Continuity and topography of ultrathin diamond-like carbon films characterized by scanning electron microscopy/energy dispersive x-ray analysis and atomic force microscopy

Abstract

Diamond-like-carbon coatings used as wear and corrosion barriers for hard disk drives are very thin and extremely smooth layers. Good morphological characterization of these ultrathin films is crucial to the good performance of the drive and has been attempted by scanning electron microscopy, energy dispersive x-ray (EDX) analysis and contact mode atomic force microscopy (AFM). Pure secondary electron images were obtained by subtracting out the backscattered component of the detected signal. EDX analysis was used for estimating the electron stopping power and the thickness of the coatings. Run-on spot analysis mode, EDX also permitted to check the continuity of these thin films. Contact mode AFM microscopy was carried out for a range of force set points. The contrast was found independent of force set point. Continuum mechanics calculations and preliminary adhesion measurements indicate that the contrast observed is purely topographic (Ra=1 nm). Finally, comparing the results, we found that the three different techniques complement each other to yield a more complete morphological characterization of these ultrathin films.