# Determination of fracture toughness of thin-film amorphous silicon using spiral crack structures

## TL;DR

This study introduces a novel method to determine the fracture toughness of thin-film amorphous silicon by analyzing spiral crack structures formed under tensile stress, combining experimental, analytical, and numerical approaches.

## Contribution

It presents the first quantitative evaluation of fracture toughness in amorphous silicon using spiral crack analysis and FEM-based geometry correction.

## Key findings

- Fracture toughness of amorphous silicon is significantly higher than crystalline silicon.
- Residual tensile stress induces spiral cracks in silicon layers.
- Finite element method effectively models crack geometry for toughness calculation.

## Abstract

We prepared thin layers of amorphous silicon by deposition of a liquid-phase polysilane precurser on glass substrate. Raman scattering provides evidence for residual tensile stress in the silicon, which is evaluated quantitatively. Under treatment with hydrofluoric acid, this stress leads to spiral cracks in the silicon. We explain the process of crack formation and examine this phenomenon both analytically and numerically, the latter with the finite element method (FEM). The FEM yields the geometry correction factor for such spiral cracks in terms of the Griffith criterion. This allows for the first time the determination of fracture toughness of amorphous silicon, which is greatly enhanced in comparison with crystalline silicon.