Two most useful families of copper CVD precursors that have been utilized widely are the Cu(I) and Cu(II) £]-diketone complexes. The Cu(II)precursors require the use of an external reducing agent such as hydrogen to deposit copper films, i.e. CuII(£]-diketonate)2 + H2 ¡÷ Cu0+2 £]-diketonate. The Cu(I) precursors deposit pure copper films without the use of an external agent via a disproportionation reaction that produces a Cu(II)£]-diketonate in conjunction with other organic byproducts, i.e. 2CuI(£]-diketonate)L ¡÷ Cu0+ CuII(£]-diketonate)2+2L where L is a typical Lewis base neutral ligand. However, Do those ligands resulting from the dissociation of the precursors simply desorb intact from the substrate or the growing films, or react further on the surface? To understand the surface chemistry of these ligands may provide better knowledge for designing more superior precursors and improvement of fabrication processes. Cu(hfac)(VTMS) and Cu(hfac)(MHY) are the most promising Cu(I) precursors, as shown in Scheme 1.1. Here we report studies on the chemistry of VTMS, MHY and hfacH on a Cu(111) surface. It should be noted that the hfacH is the simplest molecule containing the hfac, so we use it as a reference for £]-diketonate ligand. The Cu(111) single crystal was used to mimic the reactivity of these ligands on a growing Cu film during copper CVD. In situ analysis of ligand surface chemistry is carried out by TPD/R (temperature-programmed desorption/reaction) and RAIRS (reflection adsorption infrared spectroscopy) to elucidate plausible reaction mechanisms by which ligands decompose and eventually lead to impurity incorporation into the growing films, and to suggest means of minimizing such reactions.