Site-Selective Deposition of Gold on Photo-Patterned Self-Assembled Monolayers

Siloxane-anchored self-assembled monolayers on glass were patterned by contact lithography using vacuum UV (193 nm) in air. Regionally separated OTS (octadecyltrichlorosilane) and APTES (3-aminopropyltriethoxysilane) were prepared by sequential deposition. The surface potential of OTS and APTES modified glass was determined with the streaming current between parallel sample plates separated by 100−150 μm. It was found that the isoelectric points (IEP) of OTS and APTES were pH 4.0 and 6.6, respectively. The gold thin film was selectively deposited from an aqueous solution of chloroauric acid (HAuCl 4 ) and l -ascorbic acid. At pH 6.5, OTS is negatively charged and repels the chloroauric ions, so gold deposition was not observed. On the other hand, because the pH was below the IEP of APTES-modified glasses, chloroauric ions were adsorbed by APTES SAMs and reduced in situ by ascorbic acid. After the initial Au was formed, Au was continuously deposited and metalized to form uniform thin films by autocatalysis. A micropattern of Au thin film on a glass substrate was thus successfully fabricated without the use of a seed or any etching process.