Atomically resolved scanning tunneling microscopy study of the adsorption and dissociation of methylchloride on Si(001)

Abstract

Adsorption of atomic hydrogen on the Si(001) 4×3-In surface studied by coaxial impact collision ion scattering spectroscopy and scanning tunneling microscopy J. Vac. Sci. Technol. B 17, 983 (1999); 10.1116/1.590680Scanning tunneling microscopy study of the adsorption of toluene on Si (001) The room-temperature adsorption and dissociation of methylchloride ͑CH 3 Cl͒ on Si͑001͒ using scanning tunneling microscopy has been studied. Fragments are identified by the symmetry of their binding on the underlying Si͑001͒ lattice. Methylchloride adsorbs dissociatively at room temperature, yielding a methyl group and a chlorine atom bound to the surface. Chlorine atoms bind in a variety of geometries, the most common being two chlorine atoms bonded to a single silicon dimer ͑silicon monochloride dimers͒. When the surface is heated to 150°C, all Cl rearranges to this monochloride-type bonding configuration, and images reveal the beginnings of monochloride island formation. The Cl:CH 3 ratio on the surface is found to be approximately 2:1, implying that not all methyl groups are bound to the surface in the reaction.

Atomically-Resolved Studies of the Chemistry and Bonding at Silicon Surfaces

“…As a result, they readily bond to the Si(001) surface, terminating the “dangling bonds” in much the same way that hydrogen does in the monohydride structure. One of the most interesting halogen systems has been chlorine on Si(001). − At high chlorine exposures, it is generally recognized the Cl 2 does indeed form a (2×1) “monochloride” structure at one monolayer Cl coverage. ,, Indeed, STM investigations using methyl chloride as a chlorine source show formation of ordered (2×1) monochloride regions …”

“…Bronikowski et al investigated the interaction of methyl chloride with Si(001) . One motivation for investigating CH 3 species is that, since it is isoelectronic with SiH 3 , a comparison of the STM images resulting from these two fragments provides some insight into the application of STM to identify unknown molecular fragments.…”

“…The work of Bronikowski et al focused on samples prepared by exposing Si(001) to CH 3 Cl at room temperature followed by a brief anneal at 420 K. Since previous studies using methyl iodide have shown that methyl groups are stable up to 600 K, , the only species present on the surface after this exposure−anneal cycle should be Cl and methyl groups. The Cl atoms produced by dissociation pair onto the Si(001) dimers, forming a “monochloride” structure identical in all respects with that observed by Boland .…”

CH3Cl/Cu(410): Interaction and Adsorption Geometry

“…As one would expect, the (direct) reaction of CH 3 Cl with pure Si plays an important role in understanding the reaction mechanism. Surface science studies − found dissociative adsorption of CH 3 Cl/Si­(100) and molecular adsorption of CH 3 Cl/Si­(111). On the other hand, contrary to expectations, studies have found Cu 3 Si alloy surfaces rather inert to CH 3 Cl. , It is still not clear how Cu catalyzes the (direct) reaction.…”

Temperature-Programmed Desorption (TPD) and Density Functional Theory (DFT) Study Comparing the Adsorption of Ethyl Halides on the Si(100) Surface

“…Among organic modification schemes, the reactions of alkyl halides with elemental semiconductor surfaces including porous silicon as well as silicon and germanium single crystals have been investigated as a means to introduce model simple functional groups, alkyls, to the surface. For example, the dissociation of methyl halides (CH 3 Cl, CH 3 Br, CH 3 I) on Si(100) − can lead to a controlled formation of mixed methyl and halogen monolayers. Although similar species can be formed by a direct dissociative adsorption of molecular halogens (Cl 2 , Br 2 , I 2 ) or hydrogen halogenides (HCl, HBr, HI), − the reactions of these species are often complicated by additional pathways.…”