Pw. Gilberd et al., THE STRUCTURE AND OXIDATION OF HIGHLY CAVITATED METAL-SURFACES - A STUDY BASED ON TEM AND RAMAN-SPECTROSCOPY, Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms, 127, 1997, pp. 738-741
Highly cavitated layers formed in metal surfaces by He ion implantatio
n are of special interest in relation to potential catalytic applicati
ons. Here we report on a TEM study of coarse bubble structures produce
d in two representative metals with particular potential as catalysts,
Pt (fee) and Ti (hcp). For bubble sizes around 4 nm, the bubble struc
tures (described as cellular) are remarkably similar to those previous
ly reported for V. This suggests that at appropriate temperatures such
bubble structures may be a universal response to He implantation, ind
ependent of crystal type. For V, it is known that continued implantati
on to high He doses, beyond the ordered and cellular stages of bubble
development, can lead to structures involving large bubbles (diameters
exceeding 10-12 nm) in high concentration (companion paper, these Pro
ceedings, Nucl. Instr. and Meth. B 127/128 (1997) 734). Here we demons
trate for the first time that large bubbles in high concentration can
also be produced in Pt and Ti by suitable choice of implantation tempe
rature and He dose. The results encouraged us to examine the chemical
activity of a helium implanted surface. The particular example chosen
was the oxidation of cellular structures in V. It was found that Raman
spectroscopy is a powerful complement to TEM in investigating the ver
y thin oxide layers involved and that: (i) the oxides grow as oriented
crystallites with an abrupt interface to the underlying V, regardless
of the surface structures; and (ii) the nature of the surface can aff
ect the stoichiometry of the oxide phase with the cellular surface enh
ancing the formation of the higher oxide phases, in particular V2O5.