bluuebunny/crossref_metadata_2025 huggingface dataset:
La politique communautaire du tourisme dans la zone CEMAC. Une analyse à la lumière des enjeux de l’intégration sous-régionale (2001-2012)
Authors: Dang A Goufan Paul Derrick
Published: June 2023

L’objectif de la présente réflexion est d’étudier la politique communautaire du tourisme dans la zone CEMAC (Communauté économique et monétaire de l’Afrique centrale) afin de faire ressortir son rôle dans le processus d’intégration sous-régionale. Cette vision touristique commune se déploie autour de trois piliers fondamentaux : la Commission permanente du tourisme de la CEMAC ; l’École de l’hôtellerie et du tourisme de la CEMAC ; et le Conseil des ministres du Tourisme de la zone CEMAC. Pour étayer notre propos, nous avons eu recours à une méthodologie qui repose essentiellement sur la collecte et l’analyse de documents d’archives, d’ouvrages, de travaux académiques, de rapports et d’entretiens directifs en lien avec le tourisme et l’intégration sous-régionale dans cette zone. L’ancrage disciplinaire est celui de la tourismologie au sens de Jean-Michel Hoerner (sciences du tourisme) et de l’histoire des relations internationales. Au-delà des insuffisances (absence d’une réelle volonté politique, moyens financiers limités et problématique des ressources humaines dans le secteur touristique) qui démontrent que le tourisme demeure un souci annexe, cette vision communautaire du tourisme apparaît comme un atout pour parachever le processus d’intégration sous-régionale en zone CEMAC. Suite à la crise sanitaire du Covid-19, dont les effets s’estompent progressivement, cette étude propose également des éléments nouveaux afin d’assurer une meilleure relance de l’activité touristique dans l’espace CEMAC.
The Dynamics of the Relationship Between Price and Volume of Cryptocurrencies
Authors: Chaâbane Najeh , Elmalki Anas
Published: June 2023

In this study, the authors investigate the volume as the pricing driver of the top three cryptocurrencies (Bitcoin, Ethereum, and Binance) based on a wavelet analysis from January 1, 2019 to December 31, 2021. The dynamics of the relationship between price and volume in the cryptocurrency market could have valuable market implications for stakeholders and investors and contribute to making optimal investment decisions via portfolio diversification strategies. The results reveal that the relationship between price and volume is positive in the medium and long term and that price is the leading volume for both Bitcoin and Binance markets. The findings suggest that the COVID-19 pandemic significantly affected the cryptocurrency price and volume series links. Indeed, these results contribute to the emerging and growing literature on cryptocurrencies in the time of COVID-19, which has received limited attention during the pandemic compared to the classical asset financial classes.
Brain-Machine Interface and Blockchain in Avatar-Based Systems
Authors: Galiautdinov Rinat
Published: June 2023

The main purpose of this research is to provide a solution that allows neuroscientists and developers to keep the track of the neurosignals of live beings or biologically simulated neural networks and store them having the ability to guarantee that output of neurosignal translation was correct and can be reproduced later on any other biologically simulated neuron. Such a situation is especially important for the case when producers of different equipment, which are based on the biologically simulated neurons, can predict its behavior and guarantee that it will have accepted level of output deviations. Such a situation can be used for tracking live neurosignals of a beings and then reproduce them on avatars or different types of robots, neural networks, etc.
Positive Leadership and the Quiet Quitting Movement in Organizations
Authors: Joaquim Ana Filipa Vieira Lopes , Nunes Figueiredo Paula Cristina , Silva Vasco Rafael Costa , Nogueira da Fonseca Cristina
Published: June 2023

This chapter seeks to highlight the importance of positive leadership in combating the phenomenon of quiet quitting. This phenomenon is not new, but it has gone viral with the COVID-19 pandemic, being more 'visible' in the organizational context. Thus, the objective of this research is to identify the main advantages of positive leadership in mitigating the quiet quitting movement. The research methodology is qualitative and starts by conceptualizing and identifying the main causes and consequences of the quiet quitting movement. Afterwards, the advantages of positive leadership are identified and, finally, this leadership style is systematized in relation to happiness and well-being at work. This research thus integrates the positive leadership approach with practices to improve employee engagement and organizational culture, highlighting the importance of human resource management practices to attract, integrate and manage talent in companies.
Women in School Leadership in India and the United States
Authors: Saxena Adity , Akil Monique Darrisaw , Ayinampudi Pavani
Published: June 2023

Women's representation in school leadership positions in India, and of Black women in the United States, remains unexplored. This chapter addresses the realities and complexities of women leaders in school education and develops a narrative based on current trends and anticipated challenges for the future. Existing research in educational leadership in schools, case studies, and interviews tend to focus on developing a coherent understanding of the topic. The representation of women in the school, from teachers to leaders, is an inverted pyramid. This chapter aims to provide an overview of how women school leaders from India and the USA manage crises, navigate politics, establish policies and budgets, and where the constraints lie at the school board and family level. Finally, using the grounded theory framework, the authors will present a pattern of women's leadership similarities, differences, and uniqueness in the context of both countries.
Trade Union Leadership and Sustainability in the Contemporary World of Work
Authors: Tinuoye Adekunle Theophilius
Published: June 2023

The industrial revolution resulted in a conflict of interest between the employer and employee and the emergence of trade unions. By contributing to harmonizing workplace interests, formulating rules governing workplace relations, and protecting workers' rights and welfare, the imprimatur of trade unions are manifest in every facet of global socio-economic and political progress. However, certain developments, practices, and trends have served to weaken the labor movement and brought to the fore germane questions about the utility of trade unions; and it is against this background, that the ethos of unity, cohesion, and solidarity and backed by sound, pragmatic, and ethical leadership should be utilized in their quest to continue to organize, mobilize, and strategize to champion the cause of the working class. Therefore, this chapter would focus on the above themes and proffer leadership strategies for the continued relevance of trade unions as institutions for servicing worker needs in eras of uncertainty.
The Dark Side of Leadership
Authors: Gaur Bhawna
Published: June 2023

Personality traits favored by situational factors may lead to destructive tendencies in a good leader. For example, CEOs such as Larry Page of Google, Lloyd Blankfein of Goldman Sachs, Mark Zuckerberg of Facebook, and Elon Musk of Tesla have exhibited a shift from constructive to destructive leadership style due to situational or environmental factors. Destructive or dark leadership style is associated with personality traits such as narcissism, Machiavellianism, and psychopathy. This chapter introduces the concept of personality disorders that might threaten the effectiveness of an individual as a leader. It will further discuss the factors that contribute to the development of destructive personalities and different types of destructive personalities. This chapter will identify the role of followers and environment that provide legitimacy for immoral actions. It will provide solutions to improve leadership practices to reduce toxicity in the work environment and create a positive workplace.
Leadership in a VUCA World
Authors: Bindra Bhavika , Kapoor Shikha
Published: June 2023

This chapter expands on all of the preceding material by focusing on a leader's capacity to formulate and convey leadership in uncertain times. As the world has become “VUCA”—volatile, unpredictable, complex, and ambiguous—there are no hard and fast rules for operating enterprises in the 2020s. The hierarchical organization paradigm is dead in the VUCA environment, and other models are developing, but there is no dominant model that works for everyone. New times necessitate new regulations, but there is no universal norm that applies to every sector and scenario. Leaders have been walking a tightrope for the last two years, attempting to maintain stability while coping with a disruptive and unpredictable pandemic, failing to hire despite a 15-year high in talent shortages, and revising policies to suit employee expectations for more flexibility at work. Multiple waves of coronavirus variations have put executives in a difficult position: trying to comfort and focus people in the face of ongoing uncertainty while having no idea what will happen next.
Undergraduate Business Students' Perceptions About Virtual and Remote-Work Leadership Skills
Authors: Al-Fattal Anas , Walker II Eddie G. , Lundbohm Rachel
Published: June 2023

With changes introduced to the work environment since the COVID-19 pandemic, an ever-increasing amount of interest has been focused on virtual leadership. This chapter researches the topic of virtual leadership and focuses on investigating business students' perceptions of skills relevant to virtual leadership positions. The chapter presents an empirical exploratory research study conducted through four focus groups with 20 undergraduate business students. The findings reveal business students have a relevant understanding of the differences between traditional and virtual work environments. Socialization and isolation are among the most dominant themes regarding the differences in work modes. The findings also show that business students understand the challenges associated with leading in virtual and remote work settings, and they prefer traditional future leadership positions to avoid such challenges. The study highlights several relevant leadership skills needed according to business students such as communication, the ability to engage, and technological competencies.
Expanding and Updating Human Rights
Authors: Pimentel Thiago Duarte , Chaves Pimentel Mariana Pereira , de Oliveira Marcela Costa Bifano , Vieira João Paulo Louzada , Cerqueira Paulo Rodrigues
Published: June 2023

This chapter argues that tourism should be included as a social right because it synthesizes and represents the zeitgeist of contemporaneity. This idea is supported by three main arguments: (1) That there is a shift from a work-oriented society to a new consumption-oriented one, implying the revision of the meaning of current practices. (2) As a social force, tourism is a privileged category to represent, understand, and explain contemporary societies because it goes beyond the market and can heuristically express a complex and multifaceted human practice. (3) The references based on the previous societies' ideals, such as the right to work, must be revised and expanded to include tourism as a fundamental right, because (a) it can internationally represent a new kind of global citizenship, (b) basic material and economic human needs must be met for tourism to happen, and (c) it contributes to personal development, cultural exchange, and systemically update societies' development.
Human Rights and Workforce Conditions in the Tourism Sector
Authors: Khassawneh Osama , Hashmi Zeynep Gulen
Published: June 2023

In this chapter, the focus is on the various challenges related to workforce conditions in the tourism industry and how human rights can play a role in alleviating these challenges. The chapter draws from a review of literature and offers a global perspective. Topics covered include the treatment of employees in the tourism sector, adherence to human rights and labor standards in the industry, the prevalence of mandatory and forced labor, collective bargaining, the use of child labor, fair treatment for all workers, and employee discrimination. The chapter will feature examples from different countries and conclude with recommendations for improvement.
Temperature Dependence of the Channel and Drift Resistance of SiC Power MOSFETs Extracted from I-V and C-V Measurements
Authors: Stark Roger , Tsibizov Alexander , Race Salvatore , Ziemann Thomas , Kovacevic-Badstuebner Ivana , Grossner Ulrike
Published: June 2023

SiC power MOSFETs show very promising electrical performance for efficient and reliable high temperature operation. This work presents a novel approach for the determination of the temperature dependence of SiC power MOSFET’s channel and drift resistance components in the on-state, which are extracted based on current-voltage (I-V) and capacitance-voltage (C-V) measurements without the need of data extrapolation. The results show that the channel resistance has weak, whereas the drift resistance has strong temperature dependence.
Implementation of Large Scale Deep Learning Non-Destructive Methods for Characterizing 4H-SiC Materials
Authors: Leonard Robert , Conrad Matthew , van Brunt Edward , Witry Jason , Balkas Elif
Published: June 2023

A whole wafer method for industrial high volume, non-destructive characterizing of extended defects is demonstrated for 150 mm and 200 mm 4H-SiC wafers. Deep learning (DL) coupled with non-destructive techniques (NDT, DL-NDT) involving high volume, fast optical microscopy methods correlates industry accepted chemistry and physics-based etch and diffraction techniques for defect characterization. The application of the DL-NDT method is shown to reproduce defect distributions achieved by accepted etch techniques for extended defects of threading dislocations (TD), basal plane dislocations (BPD), and threading screw dislocations (TSD). An example of algorithm development is described to show progress toward implementing the method, as well as DL-NDT defect density compared to etch density for multiple wafers. The development status for implementing this technique for large-scale industrial wafer production includes etch validation of the results to ensure the technique is consistent and reliable. The ability to use this non-destructive technique ultimately will result in better correlation with device behavior and provide feedback to crystal growth processes to improve substrate wafers, while reducing the need for etch methods.
650V Vertical SiC MOSFETs and Diodes with Improved Terrestrial-Neutron Single-Event Burnout
Authors: Lichtenwalner Daniel J. , Ganguly Satyaki , Fetzer Brian , Woods Callie , Gajewski Donald A. , Ryu Sei Hyung , Hull Brett , Allen Scott , Palmour John W.
Published: June 2023

Silicon carbide (SiC) power devices such as Schottky diodes and metal-oxide semiconductor field-effect transistors (MOSFETs) are susceptible to failure by terrestrial neutron single-event burnout (SEB) while in the high-voltage blocking state. In this study the effects of the drift layer design of 650V SiC vertical power diodes and MOSFETs have been studied. TCAD simulations of different device designs have been performed, and fabricated device single-event burnout (SEB) properties are compared between the devices fabricated. We find that the standard 650V devices have a low area-scaled failure-in-time (FIT/cm2) such that essentially no failures (0.01 FIT/cm2) are expected at 400V drain-source bias (VDS) operation and below. An improved design allows the SEB failure rate curve to be shifted downward in failure rate, such that at for a given VDS operation condition, the FIT/cm2 can be decreased by 10 - 100 times, depending on the VDS value. This allows operation at about 75V higher VDS value with a similar SEB failure rate, allowing these devices to be used in a wider range of applications.
Stacking Faults Originating from Star-Defects in 4H-SiC
Authors: El Hageali Sami , Mahadik Nadeem , Stahlbush Robert , Guthrey Harvey , Johnston Steven , Soto Jake , Odekirk Bruce , Gorman Brian , Al-Jassim Mowafak
Published: June 2023

Intense efforts are currently in progress to study various sources of basal plane dislocations (BPDs) in SiC epitaxial layers. BPDs can generate Shockley-type stacking faults (SSFs) in SiC epitaxial layers, which have been shown to be associated with the degradation of power devices. This study shows that the star-shaped defect can be a source of several BPDs in the epitaxial layer. We investigate the complex microstructure of the star defect, the generation of BPDs, and expansion of SSFs using various complementary microscopy and optical techniques. We show direct evidence that star-defects can be a nucleation point of single-SSFs that can expand at the core of the defect. Newly found secondary dislocation arrays extending over a few centimeters away are found to be emanating from the primary arms of the star defect. The presence of such dislocation walls and the expansion of single-SSFs will affect the yield of numerous die on a wafer. Further understanding of the formation mechanism of stacking faults generated from star-defects as provided in this study helps understand their effect on SiC-based devices, which is crucial to assess device reliability.
Cellulosic Textile Materials Functionalization with Formic Acid and Improvement of their Properties
Authors: Faria Joana , Padrão Jorge , Zille Andrea , Miranda Teresa
Published: June 2023

Formic acid, commonly used in bioprocesses of cellulosic polymeric materials, has been considered for the treatment of cellulose-based textile. Therefore, different concentrations of formic acid (10, 20, 30, 40, and 50 g L-1) were used to treat cotton (CO) and viscose (CV) fabrics to improve their properties. Weight variation, tensile strength, stiffness, drape coefficient, crease recovery angle, and vertical wicking of the treated substrates were assessed. Fourier transform infrared spectroscopy attenuated total reflection (FTIR-ATR) analysis confirmed the acid hydrolysis process of the cellulosic substrates treated with formic acid solutions. Formic acid solutions with concentrations equal to 30 g L-1 and 40 g L-1 are the most adequate to treat the CV and CO fabrics, respectively. In addition, the fabrics treated under optimal conditions were dyed with the reactive dye Levafix Blue CA. The dyeing properties were assessed through colour absorption coefficient and scattering coefficient (K/S) values. A clear improvement in the fastness and dyeing performance of the treated substrates was observed. Finally, the antibacterial properties of the treated substrates were evaluated, for the bacteria Escherichia coli and Staphylococcus aureus. It was found that only cotton substrates treated with a 40 g L-1 formic acid solution could be classified as weak decontaminants against S. aureus bacteria.
PVA Nanofibers Embedded with Different Concentration of ZnO Prepared by Electrospinning Method
Authors: Zulkefle Muhammad Alhadi , Rahman Rohanieza Abdul , Abdullah Wan Fazlida Hanim , Zulkifli Zurita , Herman Sukreen Hana
Published: June 2023

Polyvinyl alcohol (PVA) nanofibers were fabricated using the electrospinning method. The nanofibers were embedded with zinc oxide (ZnO) particles by mixing PVA liquid with the ZnO powders during the solution preparation stage. The FESEM images showed an increase in the amount of ZnO particles embedded in the PVA nanofibers as the powder content was increased. Other than that, there are no significant changes in other physical properties of the nanofibers caused by the increasing number of ZnO particle content. This means that ZnO nanopowders (with concentration in the range of 1.63 wt% - 8.14 wt%) can be effectively integrated and embedded into PVA nanofibers without negative consequences on the fibers formation and structure. This will facilitate the fabrication of ZnO embedded PVA nanofibers in some applications that may require it such as drug delivery, filtration, and biomedical application.
A Study on Coldflame Propagation Characteristics Applying Amplified Ignition Source to Overcome Landfill gas’s Flame Retardant Limit
Authors: Ryu Kyungjin , Choe Munseok
Published: June 2023

In this study combustion characteristics were analyzed with LFG, one of the alternative energy sources of SI engines. To overcome the flame retardant limit, which is the shortcoming of LFG, the combustion characteristics were analyzed using the AIS device that was created for this study’s purpose. A static combustion chamber to which AIS can be applied was designed for the experiment that was conducted on the coldflame propagation and combustion characteristics of each LFG fuel using C-type (conventional ignition type) and AIS devices. From the basic LFG experiment, it was identified that as the proportion of carbon dioxide in the fuel increased, the combustibility decreased, and the combustion pressure decreased. When using the AIS device to overcome the flame retardancy of LFG, the combustion pressure was increased by 2 bar even in LFG70 and LFG60, where combustion was actively occurring with the C-type and the combustibility was improved in LFG50 as well. In overall respects, it was judged that the use of AIS could overcome the flame retardancy of LFG and could incorporate LFG into SI engines.
In Situ Monitoring of the Ambient Gas Phase during PVT Growth of Nominally Undoped High Resistivity SiC Boules
Authors: Ihle Jonas , Wellmann Peter J.
Published: June 2023

The aim of this study is to show the applicability of continuous residual gas analysis for growth monitoring of undoped SiC with physical vapor transport (PVT). For this purpose, two crystals were grown, one without doping and one with continuous nitrogen doping. During the processes continuous residual gas analysis were conducted and evaluated with emphasis on the temporal variations of the nitrogen content. The charge carrier concentration of the final crystals was determined by optical methods (spectrally resolved absorption measurement with UV-VIS and Raman spectroscopy) and the results were compared with the residual gas analysis during growth. A correlation was found between the measured nitrogen-related signal and the charge carrier concentration in the samples.
Reduction of Forward Bias Degradation in 4H-SiC PiN Diodes Fabricated on 4H-SiC Bonded Substrates
Authors: Hatta Naoki , Ishikawa Seiji , Ozono Kunihide , Masumoto Keiko , Yagi Kuniaki , Kobayashi Motoki , Kurihara Shunsuke , Harada Shinsuke , Kojima Kazutoshi
Published: June 2023

The advantage in reducing forward bias degradation of bipolar 4H-SiC devices using a 4H-SiC bonded substrate is demonstrated. To evaluate the differences in forward bias degradation between a 4H-SiC bonded substrate and a commercially available 4H-SiC bulk substrate, a forward current stress test and subsequent photoluminescence (PL) imaging of PiN diodes fabricated on both the substrates were performed. Unlike the bulk substrate, the bonded substrate maintained a low ΔVf and the variation among the measured diodes was extremely small even after applying the highest current density of 1500 A/cm2. The investigated number of bar-shaped SSFs within the electrically stressed diodes with more than 1000 A/cm2 revealed the possibility that the BPDs existing at deep positions below the epilayer/substrate interface were drastically reduced in the 4H-SiC bonded substrate.
Investigation of Bulk Material Transportation by Screw Conveyer with Hinge-Pan Operating Device
Authors: Lyashuk Oleg , Rohatynskyi Roman , Hevko Ivan , Dmytriv Olena , Tson Oleg , Tkachenko Ihor , Sokol Mariana , Leshchuk Roman , Kobelnyk Volodymyr
Published: June 2023

The article presents a new design of a hinged and sectional working body and substantiates its optimal parameters for ensuring the movement of loose materials along curvilinear routes. Analytical dependencies have been derived to determine the rational design and power parameters of the hinged-sectional working body, and the functional dependencies of the minimum permissible radius of curvature of the RC technological highway on the angular rotation of adjacent sections and their design parameters have been established. The axial speed and power of cargo transportation by the articulated-sectional working body of the screw conveyor along a curved route have been determined. Experimental studies have been conducted to determine the influence of the number of revolutions, the height of material lifting and the radius of curvature of the flexible helical sectional working body RC on the torque T, as well as the determination of the influence of the number of revolutions n, the filling factor of the main line ψ and the diameter of the main line D on the performance Q when transporting loose materials.
Minority Carrier Traps Induced by Neutron Reactions with 4H-SiC
Authors: Belanche Guadas Manuel , Bathen Marianne Etzelmüller , Kumar Piyush , Dorfer Christian , Martinella Corinna , Grossner Ulrike
Published: June 2023

This work presents the characterization of minority carrier traps in epitaxial n-type 4H-SiC after high fluence neutron irradiation using minority carrier transient spectroscopy (MCTS) in a temperature range of 20 K to 660 K. Three minority carrier trap levels are reported, labelled as X, B and Y, whose activation energies were estimated by Arrhenius analysis and where the B level is assigned to substitutional boron (BSi). The dynamic behaviour of the trap levels was studied by consecutive temperature scans.
Thermal Effect of Bobbin Tool Friction Stir Welding on the Mechanical Behavior of High Density Polyethylene Sheets: Experimental Study
Authors: Kaou Abdellah , Bouha Djilali , Meddah Hadj Miloud , Ould Chikh El Bahri
Published: June 2023

Bobbin friction stir welding (BT-FSW) is a variant of the conventional friction stir welding (C-FSW). This method has been applied of welding high density polyethylene (HDPE) plates; where a rotating symmetrical tool causes a fully penetrated bond, it can weld the upper and lower surface of the work-piece in the same pass. BT-FSW process involves complex heat generation and HDPE flow, which directly affects on the weld area and on mechanical properties of welded joint. Heat generation and material flow during BT-FSW are significantly affected by the tool design features, process parameters and mechanical behavior of work piece materials. Studying the temperature of polyethylene sheets welded by BT-FSW can help in analyzing the mechanism of weld formation and also can provide theoretical guidance for the tool design, process parameter selection and even new process development. In the unique work described in this paper, the 11.4 mm-thick HDPE plates were welded successfully by bobbin-tool friction stir welding. Measurements of the material temperatures were performed by thermocouples which are placed near and at the weld seam. The weld quality was determined in terms of no defects in the stir zone and the tensile strength of the joint. It was found that considerable melting occurred between the rotating shoulders and on the trailing side of the rotating pin. Movement of the molten material by the rotating tool created a very black band in the stir zone. Thermocouples measurements indicated that the temperatures were higher on the advancing side (AS) compared to those on the retreating side (RS). Tensile tests and hardness measurements were performed on welded and seamless sheet samples. The results were analyzed to compare the mechanical properties. To demonstrate the variation in micromechanical properties between welded and seamless sheet samples, micro hardness (HV) testing was used to explain the difference. The HV of the HDPE plates weld by BT-FSW, were relatively symmetrical with respect to the parting line. The maximum hardness levels were reached in the weld bead at around 66 HV in the welded nugget; there was a rise in the level of hardness, in particular at retreating side (RS) and at advancing side (AS) where the value reached 68.60 HV.
Early Burn-In Parasitic Conduction in 500 °C Durable SiC JFET ICs
Authors: Neudeck Philip G. , Spry David J. , Lukco Dorothy , Chen Liang Yu
Published: June 2023

All prior reports of long-term 500 °C operation of SiC JFET-R ICs have noted the existence of an initial “burn-in” period of changes in measured electrical characteristics for the first few hundred hours oven-testing. This work reports measurements of “burn-in parasitic MOSFET conduction” that can substantially impact the performance of some circuits during initial heat-up of JFET ICs, but then subsequently disappears after a few hours of operation at 500 °C. The behavior appears generally consistent with the known MOS phenomenon of bias-temperature driven redistribution of mobile ionic contamination. Approaches for further mitigating this initial burn-in conduction mechanism are discussed.
Analysis of Strain in Ion Implanted 4H-SiC by Fringes Observed in Synchrotron X-Ray Topography
Authors: Chen Ze Yu , Liu Yafei , Peng Hong Yu , Cheng Qian Yu , Hu Shanshan , Raghothamachar Balaji , Dudley Michael , Ghandi Reza , Kennerly Stacey , Thieberger Peter
Published: June 2023

A novel high energy implantation system has been successfully developed to fabricate 4H-SiC superjunction devices for medium and high voltages via implantation of dopant atoms with multi-energy ranging from 13 to 66 MeV to depths up to 12um. Since the level of energies used is significantly higher than those employed for conventional implantation, lattice damage caused by such implantation must be characterized in detail to enhance the understanding of the nature of the damage. In regard to this, by employing the novel high energy system, 4H-SiC wafers with 12μm thick epilayers were blanket implanted by Al atoms at energies ranging from 13.8MeV to 65.7MeV and N atoms at energies ranging up to 42.99MeV. The lattice damages induced by the implantation were primarily characterized by Synchrotron X-ray Plane Wave Topography (SXPWT). 0008 topographs recorded from the samples are characterized by an intensity profile consisting of multiple asymmetric diffraction peaks with an angular separation of only 2” (arcseconds). Using Rocking-curve Analysis by Dynamical Simulation (RADS) program, diffracted intensity profile was used to extract the corresponding strain profile indicating an inhomogeneous strain distribution across the depth of the implanted layer.
Impact of Dimensions and Doping on the Breakdown Voltage of a Trench 4H-SiC Vertical JFET
Authors: Monaghan Finn , Martinez Antonio , Fisher Craig , Jennings Mike
Published: June 2023

In this paper we study the feasibility of the design/fabrication of a vertical trench 4H-SiC Junction Field Effect Transistor (JFET), assuming realistic constraints of the depth of the P+ implantation. The P+ doping profile is obtained using a Monte Carlo implantation simulation. The calculation used a drift-diffusion approach. The JFET aims to achieve a threshold voltage of-3V. We found that this constraint in concomitance with the proposed structure limits the breakdown voltage to approximately 200V. This is the result of a premature breakdown induced by short channel effects, namely Drain Induced Barrier Lowering (DIBL). However, a negative increase in the gate bias represses this short channel effect and improves the breakdown voltage to roughly 1800V. At this gate bias, the breakdown is induced by reaching the critical field strength of 4H-SiC at the gate P+/N junction, which causes avalanche generation of carriers. In addition, we have calculated the dependence of the threshold voltage on the drift doping and pillar width. This work also shows the vulnerability of the design to random fluctuation in the doping profile.
Power Cycling on Lateral GaN and β-Ga2O3 Transistors
Authors: Rugen Sarah , Brunko Alexander , Hoffmann Felix , Kaminski Nando
Published: June 2023

The load cycling capability of novel power semiconductors is an important aspect when estimating their lifetime in field service. The Power Cycling Test (PCT) is the standard test to evaluate the lifetime of a semiconductor device under thermo-mechanical stress. PCTs are typically performed at temperature swings (ΔT) much higher than common operating conditions, to obtain results within a reasonable time. In this work, the PCT capability of gallium nitride (GaN) and gallium oxide (Ga2O3) lateral transistors is investigated. The GaN devices were tested in two groups with different ΔT. The temperature of the devices was monitored using two different temperature sensitive electrical parameters (TSEPs) and the accuracy of both methods was evaluated by comparing the results with the temperature, monitored by using an infrared (IR) camera. For Ga2O3 devices, no data on potential TSEP exists so far, thus, the typical TSEP for silicon (Si), silicon carbide (SiC) and GaN were investigated for their applicability to Ga2O3 devices. While a PCT was conducted on the devices, the temperature was also monitored using an IR camera. The results of the comparison of TSEP and IR camera data showed, that the accuracy of the TSEP for GaN matched either the temperature of the hottest spot on the chip (VDS method), or the average chip temperature (VGS method). For the Ga2O3 devices no suitable TSEP could be obtained and only the IR camera was used for the temperature measurement. It revealed a very uneven temperature and thus, current distribution on the chip. Furthermore, both GaN and Ga2O3 devices exhibit an outstanding power cycling capability with no failure after completing several millions of cycles. Considering the difference in Young’s Modulus of Si, GaN and Ga2O3, the PCT performance of GaN on silicon devices and Ga2O3 devices should be inferior to silicon devices. Thus, both device types, the GaN transistors and the Ga2O3 transistors, showed a PCT capability much higher than expected.
Effective Penetration Depth Investigation for Frank Type Dislocation (Deflected TSDs/TMDs) on Grazing Incidence Synchrotron X-Ray Topographs of 4H-SiC Wafers
Authors: Cheng Qian Yu , Peng Hong Yu , Chen Ze Yu , Hu Shanshan , Liu Yafei , Raghothamachar Balaji , Dudley Michael
Published: June 2023

In 4H-SiC crystals, Frank type dislocations are created through the deflection of threading screw/mixed dislocations onto the basal plane. Grazing-incidence X-ray topographs are often used to evaluate the density of such dislocations and a knowledge of the effective penetration depth is therefore essential. In this study, a systematic analysis is performed to investigate the effective penetration depth, which is the depth from which contrast from the dislocation is still discernible. This is achieved by comparison between observed topographic images and detailed ray tracing simulations. Simulations shows no significant contrast difference between a deflected TSD and a deflected TMD with the same line direction since the large c component is the dominant contributor to the effective misorientation, whereas the effect of a component is rather negligible. Therefore, this effective penetration depth study uses ray tracing simulation images of deflected TSDs with photoelectric absorption applied to compare with all topographically observed Frank type dislocations. Analysis first reveals that the effective penetration depth varies with the line direction of a Frank type dislocation, and the effective penetration depth is significantly deeper compared to that of a BPD. Further, the effective penetration depth on ray tracing simulations with absorption applied matches well with experimentally measured depth. The study also evaluated the effectiveness of a simplified model based on an approximate expression for the effective misorientation of a dislocation modulated by photoelectric absorption. This was also found to yield satisfactory results and can be used as a universal method to determine the effective penetration depth for Frank type dislocations with c component of Burgers vector.
Utilization of Carbon Biomass as an Absorbing Material in Anti-Microwave Brick Walls Manufacturing
Authors: Narudin Nur Hashira , Abdullah Hasnain , Taib Mohd Nasir , Hadi Basharudin Abdul , Ahmad Azizah , Kasim Nazirah Mohamat , Ismail Noor Azila
Published: June 2023

The developments in communications technology bring changes in human life, and the positive aspects of these technological innovations make life more accessible. However, the use of communications technology at a certain frequency will produce radiation that could negatively affect human health. Thus, various studies have been performed to obtain a corresponding material to reduce the levels of exposure to the pollution of the electromagnetic wave signal. This study aims to build anti-microwave brick walls and analyze the absorption performance of the anti-microwave brick walls by using carbon biomass as an absorbing material. Carbon biomass is a physically defined product obtained in a highly controlled process to produce specifically engineered aggregates of carbon particles and in this project, carbon biomass was used as an absorbing material in brick production. The absorption performance of the anti-microwave brick walls was measured by using Naval Research Laboratory (NRL) arch free-space method, and the frequency range of 1GHz to 12GHz is used. The result shows that brick containing the highest percentage of carbon biomass produces the best absorption performance at a high-frequency band (4-8GHz), with maximum absorption of -29.53dB.
Correlation of Extended Defects with Electrical Yield of SiC MOSFET Devices
Authors: Baierhofer Daniel , Thomas Bernd , Staiger F. , Marchetti B. , Förster C. , Erlbacher Tobias
Published: June 2023

The quality of the silicon carbide (SiC) epitaxial layer, i.e., layer homogeneities and extended defect densities, is of highest importance for high power 4H-SiC trench metal-oxide-semiconductor field effect transistors (Trench-MOSFET) devices. Especially, yield for devices with a large chip area is severely impacted by extended defects. Previously, devices had to be fully manufactured to effectively gauge the impact of a reduction in extended defect densities in the epitaxial layers on device yield. The production of devices such as Trench-MOSFETs is an extensive procedure. Therefore, a correlation between extended defects in the epitaxial layer and electrical device failure would allow to reliably estimate the impact of process changes during epitaxial layer deposition on electrical device yield.For this reason, n-type epitaxial layers were grown on around 1,000 commercially available 150 mm 4H-SiC Si-face substrates, which received a chemical wet cleaning prior to the epitaxy deposition. Substrates with lowest micro-pipe density from two different suppliers were used. The wafers were characterized with the corresponding device layout for defects utilizing surface microscopy as well as ultraviolet photoluminescence techniques. Subsequently, these wafers were used to produce more than 500,000 Trench-MOSFET devices. All devices have been tested on wafer level for their initial electrical integrity.With these methods a precise correlation between extended defects in the epitaxial layer and electrical failures on wafer level could be found. The influence of different substrates on the defect-based yield prediction regarding the electrical yield on wafer level is discussed. Additionally, a calculated kill-ratio is presented and the severity of defect classes on initial device failure, e.g., stacking faults, and their key failures modes are discussed.
Mechanical Properties Comparison Between Induction Hardening and Rehardening of Axle Shaft AISI 1043 According to JIS G 0559 Standard
Authors: Muslimin Muslimin , Sudarmawan Grenny , Yoslin Zhazha , Luqyana Dhiya
Published: June 2023

Induction hardening is carried out to increase the hardness of the axle shaft surface. Axle shaft specimens were hardened from the bearing seat area to the spline area of the axle. The hardness requirements of the scope of the shaft met 400-450 HV of the JIS G 0559 standard. The axle shaft's hardening process with induction coil stops in the field before reaching the spline area. It causes the hardness becomes uneven and not comply with the standard. The re-hardening process is often carried out to repair rejected parts. In this work, the result of the re-hardening process is analyzed and compared with the first hardening process—the analysis focus on mechanical properties such as static test (torque test), fatigue testing, and hardness. Microstructures were used to verify the result of the process. The results showed that the results of re-hardening can meet the expected qualifications. The difference in breaking torque (static test) values ​​is 4,428.155 Nm for hardening specimens and 4,287.832 Nm for re-hardening with a standard torque of 4,000.000 Nm, all samples fractured in the spline area. High fatigue values ​​were obtained from the hardening results, with 216,265 cycles and 252,224 cycles for re-hardening. The results of the re-hardening hardness test obtained from Vickers are higher than the hardening results. The results of microstructural testing in both hardening processes contained ferrite and Fe3C on the surface and for the core consisting of ferrite and pearlite. Based on the analysis, the re-hardening process has no significant effect compared with the hardening results. Therefore, in this case, the re-hardening process can be used to fix the failed part.
Hydrodynamic Stability Analysis for MHD Casson Fluid Flow through a Restricted Channel
Authors: Adesanya Samuel Olumide , Yusuf Tunde AbdulKadri , Adeosun Adesina Taofeek , Rundora Lazarus
Published: June 2023

Flow instability is a major challenge experienced in medical, engineering and industrial settings globally. For instance, flow instability linked with irregular cardiac output of the heart leads to organ malfunctioning in the medical field, it also encourages mechanical vibrations in the case of fluctuating flow rate, and several other applications. In this study, linear stability analysis is conducted to monitor the behavior of a small disturbance that is imposed on hydromagnetic Casson fluid that flows steadily through a saturated porous medium. A new variant of the Orr-Sommerfield equation is obtained and solved numerically by using spectral point collocation weighted residual approach with eigenfunction expansion of the Chebyshev polynomial as the admissible trial function. Based on the QZ algorithm, numerical results are obtained for wave and Reynold’s numbers, wave velocity as functions of Magnetic field intensity and porosity shape parameters. Results are validated against previously released data. The biophysics of the heart, particularly in cardiac rhythm analysis, as well as several other medicinal and technical applications, is among the areas where the current work has applicability.
Study on Estimation of Device Yield in Non-Epitaxial 4H-SiC Material Relating to Defect Densities Influencing Bipolar Degradation with XRT- Measurements
Authors: Jayaprakash Hitesh , Csato Constantin , Erlbacher Tobias , Kranert Christian , Krippendorf Florian , Wimmer Paul , Reimann Christian , Rueb Michael
Published: June 2023

Commercially available 4H-SiC substrate quality has improved over time, and this has extensively reduced defect concentration in the active epitaxial layer, during epi growth conditions at the interface. The objective of this work is to investigate bulk crystal quality for the purpose of future vertical power device fabrication in exfoliated, non-epitaxial, undoped material layers. Mathematical estimations on the device yield fraction, that is immune to bipolar degradation for the suggested future process were calculated based on XRT measurements to detect BPD and TSD densities on donor substrates. The full wafer BPD density maps of on-axis semi-insulating wafer substrates from two vendors were compared.
Fabrication of Chemotaxis Microfluidic Device Mould Using Digital Light Processing 3D Printing Method
Authors: Jemy Amelia Nuraisyah Quinsi , Saptaji Kushendarsyah , Triawan Farid , Ifat I. , Setiawan Iwan
Published: June 2023

Chemotaxis microfluidic devices are one type of lab-on-a-chip (LOC) devices that functions to minimize the volume of sample used and the testing time by conducting an analysis on a smaller scale. Chemotaxis microfluidic devices consist of micro-scale features that are delicate to be produced using conventional manufacturing methods. Chemotaxis microfluidic devices are generally manufactured using soft lithography. This study attempts to apply hot embossing process to replace soft lithography process, in which the hot embossing mould was fabricated using 3D printing, especially digital light processing (DLP) methods. This project investigates the challenges of fabricating the hot embossing mould of chemotaxis microfluidic device using DLP 3D printing. Three printed orientations for the moulds were produced and compared. The three moulds are subsequently used in the hot embossing process to produce chemotaxis microfluidic devices on poly(methyl methacrylate) (PMMA) substrate. The performance of the moulds is compared to the mould produced by micro-milling process using qualitative (visual analysis) and quantitative (dimensional analysis) methods. The analysis shows that DLP 3D printed moulds have comparable quality with those produced by micro-milling. The printing orientation has significant effect on the dimensional differences between the mould and design with mould WT (area of width and thickness attached to the platform) has the smallest dimensional differences.
High Density 65W AC-DC Adaptor Enabled by SiC MOSFET with Ultralow VGS(on)
Authors: Hsu Fu Jen , Yen Cheng Tyng , Hung Hsiang Ting , Hu Jia Wei , Huang Chih Fang
Published: June 2023

SiC MOSFETs are rarely used in low-power consumer applications because of their cost and gate driving circuitry requirement. In this work, a cost-efficient SiC MOSFET with a usable 10V of VGS is proposed. The proposed SiC MOSFET could enable low-power applications, which is around tens to hundreds of watt, to implement SiC MOSFETs. As a result, the thermal performance is better than the GaN solution thanks to the better thermal conductance of the SiC.