Effects of Electron Irradiation on Methylthiolate Monolayer on Au(111):  Electron-Stimulated Desorption

Abstract

Effects of electron irradiation on a methylthiolate (CH3S) self-assembled monolayer on Au(111) have been studied by using scanning tunneling microscope (STM), Auger electron spectroscopy (AES), low-energy electron diffraction, and thermal-desorption spectroscopy (TDS). AES results indicated that irradiation of the CH3S/Au(111) surface by an electron beam induces electron-stimulated desorption (ESD), in which mainly the methyl moiety desorbs via S−C bond cleavage, leaving a sulfur atom on the surface. From a quantitative analysis of TD spectra, the cross section of the ESD is estimated to be 2.8 × 10-17 cm2 for 100-eV electrons. Two-dimensional arrangements of the methylthiolate and the sulfur species under the ESD process have been investigated with STM. The STM observations indicated that the sulfur adatoms form 2D islands that grow in size with the progress of the ESD process, while unaffected methylthiolates are distributed between the sulfur islands. After the completion of the ESD, the Au(111) surface is covered with small patches (≲100 Å) of sulfur domains.

Shear-Induced Surface-to-Bulk Transport at Room Temperature in a Sliding Metal–Metal Interface

“…2a, profile II confirming the complete removal of sulfur. Note that the carbon in the methyl thiolate species is not detected since it undergoes rapid electron-stimulated desorption of the methyl moiety via S-C bond cleavage [15]. However, the presence of thiolate species on a copper surface was confirmed by surface infrared spectroscopy in a different UHV chamber, where subsequent Auger spectra of the same surface revealed only the sulfur Auger feature.…”

Methylthiolate adsorption on Au(111): Energetics, vibrational modes and STM imaging

“…In the case of short chain thiols, like methylthiolate, experiments [18] do not show atomic resolution, while for longer chain thiols it is not clear yet whether a c(4 · 2) or a ð ffiffi ffi 3 p  ffiffi ffi 3 p ÞR30 superstructure is seen [2]. In order to clarify the role played by the different geometrical degrees of freedom (twist and tilt angle, as well as adsorption site) in determining the aspect of STM images of methylthiolates on Au(1 1 1) at high coverages (1 ML), we have simulated constant current topographical STM images in Tersoff and Hamann's approximation [19].…”

Modification of thiol-derived self-assembling monolayers by electron and x-ray irradiation: Scientific and lithographic aspects

“…14,[19][20][21][22][23][24][25][26][27][28] However, most of the previous studies have focused on specific irradiation-induced processes and did not consider the overall changes taking place ͑exceptions are Refs. Regarding specific processes, electron irradiation-induced desorption of H 2 , 21 cleavage of C-S bonds, 26 cleavage of the C-H bonds in methyl and methylene entities ͑the respective cross sections were determined͒, 25 cross linking, and appearance of CvC bonds 23,24,27 have been studied. Regarding specific processes, electron irradiation-induced desorption of H 2 , 21 cleavage of C-S bonds, 26 cleavage of the C-H bonds in methyl and methylene entities ͑the respective cross sections were determined͒, 25 cross linking, and appearance of CvC bonds 23,24,27 have been studied.…”