Low-temperature vapour deposition of high-purity iridium coatings from cyclooctadiene complexes of iridium. Synthesis of a novel liquid iridium chemical vapour deposition precursor

Abstract

High-purity, crystalline iridium coatings have been prepared by low-temperature chemical vapour deposition (CVD) from three volatile cyclooctadiene (COD) iridium precursors. One of these, (MeCp)Ir(COD)(MeCp = methylcyclopentadienyl), is a novel complex which melts at low temperature (40 °C) and therefore can be used as a liquid iridium source for CVD. When hydrogen is used as a carrier gas, iridium coatings containing < 1 atm % carbon are generated at ca. 120 °C using (MeCp)Ir(COD) and CpIr(COD)(Cp = cyclopentadienyl). Likewise, deposition under low oxygen pressure in partial vacuum also generates coatings free of carbon and oxygen. However, when the deposition is carried out in vacuo(no carrier gas), ca. 80% carbon is incorporated into the films. When [(COD)Ir(µ-OAc)]₂(OAc = acetate) is used as the metal-organic CVD (MOCVD) precursor, films containing < 1% carbon and oxygen are obtained at ca. 250 °C in vacuo without the need for a carrier gas.