bluuebunny/crossref_metadata_2025 huggingface dataset:
Isokinetic Dynamometry and 1RM Tests Produce Conflicting Results for Assessing Alterations in Muscle Strength
Authors: Gentil Paulo , Del Vecchio Fabricio Boscolo , Paoli Antonio , Schoenfeld Brad J , Bottaro Martim
Published: March 2017

The purpose of this study was to compare strength gains in the lower limbs, assessed by one maximum repetition (1RM) and isokinetic peak torque (PT), in young men undergoing a resistance training (RT) program. Twenty-seven young men performed resistance training twice a week for 11 weeks. Training involved two exercises for the lower body, two for the upper body and one for the midsection performed with three sets of 8-12 repetitions to momentary muscle failure. Before and after the training period, participants performed the 1RM test in the 45° leg press and knee extension PT in isokinetic dynamometry. The Pearson correlation coefficient was used to assess the relationship between the changes in 1RM and PT, and the Bland-Altman test was performed to check for agreement between the strength changes of both tests. There were significant changes in 1RM and PT of 23.98% and 15.96%, respectively (p < 0.05). The changes in leg press 1RM were significantly higher than the ones in PT. The Bland-Altman analysis revealed that the tests were not equivalent. In conclusion, professionals and researchers involved in strength assessment should be aware that the results obtained by PT and 1RM are not equivalent when evaluating individual responsiveness and/or the efficacy of an intervention on muscle strength, as the results obtained show large variations and can be even conflicting.
Muscle Force-Velocity Relationships Observed in Four Different Functional Tests
Authors: Zivkovic Milena Z. , Djuric Sasa , Cuk Ivan , Suzovic Dejan , Jaric Slobodan
Published: March 2017

The aims of the present study were to investigate the shape and strength of the force-velocity relationships observed in different functional movement tests and explore the parameters depicting force, velocity and power producing capacities of the tested muscles. Twelve subjects were tested on maximum performance in vertical jumps, cycling, bench press throws, and bench pulls performed against different loads. Thereafter, both the averaged and maximum force and velocity variables recorded from individual trials were used for force–velocity relationship modeling. The observed individual force-velocity relationships were exceptionally strong (median correlation coefficients ranged from r = 0.930 to r = 0.995) and approximately linear independently of the test and variable type. Most of the relationship parameters observed from the averaged and maximum force and velocity variable types were strongly related in all tests (r = 0.789-0.991), except for those in vertical jumps (r = 0.485-0.930). However, the generalizability of the force-velocity relationship parameters depicting maximum force, velocity and power of the tested muscles across different tests was inconsistent and on average moderate. We concluded that the linear force-velocity relationship model based on either maximum or averaged force-velocity data could provide the outcomes depicting force, velocity and power generating capacity of the tested muscles, although such outcomes can only be partially generalized across different muscles.
Technique Selection ‘the Coaches Challenge’ Influencing Injury Risk During the First Contact Hand of the Round off Skill in Female Gymnastics
Authors: Farana Roman , Jandacka Daniel , Uchytil Jaroslav , Zahradnik David , Irwin Gareth
Published: March 2017

The importance of technique selection on elbow injury risk has been identified for the key round off skill in female gymnastics, with a focus on the second contact limb. The aim of this study was to shift the focus to the first contact limb and investigate the biomechanical injury risk during parallel and T-shape round-off (RO) techniques. Seven international-level female gymnasts performed 10 trials of the RO to back-handspring with parallel and T-shape hand positions. Synchronized kinematic (3D motion analysis system; 247 Hz) and kinetic (two force plates; 1235 Hz) data were collected for each trial. The t-test with effect size statistics determined differences between the two techniques. No significant differences were found for vertical, anterior posterior and resultant ground reaction force, elbow joint kinematics and kinetics. Specifically, the results highlighted that change in technique in RO skills did not influence first contact limb elbow joint mechanics and therefore, injury risk. The findings of the present study suggest the injury potential of this skill is focused on the second limb during the parallel technique of this fundamental gymnastic skill.
Adequacy of the Ultra-Short-Term HRV to Assess Adaptive Processes in Youth Female Basketball Players
Authors: Nakamura Fabio Y , Pereira Lucas A , Cal Abad Cesar C , Cruz Igor F , Flatt Andrew A , Esco Michael R , Loturco Irineu
Published: March 2017

Heart rate variability has been widely used to monitor athletes’ cardiac autonomic control changes induced by training and competition, and recently shorter recording times have been sought to improve its practicality. The aim of this study was to test the agreement between the (ultra-short-term) natural log of the root-mean-square difference of successive normal RR intervals (lnRMSSD - measured in only 1 min post-1 min stabilization) and the criterion lnRMSSD (measured in the last 5 min out of 10 min of recording) in young female basketball players. Furthermore, the correlation between training induced delta change in the ultra-short-term lnRMSSD and the criterion lnRMSSD was calculated. Seventeen players were assessed at rest pre- and post-eight weeks of training. Trivial effect sizes (-0.03 in the pre- and 0.10 in the post- treatment) were found in the comparison between the ultra-short-term lnRMSSD (3.29 ± 0.45 and 3.49 ± 0.35 ms, in the pre- and post-, respectively) and the criterion lnRMSSD (3.30 ± 0.40 and 3.45 ± 0.41 ms, in the pre- and post-, respectively) (intraclass correlation coefficient = 0.95 and 0.93). In both cases, the response to training was significant, with Pearson’s correlation of 0.82 between the delta changes of the ultra-short-term lnRMSSD and the criterion lnRMSSD. In conclusion, the lnRMSSD can be calculated within only 2 min of data acquisition (the 1st min discarded) in young female basketball players, with the ultra-short-term measure presenting similar sensitivity to training effects as the standard criterion measure.
Effects of Karate Fights on Achilles Tendon Stiffness Measured by Myotonometry
Authors: Pożarowszczyk Beata , Pawlaczyk Weronika , Smoter Małgorzata , Zarzycki Andrzej , Mroczek Dariusz , Kumorek Martyna , Witkowski Kazimierz , Adam Kawczyński
Published: March 2017

The aim of the study was to investigate the influence of karate fights on Achilles tendon stiffness in karate competitors. Eleven male karate fighters participated in the present study. A handheld MyotonPRO device (MyotonPRO, Myoton Ltd, Estonia) was applied to measure Achilles tendon stiffness in karate fighters. The Achilles tendon was tested 5 cm above the tuber calcanei. Stiffness measurements were performed before and after eight sparring fights. Each fight lasted 2 min and was separated by a 2 min rest period. Achilles tendon stiffness for the dominant leg increased significantly from before fights (751.57 ± 123.493 N/m) to immediately after fights (809.43 ± 160.425 N/m) (p = 0.012). Presented results should be used by strength and conditioning coaches in training programs as a way to decrease the risk of injury.
Plasma Actin, Gelsolin and Orosomucoid Levels after Eccentric Exercise
Authors: Tékus Éva , Váczi Márk , Horváth-Szalai Zoltán , Ludány Andrea , Kőszegi Tamás , Wilhelm Márta
Published: March 2017

The present study investigated the acute effect of eccentric exercise on blood plasma actin, gelsolin (GSN) and orosomucoid (AGP) levels in untrained and moderately trained individuals, and their correlation with exercise induced muscle damage (EIMD) markers (CK, intensity of muscle soreness and maximal voluntary contraction torque deficit). Healthy physical education students (6 untrained, 12 moderately trained) participated in this research. Actin, GSN, AGP and CK levels were measured in blood plasma at baseline, immediately, 1 h, 6 h and 24 h post-exercise comprising 90 eccentric quadriceps contractions performed on a dynamometer. There was significant time main effect for GSN, AGP, CK and significant difference was found between baseline and the lowest value of post-exercise GSN (p < 0.05), as well as baseline and the highest value of post-exercise AGP (p < 0.05). Relationships were found between GSN levels and other indirect EIMD markers (between all GSN levels at post-exercise and CK activity at 6 h, p < 0.05; GSNMIN and muscle soreness at post-exercise, p < 0.04), GSN and AGP; however, actin did not correlate at any time points with GSN. Actin, GSN, AGP and CK responses after eccentric exercise do not seem sensitive to training status. The plasma actin level is used as an indicator of injury, however, our results suggest that it is not an accurate marker of EIMD, while plasma GSN concentrations show a better relationship with EIMD and the post-exercise inflammatory process. The elevated plasma AGP and the correlation between GSN and AGP seem to be promising for assessment of exercise-induced muscle injury.
The Effect of Previous Wingate Performance Using one Body Region on Subsequent Wingate Performance Using a Different Body Region
Authors: Harvey Leonie , Bousson Matthew , McLellan Chris , Lovell Dale
Published: March 2017

The 30 second Wingate Anaerobic Test (WAnT) is the gold standard measure of anaerobic performance. The present investigation aimed to determine if a previous WAnT using one body region significantly affected a subsequent WAnT using a different body region. Twelve male university students (n = 12, 23 ± 2 years, 84 ± 16.1 kg, 178.5 ± 7.4 cm) volunteered to complete two repeated WAnT protocols (either lower body WAnT followed by an upper body WAnT or vice versa) on two separate testing occasions. The upper body WAnT was conducted on a modified electromagnetically braked cycle ergometer using a flywheel braking force corresponding to 5% bodyweight. The lower body WAnT was conducted on an electronically braked cycle ergometer using a flywheel braking force corresponding to 7.5% bodyweight. Participants had a 1 minute rest period for transition between WAnTs. Data are reported as mean ± standard deviation. No significant differences were identified in power indices for the lower body between 30 s WAnTs. When the upper body WAnT was performed 2nd, absolute peak power (p < 0.01), mean power (p < 0.001) and relative mean power (p < 0.001) were significantly lower compared to when the upper body WAnT was performed 1st. The value of maximum revolutions per minute was significantly lower (p < 0.001) when the upper body WAnT was performed after the lower body WAnT, compared to when it was performed 1st (193.3 ± 11.4 1st vs 179.8 ± 14.4 2nd). Previous upper body sprint exercise does not significantly affect lower body sprint exercise; however, previous lower body sprint exercise severely compromises subsequent upper body sprint performance.
Analysis of Motor Activities of Professional Soccer Players during the 2014 World Cup in Brazil
Authors: Chmura Paweł , Andrzejewski Marcin , Konefał Marek , Mroczek Dariusz , Rokita Andrzej , Chmura Jan
Published: March 2017

The aim of the present study was to analyze motor activities of soccer players in seven consecutive rounds of matches of the 2014 World Cup in Brazil and to compare the performance of the world champions, the German national team with other participating teams. The study sample comprised 905 observations of 340 soccer players, who played full-time matches in all seven rounds of the tournament. The study was conducted using data collected from the Castrol Performance Index, a kinematic game analysis system that records movements of players with semi-automatic cameras. The following variables were analyzed: total distance covered, the percentage of total distance covered at high intensity, the number of sprints, frequency of sprints and peak running speed. A statistically significant increase (p ≤ 0.01) was noted in total distance covered, the percentage of distance covered at high intensity and total number of sprints, between the quarter-finals and semi-finals of the World Cup tournament in Brazil. The German national team covered a significantly longer total distance (p ≤ 0.05) and had a greater percentage of distance covered at high intensity (p ≤ 0.001) than players from other teams. The obtained results point to the necessity of development of players’ aerobic endurance and speed-endurance abilities while preparing for top-level soccer tournaments. Winning a soccer championship requires players to run longer mean total distances and longer distances at high intensity during a single match.
3D transoesophageal echocardiography in the TAVI sizing arena: should we do it and how do we do it?
Authors: Bleakley Caroline , Eskandari Mehdi , Monaghan Mark
Published: March 2017

Transcatheter aortic valve implantation (TAVI) was initially proven as an alternative to valve replacement therapy in those beyond established risk thresholds for conventional surgery. With time the technique has been methodically refined and offered to a progressively lower risk cohort, and with this evolution has come that of the significant imaging requirements of valve implantation. This review discusses the role of transoesophageal echocardiography (TOE) in the current TAVI arena, aligning it with that of cardiac computed tomography, and outlining how TOE can be used most effectively both prior to and during TAVI in order to optimise outcomes.
Análisis de la apropiación y uso de las TIC por parte de las pymes colombianas
Authors: Puentes Ricardo
Published: March 2017

El desarrollo y la apropiación de las TIC (tecnologías de la información y de las comunicaciones) han marcado el rumbo de las naciones en la medida en que estas han asumido dichas tecnologías en todos los niveles. Los innumerables beneficios y promesas de la apropiación de estas tecnologías por parte de los ciudadanos, ante todo de las empresas que componen una economía, al parecer aún se hacen esperar.
Colombia no ha sido indiferente al proceso del desarrollo de las TIC. Mediante la creación de políticas y leyes enfocadas a buscar la masificación del uso de tecnologías, orientadas tanto al usuario final como al sector productivo, el país trata de incrustarse en exigentes procesos para tratar de asumirlas. Las diversas tecnologías computacionales y de información conforman el eje central del desarrollo comercial de las empresas; pero, para el caso colombiano, los esfuerzos llevados a cabo por los últimos gobiernos no han dado los resultados esperados, sobre todo en lo que concierne a las pequeñas y medianas empresas (pymes), como lo confirma la presente investigación.
Changes in the arteries in the course of hypertensive disease and extrasystoles
Authors: Didyc N. V. , Lysunets O. V.
Published: March 2017

Our research is focused on study of changes in the intima-media vascular wall of patients suffering from hypertensive disease as well as patients suffering from hypertensive disease and coexistent extrasystole. We examined 120 patients (42 men and 78 women) between the ages 27 to 81 suffering from hypertensive disease of the II stage as defined by the Ukrainian Association of Cardiologists and extrasystoles (more than 30 episodes per hour of research) of different topography and 30 persons (13 men and 17 women) suffering from hypertensive disease of the II stage between the ages 30 to 76 without rhythm disturbance. The first clinical group was formed of 54 (45%) patients suffering from repeated supraventricular extrasystoles. The second clinical group was formed of 42 (35%) patients suffering from repeated ventricular arrhythmia. The third group was formed of 24 (20%) patients suffering from both repeated supraventricular extrasystoles and ventricular extrasystoles. The results of treatment demonstrate that the existence of repeated supraventricular extrasystoles and ventricular extrasystoles in patients suffering from hypertensive disease of the ІІ stage in contrast to patients without arrhythmia and repeated supraventricular extrasystoles is associatesd with severer vascular dysfunction, which is defined by signs of rather high rigidity of the large arteries (significant reduction of original size of brachial artery diameter), severer defects of endothelium-dependant vasodilation (reduction of increment value of brachial artery diameter during the test with decompression, reduction of periodicity of registration of normal reaction and increase of paradoxical vasoconstriction of the brachial artery during the test with decompression) and significant reduction of general vasodilational potential, increase of frequency of cases with dissociation in the nature of endothelium-dependant and endothelium-independent reaction of the brachial artery. The latter changes were registered in 90 (60.0%) of examined patients, the most frequent of their variants were: 1) reduced reaction of the brachial artery for decompression + normal response in the test with nitroglycerine (29.7%) and 2) paradoxical vasoconstriction in response to decompression + reduced reaction on taking nitroglycerine (22.4%).
In vitro effects of some metal ions on glutathione reductase in the gills and liver of Capoeta trutta
Authors: Kirici M. , Atamanalp M. , Kirici M. , Beydemir Ş.
Published: March 2017

Many aquatic environmental problems have arisen in consequence of contamination of water by toxic metals and organic pollutants in the present age of technology. Metals play vital roles in enzyme activities and other metabolic events due to their bioaccumulative and nonbiodegradable properties among aquatic pollutants. The aim of this study was to evaluate the inhibitory effects of some metal ions (Ag+, Cu2+, Co2+, Ni2+, Pb2+ and Zn2+) on Capoeta trutta gill and liver glutathione reductase (EC: 1.8.1.7; GR). For this purpose, initially, GR was purified from C. trutta gill and liver. Purification procedure consisted of three steps; preparation of hemolysate, ammonium sulphate precipitation and 2’, 5’-ADP Sepharose 4B affinity chromatography. Using this procedure, C. turtta gill GR, having the specific activity of 19.111 EU/mg proteins, was purified with a yield of 38.8% and 910.05-fold; C. trutta liver GR, having the specific activity of 16.167 EU/mg proteins, was purified with a yield of 21.1% and 734.86-fold. The purity of the enzymes was checked on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and each purified enzyme showed a single band on the gel. In addition, inhibitory effects of some metal ions (Ag+, Cu2+, Co2+, Ni2+, Pb2+ and Zn2+) on GR from gill and liver were investigated in vitro. Ki constants and IC50 values for metal ions which showed inhibition effects were determined by Lineweaver-Burk graps and plotting activity % vs. [I]. In conclusion, IC50 values for fish gill GR were 0.000625, 0.153, 0.220, 0.247 and 0.216 mM and Ki constants for fish gill GR were 0.00045 ± 0.00008, 0.128 ± 0.036, 0.182 ± 0.138, 0.482 ± 0.219 and 0.112 ± 0.047 mM for Ag+, Cu2+, Co2+, Ni2+, Pb2+ and Zn2+, respectively. IC50 values for fish liver GR were 0.000437, 0.217, 0.185, 0.355 and 0.349 mM and Ki constants for fish liver GR were 0.00025 ± 0.00013, 0.532 ± 0.146, 0.123 ± 0.066, 0.093 ± 0.020 and 0.151 ± 0.084 mM for Ag+, Cu2+, Co2+, Ni2+, Pb2+ and Zn2+, respectively. In vitro inhibition rank order was determined as Ag+ > Co2+ > Zn2+ > Ni2+ > Pb2+ for fish gill GR; Ag+ > Cu2+ > Co2+ > Pb2+ > Ni2+ for fish liver GR. From these results, we showed that Ag+ metal ion is the most potent inhibitor of GR enzyme on gill and liver tissues.
From Pong to Pokemon Go, catching the essence of the Internet Gaming Disorder diagnosis
Authors: Carbonell Xavier
Published: March 2017

Taking as a starting point, this commentary proposes some issues regarding the diagnosis of Internet Gaming Disorder discussed in Kuss et al. (2016). In our opinion, the confusion in DSM-5 diagnosis could be due to the weak starting point in building the criteria. The criteria such as functional impairment and stability of the dysfunctional behavior are considered. It is suggested that avatar identification, playing motivations, and types of video games should be considered for diagnosis. The diagnostic process is highly influenced by social context and the rapid development of video game industry. The commentary ends by considering the distinction between online and offline video gaming and the critical consideration of everyday behaviors as being addictive.
Energetics of Interstitial Hydrogen and Hydrogen Diffusion in Realistic Models of a-Si:H
Authors: Fedders P. A.
Published: March 2017

In order to determine the mechanism or mechanisms of hydrogen transport in a-Si:H one must identify the reactions that bring deeply bonded H (on dangling bonds) to the transport band which is some form of interstitial hydrogen. Further, one must have reliable estimates of the energy difference between these deep states and transport states as well as the barrier energies among transport sites. In this paper we consider all of these ingredients in order to partially explain how hydrogen migrates in a-Si:H.
High Hydrogen Content Silicon Nitride For Photovoltaic Applications Deposited By Hot-Wire Chemical Vapor Deposition
Authors: Holt Jason K. , Swiatek Maribeth , Goodwin David G. , Atwater Harry A. , Watson Thomas J.
Published: March 2017

Silicon nitride films have been grown by hot-wire chemical vapor deposition and film properties have been characterized as a function of SiH4/NH3 flow ratio. Quadrupole mass spectrometry measurements revealed that NH3 should be present in large excess relative to SiH4 (<10), due to its lower decomposition probability on the wire. Silicon nitride films were produced with refractive indices ranging from 1.8-2.5 and H-content from 9-18 atomic % as the flow ratio increased from 1% to 8%. Fourier Transform Infrared Spectroscopy revealed a change from predominantly N-H to Si-H bonding as the flow ratio increases beyond 6%. Subsequent annealing studies showed different kinetics for H release from Si versus N. Films grown with a low SiH4/NH3 ratio were found to oxidize readily (23 atomic %), while larger ratios yielded no oxygen incorporation.
H NMR Evidence for a Change in The Local Hydrogen Environment of Sites Associated with the Staebler-Wronski Effect in a-Si:H
Authors: Su T. , Plachy Robin , Taylor P. C. , Stone S. , Ganguly G. , Carlson D. E.
Published: March 2017

We study the H NMR line shapes of a sample of a-Si:H under several conditions: 1) as grown, 2) light-soaked for 600 hours, and 3) light-soaked followed by annealing at different temperatures. At T = 7 K, the NMR line shape of the sample after light soaking exhibits an additional doublet compared to that of the sample as-grown. This doublet is an indication of a closely separated hydrogen pair. The distance between the two hydrogen atoms is estimated to be about (2.3 ± 0.2) Å. The concentration of these hydrogen sites is estimated to be between 1017 and 1018 cm-3 consistent with ESR measurements of the defect density after light soaking. This doublet disappears after the sample is annealed at 200°C for 4 hours.
Thin Film Microelectromechanical Systems
Authors: Chu V. , Gaspar J. , Conde J.P.
Published: March 2017

This paper presents the fabrication and characterization of MEMS structures on glass substrates using thin film silicon technology and surface micromachining. The technology developed to process bridge and cantilever structures as well as the electromechanical characterization of these structures is discussed. This technology can enable the expansion of MEMS to applications requiring large area and/or flexible substrates. The main results for the characterization of the movement of the structures are as follows: (1) in the quasi-DC regime and at low applied voltages, the response is linear with the applied dc voltage. Using an electromechanical model which takes into account the constituent materials and geometry of the bilayer, it is possible to extract the deflection of the structures. This estimate suggests that it is possible to control the actuation of these structures to deflections on the sub-nanometric scale; (2) resonance frequencies of up to 20 MHz have been measured on hydrogenated amorphous silicon (a-Si:H) bridge structures with quality factors (Q) of 70-100 in air. The frequency depends inversely on the square of the structure length, as predicted by the mechanical model; and (3) using an integrated permanent magnet/magnetic sensor system, it is possible to measure the structure movement on-chip and to obtain an absolute calibration of the deflection of the structures.
Carrier Generation in Thin-Film Polysilicon
Authors: Eccleston W.
Published: March 2017

There is a need to understand carrier generation polysilicon TFTs. When the generation is stimulated by the depletion of the material, due to the field effect, carriers are drawn to the surface and move along it by a process akin to diffusion. At some gate voltage the supply of carriers to the channel is insufficient to maintain the current flow. This leads to a reverse bias across the drain junction. It is proposed that carrier generation that occurs mainly near to the drain is more likely to be stimulated by increases of drain rather than gate voltage. The temperature dependence of currents at the current minimum, and at current saturation, of the transfer characteristic are described and are used to justify the model for generation and flow.
Experimental investigation and modelling of light scattering in a-Si:H solar cells deposited on glass/ZnO:Al substrates
Authors: Krc J. , Zeman M. , Kluth O. , Smole F. , Topic M.
Published: March 2017

The descriptive scattering parameters, haze and angular distribution functions of textured ZnO:Al transparent conductive oxides with different surface roughness are measured. An approach to determine the scattering parameters of all internal interfaces in p-i-n a-Si:H solar cells deposited on the glass/ZnO:Al substrates is presented. Using the determined scattering parameters as the input parameters of the optical model, a good agreement between the measured and simulated quantum efficiencies of the p-i-n a-Si:H solar cells with different interface roughness is achieved.
Light-intensity and temperature dependence of trap-dangling bond recombination in hydrogenated microcrystalline silicon
Authors: Boehme Christoph , Lips Klaus
Published: March 2017

A quantitative study of the trap-dangling bond tunneling recombination in hydrogenated microcrystalline silicon (μc-Si:H) is presented. The transition coefficients were measured at various light exposures and temperatures between T = 10 K and T = 140 K using time-domain measurements of spin-dependent recombination (TSR). TSR is a new characterization method related to electrically detected magnetic resonance (EDMR). It combines the advantages of pulsed electron spin resonance with that of EDMR. In contrast to previous models, the experimental results can only be interpreted if the interaction between the spins of the trap and the dangling bonds as well as triplet recombination is considered.
Real Time Spectroscopic Ellipsometry of Amorphous Silicon Grown at High Deposition Rates by Hot-Wire CVD
Authors: Nelson Brent P. , Levi Dean H.
Published: March 2017

We use real-time spectroscopic ellipsometry (RTSE) for in-situ characterization of the optical properties and surface roughness (Rs) of hydrogenated amorphous silicon (a-Si:H) grown by hot-wire chemical vapor deposition (HWCVD) with varying deposition rates (5 to 120 Å/s). Early time evolution of the Rs during growth is remarkably similar for all deposition rates. During the first few Ås of growth, there is a sharp increase in Rs as the a-Si:H nucleates in separate islands. This is followed by a reduction of Rs as these areas coalesce into a bulk film, which occurs at an average thickness of 100 Å. After coalescence the Rs rises to a stable value that is dependent upon growth conditions with a general tendency for the Rs to increase with growth rate. However, neither the Rs nor the material electronic properties are unique for a given deposition rate. Films grown under high silane flow and low pressure have a better photoresponse and a lower Rs than films grown at the same deposition rate but with low silane flow and high pressure. We observe a stronger correlation of film properties with Rs than with deposition rate; namely a monotonic decrease in photo-response, and increase in optical gap, with increasing Rs.
Recent Progress in Industrial Applications of CAT-CVD (Hot-Wire Cvd)
Authors: Masuda Atsushi , Izumi Akira , Umemoto Hironobu , Matsumura Hideki
Published: March 2017

Rapid progresses are achieved in catalytic CVD (Cat-CVD), often called hot-wire CVD, in the past 3-years NEDO national project in Japan. Cat-CVD technology presents many advantages in thin-film formation processes; high-efficiency of gas use, large-area deposition, no ion bombardment and low-temperature deposition even below 200°C. All of the elemental techniques for the industrially applicable Cat-CVD apparatuses, such as the suppression of the metal contamination, the precise control of the substrate temperature, the life extension of the catalyzer, 1-m size uniform deposition and the chamber cleaning, have been completely developed. Sophisticatedly designed substrate holder with electrostatic chuck and showerhead equipped with catalyzers are both key technologies for these achievements. High reproducibility for film properties is also obtained by controlling the reaction between high-density radicals and chamber walls. Prototype mass-production apparatus for SiNx passivation films in GaAs devices has been already developed and this will be probably the first application of Cat-CVD in industry. These recent movements appear to promise the drastic revolution in semiconductor and flat-panel display industries by introducing Cat-CVD in very near future.
Amorphous Silicon Films and Superlattices Grown by Molecular Beam Epitaxy: An Optical Analysis
Authors: Lockwood D. J. , Baribeau J.-M. , Noël M. , Zwinkels J. C. , Fogal B. J. , Orapunt F. , O'leary S. K.
Published: March 2017

We produce a novel form of amorphous silicon through ultra-high-vacuum molecular beam epitaxy. By depositing silicon atoms onto a fused quartz substrate at temperatures between 98 and 335°C, we obtain a silicon-based material that lacks the characteristic periodicity of crystalline silicon but nevertheless has 98% of its density. The impurity content of this material is studied through infrared and secondary ion mass spectroscopies. The primary impurity found is oxygen, with hydrogen and carbon atoms also being found at trace levels. The Raman spectra of the amorphous silicon films are measured and the results, as they relate to the presence of disorder, are interpreted. We also use this molecular beam epitaxy method to fabricate a number of amorphous silicon superlattices, comprised of thin layers of amorphous silicon separated with even thinner layers of SiO2. The optical properties of the films and superlattices are contrasted.
Microwave PECVD of Micro-Crystalline Silicon
Authors: Soppe Wim , Devilee Camile , Schiermeier Sacha , Donker Harry , Rath J.K.
Published: March 2017

The deposition of micro-crystalline silicon by means of PECVD with a new linear microwave plasma source is investigated. This plasma source has successfully been introduced in the large scale production of multi-crystalline Si solar cells for the deposition of passivating silicon nitride layers. Advantages of this linear plasma source are the high deposition rates and the large area (up to 80 cm width, no length limitations) on which a homogeneous deposition can be achieved. Since this source has not been applied for deposition of micro-crystalline silicon before, we explored a large parameter space (substrate temperature, pressure, MW-power, gas flow rates), in order to find optimum growth conditions. It is observed that with this microwave source it is possible to grow micro-crystalline layers at significantly higher silane/hydrogen ratios and higher deposition rates than for conventional RF PECVD. In this paper, structural properties of the silicon layers, as investigated by Raman and FTIR spectroscopy, XRD and SEM measurements are discussed.
Ultrafast Carrier Thermalization in Hydrogenated Amorphous Silicon
Authors: Dexheimer S. L. , Zhang C. P. , Liu J. , Young J. E. , Nelson B. P.
Published: March 2017

We present detailed studies of the initial relaxation processes of photoexcited carriers in hydrogenated amorphous silicon. We have carried out time-resolved measurements of the photoexcited carrier response in HWCVD a-Si:H thin films using a wavelength-resolved femtosecond pump-probe technique, in which an intense 35-fs pump pulse excites carriers in the sample and a time-delayed probe pulse measures the resulting change in optical properties as a function of time delay following the pump pulse. Measurements of the transient optical absorbance were carried out as a function of the density of excited carriers, sample temperature, and probe wavelength. These studies indicate fast carrier thermalization via phonon emission on a ∼ 150 fs time scale and rapid phonon equilibration on a ∼ 230 fs time scale.
Recombination of Optically Excited Carriers in a-Si:H at Low temperatures and Intermediate Times
Authors: Whitaker J. , Su T. , Taylor P. C.
Published: March 2017

Optically induced electron spin resonance (LESR) studies on time scales in between the previously published PL and LESR results (approximately 10 ms to 10 s) allow one to examine the cross over between energy-loss (downward) hopping of carriers and carrier recombination via tunneling. In addition, data in this time regime are directly compared in the same sample with NMR data on the dipolar spin-lattice relaxation of the bonded hydrogen where light induced electrons and holes are responsible for dipolar relaxation of bonded hydrogen. The LESR results confirm the interpretation of the NMR measurements.
Structural and Electrical Characterization of B-Doped Microcrystalline Silicon thin Films
Authors: Saleh R. , Nickel N. H.
Published: March 2017

In this paper we present the results for boron-doped microcrystalline silicon deposited at low temperature (230°C) by PECVD method. The structural and electrical properties are investigated as a function of boron concentrations using Raman, dark conductivity, hydrogen effusion and Hall effect measurements. The results show that the incorporation of boron induced an amorphization in the μc-Si:H films structure. A structural change due to boron incorporation is also accompanied by a change in hydrogen bonding environment. High conductive film of our boron-doped μc-Si:H films is attained at boron concentration 2000 ppm which consists nearly the same fraction of crystalline and amorphous phase (XC ~55 %).
Study of Amorphous to Microcrystalline Silicon Transition from Argon Diluted Silane
Authors: Gupta N. Dutta , Ray P. P. , Chaudhuri P. , Das U. K. , Vignoli S. , Jardin C.
Published: March 2017

We have studied the structural evolution in amorphous and microcrystalline silicon deposited from silane-argon mixture by radio frequency plasma enhanced chemical vapour deposition (PECVD) method. Sharp increase in small angle x-ray scattering (SAXS) intensity, in accordance with tilt measurements, indicates columnar morphology in the sample deposited in the amorphous-microcrystalline transition region. The variation of SAXS measured heterogeneity and a gradual shift of Si-H stretching vibrational frequency at 2000 cm-1 towards higher wave number with increase of power density indicate structural modifications in the films. Observation of sharp increase in the ratio of the intensity of Ar* to SiH* in the transition region may explain the surface modification assisted by Ar* and hence the structural changes in the material.
Electron Spin Resonance and Electronic Conductivity in Moderately Doped n-type Microcrystalline Silicon as a Probe for the Density of Gap States
Authors: Dylla T. , Carius R. , Finger F.
Published: March 2017

Electron spin resonance accompanied by conductivity measurements in n-type microcrystalline silicon with different doping concentrations and different structure compositions has been applied for the study of the density of gap states and the influence of these states on charge carrier density. We studied doping concentrations close to the defect density where the doping induced Fermi level (EF) shift is determined by compensation of gap states. We found a correlation between the EF shift, the intrinsic defect density and structural changes.
Metal-Free Germanium-Induced Crystallization of Amorphous-Si on Glass
Authors: Akhavan A. , Rezaee L. , Derakhshandeh J. , Mohajerzadeh S. , Goodarzi A.
Published: March 2017

A metal-free germanium-induced crystallization technique is reported to realize poly-silicon films on glass at temperatures as low as 480°C. The reduction in crystallization temperature is achieved by using ultra-violet illumination during thermal treatment of the amorphous silicon layer. The annealed samples have been studied using SEM and XRD analyses. Also the electrical conductivity of samples with various annealing conditions has been examined. Conductivity of the samples annealed in the presence of ultra-violet exposure shows more than three orders of magnitude improvement compared to that of amorphous films. Samples treated without UV exposure do not show much enhancement. Size of poly-silicon grains is 0.3μm, as revealed using SEM study.
Proton NMR Hole-Burning in Hot Wire a-Si:H
Authors: Herberg J. , Fedders P. A. , Leopold D. J. , Norberg R. E. , Schropp R. E. I.
Published: March 2017

Proton NMR near 200 MHz has been used to examine the dynamics of hole-burning in HWCVD a-Si:H films deposited from SiH4. Radiofrequency hole-burning is a tool to distinguish inhomogeneous broadening from homogeneous broadening. The 3 kHz FWHM resonance line from T-site-trapped H2 molecules shows a hole-burn behavior similar to that found for PECVD a-Si:H films, as does the 24 kHz FWHM line from clustered silicon-bonded hydrogens. However the ∼80 kHz FWHM superbroad line varies with tip angle uniformly across the line for hole-burns applied at any location within ∼50 kHz from the resonance center. The superbroad line is homogeneously broadened and apparently arises from superclose SiH clusters with inter-proton distances considerably less than 2 Å.
Correlation of Light-induced Enhancement of Open-Circuit Voltage and Structural Change of Heterogeneous Silicon Solar Cells
Authors: Yang Jeffrey , Lord Kenneth , Yan Baojie , Banerjee Arindam , Guha Subhendu , Han Daxing , Wang Keda
Published: March 2017

We observe a significant light-induced increase in the open-circuit voltage, Voc, of thin-film silicon solar cells whose intrinsic (i) layer consists of an amorphous and microcrystalline mixed phase. The increase depends on the i-layer thickness, the i-layer deposition temperature, the initial Voc values, and the light-soaking intensity. An increase of as large as 150 mV is observed. The original Voc is restored after subsequent thermal annealing. In-situ photoluminescence (PL) spectroscopy is used to investigate this metastable phenomenon. We find that the PL intensity and peak-energy position associated with the amorphous component of the heterogeneous material increase upon light soaking, suggesting a structural change. We propose that a reduction of microcrystalline volume fraction or size is responsible for the Voc enhancement.
Hydrogenated Microcrystalline Silicon Solar Cells Made with Modified Very-High-Frequency Glow Discharge
Authors: Yan Baojie , Lord Kenneth , Yang Jeffrey , Guha Subhendu , Smeets Jozef , Jacquet Jean-Marie
Published: March 2017

Hydrogenated microcrystalline silicon (μc-Si:H) solar cells are made using modified veryhigh-frequency (MVHF) glow discharge at deposition rates ∼3-5 Å/s. We find that the solar cells made under certain conditions show degradation in air without intentional light soaking. The short-circuit current drops significantly within a few days after deposition, and then stabilizes. We believe that post-deposition oxygen diffusion along the grain boundaries or cracks is the origin of the ambient degradation. By optimizing the deposition conditions, we have found a plasma regime in which the μc-Si:H solar cells do not show such ambient degradation. The best a-Si:H/μc-Si:H double-junction solar cell has an initial active-area efficiency of 10.9% and is stable against the ambient degradation. The stability data of the solar cells after light soaking are also presented.
A Study of Fabrication and Characterization of Ultra-Small Polycrystalline Silicon Islands for Advanced Display and Microsensor Applications
Authors: Schmidt Dominik , Shi Frank , Pianetta Piero
Published: March 2017

Polycrystalline silicon (polysilicon) is a key component of integrated circuit technology, micromechanical systems and displays. High-mobility polysilicon thin-film transistors are replacing amorphous-silicon transistors in advanced active-matrix displays, and are also vital to the emerging fields of microsensors and microactuators [1]. In this study, the deposition processes (LPCVD) of polysilicon thin films were carefully studied and the basic kinetics were analyzed. The films were patterned into submicron islands and the relation of the deposition temperature versus the crystallinity of polysilicon islands was observed. A “threshold” deposition temperature for polysilicon crystals larger than 0.35 μm was found. The relationships of polysilicon crystal sizes vs. annealing temperature and vs. annealing duration were also systematically studied. Polysilicon islands of ∼ 0.1 μm lateral dimensions were successfully fabricated by ebeam lithography and several types of annealings were performed to increase micro-crystal size, with the goal of creating single-crystal high-mobility islands. Theoretically, transistors built from such islands should match the performance of state-of-the-art bulk CMOS devices. The crystal size was measured using TEM and AFM analysis. Moreover, EXAFS (Extended X-ray Absorption Fine Structure) measurements at SSRL (Stanford Synchrotron Radiation Lab) were employed to study the crystallization processes of polysilicon films and the correlation between the absorption curves, the thin-film electrical properties and the polysilicon grain sizes.
Infrared Charge-Modulation Spectroscopy of Defects in Phosphorus Doped Amorphous Silicon
Authors: Zhu Kai , Schiff E. A. , Ganguly G.
Published: March 2017

We present infrared charge-modulation absorption spectra on phosphorus-doped amorphous silicon (a-Si:H:P) with doping levels between 0.17%-5%. At higher doping levels (1% - 5%) we find a sharp spectral line near 0.75 eV with a width of 0.1 eV. We attribute this line to the internal optical transitions of a complex incorporating four fold coordinated phosphorus and a dangling bond. This line is barely detectable in samples with lower doping levels (below 1%). In these samples a much broader line dominates the spectrum that we attribute to uncomplexed dopants. The relative strength of the two spectral features is in rough agreement with a model proposed by Street that has not been previously tested experimentally.
Optical Properties of i-Layers as a Function of Growth Rate in Correlation to the Performance of a-Si:H Solar Cells
Authors: Wang Keda , Owens Jessica M. , Weinberg-Wolf Jennifer , Han Daxing , Gedvilas Lynn
Published: March 2017

a-Si:H intrinsic films and their solar cells were prepared by DC-PECVD with growth rates of 1, 3, and 10 Å/s. Raman, IR, and PL spectroscopies were used to study the i-layer properties in relation to the solar cell performance. Raman shows an identical TO mode for all the samples, which indicates the local silicon-bonding configuration does not change with the growth rate from 1 to 10 Å/s. IR results show that the hydrogen bonding configuration is monohydride (Si-H) dominated, and the hydrogen content obtained from the 630 cm-1 wagging mode is 12-14 at.%. Surprisingly, a very small absorption strength for the stretching 2000-2100 cm-1 mode was found for some samples deposited at the higher growth rates (3, 10 Å/s). For these same samples, the PL spectra exhibit a red shift. Both the IR and PL results might be related to the same microstructures formed at high growth rates. We found that although the properties of the i-layer varied as the growth rate increased from 1 to 10 Å/s, the performances of the cells were comparable (within about 4%).
Influence of ZnO/p+a-Si:H Microcrystallization and Antireflection Coatings on pin a-Si:H Solar Cells Performance
Authors: Kolodziej Andrzej , Krewniak Pawel , Nowak Stanislaw
Published: March 2017

In general terms this paper analyzes effectiveness of ZnO/p+/i a-Si:H/n+/Al solar cells made on commercial glass substrate with double-sided antireflection coatings. The primary topic, however, is the ZnO/p+/i a-Si:H junction based on layers obtained by the reactive magnetron sputtering (RMS) of Si:B, Si:P, Al, Zn:Al targets, where the “i” layer is a protocrystalline RFCVD layer. These single layers, as well as the respective structures, were studied using primarily Grazing Incidence X Ray Analyzes and AFM spectroscopy. In particular, the microcrystallization, surface roughness and chemical composition of the films were studied with respect to film thickness, RMS power and hydrogen dilution. The nature of the influence of ZnO/p+/i a-Si:H crystallization on pin a-Si:H solar cells performance is presented. Optical transmission and reflection measurements were used to measure the light flux reaching the “i” layer. We determined the experimentally observed angular distribution of scattered light in transmittance through glass/ZnO:Al/p+ silicon and double antireflection coatings on glass/ ZnO:Al/p+ silicon junctions. The optoelectronic properties of glass/ZnO/pin a-Si:H/Cr/Al cells are examined by systematic investigation of their I-V characteristics subsequent to steady-state conditions.
TFA Image Sensors for Low Light Level Detection
Authors: Sterzel Jürgen , Blecher Frank , Hillebrand Matthias , Schneider Bernd , Böhm Markus
Published: March 2017

TFA technology, using ASICs coated with amorphous silicon based photo detectors, opens new applications for CMOS image sensors. One particular field of interest is the detection of low light level images with pixel photocurrents in the femtoampere range and below. In this paper we describe the effects of the capacitances on the pixel amplifier, we derive noise values for the detector and the amplifier, and we estimate the gain fixed pattern noise level. An inverter circuit providing a 40-fold increase of the charge conversion gain is presented.
Analysis of the Bias Dependent Spectral Response of a-SiC:H p-i-n Photodiode
Authors: Louro P. , Fantoni A. , Vygranenko Yu. , Fernandes M. , Vieira M.
Published: March 2017

The bias voltage dependent spectral response (with and without steady state bias light) and the current voltage dependence has been simulated and compared to experimentally obtained values. Results show that in the heterostructures the bias voltage influences differently the field and the diffusion part of the photocurrent. The interchange between primary and secondary photocurrent (i. e. between generator and load device operation) is explained by the interaction of the field and the diffusion components of the photocurrent. A field reversal that depends on the light bias conditions (wavelength and intensity) explains the photocurrent reversal. The field reversal leads to the collapse of the diode regime (primary photocurrent) launches surface recombination at the p-i and i-n interfaces which is responsible for a double-injection regime (secondary photocurrent). Considerations about conduction band offsets, electrical field profiles and inversion layers will be taken into account to explain the optical and voltage bias dependence of the spectral response.