Self-Ordered Voids Formation in SiO₂ Matrix by Ge Outdiffusion

Abstract

The annealing behavior of very thin SiO 2 /Ge multilayers deposited on Si substrate by e-gun deposition in high vacuum was explored. It is shown that, after annealing at moderate temperatures (800 ∘ C) in inert atmosphere, Ge is completely outdiffused from the SiO 2 matrix leaving small (about 3 nm) spherical voids embedded in the SiO 2 matrix. These voids are very well correlated and formed at distances governed by the preexisting multilayer structure (in vertical direction) and self-organization (in horizontal direction). The formed films produce intensive photoluminescence (PL) with a peak at 500 nm. The explored dynamics of the PL decay show the existence of a very rapid process similar to the one found at Ge/SiO 2 defected interface layers.

Synthesis and optimization of photothermal properties of NIR emitting LiGa5O8: Cr3+ and gold nanorods as hybrid materials for theranostic applications

“…The black lines are used as control (stock solution). In all four spectra, a signal-centered peak is present at ∼900 nm, which is associated to the coating with SiO 2 [ 21 ].

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Stress Evolution during Ge Nanoparticles Growth in a SiO2 Matrix

“…The effective bilayer number N eff for which the interface roughness is correlated can be estimated from the fwhm of the Bragg sheets Δq z BS along the q z direction, from the relationship 29,30…”

“…Annealing at 750 °C caused Ge out-diffusion and void formation at the positions previously occupied by the Ge clusters. 30 This is reflected by the shift of the Bragg sheets in the opposite direction due to a decrease of the bilayer thickness by 1 nm. Indeed, as shown in Figure 8, the existence of multiple-order Bragg sheets confirms that Ge remained mostly in the SiO 2 /Ge layers, and the multilayer structure was not destroyed by annealing at different temperatures up to 650 °C.…”

“…The effective bilayer number N eff for which the interface roughness is correlated can be estimated from the fwhm of the Bragg sheets Δ q z BS along the q z direction, from the relationship , Here m is the order of the Bragg sheet. For small in-plane momentum transfer, q y ≅ 0 and Δ q z BS = 0.941 ± 0.062 nm –1 , which corresponds to N eff = 1.…”

“…Annealing at 550 °C and up to 650 °C induced growth of the QDs, as shown in Figure , and this is reflected in the gradual shift of all three Bragg sheets and in the increase of the bilayer thickness by 0.8 nm, calculated from the position of the Bragg sheet. Annealing at 750 °C caused Ge out-diffusion and void formation at the positions previously occupied by the Ge clusters . This is reflected by the shift of the Bragg sheets in the opposite direction due to a decrease of the bilayer thickness by 1 nm.…”