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Surface properties of refractory ceramic transition metal nitride thin films grown by magnetron sputtering are essential for resistance towards oxidation necessary in all modern applications. Here, typically neglected factors, including exposure to residual process gases following the growth and the venting temperature T-v, each affecting the surface chemistry, are addressed. It is demonstrated for the TiN model materials system that T-v has a substantial effect on the composition and thickness-evolution of the reacted surface layer and should therefore be reported. The phenomena are also shown to have impact on the reliable surface characterization by x-ray photoelectron spectroscopy. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License. ; Funding Agencies|German Research Foundation (DFG) [SFB-TR 87]; VINN Excellence Center Functional Nanoscale Materials (FunMat) [2005-02666]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00971]; Knut and Alice Wallenberg Foundation [2011.0143]

Alkylboranes, such as trimethylboron (TMB) and triethylboron (TEB), are promising alternative precursors in low temperature chemical vapor deposition (CVD) of boron-containing thin films. In this study, CVD growth of B-C films using TMB and quantum-chemical calculations to elucidate a gas phase chemical mechanism were undertaken. Dense, amorphous, boron-rich (B/C 1.5-3) films were deposited at 1000 degrees C in both dihydrogen and argon ambients, while films with crystalline B4C and B25C inclusions were deposited at 1100 degrees C in dihydrogen. A script-based automatization scheme was implemented for the quantum-chemical computations to enable time efficient screening of thousands of possible gas phase CVD reactions. The quantum-chemical calculations suggest TMB is mainly decomposed by an unimolecular alpha-H elimination of methane, which is complemented by dihydrogen-assisted elimination of methane in dihydrogen. ; Funding Agencies|European Spallation Source ERIC; Knut and Alice Wallenberg Foundation; German Science Foundation [GRK 1782]; Swedish Foundation for Strategic Research (SSF) [IS14-0027]; COST Action [MP1402]; COST (European Cooperation in Science and Technology); Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]

Energy crisis and thermal management related issues have been highlighted in the modern century due to escalating demands for energy consumption and global warming from fossil fuels. Sustainable and alternative energy sources are an ever growing global concern. Thermoelectric (TE) materials have gained significant interest, due to effective solid-state energy conversion from waste heat to useful electrical energy and vice versa. Clean, noise-free, and environment-friendly operation of TE devices has triggered great attention in viable technologies including automotive, military equipment, aerospace, and industries to scavenge waste heat into power. To date, conventional TE materials have shown limited energy conversion efficiency, i.e. TE Figure of Merit (ZT). However, the concept of nanostructuring and development of novel TE materials have opened excellent avenues to improve significantly the ZT values. Nano-engineered bulk TE materials allow effective phonon scattering at the high density of grain boundaries, which offer a way of lowering the thermal conductivity. Large-scale synthesis of TE nanomaterials is a challenge for the TE industry because of expensive fabrication processes involved. This thesis reports several nano-engineering approaches for fabricating large quantities of bulk nanostructured TE materials. We have developed bottom-up chemical synthesis routes, as well as top-down mechanical alloying methodologies, to produce highly pure, homogenous and highly crystalline TE nanomaterials. State of the art chalcogenide, iron antimonide, and silicide based TE materials have been investigated in this thesis. Chalcogenide are the best candidates for TE devices operating at temperature range up to 450 K. Iron antimonide (FeSb2) have shown attractive performance below room temperature. Earth abundant and environment friendly, silicide based materials have better ZT performance in the range of 600-900 K. Spark plasma sintering (SPS) was utilized to preserve the nanostructuring and to achieve the highest ...

Organic electrochemical transistors (OECTs) have emerged as an enabling technology for the development of a variety of applications ranging from digital logic circuits to biosensors and artificial synapses for neuromorphic computing. To date, most of the reported OECTs rely on the use of p-type (hole transporting) conducting and semiconducting polymers as the channel material, while electron transporting (n-type) OECTs are yet immature, thus precluding the realization of advanced complementary circuitry. In this highlight, we review and discuss recent achievements in the area of n-type OECTs, in particular targeting recently reported n-type channel materials and how these have enabled a considerable advancement of OECT circuit capabilities. Further, the critical challenges currently limiting the performance of n-channel OECTs are summarized and discussed, setting material design guidelines for the next generation n-type and complementary OECTs. ; Funding Agencies|Swedish Research Council [2016-03979]; Swedish Governmental Agency for Innovation Systems - VINNOVA [2015-04859]; Swedish Foundation for Strategic Research [SE13-0045, RIT15-0119]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]

Cover -- Title Page -- Copyright -- Contents -- Preface -- Chapter 1 Thermodynamics of Homogeneous and Heterogeneous Semiconductor Systems -- 1.1 Introduction -- 1.2 Basic Principles -- 1.3 Phases and Their Properties -- 1.3.1 Structural Order of a Phase -- 1.4 Equations of State of Thermodynamic Systems -- 1.4.1 Thermodynamic Transformations and Functions of State -- 1.4.2 Work Associated with a Transformation, Entropy and Free Energy -- 1.4.3 Chemical Potentials -- 1.4.4 Free Energy and Entropy of Spontaneous Processes -- 1.4.5 Effect of Pressure on Phase Transformations, Polymorphs/Polytypes Formation and Their Thermodynamic Stability -- 1.4.6 Electrochemical Equilibria and Electrochemical Potentials of Charged Species -- 1.5 Equilibrium Conditions of Multicomponent Systems Which Do Not React Chemically -- 1.6 Thermodynamic Modelling of Binary Phase Diagrams -- 1.6.1 Introductory Remarks -- 1.6.2 Thermodynamic Modelling of Complete and Incomplete Miscibility -- 1.6.3 Thermodynamic Modelling of Intermediate Compound Formation -- 1.6.4 Retrograde Solubility, Retrograde Melting and Spinodal Decomposition -- 1.7 Solution Thermodynamics and Structural and Physical Properties of Selected Semiconductor Systems -- 1.7.1 Introductory Remarks -- 1.7.2 Au-Ag and Au-Cu Alloys -- 1.7.3 Silicon and Germanium -- 1.7.4 Silicon-Germanium Alloys -- 1.7.5 Silicon- and Germanium-Binary Alloys with Group III and Group IV Elements -- 1.7.6 Silicon-Tin and Germanium-Tin Alloys -- 1.7.7 Carbon and Its Polymorphs -- 1.7.8 Silicon Carbide -- 1.7.9 Selenium-Tellurium Alloys -- 1.7.10 Binary and Pseudo-binary Selenides and Tellurides -- 1.7.11 Arsenides, Phosphides and Nitrides -- 1.8 Size-Dependent Properties, Quantum Size Effects and Thermodynamics of Nanomaterials -- Appendix.

Electron transport materials (ETMs) are widely used as interlayers to lower the cathode electrode work function in organic solar cells and organic light-emitting diodes, for example. The usual interpretation for their operating principle is a chemical interaction between the ETM and the electrode, inducing partial or integer charge transfer or collectively an intrinsic dipole moment caused by preferential molecular orientation. Herein, we systematically explore the commonly used ETM bathophenanthroline (BPhen) deposited on a series of conducting substrates. The energetics at the BPhen interface follows the typical integer charge transfer (ICT) model with an extra displacement of the vacuum level by up to -1.4 eV. The extra displacement is ascribed to the "double dipole step" formed by the positive and negative charged species and their induced image charges when they are close to the surface of substrates. After n-type doping the displacement is further increased to -1.8 eV, yielding a larger work function modification than obtained using typical electrolytes and zwitterions as cathode interlayer. ; Funding Agencies|Knut and Alice Wallenberg Foundation project "Tail of the Sun; Swedish Research CouncilSwedish Research Council [2016-05498]; Swedish Foundation for Strategic ResearchSwedish Foundation for Strategic Research [SE13-0060]; Ministry of Science and TechnologyMinistry of Education, Culture, Sports, Science and Technology, Japan (MEXT)Ministry of Science and Technology, Government of India [2016YFA0200700]; NSFCNational Natural Science Foundation of China [21504066, 21534003]; Swedish Energy AgencySwedish Energy Agency [45411-1]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO Mat LiU) [2009 00971]

International audience ; Whatever the field of application (building, transportation, packaging, etc.) energy losses must be reduced to meet the government target of a 40% cut in CO 2 emissions. This leads to a challenge for materials scientists: designing materials with thermal conductivities lower than 0.015 W m À1 K À1 under ambient conditions. Such a low value requires reducing air molecule mobility in highly porous materials, and silica-based superinsulation materials (SIM) made of packed nanostructured silica or aerogel are good candidates for this purpose. However, the native nanostructure of silica has never been imaged or characterized up to now, making SIM optimization quite difficult. In this paper, three nanostructured commercial silica samples prepared by different synthesis methods were analysed and quantified using advanced electron tomography, N 2 physisorption, mercury porosimetry and helium pycnometry. It was demonstrated that 3D images yield a much finer description of the microstructure (particle, aggregate and pore) compared to global measurements. For the samples studied, silica particle size is dependent on the synthesis method, increasing with pore diameter size. The smallest silica particles were obtained by the sol–gel method which also provides the smallest pore diameters, the smallest and rather spherical aggregates, and the lowest thermal conductivity. The pyrogenic and precipitated samples studied presented bigger silica particles with higher pore diameters and thus higher thermal conductivities. 3D image driven characterization opens up new synthesis opportunities for silica.

International audience ; Whatever the field of application (building, transportation, packaging, etc.) energy losses must be reduced to meet the government target of a 40% cut in CO 2 emissions. This leads to a challenge for materials scientists: designing materials with thermal conductivities lower than 0.015 W m À1 K À1 under ambient conditions. Such a low value requires reducing air molecule mobility in highly porous materials, and silica-based superinsulation materials (SIM) made of packed nanostructured silica or aerogel are good candidates for this purpose. However, the native nanostructure of silica has never been imaged or characterized up to now, making SIM optimization quite difficult. In this paper, three nanostructured commercial silica samples prepared by different synthesis methods were analysed and quantified using advanced electron tomography, N 2 physisorption, mercury porosimetry and helium pycnometry. It was demonstrated that 3D images yield a much finer description of the microstructure (particle, aggregate and pore) compared to global measurements. For the samples studied, silica particle size is dependent on the synthesis method, increasing with pore diameter size. The smallest silica particles were obtained by the sol–gel method which also provides the smallest pore diameters, the smallest and rather spherical aggregates, and the lowest thermal conductivity. The pyrogenic and precipitated samples studied presented bigger silica particles with higher pore diameters and thus higher thermal conductivities. 3D image driven characterization opens up new synthesis opportunities for silica.

International audience ; Whatever the field of application (building, transportation, packaging, etc.) energy losses must be reduced to meet the government target of a 40% cut in CO 2 emissions. This leads to a challenge for materials scientists: designing materials with thermal conductivities lower than 0.015 W m À1 K À1 under ambient conditions. Such a low value requires reducing air molecule mobility in highly porous materials, and silica-based superinsulation materials (SIM) made of packed nanostructured silica or aerogel are good candidates for this purpose. However, the native nanostructure of silica has never been imaged or characterized up to now, making SIM optimization quite difficult. In this paper, three nanostructured commercial silica samples prepared by different synthesis methods were analysed and quantified using advanced electron tomography, N 2 physisorption, mercury porosimetry and helium pycnometry. It was demonstrated that 3D images yield a much finer description of the microstructure (particle, aggregate and pore) compared to global measurements. For the samples studied, silica particle size is dependent on the synthesis method, increasing with pore diameter size. The smallest silica particles were obtained by the sol–gel method which also provides the smallest pore diameters, the smallest and rather spherical aggregates, and the lowest thermal conductivity. The pyrogenic and precipitated samples studied presented bigger silica particles with higher pore diameters and thus higher thermal conductivities. 3D image driven characterization opens up new synthesis opportunities for silica.

International audience ; Whatever the field of application (building, transportation, packaging, etc.) energy losses must be reduced to meet the government target of a 40% cut in CO 2 emissions. This leads to a challenge for materials scientists: designing materials with thermal conductivities lower than 0.015 W m À1 K À1 under ambient conditions. Such a low value requires reducing air molecule mobility in highly porous materials, and silica-based superinsulation materials (SIM) made of packed nanostructured silica or aerogel are good candidates for this purpose. However, the native nanostructure of silica has never been imaged or characterized up to now, making SIM optimization quite difficult. In this paper, three nanostructured commercial silica samples prepared by different synthesis methods were analysed and quantified using advanced electron tomography, N 2 physisorption, mercury porosimetry and helium pycnometry. It was demonstrated that 3D images yield a much finer description of the microstructure (particle, aggregate and pore) compared to global measurements. For the samples studied, silica particle size is dependent on the synthesis method, increasing with pore diameter size. The smallest silica particles were obtained by the sol–gel method which also provides the smallest pore diameters, the smallest and rather spherical aggregates, and the lowest thermal conductivity. The pyrogenic and precipitated samples studied presented bigger silica particles with higher pore diameters and thus higher thermal conductivities. 3D image driven characterization opens up new synthesis opportunities for silica.

International audience ; Whatever the field of application (building, transportation, packaging, etc.) energy losses must be reduced to meet the government target of a 40% cut in CO 2 emissions. This leads to a challenge for materials scientists: designing materials with thermal conductivities lower than 0.015 W m À1 K À1 under ambient conditions. Such a low value requires reducing air molecule mobility in highly porous materials, and silica-based superinsulation materials (SIM) made of packed nanostructured silica or aerogel are good candidates for this purpose. However, the native nanostructure of silica has never been imaged or characterized up to now, making SIM optimization quite difficult. In this paper, three nanostructured commercial silica samples prepared by different synthesis methods were analysed and quantified using advanced electron tomography, N 2 physisorption, mercury porosimetry and helium pycnometry. It was demonstrated that 3D images yield a much finer description of the microstructure (particle, aggregate and pore) compared to global measurements. For the samples studied, silica particle size is dependent on the synthesis method, increasing with pore diameter size. The smallest silica particles were obtained by the sol–gel method which also provides the smallest pore diameters, the smallest and rather spherical aggregates, and the lowest thermal conductivity. The pyrogenic and precipitated samples studied presented bigger silica particles with higher pore diameters and thus higher thermal conductivities. 3D image driven characterization opens up new synthesis opportunities for silica.

ScN-rich (Sc,Nb)N solid solution thin films have been studied, motivated by the promising thermoelectric properties of ScN-based materials. Cubic Sc1-xNbxN films for 0 amp;lt;= x amp;lt;= 0.25 were epitaxially grown by DC reactive magnetron sputtering on a c-plane sapphire substrate and oriented along the (111) orientation. The crystal structure, morphology, thermal conductivity, and thermoelectric and electrical properties were investigated. The ScN reference film exhibited a Seebeck coefficient of -45 mu V/K and a power factor of 6 x 10(-4) W/m K-2 at 750K. Estimated from room temperature Hall measurements, all samples exhibit a high carrier density of the order of 10(21) cm(-3). Inclusion of heavy transition metals into ScN enables the reduction in thermal conductivity by an increase in phonon scattering. The Nb inserted ScN thin films exhibited a thermal conductivity lower than the value of the ScN reference (10.5W m(-1) K-1) down to a minimum value of 2.2 Wm(-1) K-1. Insertion of Nb into ScN thus resulted in a reduction in thermal conductivity by a factor of similar to 5 due to the mass contrast in ScN, which increases the phonon scattering in the material. Published by AIP Publishing. ; Funding Agencies|European Research Council under the European Community [335383]; Swedish Foundation for Strategic Research (SSF) through the Future Research Leaders 5 program; Swedish Research Council (VR) [621-2012-4430, 2016-03365]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]; project NanoCaTe (FP7-NMP) [604647]; project CTEC [1305-00002B]