Phononic and electronic features of diamond nanowires

TL;DR

This study uses density functional theory to analyze vibrational, Raman, and electronic properties of hydrogen-passivated diamond nanowires, revealing surface effects and electronic behavior contrary to quantum confinement expectations.

Contribution

It provides new insights into how surface termination influences vibrational and electronic properties of diamond nanowires, challenging previous assumptions about quantum confinement effects.

Findings

Surface effects cause splitting and redshift of optical modes.

Hydrogen surface termination reduces the electronic bandgap.

Electronic conduction bands are mainly contributed by surface hydrogen atoms.

Abstract

By using density functional theory, we have studied vibrational features, Raman activities, and electronic properties of ultrathin hydrogen-passivated diamond nanowires (H-DNWs). Confinement imposes the softening of transverse acoustic modes and the hardening of the low-optical modes. Higher frequencies optical modes are more influenced by the surface termination effect. Surface effect splits transverse (TO) and longitudinal (LO) optical modes with a redshift from the bulk diamond. Electronic inspection shows that the surface terminated hydrogen atoms have the main contribution to the conduction bands of H-DNWs. This causes, contrary to our expectations from the quantum confinement effect, the electronic bandgap of H-DNWs becomes smaller than bulk diamond.