AVS 46th International Symposium
    Surface Science Division Friday Sessions
       Session SS3+EM-FrM

Paper SS3+EM-FrM3
Formation of Si/Thiophene Hybrid System in UHV by a Hetero Diels-Alder Cycloaddition Surface Synthetic Strategy

Friday, October 29, 1999, 9:00 am, Room 604

Session: Reactions on Semiconductors
Presenter: G.Q. Xu, National University of Singapore
Authors: Y. Cao, National University of Singapore
G.Q. Xu, National University of Singapore
Correspondent: Click to Email
The formation of organic monolayer on semiconductor surfaces has great device applications in biosensors, field effect transistors as templates for the epitaxial layer growth on semiconductors. In this work, the covalent coupling of thiophene monolayer on a semiconductor surface has been attained by a facile way at room temperature in UHV. We demonstrate here a hetero Diels-Alder cycloaddition reaction strategy for chemical modification of a well-defined Si(111)-7x7 surface with thiophene molecules. The concerted [4+2] cycloaddition reaction of thiophene with adjacent rest atom-adatom pair, resulting the formation of a 2,5-dihydrothiophenelike cycloadduct on Si(111)-7x7, has been clearly demonstrated by combined STM and HREELS spectroscopic studies. Documented as the least reactive diene in Deils-Alder cycloaddition reaction due to its high aromaticity, however, the cycloaddition reaction of thiophene on Si(111)-7x7 is facile even under UHV conditions. In addition, the reactivity of thiophene toward the rest atom-adatom pairs on Si(111)-7x7 can be theoretically explained by correlation of the the HOMO and LUMO energy of thiophene molecule and the surface band level for the empty and filled states on Si(111)-7x7. The feasibility of such procedure provides a better understanding of the chemical reactions proceed through semiconductor surfaces, more significantly, offers a potential new methodology for functionalization the semiconductor surfaces with desired control.