Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-08-07T14:17:51Z No. of bitstreams: 0 / Made available in DSpace on 2015-08-07T14:17:51Z (GMT). No. of bitstreams: 0 / O câncer diferenciado da tireoide (CDT) representa cerca de 90% das malignidades tireoidianas com incidência crescente nas últimas décadas. As modalidades de tratamento incluem tireoidectomia, terapia com 131I (com e sem r-hTSH), radio e quimioterapias. Pouco se sabe sobre os efeitos desses tratamentos em nível celular. O presente trabalho foi proposto com o intuito de avaliar em que extensão a terapia com radioiodo pode causar danos em linfócitos periféricos de pacientes com CDT precedidos ou não com r-hTSH, levando-se em consideração, efeitos agudos, tardios e dosimétricos do 131I (estudo in vivo). Um estudo in vitro também foi realizado em células-alvo de tumores tireoidianos (WRO) por meio de análise de citotoxicidade, genotoxicidade e captação do radioiodo. Para tanto, amostras sanguíneas de pacientes, divididos em 2 grupos (grupo A com r-hTSH + 131I e grupo B somente com 131I) foram coletadas antes, 24h, 1 semana, 1 mês e 1 ano após administração do 131I para análise de aberrações cromossômicas (AC). Curva dose-resposta para 131I in vitro foi elaborada para a estimativa de dose absorvida nos pacientes, comparando as frequências de dicêntricos obtidas in vitro com dados in vivo pelo programa Monte Carlo. A iodoterapia induziu um aumento no número de AC em linfócitos de pacientes com valor máximo 24h após o tratamento, com declínio gradativo ao longo do tempo, com mais danos cromossômicos no grupo B em relação ao grupo A, atingindo níveis similares aos basais 1 anos após a administração do radioido. A frequência de dicêntricos encontrada nos linfócitos de pacientes 24h após o tratamento foi equivalente àquela induzida in vitro (0,354 ± 0,153 MBq/mL para o grupo A e 0,309 ± 0,154 MBq/mL para o grupo B), que corresponde a dose absorvida de 0,8 ± 0,3 Gy e 0,7 ± 0,3 Gy para os grupos A e B, respectivamente, sem significância estatística entre os grupos. As células WRO mostraram um ciclo celular relativamente lento de 96,3h com um cariótipo instável. O ensaio genotóxico mostrou uma radiorresistência relativamente alta (0,07 a 3,70 MBq/mL), sem significância estatística com e sem r-hTSH. No entanto, o ensaio citotóxico, mostrou uma tendência à queda nas concentrações mais altas de 1,85 (p<0,05) e 3,70 MBq/mL (p<0,01) somente na presença de r-hTSH, coincidindo com nível mais alto de captação. Células WRO foram relativamente radiorresitentes também à irradiação externa de 60Co na faixa de dose de 0,2 a 8,3 Gy, com queda gradativa em função do tempo para doses mais altas (10, 20 e 40Gy). Dados obtidos mostraram pouco dano citogenético nos pacientes após a exposição terapêutica com radioiodo, o que sugere um tratamento seguro e eficaz para os pacientes dos dois grupos. Pacientes do grupo A, no entanto, obtiveram uma melhor qualidade de vida com o uso do r-hTSH. Estudos in vitro com irradiação interna (131I) e externa (60Co) com ou sem r-hTSH, apontam a necessidade de uma estratégia terapêutica alternativa para contornar a perda da habilidade das células tireoidianas (WRO) em concentrar o radioiodo, responsável pelo relativo insucesso da iodoterapia em pacientes com CDT. / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Orientador: Fernando Iikawa / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin. / Made available in DSpace on 2018-08-12T12:58:46Z (GMT). No. of bitstreams: 1 Gomes_PauloFreitas_D.pdf: 14344200 bytes, checksum: 55a7f7d3b644c0dc43151a411d53757b (MD5) Previous issue date: 2009 / Resumo: No presente trabalho apresentamos um estudo da luminescência de érbio em nanocristais de silício (nc-Si) e nanofios de óxido de zinco (nw-ZnO). Os nanocristais de silício com érbio são obtidos através do tratamento térmico de filmes finos amorfos de sub-óxidos de silício (SiOx) preparados por rf-sputtering, variando a concentração de Oxigênio e érbio durante o crescimento. O érbio é adicionado aos filmes cobrindo parcialmente a superfície do alvo de silício com pequenos cacos de érbio metálico. Medidas de espectroscopia Raman e microscopia eletrônica de alta resolução (HRTEM) fornecem o tamanho e densidade de nanocristais em cada amostra. Medidas de fotoluminescência (PL) dos nanocristais na temperatura ambiente mostram que o tamanho dos nanocristais varia com a concentração de oxigênio e temperatura de tratamento térmico. A dependência da PL dos nanocristais com a temperatura pode ser entendida considerando a competição entre processos radiativos e não-radiativos. Em amostras com érbio a taxa de recombinação não-radiativa é maior que nas amostras sem érbio. O estudo da PL dos nanocristais e dos íons Er3+ mostra que o Er3+ funciona como um centro de recombinação não-radiativa para a energia proveniente da recombinação de portadores nos nanocristais. Neste caso, parte da energia gerada nos nanocristais é transferida para os íons Er3+ ao invés de ser emitida na forma de fótons. Também é possível observar que a intensidade da PL do Er3+ depende da intensidade da PL dos nanocristais e é maior em amostras contendo nanocristais de ~3nm (que emitem em ~1,5eV), indicando que a transferência é ressonante (com a excitação 4I15/2 ---> 4I9/2 do Er3+ que corresponde a uma energia de 1,5eV). Os nanofios de ZnO com érbio são preparados por deposição vapor-liquid-solid (VLS) e por electrospinning. Em amostras preparadas por VLS, o érbio é depositado sobre os nanofios após sua preparação. No electrospinning um composto organometálico de érbio é adicionado ao polímero precursor. É observada luminescência de érbio quando as amostras são excitadas com um comprimento de onda ressonante com algum nível mais energético do Er3+. Nanocristais de E2O3 são observados por HRTEM na superfície dos nanofios preparados por VLS. Medidas de EXAFS revelam que a vizinhança do Er nessas amostras é idêntica à do óxido Er2O3, indicando que não ocorreu dopagem substitucional do ZnO. / Abstract: We present a study of erbium luminescence in silicon nanocrystals (nc-Si) and zinc oxide nanowires (nw-ZnO). Silicon nanocrystals are produced by annealing of amorphous sub-oxide thin films (SiOx) prepared by rf-sputtering varying the oxygen and erbium concentration during growth. Erbium is added by partially covering the silicon target surface with small pieces of metallic erbium. Raman spectroscopy and HRTEM measurements reveal the size and density of nanocrystals in each sample. Photoluminescence (PL) measurements at room temperature show that the nanocrystal size changes with oxygen concentration and annealing temperature. The PL dependence on the temperature can be understood considering a competition between radiative and non-radiative processes. In samples with erbium the non-radiative recombination rate is higher than in samples without erbium. The study of the nanocrystal and Er3+ PL show that Er3+ behaves as non-radiative recombination centers for excited carriers in the nanocrystals. Part of the energy from the nanocrystals is transferred to Er3+ instead of being emitted as light. The Er3+ PL intensity depends on the nanocrystal PL intensity and is higher in samples containing nanocrystals ~3nm (which emit at ~1.5eV), indicating that the energy transfer is resonant (with the 4I15/2 -----> 4I9/2 Er3+excitation at ~1.5eV) ZnO nanowires were prepared by vapor-liquid-solid (VLS) deposition and by electrospinning. In the VLS method erbium is deposited on the nanowires after growth. In the electrospinning method a metallorganic compound is added to the polymer precursor. Erbium PL is observed when the samples are excited by one of the Er3+ higher transitions. Er2O3 nano-crystals are observed by HRTEM on the surface of the nanowires prepared by VLS. EXAFS measurements in these samples show that the Erneighborhood is identical to that of E2O<>3 indicating that there was no substitutional / Doutorado / Física / Doutor em Ciências

Orientador: Mônica Alonso Cotta / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-19T18:21:16Z (GMT). No. of bitstreams: 1 Oliveira_DouglasSoaresde_M.pdf: 3151118 bytes, checksum: 954bfe85e80e3ae53e5e5c87d10aa961 (MD5) Previous issue date: 2012 / Resumo: O estudo em nanofios semicondutores é crescente, seja pelo grande potencial de aplicações previsto para eles, seja para entender a dinâmica de formação dessas nanoestruturas. Entretanto, estes dois elementos estão ligados, pois é necessário entender o processo de síntese dos nanofios semicondutores para utilizar todo o seu potencial para aplicações. Neste trabalho, crescemos e estudamos nanofios de fosfeto de índio. Os nanofios foram crescidos pela técnica vapor-líquido-sólido em uma câmara de crescimento epitaxial por feixe químico (CBE). Através de microscopia eletrônica de varredura e microscopia eletrônica de transmissão, obtivemos dados para análise dos nossos resultados. Os parâmetros de crescimento utilizados foram escolhidos de forma que nossos nanofios apresentassem um número bastante significativo de falhas de empilhamento. Utilizamos também nanopartículas catalisadoras muito pequenas (~5nm). Nosso resultado principal foi uma nova morfologia para nanofios. Obtivemos nanofios com variações periódicas de diâmetro sem modificar os parâmetros durante o crescimento. Sendo a distância entre essas variações de diâmetro crescente com o inverso do fluxo do precursor de índio (Trimetil-índio) fornecido durante o crescimento. Análise por microscopia eletrônica de transmissão nos mostrou que essas oscilações periódicas de diâmetro estão associadas com um aumento muito grande no número de falhas de empilhamento e mudanças na fase cristalográfica, de wurtzita para blenda de zinco. Esta morfologia foi modelada por nós como a nanopartícula englobando parcialmente a lateral do nanofio periodicamente durante o crescimento. Nosso modelo é baseado em considerações sobre a competição entre as rotas de incorporação de índio durante o crescimento, as condições termodinâmicas para a nucleação na linha de três fases e estabilidade mecânica da nanopartícula sobre o nanofio durante o crescimento / Abstract: The study of semiconductor nanowires is growing, either due to the great potential for applications or to understand the dynamics of formation of these nanostructures. However, these two elements are linked since it is necessary to understand the synthesis of semiconductor nanowires in order to use all its potential for applications. In this work, we studied and grew nanowires of indium phosphide. These nanowires were grown by the vapor-liquid-solid method on a chemical beam epitaxy (CBE) chamber. They were studied by scanning and transmission electron microscopy. The growth parameters used were chosen so that our NWs presented a significant number of stacking faults and very small (~5nm) catalyst nanoparticles (NPs). Our main result was the observation of a new NW morphology. We have obtained NWs with periodical variations in diameter without any changes in growth parameters during the run. The distance between these oscillations depends almost linearly on the inverse of the Indium precursor flow (TMI) provided during growth. Analysis by transmission electron microscopy has shown that the periodic oscillations in diameter are associated with a very large increase of SF densities and crystallographic phase changes, from Wurtzite to Zinc Blende phase. We have modeled the formation of this morphology as the NP partly wetting the NW sidewalls periodically during growth. Our model is based in considerations of competition between the routes of incorporation of indium during growth, the thermodynamic conditions for nucleation at the three-phase line and mechanical stability of the NP on the NW during growth / Mestrado / Física / Mestre em Física

Orientador: Monica Alonso Cotta / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-04T02:49:32Z (GMT). No. of bitstreams: 1 Bortoleto_JoseRobertoRibeiro_D.pdf: 16802950 bytes, checksum: 1ef2bf92db0b00f30e5db9c5e3e3f34d (MD5) Previous issue date: 2005 / Resumo: Neste trabalho estudamos os mecanismos de crescimento durante a epitaxia de estruturas III-V baseadas na liga InP. Em particular, o principal objetivo foi correlacionar os mecanismos cinéticos durante a nucleação de nanoestruturas auto-formadas com as propriedades estruturais da camada que serve de substrato. Todas as amostras foram crescidas usando um sistema de epitaxia por feixe químico (CBE). De forma geral as amostras foram caracterizadas usando microscopia de força atômica (AFM), microscopia eletrônica de transmissão (TEM), difração de elétrons de alta energia (RHEED) e difração de raios-X. Na primeira parte deste trabalho correlacionamos as mudanças morfológicas nos filmes homoepitaxiais de InP com o padrão de RHEED exibido durante o crescimento epitaxial. Mostramos que as mudanças morfológicas de 3D para 2D com os parâmetros de crescimento estão diretamente relacionadas com as reconstruções superficiais 2x1 e 2x4, respectivamente. Além disso, indicamos que a formação de defeitos morfológicos é devido à dimerização In-P, através da ativação local do mecanismo de bias na difusão. Por outro lado, também investigamos o efeito dos parâmetros de crescimento (temperatura, taxa de crescimento e quantidade de material) na nucleação e auto-formação de ilhas de InP sobre InGaP/GaAs. Na segunda parte desta tese concentramos nossa atenção no efeito das propriedades da camada buffer de InGaP sobre nanoestruturas auto-formadas, principalmente sobre a sua organização espacial. Para tanto, em primeiro lugar, investigamos as propriedades de bulk da liga de InGaP e a dependência com os parâmetros de crescimento. Nossos resultados mostram que o InGaP exibe tanto ordenamento atômico de rede quanto modulação de composição. Estes dois fenômenos estão correlacionados com o tipo de reconstrução superficial. Em específico, a liga de InGaP apresenta ordenamento CuPtB quando a superfície exibe reconstrução superficial 2x1, conforme descrito na literatura. Por outro lado, a reconstrução superficial 2x4 desempenha um papel importante no fenômeno de modulação de composição. De fato, tanto a modulação de composição quanto a morfologia superficial do filme depende dos mecanismos cinéticos de superfície, que envolvem tanto os átomos adsorvidos de In quanto de Ga. Por fim mostramos que a modulação de composição na liga de InGaP pode organizar espacialmente a nucleação de ilhas de InP em uma rede quadrada. Além disso, mostramos que é possível criar redes bidimensionais de pontos quânticos de InAs/GaAs a partir do arranjo espacialmente ordenado das ilhas de InP/InGaP / Abstract: In this work we study the growth mechanisms during epitaxy of III-V structures based on InP. The main goal was to correlate the kinetic mechanisms during nucleation of self-assembled nanostructures with the bulk properties of the buffer layer. All samples were grown by chemical beam epitaxy (CBE) and characterized using atomic force microscopy (AFM), transmission electron microscopy (TEM), reflection high-energy electron diffraction (RHEED) and X-ray diffraction. In the first part of this work we correlate the morphological changes in homoepitaxial InP films with the RHEED pattern during growth process. We show that the morphological transition from 3D to 2D with growth parameters is related to changes in surface reconstruction, from 2x1 to 2x4. Moreover, we point out that the formation of morphological defects is due to mixed In-P dimerization, via the local activation of the diffusion bias mechanism. On the other hand, we also investigate the influence of the growth parameters (temperature, growth rate and amount of deposited material) on the nucleation and selfassembly of InP islands grown on InGaP/GaAs layers. In the second part of this work we concentrate our attention on the InGaP bulk properties, and their effect on the self-assembled InP nanostructures, mainly regarding their spatial ordering. In this way, we first investigate the dependence of InGaP bulk properties with the growth parameters. Our results show that our InGaP layers exhibit atomic ordering as well as compositional modulation. Both phenomena are correlated to the surface reconstruction exhibited by the InGaP surface during growth process. The InGaP alloy presents CuPtB atomic ordering when the RHEED pattern shows 2x1 reconstruction, in agreement with reports in literature. On the other hand, the 2x4-type reconstruction plays an important role in the compositional modulation phenomena. Actually, both compositional modulation and surface morphology of InGaP films depend on surface kinetic mechanisms, and thus on In and Ga adatom mobilities. At last we show that the compositional modulation in the InGaP alloy can be used to organize spatially the InP islands in a square lattice. Moreover, we point out that it is possible to produce bidimensional lattices of InAs/GaAs quantum dots starting from a template of laterally organized InP/InGaP nanostructures / Doutorado / Física da Matéria Condensada / Doutor em Ciências

Magister Scientiae - MSc / Cancer, the second most common cause of death after heart disease, is a complex and multifactorial disease that up to date is still under extensive research. To achieve early detection of cancer disease the discovery of specific, sensitive and reliable biomarkers is required. Telomerase is a ribonucleo-protein complex that has been identified as an important target for cancer diagnostics and cancer therapy, because 85% of more than 950 primary tumours express telomerase activity. The standard method for the detection and quantification of telomerase activity is the polymerase chain reaction (PCR)-based assay known as the telomeric repeat amplification protocol (TRAP) assay. TRAP and other methods developed for telomerase detection have limitations for example its time consuming, requires complicated machinery, expensive equipment and reagents thus there is a need for a more sensitive, reliable and high-throughput method. Electrochemical biosensors are quickly emerging as an alternative for early detection of cancer because they can be designed to detect developing cancer biomarkers and to allow improved monitoring of cancer growth and patient therapy. This research study reported for the first time the successful fabrication and implementation of highly sensitive 3-mercaptopropionic acid indium telluride quantum dots (3MPA-In2Te3 QDs) based genosensor for detection of telomerase biomarker. The colloidal poly-dispersed 3MPA-In2Te3 QDs introduced into the genosensor system were successfully synthesized by a simple, inexpensive and reproducible aqueous method. The as prepared 3MPA-In2Te3 QDs was characterized by Ultraviolet Visible (UV-VIS) spectroscopy, Fluorescence (FL) spectroscopy, X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy and High Resolution Transmission/Scanning Electron Microscopy (HR TEM/SEM). Electro-analysis of 3MPA-In2Te3 QDs was done by Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). HR-TEM studies revealed formation of small sized QDs about 6 nm in diameter while UV-VIS studies showed presence of iv absorption peaks in the ultraviolet region (100-400 nm) which confirmed the formation of these small sized QDs. The good electrochemical, optical, physical and chemical properties of the 3MPA-In2Te3 QDs allowed them to be used as a mediating platform between deoxyribonucleic acid (DNA) and gold electrode (AuE). The successful detection of telomerase was achieved by hybridization process between the probe single stranded deoxyribonucleic acid (ssDNA) drop coated on the 3MPA-In2Te3 QDs/AuE surface and its complementary ssDNA in biological buffer solution (0.10 M tris-ethylenediamine tetraacetic acid (TE) buffer solution, pH 8.00). The response of the 3MPA-In2Te3 QDs based genosensor towards different concentration of complementary ssDNA was studied by CV, square wave voltammetry (SWV) and EIS. It was observed that all three analytical techniques exhibited good linearity since their linear correlation coefficients (R2) corresponded to 0.99. However, it was observed that EIS was the best technique for the detection of telomerase compared to both CV and SWV since it showed a higher sensitivity (2.44 Ω/nM) towards detecting telomerase with a detection limit as low as 0.00014 ng/mL. Control experiments were also carried out by monitoring the hybridization process in the presence and absence of complementary ssDNA and it was determined that the QDs based genosensor was highly selective towards complementary ssDNA. In view of the attractive analytical characteristics and advantages, the ultimate goal of the developed QDs based genosensor is to apply it in real clinical samples of cancer cells or bodily fluids of cancer patients for the detection of telomerase cancer biomarker.

Room temperature photomodulated reflectance (PR), Photoluminescence (PL) and double crystal x-ray diffraction (DCXRD) measurements have been performed on a series of tensilely strained InxGa1-xAs (0.316 &le; x &le; 0.533) multiple quantum well (QW) structures, with In0.80Ga0.20As0.43P0.57 barriers. The DCXRD measurements provided accurate information on composition, strain and layer thickness, while PR was used to determine the energies of the full manifold of allowed and forbidden critical point interband QW transitions. A three-band effective mass formalism was used to model the QW transitions to derive structural information on each sample. The energies of the ground-state QW transitions, H11 and L11, were found to increase with tensile strain, becoming degenerate near 0.36% tensile strain. Room temperature PR and conventional reflectance (R) measurement have been performed on two I.R. emitting InGaAs/GaAs/A1As vertical cavity surface emitting laser (VCSEL) structures. The R measurements were modelled using a transfer matrix formalism to determine errors in the growth fluxes. A new PR lineshape model has been developed based on energy dependent Seraphin coefficients, to describe the cavity mode interaction with a confined-state QW transition. The model is demonstrated on a set of PR spectra, and used in a novel way to derive the Deltaepsilon2 spectrum of the QW layers directly. The results are compared with those taken of the QW layers directly after removing the top Bragg stack reflector. Whilst the QW layers in one sample were found to be close to nominal, the in composition of QW in the other sample was found to depart significantly from the nominal 23%, and was found to be 28%. Room temperature and ~ 80K PR measurements were performed on three InAs/GaAs self-assembled quantum dot (QD) structures: a sample with a single layer of QDs, and two with two layers. The PR revealed five equally spaced confined-state QD transitions, at both 80K and room temperature, with ~ 54 meV separation. The behaviour of the QD1 transition as a function of temperature was investigated and an anomalous increase in linewidth was observed on cooling. Annealing of one of the samples produced a strong blue shift (~ 250 meV) and narrowing of the QD transitions.

Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / The proposal of this work is separate the liquid crystal display (LCD) screen of cell phones in disuse, removing polymers which are adhered to the glass screen by using an appropriate solvent, and then perform the glass comminution to leaching the metal oxides that form part of the composition of the LCD screens of cell phones, as well as the screens of televisions, computers, digital clocks and other devices that have liquid crystal displays. With these proceedings, the polymeres, glass and metallic oxides are separated and can be recovered and reused, avoiding the consumption of non-renewable raw materials. Several tests are made under different conditions of temperature, time, ratio solute/solvent, particle size comminution and acid concentration in the leaching. The amount of indium and tin present in LCD screens, in the form of indium tin oxide (ITO) is analyzed in an apparatus for atomic absorption flame, which provides the same amount of the leaching solution. Compared with the amount of indium extracted in a solution of aqua regia 1:20, considered the condition of maximum extraction metal oxides, the quantity of indium recovered, in 1M sulfuric acid solution in 1:10 at 90ºC for 2 hours with those procedures was 98,74%. / A proposta deste trabalho é de separar, através de um desmantelamento manual, a tela de LCD de aparelhos celulares em desuso e, posteriormente, retirar os polímeros que ficam aderidos à superfície do vidro da tela com o uso de um solvente adequado, em seguida realizar a cominuição do vidro para a lixiviação dos óxidos metálicos que fazem parte da composição das telas de LCD de aparelhos de telefones celulares. Com estes procedimentos são separados polímeros, óxidos metálicos e o vidro, que podem ser recuperados e reutilizados, evitando o consumo de matérias-primas não renováveis. Foram testadas condições diferentes de temperatura, tempo, proporção soluto/solvente, tamanho de partículas cominuídas e concentração ácida nas lixiviações. A concentração de índio e de estanho presente nas soluções obtidas na lixiviação das telas de liquid crystal display (LCD) que contém óxido de estanho e índio (ITO) foi determinada pela técnica de absorção atômica (AAS). Em comparação com a quantidade de índio extraída em uma solução de água régia utilizando uma relação sólido-líquido de 1:20, considerada a condição de extração máxima dos óxidos metálicos, a quantidade de índio recuperada em solução de ácido sulfúrico 1M, na proporção 1:10, a 90ºC por 2 horas e sob agitação, foi de 98,74%.

In this thesis work, novel planar nanodiodes (PNDs) using an amorphous indium-gallium-zinc oxide (IGZO) film as the active layer have been electrically characterised for the first time. Simulation techniques and experimental methods, such as e-beam lithography (EBL) and nanoimprint lithography (NIL), have been explored for these devices. In addition, a novel approach was realized that produced self-aligned contacts for the nanostructured devices. A preliminary parameter space for experimentation of the PNDs was ascertained by simulating the devices using a technology computer aided design (TCAD) simulator. In this study Silvaco’s ATLAS default IGZO material system was adopted. These simulations showed device performance to be heavily dependent on the carrier concentration of the film, owing to the high leakage current during the off-state of device operation. Furthermore, device geometry had a significant influence on the device’s electrical response. Channel width, length and trench width were all examined. Experimental characterisation of PNDs were attained by fabricating devices using EBL. These devices are the first to exhbit diode-like DC electrical response from an IGZO-based PND. Full current rectification was obtained with a rectification ratio of 10^4 for devices with a long, narrow channel with a width of 50nm and a length of 4μm. This particular device geometry had a turn-on voltage, Von, of 2.2V and did not breakdown within the −10V bias range tested. An output drive current of 0.1μA at 10V was obtained by the single PND device. It was also demonstrated that by increasing the channel width, Von could be reduced; however, rectification also diminished. It is reasoned that the exposed IGZO surface was subject to contamination from the ambient which changed the device’s electrical response after 17 days. An ultraviolet NIL (UV-NIL) technique was developed to produce the PNDs. This fabrication method offers a suitable route towards high-volume manufacture of these nanodevices, which is critical for them to be incorporated into a low-cost RF energy harvester. A novel NIL process was established in which the contact pads were self-aligned to within ~ 200nm of the channel by patterning both metal and semiconductor layers with a single imprint. DC electrical characterisation of the imprinted PNDs produced high rectifications ratios at a lower Von. The greater number of devices tested allowed a coarse parameter space for channel width and length to determined. PNDs with a channel aspect ratio (length divided by width) of more than 20 exhibited the greatest DC rectification of 10^4. An alumina capping layer was found to eliminate hysteresis in the electrical response; however, the greater permittivity value had no noticeable effect on device performance. Finally, a large-signal RF analysis is carried out on a device which suggest no deterioration in device perfromance up to at least 1GHz.

The synthesis and characterization of a series of chiral indium complexes bearing a tridentate NNO ligand are reported. The ligand 2-[[[(dimethylamino)cyclohexyl]amino]methyl]- 4,6-bis(tert-butyl) phenol (H₂NNO) was synthesized via a previously published procedure and bound to indium by both a protonolysis and salt metathesis route. A dimethylated indium complex (NNO)InMe₂ (1) was isolated by reaction of InMe₃ with H₂NNO. A one-pot saltmetathesis route was used to produce a unique mixed-bridge dinuclear indium complex [(NNO)InCl] ₂(μ-OEt)(μ-Cl) (3) from a mixture of indium trichloride, potassium ethoxide and the monopotassiated salt of the ligand, KH(NNO). Direct reaction of KH(NNO) and indium trichloride resulted in the formation of (NNO)InCl₂ (4) which was carried forward to 3 by reaction with sodium ethoxide. The complex 3 is active for the ROP of β-butyrolactone ε-caprolactone and lactide and is the first reported indium-based catalyst for lactide or β-butyrolactone ROP. Kinetic studies of 3 for ROP of LA revealed that catalyst was well-behaved, and that the rate was first order with regard to lactide and catalyst. The enthalpy and entropy of activation for the ROP were experimentally determined. Polymer produced by ROP by 3 has narrow molecular weight distribution and a good correlation is seen between the observed moleular weight and monomer loading. A mechanism was proposed for 3 acting as a catalyst for the ROP of lactide; however further experiments are required to confirm this mechanism. Polymer samples isolated from the ROP of rac-lactide by rac-3 show isotactic enrichment. It is postulated that the chiral catalyst 3 is exerting stereocontrol via an enantiomorphic site control mechanism. / Science, Faculty of / Chemistry, Department of / Graduate

This study focuses on the development of InAs/GaInSb strained-layer superlattice structures by metal organic chemical vapour deposition (MOCVD), and deals with two aspects of the development of InAs/GaInSb SLS’s by MOCVD viz. the deposition of nano-scale (~100 Å) GaInSb layers, and the electrical characterization of unstrained InAs. The first part of this work aims to study the MOCVD growth of GaInSb layers in terms of deposition rate and indium incorporation on the nano-scale. This task is approached by first optimizing the growth of relatively thick (~2 μm) epitaxial films, and then assuming similar growth parameters during nano-scale deposition. The GaInSb layers were grown as part of GaInSb/GaSb quantum well (QW) structures. By using this approach, the GaInSb QW’s (~100 Å) could be characterized with the use of photoluminescence spectroscopy, which, when used in conjunction with transmission electron microscopy and/or X-ray diffractomery, proves useful in the analysis of such small scale deposition. It is shown that the growth rate of GaInSb on the nano-scale approaches the nominal growth rates determined from thick (~2 μm) GaInSb calibration layers. The In incorporation efficiency in nano-layers, however, was markedly lower than what was predicted by the GaInSb calibration layers. This reduction in indium incorporation could be the result of the effects of strain on In incorporation. The choice of substrate orientation for QW deposition was also studied. QW structures were grown simultaneously on both (100) and 2°off (100) GaSb(Te) substrates, and it is shown that growth on non-vicinal substrates is more conducive to the deposition of high quality QW structures. The second part of this study focuses on the electrical characterization of unstrained InAs. It is long known that conventional Hall measurements cannot be used to accurately characterize InAs epitaxial layers, as a result of parallel conduction resulting from surface and/or interface effects. This study looks at extracting the surface and bulk electrical properties of n-type InAs thin films directly from variable magnetic field Hall measurements. For p-type InAs, the situation is complicated by the relatively large electron to hole mobility ratio of InAs which tends to conceal the p-type nature of InAs thin films from Hall measurements. Here, this effect is illustrated by way of theoretical simulation of Hall data.