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In this project, thin films are being manufactured by different methods in a thin film deposition set-up and subsequently characterized. This is done in order to determine if the set-up is capable of producing films of sufficient quality to be used for research purposes in the ion physics group of the division of applied nuclear physics at Uppsala University. Both copper and silver films are manufactured by magnetron sputtering deposition. Copper films are also manufactured by evaporation deposition. Deposition is made on Si(001) substrates. The films are analyzed with Rutherford Backscattering Spectrometry (RBS) and Time of Flight- Elastic Recoil Detection Analysis (ToF-ERDA). Results show that the deposition rate of the set-up is much faster compared to the one provided by the manufacturer of the set-up. The purity of the films i.e. the concentrations of the contaminants are found to be in an acceptable range for research applications with an average oxygen contamination of <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?1.53%20%5Cpm%200.05%20%25" /> and carbon contamination of <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?0.53%20%5Cpm%200.02%20%25" /> for sputtered copper films. Sputtered silver films were found to have an oxygen contamination of <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?0.28%20%5Cpm%200.012%20%25" /> and a carbon contamination of <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?0.41%20%5Cpm%200.023%20%25" />. Evaporated copper films were found to have an oxygen contamination of <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?0.45%20%5Cpm%200.018%20%25" /> and carbon contamination of <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?0.31%20%5Cpm%200.013%20%25" />. Traces of gold (<img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Cprec%200.5%20%25" />) were found exclusively in the sputtered films. Trace amounts of hydrogen could also be detected in both sputtered and evaporated films. The evaporated films are found to show lower contamination by oxygen than the sputtered films, but the manufacturing process employed in this study of evaporated films is not suitable to use for producing thin films of specific thicknesses as there is insufficient data to find a deposition speed. Overall, the set-up is capable of producing thin films with a sufficient quality for it to be used by the department when producing thin films for research. / I det här projektet produceras tunnfilmer med olika metoder i en uppställning för tunnfilmsdeposition och karaktäriseras sedan för att bedöma om maskinen är kapabel att producera filmer av tillräckligt bra kvalitet för att kunna användas i forskningssyften inom jonfysikgruppen på avdelningen för tillämpad kärnfysik på Uppsala Universitet. Både koppar och silverfilmer produceras med magnetronsputtring. Kopparfilmer produceras också med resistiv förångning. Deposition sker på Si(001)-substrat. Filmerna analyseras med Rutherford Backscattering Spectrometry (RBS) och Time of Flight- Elastic Recoil Detection Analysis (ToF-ERDA). Resultaten visar att depositionshastigheten för maskinen är snabbare än det som angetts av företaget som producerar maskinen. Renheten hos filmerna, dvs. koncentrationen av föroreningar, finnes vara inom en acceptabel nivå för forskningstillämpningar med en genomsnittlig syrekontamination på <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?1.53%20%5Cpm%200.05%20%25" /> och kolkontamination på <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?0.53%20%5Cpm%200.02%20%25" /> för sputtrade kopparfilmer. Sputtrade silverfilmer finnes ha en syrekontamination på <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?0.28%20%5Cpm%200.012%20%25" /> och en kolkontamination på <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?0.41%20%5Cpm%200.023%20%25" />. Förångade kopparfilmer finnes att ha en syrekontamination på <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?0.45%20%5Cpm%200.018%20%25" /> och en kolkontamination på <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?0.31%20%5Cpm%200.013%20%25" />. Spår av guld (<img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Cprec%200.5%20%25" />) hittades enbart i sputtrade filmer. Spår av väte kunde också hittas i både sputtrade och förångade filmer. De förångade filmerna finnes ha lägre syrekontamination än de sputtrade filmerna, men tillverkningsprocessen som används i projektet vid tillverkning av förångade filmer är inte lämplig att använda i produktion av tunnfilmer med specifika tjocklekar då det saknas data för att kunna hitta en depositionshastighet. Totalt sett är uppställningen kapabel att producera filmer av adekvat kvalitet för att de ska kunna användas inom avdelningen för produktion av filmer för forskning.

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The integration of hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) with plastic substrates enables emerging technologies such as flexible organic light emitting diode (OLED) displays. Current a-Si fabrication processes, however, create residual thin film stress that affects the underlying flexible substrate due to its high mismatch in the coefficient of thermal expansion resulting in a dimensional instability for fabricating TFTs on large area flexible substrates. The motivation of this thesis is to reduce this non-uniformity and improve fabrication throughput of bottom-gated inverted-staggered a-Si:H TFTs on flexible substrates. This thesis therefore encompasses the study of overlay misalignment on TFTs over 3 inch flexible substrates and investigates the electrical characteristics of the TFTs fabricated on plastic platforms. To reduce overlay misalignment of TFTs fabricated on flexible substrates, a plastic-on-carrier lamination process has been developed. The technique comprises of a polyimide tape to attach a 125 um-thick poly-ethylene-napthalate (PEN) flexible substrate to a rigid carrier. This process has been used to minimize stress induced strain of the PEN substrate during the fabrication process; strain, which has been observed after processing a-Si:H TFTs on free-standing substrates. This technique would in turn assist in fabricating uniform stacked-layers as required for a-Si:H TFT fabrication on the PEN substrates. Overlay misalignment is measured after each of the 5 consecutive lithographic steps at 4 corner-most edges of the PEN substrates using a standard optical microscope. Results have shown an overlay misalignment reduction from 21 um to 2 um on average based on the TFTs fabricated on free-standing flexible substrates while ensuring a centre alignment accuracy of +/- 0.5 um. Post fabrication adhesive removal to separate the PEN substrate from the rigid carrier has been accomplished by sample immersion in acetone. The results present a significant increase in fabrication throughput by reducing lithographic overlay misalignment such that the resolution of large-area flexible electronics would be enhanced. Electrical characteristics show the average performance of a-Si:H TFTs with an ON/OFF current ratio of 10^8, field effect mobility of ~0.8 cm^2/Vs, and gate leakage current of 10^-13 A.

Organic semiconductors are envisioned to have widespread applications in flexible displays, radio-frequency identification (RFID) tags, bio- and chem-sensors, as well as organic solar cells. Polymer semiconductors are particularly suitable for the low-cost manufacture of organic electronics using printing techniques due to their excellent solution processability and mechanical properties. This work focuses on the development of two novel building blocks, IBDF and DTA, which can be used for the construction of high performance organic thin film transistors (OTFTs) and organic photovoltaics (OPVs). Two copolymers, P6-IBDF-T and P5-IBDF-T, and a homopolymer P6-IBDF were prepared using the IBDF building block. Copolymer P6-IBDF-T has been prepared via the Stille-coupling polymerization. This polymer exhibits a small band gap of 1.36 eV with HOMO/LUMO energy level of -5.69 eV/-4.43 eV. P6-IBDF-T showed stable electron transport performance in encapsulated thin film transistors and ambipolar transport performance in non-encapsulated TFTs. Balanced hole/electron mobilities of up to 8.2 ??10-3/1.0 ??10-2 cm2V-1s-1 was achieved in bottom-contact, bottom-gate organic thin film transistors. In addition, the broad absorption of the polymer over the UV-Vis range suggested that this polymer is suitable for applications in solar cells. The effect of conjugation on mobility and UV-vis spectra of the polymer was studied by comparing P5-IBDF-T with P6-IBDF-T. The ideal of indirect electron transition was proposed to explain the difference between UV-Vis light absorption spectra for these two polymers. DTA building block was used to construct four D-A copolymers, namely PDTA-T, PDTA-BT, PDAT-BTV, and PDTA-TT. These polymers were characterized by UV-Vis, CV, DSC, TGA, AFM and XRD. Device performance was also investigated on OTFTs. The device performance of DTA based polymer increased as the area of electron donor increase from T in PDTA-T to BTV in PDTA-BTV. PDTA-BTV exhibits hole mobility of 1.3??10-3 cm2 V-1 s-1 with Ion/Ioff value of ~103-4 in bottom-contact, bottom-gate organic thin film transistors. All DTA based copolymers exhibited small optical bandgaps (1.18 ??? 1.27 eV) and required none or moderate thermal treatment during fabrication process. These make them promising candidates for cost-effective OPV applications.

In this thesis, titanium dioxide (TiO2)-based thin film photocatalysts of different morphologies were synthesized and studied for their photoelectrocatalytic and photocatalytic properties. The superhydrophilicity of selected TiO2 films were also assessed. The work started with the synthesis of nanocrystalline TiO2 thin films with minimal porosity. A photoelectrocatalytic study was performed to evaluate the films?? photocurrent response in the presence of various organic compounds. At low concentrations, the amount of photocurrent generated was found to be influenced by the molecular structure of the organic compounds. As the concentration increased, the photocurrent response became dependent on the level of interaction of the organic compounds and their partially degraded intermediates with the TiO2 surface. Highly dispersed platinum (Pt) were added onto TiO2 films by a photo-deposition method, and their photocatalytic and photoelectrocatalytic activities were assessed using a novel thin-layer photo(electrochemical)-catalytic system. The system allowed the photocurrent data that originated from the photoelectrocatalysis process to be collected in the reaction cell, and the amount of organic compound being oxidized to be quantified. The Pt deposits were found to enhance photocatalysis by increasing the photogenerated charge-carriers separation, but conversely they retarded the photoelectrocatalysis process. The next part of the work covered the development of mesoporous TiO2 films via the evaporative-induced self-assembly procedure. The structural characteristics of the films were altered by controlling the relative humidity and temperature during the coating and thermal treatment processes. The effect of key structural parameters, such as film porosity, surface area and crystallinity, on the photoelectrocatalytic activity was investigated. These parameters were found to affect the photoelectrocatalysis because the performance of a catalyst in the photoelectrocatalysis application relies strongly on attributes such as the photocatalyst particles?? interconnectivity and the contact to the conducting substrate. The last part of this thesis demonstrated the effort undertaken to improve the UV-induced superhydrophilic effect of a TiO2 film. A multilayer structure of TiO2 nanoparticles was assembled to create a novel TiO2 film that required no UV-activation to induce a uniform water sheeting across its surface. The novel TiO2 thin film exhibited stable superhydrophilic wetting and anti-fogging behaviors after repetitive cycles of heat and wetting treatment, and this performance was affected by the porosity and surface hydroxyl (-OH) contents.

Thesis (Ph.D.)--Drexel University, 2008. / Includes abstract and vita. Includes bibliographical references (leaves 309-323).