Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 114-122). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 114-122). Also available on the Internet.

Thesis (M. Sc.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (p. 77-81). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 116-121). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 116-121). Also available on the Internet.

Estudos de filmes de carbono tipo diamante (Diamond like-carbon – DLC), com elevado apelo acadêmico, são desenvolvidos a mais de quatro décadas. Entretanto, nos dias de hoje, o interesse industrial em suas propriedades, como alta resistência ao desgaste e ultra baixo coeficiente de atrito, impulsionou o desenvolvimento de diferentes aplicações em larga escala para diversas áreas. No entanto, essas aplicações são restritas pela baixa adesão deste material sobre ligas de aço. Uma alternativa para a solução deste problema é a deposição de uma camada intermédia contendo silício. Porém, existem poucos trabalhos metódicos da dependência de parâmetros-chave como a temperatura e tempo de processo no uso de precursores líquidos contendo silício tais como tetrametilsilano (TMS), hexametildissiloxano (HMDSO) e tetraetilortossilicato (TEOS). Neste trabalho, foram depositados diferentes intercamadas usando estes três diferentes precursores sobre substrato de aço AISI 4140, a fim de melhorar a adesão do filme DLC. Os tratamentos foram realizados em um equipamento tipo PECVD com confinamento electrostático e fonte bipolar DC pulsada. As amostras foram caracterizadas por meio de FEG-SEM, EDS, GD-OES, RAMAN e testes nanoscratch. As análises de FEG-SEM revelaram uma dependência na espessura da intercamada com a temperatura de deposição, semelhante em todas as amostras estudadas. As análises de EDS e GD-OES identificaram e quantificaram a variação de intensidades dos elementos que evidenciam a estrutura DLC/intercamada/substrato. As análises de GD-OES permitiram identificar a variação da concentração dos elementos presentes na intercamada para cada precursor utilizado. Corroborando com esses resultados, os testes de nanoesclerometria linear evidenciaram a delaminação do DLC em diferentes cargas, indicando a influência da concentração de elementos sobre a adesão do filme. A carga crítica de delaminação para filmes DLC depositados sobre intercamadas depositadas por HMDSO a 300 °C é superior a 500 mN (limite do equipamento). Finalmente, a carga crítica para o TMS a 300 °C é 313,8 mN e para TEOS a 300 °C é 306 mN, onde a concentração dos elementos oxigênio e silício presentes na intercamada prejudicaram a adesão do filme de DLC. A intercamada depositada pelo precursor HMDSO aponta para a maior quantidade de C, consequentemente o maior número de ligações C–C promove uma melhor adesão do filme de DLC à temperatura de 300 oC. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2017-03-06T17:12:00Z No. of bitstreams: 1 Dissertacao Carla Daniela Boeira.pdf: 1949458 bytes, checksum: d142b48ae2df8185c3733b95fbf49c34 (MD5) / Made available in DSpace on 2017-03-06T17:12:00Z (GMT). No. of bitstreams: 1 Dissertacao Carla Daniela Boeira.pdf: 1949458 bytes, checksum: d142b48ae2df8185c3733b95fbf49c34 (MD5) Previous issue date: 2017-03-06 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / Diamond-like carbon (DLC) films research has a high academic appeal, is being developed for more than four decades. Nowadays, the industrial needs in their properties, such as high wear resistance and superlow friction coefficient, boosted the development of different applications in large scales and many fields [1]. However such applications are restricted by the low adhesion of this material on steel. An alternative for solving this problem is the deposition of a silicon-containing interlayer [2]. However, there are few methodical studies of dependence on key parameters such as temperature and process use of silicon-containing liquid precursors such as tetramethylsilane (TMS), hexamethyldisiloxane (HMDSO) and tetraethoxysilane (TEOS). In this work, different interlayer were deposited by using these three precursors on AISI 4140 steel substrates in order improve the DLC film adhesion. The treatments were done in bipolar pulsed-DC PECVD equipment with electrostatic confinement. The samples were characterizes in details by means of FEG-SEM, EDS, GD-OES and nanoscratch tests. On the one hand, FEG-SEM images revealed an interlayers thickness dependence on deposition temperature, which is quite similar in the all samples. On the other hand, EDS and GDOES analysis identified and quantified intensities variation of iron, silicon, hydrogen, oxygen and carbon intensities that are elements responsible for the structure DLC/interlayer/substrate. The GD-OES analyzes allowed to identify the variation of concentration the elements present in the interlayer for each precursor used. Corroborating these results, linear nanoscratch tests showed delamination to DLC in different loads, indicating the influence of concentration to elements on the adhesion of the film. The critical delamination load for DLC films deposited on interlayers deposited by HMDSO at 300 °C is greater than 500 mN (equipment limit). Finally, the critical load for TMS at 300 °C is 313.8 mN and for TEOS at 300°C is 306 mN, where the concentration of the oxygen and silicon elements present in the interlayer impaired adhesion of the DLC film. The interlayer deposited by the precursor HMDSO points to the greater amount of C, consequently the greater number of C–C bonds promotes better adhesion of the DLC film to a temperature of 300 °C.

Estudos de filmes de carbono tipo diamante (Diamond like-carbon – DLC), com elevado apelo acadêmico, são desenvolvidos a mais de quatro décadas. Entretanto, nos dias de hoje, o interesse industrial em suas propriedades, como alta resistência ao desgaste e ultra baixo coeficiente de atrito, impulsionou o desenvolvimento de diferentes aplicações em larga escala para diversas áreas. No entanto, essas aplicações são restritas pela baixa adesão deste material sobre ligas de aço. Uma alternativa para a solução deste problema é a deposição de uma camada intermédia contendo silício. Porém, existem poucos trabalhos metódicos da dependência de parâmetros-chave como a temperatura e tempo de processo no uso de precursores líquidos contendo silício tais como tetrametilsilano (TMS), hexametildissiloxano (HMDSO) e tetraetilortossilicato (TEOS). Neste trabalho, foram depositados diferentes intercamadas usando estes três diferentes precursores sobre substrato de aço AISI 4140, a fim de melhorar a adesão do filme DLC. Os tratamentos foram realizados em um equipamento tipo PECVD com confinamento electrostático e fonte bipolar DC pulsada. As amostras foram caracterizadas por meio de FEG-SEM, EDS, GD-OES, RAMAN e testes nanoscratch. As análises de FEG-SEM revelaram uma dependência na espessura da intercamada com a temperatura de deposição, semelhante em todas as amostras estudadas. As análises de EDS e GD-OES identificaram e quantificaram a variação de intensidades dos elementos que evidenciam a estrutura DLC/intercamada/substrato. As análises de GD-OES permitiram identificar a variação da concentração dos elementos presentes na intercamada para cada precursor utilizado. Corroborando com esses resultados, os testes de nanoesclerometria linear evidenciaram a delaminação do DLC em diferentes cargas, indicando a influência da concentração de elementos sobre a adesão do filme. A carga crítica de delaminação para filmes DLC depositados sobre intercamadas depositadas por HMDSO a 300 °C é superior a 500 mN (limite do equipamento). Finalmente, a carga crítica para o TMS a 300 °C é 313,8 mN e para TEOS a 300 °C é 306 mN, onde a concentração dos elementos oxigênio e silício presentes na intercamada prejudicaram a adesão do filme de DLC. A intercamada depositada pelo precursor HMDSO aponta para a maior quantidade de C, consequentemente o maior número de ligações C–C promove uma melhor adesão do filme de DLC à temperatura de 300 oC. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / Diamond-like carbon (DLC) films research has a high academic appeal, is being developed for more than four decades. Nowadays, the industrial needs in their properties, such as high wear resistance and superlow friction coefficient, boosted the development of different applications in large scales and many fields [1]. However such applications are restricted by the low adhesion of this material on steel. An alternative for solving this problem is the deposition of a silicon-containing interlayer [2]. However, there are few methodical studies of dependence on key parameters such as temperature and process use of silicon-containing liquid precursors such as tetramethylsilane (TMS), hexamethyldisiloxane (HMDSO) and tetraethoxysilane (TEOS). In this work, different interlayer were deposited by using these three precursors on AISI 4140 steel substrates in order improve the DLC film adhesion. The treatments were done in bipolar pulsed-DC PECVD equipment with electrostatic confinement. The samples were characterizes in details by means of FEG-SEM, EDS, GD-OES and nanoscratch tests. On the one hand, FEG-SEM images revealed an interlayers thickness dependence on deposition temperature, which is quite similar in the all samples. On the other hand, EDS and GDOES analysis identified and quantified intensities variation of iron, silicon, hydrogen, oxygen and carbon intensities that are elements responsible for the structure DLC/interlayer/substrate. The GD-OES analyzes allowed to identify the variation of concentration the elements present in the interlayer for each precursor used. Corroborating these results, linear nanoscratch tests showed delamination to DLC in different loads, indicating the influence of concentration to elements on the adhesion of the film. The critical delamination load for DLC films deposited on interlayers deposited by HMDSO at 300 °C is greater than 500 mN (equipment limit). Finally, the critical load for TMS at 300 °C is 313.8 mN and for TEOS at 300°C is 306 mN, where the concentration of the oxygen and silicon elements present in the interlayer impaired adhesion of the DLC film. The interlayer deposited by the precursor HMDSO points to the greater amount of C, consequently the greater number of C–C bonds promotes better adhesion of the DLC film to a temperature of 300 °C.

Atomic resolution images of hot-tungsten filament chemical-vapor-deposition (CVD) grown epitaxial diamond (100) films obtained in ultrahigh vacuum (UHV) with a scanning tunneling microscope (STM) are reported. A (2x1) dimer surface reconstruction and amorphous atomic regions were observed on the hydrogen terminated (100) surface. The (2x1) unit cell was measured to be 0.51"0.01 x 0.25"0.01 nm2. The amorphous regions were identified as amorphous carbon. After CVD growth, the surface of the epitaxial films was amorphous at the atomic scale. After 2 minutes of exposure to atomic hydrogen at 30 Torr and the sample temperature at 500° C, the surface was observed to consist of amorphous regions and (2x1) dimer reconstructed regions. After 5 minutes of exposure to atomic hydrogen, the surface was observed to consist mostly of (2x1) dimer reconstructed regions. These observations support a recent model for CVD diamond growth that is based on an amorphous carbon layer that is etched or converted to diamond by atomic hydrogen. With further exposure to atomic hydrogen at 500° C, etch pits were observed in the shape of inverted pyramids with {111} oriented sides. The temperature dependence of atomic hydrogen etching of the diamond (100) surface was also investigated using UHV STM, and it was found that it was highly temperature dependent. Etching with a diamond sample temperature of 200° C produced (100) surfaces that are atomically rough with no large pits, indicating that the hydrogen etch was isotropic at 200° C. Atomic hydrogen etching of the surface with a sample temperature of 500° C produced etch-pits and vacancy islands indicating an anisotropic etch at 500° C. With a sample temperature of 1000° C during the hydrogen etch, the (100) surface was atomically smooth with no pits and few single atomic vacancies, but with vacancy rows predominantly in the direction of the dimer rows, indicating that the 1000° C etch was highly anisotropic. Raman spectroscopy was used as a temperature probe, and for determining film quality.

The effects of methane (CH4), diborone (B2H6) and nitrogen (N2) concentrations on the structure and photoelectron emission properties of chemical vapor deposition (CVD) polycrystalline diamond films were studied. The diamond films were grown on single-crystal Si substrates using the hot-tungsten filament CVD technique. Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) were used to characterize the different forms of carbon in the films, and the fraction of sp3 carbon to sp3 plus sp2 carbon at the surface of the films, respectively. Scanning electron microscopy (SEM) was used to characterize the surface morphology of the films. The photoelectron emission properties were determined by measuring the energy distributions of photoemitted electrons using ultraviolet photoelectron spectroscopy (UPS), and by measuring the photoelectric current as a function of incident photon energy.

The growth mechanism of chemical vapor deposition (CVD) grown homo-epitaxial diamond (110) and (111) films was studied using ultrahigh vacuum (UHV) scanning tunneling microscopy (STM). In addition, the field emission properties of diamond coated molybdenum microtips were studied as a function of exposure to different gases.