Optimized pre-thinning procedures of ion-beam thinning for TEM sample preparation by magnetorheological polishing

• Published in: Ultramicroscopy 2017-10, Vol.181, p.165-172
• Main Authors: Luo, Hu, Yin, Shaohui, Zhang, Guanhua, Liu, Chunhui, Tang, Qingchun, Guo, Meijian
• Format: Article
• Language: English
• Subjects: Ion milling; Magnetorheological polishing; Pre-thinning; Sample preparation technique; Transmission electron microscopy
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/j.ultramic.2017.05.016

•A simplified pre-thinning method of ion-beam thinning for TEM sample preparation is proposed.•This new method can reduce physical labor of researchers during mechanical pre-thinning.•The MR technique is free from dimpling related defects.•High-resolution TEM images with high quality could be acquired after MR polishing and one side ion-thinning.•This technique may have additional advantage in TEM sample preparation of multi-layer thin films grown on substrates. Ion-beam-thinning is a well-established sample preparation technique for transmission electron microscopy (TEM), but tedious procedures and labor consuming pre-thinning could seriously reduce its efficiency. In this work, we present a simple pre-thinning technique by using magnetorheological (MR) polishing to replace manual lapping and dimpling, and demonstrate the successful preparation of electron-transparent single crystal silicon samples after MR polishing and single-sided ion milling. Dimples pre-thinned to less than 30 microns and with little mechanical surface damage were repeatedly produced under optimized MR polishing conditions. Samples pre-thinned by both MR polishing and traditional technique were ion-beam thinned from the rear side until perforation, and then observed by optical microscopy and TEM. The results show that the specimen pre-thinned by MR technique was free from dimpling related defects, which were still residual in sample pre-thinned by conventional technique. Nice high-resolution TEM images could be acquired after MR polishing and one side ion-thinning. MR polishing promises to be an adaptable and efficient method for pre-thinning in preparation of TEM specimens, especially for brittle ceramics.