Designing substrates for silicene and germanene: First-principles calculations

TL;DR

This paper presents a first-principles approach to identify suitable substrates for silicene and germanene, emphasizing the importance of band alignment and strong binding to preserve their Dirac states for nanoelectronic applications.

Contribution

It introduces a guideline for substrate selection based on band alignment and binding energy, demonstrated through first-principles calculations on Al2O3 substrates.

Findings

Supported silicene and germanene retain their structure on Al2O3(0001).

Gapped Dirac cones form at the K point due to substrate interaction.

Gaps of 0.4 eV and 0.3 eV suggest potential in nanoelectronics.

Abstract

We propose a guideline for exploring substrates that stabilize the monolayer honeycomb structure of silicene and germanene while simultaneously preserve the Dirac states: in addition to have a strong binding energy to the monolayer, a suitable substrate should be a large-gap semiconductor with a proper workfunction such that the Dirac point lies in the gap and far from the substrate states when their bands align. We illustrate our idea by performing first-principles calculations for silicene and germanene on the Al-terminated (0001) surface of Al2O3 . The overlaid monolayers on Al-terminated Al2O3(0001) retain the main structural profile of the low-buckled honeycomb structure via a binding energy comparable to the one between silicene and Ag(111). Unfolded band structure derived from the k-projection method reveals that gapped Dirac cone is formed at the K point due to the structural distortion and the interaction with the substrate. The gaps of 0.4 eV and 0.3 eV respectively for the supported silicene and germanene suggest that they may have potential applications in nanoelectronics.