Laser-Induced Deposition of Palladium and Gas-Phase Photofragmentation Pathways from (2-Methylallyl)(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato) Palladium

Abstract

Metallic palladium films are prepared at 10-2 Torr by 308 nm irradiation of gaseous (2-methylallyl)(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato) palladium. Gas-phase luminescence spectra recorded during the photochemical deposition process are used to identify photofragments. X-ray photoelectron analysis of the films shows that they consist primarily of palladium metal; the films produced with H2 carrier gas have no detectable fluorine and barely discernible carbon contaminants. The Pd films are polycrystalline fcc (face-centered cubic) palladium with preferential growth along the 111 direction. Scanning electron microscopy shows that the films formed with H2 carrier gas are smooth and consist of granules less than 35 nm in diameter. Further characterization of the gas-phase photofragmentation process is carried out by time-of-flight mass spectroscopy. The dominant peak present in the mass spectrum under 308 nm irradiation arises from palladium ions. No fragments containing palladium and other elements (especially PdC or PdF) are found. Pathways of photofragmentation, comparisons with other metal 1,1,1,5,5,5-hexafluoro-2-4-pentanedionate compounds, and the implications for laser-assisted chemical vapor deposition are discussed.