Dynamics of NF3 in a condensed film on Au(1 1 1) as studied by electron-stimulated desorption

Izabela Irena Rzeznicka, Junseok Lee, John T. Yates

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

We report a low-temperature dynamics study of condensed layers of NF3 on Au(1 1 1) by time-of-flight electron-stimulated desorption ion angular distribution (TOF-ESDIAD), temperature-programmed desorption (TPD) and low-temperature scanning tunneling microscopy (LT-STM). Upon adsorption at 30 K, molecular NF3 adsorption occurs first at the step edges and at minor terrace defect sites with the formation of 2D islands. Within the islands, NF3 is adsorbed in an upright conformation via the nitrogen lone pair electrons projecting fluorine atoms away from the surface as judged by the presence of only a sharp F+ central beam in the ESDIAD pattern. At higher coverages, 3D islands start to populate the surface. Electron bombardment of a thick NF3 (∼6 ML) layer adsorbed on the Au(1 1 1) surface leads to emission of F+, N+, NF+, NF2 + and NF3 + ions as observed in the TOF-ESD distribution. Upon heating to ∼37 K, a sudden decrease of the NF2 + and NF3 + ion yield, which is not related to thermal desorption, is observed which reflects the surface migration of NF3 molecules, leading to local thinning of the film. The thinning process occurs at the temperature of onset of molecular rotations and self-diffusion in the bulk NF3 crystal. In this process, some NF3 molecules move closer to the surface which results in higher efficiency for ion neutralization by the underlying metal surface. In the TPD spectra, the monolayer desorption is observed to begin at ∼65 K, exhibiting zero-order kinetics with an activation energy of 21 kJ/mol.

Original languageEnglish
Pages (from-to)4492-4500
Number of pages9
JournalSurface Science
Volume600
Issue number19
DOIs
Publication statusPublished - 2006 Oct 1
Externally publishedYes

Fingerprint

Desorption
desorption
Electrons
Ions
electrons
Temperature programmed desorption
ions
molecular rotation
adsorption
electron bombardment
Adsorption
Thermal desorption
Molecules
Fluorine
Angular distribution
metal surfaces
Scanning tunneling microscopy
temperature
fluorine
scanning tunneling microscopy

Keywords

  • Au(1 1 1)
  • Condensed molecular films
  • Low-temperature scanning tunneling microscope
  • Molecular rotation
  • Nitrogen trifluoride
  • Temperature-programmed desorption
  • Time-of-flight electron-stimulated desorption ion angular distribution

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Condensed Matter Physics
  • Surfaces and Interfaces

Cite this

Dynamics of NF3 in a condensed film on Au(1 1 1) as studied by electron-stimulated desorption. / Rzeznicka, Izabela Irena; Lee, Junseok; Yates, John T.

In: Surface Science, Vol. 600, No. 19, 01.10.2006, p. 4492-4500.

Research output: Contribution to journalArticle

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N2 - We report a low-temperature dynamics study of condensed layers of NF3 on Au(1 1 1) by time-of-flight electron-stimulated desorption ion angular distribution (TOF-ESDIAD), temperature-programmed desorption (TPD) and low-temperature scanning tunneling microscopy (LT-STM). Upon adsorption at 30 K, molecular NF3 adsorption occurs first at the step edges and at minor terrace defect sites with the formation of 2D islands. Within the islands, NF3 is adsorbed in an upright conformation via the nitrogen lone pair electrons projecting fluorine atoms away from the surface as judged by the presence of only a sharp F+ central beam in the ESDIAD pattern. At higher coverages, 3D islands start to populate the surface. Electron bombardment of a thick NF3 (∼6 ML) layer adsorbed on the Au(1 1 1) surface leads to emission of F+, N+, NF+, NF2 + and NF3 + ions as observed in the TOF-ESD distribution. Upon heating to ∼37 K, a sudden decrease of the NF2 + and NF3 + ion yield, which is not related to thermal desorption, is observed which reflects the surface migration of NF3 molecules, leading to local thinning of the film. The thinning process occurs at the temperature of onset of molecular rotations and self-diffusion in the bulk NF3 crystal. In this process, some NF3 molecules move closer to the surface which results in higher efficiency for ion neutralization by the underlying metal surface. In the TPD spectra, the monolayer desorption is observed to begin at ∼65 K, exhibiting zero-order kinetics with an activation energy of 21 kJ/mol.

AB - We report a low-temperature dynamics study of condensed layers of NF3 on Au(1 1 1) by time-of-flight electron-stimulated desorption ion angular distribution (TOF-ESDIAD), temperature-programmed desorption (TPD) and low-temperature scanning tunneling microscopy (LT-STM). Upon adsorption at 30 K, molecular NF3 adsorption occurs first at the step edges and at minor terrace defect sites with the formation of 2D islands. Within the islands, NF3 is adsorbed in an upright conformation via the nitrogen lone pair electrons projecting fluorine atoms away from the surface as judged by the presence of only a sharp F+ central beam in the ESDIAD pattern. At higher coverages, 3D islands start to populate the surface. Electron bombardment of a thick NF3 (∼6 ML) layer adsorbed on the Au(1 1 1) surface leads to emission of F+, N+, NF+, NF2 + and NF3 + ions as observed in the TOF-ESD distribution. Upon heating to ∼37 K, a sudden decrease of the NF2 + and NF3 + ion yield, which is not related to thermal desorption, is observed which reflects the surface migration of NF3 molecules, leading to local thinning of the film. The thinning process occurs at the temperature of onset of molecular rotations and self-diffusion in the bulk NF3 crystal. In this process, some NF3 molecules move closer to the surface which results in higher efficiency for ion neutralization by the underlying metal surface. In the TPD spectra, the monolayer desorption is observed to begin at ∼65 K, exhibiting zero-order kinetics with an activation energy of 21 kJ/mol.

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