Enhanced Crystallization and Sensitization of Si Nanocrystals in Al ₂ O ₃ :Er/Si:Er Multilayers

Abstract

Enhanced crystallization of Si nanocrystals (Si NCs) has been achieved in an Al2O3:Er/Si:Er multilayer structure, which is fabricated by pulsed laser deposition and subsequent rapid thermal annealing. The Er atoms introduce strains in the initial amorphous Si layers and serve as nucleation centers that enhance the crystallization of Si NCs at low annealing temperatures. The average size of Si NCs is well controlled by adjusting the Si layer thickness. Thanks to the formation of Si NCs and the favored chemical environment of Er 3+ after annealing around 600-700 ∘ C, optimized photoluminescence peaked at 1.54 𝜇m has been obtained. The present results stress the importance of controlling the formation of Si NCs to improve the performance of Er 3+ luminescence.

Raman scattering from confined acoustic phonons of silicon nanocrystals in silicon oxide matrix

“…It is not completely understood why the addition of erbium atoms allows one to obtain a spherical shape of Si-nc. It is, however very well known that the addition of erbium significantly enhances crystallization of Si-nc, since lanthanides serve as new nucleation centers [37,44]. In general, it is known that the introduction of erbium or europium to some silicate glasses significantly accelerates the nucleation process and it does not limit the size of the crystallites [45].…”

“…In general, it is known that the introduction of erbium or europium to some silicate glasses significantly accelerates the nucleation process and it does not limit the size of the crystallites [45]. In this way, the crystallization of Si-nc is observed at very low annealing temperatures, as low as 600°C [37], or even without annealing [44]. To compare, without erbium doping the crystallization of SRSO films is observed starting at around 1000°C [22], meaning that much higher energies are necessary to grow Si-nc.…”