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Initial stages of Fe chemical vapor deposition onto Si(100).

We study the evolution of layer morphology during the early stages of Fe chemical vapor deposition (CVD) onto Si(100) via pyrolysis of Fe(CO){sub 5} below 25 {degree}C. Scanning tunneling microscopy (STM) shows that nuclei formation is limited by precursor dissociation which occurs on terraces, not at step sites. Also, the average size of clusters formed during CVD is larger than for Fe growth by evaporation (a random deposition process). Based on STM data and Monte Carlo simulations, we conclude that the CVD-growth morphology is affected by preferential dissociation of Fe(CO){sub 5} molecules at existing Fe clusters---an autocatalytic effect.