Large differences in the optical properties of a single layer of Si on Ag(110) compared to silicene

Abstract

The optical properties of Si nanoribbons grown on Ag(110) under ultrahigh vacuum have been experimentally determined by use of in situ surface differential reflectance spectroscopy. Real-time measurements showed a clear transition of the optical response of the Si deposit at full coverage of the Ag(110) surface, corresponding to 0.8 monolayer of silicon. The spectra measured for the complete self-assembled nanoribbon layer are different from the reflectance spectrum calculated for a layer of silicene on silver, which rules out the possible silicenelike character of this layer. Furthermore, the dielectric function of the nanoribbons is calculated from the experimental data and is similar to the one of amorphous silicon, with a red shift of about 0.6 to 0.8 eV of the main absorption feature. This result indicates that the Si nanoribbons display a preferential sp 3 hybridization as in amorphous Si and not a partial sp 2 hybridization as expected for silicene.

Unveiling the pentagonal nature of perfectly aligned single-and double-strand Si nano-ribbons on Ag(110)

“…Since their discovery in 2005 (ref. 15 ) the atomic structure of Si NRs on Ag(110) has remained elusive and strongly disputed 15 16 17 18 19 20 21 22 23 . Figure 1 presents a summary of Si NRs measured with STM.…”

Noncontact AFM and differential reflectance spectroscopy joint analyses of bis-pyrenyl thin films on bulk insulators: Relationship between structural and optical properties

“…The method now permits to perform polarization-sensitive measurements [41,42], with a sensitivity in the 10 −4 range [43]. Concerning atomic adsorbates on substrates, DRS has been used to investigate the optical properties of oxygen and hydrogen on Si(001) [44][45][46][47], oxygen on InAs(001) [48], heteroatoms on III-V compounds [49], Si on Ag(110) [41], etc. to name a few.…”

Silicene: Recent theoretical advances

“…Silicene nanoribbon is found to be stable under tensile strain up to 20%, while a freestanding silicene nanoribbon is predicted to be subject to slight buckling (sp 2 -sp 3 hybridization); 12 the bonding character of a supported silicene nanoribbon on Ag(110) substrate is still under debate. Borensztein et al argue that the optical adsorption points to sp 3 hybridization, 42 whereas Padova et al favor sp 2 bonding based on results of reflection electron energy loss spectroscopy. 43 An armchair silicene nanoribbon is found to be a nonmagnetic semiconductor.…”