bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of teaching requirements for students on the activity of a university dental hospital
Authors: Collado V. , Faulks D. , Domejean S. , Roux D. , Woda A. , Mazille M. N. , Orliaguet T. , Hennequin M.
Published: October 2004

Objectives:  This study aimed at investigating the influence of teaching requirements on the clinical activity of a dental hospital.

Method:  The annual clinical activity of seven classes of fifth‐year students (n = 294) was monitored between 1994 and 2001 within the conservative dentistry and endodontic departments of a French dental hospital. The variables chosen were: (i) the mean number of procedures performed per student, and (ii) the proportion of different types of treatment within the global activity (i.e. endodontic treatment, anterior, and posterior restorations). These data were analysed in relation to changes in student assessment criteria over time.

Results:  Quantitative clinical teaching requirements were removed for the academic year 1998—99 and student clinical activity subsequently decreased by 32.7%, going from 51.9 ± 12.2 dental procedures on average per student in 1997—98, to 29.1 ± 7.2 in 2000—01. The mean number of patients treated per student also declined significantly during this period. The size of the minimum clinical requirement altered over the years prior to being removed altogether and a positive correlation existed between the volume of activity and the minimum requirement over this time. The types of treatment provided changed independently from the assessment criteria over the study period. There was a decrease in the percentage of amalgams placed and an increase in the number of posterior composites. A negative correlation existed between the evolution of these two types of treatment.

Conclusion:  This study demonstrates that the clinical activity of a department in a dental teaching hospital is directly related to the assessment criteria fixed by the university. This may have repercussions for hospital services.
British Society for Oral and Maxillofacial Pathology, UK: minimum curriculum in oral pathology
Authors: Odell E. W. , Farthing P. M. , High A. , Potts J. , Soames J. , Thakker N. , Toner M. , Williams H. K.
Published: October 2004

This paper describes a minimum curriculum in oral pathology for undergraduate dental education in the United Kingdom prepared by the Teachers Group of The British Society of Oral and Maxillofacial Pathology. Curricular development in UK dental schools is overseen by the General Dental Council (GDC), the Quality Assurance Agency for Higher Education (QAA) and the European Union. These organisations define the framework for education and learning outcomes but provide little or no detailed guidance on syllabus or curriculum. This recommended minimum curriculum has been drawn up by a consensus process involving teachers of oral pathology from all 13 UK and one Irish dental schools and is cross‐referenced to the GDC and QAA published requirements for undergraduate dental education.
Comparison of effects of acetylcholine on electromechanical characteristics in guinea‐pig atrium and ventricle
Authors: Zang W. J. , Chen L. N. , Yu X. J. , Fang P. , Lu J. , Sun Q.
Published: October 2004

The direct negative effects of acetylcholine (ACh) on guinea‐pig atria and ventricles were investigated using standard microelectrodes, a force transducer and a video edge‐detection system. It was found that: (1) ACh (at 0.001–100 μm) decreased the force of contraction and shortened the action potential duration (APD) in both atria and ventricles in a concentration‐dependent manner, and that the atria were more sensitive to ACh than the ventricles; and (2) the direct negative inotropic effect of ACh (1 μm) on an isolated cardiac cell was similar to that on the isolated myocardium. But this effect was not present in all isolated ventricular cells, while all the atrial cells responded to ACh. In conclusion, ACh had direct inhibitory effects on both atrial and ventricular tissue and myocytes, although the effects were greater in atria than in ventricles; and the negative inotropic effect of ACh was closely related to the shortening of the APD.
Ascending aortic stenosis selectively increases action potential‐induced Ca2+ influx in epicardial myocytes of the rat left ventricle
Authors: Volk Tilmann , Noble Penelope J. , Wagner Michael , Noble Denis , Ehmke Heimo
Published: October 2004

A decrease of the transient outward potassium current (Ito) has been observed in cardiac hypertrophy and contributes to the altered shape of the action potential (AP) of hypertrophied ventricular myocytes. Since the shape and duration of the ventricular AP are important determinants of the Ca2+ influx during the AP (QCa), we investigated the effect of ascending aortic stenosis (AS) on QCa in endo‐ and epicardial myocytes of the left ventricular free wall using the AP voltage‐clamp technique. In sham‐operated animals, QCa was significantly larger in endocardial compared to epicardial myocytes (803 ± 65 fC pF−1, n= 27 vs. 167 ± 32 fC pF−1, n= 38, P < 0.001). Ascending aortic stenosis significantly increased QCa in epicardial myocytes (368 ± 54 fC pF−1, n= 42, P < 0.05), but did not alter QCa in endocardial myocytes (696 ± 65 fC pF−1, n= 26). Peak and current–voltage relation of the AP‐induced Ca2+ current were unaffected by AS. However, the time course of the current–voltage relation was significantly prolonged in epicardial myocytes of AS animals. Model calculations revealed that the increase in QCa can be ascribed to a prolonged opening of the activation gate, whereas an increase in inactivation prevents an excessive increase in QCa. In conclusion, AS significantly increased AP‐induced Ca2+ influx in epicardial but not in endocardial myocytes of the rat left ventricle.
Neuronal activity‐related coupling in cortical arterioles: involvement of astrocyte‐derived factors
Authors: Lovick T. A. , Brown L. A. , Key B. J.
Published: October 2004

Neuronal activity‐evoked dilatation was investigated in cortical arterioles in brain slices from mature rats maintained in vitro at 31–33°C. In the presence of the thromboxane A2 agonist U46619 (75 nm) to preconstrict vessels, internal diameter decreased by 14.2% and rhythmic contractile activity (vasomotion) developed. Addition of the epoxygenase inhibitor miconazole (20 μm) produced a further decrease in diameter and increase in the frequency of  vasomotion, suggesting that tonic release of epoxygenase products maintains a level of cerebrovascular dilator tone. Addition of 1 μm AMPA for 5 min evoked a 15.4 ± 3.7% increase in diameter and the frequency of vasomotion decreased by −6.7 ± 1.4 contractions min−1. The response persisted in the presence of 1 μm TTX, indicating that it was independent of neuronal activity and thus likely to have been evoked by activation of AMPA receptors on astrocytes rather than neurones. The response to the brief (5 min) application of AMPA remained unchanged in the presence of miconazole (20 μm). Prolonged (30 min) application of AMPA produced a +12.1 ± 1.5% increase in internal diameter and reduction in vasomotion (−8.4 ± 1.7 contractions min−1) that were sustained throughout the stimulation period. However, when AMPA was applied in the presence of miconazole (20 μm) it evoked only a transient increase in diameter (+9.8 ± 3.1%) and decrease in vasomotion (−6.6 ± 1.5 contractions min−1) that lasted for less than 10 min despite continued application of AMPA. The results suggest that products of epoxygenase activity, probably epoxyeicosatrienoic acids (EETs) are involved in activity‐related dilatation in cortical arterioles. Whilst epoxygenase activity is not required to initiate dilatation, it appears to be involved in sustaining the response. Thus EETs released from membrane stores could contribute to the initial stages, but once these have been depleted de novo synthesis of EETs is required to maintain the effect.
Target system for fabrication and control of magnetic metal contentin diluted magnetic semiconductors by pulsed-laser deposition
Authors: Orii T. , Seto T. , Hirasawa M.
Published: October 2004

A synthesis method for control of magnetic metal content in diluted magnetic semiconductors prepared by pulsed laser deposition is presented. We developed a double target system composed of a disc-like semiconductor target and a wire metal target. This system has the advantage that the magnetic metal content is effectively controlled by changing the position of the lens focusing the laser beam. We synthesized Ni-doped ZnTe films using the target system and evaluated the Ni content and crystallinity of the films by electron probe micro analysis and x-ray diffraction.
Surface chemistry of the linear chromium chain complex on GaN(0001)
Authors: Lung Chien-Hua , Peng Shie-Ming , Chang Che-Chen
Published: October 2004

Better understanding about the chemistry of the organometallic chain complexes reacting on the solid surface can foster concepts of nanowire fabrication which are central to the continued advance of the electronic and optoelectronic industries. In this study, the adsorption and thermal reactivity of a trinuclear chromium chain complex, tetrakis (2,2′-dipyridylamino)chromium(VI) chloride, on the GaN(0001) surface were investigated using x-ray photoelectron spectroscopy, temperature-programmed desorption, and static secondary ion mass spectrometry in order to obtain some insight into the bonding changes involved in the reaction of the linear metal chain complex on the compound semiconductor surface. One of the two terminal Cr–Cl bonds of the complex may be cleaved upon adsorption at 110K, leading to the formation of the Ga–Cl bonds on the surface, although some complexes remained intact upon adsorption and bonded strongly to the surface. No ligand was dissociated from the chromium chain complex during the adsorption. The Cl-cleaved complex residue preserved its original chemical configuration. Both the Cl-cleaved and the intact complexes in the first layer were stable on the surface in the substrate temperature range between 110 and 260K. A partial decomposition in which some ligands were dissociated from the adsorbed complex took place before the substrate temperature reaching 400K. Additional Cr–Cl bonds were disrupted, resulting in a larger population of Ga–Cl bonds on the surface. Further thermal reaction at higher temperatures led to the dominance of the Ga–Cl bonding for the Cl presence on the surface. Surface etching of Ga by the dissociated Cl atoms started at a substrate temperature of ∼525K and the etching rate reached its maximum at ∼590K.
Analysis of adsorbed contaminants of CaF2 surfaces by infrared laser induced desorption
Authors: Fu JinMei , Surapaneni Yamini , Allen Susan D.
Published: October 2004

157 nm photolithography technologies are currently under development and have been accepted as the leading candidate for fabrication of the next generation semiconductor devices after 193nm. At this and shorter wavelengths, molecular contamination of surfaces becomes a serious problem as almost all molecules absorb at 157nm and below. The light transmitted by a photolithographic tool can be significantly decreased by the presence of a few monolayers adsorbed on its many optical surfaces. We have developed a laser induced desorption, electron impact ionization, time-of-flight mass spectrometer (LIDTOFMS) to study contaminants on 157nm and other ultraviolet optics, e.g., polished CaF2. The LID TOFMS of CaF2(100) samples showed water ions, hydrocarbon ions, oxygen-containing hydrocarbon ions, as well as alkali metal ions (Na+,K+). For multiple irradiations of one site at fixed laser fluence, the ion intensities decreased as the number of pulses increased, suggesting that surface contaminants were being removed. A degenerate threshold model that assumes preferential adsorption at surface defects was employed to quantitatively analyze the LID data. Desorption thresholds for water and hydrocarbons were obtained from this model.
Control of plasma parameters by using noble gas admixtures
Authors: Taylor Kurt J. , Yun Seokmin , Tynan George R.
Published: October 2004

Electron temperature and density in pure He, Ar, and Xe plasmas are estimated by zero-dimensional particle and power balance equations and measured by a Langmuir probe. Both of the modeling and experimental results show that the He (Xe) plasma has the highest (lowest) electron temperature and lowest (highest) electron density for a given fill pressure and source power. We find that the electron temperature is weakly dependent on the rf power, and thus the electron density can be controlled using the rf power. The electron temperature and density are also modeled and measured in mixtures of two noble gas species. We find that the electron temperature can be controlled by altering the composition of the noble gas mixture. Thus modulation of noble gas admixture ratios and rf power allows the electron density and temperature to be controlled independently. This independent control is shown to maintained with the addition of up to 20% partial pressure of oxygen, suggesting binary noble gas admixtures may provide additional control of dissociation kinetics.
Generation of low-energy neutral beam for Si etching
Authors: Kim S. J. , Wang S. J. , Lee J. K. , Lee D. H. , Yeom G. Y.
Published: October 2004

As the feature size shrinks toward the nanoscale, charge-up damage from ion-induced etching becomes a very serious problem. Neutral beam etching is one of the most popular techniques used to reduce charge-up damage. We have performed a neutral beam simulation to optimize the neutral beam, which is generated by collisions between ions produced by a plasma source with an ion gun and low angle reflectors. An ion gun is simulated using the two-dimensional Xgrafic object oriented particle-in-cell (XOOPIC) code to obtain a higher ion flux and to improve the directionality of ions. For neutral beam simulation, we use the modified XOOPIC code to which reflection data obtained by the transport of ions in matter (TRIM) code are appended. Neutral flux, energy and angle distributions, which have an influence upon the etch rate, are calculated in the neutral beam simulation. A low-energy neutral beam from an ion gun with two grids has a low neutral flux and a broad angle distribution. Therefore, we propose a three-grid ion gun that has one additional grid with positive voltage, allowing independent control of the ion flux and ion energy. By increasing the ion flux, the neutral flux by three grids is three times larger than that by two grids. The neutral beam source using a three-grid ion gun has several advantages for trench etching: increased etch rate, decreased sidewall etching, and reduced variation in the etch rate as the trench size changes. A low-energy neutral beam source using the three-grid ion g 0un and low-angle reflectors is experimentally tested.
Evaluation of Schottky barrier height of TiN∕p-type Si(100)
Authors: Pelleg Joshua , Douhin A.
Published: October 2004

Zero-bias Schottky barrier height (ϕBp) of reactive-sputtered TiN(∼40nm) on p-type Si(100) was determined at room temperature and the effect of heat treatment was investigated by forward current–voltage (I–V) measurements. The TiN remained amorphous following annealing. The zero-bias barrier heights for the as-deposited and annealed specimens were in the range of 0.53–0.64V. The lower ϕBp values of 0.53–0.54V are related to as-deposited and 673K annealed specimens, whereas the 0.62–0.64V values refer to samples annealed at 773–783K. Forward I–V measurements of as-deposited (300K) TiN∕Si diodes were performed in the temperature range of 220–285K. The barrier height was determined by the activation energy method, resulting in ϕBp=0.58V.
Infrared reflectance of GaN1−xPx ternary alloys grown by metalorganic chemical vapor deposition
Authors: Wang J. B. , Li Z. F. , Lu W. , Chen D. J. , Shen B. , Zheng Y. D.
Published: October 2004

Infrared (IR) reflection spectra of GaN1−xPx alloys, grown by light-radiation heating, low-pressure metalorganic chemical vapor deposition, have been investigated with phosphorus composition x=0–0.15. A multi-oscillator model has been used to fit the IR reflection spectra. In addition to the demonstration of a GaN-like transverse-optical (TO) mode, a GaP-like TO mode, located at about 355cm−1, has been identified for x>0, showing a typical two-mode behavior. With the increment of x the frequency of the GaN-like TO phonon decreases and the GaP-like TO phonon keeps its frequency almost unchanged within the measured composition range. A simple random-element-isodisplacement model has been employed to interpret the frequency change of both GaN-like and GaP-like phonons with the phosphorous composition x. The damping of the GaN-like TO mode increases significantly with x and is explained by the disorder effect resulting from the introduction of foreign P atoms.
Interpretation of stress variation in silicon nitride films deposited by electron cyclotron resonance plasma
Authors: Besland M. P. , Lapeyrade M. , Delmotte F. , Hollinger G.
Published: October 2004

We report here on internal stress variations in SiNx films deposited on silicon by plasma enhanced chemical vapor deposition-electron cyclotron resonance (PECVD-ECR) plasma. The effects of deposition parameters, film thickness and surface morphology have been considered. SiNx films can exhibit a compressive or a tensile internal stress, ranging from −1970 to +465MPa, depending on deposition parameters. Among published results, usual reported residual stress for PECVD films is compressive. Versatility of our experimental ECR equipment allows one to deposit films exhibiting a weak stress in the range of a few tens MPa. On the basis of atomic force microscopy observations, a correlation between the intensity of the stress and the granular morphology of the films has been observed. The rms value for SiNx film surfaces is never higher than 1.5nm, with a grain height ranging from 1.2 to 5nm and a grain width varying from 20 to 60nm. Both the grain size and the residual stress vary with the thickness of the films. This work highlights the influence of the initial surface properties on the deposition mechanism. An exhaustive review of the stress generation model is given and a tentative interpretation for the origin of stress, either compressive or tensile, is proposed.
Wide range flow sensor—Vacuum through viscous flow conditions
Authors: Sagi Hemi , Zhao Yabin , Wereley S. T.
Published: October 2004

An intelligent molecular flow sensor (IMFS) [see Note (1) on next page] enables direct gas flow measurements in the transitional and molecular flow regimes, as well as in the slip and continuum flow regimes, thereby enabling flow measurements at pressures ranging from vacuum through atmospheric. The properties of this sensor are investigated, along with the sensor’s transitional operating ranges. The IMFS operates as a mass flow sensor (directly measures the mass flow) in the transitional and molecular flow regimes, and it operates as a volumetric flow sensor in the continuum and slip flow regimes. Understanding of these properties and ranges of operation are critical for demanding leak testing, sealed closure integrity testing and vacuum test applications.
Effects of substrate bias and nitrogen flow ratio on the resistivity, density, stoichiometry, and crystal structure of reactively sputtered ZrNx thin films
Authors: Wang Shin-Hui , Chang Ching-Chun , Chen J. S.
Published: October 2004

Thin films of ZrNx were prepared by reactive rf magnetron sputtering from a Zr target in an Ar+N2 atmosphere, with different substrate biases (zero to −200V) and nitrogen flow ratios (0.5%–24%). The resistivity, density, stoichiometry, and crystal structure of ZrNx films were investigated. With 2% of nitrogen flow ratio, all ZrNx films exhibit the cubic ZrN crystal phase, regardless of the magnitude of substrate bias. The zero-biased ZrNx film contains substantial oxygen and shows high resistivity. Once a negative bias is applied to the substrate, the incorporated oxygen in ZrNx films can be reduced and the (111)ZrN preferred orientation is enhanced. Resistivity as low as 67μΩcm can be attained with −200V of substrate bias. At −200V of substrate bias, all films show the ZrN phase when the nitrogen flow ratio varies from 0.5% to 24%. However, the nitrogen content in ZrNx films increases continuously with the increasing nitrogen flow ratio. Resistivity of ZrNx films first decreases (0.5%–2%), and then increases with increasing nitrogen flow ratio (2%–24%). The best resistivity is obtained for the ZrNx film sputtered with 2% of nitrogen flow ratio and this sample exhibits the optimum grain size, (111)ZrN prefer orientation, density, and stoichiometry. The connection among the resistivity, density, stoichiometry, and crystal structure of ZrNx films and how they are influenced by the sputtering conditions (substrate bias, nitrogen flow ratio) are discussed.
Organosilane self-assembled monolayers directly linked to the diamond surfaces
Authors: Ohta Riichiro , Saito Nagahiro , Inoue Yasushi , Sugimura Hiroyuki , Takai Osamu
Published: October 2004

An amino-terminated self-assembled monolayer (SAM) was prepared from p-aminophenyltrimethoxysilane (H2N(CH)6Si(OCH3)3,APhS) on diamond substrates irradiated by vacuum ultraviolet (VUV) light (wavelength: 172nm) through chemical vapor deposition. Furthermore, the APhS-SAM was irradiated by VUV light in air. After the VUV irradiation, only one layer of siloxane (SiOx) was left as a result of the selective decomposition of organic compounds. APhS-SAM was reprepared on the SiOx surface. The evidence as to the respective processes was clearly obtained by x-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Based on the chemical bonding states analysis, APhS-SAMs were confirmed to be directly linked to the diamond substrates and SiOx layers with bonding types of Si–O–C and Si–O–Si, respectively. The compositions obtained by XPS measurement indicate that the thickness of the SiOx layer was increased gradually by repeating the APhS-SAM formations and VUV irradiations in this order. Finally, we are successful in controlling the nano-scale thickness of the SiOx layer, which is the interface between APhS-SAMs and diamond substrates.
Dielectric response of asymmetric KNbO3∕KTaO3 superlattices
Authors: Sigman J. , Bae H. J. , Norton D. P. , Budai J. , Boatner L. A.
Published: October 2004

The synthesis and properties of asymmetric KNbO3∕KTaO3 superlattices is examined. Interdigitated electrodes are fabricated for temperature-dependent capacitance measurements. The nonlinear dielectric response of 1∕N superlattice exhibits the anomalous positive tunability behavior indicative of antiferroelectricity. In contrast, the N∕1 KNbO3∕KTaO3 structures (N>1) appear to be either ferroelectric or paraelectric, depending on the temperature. Discussion of possible mechanisms for this behavior is given.
Neutral gas temperature measurements within transformer coupled toroidal argon plasmas
Authors: Bai Bo , Sawin Herbert
Published: October 2004

Spatially resolved neutral gas temperature of Ar plasmas within a new type of transformer-coupled toroidal plasma source was measured by fitting unresolved rovibrational bands of trace gas N2 (CΠu3→BΠg3). With power density as high as 4.8W∕cm3, the maximum neutral gas temperature inside Ar plasmas was found to be 2000K. The position with maximum neutral gas temperature was off the center of the cross section and close to the ferrite core, where higher electric field contributes to higher heating power. The dependence of neutral gas temperature on pressure was measured and can be empirically fitted by proportionality between gas temperature and logarithm of the pressure, as found by other researchers. A simple physical model gives the dependence of pressure as the sixth order of neutral gas temperature, which fits the experimental data as well. It was also found that added N2 gas perturbed Ar plasmas obviously, and therefore we recommend adding less than 1% N2 as trace gas. There is no dependence of fitted neutral gas temperature on the optical resolution of monochromator, as would be expected.
Twin formation in sputter-grown ZnO∕Al2O3(0001) epitaxial film: A real time x-ray scattering study
Authors: Kim I. W. , Kwon Y. B. , Yi J. M. , Je J. H. , Nouet G. , Wojtowicz T. , Ruterana P. , Kioseoglou J.
Published: October 2004

Twin formation and strain evolution in highly mismatched sputter-grown ZnO∕Al2O3(0001) hereroepitaxial films were investigated using real time synchrotron x-ray scattering measurements and high resolution electron microscopy (HREM). We reveal the existence of a critical thickness at which the twin of the 30° rotated domains starts to nucleate within the ZnO films, followed by gradual strain relaxation. Twin growth above the critical thickness stops as the strain almost fully relaxes. A HREM image shows that the twin nucleates 5–10nm away from the interface as isolated domains, not as types of layers.
Structural and optical characterization of beta barium borate thin films grown by electron beam evaporation
Authors: Maia L. J. Q. , Feitosa C. A. C. , De Vicente F. S. , Mastelaro V. R. , Li M. Siu , Hernandes A. C.
Published: October 2004

Thin films of beta barium borate (β-BBO) were deposited by electron beam physical vapor deposition on MgO(100) substrates. The deposition conditions were optimized so that the thin films would grow preferentially in a c-axis orientation. At a deposition temperature of 650°C, thin films grown on a MgO(100) substrate were found to be highly textured, with (00l) orientation (c-axis) normal to their surface. The addition of 4mol % of TiO2 to the BaO–B2O3 system stabilized the β-BBO crystalline phase without inducing significant variations in the optical properties of the thin films with respect to those of β-BBO bulk single crystal. The film crystallized in situ at 650°C exhibited a maximum effective second harmonic generation coefficient, deff, of 1.85pm∕V, which is comparable to the d22 coefficient of bulk β-BBO crystal.
Optical properties of tantalum nitride films fabricated using reactive unbalanced magnetron sputtering
Authors: Aouadi S. M. , Debessai M.
Published: October 2004

Coatings of tantalum nitride with various compositions were deposited on silicon substrates using unbalanced reactive magnetron sputtering. An optical emission spectrometer was used to monitor the ratio of tantalum to nitrogen particles in the plasma in real time. The coatings were characterized using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). The primary nitride phases (Ta, Ta2N, TaN) in the films were determined using XRD and XPS. The elemental composition was revealed from XPS measurements. The refractive indices were deduced from analysis of the SE data, which were subsequently simulated using the Drude–Lorentz model. The resistivity and electron mean free paths were deduced from this simulation and were correlated to the film composition and microstructure. The resistivity increased whereas the electron mean free path decreased with an increase in nitrogen content or a decrease in grain size.
Ion effects on CF2 surface interactions during C3F8 and C4F8 plasma processing of Si
Authors: Martin Ina T. , Fisher Ellen R.
Published: October 2004

Surface interactions of difluorocarbene (CF2) molecules were investigated using our LIF based imaging of radicals interacting with surfaces (IRIS) apparatus. LIF data of CF2 in C3F8 and C4F8 plasma molecular beams reveal that the relative densities of CF2 increase with increasing rf power and source pressure in both plasma systems. The surface reactivity of CF2 molecules during C3F8 and C4F8 plasma processing of room temperature Si substrates was also measured over a broad rf power range and at different pressures. A scatter coefficient (S) greater than one was measured for all unperturbed systems, indicating that CF2 molecules are produced at the substrate surface during film deposition. The same systems were also studied under ion-limited conditions, yielding S∼1, clear indication that ions are partially responsible for CF2 surface production. Plasma ions were identified using plasma-ion mass spectrometry. These data indicate that higher levels of CxFy+(x>1) are produced in the C4F8 plasmas. X-ray photoelectron spectroscopy analyses of treated substrates showed that amorphous fluorocarbon films were deposited during plasma processing of the substrates. A positive correlation was found between S(CF2) and film composition of FC materials deposited in both the IRIS apparatus and independent reactors.
Design and performance of a molecular beam epitaxy system for metallic heterostructure deposition illustrated by a study of the controlled epitaxy of Cu(111)∕Al2O3(0001)
Authors: Lund M. S. , Leighton C.
Published: October 2004

We describe the design and construction of an ultrahigh-vacuum molecular beam epitaxy (MBE) system for the growth of metallic heterostructures, particularly magnetic metals, and alloys. The system, which was specifically designed to be both cost-effective and compact, incorporates an “axial” design with a large source to substrate distance (>69cm) to meet demands for high uniformity, low deposition rate, and compatibility with nanolithographic masks and templates. The growth and in situ characterization capabilities are specifically tailored to metallic film growth allowing for greatly reduced costs in comparison to commercial MBE systems. We demonstrate the performance of the system via a study of the controlled epitaxy of Cu(111) on Al2O3(0001), a useful substrate/buffer layer combination for the growth of many magnetic transition metals and their alloys. Exploiting the three-dimensional nature of the growth at room temperature we are able to control the in-plane crystallite size, independent of the surface roughness, by varying the deposition rate.
Optical modeling of iridium thin film erosion under oxygen plasma exposure
Authors: Yan Li , Woollam John A.
Published: October 2004

This work is motivated by interest in use of iridium metal films in the space environment. Optical metrology is a sensitive tool for study of film roughness, optical constants, and microstructural properties. In the present paper, in situ spectroscopic ellipsometry is applied to monitor oxygen plasma etching of films of iridium∕chromium on fused silica substrates, using an electron cyclotron resonance plasma source. Optical modeling allows for a fundamental understanding of the plasma etching mechanism. Analysis of spectroscopic psi and delta data at selected time slices suggests the iridium film is etched away gradually upon plasma irradiation, while showing no signs of oxidation or other chemical changes. Nanoscale atomic mixing and index of refraction grading are observed.
Atomic layer deposition and characterization of hafnium oxide grown on silicon from tetrakis(diethylamino)hafnium and water vapor
Authors: Deshpande Anand , Inman Ronald , Jursich Gregory , Takoudis Christos
Published: October 2004

In this work thin films of hafnium oxide are deposited on Si(100) substrates by means of atomic layer deposition (ALD) using tetrakis(diethylamino)hafnium and water vapor at substrate temperatures of 250–350ºC. Our system capabilities include fast transient delivery of reactive fluids, real-time vapor phase detection (in situ tunable diode laser hygrometer), precursor thermochemical capabilities, and ppt level elemental analysis by inductive coupling plasma mass spectrometry. The composition, purity, and other properties of the films and resulting interfaces are determined using x-ray and Fourier transform infrared spectroscopies, Z-contrast imaging and electron energy loss spectroscopy in a scanning transmission electron microscope with Å scale resolution, and spectroscopic ellipsometry. The observed ALD rate is ∼1.4Å per cycle. The nonuniformity across the film is less than 4%. Negligible carbon contamination is found in the resulting stoichiometric films under all conditions studied. The pulse sequence was optimized to prevent disastrous particulate problems while still minimizing purge times. The film deposition is investigated as a function of substrate temperature and reagent pulsing characteristics. A mild inverse temperature dependence of the ALD rate is observed. The initial stage of the HfO2 growth is investigated in detail.
Temperature-dependent growth mechanisms of CaF2 on Si(111)
Authors: Wang C. R. , Müller B. H. , Bugiel E. , Hofmann K. R.
Published: October 2004

The molecular-beam epitaxy of CaF2 layers on Si(111) substrates was studied in the temperature range between 370 and 700°C. A strong temperature dependence of the CaF2 surface morphology was found. Layer-by-layer growth modes were found in two temperature ranges: (i) between 430 and 490°C, where growth of atomically flat CaF2 epilayers occurred, and (ii) at ∼700°C, where a step flow mode resulted in a relatively smooth CaF2 surface containing some rough regions, possibly due to the thermal decomposition of the interface layer. At ∼540°C, the triangular island shape observed at lower growth temperatures changed to a more hexagonal shape expected for thermodynamic equilibrium, but the top monolayer islands still exhibited a triangular shape, which can be attributed to a relatively higher lateral adatom impingement rate per unit length of island perimeter. The mechanisms of the complex temperature-dependent growth behavior are discussed in detail.
Sub-100°C a-Si:H thin-film transistors on plastic substrates with silicon nitride gate dielectrics
Authors: Sazonov A. , McArthur C.
Published: October 2004

Fabrication on thin-film transistors (TFTs) on flexible plastic substrates for large-area imagers and displays has been made possible by lowering the deposition temperatures, which reduces the thermal deformation of plastic substrates, greatly facilitating substrate preparation and device patterning. Furthermore, at extremely low deposition temperatures, much wider variety of low-cost substrates, plastics or otherwise, are available for use. In this article, we report on a-Si:H TFTs fabricated at 75°C on glass and plastic substrates. The TFTs were fabricated using inverted–staggered topology, in a full wet etch process. The TFT structures consisted of 140nm of sputtered Mo for gate, 380nm of plasma-enhanced chemical vapor deposition (PECVD) a-SiNx:H gate dielectric optimized for 75°C, 50nm of PECVD a-Si:H channel material, 50nm of PECVD n+ a-Si:H for source∕drain contacts, and sputtered Al for contact metallization. Current–voltage characteristics were measured, and relevant transistor parameters were calculated. TFTs exhibited the leakage current below 10−12A, and on∕off current ratio exceeding 105. The results were compared to those for high temperature a-Si:H TFTs, and the differences are discussed.
Contribution and origin of H3O+ in the mass spectral peak at 19amu
Authors: Cole C. R. , Outlaw R. A. , Champion R. L. , Baker D. H. , Holloway B. C.
Published: October 2004

Typically, the mass spectral peak observed at 19 amu in residual gas analyzers at very high vacuum (VHV) and ultrahigh vacuum (UHV) has been attributed to fluorine. Using Fourier transform mass spectrometry (FTMS), the presence of the hydronium ion H3O+ has been fully resolved from F+. Correlation of the mass 19 signals for a conventional quadrupole mass spectrometer (QMS) and the FTMS, positioned adjacent, unambiguously indicates hydronium as the source of mass 19. At partial pressures of H2O in the VHV range and higher there is sufficient density for the formation of the hydronium ion through ion–molecule interactions. Formation of the hydronium was found to directly correlate with the partial pressure of H2O. However, in a QMS, formation of H3O+ in UHV appears to occur principally by electron stimulated desorption (ESD). Dosing the system with hydrogen from 1L exposure to saturation (1×10−6Torr for 8h) was found to increase the H3O+ ESD yield detected by the QMS by as much as a factor of 10. The initial hydronium ESD cross section from a hydrogen saturated grid was estimated to be σ∼1×10−19cm2. In a separate experiment, time of flight–secondary ion mass spectrometry sputter yields from the stainless steel grid of a quadrupole mass spectrometer also showed small signals of H3O+, as well as its constituents, H+, O+ and OH+, but no F+.
Fabrication of dry etched and subsequently passivated laser facets in GaAs∕AlGaAs
Authors: Deichsel Eckard , Franz Gerhard
Published: October 2004

The aging behavior of edge emitting laser diodes based on GaAs∕AlGaAs is investigated by comparing devices with facets that are alternatively cleaved or dry etched and consecutively treated with H2S. In this work we demonstrate that an in situ exposure to H2S gas is not sufficient to prevent ageing but an additional plasma treatment is rather required to obtain comparable ageing results to lasers with cleaved facets.
Degradation of ZrN films at high temperature under controlled atmosphere
Authors: Lu Fu-Hsing , Lo Wen-Zheng
Published: October 2004

The degradation of ZrN films deposited onto Si substrates by unbalanced magnetron sputtering was investigated over temperatures of 300–1200°C in different atmospheres by analyzing changes in color and appearance, as well as microstructures. The atmospheres contained air, nitrogen, and forming gas (N2∕H2=9), which exhibited drastically different oxygen/nitrogen partial pressure ratios. The resultant degradation included mainly color changes and formation of blisters on the film surface. Color change was associated with the oxidation of the nitride film, which was analyzed by looking into the Gibbs free-energy changes at various temperatures and oxygen partial pressures. Two types of blisters occurred at different temperature ranges. Several large round blisters, denoted as A-type blisters, occurring at low temperatures originated from the large residual stress in the films. Many small irregular blisters, denoted as B-type blisters, appearing at relatively high temperatures resulted from the oxidation of the film.
In situ cleaning of GaN(0001) surfaces in a metalorganic vapor phase epitaxy environment
Authors: Reitmeier Z. J. , Park J.-S. , Mecouch W. J. , Davis R. F.
Published: October 2004

The presence of ammonia in a metalorganic vapor phase epitaxy (MOVPE) system configured for the growth of GaN films is necessary and sufficient to remove adsorbed O- and C-containing species from the (0001) surface of this compound without measurable decomposition of this surface. Chemical and microstructural evidence in support of this statement has been obtained from investigations concerned with the extension of a previously developed in situ process route for cleaning heated GaN(0001) surfaces in a molecular beam epitaxy environment using flowing ammonia to the higher pressure regime of MOVPE. Thin films of GaN were deposited under 20Torr total pressure on GaN templates, previously exposed to the laboratory ambient, and heated in either a nitrogen∕hydrogen or an ammonia∕hydrogen mixture to the deposition temperature of 1020°C. Secondary ion mass spectroscopy of these samples revealed significant concentrations of carbon and oxygen at the GaN∕GaN interface in the former and the absence of these contaminants above the detection limits of the instrument in the latter. The surfaces of the templates heated in the nitrogen∕hydrogen atmosphere also decomposed sufficiently to form a very thin liquid Ga layer that reacted with ammonia to form a GaN-containing film either at the outset of film growth or on cooling in an ammonia∕nitrogen atmosphere. Atomic force microscopy (AFM) showed a smoother surface for the GaN films deposited on templates heated and cleaned in the ammonia∕hydrogen mixture relative to films deposited on templates heated in the nitrogen∕hydrogen mixture. The latter surface contained both a higher density of step terminations, indicative of a higher density of threading dislocations having screw and mixed character, and pits.
Ion-bombardment induced light emission from Si(100) surfaces under continuous silane exposures
Authors: Rajasekar P. , Kadossov Evgueni B. , Materer Nicholas F.
Published: October 2004

The intensities of the optical spectral lines emitted from a Si(100) surface under Ar+ ion bombardment are studied as a function of the ion kinetic energy (1–5keV) and the partial pressure of silane. In these experiments, the ion flux is held constant while either the bombardment energy or the partial pressure of silane is varied. The intensities of the spectral lines are normalized with respect to the intensity of the excited neutral silicon (SiI,288nm) optical line emitted from the clean Si surface. The intensities of excited neutral Si (SiI,288nm), molecular SiH (A2Δ–X2Π,414nm), H Balmer beta (486nm) and H Balmer gamma (434nm) optical lines emitted from silane exposed Si surfaces follow a similar increasing trend with respect to increasing partial pressures of silane. During continuous silane exposures, the intensity of these four lines also increases with increasing ion kinetic energy. A qualitative explanation based on the adsorption and decomposition of silane on the Si surfaces can account for this behavior. In contrast to the monotonic increase of the above emission lines with greater incident kinetic energies and higher silane partial pressures, the normalized H Balmer alpha (656nm) optical line exhibits unique behavior. The intensity of the Balmer alpha transition decreases with increasing incident ion kinetic energy at all measured partial pressures of silane.
Aiming towards “moral equilibrium”: health care professionals’ views on working within the morally contested field of antenatal screening
Authors: Farsides B , Williams C , Alderson P
Published: October 2004

Objective:To explore the ways in which health care practitioners working within the morally contested area of prenatal screening balance their professional and private moral values.

Design:Qualitative study incorporating semistructured interviews with health practitioners followed by multidisciplinary discussion groups led by a health care ethicist.

Setting:Inner city teaching hospital and district general hospital situated in South East England.

Participants:Seventy practitioners whose work relates directly or indirectly to perinatal care.

Results:Practitioners managed the interface between their professional and private moral values in a variety of ways. Two key categories emerged: “tolerators”, and “facilitators”. The majority of practitioners fell into the “facilitator” category. Many “facilitators” felt comfortable with the prevailing ethos within their unit, and appeared unlikely to feel challenged unless the ethos was radically challenged. For others, the separation of personal and professional moral values was a daily struggle. In the “tolerator” group, some practitioners sought to influence the service offered directly, whereas others placed limits on how they themselves would contribute to practices they considered immoral.

Conclusions:The “official” commitment to non-directiveness does not encourage open debate between professionals working in morally contested fields. It is important that practical means can be found to support practitioners and encourage debate. Otherwise, it is argued, these fields may come to be staffed by people with homogeneous moral views. This lack of diversity could lead to a lack of critical analysis and debate among staff about the ethos and standards of care within their unit.
The right not to know: an autonomy based approach
Authors: Andorno R
Published: October 2004

The emerging international biomedical law tends to recognise the right not to know one’s genetic status. However, the basis and conditions for the exercise of this right remain unclear in domestic laws. In addition to this, such a right has been criticised at the theoretical level as being in contradiction with patient’s autonomy, with doctors’ duty to inform patients, and with solidarity with family members. This happens especially when non-disclosure poses a risk of serious harm to the patient’s relatives who, without that vital information, could be deprived of preventive or therapeutic measures. This paper argues, firstly, that individuals may have a legitimate interest in not knowing their genetic make up to avoid serious psychological consequences; secondly, that this interest, far from being contrary to autonomy, may constitute an enhancement of autonomy; thirdly, that the right not to know cannot be presumed, but must be “activated” by the individual’s explicit choice, and fourthly, that this is not an absolute right, in the sense that it may be restricted when disclosure to the patient is necessary in order to avoid a risk of serious harm to third persons.
Returning to the Alder Hey report and its reporting: addressing confusions and improving inquiries
Authors: Dewar S , Boddington P
Published: October 2004

The Royal Liverpool Children’s Inquiry investigated the circumstances leading to the removal, retention, and disposal of human tissue, including children’s organs, at the Royal Liverpool Children’s NHS Trust (the Alder Hey Hospital). It recommended changes to procedures for obtaining consent for postmortems and retaining organs and tissues for research or education. However, the report contains five areas of confusion. Firstly, it allowed the cultural and historical traditions of horror over the use and misuse of body parts to suffuse the logical analysis of past wrongs and future rights. Secondly, it makes an inappropriate conflation between seeking redress for past wrongs and shaping future policy. Thirdly, the report takes a muddled stance over the value of bodily integrity at burial. Fourthly, the report is inconsistent over the justification for future organ and tissue collections. Fifthly, the notion of “respect” is used with troublesome looseness. The extent to which subsequent policy work has furthered the search for greater ethical clarity over these difficult issues is discussed, together with reflection on three particular improvements that could be made to the process of such an inquiry.
The unfeasibility of requests for euthanasia in advance directives
Authors: van Delden J J M
Published: October 2004

In April 2002 a new law regarding euthanasia came into effect in the Netherlands. This law holds that euthanasia remains a criminal offence unless it is (1) performed by a physician who (2) acts according to six specified rules of due care and (3) reports the case to a review committee. The six rules of due care are similar to those of the previous regulation and are largely based on jurisprudence. Completely new, however, is the article concerning a competent patient who has written an advance directive requesting euthanasia under certain circumstances. The law stipulates that a physician may act according to that written request, as long as he or she fulfils all other rules of due care. The author defends the view that these requests are neither feasible nor ethically justifiable, and presents both moral and practical arguments for this, claiming that for consistency reasons one cannot act on the basis of a written statement and fulfil the other rules of due care at the same time. The author also examines a difficult case of a demented, severely depressed woman who had written a living will requesting euthanasia before she became demented.
Involvement of nurses in euthanasia: a review of the literature
Authors: De Beer T , Gastmans C , Dierckx de Casterlé B
Published: October 2004

In ethical debates about euthanasia, the focus is often exclusively on the involvement of physicians and the involvement of nurses is seldom given much attention. Yet nurses occupy a central position in the care of terminal patients, where being confronted with a euthanasia request is an ever present possibility. To assess the involvement of nurses in euthanasia, this article provides an overview of relevant findings from the scientific literature. From this it becomes apparent that nurses are involved in various phases of the euthanasia process: observing the request for euthanasia, decision making, carrying out of euthanasia, and the aftercare for the patient’s family members.