Surface, structural, electrical and mechanical modifications of pulsed laser deposited ZrN thin films by implantation of MeV carbon ions

Abstract

Atomic Force Microscope (AFM), X-ray Diffraction (XRD), four point probe and micro hardness techniques are utilized for studying the surface, structural, electrical and mechanical properties of ions beam irradiated nanostructured zirconium nitride (ZrN) thin films. Pulsed laser deposition technique is employed for the growth of ZrN thin films by using Nd:YAG laser (532 nm, 140 mJ, 6 ns, 10 Hz). The deposited films were irradiated with 2 MeV carbon (C+) ions at fluences ranging from 0.2 × 1015 to 1.8 × 1015 ions/cm2 by using Pelletron accelerator. AFM analysis reveals the formation of ion induced nano hillocks whose density and size are dependent upon ion irradiation fluence. The growth of these nanostructure is explained on the basis of thermal spike model. XRD analysis depicts higher angular shifting which leads to unit cell contraction along with evaluation of crystallite size, lattice parameter, strain and stresses at different ion fluences. The ion induced phase transition from metastable Zr3N4 to stable ZrN phase and the formation of new ZrC phase is also observed. The electrical resistivity explored by four point probe method is decreased after ion irradiation and is found to be dependent upon phase transformation as well as irradiation fluence. The ion irradiation induced increase in surface microhardness at different fluences is attributed to the change in crystallite size, formation of point defects and ZrC phases. The modifications in electrical and mechanical properties are well correlated with ion irradiation induced structural modification.