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In this work, we fabricated the tetrahedral amorphous carbon (ta-C) films with thicknesses of 20 nm, 40 nm and hydrogenated diamond-like carbon (DLC:H) film with thickness of 1.1 μm on 316 stainless steel substrate (316SS). The electrochemical corrosion performances of two typical amorphous carbon (a-C) films in 3.5 wt% NaCl solution were focused. Results revealed that both ultrathin ta-C films exhibited superior corrosion resistance than that of DLC:H film, because the high content of sp3 bonded carbon and low porosity in ta-C films significantly suppressed the diffusion of corrosion media. However, a thickness threshold beyond 20 nm was proposed to obtain the superior corrosion resistance for ta-C films due to the emerged pitting of 316SS. For DLC:H film, the deterioration of corrosion resistance could be attributed to the hydrogen-containing interface, the large sp2 clusters with high electron transport, and the higher porosity density in carbon matrix. Image 1 • The effects of thickness, atomic bonds and porosity on corrosion of a-C were studied. • SVET revealed the distinct changes in local electrochemical performances for films. • Thick DLC:H exhibited limited corrosion protective efficiency. • Ultrathin ta-C with high sp3 content and low porosity remarkably reduced corrosion. [ABSTRACT FROM AUTHOR]

• The design, fabrication and testing methods of amorphous carbon force sensor were systematically studied. • The sensitivity was 9.8 μV/V/mN and non-linearity was about 2.0% FS, while it also showed a good repeatability. • In-situ depositing serious amorphous carbon films by simple, economic and green DC sputtering technic. • The piezo-resistive mechanism study result supported the thick film resistors (TFRs) theory well. The rapid growing demand of micro-electromechanical system (MEMS) sensors brings an urgent need for high performance and low cost sensitive materials. In this work, amorphous carbon (a-C) film was in-situ deposited on silicon substrate as strain sensitive component using economical direct current (DC) magnetron sputtering process and the a-C sensor was systematically designed, fabricated and tested. By adjusting the negative bias voltage in the range of 0–400 V, the gauge factor (GF) of the a-C film was adjusted within the range of 3.3–6.9. What's more, the film's sp2 cluster size played an important role in their piezo-resistive performance and conductivity, which illustrated the thick-film resistors (TFRs) theory. Additionally, CAFM results also supported the applying of TFRs theory in this work. Benefiting from the outstanding performance of a-C film, the MEMS force sensor, consisted a Wheatstone full-bridge with four a-C piezo-resistors, had a sensitivity of 9.8 μV/V/mN and non-linearity about 2.0% FS in the testing range of 0–210 mN, while it also showed a good repeatability. These investigations provided deeper insight into the piezo-resistive behavior of a-C film and contributed to the development of high performance and more economical sensitive materials for MEMS sensors. [ABSTRACT FROM AUTHOR]