Abstract
Understanding the conducting mechanisms of dielectric materials under various conditions is of increasing importance. Here, we report the dielectric breakdown (DB) and post-breakdown mechanism of Si/SiO2, a widely used semiconductor and dielectric, in an acidic aqueous electrochemical environment. Cathodic breakdown was found to generate conduction spots on the Si/SiO2 surface. Using scanning electrochemical microscopy (SECM), the size and number of conduction spots are confirmed to increase from nanometer to micrometer scale during the application of negative voltage. The morphologies of these conduction spots reveal locally recessed inverted-pyramidal structures with exposed Si{111} sidewalls. The pits generation preceded by DB is considered to occur via cathodic dissolution of Si and exfoliation of SiO2 that are induced by local pH increases due to the hydrogen evolution reaction (HER) at the conduction spots. The HER at the conduction spots is more sluggish due to strongly hydrogen-terminated Si{111} surfaces.
Highlights
Electrical conduction of thin dielectric films has recently attracted attention because of the growing interest in their applications to resistive memory devices[4], nanopore generation[5,6], and photoelectrochemical energy conversion[7]
This study reports on the electrochemical dielectric breakdown (DB) phenomenon and post-breakdown change of a thermal SiO2 film on highly doped n-type Si (Si/SiO2) in a weakly acidic 0.1 M phosphate-buffered solution (PBS, pH 3)
The current-voltage relationship changed significantly after a five- or six-orders-of-magnitude larger current flowed whether by constant voltage stress (−4 V) (Fig. 1b) or by a current-voltage sweep to further negative potential, implying that a permanent chemical or physical change had occurred on the Si/SiO2 electrode surface. This change cannot be explained by the exfoliation of the oxide from the underlying conductive Si because the linear-sweep voltammogram acquired after the breakdown is very different from that obtained with bare Si directly exposed to Phosphate buffer solution (PBS) solution after HF chemical etching (Figure S1)
Summary
Electrical conduction of thin dielectric films has recently attracted attention because of the growing interest in their applications to resistive memory devices[4], nanopore generation[5,6], and photoelectrochemical energy conversion[7]. SECM substrate-generation tip-collection (SG-TC) images over the 200 × 200 μm[2] area were obtained in 10 mM [Ru(NH3)6]Cl3/PBS solution (pH 3) before and after DB (Fig. 2).
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