Silicon/molecule interfacial electronic modifications

Tao He, Huanjun Ding, Naama Peor, Meng Lu, David A. Corley, Bo Chen, Yuval Ofir, Yongli Gao*, Shlomo Yitzchaik, James M. Tour

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

85 Scopus citations

Abstract

Electronic structures at the silicon/molecule interface were studied by X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, inverse photoemission spectroscopy, and Kelvin probe techniques. The heterojunctions were fabricated by direct covalent grafting of a series of molecules (-C6H4-X, with X = NMe2, NH 2, NO2, and Mo6 oxide cluster) onto the surface of four types of silicon substrates (both n- and p-type with different dopant densities). The electronic structures at the interfaces were thus systematically tuned in accordance with the electron-donating ability, redox capability, and/or dipole moment of the grafted molecules. The work function of each grafted surface is determined by a combination of the surface band bending and electron affinity. The surface band bending is dependent on the charge transfer between the silicon substrate and the grafted molecules, whereas electron affinity is dependent on the dipole moment of the grafted molecules. The contribution of each to the work function can be separated by a combination of the aforementioned analytical techniques. In addition, because of the relatively low molecular coverage on the surface, the contribution from the unreacted H-terminated surface to the work function was considered. The charge-transfer barrier of silicon substrates attached to different molecules exhibits a trend analogous to surface band bending effects, whereas the surface potential step exhibits properties analogous to electron affinity effects. These results provide a foundation for the utilization of organic molecule surface grafting as a means to tune the electronic properties of semiconductors and, consequently, to achieve controllable modulation of electronic characteristics in small semiconductor devices at future technology nodes.

Original languageAmerican English
Pages (from-to)1699-1710
Number of pages12
JournalJournal of the American Chemical Society
Volume130
Issue number5
DOIs
StatePublished - 6 Feb 2008
Externally publishedYes

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