bluuebunny/crossref_metadata_2025 huggingface dataset:
Sealing technique for aluminum to stainless steel CF flange pairs
Authors: Ishigaki T. , Shibuya K. , Sakaue H. , Be S. H.
Published: July 2002

Ultrahigh vacuum sealing technology has been developed for joining aluminum (Al) and stainless steel (SS) CF flange pairs, which provides a leak rate of less than 2×10−11 Torr ℓ/s following a bakeout at 150 °C and return to room temperature. Sealing was achieved, in spite of the fact that the coefficient of linear thermal expansion of Al is about 1.5 times that of SS. It is assumed that the knife edges on the CF flanges changed diameters during bakeout without sliding of the knife edges with respect to the seal. This requires that the gasket assume the shape of a truncated cone. Sealing is retained during this process. This assumption was verified by three methods: (1) observing the transformation of the gasket from flat at 20 °C to conical during bakeout at 150 °C; (2) measuring the leak rate of CF 114, 203, 253, and 305 sealed flange pairs over the range from 20 °C to 150 °C, and; (3) inspecting the imprint of the knife edge of a CF 305 in the gasket after bakeout by profilometer trace and photographic examination of a section. The results showed that during bakeout, the shape of the gasket changed, accommodating the differential motion, and thus preventing damage to the seal at the knife edge/gasket interface.
Analysis of oxide film on stainless steel via position-sensitive atom probe
Authors: Yoshimura Toshihiko , Ishikawa Yuichi , Ohkido Shinobu
Published: July 2002

Thermal oxide films formed on the surface of a type 316 stainless steel were atomically characterized by a recently built position-sensitive atom probe (POSAP). Oxidation on the clean field evaporated surface was performed at temperatures of 350 °C for 5 min, 475 °C for 1, 5, and 15 min, and 600 °C for 5 min in oxygen at a pressure of 10−4 Torr. The POSAP analysis has clarified that the oxide–steel interfaces at 350 °C for 5 min, and 475 °C for 1 and 5 min are very sharp, while the interfaces at 475 °C for 15 min and 600 °C for 5 min have subnanometer level roughness. In spite of the difference in oxidation temperature and time, the oxygen concentration in the oxide films is in the range from 35 to 50%, and Ni and Mo tend to segregate to the oxide–steel interface. Furthermore at 475 °C for 15 min and at 600 °C for 5 min, Ni and Mo segregate to the top surface region as well as to the interface. The oxide film has a triplex structure consisting of the top surface region being chromium rich oxide, the inner region being iron rich oxide, and the interface being chromium rich oxide. The Mo segregation is localized in a few nanometers in size and appears to inhibit the oxide formation in those segregated regions.
Some important developments in capture pumping technology in the last 40 years
Authors: Welch Kimo M.
Published: July 2002

Highlights of the history of capture pumping technology are given. The subjects covered include some of the important chronological developments in sputter-ion, electrostatic-ion, sublimation, nonevaporable getter, and cryogenic pumping in the last 40 years. All of these forms of pumps proved to be essential tools for the attainment of ultrahigh vacuum.
Silicon shot gas epitaxy: Dose-controlled digital epitaxy
Authors: Kim K.-J. , Suemitsu M. , Miyamoto N.
Published: July 2002

We have developed a new method of silicon digital epitaxy, shot gas epitaxy, in which the dose of the source gas molecules per pulse, (shot), is easily controlled by charging and emptying a gas-charge cell. What distinguishes this method from conventional atomic layer epitaxy, lies in its ability to vary the grown thickness per cycle. The grown film thickness per cycle is highly temperature dependent below 750 °C while it is temperature independent above it. The unit thickness in the latter region is also predicted to be varied by changing the dose per pulse from the similarity of the growth mode to that of gas-source molecular beam epitaxy.
Heteroepitaxial growth of Si on GaP and GaAs surfaces by remote, plasma enhanced chemical vapor deposition
Authors: Habermehl S. , Dietz N. , Lu Z. , Bachmann K. J. , Lucovsky G.
Published: July 2002

Heteroepitaxial thin films of Si have been deposited onto GaP and GaAs substrates at low temperatures, <400 °C, by remote plasma-enhanced chemical vapor deposition. Cleaning and passivation of the GaP and GaAs surfaces, by ex situ wet chemistry, and in situ exposure to atomic-H at temperatures from 400 to 530 °C, were found to be critical in promoting epitaxial growth. The exposure to atomic-H was effective in removing surface oxides and hydrocarbon contamination. After the H-exposure, low energy electron diffraction (LEED) measurements revealed an ordered 1×1 structure for the GaP(111) surface, and a c(8×2)Ga structure for the GaAs(100) surface. Heteroepitaxial films of Si have been deposited at temperatures from 300 to 400 °C and pressures between 50 and 500 mTorr, with the highest quality epitaxial growth proceeding on vicinal GaP(100) surfaces. In contrast, for the growth of Si on GaP(111) and GaAs(100) surfaces, LEED measurements indicate the onset of strain-induced disorder within the first few monolayers of the Si overgrowth.
Scanning tunneling microscopy study of the faceting dynamics of stepped Ag(110) upon oxygen exposure
Authors: Ozcomert J. S. , Pai W. W. , Bartelt N. C. , Reutt-Robey J. E.
Published: July 2002

The dynamics of the room temperature faceting of Ag(110) upon exposure to oxygen has been studied using scanning tunneling microscopy (STM). Vicinal surfaces are exposed to oxygen while STM images are continuously collected. The surfaces are observed to break up into regions of high step density (‘‘step bunches’’) and (110) facets. This faceting is driven thermodynamically by the formation of an n×1 oxygen overlayer on the (110) facet, in which rows of oxygen atoms form along the next-nearest neighbor [001] direction. The dynamics of this breakup are found to depend sensitively on the step-edge orientation of the original clean vicinal surface. The reversibility, and thus probable thermodynamic origin, of the faceting is demonstrated by removal of the oxygen through chemical reaction with CO.
Growth of thin Ti films on W(110) and O/W(110)
Authors: Herman G. S. , Peden C. H. F.
Published: July 2002

The interaction of ultrathin Ti films grown on clean and oxidized W(110) has been studied by Auger electron spectroscopy and thermal desorption. Auger electron spectroscopy indicates layer-by-layer growth of Ti on both of these substrates. For annealing temperatures up to 1100 K, two-monolayer Ti films are stable on the clean and oxidized W surfaces. Above these coverages, the films are unstable after annealing to 1100 K, although this temperature is lower than Ti desorption. Diffusion of oxygen to the Ti surface is also observed for the oxidized surface. Thermal desorption data show distinct Ti monolayer and multilayer features for Ti from the clean surface at coverages greater than one monolayer. A more complex desorption behavior is observed for Ti on the oxidized surface.
Investigations into the chemistry of perfluorodiethoxymethane at nickel and nickel oxide surfaces
Authors: Jenks Cynthia J. , Jacobson Joyce A. , Thiel Patricia A.
Published: July 2002

We describe the surface chemistry of a low-molecular-weight perfluoroether with an acetal (–O–CF2–O–) unit. The acetal unit has been proposed by others as the critical moiety responsible for the decomposition of linear perfluoropolyethers at metal surfaces. Three nickel surfaces are studied, clean Ni(100), Ni(100) c(2×2)–O, and NiO(100). The experimental techniques are temperature-programmed desorption and high-resolution electron energy loss spectroscopy. Our work shows that even when a perfluoroether containing an acetal unit is used, in this case perfluorodiethoxymethane, decomposition is not apparent on any of the surfaces studied under typical ultrahigh vacuum conditions.
Electrical properties of radio frequency magnetron-sputtered (BaSr)TiO3 thin films on indium tin oxide-coated glass substrate
Authors: Kim Tae Song , Kim Chong Hee , Oh Myung Hwan
Published: July 2002

(BaSr)TiO3 thin films were deposited on an indium tin oxide (ITO)-coated glass substrate at the different substrate temperature of 350, 450, and 550 °C by means of rf magnetron sputtering method. The dependency of dielectric constant (ε′) and loss (tan δ) of (BaSr)TiO3 thin films as a function of frequency (0.3–1000 kHz) was studied. It was observed that there was a possibility for the oxidation of the ITO layer to be one of the causes of dielectric anomalies around 100 kHz. Dielectric constant and tan δ became larger with the increase of deposition temperature. As the deposition temperature increases, the leakage current also increases and the breakdown field decreases from 2.5 to 1.97 MV/cm. These variations of electrical properties can be clearly explained by the increase of mobile carrier-oxygen vacancy-in (BaSr)TiO3 thin films.
CaF2 overlayers to preserve the ideal termination of Sb/GaAs(110)
Authors: Green A. M. , Spicer W. E. , Kim C. , Cao R. , Pianetta P.
Published: July 2002

Photoemission spectroscopy has been performed on CaF2 overlayers on as cleaved (‘‘bare’’) GaAs(110) and GaAs(110) terminated with 1 monolayer of Sb. We observe Fermi-level positions of 0.7 and 0.9 eV above the valence-band maximum on n type for the bare and Sb terminated surfaces, respectively. On p type, we observe close to flatbands for both surfaces. These Fermi-level positions are 0.45 eV on n type and 0.8 eV on p type, below previous reports for CaF2 on the bare surface. We obtain positions close to the previous results by exposing the sample to a flux of UV photons. Upward Fermi-level movement is observed on n and p type for both surfaces. Several complimentary experiments will be discussed which indicate that the observed Fermi-level movement is not due to surface charging. We present a possible interpretation of the data which involves a low density of interface states created by the CaF2deposition and the formation of F centers when the sample is exposed to UV radiation. Analysis of core-level line shapes suggests the presence of Ga–F bonding for CaF2 on the bare surface. We present results which indicate that the ideal Sb termination is preserved for CaF2 on Sb terminated GaAs and evidence of CaF2–Sb bonding will be discussed.
Free-electron laser spectroscopy of semiconductors and interfaces
Authors: McKinley J. T. , Albridge R. G. , Barnes A. V. , Chen G. C. , Davidson J. L. , Languell M. L. , Polavarapu P. L. , Smith J. F. , Yang X. , Ueda A. , Tolk N. , Coluzza C. , Baudat P. A. , Dupuy C. , Gozzo F. , Iilegems M. , Martin D. , Morier-Genoud F. , Rudra A. , Tuncel E. , Margaritondo G.
Published: July 2002

The broad tunability (1–10 μm) and megawatt regime peak intensity available from the Vanderbilt Free-Electron Laser is opening new avenues in semiconductor research. Initial experiments in nonlinear optical absorption and heterojunction band-edge discontinuity measurements are discussed in order to illustrate the flexibility of the free-electron laser as a research tool.
Quantitative x-ray photoelectron spectroscopy of CuAu, CoNi, and CuNi alloys using theoretical photoionization cross sections or reference spectra
Authors: Jansson C. , Tougaard S.
Published: July 2002

In this paper we have studied the extent to which the accuracy of quantitative analysis by x-ray photoelectron spectroscopy is affected by neglect of the shake-up electrons. Three sets of alloys (CuAu, CoNi, and CuNi) were studied. It was found that the accuracy of quantification from first principles based on the intensity in a narrow energy range around the peak energy can lead to errors of up to 114%. The error is discussed in terms of the importance of shake-up effects. When reference spectra are applied, these effects are reduced and the Shirley method for background estimation then yields compositions for the considered alloys that differ by between 2% and 22% from those determined with an algorithm that is based on a physical description of the inelastically scattered electrons. However if, as found for CuAu, the shake-up in the reference sample is strongly different from that of the alloy, it may be less accurate to use reference spectra with the Shirley method.
Metal overlayers on organic functional groups of self-organized molecular assemblies. III. X-ray photoelectron spectroscopy of Cr/CN on 12-mercaptododecanenitrile and of Cr/CH3 on octadecanethiol at sample temperatures from 173 to 373 K
Authors: Jung D. R. , Czanderna A. W.
Published: July 2002

The dependence on substrate temperature of the formation of Cr(CN) complexes and Cr-carbides when Cr overlayers are deposited onto organized molecular assemblies (OMAs) has been investigated in situ by x-ray photoelectron spectroscopy (XPS). At Cr coverages of 6 Å or less, evidence for the formation of a Cr(CN) complex with the CN end groups of the 12-mercaptododecanenitrile OMA is found in negative binding energy shifts of the nitrile part of the C 1s line shape and of the N 1s core level. The N 1s negative binding energy shift increases from 0.1–1.2 eV for substrate temperatures from 173 to 373 K.  At a Cr coverage of 6 Å, Cr-carbide was observed to form to a similar extent on the 12-mercaptododecanenitrile and octadecanethiol OMAs. The number of carbide C atoms per OMA chain increases from 0.7 to 3 for substrate temperatures from 173 to 373 K for 6 Å Cr on the 12-mercaptododecanenitrile OMA. Greater amounts of carbide result when the Cr is deposited onto a sample at a given temperature, T, than when the deposition at a lower temperature is followed by warming to T. We interpret the increased amount of carbide to result from a contribution of the incident Cr atom kinetic energy to the activation of the Cr-carbide reaction. Collateral effects of x-ray exposure and substrate temperatures greater than 295 K may have affected, in part, the observed binding energy shifts and peak heights, but do not compromise the general conclusions of our interpretation.
Characterization of diamondlike carbon films grown by super-wide electron-cyclotron resonance plasma assisted chemical vapor deposition
Authors: Ishii A. , Amadatsu S. , Minomo S. , Taniguchi M. , Sugiyo M. , Kobayashi T.
Published: July 2002

An electron-cyclotron resonance plasma source that generates 500 mm wide plasma has been developed. The plasma is generated by a 2.45 GHz traveling microwave which is supplied through a long slot antenna prepared in the waveguide in a divergent magnetic field generated by permanent magnets and a solenoid coil. Diamondlike carbon (DLC) films were deposited in a wide zone 320 mm in width. The breakdown field was 8.4×106 V/cm and permittivity, 3.89. The prepared Al/DLC/Si metal/insulator/semiconductor diode revealed fairly good field effect in its capacitance–voltage curve.
Preliminary soft x-ray studies of β-SiC
Authors: Shek M. L. , Miyano K. E. , Dong Q.-Y. , Callcott T. A. , Ederer D. L.
Published: July 2002

We have looked at β-SiC with soft x-ray emission and photoemission spectroscopy. From the Si L23 and C K emissions, the Si s+d-like and C p partial density of states in the bulk valence band are identified and compared with valence band photoemission. In addition to bulk electronic structural features, photoemission from a (3×2) Si-rich surface shows two surface-derived valence features at ∼−2.6 and ∼−1.6 eV relative to the Fermi level. The intensities of these valence features vary as those of surface Si 2p core level components shifted by −0.5 and −1.4 eV from the bulklike SiC Si 2p core level. We have also used the Si L23 absorption edge as a probe of the unfilled states near the conduction band minimum.
Real-time observation of ultrathin silicon oxide film growth using rapid ellipsometry
Authors: Kuroki H. , Nakamura K. G. , Kamioka I. , Kawabe T. , Kitajima M.
Published: July 2002

We have studied plasma oxidation of silicon by a radio frequency discharge using rapid ellipsometry. The change rate of the ellipsometric parameter Δ immediately after starting the discharge increases as the plasma density increases. An anomalous time dependence of the optical phase shift (Δ) is observed in the initial stage of silicon surface oxidation, and the behavior is explained based on a model calculation, which considers a change in refractive index during silicon oxide film growth. The effect of silicon wafer surface orientation on the oxidation rate in the plasma oxidation has been also investigated. The result shows that the plasma oxidation rate on Si(111) is larger than that on Si(100).
Inert gases in sputtered tungsten: A test of predictive capability
Authors: Hoffman D. W. , Park J.-S. , Morley T. S.
Published: July 2002

The validity of two previously formulated general expressions for the number and energy of fast neutrals backscattered from sputtering targets is tested by predicting the concentrations of inert gases embedded in sputter-deposited tungsten. Test samples were prepared by ion beam sputtering with neon, argon, krypton, and xenon at 0.6 and 1.2 keV. Gas contents in the deposited films were measured by electron microprobe analysis. The predictions correctly emulate the observed order-of-magnitude differences in embedded concentrations among the four gases, and achieve quantitative agreement with no adjustable parameters in the case of argon. The predictions also correctly forecast the observed effects of increasing primary ion energy, which increases the embedded concentrations of krypton and argon, but decreases the concentration of neon. At the high concentrations of neon (≥10 at. %), a correction for preferential resputtering enters the analysis, which enables reasonable agreement to be achieved simultaneously for neon and argon. The concentrations of krypton and xenon are at or below the limit of detection but agree with prediction at that level. The observation of a strong and linear dependence of resistivity on embedded gas concentration anticipates the future capability to predict this and other properties for any metal, sputtering gas, and acceleration of interest using the general expressions for fast neutrals validated in this investigation.
Interfacial reactions of ion beam deposited a-C films on ZnS
Authors: Bruce T. , Huang L. J. , Bello I. , Lau W. M. , Panchhi P. , Strnad V. , High M.
Published: July 2002

The interfacial reactions between ion beam deposited diamondlike carbon (DLC) films on ZnS were studied by x-ray photoelectron spectroscopy. The DLC films were deposited by pure C+ ion bombardment. The results were also compared with those obtained from ion beam deposited DLC on Ge. It was found that the films (2–20 nm thick) deposited with a pure C+ beam in the energy range of 20–300 eV on these two substrates always showed two carbon phases with a C 1 s binding energy difference of about 0.8 eV. The low binding energy carbon phase showed an average location among about 30 samples at about 284.4±0.2 eV whereas the high binding energy carbon phase showed it at 285.5±0.2 eV. Although carbon in a carbide form typically has C 1s binding energy about 1 eV lower than that in graphite (284.7 eV), the observed difference of 0.9 eV in binding energies of the two carbon phases was not a consequence of one phase being metal carbide. Instead, the presence of these two phases appears to be characteristic of the DLC formed in this study. When the carbon in the overlayer was partly sputtered off and partly driven into the substrate by Ar+ bombardment, a carbide phase emerged with a binding energy of less than 283.8 eV for the germanium case whereas no C 1s peak shift was observed in the ZnS case. Further, C/ZnS samples before and after the Ar+ bombardments showed Zn 3p and S 2p data not significantly different from those of ZnS without DLC deposition. Hence, when carbon atoms were anchored into ZnS by ion bombardment, any chemical bonds between the incorporated carbon atoms and the atoms in the substrate were much weaker than those in Ge. Adhesion tests indicated that 20 nm diamondlike films deposited on ZnS by C+ ion bombardment passed the conventional tape test and eraser-rubbing test, and those by carbon evaporation failed the tests. However, thick films deposited by ion plating adhered poorly on ZnS but very well on Ge.
Role of residual casting solvent in determining the lithographic and dissolution behavior of poly(methylmethacrylate)
Authors: Criss R. , Cunningham A. J.
Published: July 2002

The effect of the pre-exposure bake and the choice of casting solvent on the sensitivity and contrast of poly (methylmethacrylate) (PMMA) has been documented to an extent not previously reported in the literature. Films baked at temperatures below Tg (the temperature which marks the onset of long-range, coordinated molecular motion), exhibited improved sensitivity and poorer contrast when compared to those baked above Tg. Dissolution rates and relative concentrations of casting solvents remaining in the films were also measured. Cross-correlation of these results with energy deposition calculations indicate that the pre-bake temperature more strongly correlates with the observed improvement in sensitivity than the presence of residual casting solvent.
Field desorption of lithium fluoride
Authors: Stintz A. , Panitz J. A.
Published: July 2002

Layers of lithium fluoride (LiF), ∼10 nm thick, were field desorbed from iridium substrates at temperatures between 25 and 600 °C. The electric field was increased until desorption of the salt layer occurred. Combined mass spectroscopy and field desorption microscopy characterized the desorption process. During desorption, ions of the form (LiF)n⋅Li+, n=1–4 are created. The field strength required for desorption is higher at lower temperatures and decreases as the temperature of the substrate is increased. Evidence for a piecewise removal of the LiF layer is presented. For thick salt layers, Li+ ions are frequently detected. An ion production mechanism based on ionic conduction of a salt layer in a high electric field is presented.
Positive and negative direct current bias effects on the microstructures and physical properties of hydrogenated amorphous carbon films prepared by radio frequency plasma chemical vapor deposition
Authors: Nakayama Masatoshi , Tsuyoshi Atsuhiro , Shibahara Masanori , Maruyama Kazunori , Kamata Kiichiro
Published: July 2002

Positive and negative direct current (dc) bias effects were investigated for the synthesis of hydrogenated amorphous carbon films in radio frequency plasma chemical vapor deposition at 0.025 Torr and 200 °C. The applied bias ranged from +250 to −500 V. Both the positive and negative dc bias effects are discussed on the basis of surface and cross-sectional morphology by scanning electron microscopy, deposition rate, threshold energy for photoelectron emission, contact angle, and adhesive strength of these films. For a negative bias, the surface of the film is very flat. The surface of the film deposited with no bias is somewhat pebbly while that of the film deposited with a positive bias is very rough and shows the presence of pores in the cross section. A negative bias substantially increases the deposition rate, refractive index, wettability, and adhesive strength. With no bias (ground potential), as compared to with a positive bias, there is a little increase in the wettability and adhesive force. The no bias case did not affect the properties arising from structural change, such as refractive index (density) and threshold energy for photoelectron emission (incorporated hydrogen). A positive bias did not affect these physical properties of the hydrogenated amorphous carbon films. These positive, negative, and no bias effects depend on the kinds of collision species and their collision energy against the substrate in the radio frequency plasma according to the additional bias conditions.
Low pressure chemical vapor deposition of InSb using neopentylstibine and trimethylindium
Authors: Bu Y. , Lin M. C. , Berry A. D. , Hendershot D. G.
Published: July 2002

Low pressure chemical vapor deposition of InSb using neo-pentylstibine and trimethylindium has been studied with x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy, Raman spectroscopy, and scanning electron microscopy (SEM). At 600 K, the InSb film with an In:Sb atomic ratio of 1 and a growth rate of ∼2 Å/min was formed on GaAs(110). The binding energies of the In and Sb 3d5/2 XPS peaks are in excellent agreement with those taken from InSb single crystal and amorphous samples. The He(II) ultraviolet photoelectron spectrum also agrees reasonably well with photoemission spectra taken from InSb using different photon beam sources. The corresponding Raman spectrum showed two phonon peaks at 179 (TO) and 190 (LO) cm−1, respectively, which are virtually identical to the Raman data reported for InSb single crystal samples. The XPS measurements suggested a three-dimensional growth mechanism for the InSb film on GaAs(110), which was confirmed by the SEM measurement. However, at ∼800 Å thickness, the SEM picture showed a very smooth InSb film, with the presence of some uncovered holes corresponding to ∼3% of the total surface area. The substrate temperature effect on the film growth was also investigated. At temperatures below 400 K, film growth was very slow and the decomposition of NpSbH2 and TMIn seemed to be incomplete, whereas above 800 K, metal droplets were clearly visible by SEM. The optimal growth temperature lies at approximately 600–700 K.
Crystal orientation control of YBa2Cu3Oy thin films on MgO prepared by excimer laser ablation with CO2 laser irradiation
Authors: Inayoshi Muneto , Hiramatsu Mineo , Sugiura Yoshiaki , Kawamura Hideaki , Nawata Masahito
Published: July 2002

Superconducting YBa2Cu3Oy (YBCO) thin films were prepared on a MgO (100) substrate by XeCl excimer laser ablation with CO2 laser irradiation. Control experiments of crystal orientation of YBCO thin films were carried out by varying the substrate temperature during deposition; c-axis oriented YBCO film, a-axis oriented YBCO film, and a-axis oriented YBCO film on the c-axis were obtained on the MgO (100) substrates. a-axis oriented YBCO films normal to the MgO (100) substrate were fabricated using the modified self-template method.
Adsorption of β-radioactive 8Li on single crystal surfaces: Thermal desorption spectroscopy and nuclear magnetic resonance experiments
Authors: Detje M. , Röckelein M. , Preyss W. , Ebinger H.-D. , Jänsch H. J. , Reich H. , Veith R. , Widdra W. , Fick D.
Published: July 2002

Experiments with β-radioactive 8Li atoms adsorbed on clean and oxygen covered W(110) and Ru(0001) surfaces are presented. The detection of the decay electrons allows experiments with adsorbates at extremely low coverages (10−5 monolayers). Nuclear spin relaxation and nuclear magnetic resonance experiments are described beside radiation detected thermal desorption spectroscopy (TDS), a new version of TDS experiments.
Simple method for Fe+ ion production in a microwave ion source
Authors: Matsuo Takahide , Miyake Kiyoshi
Published: July 2002

A simple method for Fe+ ion production in a microwave ion source has been developed by making use of the plasma chemical reaction of hematite (Fe2O3) powder with a chemically reactive CCl4 discharge plasma. A stable 56Fe+ ion intensity of over 1.3 mA was obtained when the ion source was installed in our 30 keV ion implanter. This was accompanied by an intense chlorine beam (Cl+), but the intensities of oxygen ions (O+,O+2) and carbon ion (C+) were very small despite the fact that these elements (C and O) are major constituents of CCl4 and Fe2O3. Traces of water vapor residue in the ion source enhanced the production of HCl+ ions and suppressed the yield of Fe+ ion production.
Preparation of Al–Ni alloy films by alternate sputter deposition
Authors: Ho J.-K. , Lin K.-L.
Published: July 2002

Al-Ni alloy films with an Al to Ni atomic ratio greater than 0.79 were prepared via an alternate sputter deposition technique. The formation of the alloy films was attributed to the interdiffusion and reaction between Al and Ni atoms by the adatom substitution. The crystal structures are all in accordance with the equilibrium phase diagram when the Al to Ni atomic ratio is greater than 2.30. The film with Al to Ni atomic ratio 2.30 is composed of Ni2Al3 and NiAl. A complete NiAl film was obtained when the Al to Ni atomic ratio is less than 1.53. The crystal structure of the film was reverted to Ni–Al equilibrium phases when the −100 V substrate bias was applied during deposition. The films with a NiAl structure showed 〈100〉 and 〈110〉 preferred orientations on the Si and glass substrates, respectively, disregarding the application of bias. The application of substrate bias significantly reduced the O and N contents and prevented the Al from oxidization. However, bias caused an incorporation of Ar and a lowering of Al content in the films was also observed. The decrease in Al content by the application of bias was attributed to the easier sublimation of Al adatoms from the surface than that from the Ni adatoms.
Magnetic, microstructural, and compositional characterization of Fe–N thin films for recording sensor applications
Authors: Kim Y. K. , Narayan P. B.
Published: July 2002

The dependence of microstructural characteristics and magnetic properties on the processing conditions of reactively dc magnetron sputter-deposited Fe–N films (≤1000 Å) was investigated for advanced recording sensor applications. The N content of the film increases linearly as the ratio of N2 to Ar flow rate increases. Magnetic properties could be significantly modified by the incorporation of N into the Fe matrix. A N-content range was discovered where desirable soft magnetic properties such as low coercivity and low magnetostriction could be achieved. The soft magnetic properties originated from the amorphous microstructure as evidenced by transmission electron microscopy and x-ray diffraction. The electrical resistivity of Fe–N films with soft magnetic properties was an order of magnitude higher than that of pure Fe or NiFe thin films with comparable thickness.
Measurement of the amount of oxygen generated by quartz source walls in a SF6 dense plasma: Application to a helicon reactor
Authors: Petri R. , Sadeghi N. , Henry D.
Published: July 2002

The amount of oxygen generated in a SF6 dense plasma by the etching of the quartz tube walls surrounding the plasma source of the helicon reactor has been measured. Two complementary techniques have been used to identify the wall etch products and the measurement of their equivalent flux: plasma induced emission spectroscopy of oxygen atoms (actinometry) and mass spectrometry by comparison with the amount of the isotopic oxygen (18O2) introduced into the plasma. It appears that, with a 5 mm air gap between the antenna and quartz walls of the reactor, the equivalent oxygen outgassing flux ranges from 2 to 4 sccm, depending on the SF6 pressure and the radio frequency power applied. This corresponds to an oxygen concentration in the gas phase between 15% and 40%, depending on the operating conditions. This result should be considered for the development of future dense plasma reactors using quartz walls and for improvement of the performance of the present generation of inductively coupled and electron cyclotron resonance plasma reactors.
Precision shell characterization using radial averaging of x-ray images
Authors: Stephens Richard B.
Published: July 2002

Radially averaging the image of a circular object makes full use of structural information contained in the photograph and optimizes interface detection and location. Measurement of shell dimensions from x-radiograph plates are limited by film graininess and camera resolution. These noise sources make edge determination using single line-outs very uncertain. The radial average process, by coherently adding radial line-outs from the entire circumference, greatly reduces that noise. Our system can detect interfaces between plastic layers with only slight differences in x-ray opacity and locate surface radii with an uncertainty of ≊0.2 μm. This capability has been created with a desktop computer and slight modification to a freeware image processing program, and careful system design.
Adsorption and decomposition of diethylsilane and diethylgermane on Si(100): Surface reactions for an atomic layer epitaxial approach to column IV epitaxy
Authors: Kellerman B. K. , Mahajan A. , Russell N. M. , Ekerdt J. G. , Banerjee S. K. , Tasch A. F. , Campion A. , White J. M. , Bonser D. J.
Published: July 2002

The room-temperature adsorption and desorption kinetics of diethylsilane (DES) and diethylgermane (DEG) on the Si(100)-(2×1) surface were investigated under ultrahigh vacuum using temperature programmed desorption, high resolution electron energy loss spectroscopy, and Auger electron spectroscopy. DES and DEG adsorb at room temperature in a self-limiting fashion, reaching saturation (0.4 and 0.3 monolayers, respectively), at exposures above 30 and 350 L, respectively. Temperature programmed desorption of the DES-saturated and DEG-saturated surfaces revealed only two species, hydrogen and ethylene, desorbing from either surface. In both systems, the hydrogen atoms desorbed primarily through the recombinative desorption of monohydride species, while the ethyl groups decomposed via β-hydride elimination and subsequently desorbed as ethylene. The hydrogen desorption peak temperature was 794 K for the DES-saturated surface and 788 K for the DEG-saturated surface. The desorption peak temperature for ethylene was significantly lower in the DEG/Si(100) system (700 K) than in the DES/Si(100) system (730 K) because of a lower activation energy and higher pre-exponential factor for β-hydride elimination from DEG-dosed Si(100). High resolution electron energy loss spectra of the DEG-saturated surface support an adsorption mechanism in which the ethyl groups remain bonded to the incoming germanium atom throughout the adsorption process.
Molecular dynamics simulations of fluorine molecules interacting with a Si{100}(2×1) surface at 1000 K
Authors: Schoolcraft T. A. , Diehl A. M. , Steel A. B. , Garrison B. J.
Published: July 2002

Molecular dynamics simulations are performed to examine the adsorption of fluorine molecules, having incident translational kinetic energies between 0.0195 and 1.67 eV, on a clean Si{100}(2×1) surface at 1000 K. Results using the Stillinger and Weber potential energy function and the Weakliem, Wu, and Carter parameterization of this potential energy function are compared to each other and to experimental results. The initial sticking probability increases as the incident kinetic energy increases. As the incident kinetic energy increases, more difluorination and less monofluorination is observed as barriers to adsorption are overcome. For difluorination, a time delay between the two atom adsorption events is quantified.
Thermal- and electron-stimulated chemistry of a cyclotriphosphazene lubricant on a magnetic disk with a hard carbon overcoat
Authors: Lin Jong-Liang , Yates John T.
Published: July 2002

The thermal and electron induced decomposition of a bis(4-fluorophenoxy)-tetrakis(3-tri- fluoromethylphenoxy)cyclotriphosphazene(code-named X-1P) lubricant on a magnetic disk are studied by temperature-programmed desorption spectroscopy, electron-stimulated desorption, and Auger electron spectroscopy. X-1P decomposes on the surface with a threshold temperature for dissociation at ∼570 K, ∼100 K lower than the thermal decomposition temperature of fluid molecules. Electron impact also damages X-1P molecules. Depending on the electron energies, dissociative ionization and dissociative electron attachment are both likely mechanisms for the electron-induced dissociation. The cross section for the dissociative electron attachment by 3 eV electrons is roughly 9×10−18 cm2. For both 8 and 25 eV electrons the cross sections are larger.
Synchrotron radiation induced reactions of a condensed layer of silicon alkoxide on Si
Authors: Kinashi Koji , Niwano Michio , Sawahata Jun-ichi , Shimoshikiryo Fumikazu , Miyamoto Nobuo
Published: July 2002

The authors have investigated the synchrotron radiation (SR) induced chemical reactions of condensed layers of silicon alkoxides, tetramethoxysilane Si(OCH3)4 and tetraethoxysilane Si(OC2H5)4, adsorbed on a Si substrate at 80 K. Photon stimulated desorption measurements show that irradiation with SR in the vacuum-ultraviolet region induces the desorption of hydrogen, hydrocarbon, and carbon monoxide from the condensed layer, indicating that the radiation decomposes the alkoxyl group in the silicon alkoxides. Infrared absorption and photoemission data demonstrate that Si-containing fragments produced by the decomposition of silicon alkoxide molecules are polymerized to form silicon oxide. The experimental results show the possibility of deposition silicon oxide film from silicon alkoxides using intense SR in the VUV region.
Surface chemistry of diethylsilane and diethylgermane on Ge(100)
Authors: Mahajan A. , Kellerman B. K. , Heitzinger John M. , Banerjee S. , Tasch A. , White J. M. , Ekerdt J. G.
Published: July 2002

The adsorption and desorption kinetics of diethylsilane (DES) and diethylgermane (DEG) on a Ge(100) (2×1) surface have been studied using temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), and high-resolution electron energy-loss spectroscopy. DES and DEG adsorb at room temperature in a self-limiting fashion. Data indicate that both precursors dissociatively chemisorb, producing a hydrogen- and ethyl-terminated surface. TPD of DES-saturated and DEG-saturated surfaces revealed only two desorbing species, ethylene and hydrogen. The ethylene signal results from the decomposition of the ethyl groups via β-hydride elimination, with a desorption peak temperature of ∼616 K for both precursors. The hydrogen TPD spectra were also similar for both precursors and consisted of two peaks: a low-temperature peak corresponding to hydrogen desorption from the monohydride state and a high-temperature peak corresponding to desorption of hydrogen produced by β-hydride elimination of the ethyl groups. Using the total hydrogen TPD peak area, DES saturation exposure (30 langmuir) led to 0.42 ML Si atom coverage and DEG saturation exposure (30 langmuir) led to 0.35 ML Ge atom coverage, assuming complete β-hydride elimination of the ethyl groups. 0.44 ML of Si was measured by AES following saturation DES exposure. No carbon contamination of the Ge surface was detected by AES for up to four exposure and TPD cycles of either DES or DEG.
Phosphorus impurities in MgxZn1−xTe alloys
Authors: El Akkad F. , Abdel Naby M. , Omar M. Ali
Published: July 2002

P-doped MgxZn1−xTe alloys (0≤x≤0.28) are characterized using room-temperature electrical, optical, and photoelectric measurements. The electrical properties (hole concentration and mobility) indicate an increasing compensation with the increase of Mg content. The donor impurities are attributed to P. The optical absorption spectrum exhibits a peak situated at 1.06 eV, independent of composition. Supportive evidence is obtained for the assignment of this peak to electronic transitions in the shallow P acceptor level originating from the spin-orbit band. The perturbations in the local potential lead to a broadening of the absorption peak and to the appearance of density-of-states tails at the edges of the principal bands. The spectral response of indium surface barriers on undoped and P-doped crystals is investigated. It is found that P doping leads to a lowering of the barrier height and to a shift in the high-energy edge of the spectral response toward lower energies. The latter is attributed to the presence of a thin insulating interfacial layer and a high density of interface states in the P-doped contacts. It is suggested that P has a role in determining the characteristics of the interface.
Adsorption of sulfur on bimetallic surfaces: Formation of copper sulfides on Pt(111) and Ru(001)
Authors: Kuhn Markus , Rodriguez José A.
Published: July 2002

The interaction of sulfur and copper on Pt(111) and Ru(001) has been examined using x-ray photoelectron spectroscopy and thermal desorption mass spectroscopy. Cu/Pt(111) and Cu/Ru(001) surfaces were exposed to S2 gas at 300 K. It was found that for both substrates stable copper–sulfide films were formed, of which the Cu–S/Ru(001) system was the more stable. The decomposition of the Cu2S films on Pt(111) occurred at 600–850 K and on Ru(001) at 900–1000 K. Breakdown of the films led to evolution into the gas phase of sulfur (mainly as S2) without desorption of copper or the sulfur chemisorbed on the substrate. This chemisorbed sulfur desorbed in a broad feature from 1000 to 1500 K. For the Ru(001) substrate the Cu atoms remained on the surface until they desorbed at 1080 K, while on Pt(111) the Cu atoms migrated into the Pt(111) surface to form a subsurface Cu–Pt alloy; no Cu desorption features were seen at temperatures as high as 1300 K. On Pt(111), copper sulfide promoted the formation of a bulklike platinum sulfide. No sulfidation of ruthenium was detected in the presence of copper–sulfide films. For both substrates the sulfur atoms were found to highly perturb the copper sites, decreasing the ability of the noble-metal adatoms to adsorb CO.
Vacuum characteristics of titanium
Authors: Minato Michio , Itoh Yoshio
Published: July 2002

Little attention has been paid to metals other than stainless steels and aluminum alloys as materials for ultrahigh vacuum (UHV) and extremely high vacuum (XHV) chambers. Titanium is another candidate material for use in UHV and XHV applications. To obtain basic data for the application of titanium to UHV and XHV, an apparatus employing the conductance modulation method was fabricated for the measurement of the outgassing rate. In the measurement of the outgassing rate of small samples, it was found that the outgassing rate of titanium decreased 1.5 times faster than that of stainless steel. Furthermore, a TiN coating was found to reduce the total amount outgassed from 1.78×10−2 to 1.17×10−2 Pa m3 in the measurement of titanium and from 1.02×10−1 to 9.22×10−3 Pa m3 in the measurement of stainless steel. In a mass analysis of the gases from the samples, the ion current of hydrogen from chemically polished titanium, chemically polished and TiN-coated titanium, and TiN-coated stainless steel decreased after attaining a maximum, while that from buffed and electropolished stainless steel increased continuously during the baking at 200 °C. Considering these results, a vacuum chamber made of titanium coated with TiN and a vacuum chamber made of electropolished stainless steel were prepared and pumped down into XHV region. The pressure of the titanium chamber reached 6×10−11 Pa after a 312 h baking at 250 °C, while the stainless steel chamber required a 434 h baking at 250 °C to attain the ultimate pressure of 7×10−11 Pa. The pressure of the titanium chamber decreased more rapidly than that of the stainless steel chamber during the baking at 250 °C.
Application of electron cyclotron resonance plasma source to conductive film deposition
Authors: Shimada Masaru , Ono Toshiro , Nishimura Hiroshi , Matsuo Seitaro
Published: July 2002

An electron cyclotron resonance (ECR) plasma source for conductive film deposition has been developed and applied to chemical vapor deposition (CVD) and sputtering deposition. In the source, 2.45 GHz microwaves are divided into two directions and transported into the composer through quartz windows which maintain the vacuum. The windows are set blind to the ECR plasma to prevent film deposition on them and in a region of higher magnetic field than that of the ECR condition to produce high density plasma. High ion current densities over 10 mA/cm2 can be stably obtained with this source. In applying the source to CVD, SiC films can be deposited with high reliability using C2H4/SiH4 plasma. Moreover, Ti films can be deposited by using a sputtering material supply. Using a rotating inclined substrate holder the uniformity of the film is found to improve and a uniformity of ±5% should be obtained over a 6-in. wafer.
X-ray photoelectron and infrared spectroscopies of Cu-implanted silica and borosilicate glasses
Authors: Henderson D. O. , George M. A. , Tung Y. S. , Mu R. , Burger A. , Morgan S. H. , Collins W. E. , White C. W. , Zuhr R. A. , Magruder R. H.
Published: July 2002

Fourier transform infrared (FTIR) spectra and x-ray photoelectron spectra (XPS) were acquired from Cu implanted in fused silica and a borosilicate glass. The FTIR spectra indicate that Cu ion implantation in the silica and borosilicate glasses results in an intensity decrease in the Si–O stretching vibration. The Si–O stretching vibration of the implanted glass is redshifted by 20 cm−1 with respect to the virgin glass. The redshift is attributed to a decrease in the Si–O–Si bridge angle. A shoulder appearing on the low frequency side of the Si–O stretching vibration observed only in the implanted glasses is attributed to Si–O dangling bonds. The XPS depth profiles revealed that the fused silica sample was depleted in oxygen by as much as 20% at a depth of 18 nm, while the borosilicate glass at a depth of 200 nm is depleted in boron by as much as 37%. Deconvolution of the O(1s) peak reveals two components located at 532.7 and 534.3 eV for silica and the borosilicate glasses. The lower binding energy peak is attributed to the binding energy for O(1s) electron in silica, while the higher energy peak is attributed to a peroxy related defect.
Enhanced deposition rate of lithium phosphorus oxynitride thin films by sputtering of Li3PO4 in N2–He gas mixtures
Authors: Bates J. B. , Yu Xiaohua
Published: July 2002

The addition of He to N2 increases significantly the deposition rate of lithium phosphorus oxynitride thin films by radio frequency magnetron sputtering of Li3PO4 targets. From the correlation with the optical emission intensity, the enhanced rate is attributed to an increase in the N+2 ion concentration in the plasma due to Penning ionization. The ionic conductivity of the films deposited at higher rates in He+20% N2 compares favorably with that of films deposited at lower rates in pure N2.
Chemical and matrix effects on sensitivity factors in electron spectroscopies. I. C and Si containing materials
Authors: Ke R. , Haasch R. T. , Finnegan N. , Dottl L. E. , Alkire R. C. , Farrell H. H.
Published: July 2002

The dependence of Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy sensitivity factors on the detailed atomic and electronic environment has been studied for several materials containing C and/or Si. The matrices containing these elements include diamond, graphite, Si0.5C0.5, and Si. It was found that correcting the sensitivity factors for atomic density, electron attenuation length, and electron backscattering improved the agreement between the measured and the true composition by up to an order of magnitude except for AES transitions involving valence band electrons. The effects of changing surface composition due to oxidation and surface segregation are also discussed.
Growth dynamics and surface fine structure of ZnO ultrafine particle films
Authors: Dachun Zhao , Zhongkai Qu , Xiaoren Pan
Published: July 2002

Growth dynamics and surface fine structure of ZnO ultrafine particle (UFP) films prepared by dc-gas discharge activated reactive evaporation (dc-gas discharge) deposition technique were studied. Spectroscopic study was performed with small angle x-ray scattering (SAXS) and surface extended energy loss fine structure (SEELFS). The SAXS probe of the nature of the film surface should lead to a more complete understanding of the mechanism of film forming and growth dynamics. The highly disordered aggregate film can be described as fractal objects with a mass and surface fractal dimension equal to 2.73 and 2.94, respectively. In addition, the SEELFS spectra of ZnO UFP film was obtained and the data were analyzed by fast Fourier transform. The results indicate that the distance between Zn and O of ZnO UFP film is 1.81 Å. Scanning electron microscope and scanning tunneling microscope were used to study the ZnO UFP film.