Diamond-like carbon films as piezoresistors in highly sensitive force sensors

Diamond-like carbon (DLC) films have a high potential as piezoresistors in sensors for microtechnology applications. Since it has been reported that some films show very high strain sensitivity, DLC seems well suited for the use in highly sensitive sensors, e.g. force sensors for the nano Newton region. For DLC films produced by PECVD from hydrocarbons, the process parameters influencing the piezoresistive properties were systematically investigated. Therefore, pressure, gas flow, and substrate bias voltage were varied. The influence of the different parameters, especially on the strain sensitivity of the films, is discussed in this paper. An increase in gas flow and pressure leads to an increased gauge factor. Furthermore, higher strain sensitivity is achieved at lower substrate bias voltages. The different process parameters were optimized for the use of DLC films as piezoresistors in highly sensitive force sensors.

► Gauge factors up to 1000 were reached for diamond-like carbon films (a-C:H)
► Influence of substrate bias voltage, pressure, and gas flow on gauge factor was studied
► Among those, gas flow has highest impact on gauge factor
► Discussion of current models for piezoresistivity in a-C:H