Chemical Structure and Orientation of Ethylene on Si(114)−(2×1)/c(2×2)

Abstract

The basic chemical structure and orientation of ethylene chemisorbed on Si(114)-(2×1) at submonolayer coverage is characterized in ultrahigh vacuum using transmission Fourier transform infrared (FTIR) spectroscopy. The spectra are consistent with di-sigma bonding of ethylene to the surface with a preferential molecular orientation over macroscopic lengths. These results are supported by density functional theory (DFT) calculations of vibrational frequencies for optimized ethylene-Si(114) structures occupying the dimer and rebonded atom surface sites. A detailed analysis of the strong angular and polarization dependence of the C-H stretching mode intensities is also consistent with the adsorption structures identified by DFT, indicating that ethylene chemisorbs with the C-C bond axis parallel to the structural rows oriented along the [1 h10] direction on the Si(114)-(2×1) surface. The results indicate that the unique structure of this surface makes it an excellent template for elucidating relationships between surface structure and organic reaction mechanisms on silicon.

Ab Initio molecular dynamics study of ethylene adsorption onto Si(001) surface: Short‐time fourier transform analysis of structural coordinate autocorrelation function

“…Along the reaction pathway of the direct adsorption of the C 2 H 4(g) onto the Si interdimer, the calculated spectrogram as shown in Figure illustrates the evolution of the IR inactive peak of the CC stretching mode. First, before the adsorption of the C 2 H 4(g) onto the Si(001) surface, the spectrogram appears only in the IR inactive peak CC stretching mode (1666 cm −1 ), which is in a good agreement with the experimental data . Then, after the adsorption of the C 2 H 4(g) onto the Si interdimer, the IR active peak of SiC stretching mode (633 cm −1 ) is observed within the calculated spectrogram, which indicates that the C 2 H 4(g) has bonded with the Si interdimer to form the di‐σ‐bonded C 2 H 4(ads) .…”

“…As shown in Figure a, the initial C 2 H 4(g) , along the indirect adsorption, has IR active peaks of rocking mode (785 cm −1 ), wagging mode (919 cm −1 ), scissor mode (1425 cm −1 ), and CH stretching modes (3058 and 3161 cm −1 ) within the calculated IR spectrum . When this initial C 2 H 4(g) adsorbs on the Si dimer to form the π‐bonded C 2 H 4(ads) , the SiC vibrational mode (640 cm −1 ) appears immediately as shown in Figure b.…”

“…As shown in Figure 9a, the initial C 2 H 4(g) , along the indirect adsorption, has IR active peaks of rocking mode (785 cm 21 ), wagging mode (919 cm 21 ), scissor mode (1425 cm 21 ), and CAH stretching modes (3058 and 3161 cm 21 ) within the calculated IR spectrum. [37] When this initial C 2 H 4(g) adsorbs on the Si dimer to form the p-bonded C 2 H 4(ads) , the SiAC vibrational mode (640 cm 21 ) appears immediately as shown in Figure 9b. The p-bonded C 2 H 4(ads) also reveal IR active peaks of rocking mode (875 cm 21 ), wagging mode (947 cm 21 ), scissor mode (1417 cm 21 ), symmetrical CAH stretching mode (3021 cm 21 ), and asymmetrical CAH stretching mode (3129 cm 21 ).…”

Coverage-dependent chemisorption of Cl on Si(114)

“…Here, adsorption prefers R, followed by dimer, and lastly tetramer sites in agreement with Fig. 4c and studies of the adsorption of ethylene [17].…”

Irreversible structural transformation of Si(1 1 4)-2 × 1 induced by subsurface carbon

“…Among them, the Si(1 1 4) surface is known to have the simplest and single-domain structure composed of dimer (D), rebonded atom (R), and tetramer (T) rows [22][23][24]. Until now, several adsorption studies on Si(1 1 4) have been performed: hydrogen passivation for enhancing the potential of Si(1 1 4) as a substrate for homoepitaxy [25,26], the dissociative chemisorption of Cl 2 as a template for patterning via halogen-etching [27], and C 2 H 4 chemisorption for the development of methods to incorporate functional organic nanostructures onto semiconductor substrates for electronic and optoelectronic device applications [28]. But, the previous C 2 H 4 chemisorption study on Si(1 1 4) is limited to adsorption at room temperature (RT), which is not enough to achieve saturated C incorporation obtained at high temperatures.…”