Berlin 2015 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 4: Thin Film Characterisation II: Structure Analysis and Composition
DS 4.6: Vortrag
Montag, 16. März 2015, 16:15–16:30, H 0111
Silicon nanocrystals in silicon nitride: the absence of quantum-confinement photoluminescence — •Anastasiya Zelenina1, Sergey Dyakov2, Daniel Hiller1, and Margit Zacharias1 — 1IMTEK University of Freiburg, Freiburg, Germany — 2Royal Institute of Technology (KTH), Kista, Sweden
Amorphous superlattices containing SiNx sublayers of different thicknesses altered with Si3N4 barriers were deposited by PECVD and further annealed at high temperatures in order to form silicon nanocrystals (Si NCs). TEM images combined with XRD spectra confirmed the formation of well separated Si NCs of controllable sizes in the range of 2 - 5 nm. The expected photoluminescence (PL) peak shift is observed at 550 - 600 nm for the films with Si NCs of 3, 4 and 5 nm in size. However, the origin of the PL peak shift induced some doubts. Firstly, the PL peaks have a very low intensity and rather broad FWHM in comparison to literature results. Secondly, the sample with Si NCs of 2 nm in size did not follow the trend and had a peak position at 580 nm. Finally, spectral position of all peaks was similar to the PL of reference Si3N4 bulk film. Our research also revealed that PL decay time is in the range of nanoseconds for all the samples, which confirm a defect-related luminescence. Thereby, we concluded that all the samples demonstrate Si3N4 defect-related PL, which originates from Si3N4 barriers. We assumed that the PL peak shift is an optical artifact. Our well-developed simulations based on the use of the method of transfer matrix confirmed the presence of optical interference in the films, which caused the PL peak shift.