min in nitrogen were found to occur in the bias voltage region mentioned.
Transport properties of sputtered molybdenum silicide thin films as a function of grain size
Authors: Thorpe T. P. , Morrish A. A. , Qadri S. B.
Published: July 2002

Molybdenum disilicide films have been sputtered onto sapphire and silicon substrates with a wide range of grain sizes achieved by postdeposition vacuum anneals at temperatures ranging between 200 and 1000 °C. Grain size of each film is determined by measurement of the breadth of observed x-ray diffraction peaks. Electrical resistivity as a function of temperature and room-temperature Hall effect has been measured for each film. Transport properties are related to grain size using scattering models developed for polycrystalline metals. A close fit to theory is obtained.
Growth and material characterization of PbSnSe/PbSe heterostructures
Authors: Martínez-Collazo Antonio , Santiago Francisco , Chu Tak-Kin
Published: July 2002

Heterostructures of Pb1−xSnxSe (PbSnSe) and PbSe (0.11<x<0.30) have been grown on (111)-oriented BaF2 substrates using a two-furnace hot-wall evaporator. Individual layers were grown with thicknesses down to 100 Å. The quality and the composition of the samples were established through the use of depth profiling Auger electron spectroscopy and x-ray diffraction. No appreciable alloying at the interfaces was detected by either technique. It was found that the SnSe mole fraction x obtained in the samples depends significantly on the substrate temperature. This allowed for the growth of single layers, as well as heterostructures, with different mole fractions using the same source material by adjusting the substrate temperature Tsubs (330 °C<Tsubs <370 °C).
Scanning probe microscopy: Current status and future trends
Authors: Wickramasinghe H. Kumar
Published: July 2002

The scanning tunneling microscope has shown us that it is possible to control and scan a tip over a conducting surface with angstrom precision. More recently, the same generic principle of the scanning tunneling microscope (STM) has been applied to many other novel scanned probe microscopies. In general all these microscopies come under the class of microscopy called superresolution microscopy—i.e., the spatial resolution achievable is far better than that dictated by the wavelength used to form, the image. Following a review of the history behind the development of scanned probe microscopes, is presented work on the recent developments in the areas of atomic force microscopy, magnetic force microscopy, electrostatic force microscopy, near-field thermal microscopy, and near-field acoustic microscopy. These will be highlighted by results from each area which illustrate the potential of these techniques to provide new information about the physical properties of surfaces on a nanometer scale.
Behavior of gallium on vicinal Si(100) surfaces
Authors: Nogami J. , Baski A. A. , Quate C. F.
Published: July 2002

The behavior of sub-monolayer coverages of Ga on vicinal Si(100) surfaces has been studied by scanning tunneling microscopy. Substrates were cut at 4° towards the (011) direction, resulting in a near-single-domain surface with double-height steps spaced an average of 39 Å (≊10 unit cells) apart. At room temperature, low coverages of deposited Ga do not disrupt the Si surface. The Ga atoms appear to lie on the existing Si dimers, appearing as bright features in the STM images. However, if the sample is annealed after Ga deposition, there is significant disruption of the step structure. At low coverages (<0.1 monolayer) the degree of disorder along the step edges appears to correlate with the amount of Ga on the surface. The double-height steps become kinked, or split into single height steps. Up to 0.1 monolayer no clear evidence of Ga growth on top of the Si dimers is observed, either at step edges or on the flat terraces. Rows and arrays of Ga are seen at higher coverages. Comparison of these results with earlier work on untilted Si(100) shows that Ga is more reactive at double-height steps than at single-height steps.
Electrical properties, stability, and applications of ultrathin porous Pt films on SiO2
Authors: Nowroozi-Esfahani Rasoul , Maclay G. Jordan
Published: July 2002

The morphology of 25 Å porous Pt films deposited on thermally grown SiO2 at room temperature and 250 °C is presented. The impedance of the films was measured over the frequency range 100 Hz to 1 MHz. At 1 kHz, the impedance was measured in electric fields up to 250 V/cm, over the temperature range −192–140 °C. The ac impedance of the 25 Å Pt film deposited at room temperature decreased by 25% in 21 days at 150 °C in room air but the ac impedance of the Pt film deposited at 250 °C did not show any change. The stable 25 Å film was used as a gate in a metal–oxide-semiconductor (MOS) sensor, which was exposed to 800 ppm H2/air at 100 °C and 1% CO/air at 150 °C. Measurements were made of the change in the impedance of the gate film and the change in the MOS capacitance.
Quasicrystalline phases and rational approximants obtained from vapor deposited Al–Mn thin films
Authors: Reyes-Gasga J. , José-Yacamán M.
Published: July 2002

Thin films produced from Al86Mn14 alloy were heated in situ in the transmission electron microscope. The deposited films were amorphous and, after heating, two metastable phases are obtained. These phases are strongly related to the quasicrystalline phases and the vacancy-ordered superstructures. The analysis shows that these phases can be described as rational approximants of the decagonal phase. The relation between the quasicrystalline and long-period superstructures is also proposed.
Applications of titanium sublimation traps to the scrubbing of reactive gases
Authors: Hu Yao-Zhi
Published: July 2002

Many applications exist for titanium sublimation traps (pumps) in the field of ultrahigh vacuum or oil-free vacuum where it is used with, a diffusion pump or ion pump. The work in this paper is directed to the particular application of scrubbing of reactive gases. Experimental results presented here show two small traps in series to be much more effective than a single large trap. The pressure of the reactive gases obtained in the double trap is two or three orders of magnitude lower than the pressure in the single trap. By using a quadrupole mass spectrometer with a mass range from 1 to 200 amu the major constituents of the residual atmosphere under various operating conditions were presented.
Impact collision ion spectrometry studies of the NiSi2(111) surface
Authors: Porter T. L. , Cornelison D. M. , Chang C. S. , Tsong I. S. T.
Published: July 2002

The technique of impact collision ion scattering spectrometry (ICISS) was used to study the composition and structure of the NiSi2(111) type B surface. Comparison of experimental data with computer simulation indicates that the surface consists of a Si bulk termination of the fluorite structure with an additional Si bilayer on top. These results are consistent with an additional Si bilayer model proposed from photoemission and scanning tunneling microscopy studies.
Adsorption energetics: First principles calculations of adatom interactions and induced local lattice relaxation
Authors: Feibelman Peter J.
Published: July 2002

Insight gained from the use of the first principles scattering theory of adsorption energetics is reviewed. Applications include the interaction and diffusion of two adsorbed Al atoms on Al(001), the interaction of an Al–S dimer on Al(001) and the nature of the local lattice relaxation induced by adsorption of S on the same surface.
Acceleration of small, light projectiles (including hydrogen isotopes) to high speeds using a two-stage light gas gun
Authors: Combs S. K. , Foust C. R. , Gouge M. J. , Milora S. L.
Published: July 2002

Small, light projectiles have been accelerated to high speeds using a two-stage light gas gun at Oak Ridge National Laboratory. With 35-mg plastic projectiles (4 mm in diameter), speeds of up to 4.5 km/s have been recorded. The ‘‘pipe gun’’ technique for freezing hydrogen isotopes in situ in the gun barrel has been used to accelerate deuterium pellets (nominal diameter of 4 mm) to velocities of up to 2.85 km/s. The primary application of this technology is for plasma fueling of fusion devices via pellet injection of hydrogen isotopes. Conventional pellet injectors are limited to pellet speeds in the range 1–2 km/s. Higher velocities are desirable for plasma fueling applications, and the two-stage pneumatic technique offers performance in a higher velocity regime. However, experimental results indicate that the use of sabots to encase the cryogenic pellets and protect them from the high peak pressures will be required to reliably attain intact pellets at speeds of ≊3 km/s or greater. In some limited tests, lithium hydride pellets were accelerated to speeds up to 4.2 km/s. Also, repetitive operation of the two-stage gun (four plastic pellets fired at ≊0.5 Hz) was demonstrated for the first time in preliminary tests. The equipment and operation are described, and experimental results and some comparisons with a theoretical model are presented.
A new shutter design with a modified effusion cell for use in an ultrahigh vacuum system
Authors: Lu H. C. , Chan W. S. , Sadwick L. , Wang K. L.
Published: July 2002

A new, inexpensive, reliable, computer-controlled shutter has been designed with a modified effusion cell on the same flange for thermal evaporation in an ultrahigh vacuum system. Only 5 W are required to control the shutter open/close states with a response time of less than 0.1 s. The evaporation rate can be modulated by varying the speed of rotation of the shutter. Rotary action is obtained through a coupled magnetic field. Doping levels between maximum and minimum flux can be achieved. About 100 W are needed for 1000 °C operation. A functional modified effusion cell was constructed using an available standard pyrolytic boron nitride crucible(10 cc capacity). As an example of the capabilities of this shutter-controller system, a linear ramped profile was demonstrated.
Ion implantation into (Hg,Cd)Te through dielectric encapsulants
Authors: Deutscher N. F. , Roedel R. J. , McIntyre L. , Leavitt J.
Published: July 2002

The effectiveness of indium tin oxide (ITO) and silicon dioxide as encapsulants for mercury cadmium telluride (MCT) has been investigated. Indium tin oxide and silicon dioxide of various thicknesses were sputtered onto samples of MCT. Samples were then implanted with aluminum and annealed in a conventional furnace. Rutherford backscattering (RBS) experiments were performed to examine Hg loss from the surface caused by the implantations and anneals. The RBS results do not indicate any Hg loss occurred during the implantation through the dielectric encapsulants. The RBS results do indicate that Hg was lost during the anneal from samples with the SiO2 caps but not from samples capped with ITO.
Information from electron spectra: Numerical analysis compared with high-energy resolution
Authors: Stickle W. F. , Watson D. G. , Moulder J. F.
Published: July 2002

Determination of the chemical species in the layers and interfaces of materials used in thin film technology requires the use of surface analytical techniques such as x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Identification of chemical species is sometimes accomplished by the use of high energy resolution during data acquisition, however, close overlap of peaks often requires the use of synthetic curve fitting or other numerical methods such as factor analysis or linear least squares fitting. Silicon appears in many chemical environments in semiconductor device technology: as an insulating oxide or nitride, in metallization as a silicide, or as a semiconducting substrate, for example. Using a Si3N4/SiO2/Si multilayer structure and various metal silicides as test structures, a comparison of the depth profiles obtained from high energy resolution data versus low energy resolution data combined with factor analysis and linear least squares fitting is made.
Direct imaging of monolayer and surface atomic structure by angular distribution Auger microscopy
Authors: Frank Douglas G. , Golden Teresa , Chyan Oliver M. R. , Hubbard Arthur T.
Published: July 2002

Presented here are complete angular distributions of Auger electrons emitted from Pt(111), Ag(111), Cu(100), and an adsorbed monolayer of iodine on Pt(111). These samples were chosen because there is agreement as to their surface structure, providing a foundation on which to compare the nature of the observed distributions to the structural properties of the surface. In particular, the dependence of the angular distribution on the Auger electron kinetic energy was investigated by obtaining data at more than one energy for each metal. In each case, angular distributions from crystalline samples contain intensity minima (‘‘silhouettes’’) along the internuclear directions for Auger kinetic energies <100 eV. Above 100 eV, the intensity minima are gradually replaced with maxima along directions parallel to the clearest channels through the crystal. Near grazing angles of detection, the angular distributions of 507 and 518 eV iodine Auger electrons emitted from a monolayer of iodine on Pt(111) contains intensity minima along directions corresponding to the I–I internuclear directions. These results indicate that the presence of intensity maxima or minima along the internuclear directions is not merely a function of Auger electron kinetic energy, but also depends upon the nature of the sample.
Seed cone evolution on positively charged Cu targets: Preliminary study by high-resolution electron microscopy
Authors: Mori Y. , Fujimoto Y. , Okuyama F.
Published: July 2002

The electrostatic effect on the seed cone evolution at Ar+-bombarded Cu(111) surfaces was investigated by means of high-resolution transmission electron microscopy. A simultaneous supply of Mo seeds to the target biased at positive 100–150 V was found to induce an oriented growth of nanometer thick Mo layers on the cone slopes receiving high seed fluxes. In the seed layers thus grown, Mo atoms were so arranged that Mo〈100〉 was parallel with the ion-incidence direction, suggesting that depositing Mo atoms were forcibly stacked very close to one another along the ion beam, by a strong electrostatic field generated at the growth front of seed layer. Evidence is also presented that the seed layers were grown via a particle supply process of Kossel type.
Epitaxial relations and electrical properties of low-temperature-grown CaF2 on Si(111)
Authors: Cho C.-C. , Liu H. Y. , Gnade B. E. , Kim T. S. , Nishioka Y.
Published: July 2002

The temperature dependences of crystalline quality, epitaxial relations, and interface properties of CaF2 on Si(111) are studied by x-ray diffraction and electrical measurements. While the CaF2 films grown at temperatures above 400 °C exhibit B-type epitaxy, the films grown at temperatures below 400 °C show A-type epitaxy. Using low substrate temperatures, we also obtained A-type CaF2 on SiGe(111) and off-orientated Si(111). In addition to the change in epitaxial relations, the interface state density is significantly reduced when the growth temperature of the CaF2 films decreases. Although flat capacitance–voltage (C–V) curves are observed from capacitors made of CaF2 films grown at 600–800 °C, suggesting a pinned interface, unpinned C–V characteristics are observed from capacitors made of either A- or B-type epitaxial CaF2/Si(111) grown at 200–500 °C, and polycrystalline-CaF2/Si(111) grown at 25–100 °C. The C–V characteristics are also dependent on the post-annealing temperature. Our results indicate that the interface state density of CaF2/Si(111) is dominated by thermal history, rather than crystalline quality or orientation, of the CaF2 film.
Interfacial reactions in epitaxial Al/Ti1−xAlxN (0≤x≤0.2) model diffusion-barrier structures
Authors: Petrov I. , Mojab E. , Adibi F. , Greene J. E. , Hultman L. , Sundgren J.-E.
Published: July 2002

Transmission electron microscopy (TEM), cross-sectional TEM, scanning TEM with energy dispersive x-ray analysis, and Auger electron spectroscopy were used to investigate the nature of rate-controlling interfacial reactions in epitaxial Al/Ti1−xAlxN thin-film couples. TiN and NaCl-structure Ti1−xAlxN layers, 120 nm thick, with compositions x=0.1 and 0.2 were grown on MgO(001) substrates by ultrahigh vacuum reactive magnetron cosputter deposition in N2 discharges. Epitaxial Al films, 200-nm-thick, were then grown in Ar on top of the nitride layers during the same vacuum cycle. The reaction paths for Al/TiN and Al/(Ti,Al)N interactions during anneals at Ta=600 °C for ta up to 150 min was similar, but the extent of reaction was dramatically decreased by the substitution of (Ti,Al)N barrier layers for TiN. The primary mobile species during annealing was Ti which penetrated into the Al layers and reacted to form the ordered tetragonal intermetallic phase Al3Ti while Al segregation resulted in the formation of a narrow metastable zincblende structure AlN layer at the Al/nitride interface. The room-temperature resistivity of 1-μm-thick nitride layers varied from 15 μΩ cm for TiN to 60 μΩ cm for Ti0.8Al0.2N.
Sputter distribution of a large scale ion beam coater
Authors: Albertinetti N. , Minden H. T.
Published: July 2002

TiO2 was reactively sputtered in a large ion beam system from a 8 in. diam Ti target. 32 glass samples were mounted in concentric semicircles on a 12 in. diam plate, and after sputtering the thickness of the samples was measured. In other experiments TiO2–SiO2 multilayer dielectric coatings were deposited in the same system. In these cases the samples were mounted on a planetary fixture, and thickness differences were measured across a single planet. Although the gross features of the thickness distributions could be explained by almost any reasonable sputter distribution, significant details of the thickness distribution could not. To explain these differences qualitatively, texturing of the target and scattering of the sputtered atoms by the neutral Ar atoms of the sputtering gas is postulated. These effects distort the thickness distribution in a manner which is not easily predicted by theory.
Molecular interactions on surfaces
Authors: Wei D. H. , Skelton D. C. , Kevan S. D.
Published: July 2002

The potential energy surfaces describing interactions between molecules lie at the heart of much of chemical physics. Numerous spectroscopic and scattering techniques can provide a fairly direct measure of the interactions between gaseous species. Less detailed information is available for the lateral interactions between adsorbed molecules since these must be inferred from their impact upon static, kinetic, and dynamic surface phenomena. We have recently combined measurements of the coverage-dependent isothermal molecular desorption rate and adsorption isotherms with a quasiequilibrium analysis to make progress in understanding the general features of the lateral interaction potential between similar and different adsorbed molecules. Results from a variety of systems ranging from physisorption to weak chemisorption are presented which emphasize several dominant trends. Our results for physisorption systems are generally quantitatively consistent with a lateral potential described by a simple screened gas phase potential. For chemisorption systems, however, we often find evidence for a weak attractive well in the lateral potential with no counterpart in the gas phase potential. These weak attractions have a pronounced impact upon coverage-dependent static and kinetic phenomena.
Protein–platelet and platelet–leukocyte interaction at materials in contact with human blood
Authors: Nygren Håkan , Braide Magnus , Karlsson Christin
Published: July 2002

The adhesion and activation of platelets and leukocytes at blood–material interfaces was studied by fluorescence microscopy and photometry using specific anti-CD antibodies, antiplasma protein antibodies, and the calcium probe Fura-2. Hydrophilic glass or methylized, hydrophobic glass was prepared and capillary blood was placed as droplets on the surface in a humified chamber. The adsorption of plasma proteins was monitored with FITC-labeled antibodies directed against albumin, IgG, fibrinogen, fibronectin, the v. Willebrand factor, prothrombin/thrombin, and complement factor C3c. The adhesion of platelets was shown by anti-CD 61 antibodies, specific for this cell type. Adhesion of leukocytes was measured by staining their DNA with acridine orange. Adhering platelets were found after 15 s of blood–material contact on both surfaces. The number of adhering platelets rapidly decreased at the hydrophilic surface, but remained high for more than 8 min at the hydrophobic surface. Fibrinogen was the dominating protein at the material surface, whereas fibronectin and the v. Willebrand factor were found at the cell surfaces. Platelet-derived microvesicles were found after 4 and 8 min of blood–material contact. These microvesicles showed intense staining with anti-C3c antibodies. Significant numbers of leukocytes (PMN cells) were seen after 2 h of blood–material contact. In other experiments, granulocytes were isolated and incubated with Fura-2. The supernatant of hirudin-treated blood, exposed to hydrophilic or hydrophobic glass surfaces, was added to the cells and the fluorescence was recorded after emission at 340 and 380 nm.

A rapid peak was seen, indicating calcium influx into the cytoplasm. The activating substance was removed from the supernatant by filtering it through a 0.1–0.45 μm Millipore filter. The blood samples were taken from patients undergoing treatment with extracorporeal circulation. The samples were incubated with monoclonal antibodies against surface antigens CD-11b, 16, 35, 61 and 62. The fluorescence was measured in a flow cytofluorometer. The PMN cells were shown to be activated rapidly after the onset of oxygenator circulation.
In situ production of very low density microporous polymeric foams
Authors: Falconer J. W. , Nazarov W. , Horsfield C. J.
Published: July 2002

Small, open-ended, parylene microcylinders of 400 μm diameter, 700 μm length, and 10 μm wall thickness were filled with a solution of a polyfunctional monomer of low concentration. The solution was polymerised in situ with ultraviolet light to produce a gel. Precipitation of these gels in a nonsolvent and subsequent drying by means of a critical point drying apparatus produced microcylinders filled with a low density foam. Radiographic examination of the foam gave a density of the order of 2 mg cm−3, and scanning electron microscopy micrographs showed cell sizes of the order of 1 μm. No shrinkage of the foam was observed with cylinders of the dimensions given, but with larger cylinders of diameter and length of the order of 1000 μm, some axial shrinkage was observed which resulted in cylinders with slightly concave ends (of the order of 20 μm).
Conformality of SiO2 films from tetraethoxysilane-sourced remote microwave plasma-enhanced chemical vapor deposition
Authors: Raupp Gregory B. , Levedakis Dimitri A. , Cale Timothy S.
Published: July 2002

The dependences of silicon dioxide step coverage in micron-scale trenches on substrate temperature, total pressure, absorbed microwave power, and O2:tetraethoxysilane (TEOS) flow ratio were investigated in a remote plasma configuration in which oxygen is excited upstream of the deposition chamber in a microwave glow discharge. Of the independent parameters investigated, temperature has the strongest effect on conformality. Conformality degrades modestly with decreasing pressure and increasing O2:TEOS flow ratio, but is nearly independent of absorbed microwave power. Step coverage degrades significantly with increasing temperature; for example, step coverage in a long rectangular trench of aspect ratio 2 is greater than 90% at 250 °C, but less than 40% at 400 °C at otherwise fixed conditions. We attribute this behavior to a thermally activated oxygen–atom recombination reaction on the growing silicon dioxide surface, that consumes reactive oxygen and leads to larger gradients in oxygen atom flux in the feature as temperature is increased.
Nucleation behavior in molecular beam and chemical vapor deposition of silicon on Si(111)-(7×7)
Authors: Andersohn L. , Berke Th. , Köhler U. , Voigtländer B.
Published: July 2002

The nucleation behavior during chemical vapor deposition (CVD) of silicon on Si(111)-(7×7) using disilane (Si2H6) is investigated with a scanning tunneling microscope. In the temperature range from 450 to 540 °C it is compared to molecular beam epitaxy (MBE). Whereas the latter is very well described within the framework of classical rate equation based nucleation theories in the complete condensation regime, the same approach fails for CVD growth. For MBE a critical nucleus i*=5–7 is found. Although the relationship between island density and growth rate in CVD also follows a power law as does MBE, the exponent is significantly higher than the theoretically expected value. The influence of hydrogen present on the surface during CVD growth is also discussed.
Vacuum chamber for the wiggler of the Taiwan Light Source at the Synchrotron Radiation Research Center
Authors: Wang D. J. , Chen J. R. , Hsiung G. Y. , Shyy J. G. , Huang J. R. , Hsu S. N. , Hsiao K. M. , Liu Y. C.
Published: July 2002

An aluminum vacuum chamber 3 m long and 21.5 mm high was fabricated, tested and installed in the wiggler section of the Taiwan Light Source at the Synchrotron Radiation Research Center. The chamber was made by the extrusion method and machined to a flatness of <±0.1 mm/3 m. The inner aperture included an elliptical channel (17 mm×80 mm) for electron beam and a pumping channel for a nonevaporable getter (NEG) strip. Two heat-treated Be–Cu springs were used to absorb the thermal expansion of the NEG strip during activation. After installation of the wiggler chamber in the storage ring, a pressure of 0.45 nTorr was reached after an in situ bakeout with NEG activated. The high temperature properties of the Be–Cu spring and the vacuum performance of the complete chamber have been tested. No obvious influence, due to the narrow beam aperture or limited gas conductance to the beam life time was found.
Characterization of silicon oxynitride thin films by infrared reflection absorption spectroscopy
Authors: Firon M. , Bonnelle C. , Mayeux A.
Published: July 2002

Silicon oxynitride thin films deposited by plasma enhanced chemical vapor deposition on various substrates have been characterized by infrared reflection absorption spectroscopy. Shifts of the LO Si–O vibrational band to lower wave numbers have been observed with increasing N content and also with the thickness of the films. We observe that the ratio of LO Si–O vibrational mode wave number to film thickness (υ/t) varies linearly with the ratio of refractive index to thickness (n/t). This linear relationship does not depend on the nature of substrates on which films are deposited (Al/Si, Si, Si/Al). Our results show that the composition of silicon oxynitride films could be determined directly by measuring the LO Si–O mode position.
Electrostatic scattering of ionic species in low pressure sputtering of Ti and TiN
Authors: Backhouse C. J. , Robbie K. , Parks J. , Broughton J. N. , Dew S. , Este G. , Brett M. J.
Published: July 2002

A technique of sputtering with low pressures and large substrate to target distances (long throw) has been studied with a view of applying the technique to the deposition of titanium and titanium nitride on high aspect ratio topographies. The angular distributions of the sputtered species produced by most sputtering systems are broad and therefore unsuitable for application to via filling in ultralarge scale integration or even to lift-off patterning in very-large scale integration. In our work, progressive reduction in the pressure to 0.013 Pa (0.1 m Torr) while reducing the size of the planar magnetron (to 50 mm diam), was made possible by injecting electrons and ionized Ar by means of a secondary hollow cathode source. These reductions in pressure and magnetron size have greatly narrowed the incident angular distribution of the sputtered species at the substrate. However, we believe that a component of the sputtered species is electrostatically scattered near the substrate. This is important because many of the applications of sputtering at low pressures will involve insulating substrate structures that are expected to be particularly susceptible to this effect (for instance lift-off deposition on, or via filling in, insulators). In addition, we believe that our findings will be applicable to several related deposition techniques of current interest in the literature such as electron cyclotron resonance, ionized sputtering (i.e., ionizing the sputtered flux and directing it towards the substrate) and conventional magnetron sputtering.
Investigation of deep levels in ZnSe:Cl films grown by molecular beam epitaxy
Authors: Hernández L. , de Melo O. , Meléndez-Lira M. , Rivera-Alvarez Z. , Hernández-Calderón I.
Published: July 2002

Using ZnCl2 as a doping source, we have grown epitaxial layers of Cl-doped ZnSe onto GaAs(100) substrates at a temperature of 285 °C by molecular beam epitaxy. The carrier concentration was controlled by the ZnCl2 source temperature. The maximum carrier concentration obtained was 1.2×1019 cm−3 with a resistivity of 2.7×10−3 Ω cm. Higher doses of Cl atoms tend to decrease free carrier concentration and introduce additional defects; this effect was consistent with an increase of deep-level photoluminescence emission. From deep-level transient spectroscopy measurements we determined the presence of four traps with energy levels Ec around 0.50, 0.68, 0.74, and 1.20 eV. The last three traps have not been previously reported. One of them, Ec∼0.74 eV, presents a clear dependence with Cl concentration and thus can affect the performance of ZnSe:Cl-based devices. The microscopic nature of these traps is discussed in terms of Zn vacancies (VZn) and VZn–Cl complexes.
Surface-extended x-ray absorption fine structure study of silicon deposited onto GaAs(110)
Authors: Hasnaoui M. L. , Flank A. M. , Pompa M. , Lagarde P.
Published: July 2002

The system Si/GaAs(110) was studied by surface extended x-ray absorption fine structure at the silicon K edge, starting from a 0.5 monolayer (ML) coverage up to 3 ML. At very low coverages, the first adsorption site of the silicon has been determined to be above the center of the triangle formed by two arsenic and one gallium surface atoms. The growth mode of silicon on this surface obeys a modified version of the Stranski–Krastanov model: the formation of three-dimensional clusters appears at 2.5 ML and involves all the deposited silicon atoms.
Cleaning thin-film diamond surfaces for device fabrication: An Auger electron spectroscopic study
Authors: Baral Bhaswar , Chan Simon S. M. , Jackman Richard B.
Published: July 2002

Auger electron spectroscopy was used to analyze polycrystalline thin-film diamond surfaces following the use of differing methods for the removal of unwanted nondiamond carbon. Exposing the film to a hydrogen plasma at the termination of the growth process is effective for producing a surface that gives an Auger spectrum typical of diamond with little contamination. Strongly oxidizing solutions involving sulfuric acid generate low concentrations of surface sulfur together with an oxide phase. However, in the case of an ammonium persulfate–sulfuric acid etchant solution, the Auger features associated with the diamond more closely resemble those of single crystal material suggesting that this treatment may offer better performance when used during the fabrication of thin-film diamond electronic devices.
Surface topography development on ion-beam-sputtered surfaces: Role of surface inhomogeneity induced by ion-beam bombardment
Authors: Moon Dae Won , Kim Kyung Joong
Published: July 2002

To understand the deterioration of the interface resolution in sputter depth profiling and the surface roughness development in semiconductor and thin-film processings, the chemical states of constituents of ion-bombarded surfaces were analyzed by in situ x-ray photoelectron spectroscopy (XPS) measurement under various ion-beam bombardment conditions. The XPS results were compared with secondary-ion-mass spectrometry (SIMS) depth profiling results and surface topographic developments observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) for a Cr/Ni multilayered thin-film structure and a GaAs/AlAs superlattice under various incidence angles and the primary ion species. SEM and AFM measurements showed that the deterioration of the interface resolution was determined mainly by surface topographic development which is very sensitive to the ion incidence angle and the primary ion species. With changing the incidence angle from the surface normal to 80° and the primary ion species between Ar+ and O+2 systematically, the effects of the ion incidence angle and the ion species on the chemical states of constituents, the depth resolution in SIMS depth profiling, and the surface topographic developments were studied by in situ XPS, SIMS, SEM, and AFM, respectively. From the systematic studies on ion-beam-bombarded surfaces of Ni, Cr, GaAs, AlAs, Si, and SrTiO3 under various ion bombardment conditions, it could be concluded that the surface inhomogeneity introduced by ion-beam bombardment is one of the most important factors that determine the surface topographic development on ion-bombarded surfaces.
Dry development of sub-0.25 μm features patterned with 193 nm silylation resist
Authors: Palmateer S. C. , Forte A. R. , Kunz R. R. , Horn M. W.
Published: July 2002

The dry development of sub-0.25 μm silylated resist features patterned at 193 nm was optimized in an oxygen plasma using a high-ion-density plasma etcher. Low pressure and low wafer temperature eliminate lateral resist loss, resulting in vertical profiles, linewidth fidelity, and large process latitudes for 0.175 μm silylated resist features.
Stabilization of CF4 plasma treated carbon surface by heat treated during and after plasma treatment
Authors: Izumi Yori , Kamata Kiichiro , Katoh Masaaki , Ohte Takeo , Kojima Akira
Published: July 2002

Stabilization of CF4 plasma treated carbon surface by heat treated during and after plasma treatment has been successfully achieved. Carbon surface was altered to hydrophobic by adsorbed fluorine (F) atoms during CF4 plasma treatment. F atoms desorbed from carbon surface after plasma treatment caused time dependent change of the carbon surface properties. The change was stopped by heating during plasma treatment because simultaneous heat and plasma treatment make the F atom bonds stable. However, heat treatment may diminish the merits of the plasma treatment such as low-temperature and damage-free treatment. Heat treatment during and after plasma treatment enabled to stabilize the F atom bonds of the carbon surface in spite of the lower temperature and to reduce the surface damage. Surfaces properties unchanged over 70 days and the degree of damage was almost the same as the one on the surface with plasma treatment only.
Microstructure and bulk reactivity of the nonevaporable getter Zr57V36Fe7
Authors: Günter M. M. , Herein D. , Schumacher R. , Weinberg G. , Schlögl R.
Published: July 2002

We report on a structural investigation of the zirconium-based ternary alloy getter “St 707” (from SAES Getters, Milan, Italy) based on in situ x-ray diffraction (XRD) measurements at high temperature in inert gas atmosphere accompanied by scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDX) and thermal analysis by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) investigations. The XRD together with SEM-EDX confirms that the getter is biphasic before as well as after activation. Hexagonal Zr and the cubic Laves phase Zr(V1−xFex)2 with a narrow compositional range (0.16⩽×⩽0.18) coexist in this material. Upon heating, the in situ XRD shows a gradual decrease in the crystallinity of the Laves phase, which is attributed to its disintegration into small particles. DSC measurements under moist Ar exhibit an exothermic irreversible transition at ≈ 675 K which is associated with chemical bulk reactions and indicative of the gettering process. The operation of the gettering process during activation was verified by TGA measurements. It is concluded that the gettering process is correlated with the disintegration of the Laves phase. The sorption kinetics of water vapor were studied at 355 K over a pressure range of 101–102 Pa using a barometric technique. A change in the rate determining step is detected from an initial diffusion-controlled step to surface adsorption after some sorption cycles.
Tritiated amorphous silicon films and devices
Authors: Kosteski T. , Kherani N. P. , Gaspari F. , Zukotynski S. , Shmayda W. T.
Published: July 2002

The dc saddle-field glow discharge system was used to stably bond tritium in hydrogenated amorphous silicon films. A betavoltaic battery is demonstrated using tritiated-hydrogenated amorphous silicon as the intrinsic layer in a p–i–n diode and betaconductivity was observed in a-Si:H:T films. Although the half-life of tritium is 12.5 years, the decay of tritium appeared to rapidly increase the midgap density of states which decreased the excess carrier lifetime and decreased the power from the betavoltaic battery. The betaconductivity properties of the a-Si:H:T film were also affected.
Semiquantitative subplantation model for low energy ion interactions with solid surfaces. III. Ion beam homoepitaxy of Si
Authors: Boyd K. J. , Marton D. , Rabalais J. W. , Uhlmann S. , Frauenheim Th.
Published: July 2002

The semiquantitative subplantation model developed in article I [K. J. Boyd, D. Marton, J. W. Rabalais, S. Uhlmann, and Th. Frauenheim, J. Vac. Sci. Technol. A 16, 444 (1998)] is used to describe the homoepitaxial growth of Si{100} films by low energy ion beam deposition. The model successfully describes the epitaxial quality of films grown at a variety of ion energies and substrate temperatures. Density functional molecular dynamics simulations are used to calculate threshold energies and cross sections for penetration of ions into the target lattice. These calculated values, used in conjunction with the model, yield good agreement with recently published experimental data for homoepitaxy by direct deposition of low energy Si+ ions. The model also provides a simple qualitative explanation of the limiting epitaxial thickness in molecular beam epitaxy and the success of epitaxial Si deposition by other hyperthermal particle methods. New insight into the atomic-level behavior of epitaxial film growth from hyperthermal particles is obtained from these applications.
Characterization of diamond phase in thin carbon films grown by laser ablation
Authors: Jayatissa Ahalapitiya Hewage , Saito Nobuo , Sato Fumio , Takizawa Kuniharu
Published: July 2002

Carbon films grown by KrF and ArF laser ablation of graphite were characterized by means of Raman and reflection high energy electron diffraction (RHEED) spectroscopies. Though Raman spectra of these films show only a weak characteristic peak of diamond, the existence of the diamond phase could be confirmed by RHEED measurements. It was found that the ArF laser grown films possess a trace of diamond phase or that these films at the threshold conditions for crystallization.