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Submitted by Juliana Feletto Silveira Costa Lopes (juliana.feletto@gmail.com) on 2021-08-24T19:18:29Z No. of bitstreams: 1 Tese Juliana Feletto Lopes.pdf: 4071723 bytes, checksum: 894675c2f3764092565c1e964359ddc8 (MD5) Approved for entry into archive by Roberta Honorato Goria (roberta.goria@unesp.br) on 2021-08-25T15:01:37Z (GMT) No. of bitstreams: 1 lopes_jfsc_dr_soro.pdf: 4071723 bytes, checksum: 894675c2f3764092565c1e964359ddc8 (MD5) Made available in DSpace on 2021-08-25T15:01:37Z (GMT). No. of bitstreams: 1 lopes_jfsc_dr_soro.pdf: 4071723 bytes, checksum: 894675c2f3764092565c1e964359ddc8 (MD5) Previous issue date: 2021-08-02 Filmes do tipo a-C:H:Si:O, onde a indica amorfo, têm potencial para aplicações tribológicas e apresentam boa estabilidade térmica e adesão a diversos substratos. Filmes a-C:H:Si:N e a-Si:N:H são úteis como revestimentos duros e camadas isolantes em transistores de filmes finos, respectivamente. Materiais similares, dos tipos a-C:H:Si:O:N e a-C:H:Si:F:N, obtidos por Deposição à Vapor Químico Assistido por Plasma ou PECVD (do inglês Plasma Enhanced Chemical Vapor Deposition) foram estudados neste trabalho, e a influência da composição e estrutura química dos filmes nas suas propriedades ópticas e mecânicas foi delineada. Os filmes finos examinados neste estudo são complexos, contendo pelo menos cinco elementos em estequiometrias diferentes. Suas estruturas químicas também variam, dependendo dos parâmetros de deposição, como os fluxos dos gases, a potência aplicada e a posição dos substratos no reator. Filmes a-C:H:Si:O:N foram depositados a partir de hexametildissiloxano (HMDSO), oxigênio (O2) e nitrogênio (N2). A pressão do HMDSO foi mantida em 60 mTorr, assim como a pressão parcial total de O2 e N2. Filmes a-C:H:Si:F:N foram depositados a partir de tetrametilsilano (TMS), hexafluoreto de enxofre (SF6) e N2. A pressão do TMS foi mantida em 96 mTorr, e a pressão parcial total dos outros gases foi de 24 mTorr. A espessura e a rugosidade foram medidas por perfilometria. Filmes com 6 mTorr de O2 apresentaram taxas de deposição de 27 nm/min, e aqueles com 2,4 mTorr de SF6, taxas de 19 nm/min. A morfologia superficial foi examinada por Microscopia Eletrônica de Varredura (MEV) e as concentrações dos elementos foram medidas por Espectroscopia por Dispersão de Energia de Raios-X (EDS). O aumento na pressão parcial de O2 levou à diminuição da concentração atômica de carbono, enquanto com a introdução de SF6 no sistema, a concentração de carbono aumentou. Espectroscopia de Transmitância no Infravermelho (FTIR) foi empregada para identificar os grupos químicos presentes nos filmes depositados. A detecção de estruturas como Si-O-C e Si-N-Si indicaram a fragmentação de moléculas de HMDSO e a incorporação de nitrogênio no material depositado. A fragmentação de moléculas de TMS resultou na presença de grupos Si-CH3. Através da goniometria foram observados ângulos de contato de gotas de água entre 75 e 95° nos filmes a-C:H:Si:O:N, e o aumento aconteceu de acordo com a concentração de carbono. Nos filmes fluorados, houve diminuição do ângulo de contato com o aumento da pressão de SF6. As propriedades ópticas foram estimadas a partir dos espectros obtidos por Espectroscopia no Ultravioleta-Visível-Infravermelho Próximo (UV-Vis). Índices de refração relativamente baixos foram identificados, entre 1,48 e 1,61, sendo pouco maiores para os filmes com F. O gap óptico também foi maior nos filmes fluorados, com valores até 4,07 eV. As propriedades mecânicas foram obtidas por nanoindentação. Os filmes depositados com 6 mTorr de O2 apresentaram a melhor combinação de propriedades mecânicas, com elevada dureza (7 GPa) e o módulo de Young reduzido (48 GPa). Já as propriedades mecânicas diminuíram consideravelmente com a introdução de SF6 no sistema, com durezas em torno de 1 GPa, módulos de Young entre 15 e 30 GPa e rigidez entre 8 e 13 µN/nm. Thin a-C:H:Si:O films, where a indicates amorphous, have the potential for tribological applications and have good thermal stability and adhesion to various substrates. Films a-C:H:Si:N and a-Si:N:H find application as hard coatings and insulating layers in thin film transistors, respectively. Similar materials, a-C:H:Si:O:N and a-C:H:Si:F:N, obtained by Plasma Enhanced Chemical Vapor Deposition, or PECVD, were studied in this work, and the influence of the composition and chemical structure on their optical and mechanical properties outlined. The thin films examined in this study are complex, containing at least five elements in different stoichiometries. Their chemical structures also vary, with dependencies on deposition parameters, such as gas flows, applied power, and the position of substrates in the reactor. Thin a-C:H:Si:O:N films were deposited from hexamethyldisiloxane (HMDSO), oxygen (O2), and nitrogen (N2). The HMDSO pressure was maintained at 60 mTorr, as well as the total partial pressure of O2 and N2. Thin a-C:H:Si:F:N films were deposited from tetramethylsilane (TMS), sulfur hexafluoride (SF6) and N2. The TMS pressure was maintained at 96 mTorr, and the total partial pressure of the other gases was 24 mTorr. Thickness and roughness were measured by profilometry. Films with 6 mTorr of O2 showed deposition rates of 27 nm/min, and those with 2.4 mTorr of SF6, rates of 19 nm/min. The surface morphology was analyzed by Scanning Electron Microscopy (SEM) and the concentrations of the elements were obtained by Energy Dispersive X-ray Spectroscopy (EDS). The increase in partial pressure of O2 led to a decrease in the atomic concentration of carbon, while with the introduction of SF6 in the system, the concentration of carbon increased. Infrared Transmittance Spectroscopy (FTIR) was used to identify the chemical groups present. The detection of structures such as Si-O-C and Si-N-Si indicated the fragmentation of HMDSO molecules and the incorporation of nitrogen in the deposited material. The fragmentation of TMS molecules resulted in the presence of Si-CH3 groups. Through goniometry, water droplet contact angles between 75 and 95° were observed on a-C:H:Si:O:N films, and an increase occurred according to the carbon concentration. The fluorinated films showed a decrease in the contact angle with an increase in SF6 pressure. The optical properties were estimated from the spectra obtained by Ultraviolet-Visible-Near Infrared Spectroscopy (UV-Vis). Relatively low refractive indices were identified, between 1.48 and 1.61, being slightly higher for films with F. The optical gap was also greater in fluorinated films, with values up to 4.07 eV. The mechanical properties were obtained by nanoindentation. Films deposited with 6 mTorr of O2 showed the best combination of mechanical properties, with high hardness (7 GPa) and reduced Young’s modulus (48 GPa). The mechanical properties decreased considerably with the introduction of SF6 into the system, with a hardness of around 1 GPa, Young’s modulus between 15 and 30 GPa, and stiffness between 8 and 13 µN/nm.

Plasmonic devices including superlenses, hyperlenses, and far-field superlenses are specially fabricated elements which can improve the resolution of optical microscopy past inherent theoretical limits. However, their fabrication is extremely difficult as they often require ultrasmooth thin films and finely structured silver (Ag). While Ag has an ideal response for these types of lenses, its fabrication in such devices is challenging. Hence, this thesis investigates viable methods of producing ultrasmooth Ag thin films and nano-scale Ag features in order to advance research in plasmonic devices. Optimum plasmon response requires the fabrication of ultrasmooth thin silver films, which presents several challenges, such as high surface roughness and high optical loss. Thin 1 nm seed layers were fabricated in advance of Ag layers in order to improve the surface properties of Ag. We found that a 1 nm germanium (Ge) seed layer results in a 400% reduction in surface roughness down to 0.64 nm(RMS), but offers increased optical loss by about 3% over Ag alone. However, an inert atmosphere high temperature anneal of a Ge/Ag stack results in preferential grain growth, further reducing surface roughness to 0.61 nm(RMS), while also improving transmission by up to 14% over Ag alone. Similar procedures were conducted on copper (Cu) and silver oxide (AgOx) seed layers. While Cu results in very smooth Ag films of 0.61 nm(RMS) for films <10 nm thick, performance deteriorates at Ag thicknesses above 10 nm, which are preferred for the plasmonic applications identified above. Furthermore, AgOx produces very rough surfaces on substrates which are amorphous--a property which is essential for our use. However, AgOx on crystalline substrates produced smooth surfaces of 0.3 nm(RMS) and may be useful for other plasmonic applications. Interference lithography (IL) was selected as the method to create the periodic nano-scale structures. The IL equipment was modified with the addition of bandpass

In the present study we determine the optical parameters of thin metal–dielectric films using two different characterization techniques based on nonparametric and multiple oscillator models. We consider four series of thin metal–dielectric films produced under various deposition conditions with different optical properties. We compare characterization results obtained by nonparametric and multiple oscillator techniques and demonstrate that the results are consistent. The consistency of the results proves their reliability.