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However, many potential applications for barium
titanate require a thin-film form rather than a bulk crystal. Despite
substantial advances in deposition technologies for barium titanate
thin films, researchers have faced continued difficulty in obtaining
high-quality, single-crystal thin films, since they require lattice
matching to the growth substrate. CIS looks set to offer researchers a
solution to these problems.
"The CIS technique enables one to slice a 0.5
micrometers to 10 micrometers-thick layer of material from a bulk
single-crystal wafer by implanting the wafer with high-energy ions and
subsequent thermal treatment or wet etching of the buried sacrificial
implant-damaged layer," says Technical Insight Industry Manager Girish
Solanki.
Essentially, this technique uses ion implantation
to modify the chemical and physical properties of materials and obtain
mesoscopically thin, single-crystal films.
Post ion slicing, researchers used sophisticated
analytical tools such as atomic force microscopy (AFM) to examine the
samples' surface roughness and domain structure. They observed a
change in the wafers' domain structure from single to multidomain as
well as a periodic structure in the surface topography.
Using a near-field scanning microwave microscope (NSMM),
researchers also noted that the barium titanate film retained the
permittivity of the bulk crystal and exhibited low dielectric loss;
they attributed the latter to stress induced by residual implanted
ions and a thermal expansion mismatch between the substrate and the
film.
Observing the large permittivity of the sliced
barium titanate films, researchers concluded that it was possible to
fabricate a small-sized, large-capacitance, integrated capacitor on
CIS single-crystal films.
Commenting on the future of barium titanate,
Solanki says, "As far as practical areas of application are concerned,
the heterogeneous integration of the material makes it possible to
realize multi-functional microwave and optical devices. Barium
titanate is also a promising material for memory applications." |
