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Imaging micropatterned organosilane self‐assembled monolayers on silicon by means of scanning electron microscopy and Kelvin probe force microscopy
Author(s) -
Wu Yunying,
Hayashi Kazuyuki,
Saito Nagahiro,
Sugimura Hiroyuki,
Takai Osamu
Publication year - 2003
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.1501
Subject(s) - kelvin probe force microscope , scanning electron microscope , monolayer , self assembled monolayer , analytical chemistry (journal) , acceleration voltage , microstructure , silicon , microscopy , materials science , scanning probe microscopy , chemistry , nanotechnology , optoelectronics , electron , optics , cathode ray , crystallography , composite material , organic chemistry , atomic force microscopy , physics , quantum mechanics
Field‐emission scanning electron microscopy (FE‐SEM) and surface potentiometry based on scanning probe microscopy, i.e. Kelvin probe force microscopy (KFM), have been applied to study microstructures consisting of organosilane self‐assembled monolayers (SAMs) terminated with ‐CH 3 or ‐CF 3 groups. Onto cleaned Si substrates covered with a thin oxide layer of 2 nm thick, SAMs were formed by chemical vapour deposition using n ‐octadecyltrimethoxysilane (CH 3 (CH 2 ) 17 Si(OCH 3 ) 3 , ODS) or fluoroalkylsilane (CF 3 (CF 2 ) 7 (CH 2 ) 2 Si(OCH 3 ) 3 , FAS) as a precursor. Through a photolithographic technique employing vacuum ultraviolet light at 172 nm, microstructures composed of ODS, FAS or both were fabricated. Micropatterns of the SAMs on SiO 2 /Si substrates were clearly imaged by FE‐SEM at an acceleration voltage of the electron beam below 1 kV, but image contrasts became faint with an increase in the acceleration voltage. At a voltage of 5 kV there was almost no detectable contrast. An FE‐SEM image of the ODS–FAS microstructure acquired at an acceleration voltage of 0.8 kV clearly demonstrated that the region covered with ODS was brighter and thus, emitted secondary electrons more efficiently than the region covered with FAS. Furthermore, as indicated in a KFM image, the region covered with FAS had a surface potential ∼180 mV lower than that of the region covered with ODS. The origin of these image contrasts between ODS‐ and FAS‐SAMs was the large difference in electronic states between ODS and FAS owing to the electron negativity of fluorine atoms. Copyright © 2003 John Wiley & Sons, Ltd.