<p> Light emitting silicon nanostructures are of significant interest for photonics due
to their potential to act as the source material for a monolithically integrated Si-based
light source. This thesis reports on the experimental characterization of such luminescent
structures formed in silicon nitride, oxynitride, and rare earth doped silicon oxide thin
films. Changes in the electronic structure of the materials have been analyzed using soft
X-ray spectroscopy by probing the constituent elements at their absorption edges. The
observed near edge structure at these edges is related to the local atomic bonding
environment of the probed atoms. Specifically, changes in the near edge structure at the
Si K and L3,2 absorption edges can be related to the coordination of silicon atoms within
the films.</p> <p> In the silicon nitrides the Si-clustering process has been observed to onset at different anneal temperatures, dependant on film composition. In films that have a small amount of excess Si higher anneal temperatures are required before a significant Si-Si
bonding signal is observed. In samples with high concentrations of excess Si this
clustering process is observed to occur at temperatures as low as 700 °C. In silicon
oxynitride samples only a small fraction of the excess Si forms into clusters within the
films. Rather, in these samples the formation of distinct silicon oxide and silicon nitride
phases is observed, with strong absorption related to the formation of the oxide phase
being observed after annealing at high temperatures (T ≥ 1000 °C). The nanoclusters were determined to be amorphous in nature, rather than nanocrystalline, through the use
of high-resolution, energy filtered, and scanning transmission electron microscopy. This
behavior was seen even for samples with high excess Si concentrations and annealed at
high temperatures. This contrasts with the behavior of silicon-rich silicon oxide thin films
were nanocrystals are clearly observed after similar treatments, indicative of the influence
of the nitride host matrix on the cluster formation process.</p> <p> Changes in the electronic structure at these edges have been correlated with changes in the bonding structure within the films, as analyzed through Fourier transform infrared spectroscopy, and with the photoluminescent behavior of the films.</p> <p> X-ray excited optical luminescence (XEOL) has been used for the study of rare earth doped silicon oxides, allowing for site specific excitation of the films in order to analyze the origin of luminescence in the films. In O-rich samples the luminescence of the films has been observed to be strongly excited at O-related absorption edges while in Si-rich samples XEOL is observed at Si-Si bonding absorption energies. The results indicate the presence of different sensitization pathways towards luminescence in the films, including the formation of oxide or silicate phases.</p> / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/17441 |
| Date | January 2009 |
| Creators | Roschuk, Tyler Richard |
| Contributors | Mascher, P., Engineering Physics |
| Source Sets | McMaster University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
Page generated in 0.0022 seconds