The rate of oxide formation during growth of pores structures on silicon was investigated by an advanced in-situ I-V measurements. The measurements were designed to get two I-V curves in a short time (300 sec.) taking into account the gap (in mA/cm2) for each corresponding voltages. [i],[ii] The in-situ I-V measurements were made at different pore depth/time, while etching takes place based on p-type Si. This was related to the expected diffusion limitation of oxide forming (H2O) molecules reaching at the electrolyte-pore tip and the anodizing current while etching takes place. The study showed that the rate of oxidation (I-V gap) during the formation of macropores, with straight walls and relatively deep structures, decreases as the pores grow down with time. This oxidation rate increases by increasing the anodizing current. However, pores with spongy like structure (irregular structures) with multi-channelled tends to show an increasing of the current gap in time. On the other hand, the rate of oxidation (or I-V gap) for nanopores and electropolishing tends to show a decreasing and constant I-V gap in time was shown, respectively. The method can be developed further and has the potential to be applied in other electrochemically etched porous semiconductor materials.
[i]. A. Benor, J. Nanomaterials, 2017, 1-7 (2017).
[ii]. A. Benor, Materials Science and Engineering B., In Press (2017).