  We present the first high pressure Raman study on nanocrystalline ZnO films
with different average crystallite sizes. The problem of low Raman signals from
nano sized particles was overcome by forming a nanocomposite of Ag and ZnO
nanoparticles. The presence of the nanodispersed Ag particles leads to a
substantial surface enhancement of the Raman signal from ZnO. We find that the
elastic modulus of nanocrystalline ZnO shows a non-monotonic dependence on the
crystallite size. We suggest that the non-monotonicity arises from an interplay
between the elastic properties of the individual grains and the intergranular
region.
