Quantum chemical models for the absorption of endohedral clusters on Si(111)-(7 × 7): a subtle balance between W-Si and Si-Si bonding.

Xiao Jin,John E Mcgrady,Vaida Arcisauskaite

doi:10.1039/c9cp01841g

Abstract

The link between the intrinsic electronic properties of an endohedral metallo-silicon cluster, W@Si12, its ability to bind to a Si(111)-(7 × 7) surface and the impact on transmission properties is explored using periodic density functional theory. The W 5dz2 orbital, the LUMO of the isolated cluster, plays a critical role in all aspects, forming a covalent bond between the metal and the silicon surface, and then providing an effective transmission channel that allows current to flow from the surface to STM tip. The STM images therefore provide a very direct probe of the W-Si surface bond.

Highlights

Many of the recent advances in the field of molecular electronics have been driven by studies of molecules with appropriate linker groups absorbed on metallic surfaces.[1]
The link between the intrinsic electronic properties of an endohedral metallo-silicon cluster, W@Si12, its ability to bind to a Si(111)-(7 Â 7) surface and the impact on transmission properties is explored using periodic density functional theory
This assumption is somehow intrinsic to the concept of ‘molecular electronics’ because only in that limit can we hope to interpret current/voltage characteristics based on the properties of the isolated molecule

Summary

Introduction

Many of the recent advances in the field of molecular electronics have been driven by studies of molecules with appropriate linker groups (thiolate, for example) absorbed on metallic surfaces.[1] In such circumstances, the boundary between molecule and surface is clearly defined and the effects of surface binding can be viewed as a small perturbation to the electronic structure of the molecule. This assumption is somehow intrinsic to the concept of ‘molecular electronics’ because only in that limit can we hope to interpret current/voltage characteristics based on the properties of the isolated molecule. Beck’s experiments used laser vaporization of a silicon wafer to generate clusters in a molecular beam which is quenched in the presence of metal carbonyl

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