bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-step deposition process of piezoelectric ZnO film and its application for film bulk acoustic resonators
Authors: Park Sang-Hyun , Seo Byeng-Chul , Yoon Giwan , Park Hee-Dae
Published: July 2002

In this article, a two-step deposition technique of piezoelectric zinc oxide (ZnO) film formation using radio-frequency (rf) sputtering and its successful applications for film bulk acoustic resonators (FBAR) are presented. Several critical sputtering process parameters such as deposition pressure, rf power, and O2 concentration were investigated to understand their impacts on the resulting crystal structures and surface morphologies of the ZnO films. The ZnO films formed by the two-step deposition have shown the growth characteristic of the strongly preferred orientation toward c axis. The FBAR with the ZnO films showed a large return loss of ∼50 dB at the center frequency of 1.49 GHz. It was also found that the impedance matching of the FBAR could be easily achieved by simply controlling the resonance area of the resonator.
Comparison of titanium oxide films grown on bare glass and boiled glass in 50% H2SO4 by metal-organic chemical vapor deposition
Authors: Jang H. K. , Whangbo S. W. , Chung Y. D. , Kim T. G. , Kim H. B. , Lyo I. W. , Whang C. N. , Wang C. H. , Choi D. J. , Kim T. K. , Lee H.-S.
Published: July 2002

Titanium oxide films were deposited on bare glass and boiled glass in 50% H2SO4 for 30 min at various substrate temperatures by metal-organic chemical vapor deposition. We investigated the effects of a substrate temperature between 300 and 550 °C on such properties as thermal stability, deposition rate, and chemical states of the films. The thickness of the films is independent of the substrate treatments. The deposition rate of the films is linearly decreased with increasing substrate temperature. Rutherford backscattering spectroscopy and x-ray photoelectron spectroscopy results indicate that the H2SO4 treated glass substrate is superior to the bare glass substrate in the suppression of out-diffusion of sodium and calcium through the TiO2 film till a substrate temperature of 500 °C. There exist only Ti3+ and Ti4+ oxidation states in the film regardless of a substrate temperature and substrate treatment. Ti3+ fractional composition are changed slightly between 0.11 and 0.17 and Ti4+ fractional composition are changed between 0.82 and 0.90 with varying substrate temperature.
Reactive deposition of compounds by a cavity-hollow cathode direct current sputtering system
Authors: Kazemeini Mehdi H. , Berezin Alexander A.
Published: July 2002

A new hollow cathode has been designed and applied in a reactive direct current (dc) sputtering system. This hollow cathode with an extra cavity (1.4 cm3) separates the reaction at the substrate from the reaction at the target surface and therefore prevents the target surface (cavity walls) to transit from the metallic sputter mode to the reactive sputter mode. This transition normally happens in reactive dc sputtering systems and it is the cause of a drastic drop in the deposition rate. The physical geometry of this cavity provides larger cathode walls and more efficient use of fast electrons and ions to produce large densities of sputtered and evaporated particles of the target metal. The development of this cavity-hollow cathode was facilitated by comprehensive structural and compositional analysis of some deposited films. By using pure titanium for the target and a mixture of 90%Ar/8%N2/2%O2 for the operating gas, some samples of titanium oxinitride films a few microns thick have been produced. At operating pressure of 0.05 Torr, the measured value for the cathode fall distance inside the cavity is 1.6 mm, showing that the pressure inside the cavity is much higher than the operating pressure in the reactor chamber. The current–voltage characteristics of this system exhibit a switching behavior from a nondischarge mode to a discharge mode with a negative resistance.
Combining advanced lithographic techniques and self-assembly of thin films of diblock copolymers to produce templates for nanofabrication
Authors: Peters Richard D. , Yang Xiao M. , Wang Qiang , de Pablo Juan J. , Nealey Paul F.
Published: July 2002

A technique to create templates for nanofabrication using thin films of diblock copolymers is discussed and demonstrated. Advanced lithographic techniques are used to create chemically patterned surfaces that manipulate the wetting behavior of diblock copolymer films and to guide the spatial microphase separation of the block copolymer domains. Guided microphase separation has great potential for application of block copolymer films in nanofabrication because of perpendicular orientation of the domains to the substrate and macroscopic perfection in the ordering of copolymer domains. Lithography allows for registration of the domains with the substrate for creating addressable arrays. Experimental implementation of the technique is demonstrated using extreme ultraviolet interferometric lithography, self-assembled monolayers of octadecyltrichlorosilane as imaging layers, and the self-assembly of films of symmetric poly(styrene-b-methyl methacrylate).
Direct-Current Electrical Breakdown of Thin Titania Films in High Vacuum
Authors: Bouchard K. G.
Published: July 2002

Electrical breakdown of thin (60–100 Å) titania films under high dc fields in high (10−9 Torr) vacuum is discussed. Titania coatings were applied to Al2O3 insulators, using the same process as in coating of Al2O3 microwave windows to reduce multipactoring. Recorded breakdown voltages and current dependence, along with the appearance of the coatings after testing, suggest the occurrence of a reduction of the titania films to a lower-order semiconducting oxide similar to what would happen in bulk titania. It is therefore evident that such coatings are not feasible on insulators subjected to high tangential dc fields.
Nucleation and Oriented Growth of Chemically Formed Sulphide and Oxide Films
Authors: Hecht G. , Herberger J. , Weissmantel C.
Published: July 2002

The kinetics of the sulphidation and oxidation of evaporated zinc and cadmium films in sulphur and oxygen have been investigated. Between 100 ° and 250 °C a rapid gas uptake occurs which may be described by k·log(t−t0). Subsequently, a slow reaction is observed, the time dependence being represented by a logarithmic expression or by a general power law of the type k·t1/n. Electron-optical and x-ray studies reveal a substantial effect of nucleation and recrystallization processes on the kinetics of the layer growth. The following phases of layer growth could be confirmed: (1) coating of the metal with a very thin (d ≈ 50 Å) nonoriented layer; (2) growth of oriented sulphide or oxide nuclei with diameters of 102–103 Å; (3) coalescence of these nuclei and formation of a coherent layer; in the case of CdS and CdO, formation of medium-size epitaxial crystallites; (4) formation of whiskers at elevated temperatures. (5) Measurements of zinc and cadmium single crystals gave similar results, but the reaction rate is much slower and the degree or orientation depends strongly on the pretreatment of the metal surfaces. The results show that nucleation and recrystallization processes affect considerably the kinetics of the formation of thin films on metals. From this it can be concluded that it is necessary to modify models of film growth, which in most cases are based on a homogeneous layer structure.
Relationship between Structure and Sputtering Parameters in NbN Films
Authors: Alessandrini E. I. , Sadagopan V. , Laibowitz R. B.
Published: July 2002

The structure of thin films of niobium nitrides was examined by reflection electron diffraction techniques. The nitride films were obtained by reactive rf sputtering of the niobium at different power levels and partial pressures of nitrogen. The films were deposited on oriented sapphire substrates maintained either at room temperature of at 400 °C. Crystal structures of three distinct phases were observed and identified as (1) α-bcc niobium with nitrogen in solid solution, (2) β-hexagonal Nb2N, and (3) δ-fcc NbN. In this study, the γ–Nb4N3 composition could not be obtained as a single phase but was always found to occur as a mixture with the δ phase. The films prepared at both high partial pressures of nitrogen and rf powers had strong textures that were dependent also on the film thickness. The electron-diffraction data showed that niobium nitride films with successive structure transformations similar to that in the bulk state can be realized and that the transformations can be correlated to the sputtering parameters used.
High-Performance Elastomer-Sealed Valves
Authors: Wheeler William R.
Published: July 2002

This paper discusses the design of elastomer-sealed valves whose outgassing rate is greatly reduced and whose reliability of operation, particularly at elevated temperatures, is enhanced. Outgassing rates of new valve designs are presented and compared with those of conventional designs. It is seen that a 15X improvement can be made. The effect of this improvement on performance of typical small-vacuum systems is displayed graphically. A design is shown utilizing Viton as the main seal gasket which results in reliable and long life at 200 °C with the valve open or closed. Test data are presented. The problems encountered at elevated temperature by previous designs are examined and explained. The general character of elastomer seals is also examined at some length in an attempt to improve our understanding of it.
Some Tests on Noncooled Zeolites
Authors: Luches A. , Zecca A.
Published: July 2002

Tests were performed to investigate the trapping and pumping properties of two kinds of zeolite as a function of temperature and duration of baking. Residual gas spectra were also recorded. The results showed that a vacuum system made up by a rotary pump and a noncooled zeolite trap can reach pressures down in the 10−6-Torr range without oil or water vapor contamination.
Gas Adsorption by Refractory Metal Single Crystals
Authors: Ageikin V. S. , Chuikov B. A. , Ptushinskii Yu. G. , Vas’ko N. P.
Published: July 2002

The results are considered of a mass spectrometric investigation of the low-pressure oxygen interaction with surfaces of tungsten and molybdenum single crystals of different crystallographic orientation. It has been established that oxygen thermodesorption occurs only in the form of unbound oxygen atoms (atomic phase) and a set of metal oxides (oxide phase); and that the oxygen quantities in the atomic and the oxide phases are comparable. A correlation is discussed between quantitative data on the surface concentration, the sticking probability and the adsorption heat of oxygen on tungsten, and the atomic structure of different faces of a single crystal. The problem is considered of a correspondence between the composition of thermodesorption products and that of the adsorbed film. Some data are also considered on the inhibition of the adsorption ability of the surface of the single crystal of tungsten in respect to carbon monoxide or nitrogen when that surface is partially covered with electronegative or electropositive adatoms. The analysis of the results shows that the inhibition effect of the adsorption ability largely depends on the charge state of the adatoms and the electron structure of the adsorbed molecules.
The Feasibility of Producing Superalloy Electroslag Remelted Hollows
Authors: Klein H. J.
Published: July 2002

The feasibility of producing electroslag remelted hollows is shown. In this work electroslag hollows of two superalloys, Hastelloy alloy X and Haynes alloy No. 718 were produced. The microstructure of the as-cast hollows was significantly finer than that of a comparable ESR solid ingot. The segregation ratio defined as the maximum concentration of an element divided by the minimum concentration of the element was 1.16 and 1.33 for molybdenum for the ESR hollow and solid ingot, respectively. Mechanical property results from ring rolled and cross rolled specimens indicated that wrought properties were achieved in both alloys when total reductions exceeded 43%–50%. An acceptable although not optimum microstructure was obtained, and the reasons for this are discussed.
The Role of Inclusions on Mechanical Properties in High Strength Steels
Authors: Hauser J. J. , Wells M. G. H. , Perlmutter I.
Published: July 2002

The relationship between quantity and type of nonmetallic inclusions and critical mechanical properties was determined for the high-strength steels 4340 and 300M. Quantitative television microscope scanning data and various petrographic and microprobe methods were used to study the inclusions. Inclusion statistics showed that improved cleanliness was obtained in ascending order of (1) electric furnace air melted, (2) Dortmund–Horder degassed, (3) vacuum-arc–remelted and (4) electron beam hearth refined steels. Studies in the electron beam melted material were made on 1000 lb heats, whereas the remaining data were obtained on large-scale production heats. The properties for both 4340 and 300M improved in a similar manner with cleanliness. Transverse reduction of area was the property most influencd by inclusion content. Fatigue and impact properties were also affected, though to a lesser degree. Plane strain fracture toughness was relatively little affected by inclusion content and, in fact, longitudinal and transverse properties were substantially the same in direct contrast to reduction of area, impact, and fatigue properties. KIc is thus not a meaningful parameter for quality control measurement in these high-strength structural steels. While we realize that other factors, such as microsegregation, affect properties, we conclude that for steels processed according to specified practices, the inclusion content is the most important variable influencing critical mechanical properties.
Vacuum Induction Melting of Titanium
Authors: Griesenauer N. M. , Lyon S. R. , Alexander C. A.
Published: July 2002

Thermodynamic and melting experiments indicate considerable potential for the use of nonstoichiometric yttria as a crucible material for cold-wall induction melting of titanium metal. Experiments have shown that substoichiometric (reduced) Y2O3−x offers more resistance to attack by molten titanium, due to lower oxygen potential, but is subject to increased uptake of yttrium into solution. Yttria reacts with and contaminates molten titanium having greater than 100 °C superheat and where the crucible temperature is equal to or exceeds the melt temperature. The yttrium taken into solution, however, scavenges oxygen from the titanium solution and precipitates as Y2O3−x, reducing interstitials to acceptable levels. Normal cold-wail induction melting, using greater metal mass to contact area in a substoichiometric yttria crucible, should yield high quality titanium metal, comparable to some grades of present commercially pure metal. Development of the crucible material is continuing with studies of larger cold-wall induction melts.
Preparation and Corrosion Properties of a Tantalum Sputtered Thick Film
Authors: Kashu S. , Sano T. , Hayashi C.
Published: July 2002

A tantalum sputtered film formed on the surface of stainless steel (AISI-316) has good corrosion resistance to hot sulphuric acid. Corrosion resistance of sputtered tantalum films, 6–20 μ thick is superior to that of other high quality corrosion resistant materials, such as niobium, titanium, zirconium, Hastelloy-B, and AISI-316 stainless steel. The corrosion rate of sputtered tantalum films is similar to that of 50 μ thick tantalum foil. Results of up to 1000 h corrosions tests, an adhesion strength test, and a bend test of the film are presented in this paper.
Rotary, Linear Motion Vacuum Feedthrough
Authors: DiGiallonardo Anthony , Dixon Raymond D. , Anderson Kenneth L.
Published: July 2002

This paper describes a rotary, linear motion feedthrough. This was designed and built to permit film deposition from a source located below the substrate and subsequent rotation by 180° and translation of 3 in. This combination of motions was required for the film deposition and subsequent movement of the substrate and thin film into position to form one plate of a vibrating capacitor.
The Measurement of Conductance to Free Molecular Flow by Substitution Procedures
Authors: Ruthberg S.
Published: July 2002

A method is presented which yields an order of magnitude increase in precision in the measurement of conductance to free molecular flow. The technique utilizes a calibrated variable conductance as a reference in a true substitution procedure. A series line was used to study balanced and unbalanced conditions and to explore the effects of various factors on precision, such as flow stability, pump behavior, ionization gauge sensitivity and response, temperature, transients, and sorption. A parallel line was used for measurements on short tubes of small diameter. For this, an iteration technique was employed for the calibration of the variable conductance on an absolute basis. Ionization gauge resolution of 0.02% and linearity of better than 0.1% were achieved. Relaxation effects were apparent. Conductance measurement precision of a few parts per 1000 was obtained. Transmission probabilities for the small diameter, short tubes showed deviations of as much as 18% from the Clausing factors at length-to-radius ratios ≥1, but approached the Clausing values as l/r→ 0. Deviations of <1% from the Clausing value required l/r ≤0.05.
Investigation of the Effects of Heating in CO2 on the Oxide-Coated Cathode Surface Microtopography and Emission Characteristics of a Triode Electron Tube
Authors: Nowak E. J. , Max A. J. , Maurin J. K.
Published: July 2002

A process which causes repeatable microtopographical changes in the oxide cathode coating of an electron tube has been investigated. This process, which is carried out by heating the cathode in CO2, reduces surface roughness and the incidence of loose particles. The scanning electron microscope in conjunction with electrical measurements was used to document and assess the repeatability of these microtopographical changes in the cathode and the resulting changes in electrical performance. Increasing the time of heating (contact time) in CO2 from 1 to 30 rain was found to increase the degree of microtopographical change but also to decrease the triode pulse emission. CO2 treatment leaves the Richardson work function of the cathode unchanged at ∼ 1.1 eV, indicating that no significant, change in the chemistry of the cathode was caused by this treatment. The lower emission capability after CO2 treatment was due to decreased values of the Richardson constant. The change is logically attributable to the observed decrease in the micro-scale surface roughness of the coating. Decreases in the Richardson constant due to CO2 treatment ranged from ∼ 35% at a contact time of 2 min to ∼ 90% at a contact time of 30 min.
Plasma hardening of high chromium alloy steel containing distributed titanium carbide
Authors: Gifford Fay E. , Cooley Keith W.
Published: July 2002

Plasma nitriding of steel-bonded carbides was investigated to determine if this process hardens the material. It is found that the nitriding and hardening occur only in the tool steel matrix by the formation of the compounds Fe3N−Fe2N, γ′Fe4N and Fe3N, and it is hardened to 1500 Knoop. A case depth of 0.15 mm (0.006 in.) is developed in 6 h at a temperature of 600 °C. Conventional heat treatment through hardens the material to 900 Knoop compared to 700 Knoop as received.
Effects of Deposition Temperatures on Ta Thin Film Resistors Reactively Sputtered in Oxygen
Authors: Hardy W. R. , Mills D.
Published: July 2002

Effects of substrate temperature on the resistivity and TCR of Ta thin film resistors have been studied by depositing films onto glass substrates for which the temperature at the start of sputtering was varied from 25 to 285 °C. For these films which were reactively sputtered in oxygen flowing at a constant rate, the film resistivity decreases, the film TCR increases in the positive direction, and the average oxygen concentration in the films decreases as the initial substrate temperature is increased. The fact that the dependence of the resistivity and TCR of these films on the average oxygen concentration is the same as for films in which the oxygen concentration is varied by depositing the films at a single substrate temperature and varying the oxygen flow rate into the system indicates that the main effect of substrate temperature during deposition is to change the oxygen concentration in the films, rather than directly introducing any temperature-dependent changes in the film properties. For films containing from 10–20 at.% oxygen, the Ta condensation coefficient and film growth rate are largely independent of temperature.
Single Source Evaporation of a Niobium Based Alloy Containing Volatile Constituents
Authors: Stowell W. R.
Published: July 2002

By adding excess niobium to the molten metal pool of a rod-fed evaporation source in order to approximate a steady state condition, reproducible transfer of source material containing niobium, titanium, chromium, and aluminum has been achieved. Single source evaporative coating of this material has not been considered practical prior to this work because of the factor of 106 difference in vapor pressure between the most volatile element and the least volatile element. As produced, the coatings had a banded structure. A heat treatment homogenized the coatings. A model is suggested to explain the banded structure.
Electron optical column for a multicolumn, multibeam direct-write electron beam lithography system
Authors: Yin E. , Brodie A. D. , Tsai F. C. , Guo G. X. , Parker N. W.
Published: July 2002

Electron beam direct-write lithography systems are capable of meeting the resolution requirements of all future ITRS nodes and have a significant cost of ownership advantage over masked technologies, but these systems typically have very poor throughput due to space charge limitations. Ion Diagnostics has developed a multicolumn, multibeam (M×M™) direct-write system that circumvents the space charge limitations by spreading the electron current over the wafer. The resulting lithography system can achieve critical dimensions of less than 100 nm with production throughputs greater than 60 wafers per hour, independent of wafer size. In this article we describe the electron optical column used in this system. We have developed a novel, microfabricated electron gun that produces 32 parallel electron beams that are individually controlled and blanked and contain deflectors that allow the gun optics to act as a perfect lens. Each column is 2 cm×2 cm and can align and scan the 32 beams in parallel on the wafer. The wafer voltage is typically held at 50–100 kV, and backscattered electrons are collected for imaging and alignment information. Theoretical results and some performance results for a prototype column are presented.
Photoluminescence and heteroepitaxy of ZnO on sapphire substrate (0001) grown by rf magnetron sputtering
Authors: Kim Kyoung-Kook , Song Jae-Hoon , Jung Hyung-Jin , Choi Won-Kook , Park Seong-Ju , Song Jong-Han , Lee Jeong-Yong
Published: July 2002

ZnO thin films were epitaxially grown on α-Al2O3 (0001) single-crystal substrates by rf magnetron sputtering. The films were grown at substrate temperatures of 550–600 °C for 1 h at a rf power of 60–120 W and Ar/O2 ratios of 1–4. The crystalline structure of the ZnO films was analyzed by four-circle x-ray diffraction (XRD) and Rutherford backscattering (RBS)/channeling. For the ZnO films deposited at 550 °C, the full width at half maximum (FWHM) of the XRD θ-rocking curve of the ZnO (0002) plane was found to be increased from 0.16° to 0.3° as the rf power was increased from 80 to 120 W. The in-plane epitaxial relationship of the ZnO film on α-Al2O3 (0001) substrates was found to be ZnO [101̄0]∥α-Al2O3[112̄0], indicating a 30° rotation of the ZnO unit cell with respect to the α-Al2O3 (0001) substrate. For the specimen grown at 600 °C, the FWHM of the XRD θ-rocking curve was 0.13°. In RBS/channeling studies, the films, which were deposited at 600 °C and 120 W, showed good crystallinity, with a channeling yield minimum (χmin) of only 3.5%, whereas χmin for the films deposited at 550 °C was as high as 50%–60%, indicating poor crystalline quality. In the case of photoluminescence (PL) measurements, sharp near-band-edge emission was observed at room temperature. The FWHM of the PL peak decreased from 133 to 89 meV at a growth temperature 550 °C by increasing the rf power. For the films deposited at 600 °C, a FWHM of the PL peak of 75–90 meV was observed, which is the lowest value reported to date. From the results of both XRD and PL measurement, it was found that the crystallinity of the films grown at 550 °C improved, but its optical property degraded. With increasing rf power, the films show a deep-level emission in the presence of higher mixtures of Ar:O2 because a considerable amount of activated oxygen was supplied in the ZnO films with an increase of rf power. From transmission electron microscopy and atomic force microscope analyses, the grain size and defects were found to affect the PL properties. The relationship between optical properties and crystal quality is discussed in terms of crystalline structure and grain size.
The application of electron spectroscopy to surface studies
Authors: Brundle C. R.
Published: July 2002

The application of three branches of electron spectroscopy to surface studies, with particular emphasis on submonolayer chemisorption systems, is reviewed. The three branches are x-ray photoelectron spectroscopy (XPS), vacuum uv photoelectron spectroscopy (UPS), and Auger electron spectroscopy (AES). Each technique is considered from the standpoints of (i) the depth of material probes, (ii) signal strength, (iii) quantitative aspects, (iv) chemical information obtainable, and (v) induced surface effects. Since UPS does not provide an atomic identification, it is best used in conjunction with either of the other two techniques. In general, XPS will provide more chemical information, more quantitatively, than AES, though analysis times are slower. However, since the three techniques have advantages and disadvantages which may depend on the system studied and the object of the study, a combination of the three is usually preferable and can be experimentally achieved using only one electron energy analyzer.
Miscellaneous topics in Auger electron spectroscopy
Authors: Harris L. A.
Published: July 2002

Some of the history of the development of Auger electron spectroscopy and the author's part in it are outlined. Unpublished work on scanning Auger microscopy is briefly discussed.
Vacuum coating with a hollow cathode source
Authors: Williams Duane G.
Published: July 2002

An evaporation source capable of depositing extremely adherent coatings at high rates on conducting substrates is described. A high-current arc generated by a hot hollow cathode of the type developed by Lidsky et al. is directed upon a hearth containing the coating material. The arc evaporates and ionizes the material. Application of a potential to the substrate causes the acceleration of the ions toward the substrate. Ions bombarding the substrate surface remove adsorbed species and penetrate the lattice, producing excellent adhesion. Strengths exceeding 3.5×109 dyn cm−2 (51 000 psi) have been measured. Design details, performance data, and properties of the coatings are covered.
Investigation of mesa-sidewall effects on direct current and radio frequency characteristics of Ga0.51In0.49P/In0.15Ga0.85As/Ga0.51In0.49P pseudomorphic high electron mobility transistors
Authors: Yen Chih-Hung , Lin Kuan-Po , Yu Kuo-Hui , Chang Wen-Lung , Lin Kun-Wei , Liu Wen-Chau
Published: July 2002

The influences and improved methods for mesa-sidewall effects of GaInP/InGaAs/GaInP pseudomorphic high electron mobility transistors are investigated and demonstrated. The mesa-sidewall effects of gate leakage current path and parasitic capacitance seriously degrade the device characteristics. For instance, the excessive gate leakage current, reduced breakdown voltage and transconductance, variation of threshold voltage, increased sidegating effect, and degraded radio frequency response are found when the number of the mesa sidewall is increased. In the work, a simple and low-cost technique of the selective removal of mesa-sidewall materials is introduced. This selective etching method can substantially eliminate the mesa-sidewall contact problems of heterostructure field-effect transistor devices.
Stoichiometric and Oxygen-Terminated α-Cr2O3(101¯2) Surfaces
Authors: Abee Mark W. , Cox David F.
Published: July 2002

X-ray photoelectron spectroscopy (XPS) spectra are presented for two different preparations of a Cr2O3(101¯2) single crystal surface. A nearly stoichiometric surface is prepared by Ar-ion bombardment and annealing to 900 K in vacuum. An oxygen-terminated surface is prepared by dissociative adsorption of O2. Both surfaces exhibit (1 × 1) LEED periodicities. XPS shows a slight broadening (0.2 eV) and an increase in intensity of the O 1s feature following O2 adsorption. The increase in oxygen signal is representative of a coverage of nearly one oxygen atom per surface Cr cation.
Effect of growth interruption and the introduction of H2 on the growth of InGaN/GaN multiple quantum wells
Authors: Moon Yong-Tae , Kim Dong-Joon , Song Keun-Man , Kim Dong-Wan , Yi Min-Su , Noh Do-Young , Park Seong-Ju
Published: July 2002

The effects of the growth interruption and the introduction of H2 during interruption time on the optical and structural properties of InGaN/GaN multiquantum wells (MQWs), grown by metalorganic chemical vapor deposition, were investigated. When the growth was interrupted during the formation of interfaces in the MQWs, the intensity of photoluminescence (PL) was greatly increased and the formation of InN-rich regions near the surface of the InGaN well layer was suppressed. As the interruption time increased, however, the PL intensity decreased and the average In composition of InGaN/GaN MQWs decreased. When H2 was introduced during the growth interruption, the intensity of the PL was significantly enhanced by eliminating the impurities at the interface and the PL peaks were blueshifted due to the reduction in the thickness of the InGaN well layers, as a result of H2 etching of well and barrier layers.
Electron field emission properties of pulsed laser deposited carbon films containing carbon nanotubes
Authors: Chiang Ming-Ray , Liu Kuo-Shung , Lai Tzai-Shin , Tsai Chun-Horng , Cheng Hsiu-Fung , Lin I-Nan
Published: July 2002

Carbon nanotubes (CNTs) were successfully synthesized by using a modified pulsed laser deposition (PLD) process, in which the laser ejected carbon species were directly collected by silicon substrates. A catalyst layer is needed in this process. The morphology of catalyst clusters varies with the heat treatment process which, in turn, alters the morphology and field emission properties of the CNTs pronouncedly. Compared with the conventional laser ablation process, such a modified PLD process is simpler, has better collection efficiently, and has a higher production rate. The CNTs thus obtained exhibit superior field emission electron properties, viz. Je=160 μA/cm2 and E0=1.76 V/μm.
Effect of composition and microstructure on temperature coefficient of resistance of polycrystalline La1−xCaxMnO3 thin films
Authors: Lai Chih-Huang , Hsu C. F. , Chin Y. C. , Chiang Chengder
Published: July 2002

Polycrystalline La1−xCaxMnO3 films were rf-sputtered on Si substrates coated with SiO2, and the effects of deposition parameters on the temperature coefficient of resistance (TCR) values were investigated. For the temperature higher than the metal–insulator transition temperature (Tp), the temperature dependence of resistance can be described by using the small polaron model, and the TCR value increases with the activation energy Ea for the polaron hopping. For the temperature higher than Tp, increasing the oxygen or Ca content of the film results in the decrease in resistivity, Ea, and TCR value. The resistivity and TCR value are also reduced in large-grained films. Applying a substrate bias can enhance the TCR value.
Electrical characteristics of p–n junction diodes fabricated by Si epitaxy at low temperature using sputtering-type electron cyclotron resonance plasma
Authors: Wang Junli , Nakashima Hiroshi , Gao Junsi , Iwanaga Kanako , Furukawa Katsuhiko , Muraoka Katsunori , Sung Youl-moon
Published: July 2002

This article reports the electrical characteristics of p–n junction diodes that were formed by directly depositing a Sb-doped n-type epilayer on a p-type substrate by using a dc-bias electron cyclotron resonance plasma sputtering system at a low temperature of 400 °C and a conventional vacuum of 5×10−7 Torr. The reverse current density of the n+–p junctions diodes depends on deposition gas pressures and substrate biases. The n+–p junction diodes exhibit, under optimum conditions, a reverse current density as low as 9.5×10−9 A/cm2 at a reverse bias voltage of 5 V and an ideality factor of 1.05. The excellent characteristics of the n+–p junction diode are due to the integrity of interface between n+ epilayer and p-type Si substrate.
Effects of thermal annealing on the interface morphology of CdTe/CdS heterojunctions
Authors: Huang S. , Soo Y. L. , Kao Y. H. , Compaan A. D.
Published: July 2002

The effects of thermal annealing on CdTe/CdS heterojunctions have been investigated by means of the grazing incidence x-ray scattering technique. Changes in the interface morphology due to heat treatment are characterized quantitatively in terms of a set of parameters including the interfacial roughness and correlation lengths of the layer thickness fluctuations.
GaAs (110) by Time-resolved XPS
Authors: Deng Z. W. , Kwok R. W. M. , Lau W. M. , Cao L. L.
Published: July 2002

Time-resolved binding energy (BE) changes of the Ga 2p3/2 level of heavily doped n-GaAs (100) (Si-doped with a carrier density of 3 × 1018 cm−3) and p-GaAs (100) (Zn-doped with a carrier density of 5∼6 × 1019 cm−3) after cleaving in UHV were measured by XPS. Also presented are spectra of survey, Ga 2p3/2, Ga 3d, and As 3d levels after the BE stopped shifting. Measurements were carried out on the in situ cleaved (110) facets. The results show nearly flat band surface as cleaved in UHV. The subsequent binding energy changes reflected the Fermi level shift in band gap relative to the valence band maximum induced by surface states which are believed to be a consequence of surface lattice relaxation after cleavage. The accurate BE of as-cleaved Ga 3d and As 3d levels can be obtained via interpolation according to the BE changes of Ga 2p3/2.
Novel high resolution scanning thermal probe
Authors: Edinger K. , Gotszalk T. , Rangelow I. W.
Published: July 2002

Scanning thermal microscopy is a scanning proximal probe technique, which can be used for mapping spatial variation of thermal properties of a surface such as temperature, thermal conductivity, and thermal diffusivity. The sensor presented here is a resistance based probe consisting of a nanometer-sized filament formed at the end of a piezoresistive atomic force microscope type cantilever. The freestanding filament is deposited by focused electron beam deposition using methylcyclopentadienyl trimethyl platinum as a precursor gas. The filament height is in the range of 2–5 μm, with typical “wire” diameters between 30 and 100 nm. Typical deposition times are between 2 and 5 min, and might be further shortened by optimizing the precursor gas flux. Because of its small size, the new probe has a high spatial resolution (<20 nm tip end radius) and, due to the low thermal mass, a high thermal sensitivity and fast response time. In this article, experiments designed to characterize the mechanical stability and electrical and thermal properties of the nanometer-sized probe are presented.
Dependence of ion beam induced nitrogen diffusion in aluminum on oxygen impurities
Authors: Manova D. , Huber P. , Sienz S. , Gerlach J. W. , Mändl S. , Rauschenbach B.
Published: July 2002

The diffusion of nitrogen in aluminum is investigated for three different methods of nitrogen implantation. Low energy nitrogen implantation (LEI) at 1 keV and plasma immersion ion implantation (PIII) with −30 kV pulses were performed in the temperature range from 250 to 500 °C, together with conventional ion implantation at room temperature with 100 keV N+ ions and subsequent annealing in vacuum at 440 or 485 °C. For the LEI samples a rather high diffusion leading to AlN layers of a few microns in less than 1 h was found, whereas a low diffusion coefficient was obtained for the PIII samples, exhibiting a sharp step near 350 °C. In contrast no diffusion was measured in the implanted and annealed samples. Several different factors are proposed to influence the observed diffusion: A competing path between the formation of AlN by trapping of N and N diffusion is responsible for the dependence of the layer thickness on the supply of nitrogen. The oxygen contamination drastically reduces the diffusion constant by occupying the surface sites and blocking the diffusion path. Finally, the phase transformation from c-AlN to h-AlN may cause the sudden onset of diffusion around 350 °C.
Bright peak enhanced x-ray clear phase mask
Authors: Yang Lei , Cerrina Franco , Taylor James W.
Published: July 2002

A clear bright peak enhanced x-ray phase mask (BPEXPM) is described. It employs the constructive interference of spatially coherent radiation as opposed to the destructive interference that is used in all the other phase-shifting schemes. This type of mask shows ultrahigh resolution imaging, feature reduction from the mask critical dimension (CD), and enhanced transmission. It has been simulated and verified experimentally with a 320 nm mask CD. Specifically, the BPEXPM exhibits: (1) approximately three times higher effective sensitivity, 40 mJ/cm2 dose to mask for Shipley XP-9947E, a positive-tone chemically amplified resist that normally has a sensitivity of 120 mJ/cm2 in the x-ray region and (2) resolution of 54 nm features in XP-9947E at a 50 μm gap for a 320 nm mask CD. The simulation for the BPEXPM also predicts a wafer image CD of 31 nm at 10 μm gaps with a 150 nm mask CD.
Ionized physical vapor deposition of titanium nitride: Plasma and film characterization
Authors: Mao D. , Tao K. , Hopwood J.
Published: July 2002

The ionized physical vapor deposition of titanium nitride is experimentally investigated in terms of both plasma characteristics and TiN material properties. The vibrational and translational gas temperatures of N2 molecules are determined using optical emission spectroscopy by fitting the intensities of vibrational transitions to the nonequilibrium Treanor distribution. The gas temperature is typically 720 K at 15 mTorr. The dissociation of nitrogen is determined using mass spectrometry and found to increase with plasma power from 10% to 30% as the power is increased from 750 to 1500 W. From this data, it is calculated that the density of atomic nitrogen in the inductively coupled plasma source is the order of 1012 cm−3. Langmuir probe measurements indicate that the electron temperature is 1.6–2.0 eV and the ion density is (2–6)×1011 cm−3. Rutherford backscattering spectroscopy (RBS) shows that the TiNx films have increasing nitrogen composition (0.26<x<1.5) as the nitrogen content increases from 2% to 9% in the Ar/N2 plasma. The flux of nitrogen atoms from the plasma, as determined from the measured gas temperature and dissociation, is compared with the flux of nitrogen that is incorporated in the film according to RBS. The ratio of these two fluxes gives an upper-bound for the sticking coefficient of atomic N on TiNx, which is ∼0.1 for titanium-rich films and ∼0.003 for nitrogen-rich films.
Characterization of low permittivity (low-k) polymeric dielectric films for low temperature device integration
Authors: Sivoththaman S. , Jeyakumar R. , Ren L. , Nathan A.
Published: July 2002

Spin-coated low-k dielectrics are now widely used in integrated circuit processing due to their low permittivity and planarization properties. Another area of potential application is in large area digital imaging using amorphous silicon (a-Si:H) technology where low-k dielectrics enable new integration schemes for thin film transistors (TFT) and sensors. In this work, the properties of spin-coated, polymeric, low-k dielectric materials, BCB (benzocyclobutene) and HSQ (hydrogen silsesquioxane), are studied after treating them with low temperature anneals. Fourier transform infrared spectroscopy (FTIR), high frequency capacitance–voltage, topographic planarization, and wafer deflection stress measurements have been used to characterize the films so as to correlate with processing conditions. Lower k values are obtained for lower process temperatures and are correlated by capacitance and FTIR measurements. Annealing in the presence of O2 appears to increase the permittivity. The BCB films yield low stress and good (>90%) planarization and are suitable as interlevel dielectrics in the vertical integration of a-Si TFT and sensor arrays.
A Mass Spectrometric Study of the Outgassing of Some Elastomers and Plastics
Authors: Barton R. S. , Govier R. P.
Published: July 2002

Information on the outgassing properties of a number of plastic materials has been obtained by the use of a bakeable mass spectrometer. This was fitted with vacuum locks to avoid affecting the residual gas compositions by introduction of the sample. Each material was examined after, (1) it had been pumped for an acceptable pumpdown time, (2) it had been baked in vacuo at its maximum permissible temperature, (3) re-exposure to the laboratory atmosphere followed by the same period of pumping as originally adopted. The majority of the materials examined showed water to be the main component of outgassing. In general, bakeout in vacuo produced a permanent reduction in hydrocarbon evolution, but after re-exposure to laboratory air the rate of water vapor evolution was comparable with that originally observed.
Isothermal Release of Ionically Pumped Inert Gases
Authors: Smeaton G. P. , Carter G.
Published: July 2002

The release of He, Ar, and Xe, ionically pumped into Pyrex glass surfaces, is studied as a function of time after the cessation of pumping. Both pumping and release are conducted at room temperature. The parameters of pumping pressure and pumping time are varied in a dynamic system so that the pressure during pumping is maintained constant. A general release-rate function of the form Rate proportional to Time raised to the —m is obtained, the index m depending upon the pumping time, pressure, and gas species; and the results are interpreted in terms of release of gas from capture sites in the glass that possess a spectrum of activation energies for desorption.
Experimental Test of Surface Phase Theory for Ultrahigh Vacuum Systems
Authors: Earnshaw J. W. , Hobson J. P.
Published: July 2002

Experiments are described which test the surface phase theory (developed in a previous paper) for ultrahigh vacuum systems. Tests were performed on a system containing 3×10−9 Torr of argon in equilibrium with a physically adsorbed phase at 77 °K. The surface phase theory is used to estimate parameters of the system (e.g., pumping speed, leak rate, quantity of gas in a physically adsorbed phase) and then estimates are compared with direct observations. Variations of the pressure of argon in this system are compared with those of carbon monoxide at room temperature in the same system. The generality of the surface phase process for many gases in vacuum systems is discussed.
Theoretical Analysis of a Two-Pump Vacuum System
Authors: Kendall B. R. F.
Published: July 2002

Factors affecting the pressure in a vacuum chamber pumped by two dissimilar pumps are investigated with the aid of a simplified theoretical model. The possibility of one of the pumps acting as a significant source of gas or vapor is taken into account. It is shown that minimum chamber pressure may be obtainable only with a finite pumping-line impedance in series with this pump. An experimental illustration of the phenomenon is given. Applications of the theory to the design of vacuum systems are discussed.
Free Molecular Gas Flow Through A Moving Absorbing Cylindrical Tube
Authors: Cohen Herbert A.
Published: July 2002

A Monte Carlo method was used to determine the transmission and reflection coefficients of cylindrical tubes with absorbing walls moving in a free molecular pressure region. Transmission and reflection coefficients are given for a range of tube lengths, velocities, attack angles, and absorption coefficients.
Dielectric Properties of Reactively Evaporated Silicon Monoxide
Authors: Anastasio Thomas A.
Published: July 2002

Dielectric constant and dissipation factor for films formed by the reactive evaporation of silicon monoxide in oxygen have been measured as a function of deposition rate, oxygen pressure, electrode material, substrate temperature during evaporation, and source temperature. The dielectric properties are shown to depend primarily on the ratio of molecular impingement rates at the substrate of O2 and SiO (p/r), independent of substrate temperature and electrode material. Dissipation factor, but not dielectric constant, is strongly dependent on source temperature. Some dc conductivity and capacitor discharge characteristics are related to the p/r parameter.
Application of gas chromatography for direct analysis of gas mixtures in the 10−4–10 Torr range
Authors: Borghi M. , Rosai L.
Published: July 2002

A new technique which combines gas chromatography and UHV techniques is described for the direct analysis of the components of gaseous mixtures whose total pressure lies between 10−4 Torr and atmospheric. It therefore covers the gap of total pressure in which both mass spectrometry and traditional gas chromatography are not able to work directly and in a satisfactory way. It has been possible to detect partial pressures down to 10−5–10−6 Torr in a gas at a pressure of 1 Torr. Concentrations down to 1–10 ppm are, therefore, measured. Due to the limited quantity of the gas required for the analysis, this technique is particularly suitable for the quantitative measurement of impurities present in the filling gas of various devices, even during their operation. Results obtained in a practical case using the technique are reported.
Ion-plated aluminum oxide coatings for protection against corrosion
Authors: Swaroop B. , Meyer D. E. , White G. W.
Published: July 2002

Ion-plated aluminum oxide coatings were deposited on stainless steel substrates using superimposed radio-frequency signals and direct voltage. The deposition was achieved in a partial pressure of argon, argon–oxygen, or water vapor. Deposition rates of aluminum oxide as high as 15 μm/min were obtained. The coatings were evaluated for thermal-cycling resistance and corrosion protection to the substrate in a synthetic coal-gas mixture at 980°C. The intermediate layers of Al/Hf between the substrate and the aluminum oxide coating were ion plated to reduce the thermal spalling.
Vacuum brazing of aluminum: Auger studies of wetting and flow characteristics
Authors: Winterbottom W. L. , Gilmour G. A.
Published: July 2002

Fluxless vacuum brazing has become a commercially feasible process for the high-volume, low-cost production of aluminum heat exchangers. With an Al–Si–Mg filler metal, excellent joint quality is obtained without requiring the use of a flux. A limited understanding of the wetting and flow characteristics of the filler alloy and the role of the magnesium promoter in the vacuum process, however, have hampered efforts to optimize control of the vacuum process. Auger electron spectroscopy and vaporization methods have been used in studying the mechanism of brazing to elucidate the characteristics of the oxide film barrier and magnesium promoter. With these methods it is possible to follow the distinctive variations in surface composition and magnesium vaporization rate that occur in the braze sheet as a function of its temperature. The mechanistic details of the wetting and flow processes in this commercially important material are delineated in the results.