The adsorption of bis(hexafluoroacetylacetonato)zinc(II) on Si(111)-7x7

The adsorption of the organometallic compounds bis(hexafluoroacetylacetonat o)zinc(lI) (Zn(hfac)(2)) and bis(hexafluoroacetylacetonato)nickel(lI) (Ni(h fac)(2)) on the surface of Si(111)-7x7 were studied by a combination of sca nning tunnelling microscopy (STM) and X-ray photoelectron spectroscopy (XPS ). These compounds are analogues of the compound bis(hexafluoroacetylaceton ato)copper(II), which is an important precursor for the chemical Vapour dep osition of copper that we have previously studied. Both XPS and STM results indicate that the Zn(hfac), is adsorbed intact on the surface, and remains intact on the surface at temperatures up to 300 K. The XPS shows a transit ion from a physisorbed state to a chemisorbed state at temperatures between 160 and 300 K. At higher temperatures Zn(hfac)(2) decomposed to form Zn an d fluorocarbon fragments. The metal component diffused into the substrate. The Ni(hfac)(2) complex could not be successfully adsorbed on the Si surfac e: it was shown that this was due to decomposition of the molecule in the v apour phase, probably due to the higher temperatures needed to evaporate th is relatively involatile compound.