A TEM study of the structure of magnetron sputtered chromium diboride coatings

Abstract

Chromium diboride thin films possess desirable combinations of properties, which are attractive for a wide range of potential industrial applications. However, these properties are strongly dependent on the deposition process and parameters. In this paper, CrB2 coatings deposited by DC and pulsed-DC magnetron sputtering of loosely packed blended powder targets are characterised by transmission electron microscopy techniques (electron diffraction and bright-field/dark-field imaging). Coatings with an extremely fine, nanocolumnar structure were observed. DC sputter deposited coatings exhibit a dense, short range ordered structure, while the pulsed-DC deposited coatings are defect-free, crystalline and show strong preferred orientation. A small amount of contamination of the interfacial sub-layers of the coatings by oxygen (from the target material) was found to affect the structure by suppressing growth of nanocolumns and promoting equiaxial grains of about 4-8 nanometres size, in the first ∼70 nanometres of coating, close to the substrate interface. The majority of the coating however remains nanocolumnar. © 2006 IOP Publishing Ltd.