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The piezoresistive effect in diamond-like carbon films

: Tibrewala, A.; Peiner, E.; Bandorf, R.; Biehl, S.; Lüthje, H.


Journal of micromechanics and microengineering 17 (2007), Nr.7, S.S77-S82
ISSN: 0960-1317
ISSN: 1361-6439
Fraunhofer IST ()

Diamond-like carbon (DLC) film was deposited using plasma-assisted chemical vapour deposition (PACVD) at -350 V and -800 V. DLC strain gauges were integrated in bulk micromachined silicon. Optical bandgaps were found to be 1.2 eV and 1.03 eV at -350 V and -800 V, respectively. Films deposited at - 350 V have a higher hydrogen percentage, hardness, sp(3) content, resistivity and gauge factor compared to films deposited at -800 V. Piezoresistive gauge factors were measured under longitudinal and transversal strain configurations and in vertical and lateral current injection directions. It was found that the gauge factor was independent of the current injection direction and strain configurations. A model to explain the origin of the piezoresistive effect in DLC films along with parameters which can further enhance the gauge factor value of the films is discussed, which is confirmed experimentally.