bluuebunny/crossref_metadata_2025 huggingface dataset:
Liquid metal alloy ion sources for B, Sb, and Si
Authors: Gamo K. , Ukegawa T. , Inomoto Y. , Ochiai Y. , Namba S.
Published: July 2002

B, Sb, and Si ion sources using liquid metal alloys have been fabricated and basic characteristics such as current–voltage relations, angular current intensity, energy distribution, and mass spectra have been measured. Singly charged B ions which amount to 33% of the total ions and have an angular current intensity of ∠40 μA/sr at a total energy spread (FWHM) of ∠20 eV were obtained using B–Ni–Pt alloys. Singly charged Si and Sb ions with an angular current intensity of ∠11 μA/sr and ∠1.4 μA/sr at an energy spread of ∠20 eV were obtained by using Si–Au and Sb–Pb–Au alloys, respectively. These ion sources could be operated for more than 10 h without any changes in mass spectra.
Hydrogen plasma etching of semiconductors and their oxides
Authors: Chang R. P. H. , Chang C. C. , Darack S.
Published: July 2002

Hydrogen plasmas have been used to etch surfaces of semiconducting materials (e.g., GaAs, GaSb, InP, Si), their oxides, and Si nitride. Using a combination of analytical techniques—spectroscopic ellipsometry, Auger spectroscopy, and scanning electron microscopy (SEM), the etch rates, the surface composition and morphology have been studied. It is demonstrated that the selective etching rate of hydrogen plasma for Si over SiO2 is ∠30, and that for GaAs oxide over GaAs is ∠2. It is also shown that the hydrogen plasma etched (and air exposed) GaAs surfaces have a Ga/As concentration ratio nearly equal to that of the air cleaved GaAs surface. Similar results have also been obtained for GaSb. Hydrogen plasma etched InP shows surface segregation and is rich in In. The etch rates of the semiconductors and their oxides vary by several orders of magnitude from compound to compound as determined from ellipsometry and SEM. It is also demonstrated that scanning ellipsometry can be used to monitor surface etching processes. Some advantages and disadvantages of the use of hydrogen plasma for surface preparation and etching applications are discussed.
Auger and photoelectron line energy relationships in aluminum–oxygen and silicon–oxygen compounds
Authors: Wagner C. D. , Passoja D. E. , Hillery H. F. , Kinisky T. G. , Six H. A. , Jansen W. T. , Taylor J. A.
Published: July 2002

Silicon–oxygen and aluminum–oxygen compounds exhibit significant XPS Auger and photoelectron chemical shifts that are accurately measurable. Chemical state plots of KLL Auger kinetic energy versus 2p photoelectron energy permit identification of chemical species from the locations of their points on the plots. The KLL Auger electrons of Al and Si were generated by the bremsstrahlung component of the radiation, with conventional instrumentation. The location of points on the plots can be understood on the basis of polarizability of the environment (on the Auger parameter grid of lines, slope +1) and on the basis of the factors contributing to the energy of the final state ion in the Auger transition (a grid of line, slope −1). Tetrahedral aluminum has a significantly smaller Auger parameter than octahedral aluminum, and this difference is repeated, but with reduced magnitude on the similar plots for silicon and oxygen lines for the same compounds. Otherwise, the Auger parameters for this class of compounds are remarkably uniform. The Auger parameter values for oxygen and sodium in these compounds, using the 1s and KLL lines, are relatively small compared to those of other compounds of oxygen and sodium. For compounds of similar Auger parameter, differences in Auger final state ion energy are interpretable on the basis of electron density on aluminum and silicon atoms in the initial state, due to extent of bonding to oxygen, or to amount of negative formal charge on the silicate structure. Inclusion of tetrahedral aluminum enhances the negative charge and decreases the final state ion energy in high alumina zeolites. The difference between the energies of the O1s and Si2p lines in the inorganic silicon compounds is almost invariant, 429.0 to 429.6 eV. The three silicon polymers examined have a significantly larger line difference, 429.8 to 430.1 eV, making possible a differentiation between silicones and silicates. The oxygen KVV lines, with Auger transition final vacancies in valence levels, have shapes characteristic of chemical structure. The uncharged Si–O–Si structure exhibits a well-defined shoulder; in Al–O–Si the shoulder is so close in energy it merely gives rise to asymmetry in the peak; Al–O–Al and charged Si–O–Si give oxygen KVV lines as single sharp peaks.
Screening energy involving electrons of remote atoms in photoelectric and Auger transitions
Authors: Wagner C. D. , Taylor J. A.
Published: July 2002

The difference in kinetic energy between Auger electrons and photoelectrons from atoms of an element is a function of the atomic environment. Chemical shifts in this parameter are a measure of the change in polarizability of the environment, which contributes to screening of the final state in these transitions. Comparison of this parameter for covalent molecules in gaseous and solid states demonstrates a significant role in this screening by neighboring condensed molecules, outside the immediate electronic system of the molecule containing the ionized atom. In the molecules tested, SF6, SO2, and CS2, the extent of remote screening for a singly charged ion was 1–2 eV.
Measurements of angular evaporation characteristics of sources
Authors: Dobrowolski J. A. , Ranger M. , Wilkinson R. L.
Published: July 2002

An apparatus is described for the rapid and reliable measurement of the angular evaporation characteristics of sources. It consists of a moving and a stationary quartz crystal evaporation rate monitor, and it can be operated at any chosen azimuth angle. The instrument has been used to demonstrate the effect of source design, rate of evaporation, external obstructions, and evaporant material on the angular evaporation characteristics of high rate, high capacity evaporation sources.
Evaluation of Zr–V–Fe getter pump for UHV system
Authors: Hseuh H. C. , Lanni C.
Published: July 2002

The nonevaporable getter pump St707(Zr–V–Fe) from SAES Getters, Inc. may be activated and operated at lower temperatures than those for the St101 getter. However, its application to a UHV system has not been reported yet. This paper reports the characteristics of the St707 getter strip in a UHV system as a linearly distributed pump. The getter is activated at ∼400 °C for 30 min. The pumping behavior of the getter strip for H2 and CO is studied. The initial pumping speeds per meter of the getter strip for H2 and CO are 300 and 190 ℓ/s, respectively; the H2 speed decreases slowly with increasing gas load to ∼90 ℓ/s at H2 gas loading of ∼50 Torr ℓ/m. Hydrogen equilibrium pressure at temperature <500 °C does not follow the Sieverts law and is higher that that predicted by SAES Getter, Inc. The application of St707 getter strip to the UHV system of ISABELLE is also discussed.
Highly oriented ZnO films grown by laser evaporation
Authors: Sankur H. , Cheung J. T.
Published: July 2002

A relatively new deposition technique involving laser-assisted evaporation is applied to the deposition of thin ZnO films. Highly oriented and crystalline films of ZnO were obtained by CO2 laser evaporation of ZnO powder targets on substrates held at 50–450 °C. Optical transmission spectra of these films show a sharp cutoff at 380 nm. The refractive index, as measured by ellipsometry, is 1.98–2.04. As-grown films are conducting (0.1–1 Ω cm), but become insulating when 0.1% Li2O is added to the source. SAW devices built with these films proved the piezoelectric nature of laser-evaporated ZnO. It is found that the laser deposition technique is applicable to producing device quality ZnO films with good reproducibility.
Infrared laser photoacoustic spectroscopy of adsorbed species
Authors: Chuang T. J. , Coufal H. , Träger F.
Published: July 2002

Infrared photoacoustic studies of SF6 and NH3 adsorption on silver films characterized by XPS have been performed under UHV conditions with a tunable CO2 laser. The results clearly demonstrate submonolayer surface sensitivity of the photoacoustic technique. Studies of both gas–surface systems further illustrate the simplicity and general applicability of this surface vibrational technique.
Self-limiting etch depths using simultaneous sputter etching/deposition technique
Authors: Berg S. , Gelin B. , Östling M. , Babulanam S. M.
Published: July 2002

During sputter etching in argon, time is most commonly used as the parameter determining the total etch depth. If the argon is replaced by CH4 during substrate etching the effect will be that etching stops, CH4 decomposes in the plasma, and a carbon film starts to deposit on the substrate. This effect will also be obtained if a mixture of Ar/CH4 is used during processing. Depending on the concentration of CH4 in the gas mixture it will take different times before a monolayer of carbon is formed at the substrate surface. During this time interval the substrate material is exposed to energetic ion sputter etching. The total amount of original substrate material etched away before the substrate is completely covered by carbon is dependent of Ar/CH4 ratio and on substrate material. The carbon layer can easily be removed by an O2 plasma when the process is completed. A process has thus been obtained that can create a self-limited etch depth (SLED) into a surface material independent of processing time as long as the time exceeds a minimum value. This SLED effect is presented for different substrates like Pt, Al, Au, Zr, Si, and SiO2. The etch depth can be varied by changing the CH4 concentration and the bias voltage. We also show how the technique can be used to obtain a high selectivity etch between Au and Si and between Au and SiO2.
DITE Langmuir probe results showing probe-size and limiter-shadow effects
Authors: Stangeby P. C. , McCracken G. M. , Erents S. K. , Matthews G.
Published: July 2002

Experimental evidence is presented for three probe-size effects which influence the interpretation of Langmuir probe measurements in tokamak scrape-off plasmas. Small probes can give erroneously high values of plasma density. Large probes can only measure reliably the average energy of the high energy tail of the electron distribution. Insertion of a large probe into the scrape-off plasma can strongly disturb the plasma necessitating special analysis procedures for recovery of the unperturbed plasma characteristics.
Glass reactivity in aqueous solutions
Authors: Baer D. R. , Pederson L. R. , McVay G. L.
Published: July 2002

Surface analysis methods have been incorporated as part of several studies concerning the mechanisms and amount of glass leaching in aqueous solutions. The reactivity of simple glasses with water has been determined by measuring the uptake of D and 18O in soda-lime silicate glass, amorphous and crystalline silica, and amorphous and crystalline albite leached in D218O at 90 °C as a function of time. The concentrations and profiles of 18O and D going into the glass were determined using nuclear reaction analysis and compared to the material leached from the glass as determined by solution and Rutherford backscattering (RBS) analyses. The measured ratio of D/18O does not follow any one simple uptake model. Reaction layers formed on simulated nuclear waste glasses containing Pu have also been measured using RBS. Specimens were leached in deionized water or brine at 90 °C. The concentration of Pu on the specimens generally decreased with time. Analysis of the leaching solution indicated that the rate of Pu release was considerably less than that of the glass matrix. The results support the buildup of a surface layer covering the Pu.
Low resistivity CdS thin films grown by flash-evaporation at low substrate temperature (150–200 °C)
Authors: Canevari V. , Romeo N. , Sberveglieri G. , Azzi S. , Tosi A. , Curti M. , Zanotti L.
Published: July 2002

Undoped and In-doped CdS films have been grown by flash-evaporation at a substrate temperature between 150 and 200 °C. A resistivity of 5 Ω⋅cm has been obtained for undoped CdS films at 150 °C substrate temperature while a resistivity of about 2.5×10−3 Ω⋅cm could be obtained for 1% In-doped CdS films at any substrate temperature between 150 and 200 °C. The transparency of such films for wavelengths larger than that of absorption edge is close to 100% when corrected for the reflection loss. Due to the above characteristics these films are suitable as windows in heterojunction solar cells.
Preparation of surfaces for high quality interface formation
Authors: Vossen J. L. , Thomas J. H. , Maa J.-S. , O’Neill J. J.
Published: July 2002

Successful fabrication of Ohmic contacts, Schottky barriers, and metal–metal contacts for multilevel metallization in integrated circuits requires very careful preparation of the substrate surface. As device dimensions shrink, this becomes increasingly more important. This paper reviews various surface treatments that are used to prepare surfaces for metal–film deposition. These include: wet chemical treatments, temporary protection techniques, glow discharge sputter etching, ion-beam sputter etching, and plasma surface treatments using reactive gases. Because of serious problems with all other methods of surface preparation, it is concluded that plasma surface treatments should be used for small-geometry devices. The implications of this to the design of metallization equipment are described.
Electron-gun evaporators of refractory metals compatible with molecular beam epitaxy
Authors: Heiblum M. , Bloch J. , O’Sullivan J. J.
Published: July 2002

The construction and performance of electrostatic electron gun evaporators, placed in a molecular beam epitaxy system are described. Minimizing electron emittance led to an evaporation of refractory metals at a vacuum level of 2×10−10–2×10−9 Torr.
On the sputtering yield of molecular ions
Authors: Steinbrüchel Ch.
Published: July 2002

It is shown that the sputtering yield of a molecular ion can be expressed in terms of the sputtering yields of the constituent atoms, irrespective of the details of the process by which the molecular ion dissociates upon impact on the target surface. It then follows that, in general, sputtering yields on a clean surface should be about the same for molecular and atomic ions of the same mass and energy, exceptions being very light targets or very heavy projectiles, in which cases sputtering yields for molecular ions should be somewhat higher. For ions which are chemically reactive with respect to a target and thus change its surface composition, these conclusions need to be modified. Sputtering yields at very low ion energy, i.e., near the sputtering threshold, are also discussed and compared for atomic and molecular ions.
A comparison of the outgassing characteristics of several solar absorbing coatings
Authors: Erikson E. D. , Berger D. D. , Frazier B. A.
Published: July 2002

An investigation has been conducted of the room temperature outgassing characteristics of several optically black solar absorbing coatings. The coatings were deposited either electrochemically, by spraying, or by brushing onto aluminum or stainless steel substrates. Vacuum outgassing rates and residual gas evolution have been studied for exposure times on the order of 100 h. Representative outgassing values are given for the following coating/substrate combinations: anodized and black dyed aluminum, etched electroless nickel on aluminum, black chrome on aluminum and on stainless steel, and black paint on aluminum. The results confirm that the outgassing rates of these coatings can be expressed as an exponential decay function of the form gt=At−m, where the outgassing rate at a specific time gt is a product of the outgassing rate after 1 h exposure to vacuum A and the time t raised to the inverse power of m. In the case of the anodized aluminum, m was found to be approximately equal to 0.5. For the other materials, m was found to be about equal to 1.0.
Design and performance of a quartz oscillator vacuum gauge with a controller
Authors: Ono M. , Hirata M. , Kokubun K. , Murakami H. , Tamura F. , Hojo H. , Kawashima H. , Kyogoku H.
Published: July 2002

We designed, built, and tested the first model of a quartz friction vacuum gauge and its controller, using a tuning fork shaped miniature quartz oscillator of a wristwatch as a pressure sensor. This gauge made it possible to measure pressure from 0.01 Torr to more than 760 Torr with an accuracy of better than 10%. The oscillator was installed on a small-sized vacuum flange and driven at its resonance frequency by constant amplitude ac voltage fed by a phase-locked loop oscillation circuit. The resonance current of the oscillator was rectified and amplified to actuate a meter and/or a recorder. The pressure dependence of the readings of the gauge for various gases was measured, and found to be in agreement with theoretical predictions. The performance of the gauge was unaffected by hundreds of repetitions of a quick evacuation from atmospheric pressure to less than 0.001 Torr and an exposure to the air.
Thickness of natural oxide films determined by AES and XPS with/without sputtering
Authors: Mathieu H. J. , Datta M. , Landolt D.
Published: July 2002

The thickness of natural air-formed oxides on Al, Si, Fe, Ni, and Ta is determined by Auger electron spectroscopy (AES), depth profiling, and angle-resolved photoelectron spectroscopy (XPS). The sputter rate of the oxides is measured under the same conditions and their values are given with respect to a certified standard 100 nm Ta2O5 reference. Data from AES depth profiling are corrected for the influence of the electron mean free path. XPS data are evaluated from area intensities of the bands after peak synthesis (fitting). Using literature values of mfp for oxides, their thickness is evaluated. AES and XPS data are in reasonable agreement giving oxide thickness ranging from 0.2 to 5 nm increasing in the order of SiO2<NiO<Al2O5<Fe2O3.
The effect of bulk hydrogen inventory on the chemical erosion of graphite
Authors: Haasz A. A. , Auciello O. , Stangeby P. C.
Published: July 2002

Methane formation due to sub-eV H0 impact on pyrolytic graphite is characterized by an initial transient effect, followed by a steady state behavior. The nature of the transient is strongly affected by the preexposure history of the sample, viz., sample bakeout temperature during preparation, preheating of sample before H0 exposure, and previous exposure of sample to H0 fluxes. Preheating of the sample at ≥2200 K for several minutes results in the elimination of the transient. By contrast, the steady state CH4 production does not appear to be sensitive to previous sample history for samples initially baked at ≥1700 K.
The synthesis of SiCx films by dual-source sputter deposition
Authors: Seaward K. L. , Barbee T. W. , Tiller W. A.
Published: July 2002

Beta-silicon carbide has been synthesized by sputter deposition from separate elemental silicon and carbon targets onto substrates above 700 °C. Deposited samples had a range of compositions continuously varying from carbon-rich to silicon-rich. Sample thickness and composition were correlated by means of thickness profiles that were compared to models based on ideal atomic volumes in the phases observed. This correlation, in conjunction with analyses of crystalline phases and microstructure, indicated that carbon-rich samples were a combination of beta-SiC and amorphous carbon, and silicon-rich samples consisted of small beta-SiC particles in a silicon matrix that had a layered microstructure. Beta-SiC with (111) preferred orientation was formed at the 1:1 Si:C location. This material had a columnar microstructure with lateral grain size of ∼50 Å and through-film grain size of ∼500 Å. The refractive index of the beta-SiC was comparable to published values and films deposited on sapphire were p-type with sheet resistivity around 2 Ω cm.
Hollow-cathode-enhanced magnetron sputtering
Authors: Cuomo J. J. , Rossnagel S. M.
Published: July 2002

A hollow cathode arc electron source has been added to a conventional planar magnetron sputtering system to form a triode magnetron. The hollow cathode source was chosen in place of a filament for high emission current at low energy, lifetime, and ease of operation in high magnetic fields and reactive gases. The electrons emitted from the hollow cathode produced additional gas ionization, resulting in a denser plasma at constant voltage. Up to 60% of the hollow cathode emission current could be directly coupled into the discharge current of the magnetron. Increases in the discharge current and the deposition rate of up to 10× were recorded over the conventional magnetron at the same voltage. The hollow cathode enhanced magnetron discharges were also capable of high current operation at voltages down to 20 V, which is below the sputter threshold. The pressure of operation could also be reduced significantly, and the magnetron could be operated at full power as low as 5×10−5 Torr in argon.
The influence of deposition temperature on the structure and optical properties of vanadium oxide films
Authors: Chain E. E.
Published: July 2002

Thin films of various vanadium oxides, including the phase transition material vanadium dioxide, have been deposited onto sapphire substrates by reactive ion-beam sputtering. In this process, an argon ion beam sputters a vanadium target in the presence of an oxygen background. Coating chemistry, structure, surface morphology and electrical properties, together with the optical response at 3.4 μm wavelength, were studied as a function of the variation of film growth temperature Ts. Films deposited in the range 350 °C<Ts<620 °C and with a uniform argon ion beam pressure (2×10−4 Torr) and oxygen background pressure (3×10−4 Torr) show a strong dependence of growth characteristics and film properties on the deposition substrate temperature. In analogy to Thornton’s zone model for the temperature dependence of sputtered metal film growth, these metal oxide films can also be separated into different growth regions based on observed physical properties.
Deposition of pyrocarbon in a low temperature environment
Authors: Inspektor A. , Carmi U. , Raveh A. , Khait Y. , Avni R.
Published: July 2002

This work presents aspects of the preparation of pyrocarbon (PyC) depositions at relatively low temperatures (300–500 °C) and discusses its properties. The deposition process which is performed in a nonequilibrium low pressure rf plasma of propylene–argon or methane argon mixtures coats thermally sensitive materials. The properties of the coatings were found to be similar to the properties of CVD–PyC films obtained at higher temperatures (>1000 °C). The measured properties and their correlation to the experimental working parameters for the deposition of pyrocarbon are presented and discussed.
HgTe and CdTe epitaxial layers and HgTe–CdTe superlattices grown by laser molecular beam epitaxy
Authors: Cheung J. T. , Niizawa G. , Moyle J. , Ong N. P. , Paine B. M. , Vreeland T.
Published: July 2002

CdTe and HgTe epilayers and HgTe/CdTe superlattices have been grown by laser molecular beam epitaxy (laser MBE) on CdTe substrates. The power density of the laser radiation used to evaporate source materials was found to be a very important growth parameter. The superlattice structures have been characterized by helium ion backscattering spectrometry, x-ray double crystal diffractometry, and low temperature electrical transport measurements. Results indicate good crystallinity and very strong 2D carrier confinement at low temperatures. At 77 K, electron mobilities in excess of 50 000 cm2/V s have been observed. Quantum Hall effect has been observed for the first time in this system.
Tellurium precipitation in bulk-grown CdxHg1−xTe
Authors: Williams D. J. , Vere A. W.
Published: July 2002

When Te-saturated CdxHg1−xTe is cooled from temperatures in excess of approximately 400 °C, precipitation of second-phase Te may occur. We have studied this precipitation as a function of the microstructure of the material prior to cooling and as a function of cooling rate. The results indicate that these parameters control the balance between heterogeneous and homogeneous nucleation and that, by careful control of precooling time at high temperature and cooling rate, precipitate-free material can be reproducibly obtained.
Calibration of mass spectrometers for quantitative gas mixture analysis
Authors: Ellefson Robert E. , Cain David , Lindsay Charles N.
Published: July 2002

Quantitative analysis of gas mixtures from sources external to a mass spectrometer (MS) requires vacuum hardware that systematically introduces the gas to the ionization region of the MS and calibration procedures that reflect the MS response to time dependent partial pressures in the gas source. Formalism for describing the gas flow, fractionation processes, and the ionization process is presented. Long-term sensitivity data for D2 is presented for three types of mass spectrometers: a quadrupole, a cycloid, and a magnetic sector mass spectrometer. The use of appropriate standard gas mixtures to monitor the accuracy of the MS calibration by control chart is advocated. Bias data from control charts can be used as the basis for minor calibration adjustments rather than total recalibration.
Influence of composition and process parameters on the internal stress of the carbides of tungsten, chromium, and titanium
Authors: Bergmann E. , Vogel J.
Published: July 2002

We have investigated the relationship between deposition process and mechanical properties of metal+carbon coatings of three different metals. We used a conventional sputtering system, equipped with planar magnetrons, whose configuration can be scaled up easily to an industrial batch coater. Metal as well as carbide targets were compared and acetylene was used as a reactive gas. The films were deposited onto substrates made of a high-speed steel. Internal stresses were determined by measuring mechanically the flexture of a thin disk. The variation of the mechanical properties, internal stress, and hardness were completely different for the three metals.
Tribological coatings for nuclear applications in the United Kingdom
Authors: Lewis M. W. J.
Published: July 2002

The performance and uses of hard coatings to provide resistance to static adhesion, fretting, galling, and wear in nuclear reactor environments in the United Kingdom are discussed, and examples are given of the coatings selected for such applications in high-temperature carbon dioxide and liquid sodium. In particular, the successful use in liquid sodium of coatings based upon a pack aluminizing process is highlighted, and developments in coatings to allow local application of nickel aluminide are mentioned. In carbon dioxide environments, experiences with tungsten carbide and chromium carbide detonation gun coatings are reviewed and illustrated with actual components.
Mass-dependent effects of channel electron multipliers in residual gas analyzers
Authors: Reagan Noreen R. , Frees Louis C. , Gray John W.
Published: July 2002

Residual gas analyzers (RGA’s) are increasingly being used to obtain quantitative information about vacuum processes. The gain for an ion [electron multiplier (EM) output current divided by the Faraday cup (FC) output current] determined by experiment for a combination FC/EM sensor was not constant for increasing mass. The gain for ions of different masses was also found to be dependent on the chemical nature of the ion, reflecting the conversion efficiency of incident ions to secondary electrons [U. Fehn, Int. J. Mass Spectrom. Ion Phys. 15, 391 (1974); 21, 1 (1976)]. Allowance for these effects makes quantitative RGA measurements in the EM mode of the sensor more reliable. Methods for determining a correction factor are discussed.
Analysis of indium nitride surface oxidation
Authors: Foley C. P. , Lyngdal J.
Published: July 2002

InN is a III–V semiconductor with a wide band gap of 1.89 eV and mobility of 2700 cm2 V−1 s−1 (300 K) which has applications in optoelectronics. As with GaAs, surface oxidation and degradation after aging in air is a problem that must be taken into account during device fabrication. Of the possible techniques, x-ray photoelectron spectroscopy was used as it could detect nitrogen, while the x-ray beam did not preferentially sputter nitrogen as rapidly as other techniques. Various sample preparation techniques and sputter etching with xenon were used to avoid nitrogen depletion as well as to view initial chemisorption of oxygen onto InN surfaces. We found the surface oxidation of InN was clearly dependent on the aging and sample treatment history. The first stage of oxidation is the bonding of oxygen onto nitrogen to form an In–NO complex. After sputter etching or abrasive cleaning, the In–NO complex further oxidized to form an In–NO2 complex. The final oxidation state after aging was found to be dependent on the sample preparation conditions. Finally, the In(3d5/3) Auger parameter plots indicate that the indium is predominantly bonded to nitrogen regardless of the aging and sample treatment. These results correspond closely to studies on GaAs where during the oxidation process, oxygen chemisorbs onto the metalloid.
Depth profile analysis of hydrogenated carbon layers on silicon by x-ray photoelectron spectroscopy, Auger electron spectroscopy, electron energy-loss spectroscopy, and secondary ion mass spectrometry
Authors: Sander P. , Kaiser U. , Altebockwinkel M. , Wiedmann L. , Benninghoven A. , Sah R. E. , Koidl P.
Published: July 2002

Hydrogenated amorphous carbon layers (a-C:H) on silicon show substantial amounts of silicon carbide in the interface, which has been identified with x-ray photoelectron spectroscopy and Auger electron spectroscopy by comparison to Si, C, and SiC standards. The quality of such layers, in particular, adhesion and hardness, becomes better with increasing width of the depth distribution of this interfacial carbide.
Magnetic enhancement of cathodic arc deposition
Authors: Sanders D. M. , Pyle E. A.
Published: July 2002

Cathodic arc deposition offers some important strengths as a deposition process. Material can be deposited at extremely rapid rates and large fractions of the evaporant are ionized, permitting control of the arrival energy of the depositing material. In addition, the depositing material can be directed by magnetic and electrostatic fields to specific locations within the chamber. In the present study, magnetic fields were used to achieve such control of a copper plasma, leading to a fourfold enhancement in the effective deposition rate and a simultaneous improvement in coating adhesion.
Impregnated cathode coated with tungsten thin film containing Sc2O3
Authors: Yamamoto Shigehiko , Taguchi Sadanori , Watanabe Isato , Kawase Susumu
Published: July 2002

An impregnated cathode of a novel structure is proposed, fabricated, and evaluated. A thin tungsten film 100–400 nm in thickness containing various amounts of Sc2O3 is coated on a standard impregnated cathode composed of a porous tungsten body in which electron emissive materials are impregnated. The electron emission property measured with a diode configuration is found to be dependent on Sc2O3 content and surface atom distribution. Surface atom distribution is depicted by means of Auger electron spectroscopy. For high electron emission enhancement it is necessary for Sc2O3 content to be 2.5–6.5 wt. % and for a layer of the order of a monolayer in thickness composed of Ba, Sc, and O to develop on the cathode surface.
Induced drift currents in circular planar magnetrons
Authors: Rossnagel S. M. , Kaufman H. R.
Published: July 2002

The circulating E×B drift currents in a circular planar magnetron have been measured as a function of discharge parameters. The drift current was calculated from the magnetic field measured at a probe located over the center of the drift loop. The drift current was found to vary almost linearly with magnetron discharge current over the entire range of the magnetron power capability. The drift current-to-discharge ratio ranged from 2.5–9 and was dependent on gas pressure, and to some extent on gas species and cathode material. This ratio was derived using both classical two-body relations and also Bohm diffusion considerations. The results of the Bohm diffusion calculations are in close agreement with the experimental measurements. An additional feature confirming the Bohm diffusion results is the weak dependence of the observed drift current on gas species. Bohm diffusion is based on turbulent, collective interactions between electrons and the choice of gas species should only have an indirect effect through the electron density and temperature.
Crystal growth of Ge studied by reflection high-energy electron diffraction and photoemission
Authors: Aarts J. , Hoeven A.-J. , Larsen P. K.
Published: July 2002

We have combined the techniques of reflection high-energy electron diffraction and photoemission in order to study crystal growth of Ge by molecular-beam epitaxy. Intensity oscillations in the reflected electron beam for deposition on both (001) and (111) surfaces at 20 °C indicate that the growth is essentially layer by layer. The evolution of valence bands and core levels as a function of deposition reveals that in the case of Ge(001) the Ge bulk band structure remains present, indicating crystalline growth. For Ge(111) the bulk band structure disappears and finally resembles the band structure of amorphous Ge, indicating a completely disordered film. At 200 °C, however, the crystalline band structure remains present.
Control of ion bombardment energy in the low-temperature deposition of highly transparent and conducting In2O3 and ZnO thin films by activated reactive evaporation
Authors: Lau W. S.
Published: July 2002

Highly transparent and conducting In2O3 and ZnO films have been successfully deposited at temperatures as low as <70 °C by activated reactive evaporation. Ways to control the anode-to-film potential, which can be used as a rough measure of ion bombardment energy, are discussed. It was found that a minimum anode-to-film voltage of ∼20 V is necessary for high mobility (∼18 cm2 V−1 s−1) for In2O3. However, for the case of ZnO, it was found that there is no such a minimum ion bombardment energy. X-ray diffraction data on low-temperature deposited In2O3 and ZnO films are also presented, showing that ZnO films are in general easier to crystallize than In2O3 films. A postulate was also made that microvoids can be filled up more easily in the case of zinc oxide deposition because the low sticking coefficient of zinc allow its vapor to go around corners more easily and thus the process is not pure physical vapor deposition but has a substantial component that behaves like a surface rate-limited chemical vapor deposition process. Hence the explanation is simply that very little energy is necessary to get ZnO films with an electron mobility of ∼40 cm2 V−1 s−1 by activated reactive evaporation. This is, however, not the case for sputtering and thus this may have an important implication that there can be less ion damage on some sensitive substrates for low-temperature deposition of ZnO by activated reactive evaporation.
Diamond films by ion-assisted deposition at room temperature
Authors: Kitabatake Makoto , Wasa Kiyotaka
Published: July 2002

Hard carbon films were prepared by ion beam sputter deposition. A graphite disk was used as a target. An electron-bombardment ion source emitted the argon ion beam whose energy and current were 1200 eV and 60 mA, respectively. The surface of a substrate was set in a direction which was almost parallel to the direction of the ion beam. The ion beam sputtered the carbon target and also affected the surface of the substrate. The substrate was kept at room temperature during the deposition. The deposited carbon film was so-called i carbon. Vicker’s hardness of the film, which was deposited on the Si substrate and 1.5 μm in thickness, was more than 3000 kg/mm2 for 10 g of load. When the ion beam contained hydrogen, diamond crystal particles of 0.1 to 1 μm in diameter were observed in an amorphous matrix. It was confirmed by electron diffraction analysis that the crystal particles had the cubic or hexagonal diamond structure. The ion bombardment gave shock-quenched conditions in a microscopic area. Sometimes it was observed that the particles exhibited well-defined morphology of the cubic diamond.
A quasi-direct-current sputtering technique for the deposition of dielectrics at enhanced rates
Authors: Este G. , Westwood W. D.
Published: July 2002

A new sputtering process with particular advantages for the deposition of dielectric films has been developed. Low-frequency power is applied between two conducting targets which are sputtered in a reactive gas. The operation has been demonstrated using Al planar magnetron targets in reactive gases as well as Ar and other noble gases, using a 60-Hz and a 80–500-kHz supply. Comparative measurements were made using the same system for both dc and 13.56-MHz operation. The process retains the controllability of reactive rf sputtering but with higher deposition rates. For N2 ambient, the AlN deposition rate at 100 kHz was 80% higher than the value for 13.56 MHz. Rate measurements were made as a function of both power and frequency by step height measurements. For all gases, the rate increased linearly with power for all frequencies; at a given power, the ratios of the rates obtained in Ar were ∼1:1:0.85:0.70:0.55 for dc, 60 kHz, 80 kHz, 500 kHz, and 13.56 MHz, respectively. The power dissipated in the targets was measured from cooling water temperatures and were proportional to the rates; at 13.56 MHz, ∼50% of the power is not dissipated in the targets. The higher target power dissipation makes the lower frequency operation more efficient for sputtering. The technique can be applied to different target/substrate geometries to deposit dielectric films at higher rates than in conventional rf sputtering.
Thin-film infrared absorber structures for advanced thermal detectors
Authors: Parsons A. D. , Pedder D. J.
Published: July 2002

Imaging thermal detector technology is a rapidly advancing field in which the current emphasis is towards the development of very large arrays of very small pyroelectric detector elements. For maximum responsivity, each of the thin pyroelectric elements (typically ≤25 μm thick) in an array must be provided with a thermal absorber to convert incoming infrared radiation into heat. This absorber must have a low thermal mass compared to the element and a high absorption efficiency to give the maximum responsivity. This paper describes one such absorber structure, comprising a thin metal film, impedance matched to free space, and a quarter-wave polymer film which offers an acceptably low thermal mass. The structure and properties of this thin-film absorber are compared with those of an electroplated platinum black absorber commonly used in thermal detectors. The theory of the absorber is presented and good agreement is shown between calculated and experimentally derived absorption spectra. Processing methods and tolerances for tailoring the spectral response to a desired specification are discussed.
Application of atomic force microscopy to magnetic materials
Authors: Grütter P. , Meyer E. , Heinzelmann H. , Rosenthaler L. , Hidber H.-R. , Güntherodt H.-J.
Published: July 2002

A new method of imaging the surface on a submicron scale is described and the observation of magnetic domain walls presented. Measurements in air on Co–Ni recording media and rapidly quenched Fe–Nd–B are shown. A resolution of better than 10 nm is achieved. This magnetic microscope is based on the idea of measuring magnetic forces with the recently developed atomic force microscope (AFM). Forces acting on a tip are recorded by the measurement of the deflection of a lever to which this tip is attached. The lever is made from a metallic foil with an integrated, electrochemically etched tip. Different measurement modes of the magnetic microscope are described. The images obtained by the AFM using a para- and ferromagnetic force sensor and by the STM are compared. Furthermore, results are compared with previous studies by the scanning electron microscope with polarization analysis and the Lorentz electron microscope. Finally, a concept is presented by which magnetic, topographic, and chemical information is simultaneously acquirable.
Axial distribution of optical emission in a planar magnetron discharge
Authors: Gu Lan , Lieberman M. A.
Published: July 2002

We measure the axial distribution S of optical emission in a dc planar magnetron discharge for various currents I, voltages V, and magnetic fields B. We develop an integral equation model of the distribution, which is in good agreement with the measurements. At fixed I, we find that the position Δ from the cathode of the peak in emission Smax scales as the ion Child law sheath thickness Δ∝V7/8/B1/4, and that for small B’s, Smax ∝B/V1/2.
Characterization of a new reactor for remote plasma chemical vapor deposition
Authors: Huelsman Alan D. , Reif R.
Published: July 2002

A remote plasma metalorganic chemical vapor deposition (CVD) system was designed, constructed, and characterized mathematically and experimentally. The system uses a new unique reactor geometry which is particularly well suited to remote plasma CVD. GaAs was grown in the system with and without a rf plasma and the results compared for various electrode geometries. The plasma reduced the activation energy for growth from 18 kcal/mol without plasma to 14 kcal/mol with plasma and increased the growth rate by as much as two orders of magnitude between the temperatures of 500 and 600 °C. The rf electrode geometry and the distance between the plasma and the wafer were the most critical parameters in determining the growth rate with plasma.
Reflection of hydrogen atoms from metal and semiconductor targets
Authors: Melnychuk S. T. , Seidl M. , Carr W. , Isenberg J. , Lopes J.
Published: July 2002

Partially cesiated Si and Mo targets have been exposed to a flux of atomic hydrogen produced by thermal dissociation of hydrogen gas on a heated tungsten mesh. Hydrogen atoms in the tail of the distribution are elastically reflected from the surface, and some fraction are negatively ionized by electron transfer from the surface. The H− energy distributions and the ion yields have been measured. The backscattered H− ions have a Maxwellian energy distribution with a temperature equal to the atomic gas temperature. The ion yield depends exponentially on the inverse temperature of the gas. The highest measured yield is ∼0.01 for T=0.21 eV on Si. Monte Carlo calculations of the ionized and neutral fractions using the probability model of Rasser et al. are in good qualitative agreement with experimental results. Calculations show that most H− ions formed near the surface do not have enough kinetic energy to overcome the potential barrier due to the image charge interaction.
Reactive magnetron sputtered zirconium oxide and zirconium silicon oxide thin films
Authors: Russak Michael A. , Jahnes Christopher V. , Katz Eric P.
Published: July 2002

Thin films of ZrO2 and ZrO2–SiO2 were deposited by reactive dc magnetron sputtering. The optical properties, density, microstructure, and crystalline phase of pure ZrO2 films were found to be a function of deposition rate. In particular, the index of refraction could be varied from 1.77 to 2.13 by increasing the deposition rate from 11 to 720 Å/min. The density of the films increased from 3.9 to 5.8 g/cm3 over the same deposition rate range. Small amounts of SiO2 (10 at. %) stabilized the mixed films in an amorphous phase. A linear relationship between index of refraction and SiO2 content was observed and, as in the case of pure ZrO2, increasing deposition rate resulted in mixed films with higher densities and indices for a fixed SiO2 content. The structure and optical properties of the mixed films remained unchanged with thermal cycling up to 500 °C.
Plasma enhanced chemical vapor deposition using forced flow through hollow cathodes
Authors: Jansen Frank , Kuhman Dan , Taber Charles
Published: July 2002

The application of hollow cathodes to the deposition of thin films from molecular gases is discussed. Precursor gases are decomposed in glow discharges created in the hollow cathode tubes while a laminar viscous gas flow is maintained through the tube towards a substrate. Either the substrate or another structure external to the hollow cathode, such as a coaxial tube, may function as the anode. Deposition rates up to 30 μ/min are observed for a-Si:H. These high-deposition rates are attributed to the high power density in the plasma combined with the efficient transport of the radicals to the substrate. A coaxial hollow cathode arrangement allows the deposition of insulating films by a direct current process. The unusual properties of amorphous silicon and silicon nitride films deposited with these electrode structures are discussed.
The state of residual stress in TiN films made by physical vapor deposition methods; the state of the art
Authors: Perry A. J.
Published: July 2002

Existing transmission electron microscope studies indicate that a variety of lattice defects such as dislocation loops, ultramicrocracking, and trapped argon and its precipitation can be present in thin TiN films, where the precise defects observed in a given sample depend on the deposition conditions of the film. There are also changes in texture and grain size as the film thickness increases. A considerable amount of data has also been reported on the lattice parameters, diffraction peak widths (which indicate the strain distribution), and x-ray diffraction (XRD) residual stress, which are all found to depend strongly on the deposition conditions of TiN films. These properties also change through the thickness of the film. In the present work, existing XRD data and their trends are reviewed. While it is clear that correlations exist between the XRD data and microscopic and microstructural changes, it is not yet possible to relate them to specific microstructural features or lattice defects. The state of residual stress and the strain distribution are different on different planes in a given film. They also appear to be affected by texture and by the nature of the substrate in a way that cannot yet be classified.
Fundamentals of ion-beam-assisted deposition. II. Absolute calibration of ion and evaporant fluxes
Authors: Hubler G. K. , Van Vechten D. , Donovan E. P. , Carosella C. A.
Published: July 2002

A method is given to obtain an absolute calibration of the ion and evaporant fluxes in an ion-beam-assisted deposition system based upon a Kaufman ion source and an electron beam vapor source. The nitrogen-ion silicon-vapor material system is used for the calibration; Rutherford backscattering is used for measurement of composition and thickness of Si1−x Nx films deposited on C and Si substrates. It is shown that quantitative predictions of the ion-to-atom impingement ratio, film composition, and film thickness can be obtained when sputtering, reflection, charge exchange neutralization of the ions, and species content of the nitrogen beam are considered.
Thermal roughening studied by scanning tunneling microscopy
Authors: Frenken J. W. M. , Hamers R. J. , Demuth J. E.
Published: July 2002

We have used scanning tunneling microscopy to observe the thermal roughening transition at the Ag(115) surface. For this purpose, a scanner and crystal assembly was employed that minimizes the lateral thermal drift of our microscope. Images were taken from room temperature, where the surface was smooth, up to 260 °C, where the surface is in the rough state. The topographs vividly demonstrate how the stepped metal surface goes through its roughening transition by the proliferation of kinks in the step edges. The roughening temperature of Ag(115), TR, is estimated to be 78±20 °C.