Coating system for use as thin film sensor exhibiting enhanced sensitivity
A coating system to be used as thin film sensor includes a piezoresistive sensor element. The piezoresistive sensor element is a layer embedded in the coating system. The coating system is deposited on a surface of a substrate. The piezoresistive sensor element comprises at least one hydrogen free tetrahedral amorphous carbon coating doped with a ta-C:X coating layer, where X is one or more chemical elements selected from the elements groups 13 and 15 of periodic table of elements, wherein the ta-C:X coating layer exhibits an anisotropic gage factor.
1 . A coating system to be used as thin film sensor, the coating system comprising:
a piezoresistive sensor element,
wherein the piezoresistive sensor element is a layer embedded in the coating system,
wherein the coating system is deposited on a surface of a substrate,
wherein the piezoresistive sensor element comprises at least one hydrogen free tetrahedral amorphous carbon coating doped with a ta-C:X coating layer, where X is one or more chemical elements selected from the elements groups 13 and 15 of periodic table of elements, wherein the ta-C:X coating layer exhibits an anisotropic gage factor, and
wherein the ta-C:X coating layer has an anisotropic gage factor comprising a vertical gage factor and a longitudinal factor, where the vertical factor is at least ten times higher than the longitudinal gage factor.
2 . The coating system according to claim 1 , wherein the at least one ta-C:X coating layer exhibits:
a hardness HIT determined by nanoindentation techniques of at least 29 GPa,
an elastic modulus EIT determined by nanoindentation techniques of at least 300 GPa,
a carbon content determined by SIMS analysis of at least 90 at, and
a content of X determined by SIMS analysis of at least 2 at.
3 . The coating system according to claim 2 , wherein the at least one ta-C:X coating layer exhibits:
a hardness HIT determined by nanoindentation techniques in a range from 30 GPa and 45 GPa,
an elastic modulus EIT determined by nanoindentation techniques in a range from 330 GPa and 430 GPa,
a carbon content determined by SIMS analysis in a range from 91 at. % and 98 at. %, and
a content of X determined by SIMS analysis in a range from 2 at. % to 20 at. %.
4 . The coating system according to claim 1 , wherein X comprises:
nitrogen N, or
phosphor P, or
nitrogen N and phosphor P.
5 . The coating system according to claim 4 , wherein a nitrogen content in the of at least one ta-C:X coating layer is in a range from 2 at. % to 10 at.
6 . The coating system according to claim 5 , wherein the nitrogen content in the of at least one ta-C:X coating layer is in a range from 6.5 at % to 8.5 at. %.
7 . The coating system according to claim 4 , wherein ta-C-X is ta-C:N.
8 . The coating system according to claim 4 , wherein a N content in the ta-C:N coating layer in is a range from 6.5 at. % to 7.5 at. %.
9 . The coating system according to claim 1 , wherein the piezoresistive sensor element is contacted by electrically conductive connectors in such a manner that the piezoresistive sensor element provides an electrical signal as a function of at least a strain or temperature from the substrate surface.
10 . The coating system according to claim 1 , wherein the coating system comprises an under electrical insulating layer provided between the substrate surface and the piezoresistive sensor element.
11 . The coating system according to claim 1 , wherein the coating system comprises an adhesive layer provided directly onto the substrate surface.
12 . The coating system according to claim 1 , wherein the coating system comprises an upper electrical insulating layer provided directly onto the piezoresistive sensor element.
13 . The coating system according to claim 1 , wherein the coating system comprises at least one functional layer.
14 . A thin film sensor comprising a coating system according to claim 1 to be used for determining at least temperature or strain.
15 . A component, or a tool comprising a thin film sensor according to claim 14 , said thin film sensor incorporated in the component or tool for determining at least temperature or strain.
16 . A method for producing a coating system according to claim 1 , or for producing a thin film sensor according to claim 14 , wherein the at least one ta-C:X coating layer is deposited by using PVD or PA-CVD techniques.
17 . The coating system according to claim 1 , wherein X is one or more from B, Al, Ga, In, TI, N and P.
18 . The coating system according to claim 1 , wherein the longitudinal gage factor in a range from 4 to 20, and the vertical gage factor in a range from 100 to 450.
19 . The coating system according to claim 1 , wherein at least one functional layer is a DLC coating layer, or any other coating layer exhibiting specific tribological properties depending of the use.