# Electro-Oxidation of p-Silicon in Fluoride-Containing Electrolyte: A Physical Model for the Regime of Negative Differential Resistance

## TL;DR

This paper develops a physical model for the negative differential resistance observed during the electro-oxidation of p-silicon in fluoride electrolytes, aligning well with experimental data on current-voltage behavior and oxide layer properties.

## Contribution

It introduces a novel physical model accounting for partial and full oxidation states of silicon and their influence on etch rate, explaining the negative differential resistance phenomenon.

## Key findings

- Model reproduces negative slope in current-voltage characteristics
- Simulations match measured oxide thickness and dissolution valence
- Impedance spectra are consistent with experimental data

## Abstract

When Si is anodically oxidized in a fluoride containing electrolyte, an oxide layer is grown. Simultaneously, the layer is etched by the fluoride containing electrolyte. The resulting stationary state exhibits a negative slope of the current-voltage characteristics in a certain range of applied voltage. We propose a physical model that reproduces this negative slope. In particular, our model assumes that the oxide layer consists of both partially and fully oxidized Si and that the etch rate depends on the effective degree of oxidation. Finally, we show that our simulations are in good agreement with measurements of the current-voltage characteristics, the oxide layer thickness, the dissolution valence, and the impedance spectra of the electrochemical system.