Potential Monitoring During Ge Electrochemical Etching: Towards Tunable Double Porosity Layers

Porous Germanium (PGe) has emerged as a promising material for applications such as substrate engineering, sensing, and energy storage, thanks to its uniquely versatile and tunable properties. The bipolar electrochemical etching (BEE) method is widely regarded as the go-to approach for producing high-quality PGe layers. However, the lack of profound understanding of BEE process limits its use to a few well-studied morphological structures, hindering the development of more complex multi-layered structures with variable morphologies. In this work, we introduce potentiometric measures of the system as a means of monitoring the BEE process. We establish a correlation between the potential response and the reactions occurring during the BEE process, as well as their evolution over time. This approach enables elucidating the importance of the passivation, and how to shape the double-layered PGe structures. These findings bring new opportunities for controllable BEE with process monitoring and fabrication of tunable PGe multilayers for advanced applications.