Silicon has been the mainstay of the microelectroncs industry for over four decades. There is no material which can match the balance it affords between cost-benefit, mass consumability, process versatility, and nano-scale electron device performance. It is, therefore, the logical (and perhaps inevitable) platform for the development of integrated opto-electronics - a technology that is being aggressively developed to meet the next generation of bandwidth demands that are already beginning to strain interconnect architectures all the way down to the intra-chip level. While silicon-based materials already provide a variety of passive optical functionalities, the success of a genuine silicon-based optoelectronics will depend upon the ability of engineers to overcome those limitations in the optical properties of bulk silicon that occur at critical junctions in device requirements (eg. modulator and laser). Such solutions must not render the device processing incompatible with CMOS, for then the "silicon advantage" is lost. Achieving reliable and efficient electroluminescence in silicon remains the most intractable of these problems to date. Reliability problems in recently developed light emitting devices operating near a wavelength of 1.54 f..Lm, based on the thermally induced formation of silicon nano-clusters in erbium-doped silicon rich silicon oxide thin films, has reinforced the need for a further understanding of the luminescence mechanisms in this material. Indeed, the efficient and stable sensitized photoluminescence from Er3+ ions (near the telecom wavelength), embedded in an oxide matrix, based on a quasi-resonant energy transfer from nanostructured silicon, has the potential to make possible compact waveguide amplifiers and thin film electroluminescence. This thesis represents a study into the luminescence mechanisms in erbium-doped silicon oxide (SiOx, x~2) thin films grown by electron cyclotron resonance plasma enhanced chemical vapour deposition. Importantly, the film growth relies on in-situ erbium doping through the cracking of a volatile organalanthanide Er(tmhd)3 source. Rutherford backscattering spectroscopy has been used to map the film composition space generated from an ECR-PECVD parameter subspace consisting of precursor gas flow rates and the erbium precursor temperature. The response of the film photoluminescence spectra in both visible and infrared bands consistenly reveals three classes of luminescence centres, whose relative ability to emit light is shown in this study to exhibit a considerable degree of variability through the control of the film composition, subsequent thermal anneal temperature, duration, and process ambient. These three classes consist of optically active Er3 + ions, silicon nano-clusters phase separated during thermal annealing, and oxide-based defects (which may additionally include organic chromophores). The latter two of these species show the ability to sensitize the Er3 + luminescence. In fact, sensitization by intrinsically luminescent defects is a rarely studied phenomenon, which seems to be an important phenomenon in the present films owing to a potentially unique Er incorporation complex. To further investigate the ability of the oxide defects in this regard, an optimally luminescent film has been subject to a damaging ion irradiation to induce a photoluminescence quenching. The subsequent recovery of this luminescence with stepwise isochronous annealing has been correlated with Doppler broadening positron annihilation spectroscopy measurements made with a slow positron beam. Irradiation to a sufficiently high fluence has demonstrated a unique ability to de-couple luminescent sensitizers and Er3+ ions, producing enhanced blue and violet emissions. / Thesis / Master of Science (MS)

Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (p. 241-266). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Title from PDF t.p. (viewed Feb. 3, 2010). Additional advisors: Derrick R. Dean, Sergey B. Mirov, Sergey Vyazovkin, Mary Ellen Zvanut. Includes bibliographical references (p. 122-145).

This work investigates the use of the novel electric field assisted chemical vapour deposition (EACVD) process in the production of titanium dioxide thin films for photocatalytic applications on glass substrate. This work looks into the interaction of applied electric fields with the precursor species during the aerosol assisted chemical vapour deposition (AACVD) and atmospheric pressure chemical vapour deposition (APCVD) reaction of Titanium isopropoxide (TTIP) and Titanium (IV) Chloride (TiCl4) with different solvents. The electric field was generated by applying a potential difference between two fluorine-doped tin oxide glass sheets. The electric field was varied between 0 – 3000 Vm-1. The deposited films were analysed and characterized using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, atomic force microscopy, UV-vis spectroscopy, water-contact angles and resazurin photcatalytic testing. It was observed that the application of electric fields produced changes in the morphology, particle size, growth rate, crystal orientation and crystal phases. Generally, films produced under the influence of the electric fields showed higher photo-activity than films produced in absence of electric fields. The deposited films produced from the electric field assisted aerosol chemical vapour deposition (EAACVD) showed higher photo-activity with applied AC electric fields than with applied DC electric fields. Likewise, they showed higher photo-activity than the deposited films produced from the electric field assisted atmospheric pressure chemical vapour deposition (EAAPCVD) with applied AC electric fields. The results obtained were explained by the interaction mechanisms between the electric fields and the precursor species, which differ depending on the CVD technique used. Although titanium dioxide photo-activity is comprised by a combination of factors, it was observed that an optimum can be obtained by varying both experimental conditions and field strength. In particular, optimum results were obtained for deposited films which showed long-shaped particles, reduced particle size and high preferential orientation in the anatase (004) plane. Electric field assisted chemical vapour deposition (EACVD) shows a great potential for the improvement of commercial products available in the market such as self-cleaning and antibacterial surfaces.

The work in this thesis examines the effects of the application of oxide coatings on the performance of the single crystalline silicon photovoltaic solar cells. A variety of potential oxide materials for solar cells performance enhancement are investigated. These films are silicon oxide, titanium oxide and rare earth ion-doped gadolinium oxysulfide phosphor. This study compares the electrical characteristics, optical properties and surface chemical composition of mono-crystalline silicon cells before and after coating. The first study investigates the potential for using single and double layers of silicon oxide films produced by low-temperature Plasma Enhanced Chemical Vapour Deposition (PECVD) using tetramethylsilane as a silicon precursor and potassium permanganate oxidising agent for efficiency enhancement of solar cells at low manufacturing cost. Deposition of the films contributes to the increase of the conversion energy of the solar cells on one hand while the variety of colours obtained in this study can be of great importance for building-integrated photovoltaic application on the other hand. The obtained results demonstrated a relative enhancement of 3% in the conversion efficiency of the crystalline silicon solar cell. In the second study, the effects of using a single layer of titanium oxide and a stack of silicon oxide and titanium oxide on the performance of solar cell are demonstrated. Moreover, this study shows the use of different sputtering configurations and oxidation methods. The experimental results showed a relative enhancement of 1.6% for solar cells coated with a stack of silicon oxide/titanium oxide. In the third study, silicon cells were coated with a luminescent layer consisting of down-converting phosphor, gadolinium oxysulfide doped with erbium and terbium, and a polymeric binder of EVA using doctor-blade screen printing technique. A relative enhancement of 4.45% in the energy conversion efficiency of PV solar cell was achieved. Also, the effects of combining silicon oxide layers together with the luminescent composite are also presented in this study.

Electrical and optical properties of the (N,Ga)-doped ZnO films have been studied. Three growth regions were identified to obtain ZnO films with different conduction types depending on the N/Ga flux ratio in doping process. The PL spectra show evident competition between neutral-donor bound exciton (D0X) and neutral-acceptor bound exciton (A0X) according to the N/Ga ratio. From the temperature-dependent PL spectra, the nitrogen acceptor level was identified to be about 126 meV in (N,Ga)-doped p-type ZnO. / For nitrogen doping of ZnO thin films, DMHy was used as the nitrogen dopant source. A narrow temperature window from about 500°C to 550°C for efficient nitrogen doping was identified. However, p-type ZnO was not obtained by nitrogen mono-doping, which results from the low solubility of N and the self-compensating effect of native defects, and/or N-induced complexes. By co-doping N with Ga in proper ratios, p-type ZnO films were successfully achieved with a high hole concentration of 3.51 x 1017 --2.41 x 1018cm-3, Hall mobility of 1.1 --4.29 cm2/V-s and resistivity of 0.6 -- 16.2 O cm. But the conduction type critically depends on the growth conditions. Based on the successfully fabrication of (N,Ga)-doped p-type ZnO, a p-ZnO:(N,Ga)/n-ZnO homojunction was fabricated. The I-V measurement shows clear rectifying behavior with a turn-on voltage of about 3.7 V. / Further investigation of the effect of N/Ga doping ratios on the conduction type of ZnO samples reveals that successful doping depends much on engineering a stable local chemical bonding environment. Under mono-doping conditions (via N-Zn4), nitrogen solubility is limited and nitrogen acceptors are readily compensated by native donors and/or N-related donors; under appropriate N/Ga flux ratios, cluster-doping (via Ga-N3O and Ga-N4) can be realized to achieve p-type ZnO; while excessively high N/Ga ratios cause the doped ZnO n-type conductivity again, which may be because that under excessively high N/Ga ratio range, N-Zn4 configuration dominates and thus cause more N-related donors and degrade the ZnO film quality, similar as the mono-doping case. By tuning the N/Ga ratio in doping, it is expected to create appropriate chemical environments to enhance the formation of desired dopant species for stable p-type ZnO. / In this work, Metal-organic chemical vapour deposition (MOCVD) growth of ZnO and its p-type doping have been studied. The group V element N was used as primary dopant to make ZnO p-type. In the growth of ZnO by MOCVD, it was found that the structural and morphological properties of deposited ZnO strongly depend on growth conditions. Low VI/II ratio and high growth rate favor the growth of ZnO nanostructures (nanowires, nanobelts); while high VI/II ratio and low growth rate favor the growth of ZnO thin films. / The semiconductor ZnO is currently gaining intense interest in the research community because of its prospect in optoelectronic applications, such as blue/ultraviolet emitters and detectors, and high speed electronic devices. However, making reliable and reproducible p-type ZnO is still a bottleneck, which impedes the practical application of ZnO-based devices. The difficulty is mainly due to the self-compensation effect of native defects and the low solubility limit of acceptor dopants. Although substantial research is currently being carried out worldwide towards this goal, the effective p-type dopant and its doping process have not yet been identified. / Wang, Hui. / "Apr 2008." / Adviser: Aaron H. P. Ho. / Source: Dissertation Abstracts International, Volume: 70-03, Section: B, page: 1860. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

acase@tulane.edu

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 204-217).

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 140-151).

The physical properties of cadmium sulfide and zinc oxide thin films, deposited from aqueous solution, were investigated using electron and x-ray diffraction techniques. The conventional method and two new methods were used to deposit cadmium sulfide thin films. Moreover, a new method for the deposition of zinc oxide was devised. Experiments were conducted on the cadmium sulfide thin films in order to make their semiconducting properties favorable for use as solar cells. Cds-Cu(x)S solar cells were fabricated, and their I-V characteristic curves plotted, using an X-Y recorder. The photovoltaic effects in chemically deposited Cds films have been clearly demonstrated.