The newfound capability of creating moisture sensitive interference multilayered thin films (MLTFs) comprising microfibrillated cellulose and polymers has not previously been possible to implement on surfaces other than silicon wafer strips. Being able to incorporate interference MLTFs on fibre-based materials would introduce the possibility for new applications within authentication, sensing and customer attraction for the paper and packaging industry. By using trichloro (1H, 1H, 2H, 2H-perfluorooctyl) silane we were able to hydrophobically modify silicon substrates, enabling interference MLTF lift-off and thus the creation of free-standing MLTFs of approximately 400 nm thickness. Contact dried MLTFs approximately 250 nm thick, were successfully transferred to copy- and filter paper as well as to cellulose-based dialysis membranes. We can also report on the successful synthesis of interference MLTFs directly on a fibre composite material and on aluminium. Initial tests of a method to quantify the pull-off conditions of the MLTFs from the fluorinated surfaces using the Micro Adhesion Measurement Apparatus showed promising results.

The aim of this thesis is to investigate how material surfaces are affected by various surface treatments and how this relates to the adhesion of the coating. The materials that were studied were WC-Co and Cermets and the surface treatments used were polishing, grinding with coarser and finer abrasive grains, and finally wet blasting and dry blasting. Focus was on deformations and residual stresses in the surface, surface roughness and cracks. The test methods used for examining the samples included surface roughness measurements, residual stress measurements, adhesion tests using Rockwell indentation and SEM images of the surface and the cross section.<br /><br />The results concluded that polishing gives very good adhesion. Additionally, the adhesion for ground surfaces was good for WC-Co but very poor for Cermets. Furthermore, it was observed that finer abrasive grains did not result in better adhesion. In fact, the coarser grains gave slightly better results. Finally, it was concluded that wet blasting has a clear advantage over dry blasting and results in much better adhesion, especially for the Cermets. The results for the WC-Co were a bit inconsistent and so further research is required.

<p>Oligo(phenyleneethynylene) (OPE) molecules are a class of fully conjugated aromatic molecules, that attract attention for their application as “molecular wires” in molecular electronic devices. In this thesis work, self-assembled monolayers (SAMs) formed from a variety of OPE derivatives have been studied. The chemical properties, structure, and packing density of the SAMs have been characterized utilizing techniques such as high-resolution X-ray photoemission spectroscopy (HRXPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), Infrared reflection absorption spectroscopy (IRRAS), contact angle measurements, and atomic force microscopy (AFM).</p><p>In a first study, three OPE-derivatives, with benzene, naphthalene and anthracene, respectively, inserted into the backbone, and an acetyl-protected thiophenol binding group were found to form SAMs on Au(111) substrates with lower molecular surface densities and larger molecular inclination as the lateral π-system increases.</p><p>In a second study, porphyrin was introduced as the end group to a wire-like molecule such as OPE. The purpose was to obtain well-organized and functionalized surfaces with optical and redox properties. Three porphyrin-functionalized OPEs had different binding groups, an acetyl-protected thiophenol, a benzylic thiol, and a trimethylsilylethynylene group, and were found to form SAMs on gold surfaces with difference in structure and degree of order. The molecules with the acetyl-protected thiophenol binding group were found to form a high quality SAM compared to the other two. This SAM exhibits a well-ordered and densely packed layer.</p><p>This study gives rise to a better understanding of SAM formation of OPE derivatives, and will form a base for further investigations of charge transport properties of these molecular films, which is of interest for applications in molecular electronic devices.</p>

The work presented in this thesis deals with experimental and theoretical studies related to alumina thin films. Alumina, Al2O3, is a polymorphic material utilized in a variety of applications, e.g., in the form of thin films. However, controlling thin film growth of this material, in particular at low substrate temperatures, is not straightforward. The aim of this work is to increase the understanding of the basic mechanisms governing alumina growth and to investigate novel ways of synthesizing alumina coatings. The thesis can be divided into two main parts, where the first part deals with fundamental studies of mechanisms affecting alumina growth and the second part with more application-oriented studies of high power impulse magnetron sputter (HiPIMS) deposition of the material. In the first part, it was shown that the thermodynamically stable α phase, which normally is synthesized at substrate temperatures of around 1000 °C, can be grown using reactive sputtering at a substrate temperature of merely 500 °C by controlling the nucleation surface. This was done by predepositing a Cr2O3 nucleation layer. Moreover, it was found that an additional requirement for the formation of the α phase is that the depositions are carried out at low enough total pressure and high enough oxygen partial pressure. Based on these observations, it was concluded that energetic bombardment, plausibly originating from energetic oxygen, is necessary for the formation of α-alumina (in addition to the effect of the chromia nucleation layer). Moreover, the effects of residual water on the growth of crystalline films were investigated by varying the partial pressure of water in the ultra high vacuum (UHV) chamber. Films deposited onto chromia nucleation layers exhibited a columnar structure and consisted of crystalline α-alumina if deposited under UHV conditions. However, as water to a partial pressure of 1*10-5 Torr was introduced, the columnar α-alumina growth was disrupted. Instead, a microstructure consisting of small, equiaxed grains was formed, and the γ-alumina content was found to increase with increasing film thickness. To gain a better understanding of the atomistic processes occurring on the surface, density functional theory based computational studies of adsorption and diffusion of Al, O, AlO, and O2 on different α-alumina (0001) surfaces were also performed. The results give possible reasons for the difficulties in growing the α phase at low temperatures through the identification of several metastable adsorption sites and also show how adsorbed hydrogen might inhibit further growth of α-alumina crystallites. In addition, it was shown that the Al surface diffusion activation energies are unexpectedly low, suggesting that limited surface diffusivity is not the main obstacle for low-temperature α-alumina growth. Instead, it is suggested to be more important to find ways of reducing the amount of impurities, especially hydrogen, in the process and to facilitate α-alumina nucleation when designing new processes for low-temperature deposition of α-alumina. In the second part of the thesis, reactive HiPIMS deposition of alumina was studied. In HiPIMS, a high-density plasma is created by applying very high power to the sputtering magnetron at a low duty cycle. It was found, both from experiments and modeling, that the use of HiPIMS drastically influences the characteristics of the reactive sputtering process, causing reduced target poisoning and thereby reduced or eliminated hysteresis effects and relatively high deposition rates of stoichiometric alumina films. This is not only of importance for alumina growth, but for reactive sputter deposition in general, where hysteresis effects and loss of deposition rate pose a substantial problem. Moreover, it was found that the energetic and ionized deposition flux in the HiPIMS discharge can be used to lower the deposition temperature of α-alumina. Coatings predominantly consisting of the α phase were grown at temperatures as low as 650 °C directly onto cemented carbide substrates without the use of nucleation layers. Such coatings were also deposited onto cutting inserts and were tested in a steel turning application. The coatings were found to increase the crater wear resistance compared to a benchmark TiAlN coating, and the process consequently shows great potential for further development towards industrial applications.

Utvecklingen inom materialforskningen går mot att framställa avancerade material vilka är skräddarsydda för olika tillämpningar. Detta har medfört att det blir allt mer populärt att belägga ytor med ett eller flera tunna lager med syfte att förbättra materialegenskaperna. Användningsområden för ytbeläggningar går att hitta inom allt från vardagliga produkter såsom teflonbeläggningar av stekpannor, förgyllning av smycken till avancerad halvledarteknik för att åstadkomma energieffektiva lysdioder. Det enskilt största tillämpningsområdet för tunna filmer är dock som skyddande skikt för verktyg inom skärande bearbetning. Utvecklingen går stadigt mot högre skärhastigheter och därmed ökade temperaturer, idagsläget kan området där verktyget och arbetsmaterialet är i kontakt nå temperaturer på mellan 800-1000 °C utan att förlora nämnvärt i styrka. Detta har gjorts möjligt genom att belägga skären med någon eller några μm (tusendels mm) av lämpligt keramiskt material i avseende att öka motståndskraften för nötning vid bearbetning vid höga temperaturer. I den här avhandlingen har tunna filmer studerats med det övergripande målet att förbättra egenskaper hos verktyg för skärande metallbearbetning genom att öka motståndskraften hos materialen mot mekanisk och kemisk nötning vid höga temperaturer. Materialsystemet som undersökts är Ti-Si-N, där tunna filmer av både legeringar och tvåfassystem har syntetiserats och egenskapskarakteriserats. Legeringarna är belagda med varierande Si-halt från 0 till 10 atomprocent och avsedda för att studera strukturella, termiska och mekaniska egenskaper. De framställdes med en teknik som kallas arcförångning, där man i ett vakuumsystem frigör högenergetiskt material i det här fallet av Ti och Si som förångas från en solid yta kallad target. Atomerna joniseras genom kollisioner med elektroner och reagerar på sin väg mot substratet med kvävgas. Väl framme vid substratet, kondenserar jonerna och bilder den tunna filmen. Filmerna består av två strukturtyper, den första är en fast lösning där Si atomer upp till 5 at.% ersätter Ti atomer i TiN. I det andra fallet så segregerar Si till korngränserna. Värmebehandlingsexperiment visar att Si bildar SiNx som kapslar in TiN-korn vid temperaturer upp till 1000 °C. Hårdhetstester visar att filmerna bibehåller sin hårdhet upp till 1000 °C tack vare fasomvandlingen. Även vid 1100 °C är hårdheten hög. Dessa skikt besitter alltså egenskaper som gör dem väldigt användbara inom tillämpningar för skärande bearbetning. Nanostrukturerade materials egenskaper beror på dess mikrostruktur snarare än på de grundämnen som ingår, detta exemplifieras av TiN-SiNx-nanokompositer bestående av nanokristallina TiN-korn inbäddade i några få atomlager SiNx, där materialegenskaperna helt och hållet beror på kornstorleken på TiN-kornen och tjockleken på SiNx-lagren. Ökas tjockleken på SiNx minskar hårdheten. Dessa filmer har mycket goda mekaniska egenskaper och är ett av de hårdaste materialen som finns. Nyckeln till den höga hårdheten hos skikten ligger i att bilda starka bindningar mellan TiN och SiNx. Hur dessa ser ut vet man dock inte eftersom strukturen på SiNx gränsytan inte är känd. Anledningen är att den är svår att avbilda på grund av dess krökta form och begränsade volym. I denna avhandling har TiN/SiNx multilager belagts, dvs. en lagrad struktur TiN alternerad med SiNx. Dessa filmer framställdes med sputtring, en teknik som liknar arcförångning men där man istället accelerera positivt laddade joner mot Ti och Si targets med en hög negativ potential som frigör Ti och Si. I multilagren varierades SiNx-lagrets tjocklek mellan endast några få atomlager för att göra en förenklad modell av gränsytan hos nanokompositen och med atomupplöst transmissionselektronmikroskopi samt hårdhetsmätningar konstateras sedan att de hårdaste filmerna var de där kristallin SiNx stabiliseras mellan TiNkorn. Vidare studerar jag SiNx/TiN ytor med sveptunnelmikroskopi och täthetsfunktionalteori (en kvantmekanisk simuleringsmetod). Mina resultat visar SiNx och bindningarna till TiN är mycket mer komplicerade än vad man tidigare trott, då de kan vara kristallina och anta komplexa rekonstruktioner. Detta bidrar till den starka bindningen mellan TiN och SiNx vilket i sin tur förklarar varför materialen blir så hårda. / Ti-Si-N and Ti-Al-Si-N thin solid films have been studied by analytical electron microscopy, X-ray diffraction, scanning tunneling microscopy, X-ray photoelectron spectroscopy, elastic recoil detection analysis, nanoindentation, and ab initio calculations. I find that arc evaporated (Ti1-xSix)Ny films can be grown as cubic solid solutions up to x = 0.09 with a dense columnar microstructure. Films with higher Si content up to x = 0.20 assumes an extremely defect-rich, feather-like structure consisting of cubic TiN:Si nanocrystallite bundles with low-angle grain boundaries caused by thermodynamically driven Si segregation. Correspondingly, the N content in the films increases close to linear with the Si content from y = 1.00 (x = 0) to y = 1.13 (x = 0.20). Annealing of the films at 1000 °C yields a metastable crystalline SiNz (1.0 ≤ z ≤ 1.33) tissue phase in 0.04 ≤ x ≤ 0.20 films which is (semi)-coherent to TiN. These films are compositionally stable and exhibit retained hardness between 31-42 GPa up to 1000 °C. At 1100-1200 °C, the tissue phase amorphizes and all SiNz diffuse out of the films, followed by recrystallization of the cubic phase. Hard turning testing was performed on (Ti0.83Si0.17)N1.09. Analysis of the tool-chip interface prepared by focused ion beam revealed shear deformation in the film and an adhering layer consisting of the work-piece material and Si and N from the film. For (Ti0.33Al0.67)1-xSix)N (0 ≤ x ≤ 0.29) films the NaCl structure cubic (Ti,Al)N solid solution phase is predominant at low Si contents, which gradually changes to a dominating hexagonal wurtzite (Al,Ti,Si)N solid solution for 0.04 ≤ x ≤ 0.17. Additional Si results in amorphization. Annealing experiments at 600-1000 °C yields spinodal decomposition of c-(Al,Ti)N into c-AlN and c-TiN, with corresponding age hardening. The h-(Al,Ti,Si)N films exhibit precipitation of c- TiN with smaller volume than the host lattice, which results in tensile cracks formations and age hardening. Films with c-(Ti,Al)N perform best in turning applications, while films with h- (Al,Ti,Si)N form cracks and fail. Finally, I have characterized the nature of metastable crystalline SiNz phases and the interface between TiN(001) and SiNz. Magnetron sputtering was used to deposit TiN/SiNz(001) nanolaminate films with varying SiNz and TiN layer thicknesses. Maximum hardness is obtained when SiNz forms coherent interfaces with TiN. In addition, in situ surface analyses in combination with ab-initio calculations reveal that SiNz sub-monolayers grow epitaxially and form crystalline reconstructions on TiN(001) and TiN(111) surfaces. Phonon calculations predict that stoichiometric c-SiN is dynamically instable when the atoms are arranged in the NaCl and ZnS forms. However, c-Si3N4 can be stabilized with D022 or L12 ordered ZnS-like structures. These results have impact for the design of superhard nanocomposites and multilayer thin films.

Oligo(phenyleneethynylene) (OPE) molecules are a class of fully conjugated aromatic molecules, that attract attention for their application as “molecular wires” in molecular electronic devices. In this thesis work, self-assembled monolayers (SAMs) formed from a variety of OPE derivatives have been studied. The chemical properties, structure, and packing density of the SAMs have been characterized utilizing techniques such as high-resolution X-ray photoemission spectroscopy (HRXPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), Infrared reflection absorption spectroscopy (IRRAS), contact angle measurements, and atomic force microscopy (AFM). In a first study, three OPE-derivatives, with benzene, naphthalene and anthracene, respectively, inserted into the backbone, and an acetyl-protected thiophenol binding group were found to form SAMs on Au(111) substrates with lower molecular surface densities and larger molecular inclination as the lateral π-system increases. In a second study, porphyrin was introduced as the end group to a wire-like molecule such as OPE. The purpose was to obtain well-organized and functionalized surfaces with optical and redox properties. Three porphyrin-functionalized OPEs had different binding groups, an acetyl-protected thiophenol, a benzylic thiol, and a trimethylsilylethynylene group, and were found to form SAMs on gold surfaces with difference in structure and degree of order. The molecules with the acetyl-protected thiophenol binding group were found to form a high quality SAM compared to the other two. This SAM exhibits a well-ordered and densely packed layer. This study gives rise to a better understanding of SAM formation of OPE derivatives, and will form a base for further investigations of charge transport properties of these molecular films, which is of interest for applications in molecular electronic devices.

At present, focus of the SiC crystal growth development is on improving the crystalline quality without polytype inclusions, micropipes and the occurrence of extended defects. The purity of the grown material, as well as intentional doping must be well controlled and the processes understood. High-quality substrates will significantly improve device performance and yield. One of the aims of the thesis is further understanding of polytype inclusion formation as well as impurity control in SiC bulk crystals grown using PVT method also termed seeded sublimation method. Carbonization of the source was identified as a major reason behind the polytype inclusion occurrence during the growth. The aim of this work was further understanding of sublimation growth process of 4H-SiC bulk crystals in vacuum, in absence of an inert gas. For comparison growth in argon atmosphere (at 5 mbar) was performed. The effect of the ambient on the impurity incorporation was studied for different growth temperatures. For better control of the process in vacuum, tantalum as a carbon getter was utilized. The focus of the SiC part of the thesis was put on further understanding of the PVT epitaxy with an emphasis on the high growth rate and purity of grown layers. High resistivity 4H-SiC samples grown by sublimation with high growth rate were studied. The measurements show resistivity values up to high 104 cm. By correlation between the growth conditions and SIMS results, a model was applied in which it is proposed that an isolated carbon vacancy donor-like level is a possible candidate responsible for compensation of the shallow acceptors in p-type 4H-SiC. A relation between cathodoluminescence (CL) and DLTS data is taken into account to support the model. To meet the requirements for high voltage blocking devices such as high voltage Schottky diodes and MOSFETs, 4H-SiC epitaxial layers have to exhibit low doping concentration in order to block reverse voltages up to few keV and at the same time have a low on-state resistance (Ron). High Ron leads to enhanced power consumption in the operation mode of the devices. In growth of thick layers for high voltage blocking devices, the conditions to achieve good on-state characteristics become more challenging due to the low doping and pronounced thicknesses needed, preferably in short growth periods. In case of high-speed epitaxy such as the sublimation, the need to apply higher growth temperature to yield the high growth rate, results in an increased concentration of background impurities in the layers as well as an influence on the intrinsic defects. On-state resistance Ron estimated from current density-voltage characteristics of Schottky diodes on thick sublimation layers exhibits variations from tens of mΩ.cm2 to tens of Ω.cm2 for different doping levels. In order to understand the occurrence of high on-state resistance, Schottky barrier heights were first estimated for both forward and reverse bias with the application of thermionic emission theory and were in agreement with literature reported values. Decrease in mobility with increasing temperature was observed and its dependencies of T–1.3 and T–2.0 for moderately doped and low doped samples, respectively, were estimated. From deep level measurements by Minority Carrier Transient Spectroscopy (MCTS), an influence of shallow boron related levels and D-center on the on-state resistance was observed, being more pronounced in low doped samples. Similar tendency was observed in depth profiling of Ron. This suggests a major role of boron in a compensation mechanism. In the second part of the thesis growth and characterization of GaN is presented. Excellent electron transport properties with high electron saturate drift velocity make GaN an excellent candidate for electronic devices. Especially, AlGaN/GaN based high electron mobility transistors (HEMT) have received an increased attention in last years due to their attractive properties. The presence of strong spontaneous and piezoelectric polarization due to the lattice mismatch between AlGaN and GaN is responsible for high free electrons concentrations present in the vicinity of the interface. Due to the spatial separation of electrons and ionized donors or surface states, 2DEG electron gas formed near the interface of the heterostructure exhibits high sheet carrier density and high mobility of electrons. Al0.23Ga0.77N/GaN based HEMT structures with an AlN exclusion layer on 100 mm semiinsulating 4H-SiC substrates have been grown by hot-wall MOCVD. The electrical properties of the two-dimensional electron gas (2DEG) such as electron mobility, sheet carrier density and sheet resistance were obtained from Hall measurements, capacitance-voltage and contact-less eddy-current techniques. The effect of different scattering mechanisms on the mobility have been taken into account and compared to the experimental data. Hall measurements were performed in the range of 80 to 600 K. Hall electron mobility is equal to 17140 cm2(Vs)-1 at 80 K, 2310 cm2(Vs)-1 at room temperature, and as high as 800 cm2(Vs)-1 at 450 K, while the sheet carrier density is 1.04x1013 cm-2 at room temperature and does not vary very much with temperature. Estimation of different electron scattering mechanisms reveals that at temperatures higher than room temperature, experimental mobility data is mainly limited by optical phonon scattering. At relevant high power device temperature (450 K) there is still an increase of mobility due to the AlN exclusion layer. We have studied the behaviour of Ga-face GaN epilayers after in-situ thermal treatment in different gas mixtures in a hot-wall MOCVD reactor. Influence of N2, N2+NH3 and N2+NH3+H2 ambient on the morphology was investigated in this work. The most stable thermal treatment conditions were obtained in the case of N2+NH3 gas ambients. We have also studied the effect of the increased molar ratio of hydrogen in order to establish proper etching conditions for hot-wall MOCVD growth.

Ceramics are distinguished from metals and polymers by their inorganic nature and lack of metallic properties. They can be highly crystalline to amorphous, and their physical and chemical properties can vary widely. Ceramics can, for instance, be made to resemble the mineral phase in bone and are therefore an excellent substitute for damaged hard tissue. They can also be made porous, surface active, chemically inert, mechanically strong, optically transparent or biologically resorbable, and all these properties are of interest in the development of new materials intended for a wide variety of applications. In this thesis, the focus was on the development of different ceramics for use in the controlled release of drugs and ions. These concepts were developed to obtain improved therapeutic effects from orally administered opioid drugs, and to reduce the number of implant-related infections as well as to improve the stabilization of prosthetic implants in bone. Geopolymers were used to produce mechanically strong and chemically inert formulations intended for oral administration of opioids. The carriers were developed to allow controlled release of the drugs over several hours, in order to improve the therapeutic effect of the substances in patients with severe chronic pain. The requirement for a stable carrier is a key feature for these drugs, as the rapid release of the entire dose, due to mechanical or chemical damage to the carrier, could have lethal effects on the patient because of the narrow therapeutic window of opioids. It was found that it was possible to profoundly retard drug release and to achieve almost linear release profiles from mesoporous geopolymers when the aluminum/silicon ratio of the precursor particles and the curing temperature were tuned. Ceramic implant coatings were produced via a biomimetic mineralization process and used as carriers for various drugs or as an ion reservoir for local release at the site of the implant. The formation and characteristics of these coatings were examined before they were evaluated as potential drug carriers. It was demonstrated that these coatings were able to carry antibiotics, bisphosphonates and bone morphogenetic proteins to obtain a sustained local effect, as they were slowly released from the coatings. / <p>Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 710</p>

The aim of this Master’s Degree thesis project is to design and develop point diffraction interferometer plates. In this project the PDI plates are re-designed, changing the design which was used in previous projects in Halmstad University. The transparency of PDI plates can be controlled by coating them with NiCr film. Firstly, four plates with coating of different thickness of NiCr were developed. The relationship between transmittance and the thickness of NiCr was established by testing these plates for transmittance and reflectance with the help of a laser and an optical power meter. The absorption coefficient of clear substrates and reflection of light is also taken into account to achieve the correct results. The parameters like the diameter of semi-transparent area around the pinholes and the size of pinholes is chosen after fully understanding its application. The lay-out and description of design is also included in the report.