X-ray Induced Damage of Self-Assembled Alkanethiols on Gold and Indium Phosphide

Abstract

We have performed an X-ray photoelectron spectroscopy (XPS) study in order to investigate thiolate monolayers on gold and indium phosphide. Evidence is presented that alkanethiols (chain length 10, 12, 16, and 18) also adsorb to form passivating monolayers on InP(110). An increasing degradation of the thiolate films has been observed on both types of substrates during extended exposure to X-rays. Several features in the spectral shapes of the core level spectra and their intensity evolution are discussed in terms of different types of layer damage. The chemical damage is indicated by the appearance of a new radiation-induced sulfur species. Spectroscopic evidence as obtained from both XPS and X-ray absorption near edge structure has been provided that indicates this species might be of disulfidic nature. Both sulfur and carbon disappear from the surface in about comparable amounts, clearly demonstrating significant structural damage of the thiolate films. The layer damage by the X-rays proceeds much faster and significantly stronger on gold films than on InP. This result is discussed in terms of structural defects and electron-induced effects. Evidence is provided for a significant contribution of backscattered and secondary electrons to the damage of the adsorbed organic layers. Patterning of alkanethiolate layers by an electron probe of a scanning Auger unit has been demonstrated.

Pressure Dependence of ZnDTP Tribochemical Film Formation: A Combinatorial Approach

“…The sulphur 2p 3/2 peak was found at 162.2 ± 0.1 eV, and can be assigned to a sulphur having a formal oxidation state of -2, as found in sulphides [48,49], thiolates [50,51] or when sulphur is substituting oxygen atoms in poly(thio)phosphates.…”

XPS study of the influence of temperature on ZnDTP tribofilm composition

“…In the case of sulphur, two different peaks, each composed of S2p 3/2 and S2p 1/2 , were detected: one at 162.1 eV assigned to sulphides [7,28,29] and thiols [30,31] and one at 168.8 eV assigned to sulphate groups [29,32]. The most intense component in the carbon signal was from aliphatic carbon (C-C, C-H), found at 284.8 ± 0.1 eV.…”

Electronic Properties of Interfaces between PCPDTBT and Prototypical Electrodes Studied by Photoemission Spectroscopy

“…The adsorption of the SAM results in the removal of carbon contamination layers. [16,27] The chemical interaction between PCPDTBT and Au discussed below suggests that also for the system considered herein the contamination can be replaced by the polymer. Therefore, we use the work function of Au after preparation in UHV for the discussion of the electronic properties.…”

“…A chemical interaction between sulfur and Au has already been investigated for other systems such as thiols. [16,27] On the other hand, for thiophenes, such interactions are not yet known. The appearance of an additional peak only in the S 2p spectra, reveal a local chemical interaction between Au and the sulfur atoms in PCPDTBT.…”