Photofragmentation Pathways and Photodeposition of Nanoparticles from a Gas Phase Copper-Containing Precursor

Abstract

Pulsed laser excitation of bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) (Cu(TMHD)(2)) in the gas phase produced neutral gaseous copper atoms and nanoparticulate copper deposits on substrates. Copper atoms were formed by the complete dissociation of the ligands from the metal. Time of flight mass spectrometry and resonance enhanced multiphoton ionization spectroscopy were used to study the details of this reaction and led to the discovery of other gaseous fragments that were produced by incomplete fragmentation of the ligands including monoligated species and coordinated ligand fragments. Laser-assisted chemical vapor deposition resulted in monodispersed nanoparticles under 100 nm in diameter. X-ray photoelectron spectroscopy and energy dispersive analysis of X-rays were used to determine the elemental composition of the deposit. The relationships between the photofragmentation pathways and the deposited particles are discussed.

Photodissociation and Photoionization Mechanisms in Lanthanide-based Fluorinated β-Diketonate Metal−Organic Chemical-Vapor Deposition Precursors

“…There has been considerable effort directed toward understanding more general MOCVD fragmentation mechanisms in the past decade, including, for example, monitoring in situ luminescence and infrared absorbance (FTIR), , and trapping volatile intermediates and byproducts of the deposition and analyzing them with electron impact ionization (EI) mass spectrometry. Except for two early publications, , it is only recently that the wealth of mechanistic detail available through PI-TOF-MS has become clear. ,− The fluorinated lanthanide-based MOCVD precursors discussed in this work provide another convincing example of the potential for this technique.…”

“…Understanding the photochemistry of gas-phase metal−organic compounds is fundamental to harnessing the full potential of laser-assisted metal−organic chemical-vapor deposition (L-MOCVD or LCVD), which can produce superior films, with finer grain boundaries and improved purity, as compared to traditional thermal activation techniques. − Another advantage of LCVD over traditional thermal techniques is the potential for deposition on a wider range of substrates, including materials with poor thermal conductivity, or materials which cannot withstand elevated temperatures . LCVD technology has broad practical applications, including direct-write technology; deposition of amorphous carbon (α-C) films; carbon nanotubes; , W, Mo, and V films; TiN films; TiO 2 films; W nanoparticles; N-rich GaN 1− x P x films and single quantum wells; , N-rich GaInNP multiple quantum well structures; and polycrystalline Si solar cell applications…”

Thin Film Deposition and Photodissociation Mechanisms for Lanthanide Oxide Production from Tris(2,2,6,6-tetramethyl-3,5-heptanedionato)Ln(III) in Laser-Assisted MOCVD

“…In general, preparation of oxide films requires the presence of a coprecursor or subsequent exposure to an oxidizing atmosphere . In a recent series of studies on β-diketonate complexes, the gas-phase photolytic mechanisms, which lead to production of reduced metal, − ,, and the mechanisms that lead to carbide and fluoride contamination in deposited films were examined. It was also noted that photolysis of the common lanthanide oxide precursor, tris(2,2,6,6,-tetramethyl-3,5-heptanedionato)Ln(III), or Ln(thd) 3 , resulted in significant formation of gas-phase LnO in addition to the reduced metal, Ln 0 . − Formation of the reduced metal was attributed to three sequential ligand-to-metal charge-transfer (LMCT) steps, wherein the anionic ligand reduced the metal and was itself ejected intact from the complex as a neutral thd radical.…”

Photofragmentation of Gas-Phase Lanthanide Cyclopentadienyl Complexes: Experimental and Time-Dependent Excited-State Molecular Dynamics

“…However, the potential still remains for hydrocarbon contamination in the deposited films. In previous work, we − and others − have shown that photoionization time-of-flight mass spectrometry (PI-TOF-MS) is a useful tool for elucidating photofragmentation mechanisms in gas-phase MOCVD precursors, including processes giving rise to fluoride contamination from frequently used fluorinated precursors.…”