Abstract:
High-purity nanocrystalline niobium (Nb) thin films have been deposited using high-pressure
magnetron sputter deposition. Increasing the pressure of the sputtering gas during deposition has
systematically led to reduced crystallite sizes in these films. Based on x-ray and electron diffraction
results, it is observed that the nanocrystalline Nb films exhibit a significantly large lattice expansion
with reduction in crystallite size. There is however, no change in the bcc crystal structure on
reduction in crystallite size to below 5 nm. The lattice expansion in nanocrystalline Nb has been
simulated by employing a recently proposed model based on linear elasticity and by appropriately
modifying it to incorporate a crystallite-size-dependent width of the grain boundary.
