Half-sandwich cobalt complexes in the metal-organic chemical vapor deposition process

A series of cobalt half-sandwich complexes of type [Co(η5-C5H5)(L)(L′)] (1: L, L′ = 1,5-hexadiene; 2: L = P(OEt)3, L′ = H2CCHSiMe3; 3: L = L′ = P(OEt)3) has been studied regarding their physical properties such as the vapor pressure, decomposition temperature and applicability within the metal-organic chemical vapor deposition (MOCVD) process, with a focus of the influence of the phosphite ligands. It could be shown that an increasing number of P(OEt)3 ligands increases the vapor pressure and thermal stability of the respective organometallic compound. Complex 3 appeared to be a promising MOCVD precursor with a high vapor pressure and hence was deposited onto Si/SiO2 (100 nm) substrates. The resulting reflective layer is closed, dense and homogeneous, with a slightly granulated surface morphology. X-ray photoelectron spectroscopy (XPS) studies demonstrated the formation of metallic cobalt, cobalt phosphate, cobalt oxide and cobalt carbide.