Surface and interface modification on nano-layers NiTi used for nano-electromechanical-system

Abstract

In nano-electronics competitive world, nano-electro-mechanical-systems are a special focus of interest. In this present study, we have discussed on the atomistic mechanism on the surface and at the interface of single-bi-layer (two alternative layers) and double-bi-layer (four alternative layers) of Ni/Ti using high resolution transmission electron microscopy (HRTEM). Ni and Ti was deposited with the help of DC/RF magnetron sputtering technique by layer-wise deposition 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 of each layer (15 min, 20 min, 25 min and 30 min). The deposition of these amorphous as-deposited thin films were followed by annealing at 300 ºC, 400 ºC, 500 ºC and 600 ºC temperature with 1 hr annealing time to achieve the diffusion in between the layers. It was found that, with the increase in annealing temperature from 300 ºC to 600 ºC, the diffusion at interface and atomic migration on the surface increases. With the increase in annealing temperature there is gradual increase in atomic-cluster coarsening with improved ad-atom mobility to improve the smoothness of the surface. Cross-sectional micrographs exhibited the inter-diffusion between the two layerconstituents, especially at higher temperatures. First time it is observed that the diffusion at the interface occur preferentially in angular manner through amorphous region.