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Phosphorus oxide (POx) capped by aluminum oxide (Al2O3) has recently been discovered to provide excellent surface passivation of crystalline silicon (c-Si). In this work, insights into the passivation mechanism of POx/Al2O3 stacks are gained through a systematic study of the influence of deposition temperature (Tdep = 100–300 °C) and annealing temperature (Tann = 200–500 °C) on the material and interface properties. It is found that employing lower deposition temperatures enables an improved passivation quality after annealing. Bulk composition, density, and optical properties vary only slightly with deposition temperature, but bonding configurations are found to be sensitive to temperature and correlated with the interface defect density (Dit), which is reduced at lower deposition temperature. The fixed charge density (Qf) is in the range of + (3–9) × 1012 cm–2 and is not significantly altered by annealing, which indicates that the positively charged entities are generated during deposition. In contrast, Dit decreases by 3 orders of magnitude (∼1013 to ∼1010 eV–1 cm–2) upon annealing. This excellent chemical passivation is found to be related to surface passivation provided by hydrogen, and mixing of aluminum into the POx layer, leading to the formation of AlPO4 upon annealing.

Phosphorus oxide (POx) capped by aluminum oxide (Al2O3) has recently been discovered to provide excellent surface passivation of crystalline silicon (c-Si). In this work, insights into the passivation mechanism of POx/Al2O3 stacks are gained through a systematic study of the influence of deposition temperature (Tdep = 100–300 °C) and annealing temperature (Tann = 200–500 °C) on the material and interface properties. It is found that employing lower deposition temperatures enables an improved passivation quality after annealing. Bulk composition, density, and optical properties vary only slightly with deposition temperature, but bonding configurations are found to be sensitive to temperature and correlated with the interface defect density (Dit), which is reduced at lower deposition temperature. The fixed charge density (Qf) is in the range of + (3–9) × 1012 cm–2 and is not significantly altered by annealing, which indicates that the positively charged entities are generated during deposition. In contrast, Dit decreases by 3 orders of magnitude (∼1013 to ∼1010 eV–1 cm–2) upon annealing. This excellent chemical passivation is found to be related to surface passivation provided by hydrogen, and mixing of aluminum into the POx layer, leading to the formation of AlPO4 upon annealing.

A critically important consideration of stiffened structural panels is the interfacial properties between skin and stiffener. In the present study a novel implementation of laser-assisted tape placement (LATP) was used to produce a representative skin-stiffener of a wingbox from carbon fibre reinforced PEEK. First, a stiffener is manufactured using this method and subsequently the skin is attached using the same method without need for a secondary bonding process. The interfacial properties between the skin and stiffener have been characterised in terms of interlaminar shear strength (ILSS) and fracture toughness (Mode-I and Mode-II) properties. LATP laydown direction and laser power was found to influence the skin-stiffener interface Mode-I fracture toughness, but not affect the Mode-II fracture toughness. The values of ILSS and fracture toughness compare favourably with those results reported in the literature, in particular for those reported for equivalent aerospace certified CF/PEEK material (APC-2)., Aerospace Manufacturing Technologies

A critically important consideration of stiffened structural panels is the interfacial properties between skin and stiffener. In the present study a novel implementation of laser-assisted tape placement (LATP) was used to produce a representative skin-stiffener of a wingbox from carbon fibre reinforced PEEK. First, a stiffener is manufactured using this method and subsequently the skin is attached using the same method without need for a secondary bonding process. The interfacial properties between the skin and stiffener have been characterised in terms of interlaminar shear strength (ILSS) and fracture toughness (Mode-I and Mode-II) properties. LATP laydown direction and laser power was found to influence the skin-stiffener interface Mode-I fracture toughness, but not affect the Mode-II fracture toughness. The values of ILSS and fracture toughness compare favourably with those results reported in the literature, in particular for those reported for equivalent aerospace certified CF/PEEK material (APC-2)., Aerospace Manufacturing Technologies

Shape memory alloy (SMA), more specifically Nickel-Titanium (NiTi), is widely used in many applications due to its intrinsic shape memory behavior. Recently, the opportunity to create new kind of composites has emerged by coupling NiTi alloy and silicone elastomer with hyper-elasticity allowing large deformations. For this novel material, the efficiency strongly depends on the quality of interface between SMA and rubber matrix. Previously, some efforts experimentally to study their adhesion have been already made. Now the aim of present work is to investigate the mechanical resistance of different NiTi/silicone rubber interfaces by employing a numerical approximation., Shape memory alloy (SMA), more specifically Nickel-Titanium (NiTi), is widely used in many applications due to its intrinsic shape memory behavior. Recently, the opportunity to create new kind of composites has emerged by coupling NiTi alloy and silicone elastomer with hyper-elasticity allowing large deformations. For this novel material, the efficiency strongly depends on the quality of interface between SMA and rubber matrix. Previously, some efforts experimentally to study their adhesion have been already made. Now the aim of present work is to investigate the mechanical resistance of different NiTi/silicone rubber interfaces by employing a numerical approximation.

The successful use of additives in modified asphalt mixtures, such as warm mix asphalt, depends largely on the effect such modification has on the mastic. Previous research indicated that such modifiers do not simply change the bitumen properties, but can also change the interaction between the filler and the bitumen matrix. Understanding the effect of the properties of the fillers, the bitumen and their interaction is thus important for future asphalt mix design. In order to investigate this and to define the dominant relationships, this paper combines a numerical and experimental approach. In the experiments, the viscosities of modified and unmodified mastics with different filler concentrations and types were systematically investigated utilizing a novel testing protocol. In the numerical analyses, the Finite Element Method was utilized for a micro-mechanical analysis, in which the shape and size of the filler particles were varied in the bitumen matrix. Combining the experimental and numerical results allowed for a detailed investigation of the effect of the interface properties, with and without modifiers. The research further indicated that the effect of the shape and size of the fillers varied, depending on the interface properties. From the research relationships were established between the overall mastic viscosity and the influence of the filler-bitumen interface, considering shape and size. The conclusion of this paper can thus be useful for the effective development of modified asphalt mixtures and gives strong indications towards future research directions., QC 20140818

With the access of new high-performance electron spectrometers capable of analyzing electron energies up to the order of 10 keV, the interest for photoelectron spectroscopy has grown and many new applications of the technique in areas where electron spectroscopies were considered to have limited use have been demonstrated over the last few decades. The technique, often denoted hard X-ray photoelectron spectroscopy (HX-PES or HAXPES), to distinguish the experiment from X-ray photoelectron spectroscopy performed at lower energies, has resulted in an increasing interest in photoelectron spectroscopy in many areas. The much increased mean free path at higher kinetic energies, in combination with the elemental selectivity of the core level spectroscopies in general has led to this fact. It is thus now possible to investigate the electronic structure of materials with a substantially enhanced bulk sensitivity. In this review we provide examples from our own research using HAXPES which to date has been performed mainly at the HIKE facility at the KMC-1 beamline at HZB, Berlin. The review exemplifies the new opportunities using HAXPES to address both bulk and interface electronic properties in systems relevant for applications in magnetic storage, energy related research, but also in purely curiosity driven problems.

Supervisor:Tatsuya Shimoda, マテリアルサイエンス研究科, 博士

Advances in instrumentation regarding 3rd generation synchrotron light sources and electron spectrometers has enabled the field of high kinetic energy photoelectron spectroscopy (HIKE) (also often denoted hard X-ray photoelectron spectroscopy (HX-PES or HAXPES)). Over the last years, the amount of investigations that relies on the HIKE method has increased dramatically and can arguably be said to have given a rebirth of the interest in photoelectron spectroscopy in many areas. It is in particular the much increased mean free path at higher kinetic energies in combination with the elemental selectivity of the core level spectroscopies in general that has lead to this fact, as it makes it possible to investigate the electronic structure of materials with a substantially reduced surface sensitivity. In this review we demonstrate how HIKE can be used to investigate the interface properties in multilayer systems. Relative intensities of the core level photoelectron peaks and their chemical shifts derived from binding energy changes are found to give precise information on physico-chemical properties and quality of the buried layers. Interface roughening, including kinetic properties such as the rate of alloying, and temperature effects on the processes can be analyzed quantitatively. We will also provide an outline of the theoretical framework that is used to support the interpretation of data. We provide examples from our own investigations of multilayer systems which comprises both systems of more model character and a multilayer system very close to real applications in devices that are considered to be viable alternative to the present read head technology. The experimental data presented in this review is exclusively recorded at the BESSY-II synchrotron at the Helmholtz-Zentrum Berlin fur-Materialien und Energie. This HIKE facility is placed at the bending magnet beamline KMC-1, which makes it different from several other facilities which relies on undulators as the

The electrical properties of oxides fabricated on n-type 3C-SiC (001) and 4H-SiC (0001) epilayers using an advanced oxidation process combining plasma enhanced deposition and rapid postoxidation steps have been investigated. Three gas atmospheres have been studied for the postoxidation steps: N2O, dry, and wet oxygen (H2O). In comparison, additional oxides using postannealing in pure N-2 have been fabricated. The implementation of wet oxygen resulted. in a significant decrease in the interface traps density, in a reduction of oxide fixed charges and in the increased breakdown field in the case of 3C-SiC. In the case of 4H-SiC the postoxidation in N2O is a superior postprocessing step., QC 20100525

Composites based on glass fiber reinforced low styrene emission polyester resins have been widely used over the last 10 years, in order to meet increasingly strict safety regulations, particularly in the pleasure boat industry. Previous studies of their mechanical properties suggested that although these resins are generally more brittle than traditional orthophthalic polyester resins this did not adversely affect the properties commonly used for quality control (short beam shear and tensile failure strength of mat reinforced composites). In the present paper results from a more detailed study of damage behaviour are presented. Tests include fracture toughness (K (Ic) ) tests on resins, fibre/matrix interface energy, detection of composite damage initiation in tension by acoustic emission, composite delamnation (G (Ic) and G (IIc) ), and low energy impact. Overall the results indicate that the low failure strain of low styrene emission resins results in significantly lower composite damage resistance.

Composites based on glass fiber reinforced low styrene emission polyester resins have been widely used over the last 10 years, in order to meet increasingly strict safety regulations, particularly in the pleasure boat industry. Previous studies of their mechanical properties suggested that although these resins are generally more brittle than traditional orthophthalic polyester resins this did not adversely affect the properties commonly used for quality control (short beam shear and tensile failure strength of mat reinforced composites). In the present paper results from a more detailed study of damage behaviour are presented. Tests include fracture toughness (K (Ic) ) tests on resins, fibre/matrix interface energy, detection of composite damage initiation in tension by acoustic emission, composite delamnation (G (Ic) and G (IIc) ), and low energy impact. Overall the results indicate that the low failure strain of low styrene emission resins results in significantly lower composite damage resistance.

Composites based on glass fiber reinforced low styrene emission polyester resins have been widely used over the last 10 years, in order to meet increasingly strict safety regulations, particularly in the pleasure boat industry. Previous studies of their mechanical properties suggested that although these resins are generally more brittle than traditional orthophthalic polyester resins this did not adversely affect the properties commonly used for quality control (short beam shear and tensile failure strength of mat reinforced composites). In the present paper results from a more detailed study of damage behaviour are presented. Tests include fracture toughness (K (Ic) ) tests on resins, fibre/matrix interface energy, detection of composite damage initiation in tension by acoustic emission, composite delamnation (G (Ic) and G (IIc) ), and low energy impact. Overall the results indicate that the low failure strain of low styrene emission resins results in significantly lower composite damage resistance.

This work deals with some fundamental material properties of the hafnia or hafnium oxide and the silicate layer at the Si/HfO2 interface. It is realized that one of the fundamental features of the HfO2 film is that its lowest conduction band states are composed mainly by d states instead of s and p states as is in the case for SiO2. There is only a very small covalent component contributed from Hf d and O 2p states and the Hf-O bond is predominantly ionic. This is the reason for the small band gap and small conduction band offset energy. This feature also gives rise to thermal instabilities and the formation of an interfacial silicate layer. Although the formation of the silicate structure will help to build a more stable interface, long metallic silicide bonds will result as a by-product when the metal oxide reacts with the Si substrate to form this silicate layer. The existence of metallic silicide bonds is one of the major reasons for the observed high-interface trap density of the HfO2/Si structure. Because of the large difference in dielectric constant between the bulk hafnia and interfacial silicate, the electric field will be distributed mainly across the low-K interface layer, which in effect reduces the interface barrier height for electron tunneling injection and the effective breakdown voltage of the low-k layer. (c) 2005 Elsevier B.V. All rights reserved.

This work deals with some fundamental material properties of the hafnia or hafnium oxide and the silicate layer at the Si/HfO2 interface. It is realized that one of the fundamental features of the HfO2 film is that its lowest conduction band states are composed mainly by d states instead of s and p states as is in the case for SiO2. There is only a very small covalent component contributed from Hf d and O 2p states and the Hf-O bond is predominantly ionic. This is the reason for the small band gap and small conduction band offset energy. This feature also gives rise to thermal instabilities and the formation of an interfacial silicate layer. Although the formation of the silicate structure will help to build a more stable interface, long metallic silicide bonds will result as a by-product when the metal oxide reacts with the Si substrate to form this silicate layer. The existence of metallic silicide bonds is one of the major reasons for the observed high-interface trap density of the HfO2/Si structure. Because of the large difference in dielectric constant between the bulk hafnia and interfacial silicate, the electric field will be distributed mainly across the low-K interface layer, which in effect reduces the interface barrier height for electron tunneling injection and the effective breakdown voltage of the low-k layer. (c) 2005 Elsevier B.V. All rights reserved.

This work deals with some fundamental material properties of the hafnia or hafnium oxide and the silicate layer at the Si/HfO2 interface. It is realized that one of the fundamental features of the HfO2 film is that its lowest conduction band states are composed mainly by d states instead of s and p states as is in the case for SiO2. There is only a very small covalent component contributed from Hf d and O 2p states and the Hf-O bond is predominantly ionic. This is the reason for the small band gap and small conduction band offset energy. This feature also gives rise to thermal instabilities and the formation of an interfacial silicate layer. Although the formation of the silicate structure will help to build a more stable interface, long metallic silicide bonds will result as a by-product when the metal oxide reacts with the Si substrate to form this silicate layer. The existence of metallic silicide bonds is one of the major reasons for the observed high-interface trap density of the HfO2/Si structure. Because of the large difference in dielectric constant between the bulk hafnia and interfacial silicate, the electric field will be distributed mainly across the low-K interface layer, which in effect reduces the interface barrier height for electron tunneling injection and the effective breakdown voltage of the low-k layer. (c) 2005 Elsevier B.V. All rights reserved.

An overview is presented of the fracture behaviour and failure mechanisms of composite laminates containing woven fabrics in mode I and mode II delamination and under impact loading. Potential advantages of using woven fabrics as opposed to cross-ply unidirectional prepreg tapes are specifically discussed from the viewpoint of the microstructure/property relationship. Correlations are established between resistance to and tolerance of impact damage and the delamination resistance of composites. Salient differences are identified between composites made from different fibre configurations in terms of the process of damage development, damage modes/states and residual performance after impact damage. The effects of fibre/matrix interface properties influenced by different silane coupling agents on interlaminar fracture and the impact performance of woven-glass-fabric composites are evaluated. The implications of these findings are discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.

An overview is presented of the fracture behaviour and failure mechanisms of composite laminates containing woven fabrics in mode I and mode II delamination and under impact loading. Potential advantages of using woven fabrics as opposed to cross-ply unidirectional prepreg tapes are specifically discussed from the viewpoint of the microstructure/property relationship. Correlations are established between resistance to and tolerance of impact damage and the delamination resistance of composites. Salient differences are identified between composites made from different fibre configurations in terms of the process of damage development, damage modes/states and residual performance after impact damage. The effects of fibre/matrix interface properties influenced by different silane coupling agents on interlaminar fracture and the impact performance of woven-glass-fabric composites are evaluated. The implications of these findings are discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.

An overview is presented of the fracture behaviour and failure mechanisms of composite laminates containing woven fabrics in mode I and mode II delamination and under impact loading. Potential advantages of using woven fabrics as opposed to cross-ply unidirectional prepreg tapes are specifically discussed from the viewpoint of the microstructure/property relationship. Correlations are established between resistance to and tolerance of impact damage and the delamination resistance of composites. Salient differences are identified between composites made from different fibre configurations in terms of the process of damage development, damage modes/states and residual performance after impact damage. The effects of fibre/matrix interface properties influenced by different silane coupling agents on interlaminar fracture and the impact performance of woven-glass-fabric composites are evaluated. The implications of these findings are discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.

The energy level alignment behavior of the widely used materials tris-(8-hydroxyquinoline)aluminum (Alq3) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) is investigated. The Integer Charge Transfer (ICT) model is successfully used to predict their overall behavior at weakly-interacting hybridorganic and organic-organic interfaces, including NTCDA/Alq3 bilayers. The EICT- of NTCDA is measured to be 4.35 eV and the EICT+ of Alq3 is found to be 4.3 eV. The Alq3 films furthermore feature an interface dipole in absence of charge transfer due to the intrinsic dipole of the molecule and ordering effects.