WorldCat Identities

Syvajarvi, Mikael

Overview
Works: 44 works in 72 publications in 1 language and 1,381 library holdings
Roles: Editor, Author, Contributor, Other, the, Opponent
Publication Timeline
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Most widely held works by Mikael Syvajarvi
Advanced materials for agriculture, food, and environmental safety by Ashutosh Tiwari( )

7 editions published in 2014 in English and held by 755 WorldCat member libraries worldwide

The levels of toxic and microbial contamination in the food and environment are influenced by harvesting or slaughtering technologies and by the processes applied during food manufacture. With current cultivation methods, it is impossible to guarantee the absence of pesticides and pathogenic microorganisms in raw foods, both of plant and animal origin. Widespread and increasing incidence of foodborne diseases and the resulting social and economic impact on the world population have brought food and environmental safety to the forefront of ecological safety and public health concerns. The emer
Graphene materials : fundamentals and emerging applications by Ashutosh Tiwari( )

9 editions published in 2015 in English and held by 292 WorldCat member libraries worldwide

Cover; Title Page; Copyright Page; Contents; Preface; Foreword; Part 1: Fundamentals of Graphene and Graphene-Based Nanocomposites; 1 Graphene and Related Two-Dimensional Materials; 1.1 Introduction; 1.2 Preparation of Graphene Oxide by Modified Hummer's Method; 1.3 Dispersion of Graphene Oxide in Organic Solvents; 1.4 Paper-like Graphene Oxide; 1.5 Thin Films of Graphene Oxide and Graphene; 1.6 Nanocomposites of Graphene Oxide; 1.7 Graphene-Based Materials; 1.8 Graphene-like 2D Materials; 1.8.1 Tungsten Sulfide; 1.8.1.1 Different Methods for WS2 Preparation; 1.8.1.2 Properties of WS2
Advanced 2D materials by Ashutosh Tiwari( )

9 editions published in 2016 in English and held by 265 WorldCat member libraries worldwide

Advanced 2D materials by Ashutosh Tiwari( )

1 edition published in 2016 in English and held by 17 WorldCat member libraries worldwide

Wide band gap materials and new developments( Book )

4 editions published between 2006 and 2007 in English and held by 6 WorldCat member libraries worldwide

The role of defects in fluorescent silicon carbide layers grown by sublimation epitaxy by Symposium G EMRS 2013 Spring Meeting( )

2 editions published in 2014 in English and held by 3 WorldCat member libraries worldwide

Donor-acceptor co-doped SiC is a promising light converter for novel monolithic all-semiconductor white LEDs due to its broad-band donor-acceptor pair luminescence and potentially high internal quantum efficiency. Besides sufficiently high doping concentrations in an appropriate ratio yielding short radiative lifetimes, long nonradiative lifetimes are crucial for efficient light conversion. The impact of different types of defects is studied by characterizing fluorescent silicon carbide layers with regard to photoluminescence intensity, homogeneity and efficiency taking into account dislocation density and distribution. Different doping concentrations and variations in gas phase composition and pressure are investigated
Alternative approaches of SiC & related wide bandgap materials in light emitting & solar cell applications by P Wellmann( )

1 edition published in 2014 in English and held by 2 WorldCat member libraries worldwide

Graphene Materials Fundamentals and Emerging Applications by Mikael Syvajarvi( )

1 edition published in 2015 in English and held by 2 WorldCat member libraries worldwide

Lien entre structure et propriétés électroniques des moirés de graphène étudié par microscopie à effet tunnel by Loïc Huder( )

1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide

Recent years have seen the emergence of two-dimensional crystalline layers, called 2D materials. Examples include the well-known graphene, insulating hexagonal boron nitride and superconducting niobium diselenide. The stacking of these 2D materials can be controlled to achieve desirable electronic properties under the form of van der Waals heterostructures. One of the simplest van der Waals heterostructures is the misaligned stacking of two graphene layers. Twisted graphene layers show a moiré pattern which can be viewed as a superperiodic potential that depends on the twist angle. The electronic properties of the twisted graphene layers are strongly linked to this moiré pattern.The subject of the present thesis is the experimental study of the link between the structural and the electronic properties of twisted graphene layers by means of low-temperature Scanning Tunneling Microscopy and Spectroscopy (STM/STS).While the effect of the twist angle has already been studied in great details, the modulation of the electronic properties by the deformation of the layers has been explored only recently. In the first part of this experimental work, a strain-driven modification of the electronic properties is probed in graphene layers with a twist angle of 1.26° grown on silicon carbide. The determined strain is found to be different in the two layers leading to a clear signature in the local electronic density of states of the moiré even at low strain magnitudes. Contrary to a strain applied in the two layers, this difference of strain between the layers (relative strain) modifies strongly the electronic band structure even at low strain magnitudes. While this relative strain is natively present, the second part of the work explores the effect of an applied strain in the layers. This is realized by approaching the STM tip to the graphene surface to trigger an interaction between the two. The resulting active modification of the density of states is shown to depend on the position on the moiré, leading to periodic instabilities at very low tip-sample distances.In the third part of the work, another type of modification of the electronic properties is studied when superconductivity was induced in the graphene layers. This is done by growing graphene on superconducting tantalum carbide in a single-step annealing. The results show the formation of a high-quality tantalum carbide layer on which graphene layers form moiré patterns. The low-temperature density of states of these moirés show evidence of a superconducting proximity effect induced by the tantalum carbide
High growth rate epitaxy of SiC : growth processes and structural quality by Mikael Syvajarvi( Book )

2 editions published in 1999 in English and held by 2 WorldCat member libraries worldwide

Étude du procédé de croissance en solution à haute température pour le développement de substrats de 4H-SiC fortement dopes by Yun ji Shin( )

1 edition published in 2016 in English and held by 2 WorldCat member libraries worldwide

Silicon Carbide is a wide band gap semiconductor which has recently imposed as a key material for modern power electronics. Bulk single crystals and active epilayers are industrially produced by vapor phase processes, namely seeded sublimation growth (PVT) and chemical vapor deposition (CVD) respectively. The high temperature solution growth is currently being revisited due to its potential for achieving high structural quality. This work is a contribution to the development of the top seeded solution growth (TSSG) process, with a special focus on heavily p-type doped 4H-SiC crystals. Aluminum (Al) is the most commonly used acceptor in SiC. Different elementary steps of the process are studied, and for every cases, the effect of Al is considered and discussed. After a brief history of SiC material, basic structural and physical properties of silicon carbide are introduced in chapter 1 and discussed with respect to power electronics applications. In chapter 2, the crystal growth puller is detailed and the three most important technical issues of the SiC solution growth process are discussed : i) carbon supply by dissolution at the graphite crucible/liquid interface, ii) carbon transport from the dissolution area to the growth front, and iii) crystallization on the seed substrate. These three steps are studied and improved by adding transition metals (Fe or Cr) to the solvent in order to increase the carbon solubility, by increasing the carbon transport with the optimization of the forced convection (i.e. rotation of the crystal) and by stabilizing the growth front. After optimization, a 4H-SiC crystal is demonstrated with a growth rate of over 300 µm/h and a diameter enlargement of about 41% compared to the original seed size. Chapter 3 is dedicated to the investigation of the interaction between the liquid solvent and the 4H-SiC surface under equilibrium conditions, i.e. without any growth, using a sessile drop method. Effect of time, temperature and the addition of Al to pure liquid silicon are investigated. It is shown that the liquid/solid exhibits a three stages evolution: i) dissolution, ii) step bunching and iii) faceting, the original step and terrace structure being decomposed into (0001), (10-1n) and (01-1n) facets. Increasing the temperature from 1600°C to 1800°C or adding Al drastically enhances the second stage, but reduces the third one. In chapter 4, transient phenomena during the seeding stage of the growth process on the seed crystal are investigated. With the help of numerical modeling, it is shown that strong temperature fluctuations during the contact between the seed and the liquid can give rise to transient 3C-SiC nucleation on the crystal surface, even at high temperatures. This phenomenon can be avoided by either pre-heating the seed or by adding Al. Increasing forced convection (rotation rate of the crystal) is a good way to increase the growth rate. However, above a critical rotation rate, a special surface instability develops. It is based on the interaction between the step flow at the growing surface and the local fluid flow directions close to the surface. This is investigated in Chapter 5. Finally, carrier concentrations and total dopant (nitrogen and aluminum) concentrations are investigated as a function of different process parameters in chapter 6. Al incorporation as high as 5E+20 at/cm3 has been achieved in layers grown at 1850°C. This value is very promising for the future development of p+ 4H-SiC substrates
Bioelectrocatalysis on Anodized Epitaxial Graphene and Conventional Graphitic Interfaces by Mikhail Vagin( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

Graphitic materials exhibit significant anisotropy due to the difference in conductivity in a single layer and between adjacent layers. This anisotropy is manifested on epitaxial graphene (EG), which can be manipulated on the nanoscale in order to provide tailor-made properties. Insertion of defects into the EG lattice was utilized here for controllable surface modification with a model biocatalyst and the properties were quantified by both electrochemical and optical methods. A comparative evaluation of the electrode reaction kinetics on the enzyme-modified 2D material vs conventional carbon electrode materials revealed a significant enhancement of mediated bioelectrocatalysis at the nanoscale
Influence of twin boundary orientation on magnetoresistivity effect in free standing 3C-SiC by Remigijus Vasiliauskas( )

1 edition published in 2012 in English and held by 1 WorldCat member library worldwide

Free standing 3C-SiC (111) samples with differently oriented twin boundaries were prepared using on-axis and slightly off-axis 6H-SiC substrates. The orientation of twin boundaries causes either an enhancement or suppression of the magnetoresistance mobility. The origin of carrier mobility difference is attributed to the specific structure of these defects. The height of the barriers created by twin boundaries was found to be 0.2 eV
A comparative study of high-quality C-face and Si-face 3C-SiC(1 1 1) grown on off-oriented 4H-SiC substrates by Yuchen Shi( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

We present a comparative study of the C-face and Si-face of 3C-SiC(111) grown on off-oriented 4H-SiC substrates by the sublimation epitaxy. By the lateral enlargement method, we demonstrate that the high-quality bulk-like C-face 3C-SiC with thickness of ~1 mm can be grown over a large single domain without double positioning boundaries (DPBs), which are known to have a strongly negative impact on the electronic properties of the material. Moreover, the C-face sample exhibits a smoother surface with one unit cell height steps while the surface of the Si-face sample exhibits steps twice as high as on the C-face due to step-bunching. High-resolution XRD and low temperature photoluminescence measurements show that C-face 3C-SiC can reach the same high crystalline quality as the Si-face 3C-SiC. Furthermore, cross-section studies of the C- and Si-face 3C-SiC demonstrate that in both cases an initial homoepitaxial 4H-SiC layer followed by a polytype transition layer are formed prior to the formation and lateral expansion of 3C-SiC layer. However, the transition layer in the C-face sample is extending along the step-flow direction less than that on the Si-face sample, giving rise to a more fairly consistent crystalline quality 3C-SiC epilayer over the whole sample compared to the Si-face 3C-SiC where more defects appeared on the surface at the edge. This facilitates the lateral enlargement of 3C-SiC growth on hexagonal SiC substrates
Alternative approaches of SiC et related wide bandgap materials in light emitting et solar cell applications by P Wellmann( )

1 edition published in 2014 in English and held by 1 WorldCat member library worldwide

Considerably long carrier lifetimes in high-quality 3C-SiC(111) by Xuefei( )

1 edition published in 2012 in English and held by 1 WorldCat member library worldwide

As a challenge and consequence due to its metastable nature, cubic silicon carbide (3C-SiC) has only shown inferior material quality compared with the established hexagonal polytypes. We report on growth of 3C-SiC(111) having a state of the art semiconductor quality in the SiC polytype family. The x-ray diffraction and low temperature photoluminescence measurements show that the cubic structure can indeed reach a very high crystal quality. As an ultimate device property, this material demonstrates a measured carrier lifetime of 8.2 mu s which is comparable with the best carrier lifetime in 4 H-SiC layers. In a 760-mu m thick layer, we show that the interface recombination can be neglected since almost all excess carriers recombines before reaching the interface while the surface recombination significantly reduces the carrier lifetime. In fact, a comparison of experimental lifetimes with numerical simulations indicates that the real bulk lifetime in such high quality 3C-SiC is in the range of 10-15 mu s
Cubic SiC formation on the C-face of 6H-SiC (0001) substrates by Remigijus Vasiliauskas( )

1 edition published in 2012 in English and held by 1 WorldCat member library worldwide

Growth optimization and applicability of thick on-axis SiC layers using sublimation epitaxy in vacuum by Valdas Jokubavicius( )

1 edition published in 2016 in English and held by 1 WorldCat member library worldwide

We demonstrate growth of thick SiC layers (100-200 µm) on nominally on-axis hexagonal substrates using sublimation epitaxy in vacuum (10 −5 mbar) at temperatures varying from 1700 to 1975 °C with growth rates up to 270 µm/h and 70 µm/h for 6H- and 4H-SiC, respectively. The stability of hexagonal polytypes are related to process growth parameters and temperature profile which can be engineered using different thermal insulation materials and adjustment of the induction coil position with respect to the graphite crucible. We show that there exists a range of growth rates for which single-hexagonal polytype free of foreign polytype inclusions can be maintained. Further on, foreign polytypes like 3C-SiC can be stabilized by moving out of the process window. The applicability of on-axis growth is demonstrated by growing a 200 µm thick homoepitaxial 6H-SiC layer co-doped with nitrogen and boron in a range of 10 18 cm −3 at a growth rate of about 270 µm/h. Such layers are of interest as a near UV to visible light converters in a monolithic white light emitting diode concept, where subsequent nitride-stack growth benefits from the on-axis orientation of the SiC layer
Atomic-Scale Tuning of Graphene/Cubic SiC Schottky Junction for Stable Low-Bias Photoelectrochemical Solar-to-Fuel Conversion by Hao Li( )

1 edition published in 2020 in English and held by 1 WorldCat member library worldwide

Engineering tunable graphene-semiconductor interfaces while simultaneously preserving the superior properties of graphene is critical to graphene-based devices for electronic, optoelectronic, biomedical, and photoelectrochemical applications. Here, we demonstrate this challenge can be surmounted by constructing an interesting atomic Schottky junction via epitaxial growth of high-quality and uniform graphene on cubic SiC (3C-SiC). By tailoring the graphene layers, the junction structure described herein exhibits an atomic-scale tunable Schottky junction with an inherent built-in electric field, making it a perfect prototype to systematically comprehend interfacial electronic properties and transport mechanisms. As a proof-of-concept study, the atomicscale-tuned Schottky junction is demonstrated to promote both the separation and transport of charge carriers in a typical photoelectrochemical system for solar-to-fuel conversion under low bias. Simultaneously, the as-grown monolayer graphene with an extremely high conductivity protects the surface of 3C-SiC from photocorrosion and energetically delivers charge carriers to the loaded cocatalyst, achieving a synergetic enhancement of the catalytic stability and efficiency
A nanostructured NiO/cubic SiC p-n heterojunction photoanode for enhanced solar water splitting by Jingxin Jian( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

Photoelectrochemical (PEC) water-splitting offers a promising method to convert the intermittent solar energy into renewable and storable chemical energy. However, the most studied semiconductors generally exhibit a poor PEC performance including low photocurrent, small photovoltage, and/or large onset potential. In this work, we demonstrate a significant enhancement of photovoltage and photocurrent together with a substantial decrease of onset potential by introducing electrocatalytic and p-type NiO nanoclusters on an n-type cubic silicon carbide (3C-SiC) photoanode. Under AM1.5G 100 mW cm( -2) illumination, the NiO-coated 3C-SiC photoanode exhibits a photocurrent density of 1.01 mA cm( -2) at 0.55 V versus reversible hydrogen electrode (V-RHE), a very low onset potential of 0.20 V-RHE and a high fill factor of 57% for PEC water splitting. Moreover, the 3C-SiC/NiO photoanode shows a high photovoltage of 1.0 V, which is the highest value among reported photovoltages. The faradaic efficiency measurements demonstrate that NiO also protects the 3C-SiC surface against photo-corrosion. The impedance measurements evidence that the 3C-SiC/NiO photoanode facilitates the charge transfer for water oxidation. The valence-band position measurements confirm the formation of the 3C-SiC/NiO p-n heterojunction, which promotes the separation of the photogenerated carriers and reduces carrier recombination, thus resulting in enhanced solar water-splitting
 
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Advanced materials for agriculture, food, and environmental safety
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Graphene materials : fundamentals and emerging applicationsAdvanced 2D materialsAdvanced 2D materials
Alternative Names
Syvajarvi, Mikael

Languages
English (47)