A Model for Current Oscillations at the SI-HF-System

Introduction

The JU-Characteristics

Fig. 1

The current voltage characteristics in the anodic region of the Si-HF-Contact consists of several distinct regimes:

1. Allmost no current flow since the hydrogen overpotential is not reached and anodic currents are not present
2. Butler-Volmer regime; current growth exponetially with applied potential
3. porous silicon regime (PSL): nanoporous silicon layer is formed
4. electropolishing regime; anodic oxide is formed which is purely chemically dissoled; this leads to a smoothing of surface roughness
5. oscillation regime; applying hight enought constant anodic potentials self-organized and self stabilized current oscillations occur. For high enough constant anodic currents voltage oscillations occure in the same regime of the iv-curve.

In this paper we will envestigate this oscillation regime

Examples for Current and Voltage Oscillations

Current Oscillations	Voltage Oscillations
	Fig. 2

Extremely stable current or voltage oscillations are fond in the high anodic bisa regime. The voltage oscillations are allways much more complicating the the current oscillations and show extremely steep slopes. Depending on the choise of teh chemical parameters and other etching conditions stable oscillations or damped oscillations are found.