Ever since the first report by Canham, luminescence from nanocrystal Si (nc-Si) has been the subject of intense research. While there is a general agreement that quantum confinement plays an important role in determining the luminescence properties, it has proven difficult to obtain visible luminescence from oxide -passivated nc-Si.
On the other hand, other dielectrics such as $SiN_x$ are available to passivate nc-Si without introducing the oxygen-related states. So far there have been very little reports on nc-Si in $SiN_x$, and on the effect of the stoichiometry on the luminescence properties.
In this thesis, we report on tunable blue-green-red luminescence from nc-Si in $SiN_x$ films grown by ultra-high vacuum ion beam sputter deposition where only nitrogen gas was used as DC plasma source.
X-ray photoelectron spectroscopy, cross-section transmission electron microscopy, and Rutherford backscattering spectroscopy data were used for characterization of the composition, thickness, and growth mechanism.
After deposition, these films were rapid thermal annealed for 10 min at 950℃ in order to induce nucleation and growth of nc-Si, and hydrogenated for 1 hour at 650℃ in flowing $H_2$ forming gas to passivate defects. We confirmed the presence of 1-2 nm nanocrystal-Si embedded in $Si_3N_4$ matrix from HR-TEM image. By considering the enhancement by annealing, we understood that the origin of luminescence was not defects but nc-Si.
The room temperature PL spectra of $SiN_x$ films show strong luminescence in the range of 450-700 nm, visible to the naked eyes, that can be tuned by varying the excess Si content of the film. We also confirmed that this result was consistent with quantum confinement effect with decreased excess Si content.
Comparison of PL energy of $SiN_x$ with that of $SiO_x$ which has similar excess Si content shows a blue-shift of nearly 1 eV, consistent with the interface control over the nc-Si luminescence. The possibility of using nc-Si in $SiN_x$...