Spatially-resolved electronic and vibronic properties of single diamondoid molecules

TL;DR

This study investigates the electronic and vibronic properties of individual tetramantane diamondoids on gold surfaces, revealing unique spatial distributions influenced by surface hydrogen terminations, with implications for molecular device design.

Contribution

First molecular-scale investigation of isolated diamondoids on metal surfaces, combining STM/STS with ab-initio calculations to understand their electronic and vibronic properties.

Findings

Unique spatial electronic and vibronic distributions with line nodes

Surface hydrogen terminations critically influence properties

Implications for designing diamondoid-based molecular devices

Abstract

Diamondoids are a unique form of carbon nanostructure best described as hydrogen-terminated diamond molecules. Their diamond-cage structures and tetrahedral sp3 hybrid bonding create new possibilities for tuning electronic band gaps, optical properties, thermal transport, and mechanical strength at the nanoscale. The recently-discovered higher diamondoids (each containing more than three diamond cells) have thus generated much excitement in regards to their potential versatility as nanoscale devices. Despite this excitement, however, very little is known about the properties of isolated diamondoids on metal surfaces, a very relevant system for molecular electronics. Here we report the first molecular scale study of individual tetramantane diamondoids on Au(111) using scanning tunneling microscopy and spectroscopy. We find that both the diamondoid electronic structure and electron-vibrational coupling exhibit unique spatial distributions characterized by pronounced line nodes across the molecular surfaces. Ab-initio pseudopotential density functional calculations reveal that the observed dominant electronic and vibronic properties of diamondoids are determined by surface hydrogen terminations, a feature having important implications for designing diamondoid-based molecular devices.