IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research

IGC
Annual Report 2007
VI.2. Microstructural Studies of Nanocomposite Thin Films
of Ni/ CrN Prepared by Magnetron Sputtering
Synthesis of metal nitrides and
metal / metal nitride
composites is very challenging
as they provide a good
illustration how materials
properties can significantly be
improved. Combination of
different materials creates
interfaces whose properties and
processing needs to be
understood to apply these
materials for technological
applications. It is the objective
of this work is to emphasize the
importance of composite
materials formed by metallic
particles dispersed within
another insulating or
nanocrystalline (nc) matrix.
Metal/nc-matrix interfaces play
a key role in the understanding
of many fundamental
properties. These interfaces
play a crucial role in a wide
range of technological
applications such as
heterogeneous catalysis, fuel
cells, microelectronics and
optoelectronics, as well as
structural components. In
addition, the metallic content
and particle size effect are
important issues in the design
of properties, for instance,
mechanical properties. Previous
experimental results of
hardness of nanostructured
metals or metallic superlattices
clearly indicate that hardness
increases with decreasing grain
sizes following d -1/2 dependence
known as the Hall-Petch effect.
However, this trend is reversed
for particle sizes less than
20nm for which the hardness
decreases due to a grain sliding
process along particle
boundaries. The increase in
hardness is based on hindering
of the movement of dislocations
by the formation of sharp
interfaces between several
nanometers of thin layers of
materials with a large
difference in elastic shear
moduli.
Nanocomposite coatings are
deposited by a variety of
techniques including hightemperature
chemical vapor
deposition (CVD) and lowtemperature
reactive sputtering,
activated reactive evaporation
and plasma CVD. The plasma
techniques provide, besides the
low deposition temperature, the
possibility to control the ion
bombardment of the growing
film which results in a smaller
grain size, a less columnar
structure and a controllably
Fig.1(a) SEM micrograph of Ni/ CrN film prepared at 773 K at 10sccm, and (b) EDX analysis of the film.
BASIC RESEARCH 147