Electron Processing at 50 eV of Terphenylthiol Self-Assembled Monolayers: Contributions of Primary and Secondary Electrons

Abstract

Aromatic self-assembled monolayers (SAMs) can serve as platforms for development of supramolecular assemblies driven by surface templates. For many applications, electron processing is used to locally reinforce the layer. To achieve better control of the irradiation step, chemical transformations induced by electron impact at 50 eV of terphenylthiol SAMs are studied, with these SAMs serving as model aromatic SAMs. High-resolution electron energy loss spectroscopy (HREELS) and electron-stimulated desorption (ESD) of neutral fragment measurements are combined to investigate electron-induced chemical transformation of the layer. The decrease of the CH stretching HREELS signature is mainly attributed to dehydrogenation, without a noticeable hybridization change of the hydrogenated carbon centers. Its evolution as a function of the irradiation dose gives an estimate of the effective hydrogen content loss cross-section, σ = 2.7-4.7 × 10(-17) cm(2). Electron impact ionization is the major primary mechanism involved, with the impact electronic excitation contributing only marginally. Therefore, special attention is given to the contribution of the low-energy secondary electrons to the induced chemistry. The effective cross-section related to dissociative secondary electron attachment at 6 eV is estimated to be 1 order of magnitude smaller. The 1 eV electrons do not induce significant chemical modification for a 2.5 mC cm(-2) dose, excluding their contribution.

Response under low-energy electron irradiation of a thin film of a potential copper precursor for focused electron beam induced deposition (FEBID)

“…All available complex material is then considered exposed to the irradiation beam from the beginning of the experiment. As already used in a previous publication [ 36 ], the decrease in the signal follows an exponentially decreasing law: where S 0 is the initial signal intensity, σ is the cross section (in cm 2 ) and is the beam fluence (in cm −2 ), i.e., the integrated number of incident electrons over time. The desorption signal must decrease and drop to zero when the compound is fully consumed.…”

“…Experimental setup in Orsay, France: The experiment setup at ISMO in Orsay, France is detailed in previous publications [ 29 , 36 , 46 ]. Samples are mounted on the cold finger of the cryostat and their temperature can be controlled from 30 K to 750 K. The temperature is measured with a Pt103 sensor and a Lakeshore 335 controller with an accuracy of 1 K.…”

“…It houses an ELG2 electron gun (Kimball physics) and a quadrupole mass spectrometer (3F-PIC- Hidden Analytical). Neutral fragment desorption induced by low-energy electron impact is recorded following a procedure described in previous publications [ 29 , 36 ] improved here with the pulsing of the electron gun in place of the sample potential. The irradiation spot has 6 mm in diameter, with a current close to 1 μA.…”

Electron-induced fragmentation mechanisms in organic monomers and their implications for photoresist optimization for EUV lithography

“…For polyatomic molecules, more than one neutral fragment may be formed. [13][14][15][16][17][18][19][20] DI, DEA and, DD processes can be studied through Mass Spectrometry (MS), as they produce charged fragments. The neutral species may also be studied by mass spectrometry after desorption through post ionization e.g.…”

Amplified cross-linking efficiency of self-assembled monolayers through targeted dissociative electron attachment for the production of carbon nanomembranes

“…Similarly, from the DEA threshold energy, we expect C–H cleavage through DEA to be present but inefficient. In fact, Houplin et al [ 32 ] recently showed that for terphenyl-thiol (TPT) SAMs, which should behave similar to the native BPTs, DEA is an insignificant process.…”