A New Class of Organized Self-Assembled Monolayers - Alkane Thiols on Gaas(100)

C. Wade Sheen, Jeanne X. Shi, Jan Martensson, Atul N. Parikh, David L. Allara, Journal of the American Chemical Society 114, 1514 (1992)

We now report the discovery of a new class of organized monolayers derived from the self-assembly of alkanethiols directly onto the bare GaAs (100) surface. That viable S/GaAs chemistry might exist to allow self-assembly has been indicated by current studies which show that room temperature coverage of GaAs by deposits of inorganic sulfide salts,' P2S5,12a nd simple organothiol compounds (six carbons or less) exerts significant effects on electron-hole pair recombination velocities. We have produced SAMs from alkanethiols, X(CH,),SH for X = CH3 with n = 11-21 and X = C02H and C02CH3 with n = 15. The bulk of our characterization has been on octadecanethiol (ODT, X = CH,, and n = 17), and for brevity we focus on these results which show that the monolayer consists of a stable, highly organized assembly of tilted, conformationally ordered alkyl chains, chemically bonded directly to the bare GaAs surface.