Hierarchical Porous Silicon: Morphological Investigations

Session

PSA.4 - Batteries & Materials for Energy Conversion

Authors

Dagmar Rings (1), Stella Gries (1), Prof. Patrick Huber (1)

Affiliations

1. Hamburg University of Technology, Institute of Materials Physics and Technology

Keywords

electron tomography, nanostructured silicon, porosity

Abstract text

Nanostructures of silicon, which is the most important material in semiconductor industry, attract attention because of their great potential applications. The particular nanoporous silicon combines interesting mechanical properties like high surface area and low density with the semiconductor properties of silicon. There are numerous potential applications, for example in photovoltaics [1], thermoelectrics [2] or anode materials of Li-ion batteries [3].

Many mechanical, electrical and optical properties of silicon depend on its structure and porosity. Therefore, it is very important to investigate the morphology and porosity of these materials. 

In this work we present morphological examinations of hierarchical porous silicon, which was synthesized using a new approach by further porosifying an already macroporous silicon membrane with smaller mesopores. The goal is to obtain an isotropic mesoporous network in the already existing macroporous silicon membrane.

After filling the porous structure with epoxy resin, we prepared the samples with FIB to obtain reasonably thin specimens of the material. Then we investigate the samples with various methods of Electron Microscopy (SEM, TEM, electron tomography).

Initial results show a high degree of porosity in the macropores walls with no decay of the macrostructure (Fig.1 and 2).

Figure 1: SEM-image of the porous silicon after the further porosifying.	Figure 2: SEM-image of the hierarchical porous silicon with a view on the macropores of the silicon membrane.

References

[1] Tian B. et al Coaxial silicon nanowires as solar cells and nanoelectronic power sources, Nature, 2, (2005), 85.

[2] Gadea G. et al., Silicon-based nanostructures for integrated thermoelectric generators, J.Phys. D: Appl. Phys. 51 (2018), 423001.   

[3] Zhu J. et al., Nanoporous silicon networks as anodes for lithium ion batteries, Phys. Chem. Chem. Phys., 15, (2013), 440.