Piezoresistive effect in DLC films and silicon

Hydrogenated amorphous diamond-like carbon (DLC, a-C:H) films were integrated in silicon boss membrane as a strain gauge material. The films were deposited at a bias voltage of -800 V by plasma-assisted chemical vapour deposition (PACVD). The a-C:H film with a 12-13 % of hydrogen showed hardness of 23 GPa. The film has around 24 % of sp3 content. The I-V characteristic is found to be Ohmic and the film has activation energy of around 0.32 eV. High gauge factor (K) values in the range of 16-36 were obtained, which were found to be independent of longitudinal and transversal strain configurations, current injection direction and of temperature in the range of 22-45 °C. P-diffused strain gauges using Borofilm 100 were also integrated in the boss membrane. High sensitivities in the range of 0.33-0.63 mV/V/mN were obtained, when vertical load was applied on the boss membrane.