Characterisation and investigation of ion-implanted boron-doped single crystal diamonds as temperature sensor for ultra-precision machining

Ultra-precision machining is a crucial manufacturing process for the production of optical components in automotive, medical and aerospace industry and enables high dimensional accuracies and low surface roughness values. Dedicated single crystal diamond tools enable the manufacturing of optical and functional surfaces such as mirrors or lenses. Despite the high mechanical hardness, temperature induced chemical wear of the diamond tools occures during the process. To characterise und interpret the wear behaviour of diamond tools, the cutting temperature needs to be analysed. At state of the art, there are no precise methods available for analysing temperatures in the cutting zone of a single crystal diamond tool in order to identify the wear behaviour online during the process. Therefore, a dedicated measurement system based on boron-doped CVD single crystal diamonds as temperature sensor was developed. The electrosensory features of the fully boron-doped diamonds enable a direct temperature measurement in the cutting zone. To enable high sensitive temperature measurements, ion-implantation was used for partial and specific boron-doping close to the cutting edge of single crystal diamonds. To fundamentally evaluate the quality of the doping and contacting structures as well as the general process of the ion-implantation three different doping structures were investigated using single crystal diamond blanks prior doping the cutting tools. For this purpose, the boron-doped structures were optically characterised and the correlations between the resistances and the temperatures were evaluated as a function of different doping-levels and doping-lengths. First results show the successful application of the ion-implantation for boron-doping of single crystal diamonds. It could be proven that the selected boron-levels as well as boron-lengths lead to different initial conditions of the analysed specimens. Dedicated ionimplantation of single crystal diamond tools represents a promissing approach as highly sensitive temperature sensor.