bluuebunny/crossref_metadata_2025 huggingface dataset:
Iron XPS Spectra from the Physical Electronics Model 5400 Spectrometer
Authors: Mansour A. N. , Brizzolara Robert A.
Published: July 2002

Iron spectra were measured with the Physical Electronics Model 5400 x-ray photoelectron spectrometer using unmonochromated Mg Kα x-rays at three pass energy settings corresponding to analyzer energy resolutions of 1.34, 0.54, and 0.13 eV. The specimen is a high purity 0.25 mm thick iron foil that was obtained from Johnson Matthey and was sputter-cleaned by 3 keV Ar ions for 10 min. We present the survey spectrum (binding energy range of 0–1100 eV) measured at an analyzer energy resolution 1.35 eV. Multiplexes of the Fe 2p (700–730 eV), Fe 3p (45–65 eV), valence band region (−5–20 eV), and Fe LVV auger lines (525–570 eV) were measured at analyzer energy resolutions of 0.54 and 0.13 eV.
MnO2 by XPS
Authors: Stranick Michael A.
Published: July 2002

Manganese compounds have many applications in areas such as catalysis, electrochemistry, and metallurgy, among others. Distinguishing between the various chemical states of manganese is an important aspect of research in many of these areas. It has been shown that the different chemical states of manganese can be identified with XPS through the Mn 2p3/2 peak positions, Mn 2p1/2 satellite–Mn 2p1/2 peak separations, Mn 3s multiplet splittings, or Mn Auger parameters. To date, however, all of these values have not been available in a single reference. In this study, XPS has been used to obtain core level, Auger, and valence band spectra for a commercial, high purity MnO2 powder. This submission provides a reference that contains all of the Mn XPS data necessary for the identification of MnO2 and also provides information that may be useful for the analysis of other Mn compounds.
Whitlockite (β-Ca3(PO4)2) Characterization by XPS: An Environmentally Important Mineral
Authors: Eighmy T. Taylor , Kinner Amy E. , Shaw Elisabeth L. , Eusden J. Dykstra , Francis Carl A.
Published: July 2002

Whitlockite (β-Ca3(PO4)2) is an environmentally important secondary phosphate mineral. It is of significance geochemically around ore bodies, and in soil, sedimentary, and waste systems. We have used XPS to study the binding energy of primary photoelectrons from air-exposed rhombohedral whitlockite crystals. The sample is from Groton, New Hampshire and is part of the Harvard University Mineralogical Museum’s collection. General survey and high-resolution spectra were collected using a Perkin Elmer Physical Electronics 5200C spectrometer. Adventitious carbon was used for energy referencing. Charge corrected binding energies for the photoelectrons present in whitlockite (Ca 2p3/2, Ca 2p1/2, P 2p3/2, P 2p1/2, P 2s, and O 1s) are reported. Additionally, charge corrected binding energies for the photoelectrons of other elements present in the natural sample are reported (Pb 4f7/2, Pb 4f5/2, and Si 2p). The Pb is likely an isomorphic substitution for Ca in the whitlockite, and the Si is from the host quartz. The reported binding energies are useful in identifying environmentally important calcium-phosphate minerals such as whitlockite in ore bodies, soils, sediments, and phosphate-stabilized waste systems.
Plumbogummite (PbAl3(PO4)2(OH)5⋅H2O) Characterization by XPS: An Environmentally Important Secondary Mineral
Authors: Eighmy T. Taylor , Kinner Amy E. , Shaw Elisabeth L. , Eusden J. Dykstra , Francis Carl A.
Published: July 2002

Plumbogummite (PbAl3(PO4)2(OH)5⋅H2O) is an environmentally important secondary phosphate mineral. We have used XPS to study the binding energy of primary photoelectrons from the air-exposed surface of a sample of dull blue botryoidal or tuberose masses. The sample is from Cumberland, England and was supplied by Excalibur-Cureton Mineral Company. General survey and high-resolution spectra were collected using a Perkin Elmer Physical Electronics 5200C spectrometer. Charge corrected binding energies for the Pb 4f7/2, Pb 4f5/2, P 2p3/2, P 2p1/2, O 1s, and Al 2p photoelectrons are reported. Two species of Pb were observed; likely representing a mixture of both plumbogummite and PbO. Additionally, charge corrected binding energies for Si 2p are reported. The Si is from the host quartz. The reported binding energies are useful in identifying environmentally important lead-phosphate minerals such as plumbogummite in ore bodies, soils, sediments, and phosphate-stabilized waste systems.
Chlorapatite (Ca5(PO4)3Cl) Characterization by XPS: An Environmentally Important Secondary Mineral
Authors: Eighmy T. Taylor , Kinner Amy E. , Shaw Elisabeth L. , Eusden J. Dykstra , Francis Carl A.
Published: July 2002

Chlorapatite (Ca5(PO4)3Cl) is an environmentally important secondary phosphate mineral, one of the apatite family of minerals. It is of significance geochemically in ore, soil, sedimentary, and waste systems. We have used XPS to study the binding energy of primary photoelectrons from the powder of a well-fractured massive block sample. The sample is from Telemark, Norway and is part of the Harvard University Mineralogical Museum’s collection. General survey and high-resolution spectra were collected using a Perkin Elmer Physical Electronics 5200C spectrometer. Adventitious carbon was used for energy referencing. Charge corrected binding energies for the photoelectrons of chlorapatite (Ca 2p3/2, Ca 2p1/2, P 2p3/2, P 2p1/2, P 2s, O 1s, Cl 2p3/2, and Cl 2p1/2) are reported. The charge corrected binding energy for Si 2p photoelectrons of either isomorphically substituted silicate (e.g., Ca5(PO4,SiO4)3Cl) or host quartz present in the natural sample is also reported. The observed binding energies are useful in identifying environmentally important calcium phosphate minerals such as chlorapatite in ore bodies, soils, sediments, and phosphate-stabilized waste systems.
Polarization effects and transport in AlGaN/GaN system
Authors: Zhang Yifei , Smorchkova Yulia , Elsass C. , Keller Stacia , Ibbetson James , DenBaars Steven , Mishra Umesh , Singh Jasprit
Published: July 2002

The AlGaN/GaN heterostructure is important for both electronic and optoelectronic devices. In addition to having a large band gap, the heterostructure has a strong piezoelectric effect and a large spontaneous polarization. This allows one to incorporate a large electric field (>106 V/cm) and high sheet charge (>1013 cm−2) without doping. Theoretical studies are done to examine how polarization effects controls the sheet charge density. The studies also focus on how interface roughness, aluminum mole fraction in the barrier, impurity scattering, sheet charge density, and phonon scattering influence mobility. Results are compared with experimental studies on samples grown by both molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD). We find that interface roughness is a dominant source of scattering in the samples reported. Due to the variation in growth techniques we find that the MBE samples have a smoother interface quality compared to the MOCVD samples. By carefully fitting the experimental data we present results on interface roughness parameters for MBE and MOCVD samples.
X-ray studies of group III-nitride quantum wells with high quality interfaces
Authors: Fewster P. F. , Andrew N. L. , Hughes O. H. , Staddon C. , Foxon C. T. , Bell A. , Cheng T. S. , Wang T. , Sakai S. , Jacobs K. , Moerman I.
Published: July 2002

This paper reports an investigation of a variety of (InGa)N/GaN multi-quantum-well (MQW) samples grown by metalorganic vapor phase epitaxy on sapphire substrates. Dynamical scattering theory has been used to simulate the x-ray diffraction profiles so as to model the structures and to assess the quality of the grown interfaces. There is good agreement between the theoretical predictions and the experimental data. A systematic comparison of a set of ten-period MQWs with different well widths is also reported together with a discussion of the comparison between a single quantum well (QW) with five- and ten-period MQWs all with the same well and barrier widths and alloy composition. The well and barrier widths deduced from the x-ray measurements agree within experimental error with those predicted from the growth parameters, however, the In content of the wells appears to be substantially lower than that expected. This is discussed in terms of a carbon incorporation model. In the better samples, the (InGa)N/GaN interface is good to within a few monolayers—this is comparable with the best that can be achieved in (AlGa)As/GaAs QWs.
Tunable Schottky barrier contacts to InxGa1−xAs
Authors: Marinelli C. , Sorba L. , Lazzarino M. , Kumar D. , Pelucchi E. , Müller B. H. , Orani D. , Rubini S. , Franciosi A. , De Franceschi S. , Beltram F.
Published: July 2002

Al/In x Ga 1−x As (001) diodes incorporating Si bilayers deposited under As or Al flux were fabricated by molecular-beam epitaxy on GaAs(001) wafers for 0.2<x<0.4. Schottky barrier heights as high as 0.75 eV and as low as −0.10 eV could be reproducibly obtained. Diodes engineered for high barrier height systematically showed a higher thermal stability than low-barrier diodes. We discuss the composition dependence of the barrier height and the observed degradation behavior vis-a-vis of the predictions of the interface-dipole model of Schottky barrier tuning.
Integration of chemical vapor deposition Al interconnects in a benzocyclobutene low dielectric constant polymer matrix: A feasibility study
Authors: Wickland Heidi , Talevi Robert , Bian Zailong , Nuesca Guillermo , Sankaran Sujatha , Kumar Kaushik , Geer Robert E. , Kaloyeros Alain E. , Liu Joyce , Hummel John , Shaffer Edward O. , Martin Steven J.
Published: July 2002

Results are presented from a proof-of-concept study that examined the integration of damascene-processed thermal chemical vapor deposited (TCVD) aluminum (Al) interconnects in a benzocyclobutene (BCB) polymer matrix. In a first phase, the study identified baseline deposition conditions for the formation of structurally and chemically compatible blanket Al/titanium nitride (TiN)/BCB stacks on two types of blanket BCB substrates utilized to simulate the actual surfaces encountered in typical damascene processing: (1) blanket BCB films capped with a silicon dioxide SiO2 layer (SiO2-BCB), and (2) plasma reactive ion etched blanket BCB films. The TiN diffusion barrier was grown in two stages. A first (bottom) layer was deposited by physical vapor deposition (PVD), followed by a CVD-grown top layer. The resulting TCVD Al/CVD TiN/PVD TiN/BCB stacks were stable under thermal stressing up to 325 °C for 1 h. In a second phase, an optimized TCVD Al process flow was developed for void-free filling of TiN-coated 320-nm-wide trenches etched in a BCB matrix. The process flow included the demonstration of a chemical mechanical polishing recipe for planarization of the patterned TCVD Al/CVD TiN/PVD TiN/BCB structures. The resulting findings were incorporated in the fabrication of electrically testable TCVD Al/CVD TiN/PVD TiN/BCB interconnect structures on 200 mm wafers. Electrical evaluation for shorting and leakage of the test dice produced an adequate yield for the feasibility study of ∼71% of screened test sites. The electrical tests also generated an upper-bound value of 4.2 μΩ cm for Al line resistivity, a number that did not include corrections for contact resistance and interfacial scattering. These findings demonstrate the feasibility of TCVD Al/BCB based metallization schemes, particularly in terms of chemical, structural, mechanical, and electrical performance.
Gas-Metal Reactions of Refractory Metals at High Temperature in High Vacuum
Authors: Fromm E.
Published: July 2002

The reactions of Nb, Ta, Mo, and W with the gases H2, N2, O2, H2O, CH4, and CO at high temperatures are discussed. Quantitative relations are compiled for the estimation of the minimum gas content attainable in vacuum metallurgical processes of both the degassing time and the metal loss due to oxide evaporation.
Reaction layer dynamics in ion-assisted Si/XeF2 etching: Temperature dependence
Authors: Sebel P. G. M. , Hermans L. J. F. , Beijerinck H. C. W.
Published: July 2002

We study the dynamics of the reaction layer during Ar+ ion-assisted Si etching by XeF2 in the temperature range T=150–800 K. Depending on temperature, the etch rate can be enhanced a factor of 8 by ion bombardment. The dynamics are studied with ion-pulse measurements on a time scale of 1–100 s in a molecular beam setup. A reaction layer with a submonolayer fluorine coverage and dangling bonds is found to be formed on the Si(100) surface during ion bombardment. The dangling bond concentration increases with ion flux and is independent of temperature in the range 150–600 K. Chemisorption on these dangling bonds results in a higher reaction probability of XeF2. The temperature dependence of the reaction probability of XeF2 is fully determined by the temperature dependence of the XeF2 precursor state. A simple model gives a very good description of the reaction probability as a function of both temperature and ion flux. The model description of the behavior of the precursor concentration as a function of ion flux and temperature is confirmed by ion pulse measurements on a time scale of 1 s. Further, it is concluded that the mechanisms for enhanced SiF4 formation during ion bombardment are the same over the temperature range studied.
Application of Dry-Pumped Systems Operating above 10−5 Torr
Authors: Smith Hugh R.
Published: July 2002

Dry-pumped systems using various combinations of ion, titanium sublimation, and cryogenic pumping are now widely accepted in vacuum processes utilizing pressures below 5×10−5 Torr. High-capacity, dry-pumped systems have now been proven which operate at much higher pressures. This paper discusses the design of these high-capacity, dry-pumped systems for evaporation and melting and refining processes. A variety of titanium evaporation pumping systems—using wire, rod, and ingot-feed systems, with large titanium inventories for continuous operation—are discussed. A high-throughput titanium sublimation pumping system is described, along with its high-pressure operating characteristics, which offers more economical pumping for large gas loads. Conventional inert gas pumping systems are described for use with these high-throughput titanium sublimation systems, to meet particular requirements.
Behavior of the Bayard–Alpert Gauge with Cage Modulator Operating without Electron Current
Authors: Szwemin P. J.
Published: July 2002

Besides the classical method of ion current modulation there are other modes applied to the BAG with modulator. In the new method (proposed by Groszkowski) the cage modulator is operated without electron current, while reasonable high modulation factor is obtained. The behavior of this gauge is presented in a wide range of pressures for both noble and active gases. The comparison of the classical method with the new one is also given. The new method allows elimination of adsorption and desorption processes from the modulator as a main disadvantage of the classical method.
Preparation and Transport Properties of Vacuum Evaporated Selenium Films
Authors: Tabak M. D. , Hillegas W. J.
Published: July 2002

The transport properties of vacuum evaporated films of “pure” selenium and selenium doped with small quantities of Cl (0–40 ppm) and As (∼12at.%) have been examined using a time-resolved drift technique. Addition of Cl alone acts as an electron trap, and addition of As alone acts as a hole trap while greatly increasing the electron free-carrier lifetime. When used in combination, controlled addition of these two impurities can be used to produce hole ranges greater than 7.5×10−6 cm2/V and electron ranges greater than 1.2×10−6 cm2/V in the same film. This hole range is approximately a factor of 3 greater and the electron range a factor of 5 greater than that observed in the best pure Se films.
Vacuum Measurements on the Lunar Surface
Authors: Johnson Francis S. , Carroll James M. , Evans Dallas E.
Published: July 2002

Measurements of neutral gas pressure on the lunar surface have been made with a cold cathode ionization gauge carried to the moon by Apollo 14. The vacuum quality at the landing site is much influenced by the adsorption of rocket gases and their later release. During surface operations by the astronauts, the pressure was near 10−8 Torr. No data were obtained between the time of the surface operations and lunar sunset about 12 days later, at which time the temperature fell rapidly to the vicinity of 100 K. The pressure was about 10−12 Torr shortly after sunset, but intermittent releases of gas, perhaps from within the moon itself, occasionally raised the pressure by less than an order of magnitude for as long as a day or two at a time and on one occasion to about 10−10 Torr for about an hour. At lunar sunrise, as the surface was warmed rapidly to about 300 K, the pressure rose rapidly to about 10−10 Torr, most likely due to the release of absorbed gases in the immediate landing area or on the landing module itself. For comparison with interplanetary vacuum conditions, the directed pressure of the solar wind is usually less than 10−11 Torr and the pressure of random gas motion within the solar wind, less than 10−13 Torr.
Structure Modification by Ion Bombardment during Deposition
Authors: Mattox D. M. , Kominiak G. J.
Published: July 2002

It is shown that continuous or intermittent ion bombardment during deposition can change the growth mode of thick deposits formed by sputtering or evaporation. The columnar morphology commonly found when deposits exceed 1 μ in thickness can be disrupted and the deposit densified by negatively biasing the deposit and subjecting it to ion bombardment during growth. This effect is found to occur in a number of metal systems and may be attributed to resputtering during growth. In the case of sputter deposited tantalum, the density of 6-μ thick films can be increased from 14 g/cm3 at 0 deposit bias to 16.3 g/cm3 at −500-V bias. The macroscopic stress in the deposited film is also shown to be a function of the deposit bias. It is proposed that this growth habit modification may also be obtained in sputter deposited nonmetallic materials and chemical vapor deposits by ion bombarding the deposit during growth.
Charge Transfer Devices
Authors: Tompsett M. F.
Published: July 2002

This is a review describing the use of charge transfer devices for digital memory, analog delay, and image sensing. Short descriptions of different types of charge-coupled devices and MOS bucket-brigade devices are presented. Those factors such as transfer inefficiency, noise, and dark current which affect the performance of these devices in the above applications are discussed. Various possible organizations of charge transfer devices to serve different functions are described. Many charge transfer devices have been fabricated and already indicate a high degree of achievement. Transfer inefficiencies per transfer in the range 10−3 to 10−4 have been measured. Finally, it is projected that charge transfer devices will rapidly find their way into certain analog delay, image sensing, and digital applications.
Equations for Thermal Transpiration
Authors: Siu M. C. I.
Published: July 2002

A formalism for analytically obtaining an expression for the thermal transpiration pressure ratio R is presented. An experimental parameter σ, which is associated with the type of molecule-solid surface collisions, is introduced. A completely diffuse scattering and a completely specular scattering from a solid surface correspond to σ = 0 and σ = 1, respectively. A known distribution function is used to derive a practical formula for R in the case of long tubes and very low pressures. Quantitative results obtained from this formula indicate that deviations from completely diffuse scattering of molecules from solid surfaces give rise to an anomalous Knudsen limit.
The Influence of Soda-Lime Substrate Ion Drift on the Resistance of Discontinuous Thin Gold Films
Authors: Morris J. E.
Published: July 2002

Conductance drift with time at high fields has been observed with discontinuous gold films on soda-lime substrates. The effect is attributed to ion drift in the substrate between metal islands which gives rise to (i) a small retarding field along the film which modifies current flow at low applied fields, and (ii) a reduction in the trap density within the tunneling barrier which leads to significant increases in film resistance at high fields.
dc Bias-Sputtered Aluminum Films
Authors: Blachman A. G.
Published: July 2002

Low resistivity aluminum films have been deposited by dc bias sputtering without excessive presputtering. Minimum resistivity occurs for a bias (VB) of approximately −40 V and, in contrast to the case for sputtered molybdenum, the resistivity increases for higher negative biases. For as-deposited 6500-Å films, resistance ratios (R.T./4.2 K) greater than 20 were obtained for VB=−40 V, indicating a minimum resistivity within 5% of bulk. Total (tensile) stress for these same films (deposited at substrate temperatures of 120–200 C) is ∼+1.5×109 dyn/cm2 for VB=−40 V, dropping to ∼+0.8×109 dyn/cm2 for VB=−125 to −150 V. The films exhibit an increasingly rougher surface for increasing negative bias, in contrast with sputtered molybdenum films, which show the opposite bias dependence.
The influence of bias on the depostion of metallic films in rf and dc sputtering
Authors: Cuomo J. J. , Gambino R. J. , Rosenberg R.
Published: July 2002

The effects of substrate bias on the electrical resistivity, accumulation rate, and impurity content of metal films deposited by rf and dc sputtering have been investigated. Some experimental techniques are described which make it possible to separate the effects of bias on resputtering, plasma density, and substrate temperature. The accumulation rate data as a function of bias have been analyzed in terms of a semiempirical equation. The analysis has elucidated the relative importance of bias-induced resputttering and plasma density changes in rf and dc sputtering.
Effect of pressure on the properties of reactively sputtered Ta2O5
Authors: Westwood W. D. , Boynton R. J. , Ingrey S. J.
Published: July 2002

Films of Ta2O5 have been prepared by reactive sputtering of tantalum in argon-oxygen dc glow discharges. Such films are of interest for capacitor dielectrics and optical waveguides, and for both applications the films must be free of pores. The effects of sputtering pressure on the density, refractive index, and dielectric constant of the films has been investigated. In the case of metal films, significant decreases in density are caused by increasing the sputtering pressure, a similar effect has been observed in the Ta2O5 case. The density decreases from 7.8 to 5.9 g/cm3 as the pressure is increased from 25 to 60 mTorr, and there are associated changes in related properties. The sputtering pressure can be controlled by adjusting the argon-oxygen mixture, but this also changed the deposition rate. Optical emission or mass spectrometry is used to ensure that the oxygen concentration is high enough for the deposition of Ta2O5 films rather than oxygen-doped tantalum; no emission from oxygen is observed until this concentration is reached.
Efficient modeling of thin film deposition for low sticking using a three-dimensional microstructural simulator
Authors: Smy T. , Dew S. K. , Joshi R. V.
Published: July 2002

Modern deposition methods for the thin metal films used in very large scale integrated diffusion barriers take advantage of nonunity sticking effects to produce more uniform coatings. Modeling these processes at the feature scale can be challenging due to long execution times which arise from the need to solve self-consistently for the transport of material in the feature. This article presents a methodology for substantially decreasing the execution time for low sticking coefficient simulations. The method is a modification of the traditional sequential Monte Carlo technique in which there is a separation of the transport processes and deposition process. This allows for a normalization of the incident flux magnitude before deposition and a substantial improvement in execution time. The article presents the incorporation of this method into a three-dimensional microstructural simulator, 3D-FILMS. The simulator is first used to confirm the accuracy of the new methodology and then assess its improvement over the more traditional algorithm. Finally, simulations for chemical vapor-deposited W and for sputtered Ti deposition are presented.
Ion compositions and energies in inductively coupled plasmas containing SF6
Authors: Goyette A. N. , Wang Yicheng , Olthoff J. K.
Published: July 2002

Inductively coupled plasmas were generated in pure SF6 and in Ar/SF6 and O2/SF6 mixtures in a Gaseous Electronics Conference rf reference cell. Absolute total ion current densities, relative ion intensities, and ion energy distributions at the grounded electrode were measured and the influences of pressure, power, and mixture concentration on these quantities examined. In addition to ions derived directly or indirectly from SF6, ions resulting from quartz etching and sulfur oxidation contribute moderately to the total ion flux. The dominant sulfur-containing ion observed under most conditions is S+, indicating a large degree of SF6 dissociation.
Structural and electrical characteristics of Y2O3 films grown on oxidized Si(100) surface
Authors: Cho M.-H. , Ko D.-H. , Choi Y. G. , Jeong K. , Lyo I. W. , Noh D. Y. , Kim H. J. , Whang C. N.
Published: July 2002

Heteroepitaxial Y2O3 films were grown on oxidized and clean Si (100) surfaces by ion assisted evaporation under an ultrahigh vacuum. The crystalline structure, crystallinity, morphology, and electrical properties were investigated using various techniques. The crystallinity assessed by x-ray diffraction and Rutherford backscattering spectroscopy shows that the films grown on the oxidized Si substrates have better crystallinity and smoother morphology compared to those on the clean Si. As the annealing temperature increases, the crystallinity and morphology are stable for the films grown on the oxidized Si, while those of the films grown on clean Si substrates degrade. The difference between the two films is attributed to the formation of hillocks and a chemical reaction at the interface between the film and SiO2. The low crystallinity, strain change, and the reaction of excess Y in the films grown on the clean Si contribute to the crystalline structure and the formation of hillock. These changes of crystallinity and morphology show that the films grown on the oxidized Si surface are more suitable for device applications. Thus, the films grown on the oxidized Si result in higher breakdown field strength and lower trap charge density than those on clean Si after the annealing treatment.
Effects of annealing of (Ba,Sr)RuO3 bottom electrodes on the electrical properties of (Ba,Sr)TiO3 thin films
Authors: Park Kyung-Woong , Park Jeong-Hee , Oh Se-Hoon , Kim Boum-Seock , Chung Yong-Chae , Choi Duck-Kyun , Yoo Cha-Young , Park Young-Wook , Lee Sang-In
Published: July 2002

The annealing of (Ba,Sr)RuO3 films which are structurally and chemically matched with (Ba,Sr)TiO3 films was performed in oxygen and nitrogen atmospheres in the temperature range of 600–750 °C for 30 min. The effects of annealing the (Ba,Sr)RuO3 on the physical and electrical properties of the (Ba,Sr)TiO3 films were investigated. The x-ray diffraction peak of the annealed (Ba,Sr)RuO3 film at high temperatures revealed that the (Ba,Sr)TiO3 film is thermally more stable than RuO2. The (Ba,Sr)RuO3 film under N2 annealed showed lower electrical resistivity and larger surface roughness compared with those under O2. In addition, from the sequential two-step annealing process using O2 and N2, and by reversing the annealing sequence, the electrical resistivity and the surface roughness of the (Ba,Sr)RuO3 film turned out to be reversible. The (Ba,Sr)TiO3 film on the N2 annealed (Ba,Sr)RuO3 showed a higher leakage current than that on the O2 annealed bottom electrode because rough surface can cause a high local electric field. The dielectric constant of the (Ba,Sr)TiO3 thin film increased with the annealing temperature of the (Ba,Sr)RuO3 bottom electrode regardless of the annealing atmosphere.
Modeling and simulation of feature-size-dependent etching of metal stacks
Authors: Abdollahi-Alibeik Shahram , Zheng Jie , McVittie James P. , Saraswat Krishna C. , Gabriel Calvin T. , Abraham Susan C.
Published: July 2002

Aspect ratio dependent etching (ARDE) has often been observed in various etching processes. During etching of metal films in a high density plasma reactor, this phenomenon is more prominent. With a high amount of ARDE present, the narrow spaces will not be cleared unless there is enough overetch, which removes an excessive amount of the underlying layers. The main focus of this article is on the understanding of the mechanisms behind metal ARDE. The results from an extensive design of experiments on the subject were utilized for this study. SPEEDIE, the Stanford etching and deposition profile simulator, was used to develop and test appropriate models. The Langmuir adsorption model with added surface recombination of the adsorbed species, both etchants and inhibitors, was used to model the phenomenon. The added surface recombination acts as the major species loss mechanism on the feature sidewalls. The simulation results indicate that a process with inhibitors, which are highly adhesive to the metal surface and which do not like to recombine with the etchants to form volatile products, will lead to a low degree of ARDE. This is in agreement with experimental results which showed that the addition of CHF3 to the Al etch process helps to reduce the ARDE in narrow space regions.
Microstructure and tribological performance of MoSx/Au co-sputtered composites
Authors: Simmonds M. C. , Savan A. , Pflüger E. , Van Swygenhoven H.
Published: July 2002

Co-sputtered thin films of MoSx with Au have been deposited in order to investigate the relationships between tribological behavior and film microstructure. The mechanical properties of the composite films were investigated by pin-on-disk wear testing in 50% relative humidity air as a function of Au concentration. X-ray diffraction measurements indicate that the microstructure is strongly affected by the inclusion of Au and that there is a strong correlation between microstructure and tribological performance.
Low temperature deposition and characterization of polycrystalline Si films on polymer substrates
Authors: Xu K. , Shah S. I. , Guerin D.
Published: July 2002

Polycrystalline Si films were deposited on poly(ethyleneterephthalate) (PET-Mylar®) and glass (7059 Corning) substrates at 140 and 200 °C, respectively. X-ray diffraction and Raman spectroscopy were used to confirm the polycrystalline nature of the films. The largest grain size obtained was 95 nm. Raman spectroscopy also showed a simultaneous presence of an amorphous phase. The relative fraction of this amorphous phase was controllable by adjusting the composition of the sputtering gas. Films deposited with only Ar or Ar+H2 sputtering gas show a very small polycrystalline Si peak. With the addition of up to 10% Kr to the gas mixture, a very strong polycrystalline peak appears in the Raman spectra. X-ray diffraction also confirmed the polycrystalline nature of the films. The Kr effect was related to the energetic condensation. The presence of Kr increased the energy of the sputtered atoms. Even after collision with the sputtering gas, these atoms impinge on the substrate surface with enough residual energy that the ad-atoms experience enhanced diffusion, which leads to polycrystalline film formation. For our system, the final energy of the ad-atoms was calculated to be 1.92 eV, which is more than the activation energy for surface self-diffusion for Si.
Reaction kinetics on supported model catalysts: Molecular beam/in situtime-resolved infrared reflection absorption spectroscopy study of the CO oxidation on alumina supported Pd particles
Authors: Libuda J. , Meusel I. , Hoffmann J. , Hartmann J. , Freund H.-J.
Published: July 2002

By combining molecular beam techniques and time-resolved infrared reflection absorption spectroscopy (TR-IRAS) we have studied the kinetics of the CO oxidation reaction on an alumina-supported Pd model catalyst. The Pd particles are deposited by metal evaporation under ultrahigh vacuum conditions onto a well-ordered alumina film, prepared on a NiAl(110) single crystal. Particle size, density, and structure of the Pd deposits have been characterized in previous studies. In the low temperature region, transient and steady-state experiments have been performed over a wide range of CO and oxygen fluxes by crossing two effusive molecular beams on the sample surface. We determine the steady-state CO2 production rate as a function of the CO fraction in the impinging gas flux. Simultaneously, the occupation of CO adsorption sites under steady-state conditions is monitored by in situ infrared spectroscopy. The origin of different types of CO2 transients is discussed. In particular we focus on the transient CO2 production after switching off the CO beam. For the model catalyst investigated, detailed reaction rate measurements in combination with TR-IRAS show that the origin of the particular transient behavior of the supported model system is not due to the presence of specific adsorption sites on small particles, as has been proposed previously. Instead, we suggest that the transient behavior is a consequence of the inhibition of the dissociative adsorption of O2 at high CO coverage. Additionally, the inherent heterogeneity of the supported particle system can enhance the observed effect.
Radio-frequency transient match monitoring using a fast Fourier transform for plasma diagnosis
Authors: Kim Byungwhan
Published: July 2002

Anomalies in an equipment plasma are diagnosed by monitoring transient data filtered through a fast Fourier transform (FFT). The anomalies were experimentally simulated with variations in process factors, including source power, pressure, and Ar flow rate. A real-time match network monitoring system was used to collect radio-frequency match data and match positions were utilized as signatures representing certain changes in plasma states. The FFT position provided better diagnostic sensitivity than the statistically characterized one, which was more apparent when factor effects on steady plasma were less significant.
Waveguide structure of Er-doped KTiOPO4 films on different substrates by pulsed-laser deposition
Authors: Wang Ke-Ming , Shi Bo-Rong , Cue Nelson , Zhu Yong-Yuan , Xiao Rong-Fu , Lu Fei , Hu Hui , Liu Yao-Gang
Published: July 2002

Er-doped KTiOPO4 films on different substrates were made by pulsed-laser deposition. Substrates included Al2O3, MgO, and KTiOPO4. Both KTiOPO4 and erbium were used as targets. The composition of the Er-doped KTiOPO4 films on the different substrates was analyzed by Rutherford backscattering with 2.1 MeV He2+. The results show that there is deficiency of K and P in the deposited KTiOPO4 film on the different substrates. The prism coupling method was used to determine the relative intensity of scattered light versus the effective refractive index. The measurement indicates that there are waveguide structures in all cases.
Magnetoresistance characteristics of NiFe/Cu/CoFe/IrMn spin valves at elevated temperature
Authors: Tanoue S. , Tabuchi K.
Published: July 2002

We present magnetoresistance (MR) characteristics of 50 Å Ta/40–80 Å NiFe/22 Å Cu/20 Å Co90Fe10/150 Å Ir20Mn80/50 Å Ta spin valves with temperatures ranging from 298 to 570 K in view of free layer NiFe thickness. The MR ratio (=ΔR/R) for a 40 Å NiFe spin valve showed the highest value among the other thicker NiFe spin valves between 298 and 480 K. A nearly linear decrease in the MR ratio was observed between 298 and 480 K in all spin valves and the temperature coefficients of the MR ratio increased with decreasing NiFe thickness and the values were −0.0173, −0.0134, and −0.0111 %/K for 40, 60, and 80 Å NiFe spin valves, respectively. The characteristic temperature T0SV which was deduced to extrapolate to zero ΔR/R were dependent on NiFe thickness and the T0SV were determined to be 644, 690, and 639 K for 40, 60, and 80 Å NiFe spin valves, respectively. Above 510 K, a steep decrease in ΔR/R was found as a result of the combination of the free layer NiFe loop and the pinned layer CoFe loop due to the reduced CoFe/IrMn exchange coupling field. The exchange coupling field of CoFe/IrMn also showed the linear decrease with increasing temperature. The blocking temperature which were deduced to extrapolate to zero exchange coupling field were determined to be 519, 524, and 499 K for 40, 60, and 80 Å NiFe spin valves, respectively.
Investigation of the adhesion, friction, and wear properties of biphenyl thiol self-assembled monolayers by atomic force microscopy
Authors: Liu Huiwen , Bhushan Bharat , Eck Wolfgang , Stadler Volker
Published: July 2002

A comparative study of the tribological properties of self-assembled 1,1′-biphenyl-4-thiol monolayer (BPT) and cross-linked BPT monolayer (BPTC) is presented. BPT monolayers were prepared on a gold substrate by spontaneous self-assembly of biphenylthiol in solution. The cross-linking of BPT was carried out by low energy electron irradiation. Structural characterization by infrared spectra shows that chemical bonds were formed between neighboring phenyl groups after irradiation. The topography, adhesion, friction, and wear properties of BPT and BPTC were studied by atomic force microscopy with silicon nitride and diamond tips. Au(111) and Si(111) substrates were also investigated for reference. Both BPT and BPTC exhibited lower adhesion and friction than Au(111) and Si(111). Cross-linking resulted in a decrease of the adhesive force, whereas the coefficient of friction is increased. The wear resistance of BPT and BPTC slid against a diamond tip were almost identical in the tested range. It appears that cross-linking makes the coating more hydrophobic with no apparent improvement in friction and wear. The study also found that the roughness of different films make different contributions to friction. For Au(111) and BPTC, friction is only affected by surface slope, but for BPT the higher height surface areas have low friction. The changes of surface height and friction force for BPT monolayers with scan times were also investigated. A relationship between the wear resistance of the low friction phase of BPT and its size was found.
Effects of excess oxygen introduced during sputter deposition on carrier mobility in as-deposited and postannealed indium–tin–oxide films
Authors: Kikuchi Naoto , Kusano Eiji , Kishio Etsuro , Kinbara Akira , Nanto Hidehito
Published: July 2002

Electrical and structural properties of indium–tin–oxide (ITO) films with various Sn concentrations deposited under a high oxygen partial pressure were examined to find out how the excess oxygen behaves as a scattering and trapping center of electron carriers and to show evidence that excess oxygen is weakly bound with Sn4+ ions on In3+ sites with single-charge SnIn•. ITO films with Sn concentrations of 1–25 wt % were deposited on glass substrates by rf sputtering under various oxygen concentrations in the discharge gas (0.3%–100%); the substrate temperature was kept at 773 K during deposition. With increasing O2 flow ratio in the discharge gas from 0.3% to 100%, the Hall mobility and the carrier density were found to decrease from ∼40 to ∼20 cm2 V−1 s−1 and from ∼5.0×1020 to ∼2.0×1018 cm−3, respectively. The dependence of the slope of mobility–temperature curve on the O2 flow ratio and Sn concentration has been examined. For high Sn concentration, the slope changes from negative to positive as the O2 flow rate increases. The slope of the curve for a film with Sn concentration of 8 wt % deposited at an O2 flow ratio of 100% changes from positive to negative after postannealing at 473 K for 30 min. in N2. These results suggest that the oxygen attaches weakly to Sn4+ and that the oxygen plays a role in the scattering and trapping center. It is also found that oxygen ions mainly exist not in interstitial quasianion sites but in the grain boundaries because of the constant lattice parameter after annealing.
Epitaxial CrN(001) Grown and Analyzed In situ by XPS and UPS. II. Analysis of Ar+ Sputter Etched Layers
Authors: Haasch R. T. , Lee T. -Y. , Gall D. , Greene J. E. , Petrov I.
Published: July 2002

X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS) were used to study epitaxial CrN(001) grown in situ which were Ar+ sputter etched. The films were deposited on MgO(001) at 650 °C in pure N2 discharges maintained at a pressure of 5 mTorr (0.67) and shown to have a N/Cr ratio of 1.04 ± 0.02 by Rutherford backscattering (RBS). The films were sputter etched with 3 keV Ar+ at an angle of 40° to a constant nitrogen-to-chromium ratio. A Mg Kα x-ray source was used to obtain the XPS data, while the UPS data was generated by He I and He II UV radiation. The sputter etched films were found to have a N/Cr ratio, as determined by XPS, of 0.63, a decrease of 29% of that determined from the as-deposited surface. This indicates a preferential removal of nitrogen from the sputtered layers.
Chlorosilane adsorption on clean Si surfaces: Scanning tunneling microscopy and Fourier-transform infrared absorption spectroscopy studies
Authors: Nishizawa Masayasu , Yasuda Tetsuji , Yamasaki Satoshi , Shinohara Masanori , Kamakura Nozomu , Kimura Yasuo , Niwano Michio
Published: July 2002

The initial adsorption processes of SiH2Cl2 on Si(111)-(7×7) and Si(100)-(2×1) surfaces have been investigated by using infrared absorption spectroscopy and scanning tunneling microscopy. We have found that dissociation reactions of SiH2Cl2 on these two surfaces are distinctively different. SiH2Cl2 adsorption on Si(111)-(7×7) takes place via Si–Cl bond breakage, while both Si–H and Si–Cl bonds of the SiH2Cl2 molecules are dissociated on Si(100)-(2×1).
Effects of wall contamination on consecutive plasma processes
Authors: Yasuda H. K. , Yu Q. S. , Reddy C. M. , Moffitt C. E. , Wieliczka D. M.
Published: July 2002

Plasma processes often go beyond the primary objectives focused on the substrate, or targeted materials. For instance, sputtered materials deposit on surfaces other than the substrate, and plasma deposition extends to the walls of the reactor. In the process of plasma polymerization, or plasma chemical vapor deposition (PCVD), every surface (not just the substrate surface) participates in the overall plasma deposition process. Consequently the chemical and physical natures of all surfaces within a reactor are very important factors that determine the fate of the PCVD process. The materials deposited on the wall surface (wall contaminants) are created in the previous run in a batch operation of PCVD. In a sequential plasma process, where plasma polymerization of trimethylsilane (TMS) was followed by plasma polymerization of hexafluoroethane (HFE), F-containing oligomers (low molecular weight compounds), created during the plasma polymerization of HFE in the previous run, remain on surfaces in the reactor. The wall contaminants were found to migrate to the new substrate (aluminum alloy) surface in the subsequent run upon the evacuation of the reactor. If an O2 plasma treatment is applied, F-containing organic compounds chemisorbed on the new substrate surface are converted to F-containing inorganic compounds, which decreases the plasma-ablatable F on the surface. If no O2 plasma treatment is applied, the F-containing organic compounds are exposed to the environment of the TMS plasma. From the viewpoint of the sequence of plasma processes, a new HFE/TMS sequence is created without the O2 plasma treatment. The HFE/TMS system (reversed order to the normal cycle) causes adhesion failure at the interface between the plasma polymers and the aluminum alloys, whereas the TMS/HFE system yields good adhesion of plasma deposited layers to the substrate and provides superior adhesion of a primer applied on the plasma polymer coating. This difference was created by the difference in handling of the wall contaminants.
Analysis of a Zirconium Diboride Single Crystal, ZrB2 (0001), by XPS
Authors: Singh R. , Trenary M. , Paderno Y.
Published: July 2002

X-ray photoelectron spectroscopy (XPS) was used to study the clean surface of ZrB2 (0001). The clean surface exhibits Zr 3d5/2 and Zr 3d3/2 peaks at 179.2 and 181.6 eV, respectively. However, angle resolved XPS indicated ZrO2 peaks at 183.5 and 185.7 eV at higher emission angles, indicating that further cleaning was necessary. After additional cleaning cycles, these oxide peaks were no longer observed at high emission angles. This result demonstrates the necessity to probe the near surface region with higher emission angles on very reactive surfaces, in order to completely establish the cleanliness of the surface.
Gas source molecular beam epitaxy of high quality AlxGa1−xN (0⩽x⩽1) on Si(111)
Authors: Nikishin S. , Kipshidze G. , Kuryatkov V. , Choi K. , Gherasoiu Ìu. , Grave de Peralta L. , Zubrilov A. , Tretyakov V. , Copeland K. , Prokofyeva T. , Holtz M. , Asomoza R. , Kudryavtsev Yu. , Temkin H.
Published: July 2002

Layers of AlxGa1−xN, with 0⩽x⩽1, were grown on Si(111) substrates by gas source molecular beam epitaxy with ammonia. We show that the initial formation of the Si–N–Al interlayer between the Si substrate and the AlN layer, at a growth temperature of 1130–1190 K, results in very rapid transition to two-dimensional growth mode of AlN. The transition is essential for subsequent growth of high quality GaN, AlxGa1−xN, and AlGaN/GaN superlattices. The undoped GaN layers have a background electron concentration of (2–3)×1016 cm−3 and mobility up to (800±100) cm2/V s, for film thickness ∼2 μm. The lowest electron concentration in AlxGa1−xN, with 0.2<x<0.6, was ∼(2–3)×1016 cm−3 for 0.5–0.7-μm-thick film. Cathodoluminescence and optical reflectance spectroscopy were used to study optical properties of these AlxGa1−xN layers. We found that the band gap dependence on composition can be described as Eg(x)=3.42+1.21x+1.5x2. p–n junctions have been formed on crack-free layers of GaN with the use of Mg dopant. Light emitting diodes with peak emission wavelength at 3.23 eV have been demonstrated.
Improved Auger electron spectroscopy sputter depth profiling of W/WNx and WSix layers on Si substrates
Authors: Goryachko A. , Krüger D. , Kurps R. , Weidner G. , Pomplun K.
Published: July 2002

We have investigated the effects of sample rotation and ion energy reduction on the quality of ion sputtering assisted Auger electron spectroscopy depth profiling of W/WNx and WSix films on polysilicon substrates. Rotation significantly improves both the depth resolution for W/WNx/Si samples and the sensitivity to oxygen inside the W/WNx film. Rotation does not have any effect on results for WSix/Si interfaces. Atomic force microscopy investigations show that the improved resolution for W/WNx/Si samples is due to reduced roughness of the sputtered surface when the sample is rotated. Reduction of the ion energy from 4 to 1 keV also improves the depth profiles of W/WNx films. The ion energy reduction in the same range leads to larger error in measured elemental concentrations for WSix films due to preferential sputtering. This reduction increases the depth resolution of Auger depth profiles in the case of polycrystalline WSix films, but does not change the depth resolution for amorphous WSix films.