Dissertations / Theses on the topic 'Bendigo Bank'

Steady-state and transient surface photovoltages in undoped GaN are studied in various environments (air, nitrogen, oxygen, vacuum) at room temperature and 400 K with a Kelvin probe attached to an optical cryostat. The results are explained within a phenomenological model accounting for the accumulation of photo-generated holes at the surface, capture of free electrons from the bulk over the near-surface potential barrier, and emission of electrons from surface states into the bulk. Mechanisms of surface photovoltage are discussed in detail. Photoadsorption and photodesorption of negatively charged species will either increase or decrease the surface potential and thus band bending. Oxygen is the assumed species responsible for the SPV changes in air ambient during continuous UV illumination. This variation in SPV will be confirmed with photoluminescence measurements.

This dissertation details the study of band bending in n- and p-type GaN samples with a Kelvin probe utilizing different illumination geometries, ambients (air, oxygen, vacuum 10-6 mbar), and sample temperatures (77 – 650 K). The Kelvin probe, which is mounted inside an optical cryostat, is used to measure the surface potential. Illumination of the GaN surface with band-to-band light generates electron-hole pairs, which quickly separate in the depletion region due to a strong electric field caused by the near-surface band bending. The charge that is swept to the surface reduces the band bending and generates a surface photovoltage (SPV). Information about the band bending can be obtained by fitting the SPV measurements with a thermionic model based on the emission of charge carriers from bulk to surface and vice versa. The band bending in freestanding n-type GaN templates has been evaluated. The Ga-polar and N-polar surfaces exhibit upward band bending of about 0.74 and 0.57 eV, respectively. The surface treatment also plays a major role in the SPV behavior, where the SPV for mechanical polished surfaces restores faster than predicted by a thermionic model in dark. When measuring the photoluminescence (PL) signal, the PL from mechanically polished surfaces was about 4 orders of magnitude smaller than the PL from chemically mechanically polished surfaces. The PL and SPV behaviors were explained by the presence of a large density of defects near the surface, which quench PL and aid in the restoration of the SPV via electron hopping between defects. Temperature-dependent SPV studies have also been performed on doped n- and p-type GaN samples. In Si-doped n-type GaN, the estimated upward band bending was about 1 eV at temperatures between 295 and 500 K. However, in p-type GaN, the downward band bending appeared to increase with increasing temperature, where the magnitude of band bending increased from 0.8 eV to 2.1 eV as the temperature increased from 295 to 650 K. It appears that heating the p-type GaN samples allows for band bending values larger than 1 eV to fully restore. Pre-heating of samples was of paramount importance to measure the correct value of band bending in p-type GaN. The slope of the dependence of the SPV on excitation intensity at low temperatures was larger than expected; however, once the temperature exceeded 500 K, the slope began to reach values that are in agreement with a thermionic model.

Prior studies have reported differences in lower back biomechanics during activities of daily living between individuals with and without chronic low back pain (LBP). Nevertheless, the literature on lower back biomechanics of patients with non-chronic LBP is scant. Therefore, the objective of this study, as the first step towards future prospective studies, was to investigate the lower back biomechanics in patients with non-chronic LBP. Case-control studies were conducted wherein measures of lumbo-pelvic coordination during bending and return tasks as well as measures of mechanical demand on the lower back during lifting tasks in the sagittal plane were investigated between patients with non-chronic LBP and matched asymptomatic individuals. Patients were enrolled into the study at the non-chronic stage of their LBP. We found distinct difference in measures of lumbo-pelvic coordination as well as mechanical demands on the lower back between patients with non-chronic LBP and controls. Reduced lumbar range of flexion and slower task pace as well as the more in-phase and less variable lumbo-pelvic coordination observed in patients with non-chronic low back pain, may be the result of a neuromuscular adaptation to reduce the forces and deformation in the lower back tissues and avoid pain aggravation. Such a neuromuscular adaptation, however, resulted in a larger shearing demand on the lower back. Persistent abnormal lumbo-pelvic coordination might play a role in transition to chronic stage or recurrence of LBP. However, such inferences need to be further investigated using prospective studies as well as clinical trials involving a combination of physical and psychological treatments aimed at correction of lumbo-pelvic coordination.

Rotary draw bending, which has very good flexibility and easy tooling, is one of the most preferred bending types for tubular profiles. Cross-section distortion and the spring-back phenomena are commonly faced problems in bending processes. Spring-back is the inevitable problem that is to be solved by manufacturer, generally by overbending. For hollow tubes cross-section distortion is another difficulty since using hollow tubes results in higher strain rates and distortions. During the process the thickness of the hollow tube at the inner surface, which is contacting with the die, increases and the thickness of the tube at the outer surface decreases. Wrinkling is another important defect that occurs at the inner surface of the tube in large diameter thin walled tube bendings. This research compares the experimental results with the finite element analysis of the rotary draw bending process. The aim is to obtain bending characteristics of the two material types, SS304 and St37 and so, to reduce the number of the bending in manufacturing. The main parameters in rotary draw bending process are the bending angle, bend radius, material properties and the geometry of the tube that is to be bent. In this study, to deal with the process, two different materials, three different bending angles and three different tube geometries are used in experiments as well as in finite element analysis. In finite element analysis explicit method is used. It is seen that the experimental results are in good agreement with the numerical results.

An investigation into the processes taking place at the surface interface of ferroelectric Pb(Zr1-x,Tix)O3 immersed in metal salt solution under ultraviolet illumination is presented. The semiconducting and switchable dipolar nature of this material allows the spatial separation and control of photo-induced reduction and oxidation across its surface interface. These properties can be of application in novel techniques such as the controlled growth of metallic nanoparticles across specific polar domains. 70nm thick Pb(Zr0.3,Ti0.7)O3 samples, PZT(30/70), are manufactured using the sol gel methodology, two crystallographic orientations being produced. The orientation being controlled by the substrate used; Si was used for [111] orientation and MgO for [100]. The initial work with wideband ultraviolet light shows that the reduction and growth of silver on the PZT surface is greatly influenced by the structure of the film. The crystallographic orientation of the film affects metal deposition such that on [111] films the metal deposits only on positive domains, where as the [100] films experience deposition on both positive and negative domains. This is shown to be due to the difference in width of the space charge region, Δw = 4.4nm, between the [111] and [100] samples so that the negative domain on [100] samples have 10 19 times higher chance of electron tunnelling compared to the [111]. It is also shown that grain boundaries have the greatest effect on the growth of metal, with a metal cluster growth rate 51 times faster than elsewhere on the surface. This increased rate of growth is due to the effect a grain boundary has on the surrounding area, the energy band bending at the boundary attracting charge carriers from the grains around it. The interface types ranked from greatest to lowest influence are grain boundaries, positive domains, domain boundaries and finally interphase boundaries.ii It is shown that the stern layer, strongly adsorbed charged ions of opposite sign to the surface charge, at the PZT/solution interface act as an insulating layer to metal reduction. The accumulation of photoexcited charge carriers at points along grain boundaries causes the surface potential gradient to alter and allows metal reduction and thus clusters to nucleate. The energy required to cause this variation is investigated by use of narrow band, 5nm bandwidth, ultraviolet. For energy from 4.4eV to 5 eV, it is found there is an increase in the average silver cluster cross sectional area by a ratio of ca 1.6 to 1 for both the [111] and [100] orientations of PZT. Finally it is shown that the type of metal salt used in the photochemical process affects the type of reaction that takes place at the sample surface. For a cation to reduce on positive domains its reduction potential needs to be below the bottom edge of the conduction band of PZT. Chloride salts, that sit above the conduction band, cause decomposition of the negative domains. Use is made of these effects to find the position of the bottom of the conduction band for PZT. It is found that across similar [111] PZT samples FeCl2 can both reduce on positive domains and decompose negative domains, this puts the bottom of the conduction band for PZT(30/70) between 4.06 and 4.36 eV from vacuum. It is also discovered that the type of anion affects the decomposition of the negative domains. Nitrate salts with cations above the conduction band cause no decomposition whereas chlorides do. The decomposition is shown to be the loss of Pb from the negative surface.

This thesis concerns new hydrogen- and polarity-related effects in the photoluminescence of ZnO single crystal wafers and the relationship between surface electron accumulation and surface hydroxyl coverage on different ZnO surfaces. A comparative study of the low temperature photoluminescence of various types of hydrothermal and melt-grown ZnO wafers revealed several new hydrogen-related exciton recombination lines and a number of consistent polarity-related differences in the PL emission from different crystallographic surfaces. Temperature-dependent PL measurements were extensively used to distinguish the ground and excited state transitions involved in these effects. ZnO samples of different surface polarity were annealed in oxygen and nitrogen gases and in hydrogen-containing forming gas mixtures in an attempt to identify the origin of these new PL features. The well known aluminium-related I_₆ recombination line was resolved into two separate features in hydrothermal ZnO, and the new component I6-H (3.36081 eV) was found to repeatedly quench and then re-emerge after annealing in oxygen and forming gas, respectively. A model involving an aluminium - lithium - hydrogen defect complex was proposed for I6-H and further tested via hydrogen and deuterium implantation experiments on hydrothermal ZnO wafers with different lithium concentrations. These experiments also provided evidence for the involvement of a different lithium-hydrogen defect complex in other hydrogen-related emission lines I₄b,c (3.36219 eV and 3.36237 eV) unique to hydrothermal ZnO. In addition, a broad Gaussian-shaped feature observed in the near-band-edge PL emission from the O-polar (000‾1), a-plane (11‾20) and r-plane (1‾102) faces of ZnO was shown to be surface sensitive and also related to hydrogen. The involvement of hydrogen in the chemical and electronic properties of different ZnO surfaces was also investigated. The thermal stability of the hydroxyl termination and the associated downward surface band bending on the polar and non-polar surfaces of ZnO was studied by synchrotron and real-time photoelectron spectroscopy, both during and after annealing and subsequent H₂O/H₂ dosing in ultra-high vacuum conditions. On the O-polar face, the band bending could be reversibly switched over a range of approximately 0.8 eV by adjusting the surface H-coverage using simple UHV heat treatments and atmospheric exposure. A transition from electron accumulation to electron depletion on the O-polar face was observed at a H-coverage of approximately 0.9 monolayers. In contrast, the downward band bending on the Zn-polar face was significantly more resilient and electron-depleted surfaces could not be prepared by heat treatment alone. This was also the case for in situ cleaving in UHV conditions which failed to produce hydroxyl-free surfaces due to migration of hydrogen from the bulk to the cleaved surface. Interestingly, the thermal stability of the hydroxyl termination on the a-plane (11‾20) and m-plane (10‾10) surfaces was signiifcantly lower than on the polar faces due to the availability of a lower energy desorption pathway and the electrostatic stability of these non-polar surfaces in their clean, bulk terminated form. The surface band bending on the non-polar ZnO surfaces was also found to be directly related to their OH coverage with a transition from downward to upward band bending, similar to that observed on the O-polar face, as the OH coverage was reduced. Thermal admittance spectroscopy and deep level transient spectroscopy was used to investigate the effect of lithium removal on the defect nature of hydrothermal ZnO. A number of new defects were introduced by the high temperature (1100-1400°C) annealing/re-polishing process used to reduce the lithium concentration, particularly E₁₉₀ (also known as T2) which is thought to be related to Zn vacancies. Significantly, both the E₅₀ defect level and the I6-H PL emission line were absent after lithium (and hydrogen) removal suggesting an association of both these features with the same aluminium - lithium - hydrogen defect complex.

The development of gallium nitride (GaN) light emitting devices has reached extraordinary echelons. As such, the characterization and analysis of the behavior of GaN materials is essential to the advancement of GaN technology. In this thesis, the effect of temperature on the optical and electrical properties of p-type GaN is investigated. The GaN samples used in this work were grown by various methods and studied by Kelvin probe and photoluminescence (PL) techniques. Specifically, the surface photovoltage (SPV) behavior and PL data were analyzed at different temperatures and illumination intensities. Using the SPV results, we show that p-type GaN exhibits n-type conductivity at low temperatures (80 K). If the sample is heated beyond a characteristic temperature, TC, the conductivity reverts to p-type. This temperature of conversion can be tuned by varying the illumination intensity. We explain this conductivity conversion using a simple, one-acceptor phenomenological model. Temperature-dependent PL measurements taken on Mg-doped p-type GaN layers show abrupt and tunable thermal quenching of the PL intensity. This effect is explained by a more complex model but with the same assertions, that the system must undergo a change in conductivity at low temperatures and under UV illumination. It is necessary to understand the observed behaviors, since the implications of such could have an effect on the performance of devices containing p-type GaN materials.

Samhället ändras konstant men detta innebär inte bara en förändring för människorna i samhället utan också att nya krav ställs på konstruktionen som brukas av människorna. Många byggnadskonstruktioner kan därmed behöva en förstärkning efter en viss tid. Behovet av en förstärkning kan bero på flera orsaker exempelvis ändrat nyttjande. Det är mer fördelaktigt med en förstärkning av konstruktionen än att den rivs ner och byts ut för att klara av dagens krav. Syftet med detta examensarbete är att undersöka förstärkning av betongkonstruktioner med hjälp av kolfiberkomposit. I rapporten presenteras beräkningar som gjordes för att undersöka tillökningen i böjoch tvärkraftskapacitet efter en utförd förstärkning. Parallellt med beräkningarna kontrollerades och utvecklades befintliga mallar som finns för denna metod. För att kunna uppnå syftet undersöktes två hypotetiska betongkonstruktioner. Ena konstruktionen är en plattramsbro som modellerades i FEM programmet Brigade Standard. Beräkningar på plattramsbron gjordes med avseende på böjande moment. Den andra konstruktionen som undersöktes är en T-balk som är en del utav ett bjälklag. På T-balken granskades tvärkraftskapaciteten innan och efter en utförd förstärkning med kolfiber. I resultatet redovisas mängden kolfiber som erfordras för att uppnå önskad kapacitet hos konstruktionerna. I resultatet redogörs också kapaciteten som uppnås efter kolfiberförstärkningen.
The society changes constantly, but this does not only affect the inhabitants of the society, but also that new demands are made on the construction used by the people. Many constructions may therefore require reinforcement after a certain amount of time. The need for reinforcement may be due many different reasons for example to altered use, corrosion to internal reinforcement or may be due to design errors, accidents or new standards. It is more beneficial to reinforce the structure than to tear it down and replace it to meet current requirements. The purpose of this thesis is to investigate carbon fiber reinforced polymer, CFRP, as a method to strengthen concrete structures. The report presents calculations that were made to investigate the increase in bending and shear capacity after a performed reinforcement. Alongside the calculations, existing templates for this method were checked and developed. In order to achieve the purpose, two hypothetical concrete structures were investigated. One design is a frame bridge modeled in the FEM program Brigade Standard. Calculations on the frame bridge were made with respect to bending. The other construction that was investigated is a T-beam. On the Tbeam, shear capacity was examined before and after reinforced carbon fiber reinforcement. The result present the amount of carbon fiber required to achieve the desired capacity of the structures. The result also describes the capacity achieved after carbon fiber reinforcement.

There is an understanding of surface photovoltage (SPV) behavior for GaN, yet little is known about the SPV behavior for AlGaN. In this work, a Kelvin probe was used to measure the SPV for p-type AlGaN. Very slow SPV transients were found in AlGaN, which could not be explained with a simple thermionic model. A possible explanation of this behavior is the segregation of impurities to the surface, which causes significant reduction of the depletion region width (down to 2 nm), with carrier tunneling and hopping becoming the dominant mechanisms responsible for the SPV transients. To verify this assumption, the near-surface defective region (about 40 nm) has been removed through the ICP-RIE process. After the etching, the SPV transients became fast and increased in magnitude by about 0.6 eV. By using the thermionic model, band bending was estimated to be -1 eV.

This work examines extended, point, and surface defects in GaN by means of electric force microscopy, photoluminescence and deep-level transient spectroscopy. Modeling of the surface band bending, its origin, and the effects of fabrication processing steps are discussed in the first part of the dissertation. Experimental results indicate that spontaneous polarization does not play a predominant role in GaN band bending. An increase of surface band bending due to annealing and etching was observed, while passivation did not produce changes. However, passivation did reduce reverse-bias leakage current by one to two orders of magnitude in GaN Schottky diodes. The optical properties of GaN were found to be sensitive to fabrication processing steps, most likely due to changes in the total density of surface states.The second part of this dissertation concerns the reduction of extended defects and associated deep levels in layers of GaN grown on different templates. Templates employing a low temperature GaN nucleation layer, epitaxial lateral overgrowth, and SiNx nanonetwork are compared in terms of deep level concentrations in the resulting GaN films. The concentrations of two types of traps, A (Ec-ET ~ 0.54-0.58 eV) and B (Ec-ET ~ 0.20-0.24 eV), were the highest for the sample with a low temperature nucleation layer and lowest for a sample with a 6 min SiNx deposition time. We surmise that the defects responsible for the dominant trap A are located along dislocation lines and form clusters.In the last part we investigate the piezoelectric and ferroelectric properties of PZT in Pb(Zr, Ti)O3(PZT)/GaN structures, and the effects of interface states. Sol-gel derived thin PZT films on GaN and Pt/Ti/SiO2/Si surfaces were studied by piezoresponse force microscopy (PFM), where quantitative characterization of piezoelectric properties of PZT films was performed. Superior piezoelectric properties of PZT/GaN/sapphire structures as compared to PZT/ Pt/Ti/SiO2/Si structures were observed and explained by a different preferred orientation of PZT. Despite the possible existence of a strong depolarization field at the PZT/GaN interface, we confirm with PFM the presence of a remanent polarization in PZT/GaN/sapphire structures.

A mezzanine is an extra floor which is used to be able to use more area both below and above the mezzanine plane. The Mezzanine is used in many various places, but this thesis is focusing on a mezzanine which will be used in in warehouses. A mezzanine concept is designed to fulfill a need within Brännhylte lagersystems AB, which is a mezzanine plane with Z-160 beams as a main component. A requirement specification is developed to help understanding what requirement the mezzanine should fulfill. With the help of the requirement specification a mezzanine concept is developed which fulfill these requirements. Because the mezzanine will have to withstand a lot of forces from different loads and people walking on it therefore it must be steady and secure. The maximum forces when the mezzanine reaches its maximum bending limit of beam length divided by 400 is calculated. This information can be used in the future to adapt the mezzanine depending on what weight it needs be able to withstand.
Ett entresolplan är ett extra våningsplan som man kan montera upp för att utnyttja mer yta både under och över entresolplanet. En entresol används på många olika platser, detta examensarbete fokuserar dock på ett entresolplan som kommer att användas i lagerlokaler. Ett entresolkoncept designades för att uppfylla ett behov ifrån Brännhylte lagersystems AB som ville ha ett entresolplan som använder sig utav Z-160 balkar som huvudkomponent. En kravspecifikation utvecklades för att få konkreta uppgifter vad som skulle uppnås med entresolen. Med hjälp av kravspecifikationen utvecklades ett entresolkoncept som uppfyller dessa krav. Eftersom entresolen kommer att utsättas för massa olika vikter under användning samt att människor ska kunna gå på den så är den tvungen att vara tillräcklig stadig för att kunna användas säkert. Därför analyserades den maximala kraften som entresolplanet kan klara av innan den når sin nedböjningsgräns som är balklängden delat på 400. För att den informationen ska kunna användas i framtiden och för att kunna anpassa entresolen utifrån hur mycket vikt man vill att den ska klara av.

The Diploma Thesis deals with the technology of manufacturing the titan exhaust for a two-stroke engine. It includes a description of the manufacturing procedure. It analyzes in detail the forming issue of sheet-metal parts in order to eliminate the spring-back effect, and it finds possible solutions to this problem.

A model is presented to use normalized multi-linear tension and compression material characteristics of strain-hardening textile reinforced concrete and derive closed form expressions for predicting moment-curvature capacity. A set of design equations are derived and simplified for use in spreadsheet based applications. The model is applicable for both strain-softening and strainhardening materials. The predictability of the simplified model is checked by model calibration and development of design charts for moment capacity and stress developed throughout the cross section of a flexural member. Model is calibrated by predicting the results of Alkali Resistant Glass and Polyethylene fabrics. A case for the flexural design of Glass Fiber Reinforced Concrete (GFRC) specimen as a simply supported beam subjected to distributed load is used to demonstrate the design procedure.

Multilayer epitaxial graphene has been shown to contain "massless Dirac fermions" and is believed to provide a possible route to industrial-scale graphene electronics. We used scanning tunneling microscopy (STM) and spectroscopy (STS) in high magnetic fields to obtain local information on these fermions. A new STS technique was developed to directly measure graphene's energy-momentum relationship and resulted in the highest precision measurement of graphene's Dirac cone. STS spectra similar to ideal graphene were observed, but additional anomalies were also found. Extra peaks and an asymmetry between electron and hole states were shown to be caused by the work function difference between the Iridium STM tip and graphene. This tip effect was extracted using modeled potentials and performing a least square fit using degenerate perturbation theory on graphene's eigenstates solved in the symmetric gauge. Defects on graphene were then investigated and magnetic field effects were shown to be due to a mixture of potential effect from defects and the tip potential. New defect states were observed to localize around specific defects, and are believed to interact with the STM tip by Stark shifting in energy. This Stark shift gives a direct measurement of the capacitive coupling between the tip and graphene and agrees with the modeled results found when extracting the tip potential.

Der Einfluss der Modifikation der technologisch relevanten GaAs(100) Oberfläche durch Chalkogene, i.e. Selen, Schwefel und Tellur, wird in dieser Arbeit untersucht. Es wird ein Modell vorgestellt, das die Eigenschaften der modifizierten Oberfläche beschreibt. In einem zweiten Schritt werden die so modifizierten Oberflächen mit Metallen unterschiedlicher Reaktivität und verschiedenen Elektronegativitäten bedampft. Die Bandbreite dieser Eigenschaften wird durch die Metalle Indium und Silber, das Alkalimetall Natrium, das Erdalkalimetall Magnesium und das Halbmetall Antimon abgebildet. Die Untersuchung des Einflusses der Chalkogene auf die chemischen Eigenschaften und die Barrierenhöhe der Metall/GaAs(100) Grenzfläche bilden einen weiteren Schwerpunkt. Die Änderung der Barrierenhöhe wird dabei mit Hilfe des Modells metallinduzierter Bandlückenzustände (metal induced gap states) erklärt. Als experimentelle Techniken werden Photoemissionsspektroskopie, Raman Spektroskopie und Strom-Spannungsmessungen verwendet
The influence of a modification of the technological relevant GaAs(100) surface by chalcogens, i.e. selenium, sulphur and tellurium, is evaluated in this work. A model is proposed, which describes the properties of the modified surface. In a second step metals of different reactivity and electronegativity have been evaporated onto these modified surfaces. Among these materials were the metals indium and silver, the alkali metal sodium, the earth alkali metal magnesium and the half metal antimony. The investigation of the influence of chalcogens on the chemical properties and the barrier height of the metal/GaAs(100) interface is another point of interest. The change in barrier height is explained by the model of metal induced gap states (MIGS). Photoemission spectroscopy, Raman spectroscopy and current-voltage-measurement have been used as experimental techniques

In der vorliegenden Arbeit werden Holzwerkstoffe im statischen Biegeversuch und im Schlagbiegeversuch vergleichend geprüft. Ausgewählte Holzwerkstoffe werden thermisch geschädigt, zudem wird eine relevante Kerbgeometrie geprüft. Ziel der Untersuchungen ist die Eignung verschiedenartiger Werkstoffe für den Einsatz in sicherheitsrelevanten Anwendungen mit Schlagbelastungen zu prüfen. Hierzu werden zunächst die Grundlagen der instrumentierten Schlagprüfung und der Holzwerkstoffe erarbeitet. Der Stand der Technik wird dargelegt und bereits durchgeführte Studien werden analysiert. Darauf aufbauend wird eine eigene Prüfeinrichtung zur zeitlich hoch aufgelösten Kraft-Beschleunigungs-Messung beim Schlagversuch entwickelt. Diese wird anhand verschiedener Methoden auf ihre Eignung und die Messwerte auf Plausibilität geprüft. Darüber hinaus wird ein statistisches Verfahren zur Überprüfung auf ausreichende Stichprobengröße entwickelt und auf die durchgeführten Messungen angewendet. Anhand der unter statischer und schlagartiger Biegebeanspruchung ermittelten charakteristischen Größen, wird ein Klassenmodell zum Werkstoffvergleich und zur Werkstoffauswahl vorgeschlagen. Dieses umfasst integral die mechanische Leistungsfähigkeit der geprüften Holzwerkstoffe und ist für weitere Holzwerkstoffe anwendbar. Abschließend wird, aufbauend auf den gewonnenen Erkenntnissen, ein Konzept für die Bauteilprüfung unter Schlagbelastung für weiterführende Untersuchungen vorgeschlagen
In the present work wood-based materials are compared under static bending load and impact bending load. Several thermal stress conditions are applied to selected materials, furthermore one relevant notch geometry is tested. The objective of these tests is to investigate the suitability of distinct wood materials for security relevant applications with the occurrence of impact loads. For this purpose the basics of instrumented impact testing and wood-based materials are acquired. The state of the technology and a comprehensive analysis of original studies are subsequently presented. On this basis an own impact pendulum was developed to allow force-acceleration measurement with high sample rates. The apparatus is validated by several methods and the achieved signals are tested for plausibility. A general approach of testing for adequate sample size is implemented and applied to the tested samples. Based on the characteristic values of the static bending and impact bending tests a classification model for material selection and comparison is proposed. The classification model is an integral approach for mechanical performance assessment of wood-based materials. In conclusion a method for impact testing of components (in future studies) is introduced

Der Einfluss der Modifikation der technologisch relevanten GaAs(100) Oberfläche durch Chalkogene, i.e. Selen, Schwefel und Tellur, wird in dieser Arbeit untersucht. Es wird ein Modell vorgestellt, das die Eigenschaften der modifizierten Oberfläche beschreibt. In einem zweiten Schritt werden die so modifizierten Oberflächen mit Metallen unterschiedlicher Reaktivität und verschiedenen Elektronegativitäten bedampft. Die Bandbreite dieser Eigenschaften wird durch die Metalle Indium und Silber, das Alkalimetall Natrium, das Erdalkalimetall Magnesium und das Halbmetall Antimon abgebildet. Die Untersuchung des Einflusses der Chalkogene auf die chemischen Eigenschaften und die Barrierenhöhe der Metall/GaAs(100) Grenzfläche bilden einen weiteren Schwerpunkt. Die Änderung der Barrierenhöhe wird dabei mit Hilfe des Modells metallinduzierter Bandlückenzustände (metal induced gap states) erklärt. Als experimentelle Techniken werden Photoemissionsspektroskopie, Raman Spektroskopie und Strom-Spannungsmessungen verwendet.
The influence of a modification of the technological relevant GaAs(100) surface by chalcogens, i.e. selenium, sulphur and tellurium, is evaluated in this work. A model is proposed, which describes the properties of the modified surface. In a second step metals of different reactivity and electronegativity have been evaporated onto these modified surfaces. Among these materials were the metals indium and silver, the alkali metal sodium, the earth alkali metal magnesium and the half metal antimony. The investigation of the influence of chalcogens on the chemical properties and the barrier height of the metal/GaAs(100) interface is another point of interest. The change in barrier height is explained by the model of metal induced gap states (MIGS). Photoemission spectroscopy, Raman spectroscopy and current-voltage-measurement have been used as experimental techniques.

Organische Farbstoffe mit einem konjugierten pi-Elektronen System zeigen überwiegend ein halbleitendes Verhalten. Daher sind sie potentielle Materialien für elektronische und optoelektronische Anwendungen. Erste Anwendungen in Flachbildschirmen sind bereits in (noch) geringen Mengen auf dem Markt. Die kontrollierte Dotierung anorganischer Halbleiter bereitete die Basis für den Durchbruch der bekannten Halbleitertechnologie. Die Kontrolle des Leitungstypes und der Lage des Fermi-Niveaus erlaubte es, stabile pn-Übergänge herzustellen. LEDs können daher mit Betriebsspannungen nahe dem thermodynamischen Limit betrieben werden (ca. 2.5V für eine Emission im grünen Spektralbereich). Im Gegensatz dazu bestehen organische Leuchtdioden (OLEDs) typischerweise aus einer Folge intrinsischer Schichten. Diese weisen eine ineffiziente Injektion aus Kontakten und eine relative geringe Leitfähigkeit auf, welche mit hohen ohmschen Verlusten verbunden ist. Andererseits besitzen organische Materialien einige technologische Vorteile, wie geringe Herstellungskosten, große Vielfalt der chemischen Verbindungen und die Möglichkeit sie auf flexible große Substrate aufzubringen. Sie unterscheiden sich ebenso in einigen fundamentalen physikalischen Parametern wie Brechungsindex, Dielektrizitätskonstante, Absorptionskoeffizient und Stokes-Verschiebung der Emissionswellenlänge gegenüber der Absorption. Das Konzept der Dotierung wurde für organische Halbleiter bisher kaum untersucht und angewandt. Unser Ziel ist die Erniedrigung der Betriebsspannung herkömmlicher OLEDs durch den Einsatz der gezielten Dotierung der Transportschichten mit organischen Molekülen. Um die verbesserte Injektion aus der Anode in die dotierte Löchertransportschicht zu verstehen, wurden UPS/XPS Messungen durchgeführt (ultraviolette und Röntgen-Photoelektronenspektroskopie). Messungen wurden an mit F4-TCNQ dotiertem Zink-Phthalocyanin auf ITO und Gold-Kontakten durchgeführt. Die Schlussfolgerungen aus den Experimenten ist, das (i) die Fermi-Energie sich durch Dotierung dem Transportniveau (also dem HOMO im Falle der vorliegenden p-Dotierung) annähert, (ii) die Diffusionspannung an der Grenzfläche durch Dotierung entsprechend verändert wird, und (iii) die Verarmungszone am Kontakt zum ITO sehr dünn wird. Der Kontakt aus organischem Material und leitfähigem Substrat verhält sich also ganz analog zum Fall der Dotierung anorganischer Halbleiter. Es entsteht ein stark dotierter Schottky-Kontakt dessen schmale Verarmungszone leicht durchtunnelt werden kann (quasi-ohmscher Kontakt). Die Leistungseffizienz von OLEDs mit dotierten Transportschichten konnte sukzessive erhöht werden, vom einfachen 2-Schicht Design mit dotiertem Phthalocyanine als Löchertransportschicht, über einen 3-Schicht-Aufbau mit einer Elektronen-Blockschicht bis zu OLEDs mit dotierten 'wide-gap' Löchertransport-Materialien, mit und ohne zusätzlicher Schicht zur Verbesserung der Elektroneninjektion. Sehr effiziente OLEDs mit immer noch niedriger Betriebsspannung wurden durch die Dotierung der Emissionsschicht mit Molekülen erhöhter Photolumineszenzquantenausbeute (Laser-Farbstoffe) erreicht. Eine optimierte LED-Struktur weist eine Betriebsspannung von 3.2-3.2V für eine Lichtemission von 100cd/m2 auf. Diese Resultate entsprechen den zur Zeit niedrigsten Betriebsspannungen für OLEDs mit ausschließlich im Vakuum aufgedampften Schichten. Die Stromeffizienz liegt bei ca. 10cd/A, was einer Leistungseffizienz bei 100cd/m2 von 10lm/W entspricht. Diese hohe Leistungseffizienz war nur möglich durch die Verwendung einer Blockschicht zwischen der dotierten Transportschicht und der Lichtemissions-Schicht. Im Rahmen der Arbeit konnte gezeigt werden, dass die Dotierung die Betriebsspannungen von OLEDs senken kann und damit die Leistungseffizienz erhöht wird. Zusammen mit einer sehr dünnen Blockschicht konnte einen niedrige Betriebsspannung bei gleichzeitig hoher Effizienz erreicht werden (Blockschicht-Konzept)
Organic dyes with a conjugated pi-electron system usually exhibit semiconducting behavior. Hence, they are potential materials for electronic and optoelectronic devices. Nowadays, some applications are already commercial on small scales. Controlled doping of inorganic semiconductors was the key step for today's inorganic semiconductor technology. The control of the conduction type and Fermi-level is crucial for the realization of stable pn-junctions. This allows for optimized light emitting diode (LED) structures with operating voltages close to the optical limit (around 2.5V for a green emitting LED). Despite that, organic light emitting diodes (OLEDs) generally consist of a series of intrinsic layers based on organic molecules. These intrinsic organic charge transport layers suffer from non-ideal injection and noticeable ohmic losses. However, organic materials feature some technological advantages for device applications like low cost, an almost unlimited variety of materials, and possible preparation on large and flexible substrates. They also differ in some basic physical parameters, like the index of refraction in the visible wavelength region, the absorption coefficient and the Stokes-shift of the emission wavelength. Doping of organic semiconductors has only been scarcely addressed. Our aim is the lowering of the operating voltages of OLEDs by the use of doped organic charge transport layers. The present work is focused mainly on the p-type doping of weakly donor-type molecules with strong acceptor molecules by co-evaporation of the two types of molecules in a vacuum system. In order to understand the improved hole injection from a contact material into a p-type doped organic layer, ultraviolet photoelectron spectroscopy combined with X-ray photoelectron spectroscopy (UPS/XPS) was carried out. The experimental results of the UPS/XPS measurements on F4-TCNQ doped zinc-phthalocyanine (ZnPc) and their interpretation is given. Measurements were done on the typical transparent anode material for OLEDs, indium-tin-oxide (ITO) and on gold. The conclusion from these experiments is that (i) the Fermi-energy comes closer to the transport energy (the HOMO for p-type doping), (ii) the built-in potential is changed accordingly, and (iii) the depletion layer becomes very thin because of the high space charge density in the doped layer. The junction between a doped organic layer and the conductive substrate behaves rather similar to a heavily doped Schottky junction, known from inorganic semicondcutor physics. This behavior favors charge injection from the contact into the organic semiconductor due to tunneling through a very small Schottky barrier (quasi-ohmic contact). The performance of OLEDs with doped charge transport layers improves successively from a simple two-layer design with doped phthalocyanine as hole transport layer over a three-layer design with an electron blocking layer until OLEDs with doped amorphous wide gap materials, with and without additional electron injection enhancement and electron blocking layers. Based on the experience with the first OLEDs featuring doped hole transport layers, an ideal device concept which is based on realistic material parameters is proposed (blocking layer concept). Very high efficient OLEDs with still low operating voltage have been prepared by using an additional emitter dopant molecule with very high photoluminescence quantum yield in the recombination zone of a conventional OLED. An OLED with an operating voltage of 3.2-3.2V for a brightness of 100cd/m2 could be demonstrated. These results represent the lowest ever reported operating voltage for LEDs consisting of exclusively vacuum sublimed molecular layers. The current efficiency for this device is above 10cd/A, hence, the power efficiency at 100cd/m2 is about 10lm/W. This high power efficiency could be achieved by the use of a blocking layer between the transport and the emission layer

Organic semiconductors are a new key technology for large-area and flexible thin-film electronics. They are deposited as thin films (sub-nanometer to micrometer) on large-area substrates. The technologically most advanced applications are organic light emitting diodes (OLEDs) and organic photovoltaics (OPV). For the improvement of performance and efficiency, correct modeling of the electronic processes in the devices is essential. Reliable characterization and validation of the electronic properties of the materials is simultaneously required for the successful optimization of devices. Furthermore, understanding the relations between material structures and their key characteristics opens the path for innovative material and device design. In this thesis, two material characterization methods are developed, respectively refined and applied: a novel technique for measuring the charge carrier mobility μ and a way to determine the ionization energy IE or the electron affinity EA of an organic semiconductor. For the mobility measurements, a new evaluation approach for space-charge limited current (SCLC) measurements in single carrier devices is developed. It is based on a layer thickness variation of the material under investigation. In the \"potential mapping\" (POEM) approach, the voltage as a function of the device thickness V(d) at a given current density is shown to coincide with the spatial distribution of the electric potential V(x) in the thickest device. On this basis, the mobility is directly obtained as function of the electric field F and the charge carrier density n. The evaluation is model-free, i.e. a model for μ(F, n) to fit the measurement data is not required, and the measurement is independent of a possible injection barrier or potential drop at non-optimal contacts. The obtained μ(F, n) function describes the effective average mobility of free and trapped charge carriers. This approach realistically describes charge transport in energetically disordered materials, where a clear differentiation between trapped and free charges is impossible or arbitrary. The measurement of IE and EA is performed by characterizing solar cells at varying temperature T. In suitably designed devices based on a bulk heterojunction (BHJ), the open-circuit voltage Voc is a linear function of T with negative slope in the whole measured range down to 180K. The extrapolation to temperature zero V0 = Voc(T → 0K) is confirmed to equal the effective gap Egeff, i.e. the difference between the EA of the acceptor and the IE of the donor. The successive variation of different components of the devices and testing their influence on V0 verifies the relation V0 = Egeff. On this basis, the IE or EA of a material can be determined in a BHJ with a material where the complementary value is known. The measurement is applied to a number of material combinations, confirming, refining, and complementing previously reported values from ultraviolet photo electron spectroscopy (UPS) and inverse photo electron spectroscopy (IPES). These measurements are applied to small molecule organic semiconductors, including mixed layers. In blends of zinc-phthalocyanine (ZnPc) and C60, the hole mobility is found to be thermally and field activated, as well as increasing with charge density. Varying the mixing ratio, the hole mobility is found to increase with increasing ZnPc content, while the effective gap stays unchanged. A number of further materials and material blends are characterized with respect to hole and electron mobility and the effective gap, including highly diluted donor blends, which have been little investigated before. In all materials, a pronounced field activation of the mobility is observed. The results enable an improved detailed description of the working principle of organic solar cells and support the future design of highly efficient and optimized devices
Organische Halbleiter sind eine neue Schlüsseltechnologie für großflächige und flexible Dünnschichtelektronik. Sie werden als dünne Materialschichten (Sub-Nanometer bis Mikrometer) auf großflächige Substrate aufgebracht. Die technologisch am weitesten fortgeschrittenen Anwendungen sind organische Leuchtdioden (OLEDs) und organische Photovoltaik (OPV). Zur weiteren Steigerung von Leistungsfähigkeit und Effizienz ist die genaue Modellierung elektronischer Prozesse in den Bauteilen von grundlegender Bedeutung. Für die erfolgreiche Optimierung von Bauteilen ist eine zuverlässige Charakterisierung und Validierung der elektronischen Materialeigenschaften gleichermaßen erforderlich. Außerdem eröffnet das Verständnis der Zusammenhänge zwischen Materialstruktur und -eigenschaften einen Weg für innovative Material- und Bauteilentwicklung. Im Rahmen dieser Dissertation werden zwei Methoden für die Materialcharakterisierung entwickelt, verfeinert und angewandt: eine neuartige Methode zur Messung der Ladungsträgerbeweglichkeit μ und eine Möglichkeit zur Bestimmung der Ionisierungsenergie IE oder der Elektronenaffinität EA eines organischen Halbleiters. Für die Beweglichkeitsmessungen wird eine neue Auswertungsmethode für raumladungsbegrenzte Ströme (SCLC) in unipolaren Bauteilen entwickelt. Sie basiert auf einer Schichtdickenvariation des zu charakterisierenden Materials. In einem Ansatz zur räumlichen Abbildung des elektrischen Potentials (\"potential mapping\", POEM) wird gezeigt, dass das elektrische Potential als Funktion der Schichtdicke V(d) bei einer gegebenen Stromdichte dem räumlichen Verlauf des elektrischen Potentials V(x) im dicksten Bauteil entspricht. Daraus kann die Beweglichkeit als Funktion des elektrischen Felds F und der Ladungsträgerdichte n berechnet werden. Die Auswertung ist modellfrei, d.h. ein Modell zum Angleichen der Messdaten ist für die Berechnung von μ(F, n) nicht erforderlich. Die Messung ist außerdem unabhängig von einer möglichen Injektionsbarriere oder einer Potentialstufe an nicht-idealen Kontakten. Die gemessene Funktion μ(F, n) beschreibt die effektive durchschnittliche Beweglichkeit aller freien und in Fallenzuständen gefangenen Ladungsträger. Dieser Zugang beschreibt den Ladungstransport in energetisch ungeordneten Materialien realistisch, wo eine klare Unterscheidung zwischen freien und Fallenzuständen nicht möglich oder willkürlich ist. Die Messung von IE und EA wird mithilfe temperaturabhängiger Messungen an Solarzellen durchgeführt. In geeigneten Bauteilen mit einem Mischschicht-Heteroübergang (\"bulk heterojunction\" BHJ) ist die Leerlaufspannung Voc im gesamten Messbereich oberhalb 180K eine linear fallende Funktion der Temperatur T. Es kann bestätigt werden, dass die Extrapolation zum Temperaturnullpunkt V0 = Voc(T → 0K) mit der effektiven Energielücke Egeff , d.h. der Differenz zwischen EA des Akzeptor-Materials und IE des Donator-Materials, übereinstimmt. Die systematische schrittweise Variation einzelner Bestandteile der Solarzellen und die Überprüfung des Einflusses auf V0 bestätigen die Beziehung V0 = Egeff. Damit kann die IE oder EA eines Materials bestimmt werden, indem man es in einem BHJ mit einem Material kombiniert, dessen komplementärer Wert bekannt ist. Messungen per Ultraviolett-Photoelektronenspektroskopie (UPS) und inverser Photoelektronenspektroskopie (IPES) werden damit bestätigt, präzisiert und ergänzt. Die beiden entwickelten Messmethoden werden auf organische Halbleiter aus kleinen Molekülen einschließlich Mischschichten angewandt. In Mischschichten aus Zink-Phthalocyanin (ZnPc) und C60 wird eine Löcherbeweglichkeit gemessen, die sowohl thermisch als auch feld- und ladungsträgerdichteaktiviert ist. Wenn das Mischverhältnis variiert wird, steigt die Löcherbeweglichkeit mit zunehmendem ZnPc-Anteil, während die effektive Energielücke unverändert bleibt. Verschiedene weitere Materialien und Materialmischungen werden hinsichtlich Löcher- und Elektronenbeweglichkeit sowie ihrer Energielücke charakterisiert, einschließlich bisher wenig untersuchter hochverdünnter Donator-Systeme. In allen Materialien wird eine deutliche Feldaktivierung der Beweglichkeit beobachtet. Die Ergebnisse ermöglichen eine verbesserte Beschreibung der detaillierten Funktionsweise organischer Solarzellen und unterstützen die künftige Entwicklung hocheffizienter und optimierter Bauteile

The stakeholder management framework of the 1980s and the triple bottom line framework of the 1990s strengthened corporate social responsibility but these frameworks could not bring about fundamental change in the role of businesses in society in relation to value creation. Hence, by the beginning of the present century, drawing on the ‘Sustainable Value’ and ‘Shared Value’ business models, the selected Australian banking and property organisations are striving to leverage on business strategies for generation of social and economic values. However, the Australian academic literature and industry reports demonstrate limited contributions to the sustainable and shared value literature, and hence, failing to support and deliver a comprehensive business model. To fill this conceptual and practical gap in the Australian industrial context, this study is undertaken with a view to recommend an alternative business model to integrate socioenvironmental issues and opportunities into core business strategy. Research objectives of the underlying study are to: a) explore the adoption of components of the applied sustainable value and shared value business models by Australian banking and property organisations for social and economic value creation; and b) empirically develop an alternative business model for the Australian banking and property industries based on emerging thematic components from industry-wide interview responses. Based on the interpretive paradigm, this study has adopted a qualitative multiple case study design to conduct semi-structured open-ended face-to-face interviews. The cases (n=8) in the banking and property industries have been selected through a purposive critical sampling approach. A thematic NVivo analysis was conducted based on four thematic components derived from the applied sustainable and shared value business models, namely clean technology, sustainability vision at the bottom of the pyramid, reconceiving of products/services and redefining of the value chain. This study explores how the selected Australian banking and property organisations are utilising various thematic components for social and economic value creation in addition to other components (i.e. customer/stakeholder engagement, community resilience) not otherwise categorically mentioned within both the above-mentioned models. The major findings show a number of industry-wide differences, which include a) banking organisations predominantly leverage sustainability based on product/service innovation at the bottom of the pyramid level, and b) property organisations predominantly leverage environmental sustainability based on the application of clean technology through redefining the value chain. The primary interview data findings suggest that the selected Australian sustainable and shared value organisations also emphasise the co-creation of value based on their engagement with customers, stakeholders, and communities. The secondary data findings suggest that the selected Australian property organisations have ensured a higher increase in net profit after tax and return on equity compared to the banking organisations. The secondary data further suggest that organisations (i.e. Suncorp, Charter Hall, Company X, Stockland) which used the combination of the elements of sustainable and shared value business models performed better in terms of profitability (i.e. economic value) than the organisations which only used either the sustainable value (ANZ, Lendlease) or the shared value (Bendigo, NAB) model. The only exception being Stockland, which experienced a slight decrease in the return on equity during the 2014- 18 period inspite of almost triple digit increase in net profit during the above-mentioned period. In terms of social value, the secondary data further suggest that the selected banking and property organisations have undertaken quite considerable social and community investments while leveraging on the components of various business models. The main recommendation of this study is an empirically developed alternative business model for value co-creation based on two new thematic components, which are customer/stakeholder engagement and community resilience that emerged from the industry case interviews. The significance of the study lies in the fact that all future academic researchers and practice managers should be able to implement the recommended business model for value co-creation to enhance social and economic value. One of the other major implications of the study lies in its application of a stakeholder-centric (i.e. customers, communities) value creation model by Australian banking organisations which have recently gone through the Financial Services Royal Commission investigation. The future theoretical implications of this study on value cocreation can be considered in terms of a better understanding of stakeholder theory (encompassing customers and communities) and agency theory (encompassing valueseeking organisational agents) with respect to the banking and property industry in Australian context.

碩士
國立成功大學
物理學系碩博士班
97
The dynamical behavior of carriers near the surface of a semiconductor had been an important issue in various applications of semiconductor devices. Some evanescent states may appear at the semiconductor surface. These surface states cause charge re-arrangement, and render the band-bending. In this thesis, we assumed a model of Gaussian distributive surface state within the band gap to study the band bending as functions of surface state density, distribution width, the doping concentration, and temperature. When the surface-state density is larger than , the Fermi-level on the surface is pinned at the energy of surface state. Introducing an intrinsic layer between the surface and the doped semiconductor to form the SIN structure, we can further study the effect of the intrinsic layer width to the band-bending. This preliminary study sets the scenario for future investigations on carrier dynamics under luminescence.

碩士
國立臺灣科技大學
機械工程研究所
83
The aim of this thesis is to apply an elastic-plastic incremental finite element computer code to simulate the U- bending process . The Updated Lagrangian Formulation is employed as the basis for the coding . The R_min method which determines the step increment is used to deal with elements yield conditions, nodes-tool contact conditions, maximun strains and rotation increments . The Coulomb friction''s law is used to calculate the frictions at the tool- sheet interface . The finite element method is used to obtained the complete deformation history of the U-bending process , such as deformation profile of each step , the relation of punch load and displacement , the distribution of sheet thickness and the springback profile . The experimental results obtain from U-bend tests and agree with the results of numerical analysis .

碩士
國立高雄第一科技大學
機械與自動化工程所
92
One of the major sheet-metal operations is bending operation which deformed a metal sheet into an angular shape along a straight axis with a spring-back effect. This paper investigates the factors of the spring-back effect and their optimal values to minimize the spring-back for AZ31B Magnesium-alloy sheets by finite element analysis and Taguchi’s experimental design method. The factors of the spring-back effect in this study include temperature,the radius of punch ,the radius of die corner,and die clearance with three levels respectively.

博士
國立臺灣大學
醫學工程學研究所
102
Background: Low back pain (LBP) is one of the most common reasons which bring patients to consult a health care professional, especially in a rehabilitation outpatient clinic. A comprehensive pain assessment for LBP patients is very important; researchers and clinicians need to develop a system to record the pain intensity of LBP patients quantitatively and objectively. The most common possible source of pain in LBP patients is muscular pain. For evaluation of muscles over low back, dynamic surface electromyography (SEMG) is a reliable and stable tool. The special flexion-relaxation phenomenon (FRP) in dynamic SEMG is a good indicator of LBP patients. For expression of pain, hand grasp is a common pain behavior when tolerating pain and hand grasp is easy to be analyzed quantitatively. Our research developed a system combining dynamic SEMG and grasp force measurement to analyze the pain behavior induced by bending in low back pain patients quantitatively. Methods: Our system included a wireless multi-channel biomedical signal recording device, wireless transceiver module, SEMG, dynamometer, and a personal computer (PC). 27 LBP patients (8 males and 19 females) were included in this research. We recorded the score of visual analog scale (VAS), Oswestry low back disability questionnaire (ODQ), and Beck depression inventory (BDI) before testing. In SEMG and dynamometer test, subjects grasped the dynamometer and performed a flexion-extension test maneuver. They were instructed to grasp the dynamometer tighter if stronger pain. Results: In basic data, the average age of subjects is 45.4±17.2 years old, the average score of VAS is 5.37 ± 2.05, the average score of ODQ is 30.03 ±17.93 %, and the average score of BDI is 9.3 ± 7.1. These results show that the pain intensity is moderate, the disability level is low, and there is almost no depression in our subjects. In SEMG and dynamometer test, the mean of correlation-coefficient between the grasp force area and the SEMG area is 0.93. The latency difference between gasp force and SEMG is significantly different between male and female LBP patients (p<0.05). Male patients show a slower onset of grasp force than SEMG, but female patients show an inconsistence on latency difference. Conclusions: The measurement of dynamic SEMG and grasp force can be used to analyze the pain behavior objectively and quantitatively in LBP patients. There is obvious difference of pain behavior between male and female LBP patients. Key words: pain behavior, low back pain.

碩士
國立高雄應用科技大學
模具工程系
97
ABSTRACT The development of micro manufacturing technologies plays an import role in reducing the cost and improving the quality of consumer electronics products which towards miniaturization. Micro metal forming can be used for mass production and has potential to produce micro metal components with high precision and low cost. The micro forming process involves elastic deformation and could cause spring back problems in manufacturing. These problems particularly occur in micro bending processes. Therefore, developing the techniques for predicting the spring back effects is widely interested and the results can be used to help the product design. This study uses different sheet materials, including copper alloys and stainless steels, in the micro bending processes in order to understand spring back effects and establish the guides for product design. A set of dies for micro bending process was designed and prepared for the experiments. By using the sheets with a thickness of 0.2 mm and a width of 0.8 mm, different experimental conditions including punch radius and punch offset have been considered. The measurements of the spring back angles were carefully recorded and analyzed. The results show that the spring back angle increase as the punch radius and the punch offset increase. According to the measured data, the guides for predicting the spring back angle were established and confirmed with the experiments. The guides can be useful to help the die design for manufacturing micro products in which the micro bending process is needed. Keywords: micro bending, spring back, micro metal forming, progress die design

The core-level energy shifts observed using X-ray photoelectron spectroscopy (XPS) have been used to determine the band bending at Si(111) surfaces terminated with Si-Br, Si-H, and Si-CH₃ groups, respectively. The surface termination influenced the band bending, with the Si 2p_3/2 binding energy affected more by the surface chemistry than by the dopant type. The highest binding energies were measured on Si(111)-Br (whose Fermi level was positioned near the conduction band at the surface), followed by Si(111)-H, followed by Si(111)-CH₃ (whose Fermi level was positioned near mid-gap at the surface). Si(111)-CH₃ surfaces exposed to Br₂(g) yielded the lowest binding energies, with the Fermi level positioned between mid-gap and the valence band. The Fermi level position of Br₂(g)-exposed Si(111)-CH₃ was consistent with the presence of negatively charged bromine-containing ions on such surfaces. The binding energies of all of the species detected on the surface (C, O, Br) shifted with the band bending, illustrating the importance of isolating the effects of band bending when measuring chemical shifts on semiconductor surfaces. The influence of band bending was confirmed by surface photovoltage (SPV) measurements, which showed that the core levels shifted toward their flat-band values upon illumination. Where applicable, the contribution from the X-ray source to the SPV was isolated and quantified. Work functions were measured by ultraviolet photoelectron spectroscopy (UPS), allowing for calculation of the sign and magnitude of the surface dipole in such systems. The values of the surface dipoles were in good agreement with previous measurements as well as with electronegativity considerations. The binding energies of the adventitious carbon signals were affected by band bending as well as by the surface dipole. A model of band bending in which charged surface states are located exterior to the surface dipole is consistent with the XPS and UPS behavior of the chemically functionalized Si(111) surfaces investigated herein.

碩士
國立中山大學
物理學系研究所
95
The wurtzite GaN has either Ga or N polarity. The direction of polarization, hence it’s associated polarization-induced electric fields (Fp), is determined by the polarity of the sample. In the present work, we prepared both N-face polarity and n-type doping of GaN with thicknesses are 1.1μm and 70nm. Photoreflectacne (PR) and contactless electroreflectance (CER) were used in combination to study the nature of the surface band bending which was found to be determined by the type of doping for the thick sample and by the polarity for the polarity for the thin sample. This is in agreement with a theoretical calculation by Poisson-Schrödinger solver. Hence, CER can determine the polarity of GaN film as long as the sample is thin enough of the Fp to become dominant in the surface region.

This study is concerned with correlating the macroscopic optoelectronic properties of SnO2 tin oxide, a transparent conducting oxide, with its microscopic morphology and electronic structure. To this end, a set of around 300 thin film samples was synthesized by sputter deposition and thoroughly characterised using state of the art analytical methods, first and foremost in-situ photoelectron spectroscopy. One main topic of the work is the correct determination of Fermi level position, and extraction of further meaningful physical information, from X-ray photoelectron spectroscopy (XPS) data. Comparison with charge carrier density, determined by Hall-effect measurement, indicates that the usually employed approaches are not suited to extract Fermi level positions from XPS data, due to doped SnO2 being a degenerate semiconductor. A more elaborate approach is successfully developed. SnO2 Fermi Level positions are then used to analyse the correlation of optoelectronic properties of SnO2 thin films doped with Antimony or Tantalum with their microscopic morphology. Results indicate that energetic barriers, caused by band bending at grain boundaries, are limiting factors in regard to electrical conductivity. Band bending at grain boundaries and surfaces is analysed thoroughly by using XPS and electrical measurements, developing new data analysis methods in the process. These methods are then employed to prove the validity of a novel doping concept called 'insulator modulation doping', which uses the band alignment at an Al2O3-SnO2 interface to locally force the SnO2 Fermi level above the classical doping limit, which has previously not been thought to be possible.

Organic semiconductors are a new key technology for large-area and flexible thin-film electronics. They are deposited as thin films (sub-nanometer to micrometer) on large-area substrates. The technologically most advanced applications are organic light emitting diodes (OLEDs) and organic photovoltaics (OPV). For the improvement of performance and efficiency, correct modeling of the electronic processes in the devices is essential. Reliable characterization and validation of the electronic properties of the materials is simultaneously required for the successful optimization of devices. Furthermore, understanding the relations between material structures and their key characteristics opens the path for innovative material and device design. In this thesis, two material characterization methods are developed, respectively refined and applied: a novel technique for measuring the charge carrier mobility μ and a way to determine the ionization energy IE or the electron affinity EA of an organic semiconductor. For the mobility measurements, a new evaluation approach for space-charge limited current (SCLC) measurements in single carrier devices is developed. It is based on a layer thickness variation of the material under investigation. In the \"potential mapping\" (POEM) approach, the voltage as a function of the device thickness V(d) at a given current density is shown to coincide with the spatial distribution of the electric potential V(x) in the thickest device. On this basis, the mobility is directly obtained as function of the electric field F and the charge carrier density n. The evaluation is model-free, i.e. a model for μ(F, n) to fit the measurement data is not required, and the measurement is independent of a possible injection barrier or potential drop at non-optimal contacts. The obtained μ(F, n) function describes the effective average mobility of free and trapped charge carriers. This approach realistically describes charge transport in energetically disordered materials, where a clear differentiation between trapped and free charges is impossible or arbitrary. The measurement of IE and EA is performed by characterizing solar cells at varying temperature T. In suitably designed devices based on a bulk heterojunction (BHJ), the open-circuit voltage Voc is a linear function of T with negative slope in the whole measured range down to 180K. The extrapolation to temperature zero V0 = Voc(T → 0K) is confirmed to equal the effective gap Egeff, i.e. the difference between the EA of the acceptor and the IE of the donor. The successive variation of different components of the devices and testing their influence on V0 verifies the relation V0 = Egeff. On this basis, the IE or EA of a material can be determined in a BHJ with a material where the complementary value is known. The measurement is applied to a number of material combinations, confirming, refining, and complementing previously reported values from ultraviolet photo electron spectroscopy (UPS) and inverse photo electron spectroscopy (IPES). These measurements are applied to small molecule organic semiconductors, including mixed layers. In blends of zinc-phthalocyanine (ZnPc) and C60, the hole mobility is found to be thermally and field activated, as well as increasing with charge density. Varying the mixing ratio, the hole mobility is found to increase with increasing ZnPc content, while the effective gap stays unchanged. A number of further materials and material blends are characterized with respect to hole and electron mobility and the effective gap, including highly diluted donor blends, which have been little investigated before. In all materials, a pronounced field activation of the mobility is observed. The results enable an improved detailed description of the working principle of organic solar cells and support the future design of highly efficient and optimized devices.:1. Introduction 2. Organic semiconductors and devices 2.1. Organic semiconductors 2.1.1. Conjugated π system 2.1.2. Small molecules and polymers 2.1.3. Disorder in amorphous materials 2.1.4. Polarons 2.1.5. Polaron hopping 2.1.6. Fermi-Dirac distribution and Fermi level 2.1.7. Quasi-Fermi levels 2.1.8. Trap states 2.1.9. Doping 2.1.10. Excitons 2.2. Interfaces and blend layers 2.2.1. Interface dipoles 2.2.2. Energy level bending 2.2.3. Injection from metal into semiconductor, and extraction 2.2.4. Excitons at interfaces 2.3. Charge transport and recombination in organic semiconductors 2.3.1. Drift transport 2.3.2. Charge carrier mobility 2.3.3. Thermally activated transport 2.3.4. Diffusion transport 2.3.5. Drift-diffusion transport 2.3.6. Space-charge limited current 2.3.7. Recombination 2.4. Mobility measurement 2.4.1. SCLC and TCLC 2.4.2. Time of flight 2.4.3. Organic field effect transistors 2.4.4. CELIV 2.5. Organic solar cells 2.5.1. Exciton diffusion towards the interface 2.5.2. Dissociation of CT states 2.5.3. CT recombination 2.5.4. Flat and bulk heterojunction 2.5.5. Transport layers 2.5.6. Thin film optics 2.5.7. Current-voltage characteristics and equivalent circuit 2.5.8. Solar cell efficiency 2.5.9. Limits of efficiency 2.5.10. Correct solar cell characterization 2.5.11. The \"O-Factor\" 3. Materials and experimental methods 3.1. Materials 3.2. Device fabrication and layout 3.2.1. Layer deposition 3.2.2. Encapsulation 3.2.3. Homogeneity of layer thickness on a wafer 3.2.4. Device layout 3.3. Characterization 3.3.1. Electrical characterization 3.3.2. Sample illumination 3.3.3. Temperature dependent characterization 3.3.4. UPS 4. Simulations 5.1. Design of single carrier devices 5.1.1. General design requirements 5.1.2. Single carrier devices for space-charge limited current 5.1.3. Ohmic regime 5.1.4. Design of injection and extraction layers 5.2. Advanced evaluation of SCLC – potential mapping 5.2.1. Potential mapping by thickness variation 5.2.2. Further evaluation of the transport profile 5.2.3. Injection into and extraction from single carrier devices 5.2.4. Majority carrier approximation 5.3. Proof of principle: POEM on simulated data 5.3.1. Constant mobility 5.3.2. Field dependent mobility 5.3.3. Field and charge density activated mobility 5.3.4. Conclusion 5.4. Application: Transport characterization in organic semiconductors 5.4.1. Hole transport in ZnPc:C60 5.4.2. Hole transport in ZnPc:C60 – temperature variation 5.4.3. Hole transport in ZnPc:C60 – blend ratio variation 5.4.4. Hole transport in ZnPc:C70 5.4.5. Hole transport in neat ZnPc 5.4.6. Hole transport in F4-ZnPc:C60 5.4.7. Hole transport in DCV-5T-Me33:C60 5.4.8. Electron transport in ZnPc:C60 5.4.9. Electron transport in neat Bis-HFl-NTCDI 5.5. Summary and discussion of the results 5.5.1. Phthalocyanine:C60 blends 5.5.2. DCV-5T-Me33:C60 5.5.3. Conclusion 6. Organic solar cell characteristics: the influence of temperature 6.1. ZnPc:C60 solar cells 6.1.1. Temperature variation 6.1.2. Illumination intensity variation 6.2. Voc in flat and bulk heterojunction organic solar cells 6.2.1. Qualitative difference in Voc(I, T) 6.2.2. Interpretation of Voc(I, T) 6.3. BHJ stoichiometry variation 6.3.1. Voc upon variation of stoichiometry and contact layer 6.3.2. V0 upon stoichiometry variation 6.3.3. Low donor content stoichiometry 6.3.4. Conclusion from stoichiometry variation 6.4. Transport material variation 6.4.1. HTM variation 6.4.2. ETM variation 6.5. Donor:acceptor material variation 6.5.1. Donor variation 6.5.2. Acceptor variation 6.6. Conclusion 7. Summary and outlook 7.1. Summary 7.2. Outlook A. Appendix A.1. Energy pay-back of this thesis A.2. Tables and registers
Organische Halbleiter sind eine neue Schlüsseltechnologie für großflächige und flexible Dünnschichtelektronik. Sie werden als dünne Materialschichten (Sub-Nanometer bis Mikrometer) auf großflächige Substrate aufgebracht. Die technologisch am weitesten fortgeschrittenen Anwendungen sind organische Leuchtdioden (OLEDs) und organische Photovoltaik (OPV). Zur weiteren Steigerung von Leistungsfähigkeit und Effizienz ist die genaue Modellierung elektronischer Prozesse in den Bauteilen von grundlegender Bedeutung. Für die erfolgreiche Optimierung von Bauteilen ist eine zuverlässige Charakterisierung und Validierung der elektronischen Materialeigenschaften gleichermaßen erforderlich. Außerdem eröffnet das Verständnis der Zusammenhänge zwischen Materialstruktur und -eigenschaften einen Weg für innovative Material- und Bauteilentwicklung. Im Rahmen dieser Dissertation werden zwei Methoden für die Materialcharakterisierung entwickelt, verfeinert und angewandt: eine neuartige Methode zur Messung der Ladungsträgerbeweglichkeit μ und eine Möglichkeit zur Bestimmung der Ionisierungsenergie IE oder der Elektronenaffinität EA eines organischen Halbleiters. Für die Beweglichkeitsmessungen wird eine neue Auswertungsmethode für raumladungsbegrenzte Ströme (SCLC) in unipolaren Bauteilen entwickelt. Sie basiert auf einer Schichtdickenvariation des zu charakterisierenden Materials. In einem Ansatz zur räumlichen Abbildung des elektrischen Potentials (\"potential mapping\", POEM) wird gezeigt, dass das elektrische Potential als Funktion der Schichtdicke V(d) bei einer gegebenen Stromdichte dem räumlichen Verlauf des elektrischen Potentials V(x) im dicksten Bauteil entspricht. Daraus kann die Beweglichkeit als Funktion des elektrischen Felds F und der Ladungsträgerdichte n berechnet werden. Die Auswertung ist modellfrei, d.h. ein Modell zum Angleichen der Messdaten ist für die Berechnung von μ(F, n) nicht erforderlich. Die Messung ist außerdem unabhängig von einer möglichen Injektionsbarriere oder einer Potentialstufe an nicht-idealen Kontakten. Die gemessene Funktion μ(F, n) beschreibt die effektive durchschnittliche Beweglichkeit aller freien und in Fallenzuständen gefangenen Ladungsträger. Dieser Zugang beschreibt den Ladungstransport in energetisch ungeordneten Materialien realistisch, wo eine klare Unterscheidung zwischen freien und Fallenzuständen nicht möglich oder willkürlich ist. Die Messung von IE und EA wird mithilfe temperaturabhängiger Messungen an Solarzellen durchgeführt. In geeigneten Bauteilen mit einem Mischschicht-Heteroübergang (\"bulk heterojunction\" BHJ) ist die Leerlaufspannung Voc im gesamten Messbereich oberhalb 180K eine linear fallende Funktion der Temperatur T. Es kann bestätigt werden, dass die Extrapolation zum Temperaturnullpunkt V0 = Voc(T → 0K) mit der effektiven Energielücke Egeff , d.h. der Differenz zwischen EA des Akzeptor-Materials und IE des Donator-Materials, übereinstimmt. Die systematische schrittweise Variation einzelner Bestandteile der Solarzellen und die Überprüfung des Einflusses auf V0 bestätigen die Beziehung V0 = Egeff. Damit kann die IE oder EA eines Materials bestimmt werden, indem man es in einem BHJ mit einem Material kombiniert, dessen komplementärer Wert bekannt ist. Messungen per Ultraviolett-Photoelektronenspektroskopie (UPS) und inverser Photoelektronenspektroskopie (IPES) werden damit bestätigt, präzisiert und ergänzt. Die beiden entwickelten Messmethoden werden auf organische Halbleiter aus kleinen Molekülen einschließlich Mischschichten angewandt. In Mischschichten aus Zink-Phthalocyanin (ZnPc) und C60 wird eine Löcherbeweglichkeit gemessen, die sowohl thermisch als auch feld- und ladungsträgerdichteaktiviert ist. Wenn das Mischverhältnis variiert wird, steigt die Löcherbeweglichkeit mit zunehmendem ZnPc-Anteil, während die effektive Energielücke unverändert bleibt. Verschiedene weitere Materialien und Materialmischungen werden hinsichtlich Löcher- und Elektronenbeweglichkeit sowie ihrer Energielücke charakterisiert, einschließlich bisher wenig untersuchter hochverdünnter Donator-Systeme. In allen Materialien wird eine deutliche Feldaktivierung der Beweglichkeit beobachtet. Die Ergebnisse ermöglichen eine verbesserte Beschreibung der detaillierten Funktionsweise organischer Solarzellen und unterstützen die künftige Entwicklung hocheffizienter und optimierter Bauteile.:1. Introduction 2. Organic semiconductors and devices 2.1. Organic semiconductors 2.1.1. Conjugated π system 2.1.2. Small molecules and polymers 2.1.3. Disorder in amorphous materials 2.1.4. Polarons 2.1.5. Polaron hopping 2.1.6. Fermi-Dirac distribution and Fermi level 2.1.7. Quasi-Fermi levels 2.1.8. Trap states 2.1.9. Doping 2.1.10. Excitons 2.2. Interfaces and blend layers 2.2.1. Interface dipoles 2.2.2. Energy level bending 2.2.3. Injection from metal into semiconductor, and extraction 2.2.4. Excitons at interfaces 2.3. Charge transport and recombination in organic semiconductors 2.3.1. Drift transport 2.3.2. Charge carrier mobility 2.3.3. Thermally activated transport 2.3.4. Diffusion transport 2.3.5. Drift-diffusion transport 2.3.6. Space-charge limited current 2.3.7. Recombination 2.4. Mobility measurement 2.4.1. SCLC and TCLC 2.4.2. Time of flight 2.4.3. Organic field effect transistors 2.4.4. CELIV 2.5. Organic solar cells 2.5.1. Exciton diffusion towards the interface 2.5.2. Dissociation of CT states 2.5.3. CT recombination 2.5.4. Flat and bulk heterojunction 2.5.5. Transport layers 2.5.6. Thin film optics 2.5.7. Current-voltage characteristics and equivalent circuit 2.5.8. Solar cell efficiency 2.5.9. Limits of efficiency 2.5.10. Correct solar cell characterization 2.5.11. The \"O-Factor\" 3. Materials and experimental methods 3.1. Materials 3.2. Device fabrication and layout 3.2.1. Layer deposition 3.2.2. Encapsulation 3.2.3. Homogeneity of layer thickness on a wafer 3.2.4. Device layout 3.3. Characterization 3.3.1. Electrical characterization 3.3.2. Sample illumination 3.3.3. Temperature dependent characterization 3.3.4. UPS 4. Simulations 5.1. Design of single carrier devices 5.1.1. General design requirements 5.1.2. Single carrier devices for space-charge limited current 5.1.3. Ohmic regime 5.1.4. Design of injection and extraction layers 5.2. Advanced evaluation of SCLC – potential mapping 5.2.1. Potential mapping by thickness variation 5.2.2. Further evaluation of the transport profile 5.2.3. Injection into and extraction from single carrier devices 5.2.4. Majority carrier approximation 5.3. Proof of principle: POEM on simulated data 5.3.1. Constant mobility 5.3.2. Field dependent mobility 5.3.3. Field and charge density activated mobility 5.3.4. Conclusion 5.4. Application: Transport characterization in organic semiconductors 5.4.1. Hole transport in ZnPc:C60 5.4.2. Hole transport in ZnPc:C60 – temperature variation 5.4.3. Hole transport in ZnPc:C60 – blend ratio variation 5.4.4. Hole transport in ZnPc:C70 5.4.5. Hole transport in neat ZnPc 5.4.6. Hole transport in F4-ZnPc:C60 5.4.7. Hole transport in DCV-5T-Me33:C60 5.4.8. Electron transport in ZnPc:C60 5.4.9. Electron transport in neat Bis-HFl-NTCDI 5.5. Summary and discussion of the results 5.5.1. Phthalocyanine:C60 blends 5.5.2. DCV-5T-Me33:C60 5.5.3. Conclusion 6. Organic solar cell characteristics: the influence of temperature 6.1. ZnPc:C60 solar cells 6.1.1. Temperature variation 6.1.2. Illumination intensity variation 6.2. Voc in flat and bulk heterojunction organic solar cells 6.2.1. Qualitative difference in Voc(I, T) 6.2.2. Interpretation of Voc(I, T) 6.3. BHJ stoichiometry variation 6.3.1. Voc upon variation of stoichiometry and contact layer 6.3.2. V0 upon stoichiometry variation 6.3.3. Low donor content stoichiometry 6.3.4. Conclusion from stoichiometry variation 6.4. Transport material variation 6.4.1. HTM variation 6.4.2. ETM variation 6.5. Donor:acceptor material variation 6.5.1. Donor variation 6.5.2. Acceptor variation 6.6. Conclusion 7. Summary and outlook 7.1. Summary 7.2. Outlook A. Appendix A.1. Energy pay-back of this thesis A.2. Tables and registers