Research on application of diamond FAT for black lithium tantalate wafer processing based on nanoindentation and scratch techniques.

Lithium tantalate (LiTaO, LT) single crystal has been widely applied in the fields of electro-optical and piezoelectric devices. In this study, diamond fixed-abrasive tools (FAT) for LT were fabricated using consolidation abrasive processing technology to streamline the LT wafers processing and enhance overall effectiveness. The material properties and the critical depth for the ductile-to-brittle transition of LT were examined through nanoindentation and scratch techniques. The depth displacement curve exhibits significant periodic fluctuations at scratch depths of 150 nm and above. The critical load for the ductile-to-brittle transition, as determined by quasi-static scratch tests, was approximately 5.2 mN. Based on the calculated data, the actual processing load was estimated and subsequently validated through experiments conducted at varying loads. Scanning electron microscopy (SEM) and three-dimensional surface morphology analyses demonstrated that the predicted values were consistent with the actual processing results. Furthermore, the FAT developed in this study achieved superior surface roughness and higher material removal rate (MRR) compared to the free abrasive processing method. Surface roughness R of LT wafer processed by diamond FAT could be reduced from 208.6 nm to 2.8 nm. Specifically, the MRR of free abrasive processing was 12.4 μm/h, whereas that of the diamond FAT was 16.3 μm/h. Additionally, the surface roughness R of LT wafers processed with the diamond FAT was reduced from 208.6 nm to 2.8 nm. The results provide significant insights for the optimization and parameter selection in LT wafer processing.