Study of surface morphology of electrochemically etched n‐Si (111) electrodes at different anodic potentials

Abstract

Changes of n-Si (111) silicon surface morphology after anodisation at different voltage conditions in dilute NH 4 F solutions were studied by AFM technique. The electrochemical etching was done with respect to current-voltage (I-V) characteristics. The Si surface was investigated at increasing and constant voltage conditions. The porous silicon was formed at potentials slightly anodic from the rest potential (from -0.6 V to 0.02 V). On the other hand silicon oxide formation and electropolishing occurs at higher anodic potentials. The sustained current oscillations take place in the Si electrode, at 6 V potential in dilute NH 4 F solution. The nature of oscillations was attributed to cyclic silicon oxide formation and its dissolution. The surface undergoes from smooth (before oscillation peak) to rough (little before top of the peak) during oscillation peak, and finally transforms to smooth at the bottom of the peak. It was confirmed by the roughness parameter.

Fabrication of deep single trenches from N-type macroporous silicon

“…In this case, the Si-SiF bonds can be broken by reacting with H 2 O, resulting in Si-O-Si bonds, which are not stable in HF. The resulting measured current is then oscillating for a fixed applied voltage [15]. In aqueous electrolytes, derived from the H 2 O-HF system, the limit between these two regions is materialized by a bPorous Silicon Limit (PSL)-peakQ clearly observed in Fig.…”

Structure formation at the nanometric scale during current oscillations at the Si/electrolyte contact

“…Accordingly, during one cycle such a Si-layer is removed by oxidation and subsequently oxide etching [16]. The thickness of the removed Si-layer depends on potential, illumination and etching rate.…”

Model for Current Oscillations at the Si/Electrolyte Contact:Extension to Spatial Resolution

“…Simultaneously, the current-less etching process reduces the oxide thickness until a minimum value is reached at which electrical contact between electrolyte and silicon is made locally and the cycle starts again. During each cycle, a silicon layer of constant thickness d is consumed by oxidation and dissolution (15). The oxide thickness oscillation, however, proceeds not uniformly at the whole electrode surface.…”