Sponsored Student: Hydrogen etching enabling well-adhered DLC on steel at low temperature

Diamond like carbon films (DLC) are state-of-the-art thin films based on amorphous carbon coating. These materials can have ultralow friction coefficient, high wear resistance and high hardness leading to energy-saving applications. Although the poor adhesion issues between DLC films and metallic substrate have been solved by hybrid PVD-PECVD technologies, the best cost option is to deposit a nanometric silicon interlayer. However the current works report processing temperatures as 300°C, this is considered relatively high to be applied in several material systems. In order to decrease the deposition temperature, the interlayers were exposed to hydrogen etching for 6 min at different deposition temperatures 85°C, 100°C, 125°C,150°C and 180°C to reduce oxygen amount and non-chemical affinity bonds. The samples were analyzed by glow discharge optical emission spectroscopy (GDOES), profilometry, field emission gun scanning electron microscope (FEG), scotch and scratch tests. A homogeneous adhered DLC film was achieved at all the studied parameters. The oxygen and silicon amounts in the interface interlayer/DLC were reduced, the ratio C/H increases and Si/C decreases with the increasing of temperature enabling more carbon-carbon bonds. A less rough surface was observed comparing with the same treatment parameters without hydrogen etching.