FORMATION AND STABILITY OF SELF-ASSEMBLED MONOLAYERS ON THIN-FILMS OFLEAD-ZIRCONATE-TITANATE (PZT)

Self-assembled monolayers (SAMs) of alkylsiloxanes were formed from he xyltrichlorosilane (HTS) and octadecyltrichlorosilane (OTS) on surface s of thin films of a complex oxide, lead zirconate titanate (PZT). X-r ay photoelectron spectroscopy (XPS) and contact angle measurements con firmed the formation of a thin, uniform organic layer on the surface o f the PZT, consistent with the hypothesis that a densely packed organi c monolayer is formed on the PZT. Angle-resolved high-resolution XPS s uggested that the surface of the PZT thin film includes a top layer de ficient in titanium and consisting mainly of oxides of lead and zircon ium, along with hydroxylated zirconium that may react with alkyltrichl orosilanes to form the SAMs. The effect on these SAMs of exposure to a cidic media was probed by wettability measurements, XPS, and scanning electron microscopy(SEM). Contact angle measurements with water and he xadecane indicated that the SAMs formed from the longer alkylsilane, O TS, were stable in HCl over long periods of time (at least 3 days), wh ile the SAMs formed from the short-chain alkylsilane, HTS, degraded af ter 12 h. The XPS spectra of SAMs formed from OTS and exposed to HCl s olution were similar to those obtained for similar SAMs not exposed to HCl. SEM also confirmed that the SAMs formed from OTS can act as prot ective barriers for PZT against etching by HCl.