Electronic and Vibrational Properties of Thiophene on Si(100)

Abstract

The surface reactions of thiophene on Si(100)-2×1 have been investigated as part of a larger study on the interaction between five-membered heterocyclic aromatic molecules and silicon substrates. Using XPS, UPS, and HREELS, two adsorption states are identified at 120 K, corresponding to physisorbed and chemisorbed thiophene. The former desorbs below 200 K, whereas the latter strongly binds to the surface, showing lower C(1s) and S(2s) binding energies. HREELS reveals that chemisorbed thiophene is a 2,5-dihydrothiophene-like species which exhibits coverage-dependent reorientation from nearly parallel to tilted relative to the surface plane. Based on the frontier molecular orbital theory and work function measurements, an inverse Diels−Alder cycloaddition mechanism for thiophene with Si(100)-2×1 is proposed. Above 400 K, chemisorbed species either desorbs as molecular thiophene or decomposes possibly via α-thiophenyl and Si−H, and metallocycle-like intermediate and atomic S through a sulfur abstraction mechanism. By 1000 K, the S(2s) peak has disappeared, leaving silicon carbide on the substrate.

Chemical manipulation of multifunctional hydrocarbons on silicon surfaces

“…Similarly, the S 2s spectra of thiophene showed a feature at 227.4 eV for chemisorbed species at room temperature [254]. Upon surface annealing, further transformations take place based on oxygen and sulfur migration.…”

“…Experimental studies by Qiao et al employed a combination of photoelectron spectroscopy and HREELS to observe the presence of alkane groups in the adsorbate of both furan [238] and thiophene [254] and also to ascribe C 1s XPS peaks observed at 284.7 and 285.5 eV to α-and β-carbon atoms respectively, while O 1s spectra for furan exhibited only one peak at 532.3 eV [238]. Similarly, the S 2s spectra of thiophene showed a feature at 227.4 eV for chemisorbed species at room temperature [254].…”

Atomic and electronic properties of furan on the Si(001)-(2×2) surface

“…Based on low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), and ultraviolet photoelectron spectroscopy (UPS) data, they reported that the C 4 H 4 S molecule was chemisorbed molecularly on the Si(1 0 0) surface by the [2 + 2] cycloaddition mechanism. In contrast to above mentioned results, Qiao et al [14] suggested a [4 + 2] cycloaddition mechanism for the same surface reaction from UPS, XPS, and HREELS studies. The thiophene/ Si(1 0 0)-(2 Â 1) structure have also been theoretically studied by the hybrid density functional (B3LYP) method within a cluster model approach [11].…”

“…This rapidly growing field has been considered in a large number of experimental and theoretical investigation so as to elucidate the structural and electronic properties of such systems [4][5][6][7][8]. Among the heterocyclic hydrocarbons, the interaction of the thiophene (C 4 H 4 S) [9][10][11] and furan (C 4 H 4 O) [12][13][14] with the Si(1 0 0) surface has also attracted with a great attention because this organic semiconductor structures is the backbone of the highly ordered thin-film conducting polymers.…”

Adsorption and thermal decomposition of 2-octylthieno[3,4-b]thiophene on Au(1 1 1)

“…TPD spectra collected from Au(1 1 1) exposed to OTTP at 298 K in UHV for mass 2 (H 2 , top) and mass 34(H 2 S, bottom) with a heating rate of 2 K/s. whereas thiophene derivatives on Si(1 1 1) and Si(1 0 0) decomposed at room temperature and $450 K, respectively [36], suggesting that thermal decomposition of thiophene derivatives strongly depends on surface properties as well.…”