A detai
led photodissociation mechanism for the f
luorinated
lanthanide (Ln) β-diketonate meta
l−organic chemica
l-vapor deposition (MOCVD) precursors Ln(fod)
3, Ln(hfac)
3, and Ln(hfac)
3dig
lyme was e
lucidated using photoionization time-of-f
light mass spectrometry. The co
llision
less environment of the mo
lecu
lar beam source revea
led a series of unimo
lecu
lar steps, starting with dissociation of an intact β-diketonate
ligand. Dissociation steps for the second and third
ligands are associated with the attachment of a f
luoride to the meta
l ion,
leading to one of three u
ltimate products: Ln, LnF, or LnF
2. Except in the case of Pr, no LnO is observed. The pattern of
ligand fragmentation strong
ly supports a mechanism for the f
luoride-attachment step which is simi
lar to one previous
ly proposed for the therma
lly activated decomposition of Ce(hfac)
3g
lyme.
lick="showRef(this, 'ref1'); return false;" href="JavaScript:void(0);" class="ref">(1) The detai
led mechanistic understanding of the step-by-step f
luorination wi
ll provide a basis for new
ligand design, which maintains the advantageous mass-transport properties of the f
luorinated precursors whi
le contro
lling LnF
x formation.