Preferential atomic deposition and diffusion in multi-layered NiTi thin film

Abstract

In the present study, HRTEM micrograph of one-bi-layer and two-bi-layer of Ni/Ti thin film was investigated. Ni/Ti thin film was deposited with the help of DC/RF magnetron sputtering technique by layer-wise deposition of Ni and Ti on Si(100) substrate in the order of Ni as the bottom layer and Ti as the top layer. Four types of bi-layers are formed by varying the deposition time from 15 min to 30 min. The deposition of these amorphous asdeposited thin films were followed by annealing from 300 ºC to 600 ºC temperature with 1 hr annealing time to achieve the diffusion in between the layers. This work describes the microstructural changes in as-deposited thin film as well as the annealed thin film. It was found that, with the increase in annealing temperature, the diffusion at interface and atomic migration on the surface increases. Cross-sectional micrographs exhibited the inter-diffusion between the two layer-constituents, especially at higher temperatures and diffusion preferentially in angular direction. It was found that, with the increase in annealing temperature resulted in gradual increase in atomic-cluster coarsening with improved ad-atom mobility.