bluuebunny/crossref_metadata_2025 huggingface dataset:
Social networks and tax (non‐)compliance in a multicultural nation
Authors: Rothengatter Maarten R.
Published: July 2005

Purpose

The purpose of this article is to explore the role that different structures of socially embedded networks themselves play in tax non‐compliance or evasion, and the contribution that an application of network analysis can make to the study of tax compliance regulation.

Design/methodology/approach

This exploratory study applies a network approach and uses focus‐group interviewing to unveil tax evasive behaviours that are deeply embedded in specifically selected and structurally different trading networks.

Findings

Indicate the kinds of difficulties that tax regulators may face in their attempts to deal with a range of law‐defying practices, which operate both within and among some structurally diversified (social) trading networks of a multicultural nation. The data confirm convincingly that tax evasive behaviours are not solely peculiar to immigrant (NESB) business networks, but are mirroring many beliefs, norms and informal practices that also exist strongly in non‐immigrant networks.

Practical implications

A mixed‐embedded network approach that grasps the rich contexts and complexities involved in the informal behaviours of “networked” small‐business entrepreneurs is to be regarded as a powerful tool in the governance of modern taxation systems.

Originality/value

Fills a gap in the research (literature) on the tax‐compliance behaviours among citizens of a multicultural nation and may have potential for a wider application.
Evaluation of relatively low dose of oral transmucosal ketamine premedication in children: a comparison with oral midazolam
Authors: HORIUCHI TOSHINORI , KAWAGUCHI MASAHIKO , KUREHARA KOUKICHI , KAWARAGUCHI YOSHITAKA , SASAOKA NORIYUKI , FURUYA HITOSHI
Published: July 2005

Background : Oral Transmucosal ketamine (lollipop) has been shown to be an effective, harmless preoperative medication for children. However, its efficacy was not compared with commonly used premedication drugs. We, therefore, compared the efficacy of oral transmucosal ketamine with oral midazolam for premedication in children.

Methods : Fifty‐five children (2–6 years of age) were randomized to receive orally either a lollipop containing 50 mg of ketamine (the group K; n = 27) or syrup containing 0.5 mg·kg−1 of midazolam (the group M; n = 28) before minor surgery. A five points‐sedation score (1 = asleep to 5 = agitated; scores 2 and 3 were defined as ‘effective’) on arrival in the operating room and a three points‐acceptance score of separation from the parents and a three points‐mask cooperation score at induction of anesthesia (1 = easy to 3 = markedly resistant; score 3 was defined as ‘poor’) were used.

Results : Sedation scores in group K were significantly higher than those in group M (P = 0.012), and the incidence of ‘effective’ in sedation was significantly lower in group K than in group M (P = 0.036). The incidence of ‘poor’ at separation from the parents and for mask cooperation was significantly higher in group K than in group M (P = 0.017, P = 0.019, respectively).

Conclusion : These results indicate that a relatively low dose of oral transmucosal ketamine premedication provides no benefits over oral midazolam in children.
Long‐term use of clonidine in a critically‐ill infant
Authors: LOWERY REBECCA , ZUK JEANNIE , POLANER DAVID M.
Published: July 2005

We report the use of clonidine in an infant as an adjunct to sedation and analgesia for 4 months in the critical care setting. Advantages, potential side effects, and dosing for multiple modes of delivery are discussed.
An evaluation of pain and postoperative nausea and vomiting following the introduction of guidelines for tonsillectomy
Authors: WHITE MICHELLE C. , NOLAN JUDITH A.
Published: July 2005

Background : Tonsillectomy and adenotonsillectomy have a high incidence of postoperative pain, and postoperative nausea and vomiting (PONV). Pain is traditionally controlled with morphine but this increases the risk of PONV and may cause respiratory depression. Antiemetics reduce PONV but their routine use has been questioned on safety grounds.

Method : After determining the current anesthetic management of elective tonsillectomy and adenotonsillectomy patients in our hospital, guidelines were developed to avoid the routine use of morphine and antiemetics. The effect on pain and PONV was then evaluated over a 3 month period. Postoperative pain was scored using the Oucher visual analog scale and nausea scored using a five point scale.

Results : We analysed 34 cases to determine our current practice and 37 cases to evaluate the effect of introducing guidelines. Postguidelines, the median Oucher pain score at 4 h was 10, and at 8, 12, 16 h was zero. Despite receiving no antiemetics, only two children vomited (5%) after introduction of guidelines.

Conclusion : Guidelines which use a combination of paracetamol, nonsteroidal anti‐inflammatory drugs and fentanyl, provide excellent analgesia with minimal PONV after elective tonsillectomy and adenotonsillectomy. As a result the routine use of morphine and antiemetics can be avoided.
Use of low‐dose rocuronium for intubation of children during volunteer surgery abroad1
Authors: POLITIS GEORGE D. , BRILL JUDITH , JONES JOHN
Published: July 2005

Background : Low‐dose rocuronium (ROC) might improve safety during volunteer surgery abroad (VSA) by facilitating intubation with a lower halothane concentration than is typically used. We hypothesized that 0.25 mg·kg−1 of ROC would improve intubation conditions during 3% halothane induction and still allow for rapid return to spontaneous ventilation (SV).

Methods : During Operation Smile's 2002 mission to Honduras, patients aged 3 months–11 years were randomized to receive ROC 0.25 mg·kg−1 (n = 19), or placebo (n = 23). Induction was with 3% halothane in 100% O2, with ventilation assisted and controlled when possible, and normocarbia maintained. An i.v. was placed after induction, and ROC or placebo given. Direct laryngoscopy (DL) was performed 3 min later by a blinded laryngoscopist who assessed conditions according to predetermined criteria.

Results : Adequate intubation conditions occurred in 89 and 87% of patients (P = 0.59), and mean times from DL until the return to SV were 9.8 and 4.3 min (P = 0.003), in the ROC and placebo groups, respectively. For the placebo group, the presence of SV at DL was predictive of inadequate intubation conditions (P = 0.006).

Conclusions : When administering 3% halothane for induction of VSA patients, a high frequency of adequate intubation conditions can be achieved without a relaxant, rendering the known benefits of 0.25 mg·kg−1 of ROC unapparent. ROC 0.25 mg·kg−1 does allow rapid return to SV.
Perinatal tuberculosis: implications of failure to isolate the lungs in an infant undergoing thoracotomy
Authors: SUBRAMANIAM RAJESHWARI , GUPTA SURBHI , PRASAD CHANDRASHEKARAIAH NAGENDRA
Published: July 2005

A 3‐month‐old male infant presented with intermittent low‐grade fever from the age of 1 month. On investigation, a nonhomogenous opacity was found in the upper lobe of the right lung. A computerized tomographic scan revealed loss of aeration of the right upper lobe and partial collapse of the middle lobe. A provisional diagnosis of congenital cystic adenomatoid malformation of the lung (with episodes of infection) was made. We describe the use of a single lumen tracheal tube (TT) for thoracotomy and lobectomy in this infant. The surgical procedure was complicated by a flood of thick, semisolid caseous material from the TT tube causing hypoxia and inability to ventilate the infant. The problem was managed appropriately in the circumstances. The infant died on the 10th postoperative day after two episodes of pneumothorax and, finally, sepsis, and multiorgan failure. Histopathological examination of the tissues and smears revealed acid‐fast bacilli in all fields and confirmed the diagnosis of perinatal tuberculosis. This appears to be the first report of its kind of an anesthetic complication of perinatal tuberculosis. A brief update on this condition and the importance of lung separation in infants undergoing thoracotomy is discussed.
Sevoflurane–remifentanil vs isoflurane–remifentanil for the surgical correction of craniosynostosis in infants
Authors: PIETRINI DOMENICO , CIANO FRANCESCA , FORTE ELIA , TOSI FEDERICA , ZANGHI FILIPPO , VELARDI FRANCESCO , DI ROCCO CONCEZIO , CHIARETTI ANTONIO , CARESTA ELENA , PIASTRA MARCO
Published: July 2005

Background : The aim of the present study was to compare the efficacy of isoflurane–remifentanil and sevoflurane–remifentanil combinations during neurosurgical correction craniosynostosis.

Methods : Twenty‐two infants with craniosynostosis received a slow bolus of remifentanil followed by continuous infusion. The infants were randomly divided into two groups: remifentanil followed by sevoflurane (the ‘sevoflurane group’), and remifentanil followed by isoflurane (the ‘isoflurane group’). We monitored electrocardiogram (ECG), heart rate (HR), invasive arterial blood pressure (IABP), pulse oximetry saturation (SpO2), endtidal CO2 (PEco2), inspired fraction of oxygen (FiO2) and endtidal volatile agent (PE volatile agent) at 12 time points, from the beginning of surgery (T0) until the cessation of drugs (T11). The volatile agent was stopped prior to skin suture and the remifentanil infusion after skin closure. Subsequently, we evaluated recovery time of spontaneous breathing and spontaneous eye opening and time of extubation at 5, 10, and 15 min after extubation, the Steward Recovery Score (SRS) was assessed. Patients were then transferred to the Pediatric Intensive Care Unit (PICU).

Results : During the surgical procedure the hemodynamic parameters between the two groups did not show statistically significant differences. There were also no significant differences in terms of awakening time or SRS.

Conclusions : The rapid recovery of the children (confirmed by their high values of SRS) makes it possible to reliably assess the patient's neurological condition immediately after surgery.
Micro‐scooter induced dental trauma: a case report
Authors: Dhillon Gulsharandip Kaur , Gulati Aakshay , Sherman Jeremy
Published: July 2005

Abstract –  There has been a remarkable increase in the popularity of micro‐scooters over the past few years. This has brought with it an astonishing rise in the number of associated injuries. Highlighted here is a case report which outlines the dental injuries associated with the use of a micro‐scooter.
Evaluation of the anti‐inflammatory effect of erythromycin on aseptic inflammation of temporomandibular joint in rabbit: a scintigraphic and histopathologic study
Authors: Ertaş Ümit , Tozoglu Sinan , Sahin Onder , Seven Bedri , Gundogdu Cemal , Aktan Bulent , Yildirim Mustafa
Published: July 2005

Abstract –  This article investigates the anti‐inflammatory effects of erythromycin (EM) on aseptic inflammation of temporomandibular joint (TMJ) space using by Tc‐99 m HIG scintigraphy and histopathology. In this experimental study, 33 adult male New Zealand White rabbits were divided into three groups. The animals in the first group were treated with EM 25 mg kg−1; the animals in the second group were treated with methylprednisolone (MP) 2 mg kg−1 and the animals in the third group were given saline solution (control group). Each drug was given by intraperitoneal injection twice a day for 7 days. Two hours after the last injection, carrageenan was injected into right TMJ of rabbits for aseptic inflammation. After carrageenan injection, each rabbit was given an intravenous injection of 111 Mbq (3 mCi) Tc‐99 m human HIG, and scanning was performed 4 h later. Later, all animals were killed and TMJ and periarticular tissues were resected. Histopathologically, the distance between synovial surface epithelium (SSE) and muscle layer (ML) in each section was measured by using SAMBA 200 Cell image processor with software. Scintigraphically, when lesion activity/adjacent region activity (L/N) was evaluated there was a significant difference between the control group and the other two groups (P < 0.05 for EM and MP). However, no significant difference was found between the EM and MP groups. Histopathologically, the mean distance between SSE and ML in the sections was found longer in the control group (78.6 ± 10.7 μm) than in the EM (44.38 ± 18.26 μm) and MP (44.05. ± 18.25 μm) groups. We think that administration of EM, which is a well‐known macrolid antibiotic, might be very effective in the treatment of aseptic inflammation of TMJ space. Because corticosteroid administration has many side effects, EM may be a preferable drug in the treatment of inflammation of TMJ.
Humoral immune response of patients with dental trauma and consequent replacement resorption
Authors: Hidalgo Mirian Marubayashi , Itano Eiko Nakagawa , Consolaro Alberto
Published: July 2005

Abstract –  Replacement dental resorption may be a consequence of trauma and may cause dental transplants or reimplants to fail. Previously, we demonstrated the participation of the immunopathological response in inflammatory dental resorption. The induction mechanisms of the two types of dental resorption are well known to be different. The aim of the present study was to observe the immune response of patients who suffered dental trauma with subsequent replacement dental resorption. Four patients with replacement radicular resorption and four healthy individuals with no evidence of radicular resorption participated in the study. The results of ELISA demonstrated that serum from patients with replacement dental resorption contained larger amounts of IgG and smaller amounts of IgM anti‐total human‐dentin extract and anti‐fractions of extract than did serum from control individuals. These results signal the hypothesis that dentin is immunogenic and the serological profile of patients with replacement dental resorption may be identified through biochemical analysis of their blood. Precise screening by this method may allow early diagnosis of dental resorption before it becomes visible radiographically.
Oral injuries in children: comparison of those children who visit and do not visit the after‐hours clinic after telephone consultation
Authors: Horie Norio , Shimoyama Tetsuo , Hasegawa Kiyoe , Kaneko Takahiro
Published: July 2005

Abstract –  Pediatric patients who sustain oral and dental injuries during the evening or night require telephone consultation and/or examination at our regional medical center in the oral surgery clinic. Between April 1, 2001 and March 31, 2003, a total of 393 patients (1–15 years old) sought advice; 67.7% came for a visit and examination after telephone consultation (visited patients) and 32.3% received telephone advice, but did not need to come for a medical visit (non‐visited patients). The busiest consulting time for both groups was the evening time band. Soft tissue injuries were the most frequent in both visited and non‐visited patients, 66.9 and 85.0% respectively. Particularly in non‐visited patients, the upper lip was the most significantly affected site (57.4%). The most common cause of injuries was falls (84.2% of visited and 77.2% of non‐visited patients). Of non‐visited patients, the most common reason not to visit was a minor injury that did not require examination (87.4%). We recommend that a personal telephone call from a dentist is important because telephone consultation can help triage patients and provide relief for the patient's guardians.
Asymptotics for the Characteristic Roots of Delayed Dynamic Systems
Authors: Wahi Pankaj , Chatterjee Anindya
Published: July 2005

Delayed dynamical systems appear in many areas of science and engineering. Analysis of general nonlinear delayed systems often begins with the linearized delay differential equation (DDE). The study of these linearized constant coefficient DDEs involves transcendental characteristic equations, which have infinitely many complex roots not obtainable in closed form. Here, after motivating our study with a well-known delayed dynamical system model for tool vibrations in metal cutting, we obtain asymptotic expressions for the large characteristic roots of several delayed systems. These include first- and second-order DDEs with single delays, and a first-order DDE with distributed as well as multiple incommensurate delays. For reasonable magnitudes of the coefficients of the DDEs, the approximations in each case are very good. Subsequently, a fourth delayed system involving coefficients of disparate magnitude is analyzed using an alternative asymptotic strategy. Finally, the large root asymptotics are complemented with calculations using Padé approximants to find all the roots of these systems.
Asymptotic Analysis of a Mode III Stationary Crack in a Ductile Functionally Graded Material
Authors: Kubair Dhirendra V. , Geubelle Philippe H. , Lambros John
Published: July 2005

The dominant and higher-order asymptotic stress and displacement fields surrounding a stationary crack embedded in a ductile functionally graded material subjected to antiplane shear loading are derived. The plastic material gradient is assumed to be in the radial direction only and elastic effects are neglected. As in the elastic case, the leading (most singular) term in the asymptotic expansion is the same in the graded material as in the homogeneous one with the properties evaluated at the crack tip location. Assuming a power law for the plastic strains and another power law for the material spatial gradient, we derive the next term in the asymptotic expansion for the near-tip fields. The second term in the series may or may not differ from that of the homogeneous case depending on the particular material property variation. This result is a consequence of the interaction between the plasticity effects associated with a loading dependent length scale (the plastic zone size) and the inhomogeneity effects, which are also characterized by a separate length scale (the property gradient variation).
Anisotropic Elastic
Tubes of Arbitrary Cross Section Under Arbitrary End Loads: Separation of Beamlike and Decaying
Solutions
Authors: Ladevèze P. , Simmonds J.
G.
Published: July 2005

First approximation analytical solutions are constructed for finite and semi-infinite, fully anisotropic elastic tubes of constant thickness h and arbitrary cross section, subject to purely kinetic or purely kinematic boundary conditions. Final results contain relative errors of O(h∕R), where R is some equivalent cross sectional radius. Solutions are decomposed into the sum of an exact beamlike or Saint-Venant solution, treated in Ladevèze et al. (Int. J. Solids Struct., 41, pp. 1925–1944, 2004) and extended in an appendix; a rapidly decaying edge-zone solution; and a slowly decaying semi-membrane-inextensional-bending (MB) solution. Explicit conditions on the boundary data are given that guarantee decaying solutions. The MB solutions are expressed as an infinite series of complex-valued exponential functions times real-valued one-dimensional eigenfunctions which satisfy a fourth-order differential equation in the circumferential coordinate and depend on the pointwise cross sectional curvature only.
Newmark’s Time Integration Method From the Discretization of Extended
Functionals
Authors: Bardella Lorenzo , Genna Francesco
Published: July 2005

In this note we illustrate how to obtain the full family of Newmark’s time integration algorithms within a rigorous variational framework, i.e., by discretizing suitably defined extended functionals, rather than by starting from a weak form (for instance, of the Galerkin type), as done in the past. The availability of functionals as a starting point is useful both as a tool to obtain new families of time integration methods, and as a theoretical basis for error estimates. To illustrate the first issue, here we provide some examples of how to obtain modified algorithms, in some cases significantly more accurate than the basic Newmark one despite having a comparable computational cost.
Multiscale Shock Heating Analysis of a Granular Explosive
Authors: Gonthier Keith A. , Jogi Venugopal
Published: July 2005

A multiscale model is formulated and used to characterize the duration and amplitude of temperature peaks (i.e., hot spots) at intergranular contact surfaces generated by shock compaction of the granular high explosive HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine). The model tracks the evolution of both bulk variables and localized temperature subject to a consistent thermal energy localization strategy that accounts for inelastic and compressive heating, phase change, and thermal conduction at the grain scale (grain size ∼50μm). Steady subsonic compaction waves having a dispersed two-wave structure are predicted for mild impact of dense HMX (porosity ∼19%), and steady supersonic compaction waves having a discontinuous solid shock followed by a thin compaction zone are predicted for stronger impact. Short duration hot spots having peak temperatures in excess of 900K are predicted near intergranular contact surfaces for impact speeds as low as 100m∕s; these hot spots are sufficient to induce sustained combustion as determined by a two-phase thermal explosion theory. Thermal conduction and phase change significantly affect hot-spot formation for low impact speeds (∼100m∕s), whereas bulk inelastic heating dominates the thermal response at higher speeds resulting in longer duration hot spots. Compressive grain heating is shown to be largely inconsequential for the range of impact speeds considered in this work (100⩽up⩽1000m∕s). Predictions for the variation in inelastic strain, pressure, and porosity through the compaction zone are also shown to qualitatively agree with the results of detailed mesoscale simulations.
A Method to Generate Damage Functions for Quasi-Brittle Solids
Authors: Cope D. , Yazdani S. , Ju J. W.
Published: July 2005

In continuum damage mechanics theories, damage functions are identified based on experimental records. These functions also serve as strain hardening-softening functions similar to the conventional plasticity formulations. In a class of damage theories described in this paper it will be shown that if care is not taken, internal contradictions will arise as manifested by a snapback in the strain–stress space. This paper establishes a formal method by which different damage functions can consistently be developed leading to no snap-back in the solution.
Collapse of Thick Cylinders Under Radial Pressure and Axial
Load
Authors: Corradi Leone , Luzzi Lelio , Trudi Fulvio
Published: July 2005

This paper provides the theoretical collapse loads of thick, long cylindrical shells subject to pressure and axial forces. Tubes are made of isotropic, perfectly plastic von Mises' material. Axial strains are assumed to be constant but possibly different from zero, so that elongation is permitted. This assumption, together with axial symmetry and the isochoric nature of plastic flow, unambiguously defines the set of possible collapse mechanisms, and collapse loads are computed on this basis. Results are contrasted to those presently available, based on thin-shell assumptions. Comparison shows that differences are of engineering significance, well worth considering for thick tubes, such as those envisaged in some nuclear power plant applications.
On a Perturbation Method for the Analysis of Unsteady Belt-Drive Operation
Authors: Leamy Michael J.
Published: July 2005

A perturbation method is presented for use in analyzing unsteady belt-drive operation. The method relies on the important assumption that for operating states close to steady operation, the friction state (i.e., whether the belt is creeping or sticking at any location on the pulley) is similar to that of the well-known steady solution in which a lone stick arc precedes a lone slip arc (Johnson, K. L., 1985, Contact Mechanics, Cambridge U.P., London, Chap. 8; Smith, D. P., 1999, Tribol. Int., 31(8), pp. 465–477). This assumption, however, is not used to determine the friction force distribution, and, in fact, the friction forces in the stick zone are found to be nonzero, in direct contrast to the steady solution. The perturbation analysis is used to derive expressions for the span tensions, the pulley tension distributions, the contact forces between the belt and the pulleys, and the angular velocity of the driven pulleys. Validity criteria are developed which determine bounds on the operation state for which the assumed friction state is upheld. Verification of response quantities from the perturbation solution is accomplished through comparison to quantities predicted by an in-house dynamic finite element model and excellent agreement is found. Additionally, the finite element model is used to verify the key assumption that a lone slip arc precedes a lone stick arc.
Synthesis and Experimental Validation of a Delayed Reference Controller for Active Vibration Suppression in Mechanical Systems
Authors: Gallina P. , Trevisani A.
Published: July 2005

This paper introduces a non-time-based control scheme for active position and vibration control of two-degree-of-freedom systems by applying it to the path-tracking and swing control of a system composed of a trolley and a simple pendulum. The basic idea behind such a scheme is to make the path reference of the trolley a function of the time and of a time delay. This latter, which is affected by the measured oscillation, is calculated on-the-fly in order to reduce the swing phenomenon. The effectiveness of the proposed control scheme, which may have application to the control of overhead cranes, is proved experimentally.
Effect of beryllium concentration on the size of self-assembled CdSe quantum dots grown on Zn1−xBexSe by molecular-beam epitaxy
Authors: Zhou X. , Tamargo Maria C. , Muñoz Martin , Liu H. , Couzis A. , Maldarelli C. , Huang Y. S. , Malikova L.
Published: July 2005

The effect of Be concentration on the formation of CdSe self-assembled quantum dots grown on Zn1−xBexSe by molecular-beam epitaxy has been investigated using photoluminescence, atomic force microscopy, contactless electroreflectance, and surface photovoltage spectroscopy. Systematic decrease of the quantum dot (QD) size by increasing the Be concentration (x) in the Zn1−xBexSe barrier layer has been demonstrated. A 233meV blueshift in the photoluminescence emission energy was obtained by changing the Be concentration of the barrier layer from x=0.02 to x=0.24. A corresponding decrease in the size of uncapped QDs was observed. Furthermore, a significant effect of unintentional variation in growth parameters on the size of the QDs was also evident. This suggests that very careful control of the growth conditions is essential in order to utilize this phenomenon for practical applications.
Electronic properties of ZnO epilayers grown on c-plane sapphire by plasma-assisted molecular beam epitaxy
Authors: Murphy T. E. , Chen D. Y. , Cagin E. , Phillips J. D.
Published: July 2005

Plasma-assisted molecular beam epitaxy was used to grow thin films of ZnO on c-plane sapphire substrates. The crystalline properties of the layers as measured by x-ray diffraction were found to improve with lower growth temperatures, where the full width at half maximum (FWHM) of the (0002) peak x-ray rocking curves was shown to be in the range of 100to1100arcsec. The surface roughness and crystalline quality were shown to be dependent on the Zn∕O flux ratio. The electronic properties were found to be improved for higher growth temperatures with carrier concentrations in the range of 1×1017–5×1018cm−3 and electron mobilities ranging from 80to36cm2∕Vs. P-type doping of the ZnO films was accomplished by introducing nitrogen into the oxygen plasma with resulting carrier concentration and hole mobility of 2.8×1018cm−3 and 9cm2∕Vs, respectively.
Molecular-beam epitaxial growth and characterization of (In0.5Al0.5)1−xMnxAs-(In0.5Ga0.5)1−xMnxAs: Thin films and superlattices
Authors: Maksimov O. , Sheu B. L. , Schiffer P. , Samarth N.
Published: July 2005

We describe the growth and properties of (In0.5Al0.5)1−xMnxAs and (In0.5Ga0.5)1−xMnxAs epilayers and superlattices. We find that the structural quality of the epilayers is similar to that of the more extensively studied In1−xMnxAs and Ga1−xMnxAs magnetic semiconductors and that we can incorporate significantly larger amounts of Mn (∼12%) without phase segregation. Magnetization measurements indicate that the Curie temperatures of (In0.5Ga0.5)1−xMnxAs and (In0.5Al0.5)1−xMnxAs(x∼0.11) epilayers are 95 and 25K, respectively. The Curie temperature of the (In0.5Ga0.5)1−xMnxAs∕(In0.5Al0.5)1−xMnxAs superlattices decreases with the increase of the Al∕(Al+Ga) ratio. We attribute this to a decreased overlap between the impurity band and the valence band because of an enhanced Mn acceptor activation energy.
Effects of antimony and ion damage on carrier localization in molecular-beam-epitaxy-grown GaInNAs
Authors: Bank S. R. , Wistey M. A. , Yuen H. B. , Lordi V. , Gambin V. F. , Harris J. S.
Published: July 2005

We investigate the effects of both nonradiative recombination centers and compositional inhomogeneity on low-temperature localization in GaInNAs quantum wells. With the introduction of antimony and a reduction of nitrogen plasma-related damage during growth, localization energies as low as 2.5meV are reported for single quantum well samples with room temperature emission at 1.5μm. Moreover, low-temperature photoluminescence spectra revealed a broad, sub-band-gap luminescence peak that is ascribed to plasma-related defects. Deviation from the Varshni dependence of the band gap below 50K was also observed and attributed to compositional inhomogeneity that localizes emission; however, no “S shape” was observed. Localization effects were found to depend upon the excitation density.
Impact of unintentional and intentional nitridation of the 6H-SiC(0001)Si substrate on GaN epitaxy
Authors: Kim Tong-Ho , Choi Soojeong , Morse Mike , Wu Pae , Yi Changhyun , Brown April , Losurdo Maria , Giangregorio Maria M. , Bruno Giovanni
Published: July 2005

We report the impact of both unintentional and intentional nitridation of 6H-SiC(0001)Si substrates on the epitaxial growth of GaN by molecular-beam epitaxy. The unintentional nitridation is dependent upon the details of the pregrowth Ga flash-off process used to remove surface oxides and to achieve a specific pregrowth surface reconstruction. The nucleation process and structural and morphological properties of GaN epitaxial layers are strongly influenced by the modifications of the SiC surface induced by the pregrowth preparation process. We found that residual oxygen at the SiC surface, unintentional SiC nitridation, and the formation of cubic GaN grains at the initial nucleation stage strongly decrease as the concentration of Ga used is increased during the flash cleaning. In addition, recent work has shown that the use of a SiN interlayer for GaN epitaxy on various substrates reduces dislocation density. We observe an improvement in the heteroepitaxy of GaN when the SiC surface is intentionally nitridized at low temperature prior to the initiation of growth.
Recent developments in surface studies of GaN and AlN
Authors: Feenstra R. M. , Dong Y. , Lee C. D. , Northrup J. E.
Published: July 2005

Recent developments in the structural analysis of GaN and AlN surfaces are reviewed, and the implications of these structures for molecular beam epitaxial growth are discussed. The GaN(0001), AlN(0001), and GaN(101¯0) surfaces are all found to be terminated by metallic layers containing approximately one bilayer of Ga or Al atoms. However, in contrast to GaN(0001) where the Ga bilayer exists in an incommensurate, fluid-like state at room temperature, the metallic layers for AlN(0001) and GaN(101¯0) form large-unit-cell commensurate structures with static atomic arrangements. Small amounts of H on the GaN(0001) surface leads to facet formation on the surface, whereas larger amounts of H produce a 2×2 surface arrangement that displaces the Ga bilayer. A possible model for the H-terminated GaN(101¯1) surface is introduced and first-principles total energy calculations employing a finite temperature thermodynamics approach are employed to determine the conditions in which it could be stable.
Dielectric functions of molecular-beam-epitaxy-grown Ga1−xMnxAs thin films
Authors: Weber Z. J. , Peiris F. C. , Liu X. , Furdyna J. K.
Published: July 2005

We have measured the dielectric functions of a series of molecular-beam-epitaxy-grown Ga1−xMnxAs thin films directly deposited on GaAs (100) substrates. Initially, x-ray diffraction experiments were employed to determine the alloy compositions of these samples. A rotating analyzer spectroscopic ellipsometer was used subsequently to measure the complex reflection ratio for each of the films in the energy range between 0.9 and 6.5eV. By modeling the ellipsometric data in the transparent region, we were able to determine the film thickness precisely. Extending the analysis into the absorption region, we were able to identify the dielectric functions for each of the Ga1−xMnxAs samples in the energy region of our measurement. All of the dielectric functions displayed the critical point structures related to the higher-order electronic transitions. To determine the characteristics associated with the higher-order electronic transitions, we fit the dielectric functions with a model that incorporates the energy band structure near critical points as well as discrete and continuum exciton states associated with each critical point. This enabled us to determine that both E1 and E1+Δ1 critical points blueshift slightly in the Ga1−xMnxAs alloy system as Mn is incorporated into the lattice.
Effect of thermal annealing on 120-nm-T-shaped-Ti∕Pt∕Au-gate AlGaN∕GaN high electron mobility transistors
Authors: Yamashita Yoshimi , Endoh Akira , Ikeda Keiji , Hikosaka Kohki , Mimura Takashi , Higashiwaki Masataka , Matsui Toshiaki , Hiyamizu Satoshi
Published: July 2005

We fabricated 120-nm-long-T-shaped-Ti∕Pt∕Au-gate AlGaN∕GaN high electron mobility transistors (HEMTs) on sapphire substrates and annealed them thermally to improve their Schottky contacts (i.e., to reduce interface traps, increase the Schottky barrier height, and get better adhesion), thereby reducing gate leakage current, achieving better gate controllability, and obtaining better dc and rf characteristics compared to the HEMTs with as-deposited Schottky gate metals. Rapid thermal annealing (RTA) was carried out successively at 500, 600, and 650°C. The drain-source current Ids decreased with RTA temperature up to 600°C and turned to increase at 650°C. The maximum transconductance gm̱max, on the other hand, increased up to 650°C, indicating that RTA improved the dc characteristics of the HEMTs. We confirmed the improvement of Schottky contacts by measuring gate leakage current Igs and calculating the Schottky barrier height ϕB. After RTA at 600°C, the Igs at a gate-source voltage Vgs of −10V was as much as three orders of magnitude lower than it was in the as-deposited condition and the ϕB was 0.27eV greater than it was in the as-deposited condition (1.16eV versus 0.89eV). After the RTA at 650°C, the ϕB was slightly less than it was after the RTA at 600°C. RTA at 600 and 650°C also improved the rf characteristics, increasing the cutoff frequency fT from 80to84GHz (5% increase) and increasing the maximum oscillation frequency fmax from 102to122GHz (20% increase).
Effect of gate hard mask and sidewall spacer structures on the gate oxide reliability of W∕WNx∕poly-Si gate MOSFET for high density DRAM applications
Authors: Lim Kwan-Yong , Cho Heung-Jae , Jang Se-Aug , Kim Yong Soo , Oh Jae-Geun , Lee Jung-Ho , Yang Hong-Seon , Sohn Hyun-Chul , Kim Jin-Woong
Published: July 2005

We have studied the effects of the gate hard mask and the gate spacer nitride film on the reliability of W∕WNx∕poly-Si gated devices. When the gate hard mask nitride film is used, severe degradation of the stress-induced leakage current (SILC) and the interface trap density (Dit) characteristics are observed in the large metal-oxide-semiconductor (MOS) capacitors. On the other hand, as the devices become smaller, the effects of the hard mask nitride film are relieved. The gate spacer stack plays a more critical role in the reliability of smaller devices. The oxide∕nitride (ON) spacered devices exhibit better reliability in terms of SILC, Dit, threshold voltage (Vth) shift, and transconductance (Gm) compared to those of the nitride∕oxide∕nitride (NON) spacered ones. These behaviors are explained by the mechanical stress of the nitride films.
Storage conditions for high-accuracy composition standards of AlGaAs
Authors: Bertness K. A. , Roshko A. , Asher S. E. , Perkins C. L.
Published: July 2005

AlGaAs epitaxial films were stored under different environmental conditions and the resulting surface oxidation and contamination variations measured with several analytical techniques. Auger depth profiles confirmed that contamination had been confined to within approximately 10nm of the surface for all specimens stored in controlled environments for over three years. We also performed an atomic force microscopy study on a multilayer structure, measuring the height of the oxides formed in air. Surface contamination was examined in more detail with time-of-flight secondary ion mass spectrometry and x-ray photoelectron spectroscopy. Surface oxides changed over time, and could be altered by sputtering. Sputtering was particularly effective in removing hydrocarbons. Based on these results, AlGaAs reference films for x<0.4 should remain stable for at least five years if stored in either nitrogen or vacuum environments, with allowance for periodic handling in air.
Micro∕nanotribological study of perfluorosilane SAMs for antistiction and low wear
Authors: Kasai Toshi , Bhushan Bharat , Kulik Gerit , Barbieri Laura , Hoffmann Patrik
Published: July 2005

In micro∕nanoelectromechanical systems (MEMS∕NEMS), surface-dominated forces, such as stiction∕adhesion and friction, play an important role because of the large surface-area-to-volume ratio. In order to control these forces and wear properties, optimal lubricant systems have been extensively investigated. Perfluoroalkyl self-assembled monolayers (SAMs) are considered to be a strong candidate since the fluorinated carbon backbones are expected to show lower adhesion and friction. In this paper, surface properties of perfluoroalkylsilane SAMs are investigated and compared with those of standard alkylsilane SAMs. The SAMs are deposited on silicon with a native oxide layer and silica substrates by a vapor deposition process. Surface properties, such as surface energy, water contact angle, roughness, adhesive and friction forces, and wear resistance, are evaluated. An atomic force microscope (AFM) is used for evaluations of the micro∕nanotribological properties. The influence of humidity, temperature, and sliding velocity is also examined. In addition, the tribological mechanisms of the SAMs on molecular scale are discussed based on the AFM observations to aid the design and selection of proper lubricants for MEMS∕NEMS.
Characterization of small-mismatch GaAsSbN on GaAs grown by solid source molecular beam epitaxy
Authors: Wicaksono S. , Yoon S. F. , Tan K. H. , Loke W. K.
Published: July 2005

GaAsSbN layers with small lattice mismatch to GaAs were studied for possible application as the intrinsic layer in a GaAs-based p-i-n photodetector. Our calculation has shown that small lattice mismatch GaAsSbN to GaAs could be achieved at an Sb∕N atomic ratio of 2.60. GaAsSbN was grown as the intrinsic layer for a GaAs∕GaAsSbN∕GaAs photodetector structure using solid-source molecular beam epitaxy in conjunction with a radio frequency (rf) plasma-assisted nitrogen source and valved antimony cracker source. The lattice mismatch of the GaAsSbN layer to GaAs was kept below 5000ppm, which is sufficient to maintain coherent growth of ∼0.5μm thick GaAsSbN on GaAs substrate. The growth temperature was varied between 420 and 520°C, and the Sb flux beam equivalent pressure between 1.7×10−8 and 2.3×10−8Torr to maintain coherent growth. All samples exhibit room temperature photocurrent response in the 1.3μm wavelength region. X-ray diffraction two-dimensional maps showed diffuse scattering, which may have been caused by point defects in the material.
Improved high temperature growth of GaInNAsSb by molecular beam epitaxy
Authors: Maranowski K. D. , Smith J. M. , Fanning T. R. , Jewell J. L.
Published: July 2005

GaInNAs(Sb) quantum wells were grown by plasma-assisted molecular beam epitaxy on GaAs substrates. The effects of both growth temperature and the addition of Sb flux on the material quality were investigated with photoluminescence and x-ray diffraction. The photoluminescence intensity and structural quality of GaInNAs quantum wells drops rapidly as the growth temperature is increased above 480°C. However, at a growth temperature of 500°C, adding a relatively small amount of Sb dramatically recovers the photoluminescence intensity of the quantum well. Furthermore, the addition of Sb suppresses N surface diffusion, enabling the growth of high quality GaInNAsSb at temperatures as high as 530°C.
Molecular beam epitaxial growth of AlGaAs∕InGaAs∕GaAs planar superlattice structures on vicinal (111)B GaAs and their transport properties
Authors: Akiyama Y. , Kawazu T. , Noda T. , Koshiba S. , Torii K. , Sakaki H.
Published: July 2005

Al Ga As ∕ In Ga As ∕ Ga As planar superlattice structures have been formed by depositing a very thin InGaAs layer onto vicinal (111)B GaAs surfaces, where the bunching of atomic steps has resulted in a corrugation of about 20–30nm in period and 2nm in height. The growth condition to form bunched steps with little irregularity is clarified. By selectively doping, electrons are introduced into such planar superlattices, and their transport parallel to and normal to the steps are studied. Clear Shubnikov–de Haas oscillations with specific features and quantized Hall plateaus are observed in both geometries, suggesting that electrons retain some of their quasi-two-dimensional characters. In-plane anisotropies of electron mobilities are studied, and discussed in terms of electron scatterings by step structures. Photoluminescence spectra are studied to evaluate the in-plane potential modulation and its inhomogeneities.
Effects of oxygen plasma on optical and electrical characteristics of multiwall carbon nanotubes grown on a four-probe patterned Fe layer
Authors: Lee Jeong-Soo , Chandrashekar Anand , Park Bong Mo , Overzet Lawrence J. , Lee G. S.
Published: July 2005

We report on the fabrication and electrical characterization of aligned multiwall nanotubes (MWNTs) grown on a four-probe patterned catalyst layer. This structure has been designed to directly measure the electrical property of as-grown MWNTs. The temperature-resistance results show that the aligned MWNTs are semiconducting in directions perpendicular to the tube axis and follow the three-dimentional hopping conduction mechanism. Effects of oxygen plasma on the characteristics of the MWNTs are also investigated. Raman spectroscopy results indicate that oxygen plasma treatments can be used to reduce the carbonaceous material in the film. As the exposure time of oxygen plasma increases, the resistance of the aligned MWNTs increases mainly due to the suppression of current conduction through carbonaceous materials. These results suggest that oxygen plasma treatment is effective in improving the film quality of as-grown MWNTs.
Millisecond microwave annealing: Driving microelectronics nano
Authors: Thompson Keith , Booske J. H. , Ives R. L. , Lohr J. , Gorelov Yurii , Kajiwara Ken
Published: July 2005

The efficient deposition of high frequency microwave energy into the top several microns of a semiconducting material was experimentally demonstrated as a highly effective mechanism for rapid thermal annealing. Simulations show that absorbed power densities of 4 and 32kW∕cm2 produce average Si heating rates of 325 000 and 10000000°C∕s up to 1300°C. Conduction of thermal energy from the absorption region into the bulk substrate yields peak cooling rates that exceed 1000000°C∕s after the microwave pulse subsides. At the peak temperature, thermal gradients of 5 and 20°C∕μm exist for the aforementioned power densities of 4 and 32kW∕cm2. The application of a 4.5ms, 6kW∕cm2 pulse of 110GHz radiation resulted in an experimentally measured Si heating rate of 275000°C∕s. Applying this millisecond microwave anneal technology to ultrarapid annealing for shallow implanted dopants resulted in ultrashallow junctions that were 14–16nm deep with sheet resistances between 500 and 700Ω∕square and an estimated active dopant concentration of 1020∕cm3–2×1020∕cm3.
Effect of cerium concentration on the structural and ferroelectric properties of Bi4−xCexTi3O12 thin films for ferroelectric random access memories
Authors: Oh Young-Nam , Yoon Soon-Gil
Published: July 2005

The effect of cerium concentration on the structural and ferroelectric properties in Bi4−xCexTi3O12 (BCT) thin films grown using pulsed-laser deposition was studied. The BCT films with x=0.25 and 0.5 have a pure layered structure after annealing at 650°C in an oxygen ambient. On the other hand, films with x=0.75 still contained a pyrochlore phase as well as a layered structure. The remanent polarization of BCT thin films decreased with increasing Ce concentration. The BCT films with x=0.25 and 0.5 exhibit no polarization fatigue after electric field cycling up to 6×1010 switching cycles. The leakage current densities of samples measured at 100kV∕cm decreased slightly with decreasing Ce concentration.
Technology of polycrystalline diamond thin films for microsystems applications
Authors: Tang Yuxing , Aslam Dean M.
Published: July 2005

Large area and uniform polycrystalline diamond (poly-C) thin films, with a thickness of approximately 1μm, were grown and patterned on 4in. oxidized Si wafers using IC compatible processes for microsystems applications. Uniform and reproducible seeding with a density of 2×1010∕cm2 was achieved by spinning diamond powder loaded water on 4in. wafers. Gas mixture of 1.5% methane in hydrogen was used in MPCVD system for diamond film growth with optimized pressure and microwave power. Thickness variation of less than 20% was achieved on the 4in. area using 43Torr pressure and 2.8kW microwave power. Electron cyclotron resonance (ECR)-assisted microwave plasma reactive ion etch was carried out using SF6∕O2∕Ar gases to pattern the diamond films with an etch rate around 80nm∕min and less than 10% variation in etch rate over a 4in. area.
Effect of a surface inhibition layer on line edge roughness
Authors: Ma Yuansheng , Cerrina Franco
Published: July 2005

Line edge roughness (LER) is one of the most important issues in sub-100nm lithography. We have designed and implemented an experiment to study the coupled effect from acid depletion and percolation property of development process of Chemically Amplified Resist (CAR) on Line Edge Roughness (LER). The resist selected is UV-5 (a positive tone CAR from Shipley), known to be fairly sensitive to acid loss. After development, the resist is analyzed using high-resolution SEM (LEO 1550 VP), and an in-house made software is used for LER measurements. Our results indicate that the effect on LER and Critical Dimension (CD) variation depends on image modulation, and that aggressive lithography (low modulation image) will be more sensitive to the environment. In addition, it is shown that percolation development with stochastic energy deposition model can explain all the observed phenomena.