Silicon nanoclusters (Si-ncs) embedded in silicon nitride films have been studied to determine the effects that deposition and processing parameters have on their growth, luminescent properties, and electronic structure. Luminescence was observed from Si-ncs formed in silicon-rich silicon nitride films with a broad range of compositions and grown using three different types of chemical vapour deposition systems. Photoluminescence (PL) experiments revealed broad, tunable emissions with peaks ranging from the near-infrared across the full visible spectrum. The emission energy was highly dependent on the film composition and changed only slightly with annealing temperature and time, which primarily affected the emission intensity. The PL spectra from films annealed for duration of times ranging from 2 s to 2 h at 600 and 800°C indicated a fast initial formation and growth of nanoclusters in the first few seconds of annealing followed by a slow, but steady growth as annealing time was further increased. X-ray absorption near edge structure at the Si K- and L3,2-edges exhibited composition-dependent phase separation and structural re-ordering of the Si-ncs and silicon nitride host matrix under different post-deposition annealing conditions and generally supported the trends observed in the PL spectra.

Current microelectronic devices and integrated optoelectronics are strongly dominated by the silicon technology. Despite being the fundamental material in a wide range of device applications, the indirect band gap nature of silicon causes difficulties in the creation of visible luminescence from silicon based devices. Quantum confinement effects confirm the formation of silicon nanoclusters in the dielectric matrices resulting in efficient luminescence at room temperature. Among several candidates for the host matrix of silicon based materials, silicon carbonitride (SiCN) is a less studied structure exhibiting interesting features due to the combination of unique characteristics of silicon carbide and silicon nitride compounds.In this contribution, we have investigated the effect of the carbon fraction influencing the optical and structural properties of the SiCN matrix. To achieve this aim SiCN thin films have been fabricated by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD) using 30% SiH 4 in Ar, 10% N 2 in Ar, and pure CH 4 as the gas sources. In addition, for comparison, a set of silicon nitride and silicon carbide samples were fabricated as well. Following their deposition, all films were subjected to thermal annealing in a quartz tube furnace under flowing gases N 2 and N 2 + 5% H 2 for one hour at a wide range of temperatures up to 1200 °C.The compositions of the films were determined through Rutherford backscattering spectrometry (RBS) and elastic recoil detection (ERD) for samples deposited on both crystalline silicon and glassy carbon substrates. For the photoluminescence (PL) emission at room temperature, a 17 mW 325 nm HeCd laser was employed as the excitation source. Combinations of advanced techniques (Fourier transform infrared spectroscopy, Xray photoelectron spectroscopy, and high resolution transmission electron microscopy) were employed to acquire insight into the correlation between the luminescent properties and the structure of amorphous silicon carbonitride. X-ray absorption spectroscopy (XAS) has been carried out at the Si L3,2-edge on the high resolution variable line spacing plane grating monochromator (VLS PGM) 11ID-2 beamline at the Canadian Light Source synchrotron facility to obtain detailed information of silicon nanoclusters affecting the visible emission.The RBS spectra of samples deposited on glassy carbon substrates gave well separated carbon and nitrogen peaks of sample compositions varying from stoichiometric silicon nitride to the high carbon content silicon carbonitirde. PL results indicated a significant enhancement in the visible luminescence occurring at lower annealing temperatures and longer wavelengths in more carbon-rich films up to a certain ratio of CH 4 /N 2 . By continuing to increase the carbon content in the SiCN matrix both the PL emission intensity and features related to Si-C bond started to increase. X-ray absorption spectra of several annealed SiCN thin films at the Si L3,2-edge indicated that the Si-N peak decreased and ...

The luminescent and structural properties of cerium and terbium co-doped silicon oxide thin films were investigated through transmission electron microscopy, photoluminescence spectroscopy, and synchrotron-based X-ray absorption spectroscopy. While combined blue and green luminescence characteristic of Ce 3+ and Tb 3+ ions, respectively, was observed from different compositions of films, the emission intensity from samples in which Ce 2 Si 2 O 7 nanocrystallites were formed after high temperature annealing was much stronger than in films where the Ce and Tb co-dopants were incorporated in an amorphous SiO 2 host matrix. Films containing the cerium silicate phase also exhibited a very strong enhancement of Tb emission. X-ray absorption near edge structure and X-ray excited optical luminescence analysis at the Si L 3,2 -, Si K-, O K-, Ce N 4 -, and Ce M 5,4 -edges indicated this enhancement was likely the result of a direct energy transfer process between the cerium silicate and Tb levels.

Rapid thermal annealing has been used to study the changes in luminescence and structure from silicon-rich silicon nitride films for annealing times ranging from 2 seconds to 1 hour at 600 and 800°C. Silicon nanoclusters formed within the silicon nitride host matrix provided the source of the luminescence in the films through quantum confinement effects. Room temperature photoluminescence spectra exhibited a large, abrupt red-shift in emission after only 2 seconds of annealing, indicating early formation and growth of the silicon nanoclusters occurs through a fast transient diffusion mechanism. This initial shift was followed by a slower but steady growth of the nanoclusters as the annealing time was increased further. X-ray absorption near edge structure at the Si K- and L3,2-edges supported the trends observed in the photoluminescence spectra, providing evidence of silicon nanocluster growth and restructuring of the silicon nitride host matrix over the course of annealing.

Luminescent Si-based materials are of significant interest due to their potential applications in the fields of photonics and solid state lighting. The use of rare earth dopants incorporated into Si-based materials allows the attainment of specific wavelengths of emission for color tunability. Details of the RE luminescence and even the ability to obtain luminescence are strongly dependent on the composition and structure of the Si-based host material. Through the use of X-ray absorption spectroscopy details of the atomic bonding environment of the films has been obtained. X-ray excited optical luminescence, measured after excitation at the absorption edges of the constituent atoms within these materials, reveals that excitation of the rare earth ions occurs primarily at energies related to oxygen states.