Attenuation Length of Electrons in Self-Assembled Monolayers of n-Alkanethiols on Gold

Abstract

The interaction of both photoelectrons and X-rays with self-assembled monolayers of n-alkanethiols on gold has been measured using synchrotron radiation as the photon source in the energy range 140−1100 eV. The attenuation length of photoelectrons (λ) was found to vary from a minimum of ∼5 Å at an electron kinetic energy (E) of 100 eV up to ∼23 Å at a kinetic energy of 1000 eV and can be described by the expression λ = 0.3E 0.64 in the range 300−1000 eV. Exposure of the self-assembled monolayer to X-rays leads to fission of the C−S bond with a cross section of the order of 10-17 cm2 which diplays no apparent dependence on the incident photon energy.

Thymine/adenine diblock-oligonucleotide monolayers and hybrid brushes on gold: a spectroscopic study

“…This seeming disagreement can be explained by the stronger attenuation of the photoelectron signal from the d(A) block serving as the molecular anchor and located, partly or almost completely, underneath the d(T) block. Note that the attenuation is especially strong at the kinetic energy of the N 1s photoelectrons (~180 eV; an attenuation length of 0.84 nm [33]), which explains why this effect was less pronounced in previous work relying on laboratory XPS systems [13,24,25] which have much higher excitation energy and, subsequently, higher photoelectron kinetic energies. Note also that the respective attenuation factor (~2.5) does not change significantly with the increasing length of the d(A) block, which contradicts the idea of the L-shape adsorption model and suggests that the exact adsorption geometry of the A n T 15 molecules depends on the molecular composition.…”

“…the same peak parameters were used for identical spectral regions. The film thickness was determined on the basis of the intensity ratios of the C 1s and Au 4f emissions [32], assuming a standard exponential attenuation of the photoelectron signal and using the attenuation lengths reported by Lamont and Wilkes [33].…”

Azobenzene-functionalized alkanethiols in self-assembled monolayers on gold

“…For photoelectrons with around 100 eV kinetic energy, the attenuation length in alkanethiol SAMs amounts to about 5.4 Å [29]. Thus, for the photon energy of 400 eV, the C 1s XPS data are not quantitative, and the C 1s signal of both the Az6 and BP6 compounds will be dominated by the carbon atoms of the aromatic moieties.…”

Dipodal Ferrocene‐Based Adsorbate Molecules for Self‐Assembled Monolayers on Gold

“…The respective values were obtained from the C 1s/Au 4f intensity ratios, [49] using previously reported attenuation lengths. [50] Pertinent data are collected in Table 1. Whereas the thicknesses are quite small in each case, indicative of the formation of monolayer films, they do not fully correlate with the respective Fe 2p 3/2 intensities (Figure 7), even if one corrects for the different iron/carbon ratio in the adsorbate molecules.…”