Structural and optical properties of size controlled Si nanocrystals in Si3N4 matrix: The nature of photoluminescence peak shiftстатья
Статья опубликована в высокорейтинговом журнале
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Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 9 ноября 2017 г.
Аннотация:Superlattices of Si3N4 and Si-rich silicon nitride thin layers with varying thickness were prepared by
plasma enhanced chemical vapor deposition. After high temperature annealing, Si nanocrystals were
formed in the former Si-rich nitride layers. The control of the Si quantum dots size via the SiNx layer
thickness was confirmed by transmission electron microscopy. The size of the nanocrystals was well
in agreement with the former thickness of the respective Si-rich silicon nitride layers. In addition
X-ray diffraction evidenced that the Si quantum dots are crystalline whereas the Si3N4 matrix
remains amorphous even after annealing at 1200 C. Despite the proven Si nanocrystals formation
with controlled sizes, the photoluminescence was 2 orders of magnitude weaker than for Si
nanocrystals in SiO2 matrix. Also, a systematic peak shift was not found. The SiNx/Si3N4
superlattices showed photoluminescence peak positions in the range of 540–660nm (2.3–1.9 eV),
thus quite similar to the bulk Si3N4 film having peak position at 577nm (2.15 eV). These rather weak
shifts and scattering around the position observed for stoichiometric Si3N4 are not in agreement with
quantum confinement theory. Therefore theoretical calculations coupled with the experimental
results of different barrier thicknesses were performed. As a result the commonly observed
photoluminescence red shift, which was previously often attributed to quantum-confinement effect
for silicon nanocrystals, was well described by the interference effect of Si3N4 surrounding matrix
luminescence.