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Heterogeneous optoelectronic characteristics of Si micropillar arrays fabricated by metal-assisted chemical etching.

ABSTRACT: Recent progress achieved in metal-assisted chemical etching (MACE) has enabled the production of high-quality micropillar arrays for various optoelectronic applications. Si micropillars produced by MACE often show a porous Si/SiO_x shell on crystalline pillar cores introduced by local electrochemical reactions. In this paper, we report the distinct optoelectronic characteristics of the porous Si/SiO_x shell correlated to their chemical compositions. Local photoluminescent (PL) images obtained with an immersion oil objective lens in confocal microscopy show a red emission peak (? 650 nm) along the perimeter of the pillars that is threefold stronger compared to their center. On the basis of our analysis, we find an unexpected PL increase (? 540 nm) at the oil/shell interface. We suggest that both PL enhancements are mainly attributed to the porous structures, a similar behavior observed in previous MACE studies. Surface potential maps simultaneously recorded with topography reveal a significantly high surface potential on the sidewalls of MACE-synthesized pillars (+?0.5 V), which is restored to the level of planar Si control (- 0.5 V) after removing SiO_x in hydrofluoric acid. These distinct optoelectronic characteristics of the Si/SiO_x shell can be beneficial for various sensor architectures.

SUBMITTER: Qian Y

PROVIDER: S-EPMC7530667 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Heterogeneous optoelectronic characteristics of Si micropillar arrays fabricated by metal-assisted chemical etching.

Qian Yang Y Magginetti David J DJ Jeon Seokmin S Yoon Yohan Y Olsen Tony L TL Wang Maoji M Gerton Jordan M JM Yoon Heayoung P HP

Scientific reports 20201001 1

Recent progress achieved in metal-assisted chemical etching (MACE) has enabled the production of high-quality micropillar arrays for various optoelectronic applications. Si micropillars produced by MACE often show a porous Si/SiO<sub>x</sub> shell on crystalline pillar cores introduced by local electrochemical reactions. In this paper, we report the distinct optoelectronic characteristics of the porous Si/SiO<sub>x</sub> shell correlated to their chemical compositions. Local photoluminescent (PL ...[more]

PMID: 33004988

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Project description:The combination of metal-assisted chemical etching (MACE) with colloidal lithography has emerged as a simple and cost-effective approach to nanostructure silicon. It is especially efficient at synthesizing Si micro- and nanowire arrays using a catalytic metal mesh, which sinks into the silicon substrate during the etching process. The approach provides a precise control over the array geometry, without requiring expensive nanopatterning techniques. Although MACE is a high-throughput solution-based approach, achieving large-scale homogeneity can be challenging because of the instability of the metal catalyst when the experimental parameters are not set appropriately. Such instabilities can lead to metal film fracture, significantly damaging the substrate and thus compromising the nanowire array quality. Here, we report on the critical parameters that influence the stability of the metal catalyst layer for achieving large-scale homogeneous MACE: etchant composition, metal film thickness, adhesion layer thickness, nanowire diameter and pitch, metal film coverage, Si/Au/etchant interface length, and crystalline quality of the colloidal template (grain size and defects). Our results investigate the origin of the catalyst film fracture and reveal that MACE experiments should be optimized for each Si wire array geometry by keeping the etch rate below a certain threshold. We show that the Si/Au/etchant interface length also affects the etch rate and should thus be considered when optimizing the MACE experimental parameters. Finally, our results demonstrate that colloidal templates with small grain sizes (i.e., <100 μm2) can yield significant problems during the pattern transfer because of a high density of defects at the grain boundaries that negatively affects the metal film stability. As such, this work provides guidelines for the large-scale synthesis of Si micro- and nanowire arrays via MACE, relevant for both new and experienced researchers working with MACE.

Dataset Information

Heterogeneous optoelectronic characteristics of Si micropillar arrays fabricated by metal-assisted chemical etching.

Publications

Heterogeneous optoelectronic characteristics of Si micropillar arrays fabricated by metal-assisted chemical etching.

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