J. Phys. IV France 104 (2003) 459
DOI: 10.1051/jp4:20030122

Imaging of patterned self-assembled monolayers by scanning photoelectron microscopy

R. Klauser¹, M. Zharnikov², I.-H. Hong¹, S.-C. Wang¹, A. Gölzhäuser² and T.J. Chuang<sup>3

1</sup>  Synchrotron Radiation Research Center, No. 1 R&D Road VI, Hsinchu 300, Taiwan
²  Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
³  Center for Condensed Matter Sciences, National Taiwan University, Roosevelt Road, Sec. 4, No. 1, Taipei 10764, Taiwan

Abstract
We have applied soft X-ray scanning photoelectron microscopy (SPEM) to image and characterize molecular pattems produced by electron irradiation of various aliphatic and aromatic thiol-derived self-assembled monolayers (SAMs) through masks. The fabricated patterns can be clearly distinguished and the inverse contrasts for the Au 4f and C 1s images suggest that the goal of "chemical" imaging bas been achieved. The thickness of the films in the irradiated areas appeared to be higher than that in the non-irradiated ones. This can be explained by the adsorption of airborne carbon-containing molecules on the irradiated areas. In addition, the N 1s images were acquired from the structured films of NO ₂(C ₆H ₄) ₂SH on gold to monitor the electron irradiation-induced transformation of the nitro tailgroups into amino moieties. However, no chemical contrast related to the nitro-amino transformation was observed. This can be explained by the small intensity of the nitrogen photoelectron emission with respect to the inelastic background originated from the substrate and by the X-ray induced modification of the lithographie pattern during the image acquisition. The modification of aromatic SAMs caused by the zone-plate-focused X-ray beam has been utilized for direct lithographic writing by the microprobe.

© EDP Sciences 2003