Spelling suggestions: "subject:"thin fim fabrication"" "subject:"hin fim fabrication""
1 |
The development of equipment for the fabrication of thin film superconductor and nano structuresButtner, Ulrich 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The nano-age is more about the mesoscopic phenomena, than those occurring at molecular
and atomic level, which have been studied by chemists and physicists for more
than a hundred years. Nanotechnology is currently one of the most active fields being
explored in many different disciplines by many scientists across the world. In this
research field, it is imperative to continually create more effective and superior methods
to build smaller and smaller electronic devices, circuits and sensors. Technology
is being improved continually and, specifcally at our university, there was a need to
improve our device manufacturing facility. The aim of this work was to create a new
sputtering system, build a dry etching system and to make modifications to upgrade
existing equipment. This work has been done to produce nano structures or devices
and, most importantly, to save costs.
New systems and equipment have been built to keep up with the progress in this field.
In order to understand the significance of the different types of equipment used in
the fabrication of thin film superconductor layers, an overview will be given of the
complete process of manufacturing a patterned Josephson junction. The apparatus
used will be described and critically analyzed, whereby the shortfalls in design will be
highlighted and improvements shown. Some of the equipment, such as the plasma laser
deposition system, the lithography system and the test facility existed before and has
been modified. Newly designed systems were built to further improve the quality of
our thin film superconductors; these include the inverted cylindrical magnetron (ICM)
sputtering system, the argon ion mill and the incandescent substrate heater.
Finally, the results of the improved thin films and structures will be shown. To summarize:
The entire process was analyzed and upgraded, resulting in an improved device
manufacturing facility. / AFRIKAANSE OPSOMMING: Die nano-era het aangebreek en nanotegnologie is tans een van die mees aktiewe en diverse
navorsingsvelde wat wetenskaplikes wêreldwyd ontgin - hoofsaaklik as gevolg van
nuwe verskynsels op molekulêre en atomiese vlak. In die nanotegnologie-navorsingsveld
is die vereiste dat daar voortdurend meer effektiewe metodes gevind moet word om die
al hoe meer miniatuurwordende elektroniese meganismes met verbeterde energieverbruik,
spoed en ruimtebesparende vermoëns tot stand te bring.
Dit is duidelik dat in hierdie toonaangewende navorsingsveld, waar tegnologiese ontwikkeling
voorturend en snelgroeiend is, dit dikwels vinniger is om reeds bestaande
toerusting aan te pas en te moderniseer ten einde in pas te bly met nuutontwikkelde
en ontwikkelende tegnologieë. Die doel van die werk verrig, wat hier beskryf word, was
om 'n nuwe deponeerstelsel, sowel as 'n droogets stelsel te bou. Bestaande apparaat is
opgradeer deur verandering aan te bring. Die uiteintelikke doel is die vervaarding van
beter nano-strukture, en terselfde tyd om kostes te bespaar.
Nuwe stelsels en toerusting is gebou om tred te hou met tegnologiese vooruitgang. Om
die belangrikheid van die verskillende tipes toerusting wat in die vervaardiging van
dunlaag- supergeleierlae gebruik word te verstaan, sal 'n oorsig van die volledige vervaardigingsproses
van 'n Josephson-patroon gegee word. Die apparaat wat gebruik is,
sal beskryf en krities ontleed word en die tekorte in ontwerp sal uitgelig word, terwyl
verbeterings aangetoon sal word. Sommige van die toerusting het voorheen bestaan
en is aangepas, byvoorbeeld die plasmalaser-neerleggingstelsel, die litografiestelsel en
die toetsfasiliteit. Nuwe ontwerpstelsels is gebou om die gehalte van ons dunlaagsupergeleiers
verder te verbeter. Dit sluit die silindriese plasma deponeer stelsel, die
Argon-ioon bron en die substraatverwarmer in.
In hierdie tesis word daar eerstens 'n oorsig gegee van die totstandkomingsproses van
'n supergeleier kwantum-interfensiemeganisme, beginnende met dunlaagneerslag van
YBCO (Yttrium, Barium en Koperoksied). Die oorsig word gevolg deur 'n stap-virstap
beskrywing van elke daaropvolgende proses wat lei tot die voltooiing van die
meganisme. Daarna word die toetsprosedure van die dunlaag en instrumente verduidelik.
Bykomende veranderinge wat aan bestaande instrumente aangebring is (ten einde
die dunfilmlae te verbeter en die toetsfasiliteit op te gradeer) word ook bespreek.
Daar sal ook verwys word na artikels wat in verskeie joernale verskyn het oor die
vernuwende aanpassings en sisteme wat in hierdie tesis verduidelik word. Ten slotte
sal die resultate van die verbeterde dunlae en strukture getoon word. Kortom: die hele
proses is ontleed en opgegradeer om 'n verbeterde apparaatvervaardigingsfasiliteit tot
gevolg te hê.
|
2 |
Optimization of Solid Phase Microextraction for Determination of Disinfection By-products in WaterRiazi Kermani, Farhad January 2012 (has links)
A new technique for sample preparation and trace analysis of organic pollutants in water using mixed-phase thin film (MPTF) devices, combined with direct thermal desorption, cold trapping, gas chromatography-mass spectrometry (GC-MS) is presented for the first time. Two novel analytical devices, Carboxen/polydimethylsiloxane (CAR/PDMS) and polydimethylsiloxane/divinylbenzene (PDMS/DVB) TF samplers were fabricated using spin coating technique and glass wool fabric mesh as substrate. The samplers were easily tailored in size and shape by cutting tools. Good durability and flat-shape stability were observed during extractions and stirring in water. The latter characteristic obviates the need for an extra framed holder for rapid thin film microextraction (TFME) and makes the samplers more robust and user-friendly. The analytical performance of the MPTF devices was satisfactorily illustrated and compared with those of solid phase microextraction (SPME) fibers and PDMS thin film membrane using water samples spiked with seven N–nitrosamines (NAs), known as disinfection by-products (DBPs) in drinking water. Marked enhancement of extraction efficiencies (typically more than one order of magnitude) for the N-nitrosamines, including the hydrophilic ones, was obtained with the MPTF devices under generally pre-equilibrium conditions, compared to the SPME fibers and PDMS thin film membrane. The analytical results obtained in this study, including linearity, repeatability and detection levels at low ng/L for the tested compounds, indicate that the new thin film devices are promising for rapid sampling and sample preparation of trace levels of polar organic pollutants in water with sensitivities higher than SPME fibers and with a wide application range typical of mixed-phase coatings. The user-friendly format and robustness of the novel devices are also advantageous for on-site applications, which is the ultimate use of thin film samplers. Moreover, the thin film fabrication approach developed in this study offers the possibility of making other novel samplers with PDMS or different absorptive polymers such as polyacrylate (PA) and polyethylene glycol (PEG) as particle-free, or as particle-loaded thin films with a variety of adsorptive solid particles.
In another development in the course of this research, the performance and accuracy of the SPME fiber approach for sample preparation of selected DBPs were demonstrated and compared with the conventional liquid-liquid extraction (LLE) method by real drinking water samples analysis in collaboration with Health Canada. Four regulated trihalomethanes (THMs) and seven other DBPs known as priority by-products, including four haloacetonitriles, two haloketones and chloropicrin, were analyzed in real samples during two separate comparative studies. In each study, duplicate samples from several water treatment and distribution systems in Canada, collected and stabilized under the same protocol, were analyzed in parallel by two independent labs; in the University of Waterloo by an optimized headspace SPME-GC-MS and in Health Canada by a LLE-GC-ECD (electron capture detection) method equivalent to EPA 551.1. The values for the concentration of the analytes in the samples obtained by the two methods were in good agreement with each other in majority of the cases indicating that SPME affords the promise of a dependable sample preparation technique for rapid DBPs analysis. In particular, it was shown that the SPME fiber approach combined with GC-MS is a fast reliable alternative to the LLE-GC-ECD (EPA 551.1) method for analysis of the regulated THMs in the concentration ranges that are typical and relevant for drinking water samples.
|
3 |
Quasi-Two-Dimensional Halide Perovskite Materials For Photovoltaic ApplicationsAidan Coffey (12481935) 29 April 2023 (has links)
<p>As energy demands for the world increase, the necessity for alternate sources of energy are critical. Just in the United States alone, 92 quadrillion British thermal units (Btu) were used in 2020. As political and geographical pressures surrounding oil increase, along with the growing concern for climate, the drive to explore alternative and renewable means for harvesting energy is on the rise. Solar cells, also known as photovoltaics (PVs), are an attractive renewable source and have been developed as an alternative energy means for over 60 years. When considering losses due to atmospheric absorption and scattering, the Earth’s surface gets about 1000 W/m2 of energy from the sun, which is why there are research efforts around the world trying to maximize the efficiency of solar cells.</p>
<p>Organic-inorganic halide perovskites provide for ideal absorbing layers that feature long carrier lifetime and diffusion lengths, strong photoluminescence, and promising tunability. Furthermore, the solution-processing methods used to make these perovskites ensure that the solar cells will remain low-cost and have easy scale-up possibilities. The main problem perovskites is that they degrade in the presence of water, thus leading to decreased device performance.</p>
<p>In this work two approaches are investigated to increase moisture stability. The first investigates incorporation of thiols as pseudohalides into the 2D perovskite structure. Instead of the theorized perovskite, two novel 2D compounds were created, Pb<sub>2</sub>X(S-C<sub>6</sub>H<sub>5</sub>)<sub>3</sub> (X= I, Br, Cl) and PbI<sub>1.524</sub>(S-C<sub>6</sub>H<sub>5</sub>)<sub>0.476</sub>. While not perovskites, this study gives insight into the effect that the thiol may have on determining structure when comparing –S-C<sub>6</sub>H<sub>5</sub> with –SCN groups. Future work will explore more electronegative thiols that will be used to make moisture resistant, tunable 2D perovskites.</p>
<p>The second approach is to incorporate longer organic ammonium cations into the perovskite structure to produce quasi-2D perovskite films fabricate them into devices. Adding in electronically insulating ligands leads to a stricter requirement for vertically aligned 2D films and special care must be taken to have efficient charge collection. The current field has successfully incorporated short ligands such as butylammonium (BA) into PVs, however the extension to larger and more beneficially hydrophobic ligands has been very scarce. In this work, a novel solvent engineering system is developed to create vertically aligned quasi-2D perovskite absorbing layers based off of a bithiophene ligand (2T). These absorbing layers are then characterized and incorporated into efficient PV devices. Generalizations to solvent conditions related to ligand choice is discussed herein, creating deep insights into incorporating more conjugated ligands into devices.</p>
|
4 |
Sputter Deposited Thin Film Cathodes from Powder Target for Micro Battery ApplicationsRao, K Yellareswara January 2015 (has links) (PDF)
All solid state Li-ion batteries (thin film micro batteries) have become inevitable for miniaturized devices and sensors as power sources. Fabrication of electrode materials for batteries in thin film form has been carried out with the existing technologies used in semiconductor industry. In the present thesis, radio frequency (RF) sputtering has been chosen for deposition of cathode material (ceramic oxides) thin films because of several advantages such as precise thickness control and deposition of compound thin films with equivalent composition. Conventional sputtering involves fabrication of thin film using custom made pellet according to the specification of sputter gun. However several issues such as target breaking are inevitable with the pellet sputtering. To forfend the issues, powder sputtering has been implemented for the deposition of various thin film cathodes in an economically feasible approach. Optimization of various process parameters during film deposition of cathode materials LiCoO2, Li2MnO3, LiNixMnyO4, mixed oxide cathodes of LiMn2O4, LiCoO2 and TiO2 etc., have been executed successfully by the present approach to achieve optimum electrochemical performance. Thereafter the optimized process parameters would be useful for selection of cathode layers for micro battery fabrication.
Chapter 1 gives a brief introduction to the Li ion and thin film solid state batteries. It also highlights the advantages of powder sputtering compared to conventional pellet sputtering.
In Chapter 2, the materials used and methods employed for the fabrication of thin film electrodes and analytical characterizations have been discussed.
In chapter 3, implementation of powder sputtering for the deposition of LiCoO2 thin films has been discussed. X-Ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS) and electrochemical investigations have been carried out and promising results have been achieved. Charge discharge studies delivered a discharge capacity of 64 µAh µm-1 cm-2 in the first cycle in the potential range
3.0-4.2 V vs. Li/Li+. The possible causes for the moderate cycle life performance have been discussed.
Systematic investigations for RF power optimization for the deposition of Li2-xMnO3-y thin films have been carried out. Galvanostatic charge discharge studies delivered a highest discharge capacity of 139 µAh µm-1cm-2 in the potential window 2.0-3.5 V. Thereafter, effect of LMO film thickness on electrochemical performance has been studied in the thickness range 70 nm to 300 nm. Films of lower thickness delivered higher discharge capacity with good cycle life than the thicker films. These details are discussed in chapter 4.
In Chapter 5, fabrication and electrochemical performance of LiNixMnyO4 thin films are presented. LMO thin films have been deposited on nickel coated stainless steel substrates. The as deposited films were annealed at 500 °C in ambient conditions. Nickel diffuses in to LMO film and results in LiNixMnyO4 (LMNO) film. These films were further characterized. Electrochemical studies were conducted up to higher potential 4.4 V resulted in discharge capacities of the order of 55 µAh µm-1cm-2.
In chapter 6, electrochemical investigations of mixed oxide thin films of LiCoO2 and LiMn2O4 have been carried out. Electrochemical investigations have been carried out in the potential window 2.0–4.3 V and a discharge capacity of 24 µAh µm-1cm-2 has been achieved. In continuation, TiO2 powder was added to the former composition and the deposited films were characterized for electrochemical performance. The potential window as well as the discharge capacity enhanced after TiO2 doping. Electrochemical characterization has been carried out in the potential window 1.4–4.5 V, and a discharge capacity of 135 µAh µm-1cm-2 has been achieved.
Finally chapter 7 gives overall conclusions and future directions to the continuation of the work.
|
Page generated in 0.1216 seconds