McMaster University DOCTOR OF PHILOSOPHY (2017) Hamilton, Ontario (Engineering Physics) TITLE: Luminescent Silicon Carbonitride Thin Films Grown using ECR PECVD: Fabrication and Characterization AUTHOR: Zahra Khatami , M.A.Sc. (Shahid Behehsti University) SUPERVISOR: Professor Peter Mascher NUMBER OF PAGES: xx, 268 / Silicon, the cornerstone semiconductor of microelectronics, has seen growing interest as a low-cost material in photonics. Nanoscience has employed various strategies to overcome its fundamentally inefficient visible light emission such as developing new silicon-based nanostructures and materials. Each of the proposed materials has its own advantages and disadvantages in attempting to reach commercialization. Silicon carbonitride (SiCxNy) is a less-studied and multi-functional material with tunable optical features. Despite reports on promising mechanical properties of SiCxNy thin films, they have not yet been well explored optically. This thesis presents the first in-depth analysis of the luminescent properties of SiCxNy thin films at a broad range of compositions and temperatures. To better understand this ternary structure, the reported data of the two fairly well studied binary structures was used as a reference. Therefore, three classes of silicon-based materials were produced and explored; SiCxNy, SiNx, and SiCx. Samples were fabricated using one of the common methods in the semiconductor industry; electron cyclotron resonance plasma enhanced chemical vapour deposition (ECR PECVD). A multitude of characterization techniques were utilized including; optical methods (ultraviolet-visible spectroscopy (UVVIS), variable angle spectroscopic ellipsometry (VASE), photoluminescence (PL)) and structural techniques (elastic recoil detection (ERD), Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HR-TEM)). In view of the exploring of emission properties of SiCxNy materials, our approach was towards the enhancement of the visible emission by adjusting the film composition and subsequent thermal treatment. First, a systematic study of the influence of carbon on the optical, compositional, and structural properties of SiCxNy was carried out. This investigation was followed by an exploration of influence of growth conditions on the visible emission and its connection with the other film properties including hydrogen concentration, microstructure, and composition. In addition, hydrogen diffusion was explored and associated with two featured annealing temperatures. The key element of this thesis is the comprehensive report on the interdependency of the visible light emission and all optical, structural, and compositional features of SiCxNy structures. Unlocking the potential of this ternary and less studied material can appeal to the silicon photonics community to implement it in anti-reflection, solar cell, and sensing applications, and in particular as a substitution of SiNx used in existing microelectronic devices. / Thesis / Doctor of Philosophy (PhD)

In the present work a new synthesis route, a hybrid between solid state reaction and proteic sol-gel method, is applied to a scintillator material based on Ca2Al2SiO7 (CAS). The luminescence mechanisms for the nanostructured scintillator is studied a mechanism that describes the luminescence process, when excited with X-rays, is proposed. The same system was also prepared via other 2 different methodologies, solid state traditional route, proteic sol-gel route, and 3 different solvents were used, for comparison in the hybrid method. In all cases the CAS phase was found as indicated by X-ray powder diffraction. During the thermal evolution of CAS precursors prepared via hybrid route assisted by coconut water, intermediate oxide phases were formed and they reacted with SiO2 to form the final CAS phase. SEM images indicated that the organic molecules present in the coconut water play an important role in the nanoparticle formation defining the average size and morphology, Samples prepared via the hybrid route showed particle with spherical shape with average size of (36 ± 15) nm. Analysis carried out via photoemission spectroscopy indicated that Si ions are the most abundant cation on surface of the particles produces via hybrid methods and solid state reaction. X-ray absorption (XAS) revealed that the Si coordination environment did not change during the synthesis. The XAS technique also indicated that the main valence for the dopants in CAS structure and the emission spectra obtained via pholuminescence and X-ray excited optical luminescence (XEOL) confirmed that the main emissions are related to the dopants on the CAS matrix. Extended X-ray absorption fine structure revealed the location of the dopants in the CAS matrix, and the most probable defect generated for the dopant presence. XEOL excitation spectra showed different behaviors for the luminescence around K edge of the matrix elements. The XEOL decay time indicated that fast scintillators were produced when CAS were doped with Ce3+ with characteristic constants lower than 40 ns. The results time dependent XEOL emission also showed that the luminescence decay curves are influenced by the presence of electrons and holes shallow traps in the CAS electronic structure. / No presente trabalho uma nova rota de síntese, híbrida entre as sínteses de estado sólido e sol-gel proteico, é aplicada a um material cintilador baseado na matriz cristalina Ca2Al2SiO7 (CAS). Adicionalmente, o mecanismo de luminescência destes cintiladores nanoestruturados é estudado e um modelo é proposto. Para efeito de comparação com a rota de síntese híbrida, amostras foram também preparadas por sol-gel proteico e síntese de estado sólido, e com a variação do solvente na síntese híbrida. Os resultados de difração de raios X mostraram que as amostras apresentaram a fase cristalina de Ca2Al2SiO7 após calcinação acima de 1300°C. Durante a evolução térmica dos precursores preparados pelo método híbrido assistido por água de coco, fases cristalinas intermediárias são formadas e estas reagem com o SiO2, até a formação do CAS. As imagens obtidas por microscopia eletrônica de varredura indicaram que as moléculas orgânicas presentes na água de coco são decisivas no controle do tamanho e morfologia das nanopartículas obtidas pelo método híbrido, e as partículas apresentam formato esférico e tamanho médios de (36 ± 15) nm. A espectroscopia de fotoemissão revelou que o Si é o elemento mais abundante na superfície das amostras produzidas pelos métodos híbridos e síntese de estado sólido. Enquanto a absorção de raios X (XAS) mostrou que a coordenação do Si não muda durante a síntese. A XAS também indicou as valências mais abundantes dos íons dopantes do CAS e os espectros de emissão fotoluminescente e de luminescência óptica estimulada por raios X (XEOL) confirmaram que estes são os canais luminescentes dos materiais. Com a análise da estrutura fina de absorção de raios X foi possível localizar os sítios ocupados pelos dopantes no CAS, assim como estimar o tipo de defeito mais provável, gerado pela presença destes íons. Os espectros de excitação XEOL mostraram comportamentos diferentes para a luminescência na região das bordas K de absorção dos elementos da matriz. As medidas de tempo de decaimento da luminescência indicaram a obtenção de cintiladores muito rápidos, com constantes características menores que 40 ns em todas as amostras que contém Ce3+ e que o processo de decaimento também está associado à presença de armadilhas de portadores de cargas na estrutura eletrônica do material.