Zugl.: Braunschweig, Techn. Univ., Diss., 2008

Thesis (Ph. D.)--University of Massachusetts Amherst, 2009. / Includes bibliographical references (p. 103-107). Print copy also available.

Universiẗat, Diss., 2004--Düsseldorf.

Techn. Universiẗat, Diss., 2000--Berlin.

Universiẗat, Diss., 2003--Saarbrücken.

Alternative plasmonic materials of Transparent Nitrides and Conductive Oxides (TNCOs) including Indium Tin Oxide (ITO), Al-doped ZnO (AZO) and Titanium Nitride (TiN), have been proposed as novel material platforms for Si-compatible plasmonics and metamaterials, showing enhanced light-matter interaction over a broad spectral range. It has been recently shown that these materials feature reduced optical losses compared with conventional noble metals such as Au and Ag in the visible and near-infrared spectral range. However, it is still an open challenge to tailor the structural and optical properties of these materials, and to further reduce their optical losses, in order to effectively utilize them in photonic devices. In this thesis work, I demonstrate wide tunability of the optical and structural properties of ITO, AZO and TiN thin films, by using post-deposition annealing treatments, enabling significant reduction of their optical losses. By measuring the optical bandgaps of the investigated materials, I show that the tunability of the optical properties originates from the modulation of the free carrier concentration induced by the annealing treatment. Moreover, I perform XRD characterization of the fabricated films, indicating that the annealing also effectively tunes the grain size, which is consistent with the change of the optical properties. Eventually, I investigate the role of the annealing gases for ITO and AZO, demonstrating that free-carrier modulation in ITO and AZO is due to the change in the density of oxygen vacancies after post-deposition annealing. In particular, TNCOs possess epsilon-near-zero (ENZ) condition in near-infrared range with optical loss ε^"<1, thus providing enhanced internal fields in the medium at the ENZ condition. In collaboration with Prof. Nader Engheta and the previous post-doc in our group Dr. Antonio Capretti, we demonstrate enhanced second-harmonic generation (SHG) and third-harmonic generation (THG) from ITO thin films driven by ENZ condition. It results that the SHG generation efficiency is comparable with that of a crystalline quartz plate of thickness 0.5 mm, and that the THG generation efficiency is ∼600 times larger than crystalline silicon. As an application for the fabricated TiN material, I investigate PL intensity and lifetime in Hyperbolic Metamaterials (HMMs) coupled with emitting Si Quantum Dots (QDs). In collaboration with Hiroshi Sugimoto in Prof. Minoru Fujii’s group and the previous post-doc in our group Dr. Sandeep Inampudi, we demonstrate up to 1.6-times enhanced decay rate of QDs emission. Photonic devices based on TNCO plasmonic materials offer an effective approach for the engineering of novel Si-based photonic devices with enhanced light-matter coupling over a broad spectral range. As an application for the fabricated ITO, in collaboration with Hongwei Zhao in Prof. Jonathan Klamkin’s group, electro-absorption modulators are numerically investigated to show high extinction ration of greater than 6dB, while insertion loss is less than 1.3dB for wavelength range from 1.25 µm to 1.42 µm. Additionally, we demonstrate tunable optical properties of ITO thin films in mid-infrared spectrum by thermal annealing of ITO in oxygen environment. In collaboration with Sajan Shrestha and Adam Overvig in Prof. NanFang Yu’s group, we fabricate 2D periodic arrays of ITO and show wide tuning of plasmonic resonances of ITO nanostructure from 4 µm to 10 µm. Combining with the tunability of ITO thin films in near-infrared, the ITO material platform provides a promising method for the control and engineering of Si-based tunable plasmonic and metamaterial devices in the infrared spectrum. Finally, in collaboration with my colleague Ren Wang, we experimentally demonstrate silicon nanodisk arrays with tunable anapole mode excitation in the visible spectrum. The proposed high index nanostructures can be used to enhance absorption rate for applications in semiconductor photodetector.

This practice-based thesis undertakes research into the contemporary aesthetic of interactive media art, in order to propose a useful practical model of interactivity founded on a critical approach to both existing theory and practice. It proceeds from the identification of a primary lack in contemporary aesthetics that arises from the predominantly materialistic comprehension of technologically-mediated artworks. The thesis establishes a new model for interactive art that offers an immaterial engagement with technology at a locus where cognition and the aesthetic intertwine. This model is constructed following a revision of both the theory and practice of interactive media art, which identifies a materialistic bias of technology-mediated art production caused by a confused concept of technology as both tool and medium. This investigation confines itself to the last forty years of interactive art and the new model of spectatorship that has accompanied it. The main objective of what follows from this investigation is an account of agency in the artist and spectator interrelationship. In the context of technologically based artworks various approaches to spectatorship have frequently remained within the constraints of the traditional model of art that inherently drew on a separation between body and mind. It is argued in this thesis that neither the technology nor the participation itself, but the cognitive interconnection between 'artist-artwork-spectator' produces the primary aesthetic dimension of interactive media art. In this respect, not the physical object creation but the aestheticisation of this triangle produces the here identified immaterial/cognitive experience of the spectators. This can be achieved when the technology is applied as a transparent medium one of the core concepts introduced in this thesis which can facilitate an aesthetic quality or meaning creation through technology. The 'transparent medium' enables the cognitive-based experience production, which is identified as the immersive flow of the spectator's aesthetic experience. As such, the re-evaluation of the artist- spectator interrelationship proposes a new immaterial model of art which is called the Transparent Act. The introduction of the Transparent Act leads to the main intervention of this thesis which lies in an effort to recover a lost dimension in interactive media art. A recovery of this dimension enables access to a knowledge practice which is not necessarily located in ordinary cognitive experiences but in unfamiliar conscious states that can be compared to accounts of so-called spiritual experiences. The model of the Transparent Act is concurrently applied as a practise-based intervention and proof-of-concept in a major installation, the Mind Cupola. This artistic and technological contextualisation of the original intervention of this thesis is exemplified as an affective environment which aims for an immediate cognitive affection of the spectator by generating mechanical and audio-visual effects in the spectator's 'mind'. The artistic system uses special face analysis techniques to close the feedback loop and affect the spectator through the analysis of her/his reactions. The installation is built upon a 'passive' modality of interaction in which the spectator contributes to the artwork with subtle, cognitive-based interactions which are fed back through a complex open response system. The implementation of cognitive feedback loops, also described as the fractal structure in the spectator's cognition, constitutes the essential transparent medium through which the previously lost immaterial dimension of a spiritual-like aesthetic experience in interactive media art is achieved. The thesis concludes with suggestions of further applications including the evaluation of technologically mediated artworks.

A methodology was developed for isolation and transfer of 1-4 monolayer graphene from both Cu and Ni foil and Ni/SiO2/Si layered substrate types for use as electron transparent windows in environmental electron microscopy and spectroscopy. The graphene membranes were transferred onto disc "frames" made of stainless steel containing 3-10 μm diameter apertures. Such frames "windowed" with the graphene membrane are assembled into the custom designed environmental cell (e-cell) which contain a specimen immersed in the desired liquid or gaseous environment, and are compatible for imaging with a conventional scanning electron microscope (SEM) (in this case, a Hitachi 4500 SEM). Gold nanoparticles (50 nm) colloidal in water served as model specimens and were observed inside the e-cell using both secondary electron and backscattered electron detectors. An imaging induced radiolysis of water was observed at higher electron doses, which manifested itself in the formation of bubbles growing and coalescing under the enclosed graphene surface. Key SEM imaging parameters responsible for driving the radiolysis phenomena were addressed.

Organic solar cells (OSCs) have attracted significant attention due to their potential of large area solution fabrication capability at low-cost. For bulk heterojunction (BHJ) OSCs, a thin film of transparent conducting indium tin oxide (ITO), coated on glass or flexible plastic substrate, is widely used as a front electrode. However, indium is not abundant on Earth. Its price has increased continuously over the past 10 years and will likely become an obstacle for the commercialization of OSCs at low cost. Aluminum-doped zinc oxide (AZO) is a promising ITO alternative due to its advantages of high electric conductivity, optical transparency, non-toxicity and low cost. However, reports on OSCs using AZO electrode are quite limited, due to the relatively lower power conversion efficiency (PCE) of AZO-based OCSs as compared to that of ITO-based OCSs. This work focused on studies of high performance AZO-based OSCs through AZO surface modification, absorption enhancement and process optimization. The optical and electronic properties of AZO film including transmittance, sheet resistance, surface morphology and surface work function were characterized. AZO-based OSCs with conventional and inverted structures were fabricated. It was found that AZO-based OSCs with inverted structure demonstrated superior performance than the ones with conventional structure. The inverted structure avoids the use of acidic PEDOT:PSS hole transporting layer, allows the improving of the absorbance of the OSCs and therefore its efficiency. An AZO front transparent cathode was used for application in high performance inverted BHJ OSCs. The photoactive layer consisted a blend of poly[[4,8-bis[(2- ethylhexyl)oxy] benzo [1,2-b:4,5-b'] dithiophene-2,6- diyl][3-fluoro- 2-[(2-ethylhexyl) carbonyl]thieno[3,4-b]thiophenediyl]](PTB7):3'H-Cyclopropa[8,25][5,6]fullerene- C70- D5h(6)-3'-butanoicacid, 3'-phenyl-, methyl ester (PC70BM). A structurally identical control OSC having an ITO front cathode was also fabricated for comparison studies. The structure of OSCs was optimized to achieving absorption enhancement in the active layer. AZO and ITO were modified with a 10 nm thick solution-processed ZnO interlayer to facilitate the efficient electron extraction. The results revealed that bilayer AZO/ZnO and the ITO/ZnO cathodes possess similar electron extraction property. AZO layer has a transparency cutoff at wavelength < 380 nm, results in a slight decrease in the short-circuit current density (JSC). However, the decrease in JSC is very small because the main energy of solar irradiation falls in the spectrum with wavelength > 380 nm. It shows that AZO-based OSCs have a promising PCE of 6.15%, which is slightly lower than that of a control ITO-based OSC (6.57%). AZO-based OSCs, however, demonstrate an obvious enhancement in the stability under an ultraviolet (UV)-assisted acceleration aging test. The significant enhancement in the stability of AZO-based OSCs arises from the tailored absorption of AZO electrode in wavelength < 380 nm, which serves as a UV filter to inhibit an inevitable degradation process in ITO-based OSCs due to the UV irradiation. In order to further investigate the degradation mechanism of OSCs under UV exposure, the change in charge collection characteristics of the OSCs made with ITO/ZnO and AZO/ZnO front cathode before and after UV exposure was examined. It was found that there was an obvious decrease in the charge extraction efficiency of ITO-based OSCs after UV exposure, while there was no observable change in the charge extraction efficiency of OSCs made with AZO/ZnO cathode under the same acceleration aging test. This work demonstrates that AZO is a suitable ITO alternative for application in OSCs, offering an improved device stability, comparable PCE and cell fabrication processes with an attractive commercial potential.

Denna rapport behandlar hur aggregattabeller kan administreras av lagrade procedurer i en databasserver. Målet är att skapa en parser som kan hantera aggregattabeller transparent för de applikationer som använder databasen. För att kunna uppfylla transparens måste denna parsern kunna dra slutsatser om databasstrukturen. Genom att identifiera nödvändig metadata och sedan placera den i ett repository, kan parsern dra sådana slutsatser. Identifiering redovisas i rapporten genom en metadatastudie, vilken ligger till grund för metodens genomförande. I rapporten diskuteras olika metoder för att uppnå en transparent lösning. Den metod som sedan implementeras, är en lagrad procedur. I rapporten dras slutsatsen att det är möjligt att skapa en lagrad procedur i databasservern, som kan utföra de uppgifter som krävs för att hantera aggregattabeller på ett transparent sett.