Ultra-high vacuum scanning tunnelling microscopy investigation of free radical adsorption to the Si(111)-7 × 7 surface

Nathan P. Guisinger, Shaun P. Elder, Nathan L. Yoder, Mark C Hersam

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Room-temperature ultra-high vacuum (UHV) scanning tunnelling microscopy (STM) has been employed to investigate free radical chemistry on the Si(111)-7 × 7 surface with atomic-scale spatial resolution. In particular, due to its single-site binding mechanism and extensive previous study on the Si(100)-2 × 1 surface, the nitroxyl free radical 2,2,6,6-tetramethyl-1- piperidinyloxy (TEMPO) was explored. UHV STM imaging of isolated molecules revealed that TEMPO covalently reacts with adatom dangling bonds with high affinity. By monitoring TEMPO adsorption as a function of surface coverage, TEMPO was also found to preferentially bind to centre adatom sites at the initial stages of adsorption. On the other hand, as the surface coverage increased, TEMPO molecules adsorbed to centre adatoms and corner adatoms approached a ratio of 1:1. At all surface coverage levels, TEMPO showed minimal preference for binding to either the faulted or unfaulted half of the unit cell. Consequently, upon saturation, the TEMPO adlayer exhibited long-range ordering and preserved the underlying 7 × 7 surface reconstruction. This study provides fundamental insight into free radical surface chemistry and suggests a direct pathway for forming nearly perfectly ordered organic adlayers on the Si(111)-7 × 7 surface.

Original languageEnglish
Article number044011
JournalNanotechnology
Volume18
Issue number4
DOIs
Publication statusPublished - Jan 31 2007

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Ultrahigh vacuum
Scanning tunneling microscopy
Free radicals
free radicals
ultrahigh vacuum
Free Radicals
scanning tunneling microscopy
Adatoms
Adsorption
adsorption
adatoms
Molecules
Dangling bonds
Surface reconstruction
Binding sites
chemistry
Surface chemistry
Binding Sites
affinity
Imaging techniques

ASJC Scopus subject areas

  • Engineering (miscellaneous)
  • Materials Science(all)
  • Physics and Astronomy (miscellaneous)

Cite this

Ultra-high vacuum scanning tunnelling microscopy investigation of free radical adsorption to the Si(111)-7 × 7 surface. / Guisinger, Nathan P.; Elder, Shaun P.; Yoder, Nathan L.; Hersam, Mark C.

In: Nanotechnology, Vol. 18, No. 4, 044011, 31.01.2007.

Research output: Contribution to journalArticle

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