Three-layered sandwich structured carbon film prepared by sputtering and ion/electron/ion alternative irradiation

• ECR ion/electron irradiation was developed to prepare the sandwich structure films.
• A well-defined three-layer structure was observed in the TEM images.
• The conductive and paramagnetic characteristics of electron irradiated layer were remained.
• The structure contributed to improved hardness, smoothness, indentation and wear resistance.

The electron irradiated carbon film based on electron cyclotron resonance (ECR) sputtering technology has been proved to have both high conductivity and paramagnetism. However, the relatively low hardness, wear life and high surface roughness value limit its application in Micro-electromechanical Systems (MEMS). To improve these properties, the sandwich structured carbon films with different modulation ratios were introduced on silicon (100) wafers by alternative irradiation (ion/electron/ion) technique in ECR sputtering system. The three-layered nanostructure of films was measured with a transmission electron microscopy (TEM). The surface roughness of the film can be controlled to 0.19 nm according to the measurement of atomic force microscope (AFM). The unique characteristics of electron irradiated layer remained stable after irradiation through the analyzing of Raman spectroscopy. The mechanical properties (including hardness, elastic modulus, fracture behavior) and wear life were improved significantly due to the sandwich structure. The results showed that the sandwich structured carbon film is a kind of functional material equipped with enhanced mechanical and tribological properties.