The continuing drive towards miniaturization of electronic devices(1)
is motivating the search for new materials. Consider, for example, the
case of the much-used dynamic random-access memory, The minimum capac
itance per cell that can be tolerated is expected(2) to remain at 30-4
0 fF, but as the cell area decreases, the corresponding reduction in g
eometric capacitance has to be compensated for. So far, this has been
achieved by resorting to complex non-planar structures and/or using mu
ch thinner films of the dielectric insulator, amorphous silicon dioxid
e (a-SiOx), although the latter approach is limited by the electric fi
elds that can be supported by a-SiOx before its insulating properties
break down. An alternative strategy is to develop thin-film insulators
that have a dielectric constant significantly greater than that of a-
SiOx, reducing the size of the fields required for device operation. H
ere we show that a composition-spread technique allows for the efficie
nt evaluating of materials,vith both a high dielectric constant and a
high breakdown field, We apply this approach to the Zr-Sn-Ti-O system,
and we find that compositions close to Zr0.15Sn0.3Ti0.55O2-delta are
better thin-film dielectrics than high-quality deposited a-SiOx, Altho
ugh detailed tests of the performance of these materials have not yet
been carried out, our initial results suggest that they are likely to
be comparable to the best alternatives (such as (Ba, Sr)TiO3) currentl
y being considered for integrated-circuit capacitors.