HIGH LATERAL RESOLUTION IMAGING BY SECONDARY-ION MASS-SPECTROMETRY OFPHOTOPATTERNED SELF-ASSEMBLED MONOLAYERS CONTAINING ARYL AZIDE

Imaging secondary ion mass spectrometry (SIMS) is used to map the dist ribution of molecular and elemental species in a patterned self-assemb led monolayer (SAM) with 1 mu m lateral resolution. The patterned SAMs are made by exposing polycrystalline Au to a solution of dis(11-(4-az ido(benzoyloxy))1-undecyl) disulfide, I, which forms a photosensitive SAM (Au-I) on the Au. Subsequent UV irradiation (lambda > 260 nm) of A u-I SAMs through a mask and a thin film of a secondary amine results i n attachment of the amine to the Au-I SAM only in the irradiated regio ns. The Au-I SAM is photosensitive by virtue of a pendant aryl azide g roup which reacts with secondary amines under UV irradiation to form h ydrazine or azepine photoadducts. A large molecular fragment ion corre sponding to vinyl ferrocene (m/z 212) was mapped with 1 mu m lateral r esolution on a Au-I SAM that had been irradiated through a mask and a thin film of (2-ferrocenylethyl)(2',2', 2'-trifluoroethyl)amine. SIMS can also detect intact molecular ions M(+) corresponding to the 3H-aze pine and hydrazine photoadducts obtained upon irradiation of Au-P SAMs in the presence of diethyl- and dibutylamines. Smaller fragment ions characteristic of the 3H-azepine and hydrazine adducts were also obser ved. The mass assignments were verified by a series of isotopic labeli ng experiments in which the observed ions displayed the expected isoto pic shifts.