Surface morphology and grain analysis of successively industrially grown amorphous hydrogenated carbon films (a-C:H) on silicon

Abstract

Silicon (1 0 0) has been gradually covered by amorphous hydrogenated carbon (a-C:H) films via an indus-trial process. Two types of these diamond-like carbon (DLC) coatings, one more flexible (f-DLC) and onemore robust (r-DLC), have been investigated. Both types have been grown by a radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) technique with acetylene plasma. Surface morphologieshave been studied in detail by atomic force microscopy (AFM) and Raman spectroscopy has been usedto investigate the DLC structure. Both types appeared to have very similar morphology and sp2carbonarrangement. The average height and area for single grains have been analyzed for all depositions. Arandom distribution of grain heights was found for both types. The individual grain structures betweenthe f- and r-type revealed differences: the shape for the f-DLC grains is steeper than for the r-DLC grains.By correlating the average grain heights to the average grain areas for all depositions a limited regionis identified, suggesting a certain regularity during the DLC deposition mechanisms that confines bothvalues. A growth of the sp2carbon entities for high r-DLC depositions is revealed and connected to astructural rearrangement of carbon atom hybridizations and hydrogen content in the DLC structure.