Co-Sputtering of C-AlN Novel Thin Films for Force Sensor Applications

Abstract

Nowadays Force Sensors are applied to monitor the life-time of metal parts or to observe the performance of components subjected to mechanical loading. A typical example is the real-time detection of forces produced on ball bearing steel by means of Diamond-like Coatings (DLC). Integrated force sensors can be placed either on the surrounding ring or in specific places of the component allowing the life-time monitoring of the whole component. Further potential applications areas for Force Sensors are in aircraft engines, wind power generation, etc. In the present project, thin films based on C-Al-N were produced by using the sputtering technique. An extensive parameter study including the variation of the power on C- and Al-targets and reactive gas (Ar+N2) flow was done in order to optimize the Al and N content in the thin films. Two sputtering concepts were studied to produce the C-Al-N containing thin film sensors. The results obtain with these two sputtering concepts will be presented and discussed here. The microstructure and the composition of the C-Al-N films were determined with a FE-SEM Gemini Ultra 55 from Zeiss equipped with an EDS from Oxford Instruments, XRD D5000 from SIEMENS, Raman and TEM Phillips Tecnai F30 microscope equipped with an Energy Dispersive X-ray Spectrometer (EDAX) operated at 300 keV. Extremely fine grains (below 50nm) are observed on the top view of the sensor films. The film appears amorphous and no crystalline AlN is detected by standard XRD analysis but Raman analysis indicates some of the carbon domains contain sp3 groups may be present and thus a diamond-like carbon structure is present in the nano-composites, relying on the position and intensity of D and G-Peaks. Different surface geometries are coated in order to determine their effect on the basis resistivity of the sputtered layers. The performance of the sensor films under uniaxial mechanical loading Instron machine was measured by means of a Source-meter from Keithley Instruments.