bluuebunny/crossref_metadata_2025 huggingface dataset:
Collapse Tests on Externally Pressurized Toroids
Authors: Błachut J.
Published: February 2003

The paper discusses the load-carrying capacity of toroidal shells with closed circular cross section and loaded by static external pressure. Details about the manufacturing, pre-experiment measurements and testing of three, nominally different, steel toroids are provided. Two of them were manufactured from mild steel by spinning two halves and then welding them around the inner and outer equatorial perimeters. The third one has been assembled by welding four 90-deg stainless elbows. The outer diameter of these models was about 300 mm and the wall thickness varied from 2.0 to 3.0 mm. The hoop radius-to-thickness ratio, r/t, varied from about 15 to 30. The experimental collapse pressures were in the range from 4 to 8 MPa. Comparisons with numerical results are also provided.
Effect of Temperature on Fatigue Crack Growth in CPVC
Authors: Irfan-ul-Haq Muhammad , Merah Nesar
Published: February 2003

This study addresses the effect of temperature on fatigue crack growth (FCG) behavior of CPVC. FCG tests were conducted on CPVC SEN tensile specimens in the temperature range −10 to 70°C. These specimens were prepared from 4-in. injection-molded pipe fittings. Crack growth behavior was studied using LEFM concepts. The stress intensity factor was modified to include the crack closure and plastic zone effects. The effective stress intensity factor range ΔKeff gave satisfactory correlation of crack growth rate (da/dN) at all temperatures of interest. The crack growth resistance was found to decrease with temperature increase. The effect of temperature on da/dN was investigated by considering the variation of mechanical properties with temperature. Master curves were developed by normalizing ΔKeff by fracture strain and yield stress. All the da/dN-ΔK curves at different temperatures were collapsed on a single curve. Crazing was found to be the dominant fatigue mechanism, especially at high temperature, while shear yielding was the dominant mechanism at low temperatures.
High-resolution retarding field analyzer
Authors: Johnson S. D. , El-Gomati M. M. , Enloe L.
Published: February 2003

A simple to construct, high-resolution, retarding field analyzer (RFA) comprising a cone-in-the-can electrode configuration was developed to eliminate the problems associated with the planar RFA, specifically potential sagging around the discrete wires of the grid and the cutoff energy dependence on arrival angle. This study extends the analysis of this spectrometer by discussing its performance as a function of its internal dimensions, specifically the length to width (L/W) ratio of the analyzer body. Experimental data for several designs are also included and indicate a resolution of the order of 1% is achievable. The simple geometry of the analyzer lends itself to miniaturization. However, the elimination of the grid from the device is an essential task if full miniaturization of the analyzer is to be realized. Such a gridless high-resolution RFA has been developed and the first results from this device show a resolution comparable to that of the grid-based design. Performance analysis of the gridless analyzer as a function of its dimensions is also reported.
Fabrication and field emission characteristics of lateral diamond field emitter
Authors: Kang W. P. , Davidson J. L. , Wisitsora-at A. , Howell M. , Jamaludin A. , Wong Y. M. , Soh K. L. , Kerns D. V.
Published: February 2003

Lateral diamond field emitters were fabricated by a diamond patterning technique that utilizes oxide patterning and lift-off process on a silicon-on-insulator wafer. An anode–cathode spacing of 2 μm between the diamond anode and cathode was achieved. The fabricated lateral diamond emitter diode exhibits excellent emission characteristics with a low turn-on voltage of ∼5 V and a high emission current of 6 μA, from four diamond fingers, at an anode voltage of 25 V. The emission current is stable over time, even at high emission current. The low turn-on voltage (turn-on field ∼3 V/μm) and high emission characteristics are among the best of reported lateral field emitter structures. The lateral diamond field emitter has potential applications in vacuum microelectronics, sensors, and microelectromechanical systems.
Field emission from metal particles bound with a photoresist
Authors: Baba Akiyoshi , Asano Tanemasa
Published: February 2003

A film composed of metal particles was evaluated as a material for the fabrication of field electron emitters on large substrates. Two test films were prepared on silicon substrates from either a mixture of fine palladium particles or spin-on glass and a mixture of fine palladium particles and a positive tone photoresist. Field electron emission characteristics were evaluated with a diode. It was found that the insulating film on the surface of the electron emitting material acted as a barrier to electron emission. It was also found that, with the application of a constant voltage, the field emission current abruptly increased with time in the initial stage of field electron emission. Following this phenomenon the threshold voltage for electron emission was drastically reduced and the emission current fluctuation was less than 10%.
Metal–oxide–semiconductor field effect transistor-controlled field emission display
Authors: Kim Il Hwan , Lee Jong Duk , Oh Chang Woo , Park Jae Woo , Park Byung Gook
Published: February 2003

A metal–oxide–semiconductor field effect transistor-controlled field emission display (MCFED) was fabricated to evaluate the validity of MCFEAs (MOSFET-controlled field emitter arrays) for display application. The electrical properties of FEAs, HVMOSFETs (high voltage MOSFETs), and MCFEAs were measured. The gate hole diameter of a fabricated FEA is 1.25 μm and the extraction gate voltage to obtain the anode current of 10 nA/tip is 71 V. The threshold voltage and the breakdown voltage of a HVMOSFET are 1.4 and 81 V, respectively. The I–V characteristics of a MCFEA show that the emission currents of FEA are well controlled by the control gate voltage of the HVMOSFET. To exclude the harmful effects generated during the packaging process, the performance of the MCFED was evaluated in a high vacuum chamber. It was proven that the uniformity of a conventional FED could be improved by the integration with a MOSFET.
Dependence of field emission from AlxGa1−xN on the stoichiometric composition for x⩽0.7
Authors: Chung M. S. , Cutler P. H. , Miskovsky N. M.
Published: February 2003

The field emission current density j from the ternary alloy AlxGa1−xN is fully calculated as a function of a stoichiometric composition x. The carrier concentration n is numerically obtained as a function of x from the measured values of n. Most of the other material parameters of AlxGa1−xN are obtained as a function of x by averaging those of GaN and AlN. Then we use an exact scheme to calculate j as a function of x for x⩽0.7. The calculated plots of j versus x are different in shape according to the value of electron affinity, χ, of AlxGa1−xN. For low χ, j has a peak in the transition region from semiconductor to insulator while for high χ, j does not. Such a peak becomes more apparent and moves toward a smaller x as χ decreases and the field F increases.
Emission characteristics of a GaAs wedge emitter monolithically fabricated with an air bridge and a cantilever anode
Authors: Mimura H. , Yilmazoglu O. , Shimawaki H. , Yokoo K. , Mutamba K. , Hartnagel H.
Published: February 2003

GaAs wedge emitters with an air bridge anode and a cantilever anode were monolithically fabricated using a micromachining technique. The threshold voltage of electron emission is about 8 V for the diode between the emitter and the air bridge anode, while only 1.5 V for the diode between the emitter and the cantilever anode. The current–voltage characteristic of the air bridge diode is due to a field emission, on the other hand, that of the cantilever diode is recognized as a direct tunneling of electrons through the reduced air gap between the emitter and the cantilever by electrostatic force.
Electron gun with field emission cathode of carbon fiber bundle
Authors: Baturin A. S. , Yeskin I. N. , Trufanov A. I. , Chadaev N. N. , Sheshin E. P. , Tchesov R. G.
Published: February 2003

The electron gun with field emission cathode is developed. The cathode was made of a bundle of carbon fibers. Specific properties of electron gun with bundles of carbon fibers are related to mechanical displacement of carbon fibers in the bundle. Specific types of emission current instability in connection with mechanical properties of cathode are described. The developed electron gun could be used to replace hot cathodes. Application of the gun for a light source and compact x-ray tube is considered.
Field-emission characteristics of carbon buckypaper
Authors: Knapp W. , Schleussner D.
Published: February 2003

Carbon buckypaper was investigated with respect to field-emission properties and long-term stability, especially under well-defined stress conditions. The carbon buckypaper field emitters showed a threshold field strength of about 1 V μm−1 for an emission current of 1 nA. Field-emission current densities of more than 10 mA cm−2 are measured for higher applied field strengths. The main focus of our investigations is the interaction of field emission and vacuum conditions. In this contribution, reproducible stress tests with microdischarges are presented. Higher emission current densities of about 100 mA cm−2 increased ionization, and luminescence out of the emission zone even appears before the microdischarges start. After arcing with microdischarges, the carbon buckypaper field emission has lower emission current density and lower variation range. However, the contribution demonstrates the advantages of carbon buckypaper as a large-array electron field emitter for cold-cathode applications.
Field emission vacuum power switch using vertically aligned carbon nanotubes
Authors: Rupesinghe N. L. , Chhowalla M. , Teo K. B. K. , Amaratunga G. A. J.
Published: February 2003

A field emission vacuum switch using vertically aligned carbon nanotubes grown by a direct current plasma enhanced chemical vapor deposition is reported. Cathodes with optimized field emission properties were evaluated in diode configuration as a test vehicle for the construction of a vacuum power three terminal triode device. Limiting factors such as space charge effects involved with high current densities (more than 10 mA/cm2) are also investigated using computer simulations.
Double-gated silicon field emitters
Authors: Dvorson L. , Kymissis I. , Akinwande A. I.
Published: February 2003

Gated field emission devices have great promise for a number of applications. The electron beams formed by these devices are poorly collimated, however, which limits their utility for certain applications. This article describes an approach to collimating the electron beam and forming a small spot size by using a new chemical–mechanical polishing process to make an electron lens at each field emission tip. Variations in the tip height with respect to the aperture vary βF/βG between 0.16 and 2.67, showing significant sensitivity of the coupling between the focus gate and tip as a function of process variation. The tips exhibit good Fowler–Nordheim behavior and interesting electrostatic properties. Electron spot size reduction greater than ten times is demonstrated.
Field emission from nanocomposites
Authors: Lerner Peter , Miskovsky N. M. , Cutler P. H. , Chung Moon S.
Published: February 2003

We study field emission from wide band gap metal–semiconductor nanocomposites. The grains of the wide band gap semiconductor are embedded into the layers of metal. Interfacial charge transfer gives rise to the metal-induced gap states (MIGS) in the vicinity of the grains. If the density of the semiconductor grains is sufficiently large, MIGS hybridize with conduction band states of the semiconductor forming a quasi-band, which can be populated by the electrons from the metallic matrix through the scattering in the metal–semiconductor composite. The location of the high-lying MIGS in the vicinity of the conduction band of the wide band gap semiconductor (e.g., diamond) significantly reduces the barrier between those states and the vacuum level compared to the work function of a metal. Thus low-threshold field emission from a nanocomposite becomes possible. This hypothesis is supported by Monte Carlo simulation of transport through a nanocomposite.
Uniformity and stability of field emission from bare and metal coated Si tip arrays
Authors: Günther B. , Kaldasch F. , Müller G. , Schmitt S. , Henning T. , Huber R. , Lacher M.
Published: February 2003

Field emitter arrays of tips of some micrometers in height have been fabricated from p- and n-doped Si substrates by photolithographic techniques and partially coated with 7.5 nm thick W, Pt, or Cr layers by magnetron sputtering. The emission uniformity of these tip arrays was investigated with a field emission scanning microscope. The local current stability was measured with a spectrum analyzer. The bare Si tips show low average extraction fields (∼35 V/μm for 10 nA) but moderate uniformity and pronounced current noise and switches. In comparison, the metal-coated Si tips yield improved emission uniformity with up to 100% of emitting tips and sufficient stability up to 700 nA (1 μA) in the case of Pt (W) coating, but also a factor of 2 higher extraction fields. Noise power spectra of W and Pt coated samples showed a typical 1/fγ dependence up to the kHz range with a spectral density index γ of about 3.
Variations in structure and emission characteristics of nanostructured carbon films prepared by the hot-filament chemical-vapor-deposition method due to the addition of ammonia in the source
Authors: Choi Seungho , Park Kyung Ho , Han Hyung Jun , Lee Kyung Moon , Lee Soonil , Koh Ken Ha
Published: February 2003

We investigated the structural variation and the concomitant change in the emission characteristics of hot-filament chemical-vapor-deposition-grown nanostructured carbon films induced by the addition of ammonia to source gases. At low ammonia concentrations the film morphology was dominated by carbon nanoparticles encapsulating metal and/or carbide cores. As the ammonia concentration was increased nanotube density increased, and in the medium ammonia-concentration range nanotubes dominated the film morphology. However, at 80% of ammonia concentration the number of nanotubes decreased substantially and nanoparticles became the dominant species again. The diameter, length, and shape of nanotubes also showed systematic ammonia-concentration- dependent variations, while the nanoparticle size did not change significantly. Another important variation was found in the quality of carbon layers constituting the carbon nanoparticles and nanotubes. As more and more ammonia was added to the source gas, large structural deterioration, including the increase of disorder in the atomic bonding and the decrease of graphitic sheet size, was observed. The electron-emission characteristics of these films were as diverse as their morphological and structural variations. At the low ammonia-concentration range, the emission was degraded as the ammonia concentration was increased. However, when the ammonia concentration was increased up to 40%, the emission was recovered almost back to the best level. At higher ammonia concentrations, substantial emission degradation recurred.
Reticulated vitreous carbon field emission cathodes for light source applications
Authors: Chakhovskoi Andrei G. , Hunt Charles E. , Forsberg Gunnar , Nilsson Thomas , Persson Per
Published: February 2003

Reticulated vitreous carbon (RVC) is demonstrated as a viable field emission electron source for cathodoluminescent lamps. The high void volume and porous structure of RVC help create a large number of natural emission sites on the surface. Emission centers are formed by the sharp edges of the carbon struts, which result from simple machining of the macroscopic open-pore material. Additional surface treatment of the emitters in vacuum or in open air helps to increase the extracted current and reduce the current fluctuations. Electron emission has been evaluated in the 10 to 500 μA range, in 10−6 to 10−8 Torr vacuum ambient. Extended lifetime tests were carried out for over 5000 h in sealed glass prototype devices utilizing commercial cathodoluminescent phosphors. Brightness levels exceeding 10 000 cd/m2 were achieved for diode and triode configurations. The low cost of manufacturing, along with chemical and mechanical robustness, make RVC a viable material for electron-beam vacuum device applications such as mercury-free cathodoluminescent light sources.
Silicon doped diamond-like carbon films as a coating for improvement of electron field emission
Authors: Evtukh Anatoli A. , Litovchenko Volodimir G. , Litvin Yurii M. , Fedin Dmitrii V. , Dzyan Olexander S. , Pedchenko Yu. N. , Chakhovskoi Andrei G. , Felter Thomas E.
Published: February 2003

To improve the electron field emission parameters of silicon tips diamond-like carbon (DLC) films doped with silicon have been used as a coating. The idea was to enhance the field emission efficiency using DLC film and increase the DLC film conductivity to make easier electron transport from the silicon tip through the DLC film. The emission properties of in situ silicon doped DLC films have been investigated. Undoped and silicon doped DLC films were grown by plasma enhanced chemical vapor deposition from CH4:H2 and CH4:H2:SiH4 mixtures, respectively. In situ gas-phase doping allowed us to deposit DLC films with different concentrations of silicon in them. The concentration of SiH4 in the gas mixture was varied from 0% to 50%. To characterize the electron conductivity of undoped and silicon doped DLC films metal–insulator–semiconductor (Al–DLC–Si) capacitors were prepared on flat silicon wafers. The strong influence of silicon doping on DLC film properties and electron field emission was revealed. The conductivity of the DLC films increased and the electron field emission changed after doping of the DLC films with silicon. It is shown that silicon doped DLC films are a prospective coating for improvement of electron field emission from silicon tip arrays.
Fabrication of Si single-electron transistors with precise dimensions by electron-beam nanolithography
Authors: Namatsu H. , Watanabe Y. , Yamazaki K. , Yamaguchi T. , Nagase M. , Ono Y. , Fujiwara A. , Horiguchi S.
Published: February 2003

Determining the relationship between wire size and the electrical characteristics of a single-electron transistor (SET) can significantly shorten the development time required to make SETs practical devices. In this study, this relationship was examined by fabricating SETs with precise dimensions using electron-beam nanolithography. The high-resolution resist HSQ provided fine wire patterns with small linewidth fluctuations. Si nanowires were made by etching using HSQ patterns as a mask, and then oxidized to produce SETs. The electrical characteristics were measured to determine the wire size required for making operational SETs. First, it was found that more oxidation widens the range of wire widths for which clear Coulomb blockade oscillations are observed. This is probably because more oxidation produces more oxidation-induced stress, which deepens the potential well essential for SET operation. In addition, it was experimentally confirmed that the gate capacitance is proportional to the nanowire length. These results demonstrate that SETs can be fabricated with good control of the size.
Application of electron-beam lithography in manufacturing of magnetic heads
Authors: Kurokawa Masaki , Yamada Akio
Published: February 2003

In this article, we show a practical way to improve overlay accuracy that is consistent with resolution performance for manufacturing magnetic heads by electron-beam lithography. First, we report the electron-beam displacement caused by disturbances in the objective lens magnetic field of lithography equipment when wafers coated with high permeability material are inserted into the immersion objective lens. Then we propose a method that compensates for these displacements by using a compensation map. Next, we apply these corrected values to actual exposure and achieve overlay accuracy of 3 σ<50 nm. We also evaluate the appropriateness of this compensation method by measuring the influence of the magnetic hysteresis of the magnetic material coated wafers and analyzing the influence of the distribution of magnetic material inside the lens.
Physical and electrical properties of metal gate electrodes on HfO2 gate dielectrics
Authors: Schaeffer J. K. , Samavedam S. B. , Gilmer D. C. , Dhandapani V. , Tobin P. J. , Mogab J. , Nguyen B.-Y. , White B. E. , Dakshina-Murthy S. , Rai R. S. , Jiang Z.-X. , Martin R. , Raymond M. V. , Zavala M. , La L. B. , Smith J. A. , Garcia R. , Roan D. , Kottke M. , Gregory R. B.
Published: February 2003

As the metal–oxide–semiconductor field-effect transistor (MOSFET) gate lengths scale down to 50 nm and below, the expected increase in gate leakage will be countered by the use of a high dielectric constant (high-k) gate oxide. The series capacitance from polysilicon gate electrode depletion significantly reduces the gate capacitance as the dielectric thickness is scaled to 10 Å equivalent oxide thickness (EOT) or below. Metal gates promise to solve this problem and address other gate stack scaling concerns like boron penetration and elevated gate resistance. Extensive simulations have shown that the optimal gate work functions for the sub-50 nm channel lengths should be 0.2 eV below (above) the conduction (valence) band edge of silicon for n-type MOSFETs (p-type MOSFETs). This study summarizes the evaluations of TiN, Ta–Si–N, WN, TaN, TaSi, Ir, and IrO2 as candidate metals for dual-metal gate complementary metal–oxide semiconductor using HfO2 as the gate dielectric. The gate work function was determined by fabricating metal–oxide–semiconductor capacitors with varying dielectric thicknesses and different post-gate anneals. The metal–dielectric compatibility was studied by annealing the gate stacks at different temperatures. The gate stacks were characterized using transmission electron microscopy, secondary ion mass spectroscopy, Rutherford backscattering spectroscopy, atomic force microscopy, and x-ray diffraction. Based on work functions and thermal stability, Ta–Si–N and TaN show the most promise as metal electrodes for HfO2 n-MOSFETs.
Growth-temperature dependence of the microstructure of ErAs islands in GaAs
Authors: Kadow C. , Johnson J. A. , Kolstad K. , Gossard A. C.
Published: February 2003

This article concerns the growth-temperature dependence of the microstructure of ErAs islands embedded in GaAs. The material was grown by molecular-beam epitaxy. The nucleation of ErAs on GaAs occurs in an island growth mode leading to spontaneous formation of nanometer-sized islands. Multiple layers of ErAs islands separated by GaAs can be stacked on top of each other to form a superlattice along the growth direction. A series of four such samples were grown at growth temperatures of 480 °C, 535 °C, 580 °C, and 630 °C. For all samples, 1.8 monolayers of ErAs were deposited in each layer of the superlattices. The microstructure of these samples was investigated by x-ray diffraction and transmission electron microscopy. We find that single crystallinity was maintained across the layers of ErAs islands at the growth temperatures of 535 °C, 580 °C, and 630 °C. At the growth temperature of 480 °C, however, the sample was not single crystalline. The GaAs matrix of the sample was defective. With increasing growth temperature, the size of the ErAs islands increased and the areal density of the ErAs islands decreased. The size increase is due to an increasing lateral (in-plane) dimension; the height of the islands is essentially unchanged.
Investigation of various copper seed layers for copper electrodeposition applicable to ultralarge-scale integration interconnection
Authors: Kim Jae Jeong , Kim Soo-Kil , Lee Chang Hwa , Kim Yong Shik
Published: February 2003

As a superior substituent for the chemical-vapor deposition and physical-vapor deposition (PVD) Cu processes in an ultralarge-scale integrated interconnection, electrodeposition on two kinds of electroless-plated Cu seed layers was investigated. Co(II) and formaldehyde were used as reducing agents for each electroless plating. Two samples of electroless-plated seed layers had relatively higher resistivity due to rough and irregular grains and weakly developed (111) texture, which are peculiarities of electroless plating. However, the Cu electrodeposited onto the electroless-plated seed showed reasonably good characteristics in resistivity, impurity level, crystalline structure, and surface roughness compared to those on the conventional PVD Cu seed. For the gap filling in the damascene structure, the electroless seed layer plating using formaldehyde and the subsequent electrodeposition on a patterned wafer showed an excellent filling profile without any voids or keyholes. After 400 °C annealing in a N2 atmosphere, adhesion between the Cu/barrier interfaces of electrodeposited copper on the two electroless-plated seeds was highly improved.
Lifetime estimation of ac plasma display panels from the quantitative investigation of MgO-layer erosion based on microscopic in situ transmission measurement
Authors: Choi Seungho , Byun Hyun Suk , Shin Gil Yong , Oh Soo-ghee , Lee Soonil
Published: February 2003

Quantitative investigation of the MgO-layer erosion in a real ac plasma display panel (PDP) microcell operated at 180 V and 10 kHz was carried out in situ, and real-time using noninvasive and nondestructive microscopic transmission measurements. The main spatial features in the MgO-layer erosion were the formation of two trenches near the electrode edges, the redeposition of the eroded MgO in the midsection between the two trenches and the occurrence of maximum erosion rate at the position where the trench bottom formed. The temporal variation of both the normalized thickness and the erosion rate were dominated by the exponential terms with the identical time constant of 74.6 h for short discharge duration. After the prolonged discharge, the former and the later became constant and linearly decreasing as a function of time, respectively. The lower limit of the lifetime of this PDP cell, which we assume as the time for the total depletion of the electron-beam evaporated MgO layer at the trench bottom, was estimated to be ∼12 000 h from the quantified temporal variation of the normalized thickness.
Characterization of electron emitters for miniature x-ray sources
Authors: Busta H. H. , Chen J. M. , Shen Z. , Jansen K. , Rizkowski S. , Matey J. , Lanzillotto A.
Published: February 2003

Single tip tungsten emitters, nanocrystalline graphite (NCG) emitters, gated silicon field emitter arrays, thoriated tungsten filament emitters, and micromachined n-type polycrystalline silicon thermionic emitters were investigated as potential electron sources for miniature x-ray devices. The emission sources were characterized in a demountable 3.5 mm diameter Schott glass 8250 tube using a 45° cone angle, 1 mm diameter tungsten anode. X-ray characterization was performed in a custom-built shielded system surrounding the tube using an AMPTEX, model XR-100T-cadmium zinc telluride crystal detector. The best results in terms of reliability and recovery from flashover events were obtained with the NCG emitter. Lateral, distal, and rotational x-ray spectra were obtained for the NCG emitter. Initial integration efforts of mounting the x-ray source on the end of a cardiac catheter yielded 15 kV standoff voltages for a 0.2 mm catheter wall thickness.
Effect of catalyst on growth behavior of carbon nanotubes synthesized by microwave heating thermal chemical vapor deposition process
Authors: Cheng Hsiu-Fung , Chuo Yen , Chou Chen-Shien , Huang Jin-Hua , Liu Kuo-Shung , Lin I-Nan
Published: February 2003

Influence of morphology of Fe-catalyst on the microstructure and electron field emission properties of carbon nanotubes were systematically investigated. H2-plasma treatment imposed a most significant effect on the morphology of Fe clusters. The 1200 W H2-plasma treated Fe catalysts are nanosized (40–80 nm), isolated, and uniformly distributed, which result in carbon nanotubes of highest purity and most density population, exhibiting the largest electron field emission capacity (Je=3600 μA/cm2 at 6 V/μm applied field). Too low (1000 W) or too high (1400 W) H2-plasma treated Fe catalysts are interconnected or coarsened particulates, which result in large proportion of carbon soots, in addition to the carbon nanotubes. The electron field emission capacity of the films is thus markedly decreased. The prebaking process before H2-plasma treatment also imposes a marked effect on those characteristics. These results imply that spin coating of Fe(OR)3 is a simple and inexpensive method for producing catalyst of good quality, provided that the Fe(OR)3 was well pretreated.
Field emission properties of phosphorus doped microwave plasma chemical vapor deposition diamond films by ion implantation
Authors: Cho Euo Sik , Park Byung-Gook , Lee Jong Duk , Kwon Sang Jik
Published: February 2003

Phosphorus doped polycrystalline diamond films were grown using ion implantation in various process steps and were structurally and electrically characterized. When the diamond films were implanted after pretreatment or in the course of diamond growth and were grown by microwave plasma chemical vapor deposition, some modified structural characteristics and improved electrical characteristics were obtained. Secondary ion mass spectrometry analyses of some diamond films led to the conclusion that phosphorus ions and defects in the Si–diamond interface play an important role in the enhancement of field emission from diamond films.
Study on dc characteristics of an interesting InP/InGaAs tunneling-emitter bipolar transistor with double heterostructures
Authors: Chen Chun-Yuan , Chiou Wen-Huei , Yen Chih-Hung , Chuang Hung-Ming , Chen Jing-Yuh , Cheng Chin-Chuan , Liu Wen-Chau
Published: February 2003

The dc performances of an interesting InP/InGaAs tunneling-emitter bipolar transistor (TEBT) with double heterostructures are studied and demonstrated. The studied device has a higher breakdown voltage than conventional InP single heterojunction bipolar transistors between the collector and base. The base–collector junction breakdown voltage VBR up to 15.6 V is obtained. Both of the common-emitter and common-base breakdown voltages of the studied device are higher than 10 V. Furthermore, low variations of dc current gains are found as the temperature is increased from 25 to 175 °C. The elimination of knee-shaped characteristics and near unity ideality factors of collector and base currents (ηC and ηB) are obtained due to the use of a δ-doping sheet and spacer layer. In addition, the studied TEBT device has a stable dc current gain distributed regime as the temperature is increased from 25 to 175 °C.
Efficient removers for poly(methylmethacrylate)
Authors: Hang Qingling , Hill Davide A. , Bernstein Gary H.
Published: February 2003

As nanotechnology approaches molecular scales, issues of surface contamination by unremoved resists will play an important role in device fabrication. Electron beam lithography of polymethylmethacrylate (PMMA) resist is still among the most widely used nanofabrication techniques, so it is relevant to study its residual contamination on both exposed and unexposed surfaces using a variety of resist removers. We systematically characterized the effectiveness of several different strippers. Our experiments show that 1,2-dichloroethane is an efficient PMMA remover, and can produce almost the same surface roughness as the original SiO2 surface (i.e., no contamination), whereas the popular PMMA remover, acetone, cannot. Estimates of the polymer–solvent Flory–Huggins interaction parameters and surface–solvent interfacial energy (from contact angle measurements) satisfactorily predict the effectiveness of the solvents. This method should also be applicable to any PMMA-like films on any substrate to find a good surface cleaner.
Thermal and structural deformation and its impact on optical performance of projection optics for extreme ultraviolet lithography
Authors: Li Yanqiu , Ota Kazuya , Murakami Katsuhiko
Published: February 2003

Thermal and structural deformation of mirrors becomes an important consideration for extreme ultraviolet lithography (EUVL) when targeting features of 50 nm and below. Such deformation will contribute to the critical dimension control and decrease the performance of the designed system. Multilayer coated mirrors typically absorb 35%–40% of the in-band radiation, which results in the deformation of mirror figures and degrades the performance of the optics. We have employed several software packages to study these effects. This article presents the results for the EUVL production tool with wafer throughput of eighty 300 mm wafers per hour for the 35 nm technology generation.
Field emission characteristics of self-assembled carbon nanotubes on the gold surface
Authors: Lee J. H. , Heo J. N. , Yi W. K. , Jeong T. W. , Yu SeGi , Lee C. S. , Kim W. S. , Yoo J.-B. , Han H. S. , Kim J. M.
Published: February 2003

A method was studied to fabricate carbon nanotube (CNT) field emitters through self-assembly of thiol-modified CNTs onto a gold-coated substrate. By adsorption through simple immersion of the gold-coated substrate into thiol-modified CNT solution overnight, deposition of CNTs was accomplished. It was found that CNTs were deposited on the substrate as random aggregates of CNT bundles. The population density of CNTs on the gold-coated substrate was varied by controlled CNT concentration in ethanol. The I–V measurement of the self-assembled CNTs shows relatively good field emission characteristics with a low turn-on field (2.5 V/μm) and a high current density (40 μA/cm2 at 3 V/μm). In addition, more-populated CNTs on the substrate produce a higher current density. Therefore, the technique of self-assembly of CNTs on a selected area is expected to be a reliable way to prepare large-size panels with easy process and low cost. These advantages recommend further investigation of the self-assembly of CNTs.
Current image tunneling spectroscopy of chemical vapor deposited diamond films
Authors: Lin I-Nan , Chou Yi-Ping , Chen Tong T. , Cheng Hsiu-Fung
Published: February 2003

The effects of boron doping on the electron field emission properties of diamond films were examined using current image tunneling spectroscopy in atomic force microscopy (AFM). Tunneling current–voltage (It–V) characteristics measured by AFM indicate that incorporation of boron species induces the presence of the impurity state. The films doped with 3 sccm boron (B3) possess the smallest emission barrier (Eb=1.65 eV) and the largest emission ratio (η=38%) among the boron-doped diamond samples. Therefore, B3 diamond films can be turned on at the smallest electric field (E0=8.8 V/μm), exhibiting largest field emission capacity (Je=250 μA/cm2). Restated, the electron field emission behavior of diamond films is closely related to the formation of impurity states due to boron doping.
Investigation of boron penetration through decoupled plasma nitrided gate oxide using backside secondary ion mass spectrometry depth profiling
Authors: Yeo K. L. , Wee A. T. S. , Liu R. , Zhou F. F. , See A.
Published: February 2003

High drive-in temperature during dopant activation of p+-poly metal-oxide-semiconductor field effect transistors causes boron penetration through the thin gate oxide, which degrades the device performance. Conventional secondary ion mass spectrometry (SIMS) depth profiling is unable to accurately analyze boron penetration under rapid thermal annealing conditions due to ion knock-on and mixing effects. With the development of backside SIMS depth profiling technique using SOI wafers [Yeo et al., Surf. Interface Anal. 33, 373 (2002); Runsheim et al., J. Vac. Sci. Technol. B 20, 448 (2002)], quantification of the amount of boron penetration becomes possible. In this article, boron penetration through decoupled plasma nitridation silicon dioxide was studied by performing both front and backside depth profiling using 0.5 keV O2+ with oxygen flooding and 2 keV Cs+ primary ions at oblique incidence in a Cameca IMS-6f SIMS instrument.
Towards a better understanding of the operative mechanisms underlying impurity-free disordering of GaAs: Effect of stress
Authors: Doshi Sachin , Deenapanray Prakash N. K. , Tan H. H. , Jagadish C.
Published: February 2003

The effect of stress on defect creation and diffusion during impurity-free disordering of SiOx-capped n-GaAs epitaxial layers has been investigated using deep level transient spectroscopy. The oxygen content in the SiOx layer and the nature of the stress that it imposes on the GaAs layer were varied by changing the nitrous oxide flow rate, N, during plasma-enhanced chemical vapor deposition of the capping layer. The peak intensity of defects S1 and S4 increased with the increasing nitrous oxide flow rate to exhibit a maximum in the range 80 sccm<N<200 sccm. Any further increase in N resulted in a decrease in peak defect intensity, which reached an almost constant value for N>350 sccm. On the other hand, the peak intensity of S2* increased linearly with N. We have explained the maximum in the intensity of defects S1 and S4 for 80 sccm<N<200 sccm to be due to a corresponding maximum in the compressive stress which is experienced by the capped GaAs layer during annealing. Although the creation of S2*, which we have proposed to be a complex involving the gallium vacancy (VGa), is enhanced with the increasing compressive stress, it also becomes efficiently converted into the arsenic-antisite, AsGa. The compound effect of these opposing mechanisms results in a linear dependence of the peak intensity of S2* on N. This study is to the best of our knowledge the first to provide the evidence for the stress-dependent anti-correlation between VGa- and AsGa-related defects in GaAs. We have also narrowed the origin of S1 to complexes involving arsenic interstitials, Asi, and/or AsGa.
Etching behavior of Si-containing polymers as resist materials for bilayer lithography: The case of poly-dimethyl siloxane
Authors: Tserepi A. , Cordoyiannis G. , Patsis G. P. , Constantoudis V. , Gogolides E. , Valamontes E. S. , Eon D. , Peignon M. C. , Cartry G. , Cardinaud Ch. , Turban G.
Published: February 2003

This work is focused on the plasma development of siloxanes investigated as model Si-containing photoresist components that show a promise for bilayer lithography at 157 nm and other Next Generation Lithography technologies. In such lithography, the image is developed in the top photosensitive polymer and transferred to the (usually thick) organic underlayer by means of O2-based plasma etching. In this work particularly, the issue of line edge roughness (LER) induced by transfer etching and its reduction by means of plasma processing optimization is addressed. The experimental results reveal that low values of line-edge roughness are obtained in a high-density plasma reactor, if an F- but not O-containing etching first step is used in appropriate plasma conditions. The effect of different etching chemistries and processing conditions on imaging layer roughness formation is demonstrated with the aid of scanning electron microscopy images and image analysis for quantifying LER, and atomic force microscopy (AFM) for measuring surface roughness. X-ray photoelectron spectroscopy analysis of etched PDMS is used to show the evolution of the chemical modification of the PDMS layer, to measure the top oxide thickness, and to correlate both to processing conditions. In situ interferometry and ellipsometry are used to determine the etch resistance of the imaging PDMS layer and the selectivity of the transfer etching process. It is demonstrated that optimum LER correlates well with plasma processing conditions that ensure a nonselective first etching step prior to a highly selective main etching.
Photoresist etch resistance enhancement using novel polycarbocyclic derivatives as additives
Authors: Gogolides Evangelos , Argitis Panagiotis , Couladouros Elias A. , Vidali Veroniki P. , Vasilopoulou Maria , Cordoyiannis George , Diakoumakos Constantinos D. , Tserepi Angeliki
Published: February 2003

In house synthesized mixed derivatives containing at least two carbocycles per molecule from the group of anthracenes, adamantanes and steroids with functionalized carbon chains are used as modifiers of resist properties and especially etch resistance enhancement and absorption characteristics. Etch resistance enhancement is demonstrated in oxygen, fluorine, and chlorine-containing plasmas under reactive ion etching and inductively coupled plasma etching conditions for poly(methyl-methacrylate) and a chemically amplified, positive-tone, methacrylate-based 193 nm photoresist formulation. High resolution experiments show that the proposed additives do not adversely affect the lithographic properties of the photoresists. The additive role is explained with empirical etch parameters such as the Ohnishi number and the ring parameter.
Formation of low resistivity alpha Ta by ion beam sputtering
Authors: Zhang Jinqiu , Huai Yiming , Chen Lifan , Zhang Jing
Published: February 2003

The properties of tantalum thin film prepared by ion beam sputtering with Xe ions (0.6–1.5 KV) have been investigated. β-Ta thin films with high resistivity (170 μΩ cm) on Si substrate were obtained without Cr underlayer. With Cr underlayer, however, a body-centered-cubic phase (bcc) α-Ta thin film with low resistivity (20 μΩ cm) has been successfully obtained at room temperature. The experimental results indicate that the Cr underlayer plays an important role in α-Ta formation and that the critical thickness of Cr is 20 Å. Properties of α-Ta are also influenced by Ta thickness and ion beam deposition process conditions. α-Ta with lower resistivity was achieved by using approximate beam energy of 1000 eV and beam current of 150 mA. X-ray diffraction analysis indicates that changes in resistivity can be attributed to changes in microstructure that is influenced by the ion beam conditions.
Modeling of field emission nanotriodes with carbon nanotube emitters
Authors: Nicolaescu D. , Filip V. , Kanemaru S. , Itoh J.
Published: February 2003

Films of vertically aligned carbon nanotubes (CNT’s) have recently beeen grown within patterned areas, making them suitable as field emitters in many applications. In this article, we propose and model a nanotriode using CNT’s as emitters. The overall device dimensions are around 100 nm. The electric-field distribution in the nanotriode has been computed using the commercial software package Simion 3D 7.0. A special discussion is devoted to the nanotube tip electric-field screening by the neighboring nanotubes in the film. It is outlined that the nanotube film density and the CNT’s height distribution can greatly change the local field values. Film electron emission properties are enhanced for regular arrays of parallel nanotubes with the same height, for which an optimum CNT film density has been shown to exist. The CNT emission current has been computed using a recently developed model that takes into account the low dimensionality of the CNT electronic system. The device characteristics have been calculated as a function of the device geometry and its functional parameters.
High-temperature electron emission from diamond films
Authors: Shin S. H. , Fisher T. S. , Walker D. G. , Strauss A. M. , Kang W. P. , Davidson J. L.
Published: February 2003

This work examines electron field-emission characteristics of polycrystalline diamond films at elevated temperatures. Diamond is an excellent material as a field emitter because of its exceptional mechanical hardness and chemical inertness. The motivation behind this study involves the use of field emitters in applications where high temperatures exist. Nitrogen-doped polycrystalline diamond films were grown by plasma-enhanced chemical-vapor deposition. To investigate the effect of increased temperatures on field emission, current–voltage measurements were taken from the same diamond film at varying temperatures. Results from these measurements indicate a decrease in the turn-on voltage with increasing temperature. Further analysis of the temperature dependence of emission is achieved through parameter estimation of the effective emitting area, field enhancement factor, and work function. These results suggest that thermally excited electrons are responsible for improved emission at high temperature.
Diffractive x-ray optics using production fabrication methods
Authors: Stein A. , Jacobsen C. , Evans-Lutterodt K. , Tennant D. M. , Bogart G. , Klemens F. , Ocola L. E. , Choi B. J. , Sreenivasan S. V.
Published: February 2003

Zone plates are the key focusing element for many x-ray (7–20 keV) and soft x-ray (200–500 eV) applications, yet, production with electron-beam lithography poses obstacles to their widespread availability. In addition, fabrication processes to date have limited the studies of amplitude Bragg–Fresnel-type elements in the hard x-ray regime. We report new processes that couple 100 keV electron-beam lithography with established production methods to achieve two goals: (1) improving the overall yield and volume of ultrahigh-resolution soft x-ray zone plates and (2) applying deep silicon etching techniques to extend the state of the art in high aspect ratio Bragg–Fresnel optics required to create high efficiency focusing of high-energy x rays.
Aspect ratio dependent strains in InAs/InP quantum dots measured by synchrotron radiation x-ray diffraction
Authors: Kim Kihong , Yoon Sukho , Yoon Euijoon , Koo Yang Mo , Lee Jong-Lam
Published: February 2003

Uncapped self-assembled InAs quantum dots (QDs) grown on InP (001) were studied by synchrotron x-ray diffraction. Reciprocal lattice mapping of the (004) InAs peak shows the strain relaxation behavior with InAs coverage and coalescence at various growth conditions. The aspect ratio (height/diameter) of QDs increases linearly with decreasing strain in QDs in the perpendicular direction before complete strain relaxation by dot coalescence and misfit dislocation generation. The full widths at half maximum of InAs (004) peaks can be used to extract the average height of InAs QDs, which is in good agreement with that directly obtained by atomic force microscopy.
Enhancement of emission characteristics for field-emitter arrays by optimizing the etched feature of the gate electrode
Authors: Kim Hoon , Seo Sang-Won , Lee Joo-Won , Park Jong-Won , Lee Yun-Hi , Jang Jin , Ju Byeong-Kwon
Published: February 2003

The etched features of thin chromium (Cr) films deposited on SiO2–Si substrate were investigated as a function of the substrate temperature during rf sputtering deposition. In this work, the changes of both the grain structures and crystallographic orientations of sputtered Cr films as a function of substrate temperature were examined, and we found that the tapering angle θt of thin Cr film after reactive ion etching depends on the deposition condition, especially the substrate temperature during the rf sputtering process. Based on the obtained results, we fabricated two kinds of Cr-grated Mo-tip field-emitter arrays (FEAs): the first kind is a FEA with tapered-gate electrode (tapered-gated FEA, θt⩽90°) and the second kind is a FEA with taper-free gate electrode (nontapered-gated FEA, θt=90°). We obtained more emission current than that of tapered-gated FEAs, whereas the gate leakage current of nontapered-gated FEAs was almost the same value as compared to that of tapered-gated FEAs. Because of the optimized etched shape of the gated electrode, the field conversion factor β of the nontapered-gated FEAs increased to 32% more than that of tapered-gated FEAs. Furthermore, the total transconductance Gm of nontapered-gated FEAs increased to 20% without increasing the packing density of FEAs.