bluuebunny/crossref_metadata_2025 huggingface dataset:
Note on Sources of Sampling Variability in Science Performance Assessments
Authors: Shavelson Richard J. , Ruiz‐Primo Maria Araceli , Wiley Edward W.
Published: September 2005

In 1993, we reported in Journal of Educational Measurement that task‐sampling variability was the Achilles’ heel of science performance assessment. To reduce measurement error, tasks needed to be stratified before sampling, sampled in large number, or possibly both. However, Cronbach, Linn, Brennan, & Haertel (1997) pointed out that a task‐sampling interpretation of a large person x task variance component might be incorrect. Task and occasion sampling are confounded because tasks are typically given on only a single occasion. The person x task source of measurement error is then confounded with the pt x occasion source. If pto variability accounts for a substantial part of the commonly observed pt interaction, stratifying tasks into homogenous subsets—a cost‐effective way of addressing task sampling variability—might not increase accuracy. Stratification would not address the pro source of error. Another conclusion reported in JEM was that only direct observation (DO) and notebook (NB) methods of collecting performance assessment data were exchangeable; computer simulation, short‐answer, and multiple‐choice methods were not. However, if Cronbach et al. were right, our exchangeability conclusion might be incorrect. After re‐examining and re‐analyzing data, we found support for Conbach et al. We concluded that large task‐sampling variability was due to both the person x task interaction and person x task x occasion interaction. Moreover, we found that direct observation, notebook and computer simulation methods were equally exchangeable, but their exchangeability was limited by the volatility of student performances across tasks and occasions.
Measurement Error, Multidimensionality, and Scale Shrinkage: A Reply to Yen and Burket
Authors: Camilli Gregory
Published: September 2005

Yen and Burket (1997) provided a critical analysis of the work by Camilli (1988) regarding scale shrinkage, and suggested that shrinkage in vertical equating cannot be understood apart front multidimensionality. In this response, select research on reliability, multidimensionality and scale shrinkage are reviewed. These perspectives are then integrated with issues of practical importance to educators.
Can Examinees Use a Review Option to Obtain Positively Biased Ability Estimates on a Computerized Adaptive Test?
Authors: Vispoel Walter P. , Rocklin Thomas R. , Wang Tianyou , Bleiler Timothy
Published: September 2005

Part of the controversy about allowing examinees to review and change answers to previous items on computerized adaptive tests (CATs) centers on a strategy for obtaining positively biased ability estimates attributed to Wainer (1993) in which examinees intentionally answer items incorrectly before review and to the best of their abilities upon review. Our results, based on both simulated and live testing data, showed that there were instances in which the Wainer strategy yielded inflated ability estimates as well as instances in which it yielded deflated ability estimates. The success of the strategy in inflating ability estimates depended on the ability estimation method used (maximum likelihood versus Bayesian), the examinee's true ability level, the standard error of the ability estimate, the examinee's ability to implement the strategy, and the type of decision made from the ability estimate. We discuss approaches to dealing with the Wainer strategy in operational CAT settings.
Psychometric and Cognitive Functioning of an Under‐Determined Computer‐Based Response Type for Quantitative Reasoning
Authors: Bennett Randy Elliot , Morley Mary , Quardt Dennis , Rock Donald A. , Singley Mark K. , Katz Irvin R. , Nhouyvanisvong Adisack
Published: September 2005

We evaluated a computer‐delivered response type for measuring quantitative skill. “Generating Examples” (GE) presents under‐determined problems that can have many right answers. We administered two GE tests that differed in the manipulation of specific item features hypothesized to affect difficulty. Analyses related to internal consistency reliability, external relations, and features contributing to item difficulty, adverse impact, and examinee perceptions. Results showed that GE scores were reasonably reliable but only moderately related to the GRE quantitative section, suggesting the two tests might be tapping somewhat different skills. Item features that increased difficulty included asking examinees to supply more than one correct answer and to identify whether an item was solvable. Gender differences were similar to those found on the GRE quantitative and analytical test sections. Finally, examinees were divided on whether GE items were a fairer indicator of ability than multiple‐choice items, but still overwhelmingly preferred to take the more conventional questions.
A Cautionary Note on IRT‐Based Linking of Tests With Polytomous Items
Authors: Tate Richard L.
Published: September 2005

Published discussions of the year‐to‐year linking of tests comprised of polytomous items appear to suggest that the linking logic traditionally used for multiple‐choice items is also appropriate for polytomous items. It is argued and illustrated that a modification of the traditional linking is necessary when tests consist of constructed‐response items judged by raters and there is a possibility of year‐to‐year variation in the rating discrimination and severity.
Possible Determinants of Differential Item Functioning: Familiarity, Interest, and Emotional Reaction
Authors: Stricker Lawrence J. , Emmerich Walter
Published: September 2005

This study evaluated the connection between gender differences in examinees’ familiarity, interest, and negative emotional reactions to items on the Advanced Placement Psychology Examination and the items’ gender differential item functioning (DIF). Gender DIF and gender differences in interest varied appreciably with the content of the items. Gender differences in the three variables were substantially related to the items’ gender DIF (e.g., R = .50). Much of the gender DIF on this test may be attributable to gender differences in these variables.
Estimators of Conditional Scale‐Score Standard Errors of Measurement: A Simulation Study
Authors: Lee Won‐Chan , Brennan Robert L. , Kolen Michael J.
Published: September 2005

This paper describes four procedures previously developed for estimating conditional standard errors of measurement for scale scores: the IRT procedure (Kolen, Zeng, & Hanson. 1996), the binomial procedure (Brennan & Lee, 1999), the compound binomial procedure (Brennan & Lee, 1999), and the Feldt‐Qualls procedure (1998). These four procedures are based on different underlying assumptions. The IRT procedure is based on the unidimensional IRT model assumptions. The binomial and compound binomial procedures employ, as the distribution of errors, the binomial model and compound binomial model, respectively. By contrast, the Feldt‐Qualls procedure does not depend on a particular psychometric model, and it simply translates any estimated conditional raw‐score SEM to a conditional scale‐score SEM. These procedures are compared in a simulation study, which involves two‐dimensional data sets. The presence of two category dimensions reflects a violation of the IRT unidimensionality assumption. The relative accuracy of these procedures for estimating conditional scale‐score standard errors of measurement is evaluated under various circumstances. The effects of three different types of transformations of raw scores are investigated including developmental standard scores, grade equivalents, and percentile ranks. All the procedures discussed appear viable. A general recommendation is made that test users select a procedure based on various factors such as the type of scale score of concern, characteristics of the test, assumptions involved in the estimation procedure, and feasibility and practicability of the estimation procedure.
Monte Carlo Based Null Distribution for an Alternative Goodness‐of‐Fit Test Statistic in IRT Models
Authors: Stone Clement A.
Published: September 2005

Assessing the correspondence between model predictions and observed data is a recommended procedure for justifying the application of an IRT model. However, with shorter tests, current goodness‐of‐fit procedures that assume precise point estimates of ability, are inappropriate. The present paper describes a goodness‐of‐fit statistic that considers the imprecision with which ability is estimated and involves constructing item fit tables based on each examinee's posterior distribution of ability, given the likelihood of their response pattern and an assumed marginal ability distribution. However, the posterior expectations that are computed are dependent and the distribution of the goodness‐of‐fit statistic is unknown. The present paper also describes a Monte Carlo resampling procedure that can be used to assess the significance of the fit statistic and compares this method with a previously used method. The results indicate that the method described herein is an effective and reasonably simple procedure for assessing the validity of applying IRT models when ability estimates are imprecise.
The Point‐Biserial as a Discrimination Index for Distractors in Multiple‐Choice Items: Deficiencies in Usage and an Alternative
Authors: Attali Yigal , Fraenkel Tamar
Published: September 2005

We show that using the point‐biserial as a discrimination index for distractors by differentiating between examinees who chose the distractor and examinees who did not choose the distractor is theoretically wrong and may lead to an incorrect rejection of items. We propose an alternative usage and present empirical evidence for its suitability.
The Stability of Rater Severity in Large‐Scale Assessment Programs
Authors: Congdon Peter J. , MeQueen Joy
Published: September 2005

The purpose of this study was to investigate the stability of rater severity over an extended rating period. Multifaceted Rasch analysis was applied to ratings of 16 raters on writing performances of 8, 285 elementary school students. Each performance was rated by two trained raters over a period of seven rating days. Performances rated on the first day were re‐rated at the end of the rating period. Statistically significant differences between raters were found within each day and in all days combined. Daily estimates of the relative severity of individual raters were found to differ significantly from single, on‐average estimates for the whole rating period. For 10 raters, severity estimates on the last day were significantly different from estimates on the first day. These fndings cast doubt on the practice of using a single calibration of rater severity as the basis for adjustment of person measures.
Obtaining Test Blueprint Weights From Job Analysis Surveys
Authors: Spray Judith A. , Huang Chi‐Yu
Published: September 2005

A method for combining multiple scale responses from job or task surveys based on a hierarchical ranking scheme is presented. A rationale for placing the resulting ordinal information onto an interval scale of measurement using the Rasch Rating Scale Model is also provided. After a simple linear transformation, the item or task parameter estimates can be used to obtain item weights to be used in constructing test blueprints. Prior weights can then be used to modify the item weights after data collection, based either on content balancing requirements or Bayesian prior content weights from SMEs (subject matter experts). Finally a method is suggested to link two or more surveys, again using the Rasch Rating Scale Model and the computer program, Bigsteps, when it is desirable to shorten the length of the typical job or task survey.
The Scaling of Mixed‐Item‐Format Tests With the One‐Parameter and Two‐Parameter Partial Credit Models
Authors: Sykes Robert C. , Yen Wendy M.
Published: September 2005

Item response theory scalings were conducted for six tests with mixed item formats. These tests differed in their proportions of constructed response (c.r.) and multiple choice (m.c.) items and in overall difficulty. The scalings included those based on scores for the c.r. items that had maintained the number of levels as the item rubrics, either produced from single ratings or multiple ratings that were averaged and rounded to the nearest integer, as well as scalings for a single form of c.r. items obtained by summing multiple ratings. A one‐parameter (IPPC) or two‐parameter (2PPC) partial credit model was used for the c.r. items and the one‐parameter logistic (IPL) or three‐parameter logistic (3PL) model for the m.c. items, ltem fit was substantially worse with the combination IPL/IPPC model than the 3PL/2PPC model due to the former's restrictive assumptions that there would be no guessing on the m.c. items and equal item discrimination across items and item types. The presence of varying item discriminations resulted in the IPL/IPPC model producing estimates of item information that could be spuriously inflated for c.r. items that had three or more score levels. Information for some items with summed ratings were usually overestimated by 300% or more for the IPL/IPPC model. These inflated information values resulted in under‐estbnated standard errors of ability estimates. The constraints posed by the restricted model suggests limitations on the testing contexts in which the IPL/IPPC model can be accurately applied.
A SIBTEST Approach to Testing DIF Hypotheses Using Experimentally Designed Test Items
Authors: Bolt Daniel M.
Published: September 2005

This paper considers a modification of the DIF procedure SIBTEST for investigating the causes of differential item functioning (DIF). One way in which factors believed to be responsible for DIF can be investigated is by systematically manipulating them across multiple versions of an item using a randomized DIF study (Schmitt, Holland, & Dorans, 1993). In this paper: it is shown that the additivity of the index used for testing DIF in SIBTEST motivates a new extension of the method for statistically testing the effects of DIF factors. Because an important consideration is whether or not a studied DIF factor is consistent in its effects across items, a methodology for testing item x factor interactions is also presented. Using data from the mathematical sections of the Scholastic Assessment Test (SAT), the effects of two potential DIF factors—item format (multiple‐choice versus open‐ended) and problem type (abstract versus concrete)—are investigated for gender Results suggest a small but statistically significant and consistent effect of item format (favoring males for multiple‐choice items) across items, and a larger but less consistent effect due to problem type.
Piece-Wise Linear Dynamic Systems With One-Way Clutches
Authors: Mockensturm Eric M. , Balaji Raghavan
Published: September 2005

One-way clutches and clutch bearings are being used in a wide variety of dynamic systems. Motivated by their recent use as ratchets in piezoelectric actuators and decoupling devices in serpentine belt drives, a method of analysis of systems containing one-way clutches is presented. Two simple systems are analyzed. The goal of the first is the power transmission which would be of concern in an actuator. The goal of the second is decoupling large inertia elements to reduce loads in an oscillating system, the objective of the clutch in a serpentine belt drive. Results show how system parameters can be tuned to meet the desired performance of these piece-wise linear systems.
A Technique for Estimating Linear Parameters Using Nonlinear Restoring Force Extraction in the Absence of an Input Measurement
Authors: Haroon Muhammad , Adams Douglas E. , Luk Yiu Wah
Published: September 2005

Conventional nonlinear system identification procedures estimate the system parameters in two stages. First, the nominally linear system parameters are estimated by exciting the system at an amplitude (usually low) where the behavior is nominally linear. Second, the nominally linear parameters are used to estimate the nonlinear parameters of the system at other arbitrary amplitudes. This approach is not suitable for many mechanical systems, which are not nominally linear over a broad frequency range for any operating amplitude. A method for nonlinear system identification, in the absence of an input measurement, is presented that uses information about the nonlinear elements of the system to estimate the underlying linear parameters. Restoring force, boundary perturbation, and direct parameter estimation techniques are combined to develop this approach. The approach is applied to experimental tire-vehicle suspension system data.
Characterization of Modal Damping of Sandwich Plates
Authors: Hammami Lotfi , Zghal Bacem , Fakhfakh Tahar , Haddar Mohamed
Published: September 2005

The homogenization of the energy functional of a sandwich plate, its minimization and its discretization by finite element methods and modeling the viscoelastic core behavior by an hysteretic structural damping lead to the homogenized dynamic equation of a sandwich plate. The vibratory analysis permits the determination of the elastic eigenmodes and the characterization of the modal damping which will serve to the establishment of dynamical responses if we used the modal dynamic recombination method. The numerical results obtained show that the eigenmodes are not orthogonal to the damping matrix but are only weakly coupled. Besides, the modal damping matrix coefficients vary according to the ratio of the core thickness and the total thickness of sandwich plate and follow a second-order polynomial function of this ratio.
Simulating and Measuring Structural Intensity Fields in Plates Induced by Spatially and Temporally Random Excitation
Authors: Daley Michael J. , Hambric Stephen A.
Published: September 2005

The structure-borne power in bending waves is well understood, and has been studied by many investigators in ideal beam and plate structures. All studies to date, however, have considered only the structural intensity induced by deterministic, localized drives. Since many structures of practical interest are excited by spatially random pressure fields, such as diffuse and turbulent boundary layer pressure fluctuations, techniques for measuring and predicting the structural intensity patterns in flat plates excited by such fields are presented here. The structural intensity at various frequencies in a simply supported, baffled, flat plate driven by a diffuse pressure field is simulated using analytical techniques and measured by post-processing data from a scanning laser Doppler vibrometer and reference accelerometer using finite differencing techniques. The measured and simulated fields are similar, and show intensity patterns different from those caused by deterministic point drives. Specifically, no clear source regions are apparent in the randomly driven intensity fields, although the energy flow patterns do clearly converge toward a point damper attached to the plate.
Active Stiffeners for Vibration Control of a Circular Plate Structure: Analytical and Experimental Investigations
Authors: Philen Michael K. , Wang K. W.
Published: September 2005

Space-based adaptive optic systems have gained considerable attention within the past couple of decades. Achieving the increasingly stringent performance requirements for these systems is greatly hindered by strict weight restrictions, size limitations, and subjected hostile environments. There has been considerable attention in developing lightweight adaptive optics where piezoelectric sheet actuators are attached on the back of optical mirrors to achieve a high precision surface shape with minimum additional weight. Vibration control of such large flexible space structures is continually challenging to engineers due to the large number of actuators and sensors and the large number of vibration modes within the operational bandwidth. For these structures, any disturbed modes are likely to remain vibrating for an extended period of time due to the small amount of damping available. As a result, controller spillover should be minimized as much as possible to avoid exciting the residual modes. In recent investigations of circular plate shape control by [Philen and Wang, Int. Soc. Opt. Eng. 4327, pp. 709–719]. It was demonstrated that directional decoupling of the two-dimensional actuator (meaning that the actuation in one of the two directions is eliminated) improves the system performance when correcting for the lower order Zernike static deformations. This directional decoupling effect can be achieved through an active stiffener (AS) design. In this research, analytical and experimental efforts are carried out to examine the effect of the active stiffener actuators in reducing the controller spillover through the stiffeners’ decoupling characteristics. It is shown that significant reductions in controller spillover can be achieved in systems using the active stiffener actuators when compared to systems having direct attached (DA) actuators, thus resulting in improved vibration control performance. The experimental results verify the analytical predictions and clearly demonstrate the merit of the active stiffener concept.
Structural and mechanical properties of dendrimer-mediated thin films
Authors: Xu Fengting T. , Thaler Sean M. , Barnard John A.
Published: September 2005

Dendrimers are three-dimensional, globular, highly branched macromolecules made up of a central core surrounded by repetitive units all enclosed by a terminal group shell. They can be synthesized with highly controllable sizes (they are monodisperse) determined by the core type, extent of branching, and nature of the end groups, in the range from a few to several tens of nm in diameter. Dendrimers also assemble into monolayers on technologically interesting substrates using simple cleaning, dipping, and rinsing procedures. In this condensed monolayer phase dendrimers can act as surfactants mediating the growth of ultraflat films, and create novel nanomechanical, adhesive, frictional, and tribological behavior. We have recently reported on the dramatically enhanced quality (superior flatness and adhesion) of metal films deposited on dendrimer monolayers. Different tribological responses are also observed in dendrimer-mediated metal thin films. To better understand metal/dendrimer/substrate interactions and how they determine the distinct physical, mechanical, and chemical properties of the resulting dendrimer-based nanocomposites, we are examining the structure and nanomechanical response of metal films formed with and without dendrimer mediation by atomic force, lateral force, and force modulation microscopy.
Low-temperature studies of magnetic phases of the interfacial layers for Co∕Ge(100) and Co∕Ge(111) films
Authors: Tsay J. S. , Su C. W. , Hwang C. H. , Yao Y. D.
Published: September 2005

Magnetic phases of the interfacial layers were comparatively investigated for Co∕Ge(100) and Co∕Ge(111) films thinner than 13 ML using surface magneto-optic Kerr effect technique. Co∕Ge(100) films are nonferromagnetic up to 12 ML as deposited and measured at 300K. A transition from nonferromagnetism to ferromagnetism occurs upon cryogenic treatments. Systematic investigations of the magnetic properties for Co∕Ge(100) reveal a magnetic phase diagram. The boundary between nonferromagnetic and ferromagnetic phases was experimentally determined to be from below 150K to above 300K as the cobalt thickness increases from 9 to 13 ML. This behavior is consistent with the thickness-dependent scaling law of the Curie temperature for a thin film system. Because of the difference of the densities of surface atoms, the different thickness of the formed interfacial compounds could explain the shift of the phase boundary to higher Co thickness side as compared to the Co∕Ge(111) system. In addition, the critical exponent β in the power law relationship of magnetization for Co∕Ge(100) films lies close to the value expected by the three-dimensional Heisenberg model, while the critical exponent of Co∕Ge(111) is close to the value of the two-dimensional XY model. The different behaviors of the magnetic transition are attributed to the different interfacial structures.
Microfabrication and nanomechanical characterization of polymer microelectromechanical system for biological applications
Authors: Wei Guohua , Bhushan Bharat , Ferrell Nicholas , Hansford Derek
Published: September 2005

Polymer microelectromechanical system (MEMS) devices are promising for biological applications such as development of biosensors and biomechanical devices. In order to develop polymer biological MEMS (BioMEMS), polymer microfabrication techniques are required, and the nanomechanics studies, including measurement of the nanomechanical properties of the polymer materials, must be carried out. This article presents the development of soft lithography based polymer BioMEMS microfabrication techniques and systematic studies on the nanomechanical characterization of the polymer thin films and beams. Poly (methylmethacrylate) (PMMA) and poly (propyl methacrylate) (PPMA) are used to make the polymer beams for MEMS integration. The hardness, elastic modulus and creep behavior of PMMA and PPMA thin films and microstructures were measured using continuous stiffness measurement nanoindentation technique, and the scratch resistance of the polymer thin films was measured using a nanoscratch technique. The elastic moduli of the polymer beams were also obtained from bending tests performed by nanoindentation. To simulate the working environment of the polymer BioMEMS, the beams were also soaked in de-ionized water or heated up to human body temperature, and the nanomechanical properties were measured.
Assembly of hydrothermally synthesized tin oxide nanocrystals
Authors: Shirahata Naoto , Hozumi Atsushi , Asakura Shuuichi , Fuwa Akio , Sakka Yoshio
Published: September 2005

We have successfully assembled highly crystalline tin oxide nanoparticles, which were synthesized through a simple hydrothermal approach, onto the chemical template of octadecyltrimethoxysilane self-assembled monolayer (OTS-SAM). Tin oxide nanoparticles were synthesized by refluxing ethanol containing 0.1M of tin (IV) chloride pentahydrate at 70°C for 3h, and subsequently hydrothermally treating the resulted precipitates at 200°C for 80h. As a result, we could obtain the highly crystalline tin oxide nanoparticles. The average particle size and its distribution were estimated by high-resolution transmission electron microscopy observation to be about 5.8nm and 27.6%. Area-selective assembly of tin oxide nanoparticles was performed by dipping a few drops of the suspension containing the nanoparticles onto the OTS-SAM template-covered silicon substrates, and then sonicating the substrate covered with the dried suspension in absolute toluene for 10min. The nanoparticles assembled on the methyl-covered regions of the template were easily eliminated from the surface by the sonication, while those on the silanol-covered regions of the template remained tightly adhered to the substrate surface. As confirmed by atomic force microscopy, one-dimensional microarray of tin oxide was achieved on the substrates.
SPM oxidation and parallel writing on zirconium nitride thin films
Authors: Farkas N. , Comer J. R. , Zhang G. , Evans E. A. , Ramsier R. D. , Dagata J. A.
Published: September 2005

Systematic investigation of the SPM oxidation process of sputter-deposited ZrN thin films is reported. During the intrinsic part of the oxidation, the density of the oxide increases until the total oxide thickness is approximately twice the feature height. Further oxide growth is sustainable as the system undergoes plastic flow followed by delamination from the ZrN–silicon interface keeping the oxide density constant. ZrN exhibits superdiffusive oxidation kinetics in these single tip SPM studies. We extend this work to the fabrication of parallel oxide patterns 70 nm in height covering areas in the square centimeter range. This simple, quick, and well-controlled parallel nanolithographic technique has great potential for biomedical template fabrication.
TiN
∕
Ta
2
O
5
∕
PE
–
SiN
∕
TiN
metal-insulator-metal capacitor for radio frequency and mixed signal integrated circuit applications
Authors: Chung Y. S. , Kim K. S. , Ryu Y. S. , Lee D. , Hwang S. B. , Shin C.-S. , Park S. K. , Lee J. G.
Published: September 2005

Ta 2 O 5 ∕ PE – SiN metal-insulator-metal (MIM) capacitors with high capacitance density of 4.7fF∕μm2 for mixed-signal rf applications were originally integrated by adopting 120Å-thick-PE–SiN as a barrier layer between bottom electrode and 80-Å-thick metal-organic chemical-vapor deposition Ta2O5 layer. Inserting a PE–SiN layer resulted in dramatic reduction of leakage current at −3.3V from 8.0E–5A∕cm2 with only Ta2O5 film to 9.3E–8A∕cm2 with Ta2O5∕PE–sin layers. It was probably that the PE–SiN layer in the laminated structure provided a higher energy barrier than Ta2O5 as well as a physical diffusion barrier against oxygen into the bottom electrode. These laminated MIM capacitors also showed good linearities of capacitance with 302ppm∕V2, 125ppm∕V, and 30.7ppm∕°C as well as an excellent matching property with 0.79%μm. The breakdown voltage of capacitor was about 6MV∕cm and the lifetime (time-to-breakdown) of Ta2O5∕PE–SiN MIM capacitor at 3.7V and 25°C was 198 000 years. The quality factor of 53.9 and capacitance density of 5.08fF∕μm2 at 2.4GHz were obtained for 10×10μm2 MIM capacitors.
Effect of Mn composition of characterization of Zn1−xMnxS epilayers
Authors: Yu Y.-M. , Kim D. J. , Eom S. H. , Choi Y. D. , Kim T.-H. , O Byungsung
Published: September 2005

Zn 1 − x Mn x S epilayers have been grown on GaAs (100) substrates by hot-wall epitaxy. The structure of the epilayers was found to be zincblende over a large Mn composition range, 0⩽x⩽0.52. The relation between the Mn composition determined by energy dispersive x-ray spectrometry and the lattice constant by double crystal rocking curve was found to be consistent with Vegard’s law. A broad Mn2+-related transition near 2.1eV was observed in the low- and room-temperature photoluminescence (PL) spectra. The Mn composition dependence of PL peak energy was also investigated.
Uniformity study in large-area showerhead reactors
Authors: Sobbia R. , Sansonnens L. , Bondkowski J.
Published: September 2005

Large area plasma-enhanced chemical vapor deposition of thin films such as silicon nitride or amorphous silicon is widely used for thin film transistor fabrication in the flat panel display industry. A numerical three-dimensional model to calculate the deposition uniformity over the whole electrode surface for rf rectangular showerhead reactors powered at 13.56MHz is presented. The simulation tool is a commercially available finite-volume software (CDF-ACE®) which solves the multispecies, multireaction chemistry in capacitively coupled rf plasma. In order to simplify the three-dimensional geometry, the injected gas flow distribution across the showerhead is calculated separately and introduced as volumetric source terms for the gas flow and species continuity equations. The model is applied to the particular case of silicon nitride deposition and the results are compared with uniformity profiles obtained in an industrial plasma enhanced chemical vapor deposition reactor. Perturbations due to reactor edges together with nonuniform distribution of voltage due to standing wave effect are investigated as possible sources of the inhomogeneity of the thin film.
Blue photoluminescence of Si nanocrystallites embedded in silicon oxide
Authors: Kim Gun Hee , Kim Jong Hoon , Jeon Kyung Ah , Lee Sang Yeol
Published: September 2005

Luminescent characteristics of Si nanocrystallites have been reported depending on deposition condition. Si nanocrystalline thin films on p-type (100) silicon substrate have been prepared by pulsed laser deposition technique using a Nd:YAG laser. Strong blue photoluminescence has been observed at room temperature. The optical properties of thin films have been investigated as functions of laser energy densities, annealing gases, and target-substrate distances. These results indicate that the blue photoluminescence of Si nanocrystallites is related to the quantum size effect of Si nanocrystallites.
Evaluation of silicon oxide cleaning using F2∕Ar remote plasma processing
Authors: Kang S. C. , Hwang J. Y. , Lee N.-E. , Joo K. S. , Bae G. H.
Published: September 2005

In this study, chamber cleaning experiments using a F2∕Ar remote plasma generated from a toroidal-type remote plasma source were carried out in a plasma enhanced chemical vapor deposition (PECVD) system. The cleaning processes for the various silicon oxide layers, including PE-oxide (deposited by PECVD using SiH4 and N2O), O3-TEOS oxide (deposited by thermal CVD using ozone and TEOS precursor), and BPSG (borophosphosilicate glass), were investigated by varying the various process parameters, such as the F2 gas flow rate, the F2∕(F2+Ar) flow ratio, and the cleaning temperature. The species emitted during cleaning were monitored by Fourier transformed infrared spectroscopy and residual gas analysis. Under the current experimental conditions, the cleaning rate of the BPSG was 4.1–5.0 and 3.9–7.3 times higher than that those of the PE-oxide and O3-TEOS oxide layers, respectively, at room temperature and an F2∕(F2+Ar) flow ratio of 28.5%–83%. As the cleaning temperature increased from 100 to 350 °C, the cleaning rates of the PE-oxide, O3-TEOS oxide, and BPSG layers were increased by factors of 2.0–3.0, 1.5–2.2, and 3.0–3.4, respectively, at an F2∕(F2+Ar) flow ratio of 28%–68%. The F2∕(F2+Ar) flow ratio and cleaning temperature were found to be the most critical parameters involved in determining the cleaning rate of the various oxide layers.
Transparent and semitransparent conducting film deposition by reactive-environment, hollow cathode sputtering
Authors: Delahoy A. E. , Guo S. Y.
Published: September 2005

Highly transparent and conductive In2O3 and ZnO films containing different doping elements such as Ti, Mo, Zr, Nb, Ta, W (for In2O3), and B (for ZnO) have been prepared by reactive-environment, hollow cathode sputtering (RE-HCS). The use of Nb and W as effective dopants is reported for the first time. Metallic targets were used exclusively, and the dopant concentration was easily controlled using a second sputtering power supply. As a result of the cathode and gas flow geometry, the sputtering is conducted in metal mode, and the target and doping materials are free from oxidation during the deposition process. Film resistivities achieved with the various dopants are reported. For In2O3:Mo (IMO), a resistivity of 1.6×10−4Ωcm and a mobility of 80cm2∕Vs were achieved for Mo concentrations in the range 0.5–5.0% as measured by inductively coupled plasma (ICP). X-ray photoelectron spectroscopy (XPS) analysis indicates Mo with a +6 valence state and that the film is stoichiometric. For In2O3:Ti (ITiO), a superior optical transmission is achieved relative to IMO, while carrier mobility and conductivity were similar. Remarkably, semitransparent films of InN:O having sheet resistances of 9.5Ω∕square have also been prepared. ZnO:B films deposited by RE-HCS exhibit superior optical properties relative to ZnO:Al, and when applied as a window layer to CIGS solar cells yield higher quantum efficiencies.
Fabrication of NiSi2 nanocrystals embedded in SiO2 with memory effect by oxidation of the amorphous Si∕Ni∕SiO2 structure
Authors: Yeh P. H. , Wu H. H. , Yu C. H. , Chen L. J. , Liu P. T. , Hsu C. H. , Chang T. C.
Published: September 2005

NiSi 2 nanocrystals embedded in the SiO2 layer exhibiting a memory effect have been formed by dry oxidation of an amorphous Si∕Ni∕SiO2 structure at 900 °C. A pronounced capacitance-voltage hysteresis was observed with a memory window of 1 V under the 2 V programming voltage for the samples. For dry oxidation at 800 °C, no distinct memory effect was detected. The processing of the structure is compatible with the current manufacturing technology of the semiconductor industry. The structure represents a viable candidate for low-power nanoscaled nonvolatile memory devices.
Influence of sputtering parameter on the optical and electrical properties of zinc-doped indium oxide thin films
Authors: Pan Han-Chang , Shiao Ming-Hua , Su Chien-Ying , Hsiao Chien-Nan
Published: September 2005

The zinc doped indium oxide (IZO) films deposited with various sputter parameters such as, film thickness ranging from 200to500nm, O2∕Ar ratio ranging from 0% to 12%, and sputter power ranging from 100to250W was studied in this work. For a 200nm thick IZO film grown at room temperature in pure argon atmosphere, the resistivity was 2.4×10−4Ωcm and the average transmittance in the visible region was 80%. The root mean square roughness of IZO film was around 0.4nm regardless of the film thickness due to the IZO films exhibiting an amorphous structure. With increasing film thickness, the IZO films showed an increase in the resistivity and energy band gap. X-ray photoelectron spectroscopy analysis suggests that the IZO films with reduction of O2∕Ar ratio possess two splitting O1s binding energy levels, suggesting the IZO films were oxygen deficient and resulted in a lower resistivity.
Design for a kinematic, variable flux microcapillary array molecular beam doser
Authors: Fisher Gregory L. , Meserole Chad A.
Published: September 2005

The design of a microcapillary array for dosing gases in ultrahigh vacuum (UHV) is reported. The current design improves upon previous designs in ease of fabrication and assembly, and combines the attributes of minimum dead volume, minimum gas load on the vacuum system, collimated molecular flow, the ability to optimize dosing geometry and withdraw the doser when not in use, and ultimate UHV compatibility. These design characteristics result in an optimum source–target spacing enabling uniform, quantitative exposure of samples up to 1in. in diameter.
Piezoelectric and dielectric properties of Pb(Zr,Ti)O3–Pb(Mn,W,Sb,Nb)O3 with Ag2O addition
Authors: Chung Hyun Woo , Lim Sung Hun , Lee Eun Sun , Kim Gun Hee , Lee Sang Yeol
Published: September 2005

The effects of Ag2O addition on the dielectric and piezoelectric properties of 0.96Pb(Zr,Ti)O3–0.04Pb(Mn,W,Sb,Nb)O3 (PZT–PMWSN) ceramics and thin films deposited on a Pt∕Ti∕SiO2∕Si substrate by pulsed laser deposition have been investigated. By varying the contents of silver from 0∼3mol.%, the effect of Ag2O addition on PZT–PMWSN ceramics and thin film was systematically observed. No reaction between silver and PZT is observed in X-ray diffraction analysis. Enhanced sinterability of PZT–PMWSN ceramics with Ag2O addition increased the electromechanical quality factor (kp) and mechanical quality factor (Qm). As silver content increased, it was observed that the relative dielectric constant (ϵr) increased because of increasing effective dielectric field in the dielectric phase.
Area-selective assembly of high crystalline tin-doped–indium–oxide particles onto monolayer template
Authors: Shirahata Naoto , Sakka Yoshio , Uchikoshi Tetsuo , Hozumi Atsushi
Published: September 2005

Well-defined microstructures of tin-doped–indium–oxide (ITO) were successfully fabricated on a monoalyer template through an electrostatic interaction in aqueous media without any chemical and physical etching processes. Highly oriented amino-terminated self-assembled monolayers (SAMs) were formed on the SiO2∕Si substrate in a vapor of 12.5vol% solution of N-(6-aminohexyl)-3-aminopropyltrimethoxysilane [H2N(CH2)6NH(CH2)3Si(OCH3)3, AHAPS] diluted with absolute toluene. A chemical template of AHAPS–SAM was photolithographycally prepared using 172nm vacuum ultraviolet light under a reduced pressure of 10Pa for 30min through a photomask. The fabricated chemical template composed of AHAPS- and SiOH-covered regions served, respectively, as electrostatically repulsive and attractive areas to provide a monolayer template for the area-selective assembly of ITO particles. The ITO particles assembled preferentially onto the silanol regions through the electrostatic interaction, while their assembly was prevented on the amino-terminated regions because of the electrostatic repulsion between the particle’s surface and the terminated amino groups. The resistivity of the ITO particulate film formed on silanol region was measured to be 4.0×10−3Ωcm.
Surface modification of silicon-containing fluorocarbon films prepared by plasma-enhanced chemical vapor deposition
Authors: Jin Yoonyoung , Desta Yohannes , Goettert Jost , Lee G. S. , Ajmera P. K.
Published: September 2005

Surface modification of silicon-containing fluorocarbon (SiCF) films achieved by wet chemical treatments and through x-ray irradiation is examined. The SiCF films were prepared by plasma-enhanced chemical vapor deposition, using gas precursors of tetrafluoromethane and disilane. As-deposited SiCF film composition was analyzed by x-ray photoelectron spectroscopy. Surface modification of SiCF films utilizing n-lithiodiaminoethane wet chemical treatment is discussed. Sessile water-drop contact angle changed from 95°±2° before treatment to 32°±2° after treatment, indicating a change in the film surface characteristics from hydrophobic to hydrophilic. For x-ray irradiation on the SiCF film with a dose of 27.4kJ∕cm3, the contact angle of the sessile water drop changed from 95°±2° before radiation to 39°±3° after x-ray exposure. The effect of x-ray exposure on chemical bond structure of SiCF films is studied using Fourier transform infrared measurements. Electroless Cu deposition was performed to test the applicability of the surface modified films. The x-ray irradiation method offers a unique advantage in making possible surface modification in a localized area of high-aspect-ratio microstructures. Fabrication of a Ti-membrane x-ray mask is introduced here for selective surface modification using x-ray irradiation.
High-energy ions and atoms sputtered and reflected from a magnetron source for deposition of magnetic thin films
Authors: Matsui Hiroki , Toyoda Hirotaka , Sugai Hideo
Published: September 2005

In the magnetron sputtering process, moderate bombardment of particles on a substrate gives favorable effects on the deposited films, while excessive bombardment at high energies may cause film damage and surface roughness. To make these influences clear, high-energy ions and neutrals are comprehensively measured by a mass spectrometer with an energy analyzer in the case of magnetron sputtering of a Permalloy™ target (80%Ni∕20%Fe). Ni atoms sputtered from the target by a dc magnetron discharge (∼600V, <0.2A) in argon below 4 Pa have an energy distribution function (EDF) spreading up to ∼8eV. A similar shape of EDF is also observed for Ni+ ions, which are produced possibly by electron-impact ionization of Ni atoms in gas phase. The EDF of Ar+ ions has a tail of extremely high energies of ∼150eV. Production of such energetic ions is tentatively explained in terms of resonant charge exchange of energetic Ar atoms reflected from the target after surface neutralization of ∼600eVAr+ ions impinging on the target. The existence of energetic Ar atoms is verified by mass spectrometry with an extra-ionizer, and is also supported by a sputtering simulation code (TRIM).
Plasma-based ion implantation sterilization technique and ion energy estimation
Authors: Tanaka T. , Watanabe S. , Shibahara K. , Yokoyama S. , Takagi T.
Published: September 2005

Plasma-based ion implantation (PBII) is applied as a sterilization technique for three-dimensional work pieces. In the sterilization process, a pulsed negative high voltage (5μs pulse width, 300pulses∕s,−800V to −13kV) is applied to the electrode (workpiece) under N2 at a gas pressure of 2.4 Pa. The resultant self-ignited plasma is shown to successfully reduce the number of active Bacillus pumilus cells by 105 times after 5 min of processing. The nitrogen ion energy is estimated using a simple method based on secondary ion mass spectroscopy analysis of the vertical distribution of nitrogen in PBII-treated Si.
Organic polymer thin films deposited on silicon and copper by plasma-enhanced chemical vapor deposition method and characterization of their electrochemical and optical properties
Authors: Bae I.-S. , Cho S.-H. , Park Z. T. , Kim J.-G. , Boo J. H.
Published: September 2005

Polymer-like thin films have been deposited on glass, silicon, and copper substrates at a room temperature to 100 °C by the plasma-enhanced chemical vapor deposition method using cyclohexane (C6H12) as a precursor for analysis of these substrates electrochemical and optical characteristics. Cyclohexane was utilized as an organic precursor and hydrogen and Ar (argon) were used as a bubbler and carrier gases, respectively. In order to compare the difference between the corrosion-resistant and the optical properties of the plasma-polymerized organic thin films, conditions of various radio frequencies (rf) using 13.56 MHz power in the range of 20–50 W and deposition temperature were used. The optical and electrical properties of the as-grown plasma polymerized thin films were analyzed by Fourier transform infrared spectrophotometer, ultraviolet-visible spectroscopy, current–voltage, and capacitance-voltage curves. The corrosion-protective abilities of cyclohexane were also examined by ac impedance measurements in a 3.5 wt. % NaCl solution. We found that the corrosion-protection efficiency (Pk), which is one of the important factors for corrosion protection in the interlayer dielectrics of microelectronic-device application, was increased with increasing rf power. The highest Pk value of plasma-polymerized cyclohexane film was (85.26% at 50 W), atomic-force-microscope, and scanning electron microscopy showed that the polymer films with smooth surfaces and sharp interfaces could be grown under various deposition conditions.
Elementary examples of adiabatic invariance
Authors: Crawford Frank S.
Published: September 2005

Simple classical one-dimensional systems subject to adiabatic (gradual) perturbations are examined. The first examples are well known: the adiabatic invariance of the product Eτ of energy E and period τ for the simple pendulum and for the simple harmonic oscillator. Next, the adiabatic invariants of the vertical bouncer are found—a ball bouncing elastically from the floor of a rising elevator having slowly varying velocity and acceleration. These examples lead to consideration of adiabatic invariance for one-dimensional systems with potentials of the form V=axn, with a=a(t) slowly varying in time. Then, the horizontal bouncer is considered—a mass sliding on a smooth floor, bouncing back and forth between two impenetrable walls, one of which is slowly moving. This example is generalized to a particle in a bound state of a general potential with one slowly moving ‘‘turning point.’’ Finally, circular motion of a charged particle in a magnetic field slowly varying in time under three different configurations is considered: (a) a free particle in a uniform field; (b) a free particle in a nonuniform ‘‘betatron’’ field; and (c) a particle constrained to a circular orbit in a uniform field.
The quantum mechanical Hamiltonian in curvilinear coordinates: A simple derivation
Authors: Kjaergaard Henrik Grum , Mortensen Ole Sonnich
Published: September 2005

The quantum mechanical Hamiltonian in curvilinear coordinates is obtained in a straightforward manner without using results from tensor analysis.