The piezoresistive effect in diamond-like carbon films

Abstract

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.

Piezoresistive properties of diamond like carbon films containing copper

“…4b, Table 2). This is in good accordance with the model explaining piezoresistance phenomenon in diamond like carbon films [8,10] as well as with other studies on piezoresistivity of hydrogen free DLC films [12] and DLC films containing Ag [19,20] or Cr [18]. In those studies gauge factor of DLC films increased with sp 3 /sp 2 carbon bond ratio.…”

“…Recently piezoresistive effect in diamond like carbon films was found . Piezoresistive gauge factor comparable with the gauge factor of the main material of the semiconducting strain gauges silicon was reported [4][5][6][7][8][9][10]. Thus, in combination with the beneficial properties mentioned above, diamond like carbon films became an attractive material for fabrication of the advanced sensors capable to work in different harsh environments [14,[26][27][28][29][30][31][32].…”

Microstructure and properties of (Cr:N)-DLC films deposited by a hybrid beam technique

“…It is noted that the hardness of the (Cr:N)-DLC film is higher than that of Cr-DLC film, which may be due to the formation -C_N-H and Cr-N bonds in the (Cr:N)-DLC film. The hardness of the film is related to sp 3 /sp 2 bonding ratio and the amount of hydrogen [29]. The above XPS and Raman analysis show that the ratio of sp 3 /sp 2 in (Cr:N)-DLC decreases, but the formation of -C_N-H and C-N may be beneficial in keeping high hardness of (Cr:N)-DLC film.…”

In situ measurement of contact area in coated surfaces

“…Thus the current has to be kept very low or the voltage across the junction has to be kept constant, to avoid a non-linear response to changes of junction's cross sectional area that is involved in transport. Some films have piezoresistive properties, as shown from Tibrewala [14]. The polarity dependence found in measured results is small.…”