bluuebunny/crossref_metadata_2025 huggingface dataset:
Determining effective dielectric thicknesses of metal-oxide-semiconductor structures in accumulation mode
Authors: Hu C.-Y. , Kencke D. L. , Banerjee S. , Bandyopadhyay B. , Ibok E. , Garg S.
Published: July 2002

Metal-oxide-semiconductor (MOS) capacitance–voltage (C–V) characteristics in the accumulation mode have been measured and simulated for polycrystalline Si gate MOS capacitors with various oxide thicknesses (40–200 Å) on p-type (100) Si substrates. The discrepancy between experimental data and theoretical prediction by classical MOS theories is clarified by taking quantization effects into account. The experimentally determined ‘‘effective dielectric thicknesses’’ in the semiconductors are found to be in good agreement with the values calculated from quantization effects for MOS capacitors with thinner oxides (<80 Å). The effective dielectric thicknesses at oxide electric fields of 2–6 MV/cm have been determined to be 2–3 Å larger for the quantum mechanical case than for the classical case.
On the origin of oval defects in metalorganic molecular beam epitaxy of InP
Authors: Cotta M. A. , Hamm R. A. , Chu S. N. G. , Harriott L. R. , Temkin H.
Published: July 2002

We have studied the dependence of oval-shaped defects on growth conditions during metalorganic molecular beam epitaxy of InP. The density of oval defects is independent of growth conditions but strongly dependent on the initial substrate surface preparation. Contaminants existing on the surface prior to growth are indicated as the likely cause of oval defect formation due to local enhancement of metalorganic molecules cracking on the surface and the subsequent formation of group III rich structures. High densities of such defects are shown to degrade the optical properties of InGaAs quantum wells.
Quantum cascade unipolar intersubband light emitting diodes in the 8–13 μm wavelength region
Authors: Sirtori Carlo , Capasso Federico , Faist Jérôme , Sivco Deborah L. , Hutchinson Albert L. , Cho Alfred Y.
Published: July 2002

An intersubband electroluminescent light source in the 8–13 μm spectral region is reported. The structure was grown by molecular beam epitaxy in the lattice matched AlInAs/GaInAs material system and consists of coupled-quantum-well active regions alternated with compositionally graded electron injecting regions. The device operates in the temperature range from 10 to 200 K with measured integrated optical powers up to 6 nW. The peak of the electroluminescent spectrum blue shifts linearly with current due to the Stark effect. From these data and straightforward electrostatic considerations we obtain the intersubband nonradiative electron lifetime, in good agreement with the calculations.
A capacitive probe array for measurements of ionization growth
Authors: Choi P. , Favre M.
Published: July 2002

The design and construction of a novel capacitive probe array to directly measure the ionization growth in high-voltage discharges is presented. By optimizing the design geometry, the probe output is made to be dependent only on the variation of charge development or potential changes at the vicinity of the probe in the interelectrode space. A set of these probes was used in an experiment to allow the time and space development of a virtual anode to be directly observed.
A simple method to monitor the intensity profile of a pulsed laser beam with micrometer resolution
Authors: Huth-Fehre T. , Westman A. , Sundqvist B. U. R.
Published: July 2002

A simple method is demonstrated for monitoring the time integrated intensity profile of a pulsed laser beam based on desorption from homogeneous films of Rhodamine 6G dye. The method offers micrometer resolution, and for the case of a Gaussian beam profile the fluence scale may be calibrated.
On the importance of magnetic periodicity in permanent magnet undulators
Authors: Gore B. W. , Asgekar V. B.
Published: July 2002

In permanent magnet undulators, dimensional variations in the magnet blocks are responsible for displacing the magnets from their ideal positions. These displacements, which can be characterized in terms of the periodicity of the arrangement of the magnets, perturb the undulator field. It is shown that the deviations in the undulator field can be reduced to the desired level by adding two cost factors, based on the uniformity in periodicity, in the cost function used in the simulated annealing technique to determine the placement of the magnet blocks.
Construction and development of the JAERI 18 GHz electron cyclotron resonance ion source
Authors: Yokota W. , Saitoh Y. , Ishii Y. , Nara T. , Arakawa K. , Wu Y.
Published: July 2002

An 18 GHz electron cyclotron resonance ion source for multiply charged ions was constructed and is now in operation. A new distribution of the mirror field was adopted, and minimum strength is varied by a solenoid coil installed between the mirror coils. The measured mirror field distribution is close to the designed distribution and its maximum strength exceeds 1.4 T. The source is now being tuned by use of Ar ion generation. The relatively high base pressure in the plasma chamber has been improved by installing an additional vacuum pump. The source performance has been maturing gradually with the vacuum and Ar ions with charge states of up to 13+ have been observed so far.
Extraction studies on electron cyclotron resonance ion sources
Authors: Leroy R. , Mandin J. , Bertrand P. , Lecesne N. , Pacquet J. Y. , Robert E. , Sortais P. , Villari A. C. C.
Published: July 2002

The production of radioactive ion beams in the SPIRAL project requires very efficient ion sources delivering beams with good optical properties. To improve these properties, the extraction conditions are under study. This paper will present the last results obtained with a new extraction system and will compare them to a numerical simulation. This comparison shows that the axial magnetic field influences the multicharged ion beam if the space charge during the acceleration is not compensated. In order to decrease the axial magnetic field effect on the extraction zone, a parallel beam can be formed with a multielectrode system. The first tests of this system will be presented.
The production of ions of solids from the PIG source with an additional anode
Authors: Bogomolov S. L. , Kutner V. B. , Tretyakov Yu. P.
Published: July 2002

In this paper we report the results of production of ions of solids from the PIG source with an additional anode and solid material feed by cathode sputtering. The investigations were performed at the test bench and at the U-400 cyclotron. Two versions of the ion source with different dispositions of the sputtering electrode were studied. In the first version the sputtering electrode is introduced into the discharge chamber through the wall opposite to the emission slit, the second version has lateral disposition of the sputtering electrode. The influence of the potential of an additional anode on the total extracted current and charge state distribution was studied at the test bench for both versions. The results of the test of the ion source with lateral disposition of the sputtering electrode at the U-400 cyclotron are reported.
Isotope effects in an electron beam excited negative ion source
Authors: Fukumasa Osamu , Nishimura Hideki , Sakiyama Satoshi , Kimoto Tatsushi
Published: July 2002

Results which focus on comparing operation in hydrogen and deuterium are presented. Measurements of plasma parameters, including electron density, electron temperature, electron energy distribution function and extracted negative ion current, have been made in the source and extractor regions of an electron beam excited negative ion source. For the same operating conditions, negative ion current is found to be higher in deuterium than in hydrogen.
The origin of sample memory in the Chalk River accelerator mass spectrometry sputter ion source
Authors: Koslowsky V. T. , Andrews H. R. , Davies W. G. , Forster J. S. , Imahori Y.
Published: July 2002

The origin of memory effects in the Chalk River accelerator mass spectrometry sputter ion source has been studied by tracer and elastic-recoil-detection surface analysis techniques. For 36Cl measurements, the results indicate that the memory arises from contamination of the region immediately surrounding the sample and that it can be mitigated by operating this portion of the ion source above 350 °C. This has reduced memory effects by a factor of 10 or more and has resulted in a similar improvement in background.
Installation of an on-line Lamb–shift spin–filter polarimeter in the Triangle Universities Nuclear Laboratory atomic beam polarized ion source (abstract)a)
Authors: Mendez A. J. , Roper C. D. , Dunham J. D. , Clegg T. B.
Published: July 2002

An atomic beam polarized ion source, used heavily since 1989 for producing polarized H± and D± beams for experiments between 25 keV and 20 MeV, have been modified to accept a Lamb–shift, spin–filter polarimeter. In this source, polarized ground-state H or D atoms enter an electron cyclotron resonance ionizer where they are stripped to produce an outgoing positive polarized ion beam. When negative ions are desired, cesium vapor is introduced into a downstream charge-exchange canal. The polarimeter, based on an atomic physics concept first developed to produce nuclear–spin-polarized beams at Los Alamos, is designed to monitor the polarization of 2S1/2 metastable H or D atoms emerging from this cesium canal. Metastable 2S1/2 atoms created by electron pickup in a collision with cesium are ‘‘filtered’’ by the polarimeter according to a magnetic substate, as the magnetic field imposed on the polarimeter cavity is tuned between 53 and 61 mT. Photons produced by subsequent quenching of these filtered atoms to their ground state are monitored downstream by a phototube to reveal the magnetic substate population of the incident positive beam. To install the polarimeter cavity and phototube assembly, the existing polarized ion source was lengthened by 30 cm. Installation is complete, its calibration has been checked, and initial impressions gained from its use are presented.
Hot and warm electron energy distribution at different electron cyclotron resonance ion source operation regimes
Authors: Friedlein R. , Tyrroff H. , Henke D. , Zippe C. , Zschornack G.
Published: July 2002

High charge states of heavy ions inside the electron cyclotron resonance plasma are produced by hot and warm electrons with energies above 3 keV. The slope of the electron energy distribution function and the density of these populations were obtained from bremsstrahlung spectra emitted by the 7.5 GHz Electron Cyclotron Resonance Ion Source of the Forschungszentrum Rossendorf measured with a HP Ge solid state detector. For this a new deconvolution method has been used. The operating condition of the ion source influences the behavior of the electrons. Mixing in of light gases to the discharge strongly increases the electron density.
Pulsed magnetic field-electron cyclotron resonance ion source operation
Authors: Mühle C. , Ratzinger U. , Jöst G. , Leible K. , Schennach S. , Wolf B. H.
Published: July 2002

The pulsed magnetic field (PuMa)-electron cyclotron resonance (ECR) ion source uses a pulsed coil to improve the peak current by opening the magnetic bottle along the beam axis. After demonstration of the principle of the pulsed magnetic extraction, the ion source was tested with different gases. We received promising results from helium to krypton. The influence of the current in the pulsed coil on the analyzed ion current was measured. With increased current levels within the pulsed coil not only the pulse height of the PuMa pulse, but the pulse length can also be controlled. By using the pulsed coil the maximum of the charge state distribution can be shifted to higher charge states.
Beam tests of a compact 2.45 GHz electron cyclotron resonance ion source
Authors: Shibuya S. , Fukushima T. , Kimura T. , Muramatsu M. , Kitagawa A. , Yamada S.
Published: July 2002

A compact 2.45 GHz ECR ion source has been developed at National Institute of Radiological Sciences (NIRS). The source was designed to provide doubly charged carbon ions, aiming at easy maintenance of the source. A set of permanent magnets was adopted to realize a minimum B structure. In pulse operation with a duty factor of 5%, the beam performance was measured with He, CO2, CH4, and N2 gases. With CO2 gas, analyzed beam currents are 160 and 15 eμA for C+ and C2+, respectively. Through the measurement of the microwave amplitude in the plasma chamber, it was found that the microwave power was not transmitted into the plasma chamber efficiently.
Design parameters, goals, and status of the new ATLAS ECR ion source
Authors: Pardo R. C. , Harkewicz R. , Billquist P. J. , Lyneis C. M. , Xie Z. Q.
Published: July 2002

A new 14 GHz ECR ion source for the ATLAS facility is under construction. The new source is an evolution of the 14 GHz AECR Lawrence Berkeley source. The new source will feature an all-aluminum hexapole main chamber and enhanced peak radial and solenoid magnetic fields compared to the existing AECR. Most of the other design features of the existing source are maintained in this design. The new source will be mounted on a new 300 kV high-voltage platform in order to match the velocity requirements of the existing PII injector linac. Achieving the very precise goal of a few electrical microamps of 238U+33 from this source will allow the ATLAS facility to provide Coulomb-barrier energies of uranium without the use of an additional stripper foil and will significantly enhance the capabilities of ATLAS for the heaviest of beams. The project status and more details of the source system design are discussed.
Present status of the 2.45 GHz ECRIS for a light ion accelerator at IAP
Authors: Cojocaru G. , Martin D. , Ivanov E. , Macovei M.
Published: July 2002

This article presents a 2.45 GHz electron cyclotron resonance ion source which is under construction at the Institute of Atomic Physics Bucharest, Romania. It will be used as an injector into an existing linac for light ions and is a compact version of a similar source, for which we have obtained the magnetic system by superimposing an axial magnetic field generated by two solenoids and a radial magnetic field generated by a permanent magnet hexapole. For the compact version we have employed two rings made of permanent magnets for the axial magnetic field and the same type of hexapole for the radial field. This second version will work on a high voltage platform. The calculation, design, and construction of the two minimum magnetic field structures (B minimum) are presented. These sources have a special microwave antenna, of a helix type, allowing a much smaller diameter plasma chamber than is usually used for the employed microwaves. The microwave system is also presented. The first experiments were made with an Ar plasma.
Optimization of U4+ output of the MEVVA ion source
Authors: Batalin V. A. , Kuybeda R. P. , Kulevoy T. V. , Petrenko S. V.
Published: July 2002

The quadruply charged U4+ ion component of the uranium ion beam produced by the Institute for Theoretical and Experimental Physics MEVVA ion source has been investigated and increased. An independent, additional power supply has been connected to the trigger electrode, by means of which the U4+ current was increased up to 30%–40% of the total beam current at the injector output. The charge state distribution was measured by time-of-flight and magnetic analysis methods. An accelerated U4+ ion beam with a mean pulse current up to 50 mA in the bunch has been obtained at the TIPr-1 linac.
The insertion of a small Mevva source inside an electron cyclotron resonance: Status report
Authors: Cavenago M. , Vassiliev A.
Published: July 2002

A miniaturized Mevva source, designed to be inserted in an electron cyclotron resonance (ECR) source in order to sputter metals, was proposed to supplement our ECR source Alice. The major problem was to control the Mevva arc at the low level of current (20–30 A for Al, Cu), which are required to limit metal consumption. Installation of our Mevva in a separate test stand was completed. Extensive electrical tests are here reported, discussing components that were rebuilt and optimized during experiments. The improvement in trigger voltage (10 kV) and rise time (3 μs) obtained by an air transformer, with little help from a ferrite core, allowed a reliable arc start-up. Increasing the main voltage was also important, as was evident from the new ferrite transformer (giving 3.5 kV instead of 2 kV) and from the detailed shape of arc voltage in some shots, where wide fluctuation appeared. A neutral beam spectrometer for the MetAlice experiment is being developed. Perspective of schematic improvement and of installation in Alice are discussed.
Development of a compact negative ion source using powdery samples
Authors: Wada Motoi , Kawano Hiroyuki , Sasao Mamiko
Published: July 2002

A compact negative ion source that can be attached to a standard 1.33 in. copper-gasket flange has been developed. Negative ions of hydrogen (H−) were produced from LiH powder by electron stimulated desorption. With the input electrical power of less than 8 W, 1 nA mass-separated current of the H beam was extracted from the source. The impurity ion current extracted with the H− ion was less than 2%. The source was stable for more than 10 h with little gas emission.
An H− source for ESS
Authors: Volk K. , Klein H. , Lakatos A. , Maaser A. , Weber M.
Published: July 2002

A new version of the high efficiency source is being developed for the European Spallation Source. The goal of these experiments is to produce a nearly pure H− ion beam with a low electron to H− ratio and high current (70 mA). To achieve this, the discharge chamber is divided into two parts of different plasma parameters by means of a filter magnetic field. Furthermore, the plasma chamber is aligned unsymmetrically with respect to the z axis of the extractor. We obtained a current density of 10 mA/cm2 for an arc power as small as 1 kW. In preliminary experiments, a beam of 10 mA was extracted at an extraction voltage of 8 kV (1.8% impurities). Measurements of the beam current density, electron to H− ratio, and the ion composition for a wide range of discharge conditions will be presented in this article.
Development of a toroidal-filter H− ion source
Authors: Stevens Ralph R. , York R. L. , Geisik C. , Swenson David R.
Published: July 2002

High brightness H− ion beams will be required for the next generation of accelerator-driven, neutron spallation sources. Volume H− ion sources have the potential for providing these beams at a high duty factor with moderate beam currents and with the long-term operational stability and reliability needed. We report on the results of a continuing study of the Los Alamos National Laboratory version of a toroidal-filter, volume H− ion source which was designed to provide such beams. The H− beam current, emittance, and electron loading have been measured with the source equipped with a 3- and a 10-mm-diam emission aperture and with several configurations of the plasma filter. The results are compared to beam simulations.
Modeling microwave conversion to longitudinal waves in small electron cyclotron resonance plasmas
Authors: Cavenago M.
Published: July 2002

The propagation of the transverse microwave Ex Ey into electron cyclotron resonance (ECR) plasmas is studied (with simplified plasma dynamics), emphasizing that plasma dimensions and wavelength λ are comparable, which is the case with most ion sources. The coupling to the Ez field is included. A simple system of coupled equations is found and a closed fourth-order differential equation is obtained. Nonpropagating modes are easily solved. Numerical solutions are shown for propagating modes applied to the ECR Alice dimension (radius 3 cm, λ≂2 cm). A simplified formula for the cavity admittance is given, involving the matching of the guide to cavity, where each mode contribution is weighted; weights are computed for the circular waveguide case.
Multicharged ion sources for pulsed accelerators (invited)
Authors: Haseroth H. , Hill C. E.
Published: July 2002

The relatively low duty cycle of pulsed accelerators can give rise to problems in matching the characteristics of multicharged ion sources to the beam intensity required by the user. Heavy ion physics interests, especially in the heavy ion colliders, demand more and more intensity while the accelerator designers require higher charge states to ease their machine problems. Various options for ion sources for present and future heavy ion accelerators are presented.
Peristaltic ion source (invited)
Authors: Brown I. G. , Anders A. , Anders S. , Dickinson M. R. , MacGill R. A.
Published: July 2002

Conventional ion sources generate energetic ion beams by accelerating the plasma-produced ions through a voltage drop at the extractor, and since it is usual that the ion beam is to propagate in a space which is at ground potential, the plasma source is biased at extractor voltage. For high ion beam energy the plasma source and electrical systems need to be raised to high voltage, a task that adds considerable complexity and expense to the total ion source system. We have developed a system which though forming energetic ion beams at ground potential as usual, operates with the plasma source and electronics at ground potential also. Plasma produced by a nearby source streams into a gridded chamber that is repetitively pulsed from ground to high positive potential, sequentially accepting plasma into its interior region and ejecting it energetically. We call the device a peristaltic ion source. In preliminary tests we’ve produced nitrogen and titanium ion beams at energies from 1 to 40 keV. Here we describe the philosophy behind the approach, the test embodiment that we have made, and some preliminary results.
Status of ion sources for the Heavy Ion Medical Accelerator HIMAC
Authors: Kitagawa A. , Yamada S. , Muramatsu M. , Ogawa H. , Sato Y. , Torikoshi M. , Yoshizawa J. , Sekiguchi M. , Hattori T. , Honda Y. , Kimura T. , Kobayashi C. , Matsushita H. , Okada T. , Sakamoto H. , Shibuya S. , Yamamoto M. , Sawada K.
Published: July 2002

The Heavy Ion Medical Accelerator in Chiba (HIMAC) at National Institute of Radiological Sciences (NIRS) is the first heavy-ion accelerator complex dedicated to cancer therapy. HIMAC is equipped with two kinds of ion sources. The PIG ion source is an indirectly heated cathode type, which is operated with a very low-duty factor. The ECR ion source has a single closed ECR zone with 10 GHz microwaves. Both sources realize good stability and reproducibility with easy operation, and satisfy the requirements for radiotherapy. They have been successfully used for clinical trials since June of 1994, and several tens of cancer patients have already been treated with 290–400 MeV/u carbon beams.
Design aspects of the Debrecen ECR ion source
Authors: Biri S. , Vámosi J.
Published: July 2002

In the ATOMKI a 14 GHz ECR ion source has been designed and is being built. The main design aspects and the results of some checking measurements are briefly summarized. The designing of an extraction-focusing optics is shown in detail. Based on a theoretical model (developed by the authors earlier), the axial distribution of the electrostatic potential in the extraction region must be a superposition of linear and cosinusoidal parts. The behavior of such an extraction optics has been checked experimentally on a low-charged hollow-cathode ion source. The development and usage of the TrapCAD code has also been continuing. The code is suitable to visualize the magnetic structure of any magnetic bottle in 3D and also to simulate the charged particle movement in it. The code—with some restrictions—is suitable for plasma modeling as well.
Small microwave ion source for an ion implanter
Authors: Song Zhizhong , Jiang Dong , Yu Jinxiang
Published: July 2002

Three kinds of small 24.5 GHz microwave ion sources have been developed for a middle current implanter. The magnetic fields of the sources are produced by an electromagnetic coil, electromagnetic coil added permanent magnet ring, and permanent magnet rings, respectively. Adopting single-hole accel–decel extraction electrodes with about 5 mA of nitrogen and oxygen, ion current can be extracted from them. The microwave power consumption is about 100–200 W.
Effusive flow delay times for gaseous species in a compact rf ion source (abstract)
Authors: Welton R. F. , Piotrowski A. , Alton G. D. , Murray S. N.
Published: July 2002

A rf ion source is presently being developed and evaluated as a potential candidate for use in generating radioactive ion beams (RIBs) for the experimental research program at the Holifield Radioactive Ion Beam Facility (HRIBF) now under construction at the Oak Ridge National Laboratory. For this application, any time delays that are excessively long with respect to the half-life of the radioactive species of interest can result in significant losses of the RIB intensity; therefore the times for effusive flow through the ion source are of fundamental importance since they set limits on the minimum half-life of radioactive species that can be processed in the source. Complementary experimental and computational techniques have been developed which can be used to determine the characteristic delay times for gaseous species in low-pressure ion source assemblies. These techniques are used to characterize the effusive delay times for the stable counterparts of various atomic and molecular radioactive species in the ORNL-rf source: He, Ne, Ar, Kr, Xe, H2, CO, CO2, N2, N2O, and O2.
A novel rectilinear ion source for direct metal ion beam deposition (abstract)
Authors: Kim S. I.
Published: July 2002

A novel rectilinear ion beam disposition technique has been developed for the direct metal ion beam deposition over a large area. The technology is based on the patent pending solid-state cesium ion beam technology. This technique has several unique advantages: (1) Due to the rectilinear shape of the ion beam, the ion beam length is expandable to any size up to several meters; (2) The technique uses no carrier gas or gas medium to generate the ion beams, thus, it is very compact and economical; (3) It is capable of producing various negative metal ion beams such as C, Si, Au, Ni, Fe, Mo, W, etc.; (4) The ion source is operating in a low energy range (10–500 eV) and it is ideal for the direct ion beam disposition. The prototype of the ion source has produced superior quality amorphous diamond films which exhibited superior hardness (≳60 GPa), low wear rate (<108 mm3/Nm), low friction coefficient (<0.1) and high transparency. Furthermore the coatings contain no hydrocarbon impurities, and exhibit atomically smooth surfaces (<1 nm Ra) on the as-grown materials.
Development of an array calorimeter detector and measurement of KrF laser intensity
Authors: Qi Feng , Kun Gang , Jing Li , Yushang Shang , Naiyan Wang
Published: July 2002

A new array calorimeter detector has been developed and was used to measure the spatial profile of a KrF laser with 300 J energy and a 267 mm diameter in near field. The detector contains 441 (21×21) calorimeters. A tantalum foil is used as the absorber. The boiling of liquid nitrogen is used as the reference temperature of the thermocouples, as it is both insulating and stable. Thus, it is the basis of the physical measurement in the sub-μV–mV level with a multithermocouple detector. The response of the tantalum foil is linear in the range of fluence from 30 mJ/cm2 to 1.1 J/cm2. The experimental results show that the spatial profile of the KrF laser pumped by two side electron beams is saddle shaped with a valley at the center and one peak at each side of the center on the coaxial line of electron beams in the near field. With a decrease of the laser’s gas pressure, the distribution become more even rather than flat.
A new radiative heater for high Tc thin film growth
Authors: Badaye M. , Gardner M. , Wong A. , Dosanjh P. , Bonn D. , Hardy W. N.
Published: July 2002

The design of a new radiative heater for the growth of oxide thin films is presented. A blackbody cavity approach has been used to eliminate the large temperature variations usually observed during the growth of high Tc (HTC) superconducting thin films. Results show that this simple and inexpensive design enables one to work without the need for in situ monitoring and constant adjustment of the substrate temperature. The performance of the new heater is demonstrated by the growth of excellent quality HTC thin films.
Quantitative investigation of localized ion irradiation effects in n-channel metal-oxide-semiconductor field-effect transistors using single ion microprobe
Authors: Koh Meishoku , Horita Katsuyuki , Shigeta Bungo , Igarashi Kai , Matsukawa Takashi , Tanii Takashi , Mori Shigetaka , Ohdomari Iwao
Published: July 2002

Localized ion irradiation effects in n-channel metal-oxide-semiconductor field-effect transistor (n-ch MOSFET) have been investigated quantitatively by means of both the single ion microprobe (SIMP) and single ion beam induced charge (SIBIC) imaging. An extremely large leakage current in the subthreshold gate voltage Vg–drain current Id characteristics (Vg< threshold voltage Vth) have been induced by exposing a small fraction of the MOSFET gate area to MeV He single ions, while the turn-on Vg–Id characteristics (Vg≳Vth) have scarcely been affected. The causes of the large leakage current in the subthreshold region induced by the localized ion irradiation have been discussed.
Microstructure of epitaxial potassium niobate thin films prepared by metalorganic chemical vapor deposition
Authors: Nystrom M. J. , Wessels B. W. , Chen J. , Marks T. J.
Published: July 2002

The microstructure of (001)p-oriented (subscript p indicates the choice of a pseudocubic unit cell) potassium niobate (KNbO3) thin films grown by metalorganic chemical vapor deposition on (100)p lanthanum aluminate and having a large second-order nonlinear optical response is examined. Transmission electron microscopy reveals the films to be epitaxial and the film/substrate interface to be abrupt and semicoherent. The strain between the film and substrate due to the 5% lattice constant mismatch is accommodated by formation of an array of misfit dislocations as well as 60° and 120° ferroelectric microdomains. The domains are located in a 20 nm thick region adjacent to the interface. Beyond the multidomain region, the film is free of significant defects.
Fabrication of silicon nanopillars containing polycrystalline silicon/insulator multilayer structures
Authors: Fukuda Hiroshi , Hoyt J. L. , McCord M. A. , Pease R. F. W.
Published: July 2002

A new approach to three-dimensional nanostructures is discussed with the goal of fabricating vertical, ultrasmall tunneling junctions suitable for single electron devices. Pillars consisting of multiple layers of polycrystalline silicon (polysilicon) (∼10 nm thick) and silicon nitride (∼2 nm thick) were laterally oxidized. The fabrication of vertically stacked silicon nanoislands, with dimensions on the order of 10 nm in all three directions, connected by thin silicon nitride layers, is demonstrated. The saturation of the polysilicon core diameter during the lateral pillar oxidation process is clearly observed, confirming the self-limiting effect for polysilicon pillars. This approach allows the fabrication of three-dimensional nanostructures using conventional silicon processing equipment.
A tunneling field-effect transistor with 25 nm metallurgical channel length
Authors: Wang Fu-Cheng , Zhang W. E. , Yang C. H. , Yang M. J. , Bennett B. R. , Wilson R. A. , Stone D. R.
Published: July 2002

A tunneling field-effect transistor with an ultrashort channel-length of 25 nm has been experimentally realized using InAs/AlSb heterostructures. The conduction between the source and the drain is through a sequential process, including tunneling and drift-diffusion mechanisms. According to its operating principle, the transistor is inherently free of the conventional short-channel effects. The results demonstrate a new scheme of building nanometer-scale transistors.
Bistable operation of coupled in-plane and oxide-confined vertical-cavity laser 1×N routing switches
Authors: Shire D. B. , Tang C. L. , Parker M. A. , Lei C. , Hodge L.
Published: July 2002

We report on the observation of two-mode intensity bistability in intracavity-coupled in-plane lasers and oxide-confined vertical-cavity surface emitting lasers (VCSELs) operating under room-temperature CW conditions.
Synchrotron radiation micro-Fourier transform infrared spectroscopy applied to photoresist imaging
Authors: Ocola L. E. , Cerrina F. , May Tim
Published: July 2002

The application of a micro-Fourier transform infrared, (μ-FTIR), spectroscopic system, using synchrotron radiation as a light source, for photoresist chemical analysis has been investigated. The better signal to noise due to the high brightness of the infrared radiation from the synchrotron permits higher spatial resolution scans than with a conventional glowbar. This permits a new technique of μ-FTIR spectroscopy, which potentially can get close to diffraction limited resolution, with high chemical sensitivity, for mid-IR wavelengths ranging from 2.3 μm (4400 cm−1) to 9 μm (1100 cm−1). An example of application of imaging the local chemistry changes of a chemically amplified photoresist with post-exposure bake shows the exciting capability of this technique for nondestructive resist exposure process control.
Carbon-induced undersaturation of silicon self-interstitials
Authors: Scholz R. , Gösele U. , Huh J.-Y. , Tan T. Y.
Published: July 2002

Carbon diffusion into silicon is well behaved and does not generate any nonequilibrium point defects. We show that, in contrast, the diffusion of carbon incorporated in silicon well above its solid solubility will cause an undersaturation of silicon self-interstitials, which in turn may cause retarded diffusion of boron. In addition, we predict that due to this undersaturation, the diffusion of built-in carbon spikes will lead to strongly non-Gaussian concentration profiles.
Fused vertical couplers
Authors: Liu Bin , Shakouri Ali , Abraham Patrick , Kim Boo-Gyoun , Jackson Andrew W. , Bowers John E.
Published: July 2002

A vertical directional coupler fabricated using wafer fusion is demonstrated with a very short coupling length of 62 μm. The optical propagation loss introduced by the fused layer is investigated. An excess loss of 1.1 dB/cm at 1.55 μm was measured for waveguides which incorporate a fused junction near the core region. Fused vertical couplers make it possible to realize three-dimensional waveguide structures and compact switching arrays and they solve some of the topology problems of large switch arrays.
Elastic constants and their pressure dependence of Zr41Ti14Cu12.5Ni9Be22.5C1 bulk metallic glass
Authors: Wang Wei-Hua , Wang R. J. , Li F. Y. , Zhao D. Q. , Pan M. X.
Published: July 2002

The acoustic velocities and their pressure dependence of bulk Zr41Ti14Cu12.5Ni9Be22.5C1 metallic glass (MG) have been measured up to 0.5 GPa by using a pulse echo overlap method. The elastic constants and thermodynamic parameters as well as their pressure dependence of the MG have been determined. The obtained elastic constants were compared to that of other kinds of glasses. More information about the microstructure, elastic properties, and glass forming ability of the MG was obtained.
Shallow p-type SiGeC layers synthesized by ion implantation of Ge, C, and B in Si
Authors: Kurata H. , Suzuki K. , Futatsugi T. , Yokoyama N.
Published: July 2002

We investigated the characteristics of p-type SiGeC layers for possible application to source/drain regions of sub-100 nm metal–oxide–semiconductor field-effect transistors. We synthesized the SiGeC layer by the high-dose ion implantation of Ge and C into Si substrate and subsequent annealing. We succeeded in fabricating shallow p+/n junctions by the incorporation of C, of which the peak concentration is more than 1%. B diffusion in this layer was significantly suppressed, and the depth profile of B was reproduced with a process simulation in which a diffusion coefficient much lower than the reported value was assumed. This should be attributed to decreased Si interstitials. We examined the sheet resistance and contact resistance of the SiGeC layer, and found that the increase in resistance is tolerable as compared with a SiGe layer. This is because the carrier deactivation by the incorporation of C was not serious, which was confirmed by the spreading resistance measurement. The junction leakage in the p+/n diode was reduced with the increase in the concentration of C. Hence, SiGeC is a promising material for use in shallow and low resistance p+/n junctions.
Observation of EL2 and additional deep levels at low temperature in an AlGaAs/GaAs multiple-quantum-well structure
Authors: Zhang Y. F. , Zhuo Q. , Zhang M. H. , Huang Q. , Zhou J. M.
Published: July 2002

Using a YAG:Nd laser as a pump source, the properties of electroabsorption in Stark geometry AlGaAs/GaAs multiple-quantum-well a photorefractive structure are studied at low temperature. When the temperature decreases from 160 to 120 K, the electroabsorption demonstrates the characteristics of both quenchable and unquenchable components. The quenchable component is interpreted as the photoquenching of EL2, and the unquenchable component is ascribed to the existence of additional deep levels. Modulated with an equivalent circuit, the concentrations of these defects are predicted on the order of 1.3×1016 and 2.2×1018 cm−3, and the capture cross section of additional deep levels is about 4.5×10−16 cm2. The investigation of optical transient current spectra verifies our deduction.
Electronic and isochronal annealing properties of electron traps in rapid thermally annealed SiO2-capped n-type GaAs epitaxial layers
Authors: Deenapanray P. N. K. , Tan H. H. , Jagadish C. , Auret F. D.
Published: July 2002

We have recently shown [P. N. K. Deenapanray et al., Appl. Phys. Lett. 77, 626 (2000)] that four electron traps S1(Ec−0.23 eV), S2(Ec−0.46 eV), S3(Ec−0.72 eV), and S4(Ec−0.74 eV) are introduced in rapid thermally-annealed (RTA) SiO2-capped n-type GaAs epitaxial layers. In the present study, we have used deep level transient spectroscopy to investigate the electronic and annealing properties of these deep levels. The electron emission kinetics of S1 is enhanced by an electric field, and the activation energy of S1 decreases linearly from ∼233 to ∼199 meV when the field is increased from 7.5×104 to 13.4×104 V cm−1. The intensities of S1, S2, and S4 show Arrhenius-like dependencies on the RTA temperature, which relate to the outdiffusion of Ga atoms into the SiO2 layer. The intensity of S2(VGa–SiGa) also increases exponentially with the square of the annealing time for RTA at 800 °C. Isochronal annealing experiments show that S1 and S2 are thermally stable below 500 and 400 °C, respectively. S4, which is a member of the EL2 family, is stable up to 600 °C. Secondary defects are introduced during isochronal annealing above 400 °C, and some of these defects are thermally stable at 600 °C.
Effects of In0.53Ga0.47As cap layer and stoichiometry of dielectric capping layers on impurity-free vacancy disordering of In0.53Ga0.47As/InP multiquantum well structures
Authors: Yu Jae Su , Lee Yong Tak , Lim H.
Published: July 2002

We have investigated the influence of the In0.53Ga0.47As cap layer and the stoichiometry of the SiOx and SiNx cap layers on the band gap energy increase, ΔEg, induced by the impurity-free vacancy disordering of In0.53Ga0.47As/InP multiquantum well structures. It is found that the magnitude of ΔEg decreases (increases) as the deposited SiOx (SiNx) layer becomes denser. It is also observed that the insertion of the In0.53Ga0.47As cap layer between the dielectric layer and InP barrier layer enhances (does not enhance) ΔEg appreciably in the SiOx (SiNx) capped system. A possible mechanism for these phenomena is discussed.
Influence of molecular hydrogen on Ge island nucleation on Si(001)
Authors: Dentel D. , Vescan L. , Chrétien O. , Holländer B.
Published: July 2002

The influence of molecular hydrogen (H2) on the structural and optical properties of self-assembled Ge dots grown on Si(001) has been studied using atomic force microscopy and photoluminescence spectroscopy (PL). Without hydrogen, a well known bimodal island size distribution occurs with small {105} faceted pyramids, and larger multifaceted domes. In the presence of an additional H2 flow, we observe that a higher density of smaller pyramids and a lower density of domes occurs. Moreover, in the presence of hydrogen, PL investigations have revealed a thicker wetting layer thickness, probably due to a reduction of the surface diffusion length.
Deep submicron microcontact printing on planar and curved substrates utilizing focused ion beam fabricated printheads
Authors: Longo D. M. , Benson W. E. , Chraska T. , Hull R.
Published: July 2002

Focused ion beam (FIB) fabrication of nanostructured “printheads” is used to extend applications of microcontact printing. Planar and curved printheads are fabricated with feature sizes less than 100 nm over fields of view of order 1 mm2, and transferred to target substrates with spatial resolution of order 200 nm. Analysis of the mechanical and ion optical stabilities of the FIB demonstrates that several hours of printhead fabrication time are possible with nanoscale precision. The rapid prototyping capability of this approach and the large depth of focus in the FIB enable rapid nanoscale patterning of a wide range of surface geometries.
Sensitive measurement of magnetostriction effects in thin films by means of a two-beam free-sample deflection method
Authors: Brückner W. , Lang C. , Schneider C. M.
Published: July 2002

We describe a setup for the measurement of thin-film magnetostriction λ which utilizes a sensitive laser-optical measurement of the substrate bending in magnetic fields up to 530 kA/m. The sensitivity reaches, e.g., for a 10 nm thick film on a 100 μm thick Si substrate, λ=5×10−8, which corresponds to a total substrate deflection on the order of 0.1 nm. The performance is tested with Co thin films of different thicknesses and annealing states.
Dynamic plasma pressure measurements
Authors: Kulish M. , Fertman A. , Golubev A. , Tauschwitz A. , Turtikov V.
Published: July 2002

An interferometric registration scheme for dynamic plasma pressure measurements has been developed and tested. The sensitive element of this scheme is an acoustic quartz rod. A description of the method is presented. The main features of the proposed scheme are the absence of a calibration procedure, the small size of the sensitive area, and the possibility of separating the studied object from the measuring setup. Experimental results for a capillary discharge plasma in a polyethylene slab with three different diameters of the channel, namely, 1.5, 2, and 3 mm are shown and illustrate the feasibility of the approach. Pressures in the range 30–600 bar were recorded.
A novel primary inductor for a dual tuned resonant transformer
Authors: Scholfield D. W. , Borovina J. L. , Copeland R. P.
Published: July 2002

A primary inductor for a dual tuned resonant transformer of some limited utility has been developed which merges the capacitance utilized for energy storage into the inductor, creating a composite electrical component. The resulting device, and the mathematical treatment to predict performance, are described.
Development of a two-dimensional birefringence distribution measurement system in laser-diode pumped solid-state laser material
Authors: Nishida Yoshio , Yamanaka Masanobu
Published: July 2002

We have developed a highly sensitive two-dimensional (2D) polarimeter that can sensitively measure the direction of the principal birefringence axis as well as the phase shift δ with its sign when δ<π/4. The principle of polarimeter, system hardware, processing software, and calculated power loss will be described. The power loss due to thermal birefringence was evaluated quantitatively using the Jones matrix method. This polarimeter was successfully used to measure the 2D birefringence distribution in the laser-diode (LD) pumped solid-state laser material. The 2D thermal- and mechanical-stress-induced birefringence distributions were measured using the proposed polarimeter and compared to a calculated one with good agreement in a LD-pumped rod. The measured relative phase shifts induced by thermal effects and the simulation obtained by a three-dimensional analysis code of thermal birefringence in a LD pumped solid-state laser slab also were quantitatively in good agreement. We found that the developed polarimeter will be useful for developing high power and high beam quality LD pumped solid-state lasers.
Diffusion-limited reaction in one dimension: Paired and unpaired nucleation
Authors: Habib Salman , Lindenberg Katja , Lythe Grant , Molina-Parı́s Carmen
Published: July 2002

We study the dynamics of diffusing particles in one space dimension with annihilation on collision and nucleation (creation of particles) with constant probability per unit time and length. The cases of nucleation of single particles and nucleation in pairs are considered. A new method of analysis permits exact calculation of the steady-state density and its time evolution in terms of the three parameters describing the microscopic dynamics: the nucleation rate, the initial separation of nucleated pairs, and the diffusivity of a particle. For paired nucleation at sufficiently small initial separation the nucleation rate is proportional to the square of the steady-state density. For unpaired nucleation, and for paired nucleation at sufficiently large initial separation, the nucleation rate is proportional to the cube of the steady-state density.
Freezing out a Fermi resonance: A temperature dependence study of the low-energy modes of CO on Pt(111)
Authors: Engström Ulrika , Ryberg Roger
Published: July 2002

We present an experimental study of the temperature dependence of the metal-molecule stretch vibrational mode of CO chemisorbed on a Pt(111) surface using infrared spectroscopy. The previously reported doublet structure in the vicinity of the Pt–CO stretch for bridge bonded C1612O, which we assigned to a Fermi resonance, exhibits a strong temperature dependence. The doublet vanishes at 50 K, reducing to one single peak with twice the intensity. This supports our previous interpretation and we are in this paper able to discuss this Fermi resonance in more detail. In addition, we have investigated how the Fourier transform infrared technique may influence the observed peak widths.
Application of scaled nucleation theory to metallic vapor condensation
Authors: Martı́nez Daniel M. , Ferguson Frank T. , Heist Richard H. , Nuth Joseph A.
Published: July 2002

In this paper we report that scaled nucleation theory (SNT) can describe moderately well the observed nucleation behavior of a significant number of refractory materials if a more appropriate value of a quantity commonly referred to as the excess surface entropy is used. With the availability of more reliable critical point and liquid property data, we are better able to calculate this quantity and we find that for refractory materials it can be as small as one half to one third the quantity traditionally used in its approximation. As a result of using more accurate values, we find considerably better agreement between SNT and experiment than what was originally determined. We also explain why using surface tension slope information to determine the excess surface entropy can lead to substantial errors in the SNT supersaturation prediction.
Comment on: “Energy band structures of the low-dimensional antiferromagnets Sr2CuO3 and Sr2CuO2Cl2” [J. Appl. Phys. 87, 4897 (2001)]
Authors: Rosner H. , Johannes D. M. , Drechsler S.-L.
Published: July 2002

Recent electronic structure calculations for the title compounds performed by Wu et al. [H. Wu et al., J. Appl. Phys. 87, 4897 (2000)] are critically reconsidered by applying highly accurate full-potential band structure methods. It is shown that due to a nonconverged basis set the band structure calculations presented here by the authors disagree considerably with those of Wu et al.