Abstract
Abstract A novel structure of silicon-riched nitride (SRN)/silicon-riched oxide (SRO) is proposed and prepared using RF reactive magnetron co-sputtering. High temperature annealing of SRN/SRO multilayers leads to formation of Si nanocrystals (NC) from isolating SRN and SRO layers simultaneously, which efficiently improves carrier transport ability compared to conventional SRN/Si3N4 counterpart. Micro-Raman scattering analysis reveals that SRN layer has dominating number of denser and smaller Si NCs, while SRO layer has relatively less, sparser and bigger Si NCs, as confirmed by high resolution transmission electron microscopy observation. The substitute SRO layers for Si3N4 counterparts significantly increase the amount of Si NCs as well as crystallization ratio in SRN layers; while the average Si NC size can be well controlled by the thickness of SRN layers and the content of N, and hence an obvious stronger absorption in UV region for the novel structure can be observed in absorption spectra. The I–V characteristics show that the current of hybrid SRN/SRO system increases up to 2 orders of magnitude at 1 V and even 5 orders of magnitude at 4 V compared to that of SRN/Si3N4 structure. Si NCs in SiOy layers provide a transport pathway for adjacent Si NCs in SiNx layers. The obvious advantage in carrier transportation suggests that SRN/SRO hybrid system could be a promising structure and platform to build Si nanostructured solar cells.
Highlights
Silicon(Si) nanocrystals(NCs) embedded in dielectric matrix like SiO2, Si3N4 or SiC have attracted interest vis-a-vis all-silicon tandem solar cells [1, 2] as well as silicon optoelectronics [3,4,5,6,7]
When growing SiNy layer, the power density applied to Si target is 75 W, the gas flux ratio of N2 to Ar is 4:100(SiNx), 8:100(SiNx∗) or 16:100(Si3N4); while in growing SiOx layer, the power density applied to Si and SiO2 targets are 75 W and 30 W, alternatively
The fabrication of Si NCs embedded in a novel SiNx/SiOy structure using radio frequency magnetron sputtering has been demonstrated
Summary
Silicon(Si) nanocrystals(NCs) embedded in dielectric matrix like SiO2, Si3N4 or SiC have attracted interest vis-a-vis all-silicon tandem solar cells [1, 2] as well as silicon optoelectronics [3,4,5,6,7]. As-deposited SiNx/SiOy film remains the amorphous phase characterized by the broadband peak centered at around 480 cm−1 [15]; after annealing at 1100°C, a transition from amorphous to crystalline phase occurs through random nucleation of Si NC surrounded by aSi, as indicated by the emergence of an intense peak with a frequency downshift compared to bulk Si Raman scattering spectra [16].
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