Iron Thin Films from Fe„CO…5 and FeCp2/H2O under Atmospheric Pressure

Abstract

Iron layers were first obtained from iron pentacarbonyl in metallorganic chemical vapor deposition MOCVD process under atmospheric pressure, in the temperature range 473–773 K, in a vertical cold wall reactor. Films of good purity were obtained with or without hydrogen as co-reactant, no chemical additives being used. The experiments showed that the velocity of the gas stream and, to a lower extent, the precursor molar fraction are the key parameters to be controlled, in order to monitor film growth rate and purity. In a second step, Fe thin layers were obtained by atmospheric pressure MOCVD starting from the reactive gas mixture FeCp2 and H2O in the temperature range 973–1073 K. A thermochemical simulation of the Fe-C-H-O system allowed optimum processing conditions to be approached. X-ray diffraction and microprobe analysis showed that the highest iron content in the layer was obtained for H2O/FeCp2 ratios between 4 and 6. Film growth occurs in two steps: the initial formation of a black, powdered, and porous layer that becomes densified as a result of the grain growth on increasing the deposition time in order to form compact gray metal films. This two-step mechanism was confirmed by kinetic and in situ IR pyrometric observations.