Intercalation of hydrogen in the SiC/epitaxial graphene interface

TL;DR

This study investigates hydrogen intercalation in epitaxial graphene on SiC, revealing temperature-dependent bond formation, stability issues in ambient air, and the formation of functional groups at the interface through optical absorption measurements.

Contribution

It provides new insights into the temperature effects on hydrogen intercalation and the chemical changes at the SiC/graphene interface, using mid-infrared optical spectroscopy.

Findings

Hydrogen bonds form at 790°C, but well-developed bonds occur above 1000°C.

Intercalated hydrogen degrades within days in ambient air.

Residual hydrogen leads to vinyl and silyl group formation at the interface.

Abstract

We have measured optical absorption in mid-infrared spectral range on hydrogen intercalated epitaxial graphene grown on silicon face of SiC. We have used attenuated total reflection geometry to enhance absorption related to the surface and SiC/graphene interface. The samples of epitaxial graphene have been intercalated in the temperature range of 790 to 1250$^\circ$C and compared to the reference samples of hydrogen etched SiC. We have found that although the Si-H bonds form at as low temperatures as 790$^\circ$C, the well developed bond order has been reached only for epitaxial graphene intercalated at temperatures exceeding 1000$^\circ$C. We also show that the hydrogen intercalation degradates on a time scale of few days when samples are stored in ambient air. The optical spectroscopy shows on a formation of vinyl and silyl functional groups on the SiC/graphene interface due to the residual atomic hydrogen left from the intercalation process.