The unique properties of diamond make it an excellent material for electronic and optical applications. It is particularly attractive for ultraviolet radiation dosimetry due to its intrinsic properties, which include biological tissue equivalence and visible blindness. Importantly, the advent of synthetic diamond, especially Chemical Vapour Deposition (CVD) diamond, has made it more economically viable for such applications. A thorough understanding of the electronic properties of diamond is needed before these applications can be fully explored. Consequently, this thesis investigates charge carrier trapping states in CVD polycrystalline diamond for the optimization of ultraviolet radiation dosimetry. / The technique of Thermally Stimulated Conductivity (TSC) is used to probe electrically active defects and is also applied for dosimetric read-out. A range of as-grown CVD polycrystalline diamond films are studied to determine attributes that favour dosimetric-related TSC. In doing so, we establish that dosimetric TSC in these films originate from defects at the grain boundaries with a correlation to high crystalline quality. / With this finding in hand, we then investigate the possibility of optimising diamond for dosimetry by controllably introducing extrinsic dosimetric defects using ion implantation. However, it is shown that these defects are not suitable for dosimetry and have a detrimental effect on the indigenous TSC signal. This study verifies the importance of crystalline quality on the indigenous dosimetric properties of CVD polycrystalline diamond. / The possibility of doping CVD diamond during growth is also investigated as a means for intentionally introducing extrinsic dosimetric defects. Sulphur is selected as the dopant based on the theoretical energy levels formed by this defect, and because the prospect of S doping in diamond remains an actively debated issue in the literature. We report for the first time defect levels extracted from TSC analysis of S-doped CVD diamond and find consistency with theoretical predications. In addition, the dominant TSC trap level in S-doped diamond shows promise for radiation dosimetry with certain properties exceeding many current radiation dosimeters. / The experimental results in this thesis lead to a deeper understanding of defect and trapping mechanisms in CVD polycrystalline diamond and establish attributes that favour TSC and related dosimetric properties in such films. This knowledge is fundamental to the realisation of diamond for ultraviolet dosimetry.

Orientador: Vitor Baranauskas / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-10T13:04:37Z (GMT). No. of bitstreams: 1 Pinto_MarcioAugustoSampaio_M.pdf: 3334021 bytes, checksum: e3031df53e18ad072ffc8cbe1486889f (MD5) Previous issue date: 2007 / Resumo: Apresentamos neste trabalho o desenvolvimento de filmes de diamante crescidos com adição de enxofre. Foram crescidos por deposição química a partir da fase vapor (diamante CVD) utilizando reatores do tipo filamento quente. Para a obtenção de diamante com condução do tipo-n, diluímos diferentes concentrações de dissulfeto de carbono (CS2) em etanol, cujo vapor foi arrastado para o reator pelo hidrogênio. Isto foi feito, pois o enxofre pode agir como doador em diamante. A espectroscopia Raman mostrou a boa qualidade dos filmes de diamante crescidos mesmo com o aumento da concentração de CS2. Ocorreu o deslocamento do pico do diamante indicando que houve um aumento médio nos comprimentos das ligações detectadas nas amostras, possivelmente devido à expansão da rede do diamante pela incorporação do enxofre. As imagens revelam uma perda da cristalinidade das amostras intermediárias e o ótimo facetamento das amostras iniciais e finais (baixa e alta concentração de CS2). Medidas elétricas pela sonda de quatro pontas revelaram que quanto mais o CS2 era adicionado, mais a resistividade dos filmes produzidos diminuía e que depois voltou a subir nas últimas amostras. Ao tratar as amostras com ácidos nítrico e sulfúrico para fazer medidas por efeito Hall, elas se tornaram isolantes. Esse fato revela que o banho removeu o material condutor e que pode ser devido à dopagem com enxofre nas áreas superficiais e intergranulares dos filmes. Medidas por efeito Hall de amostras que foram crescidas ao mesmo tempo das amostras tratadas pelo banho, mas sem passar por ele, apresentaram uma condução do tipo-p devido aos buracos, da mesma forma que as amostras relatadas em artigos na literatura em que não houve contaminação com boro, seja ela involuntária ou voluntária. Apresentaram também alta densidade de portadores e uma mobilidade razoável. A incorporação do enxofre no filme de diamante foi confirmada por medidas de XRF e de PIXE. O aumento do enxofre incorporado no filme não foi proporcional às crescentes concentrações de CS2. Isto sugere que nem todo átomo de enxofre é eletricamente ativo, isto é, nem todo enxofre age como um dopante nos filmes de diamante. Estudos recentes revelam que a presença do boro nas dopagens com enxofre têm sido decisiva na obtenção de diamante do tipo-n / Abstract: We present in this work the development of grown diamond films with sulphur addition. They had been grown by chemical deposition from the vapor phase (diamond CVD) using reactors of the type hot filament. For the diamond attainment with conduction of the n-type, we diluted different concentrations of carbon disulfide (CS2) in ethyl alcohol, whose vapor was dragged into reactor by hydrogen. This was done, due to the fact that sulphur can act as a donor in diamond. The Raman spectroscopy showed exactly the good quality of the grown diamond films with the increase of the CS2 concentration. The displacement of the peak of the diamond occurred indicating that it had an average increase in the lengths of the linkings detected in the samples, possibly due to the expansion of the lattice of the diamond for the incorporation of sulphur. The images presented to a loss of the crystallinity of the intermediate samples and the excellent good crystalline facets of the initial and final samples (low and high concentration of CS2). The electric measures in four-point probe methods showed that the higher the concentration of CS2 the lower the resistivity of the produced films was, and afterwards, it went up again in the last samples. When treating the samples with nitric and sulphuric acids to make the measures for Hall effect, they had become insulators. This fact discloses that the bath removed the conducting material and that can be due to doping with sulphur in the surface and intergrain areas of the films. The Hall effect measures of the samples that had been grown at the same time of the samples treated for the bath, but without being through it, presented a conduction of the p-type due to the holes, in the same way that the samples described in articles in literature where they did not have contamination with boron, either involuntary or voluntary. They had also presented high density of carriers and a reasonable mobility. The incorporation of sulphur in the diamond film was confirmed by measures of XRF and PIXE. The increase of sulphur incorporated in the film was not proportional to the increasing concentrations of CS2. This suggests that nor all sulphur atom is electrically active, that is, not every sulphur acts as a dopant in the diamond films. Recent studies have disclosed that the presence of boron in the doping with sulphur has been decisive in the diamond attainment of the n-type / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

Orientador: Vitor Baranauskas / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-05T18:10:58Z (GMT). No. of bitstreams: 1 Correa_WashingtonLuizAlves_D.pdf: 3351242 bytes, checksum: 8f30a26c68d4c1e73a72d065eaedb4f9 (MD5) Previous issue date: 2004 / Resumo: Estudamos processos de dopagem do diamante crescido por deposição química a partir da fase vapor (diamante CVD) com a introdução de impurezas dopantes durante o crescimento do diamante em reatores do tipo filamento-quente. Focalizamos nossa pesquisa na dopagem do diamante com boro, ou nitrogênio, ou enxofre, visando obter diamantes com propriedades semicondutoras com condutividade eletrônica (tipo n) ou condutividade por lacunas (tipo p). Foram utilizadas contaminações intencionais utilizando: trimetil borano (B(CH3)3), ou amônia (NH3), ou dissulfeto de carbono (CS2), misturados com metano e diluídos em hidrogênio. As amostras foram caracterizadas por microscopia eletrônica de varredura (SEM), espectroscopia Raman, espectroscopia de foto-elétrons excitados por raios X (XPS), espectroscopia de emissão de raios X excitado por feixe de prótons (PIXE) e efeito Hall. As dopagens do diamante do tipo p e do tipo n foram obtidas com contaminações de boro e enxofre, respectivamente. O diamante dopado com nitrogênio não apresentou propriedades semicondutoras / Abstract: We studied the diamond doping processes with introduction of doping impurities during the diamond growth in the chemical vapor deposition (CVD) technique, using a hot-filament reactor. Our research focused the use of boron, nitrogen or sulphur atoms in order to obtain diamond films with semiconductor properties of electronic (n-type) or hole (p-type) current transport mechanisms. Trimethyl-borane (B(CH3)3), or ammonia, or carbon disulphide (CS2), mixed with methane and hydrogen were used in the feed gas mixture. The diamond samples were characterized by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Proton-induced X-ray emission (PIXE) and Hall effect. p-type and n-type diamonds have been obtained with boron and sulphur doping, respectively. However, the nitrogen doped samples do not presented semiconductor properties / Doutorado / Engenharia de Eletronica e Comunicações / Doutor em Engenharia Elétrica