Plan-view sample preparation of a buried nanodots array by FIB with accurate EDS positioning in thickness direction

Chaorong Zhong; Lina Lin; Ruijuan Qi; Yan Cheng; Xingsen Gao; Rong Huang

doi:10.1016/j.ultramic.2019.112840

Plan-view sample preparation of a buried nanodots array by FIB with accurate EDS positioning in thickness direction

Ultramicroscopy. 2019 Dec:207:112840. doi: 10.1016/j.ultramic.2019.112840. Epub 2019 Sep 3.

Authors

Chaorong Zhong¹, Lina Lin², Ruijuan Qi², Yan Cheng², Xingsen Gao³, Rong Huang⁴

Affiliations

¹ Key Laboratory of Polar Materials and Devices (MOE) and Department of Electronics, East China Normal University, Shanghai 200062, China; School of Physics and Telecommunication Engineering, Yulin Normal University, Yulin, Guangxi 537000, China.
² Key Laboratory of Polar Materials and Devices (MOE) and Department of Electronics, East China Normal University, Shanghai 200062, China.
³ Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006, China.
⁴ Key Laboratory of Polar Materials and Devices (MOE) and Department of Electronics, East China Normal University, Shanghai 200062, China; Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China. Electronic address: rhuang@ee.ecnu.edu.cn.

PMID: 31505397
DOI: 10.1016/j.ultramic.2019.112840

Abstract

Recently, there are growing demands on focus ion beam (FIB) sample preparation technique in plan-view geometry because it can provide the in-plane microstructure information of thin film and allows direct correlations of the atomic structure via transmission electron microscopy with micrometer-scale property measurements. However, one main technical difficulty is to position the buried thin film accurately in a sandwich structure. In this paper, an on-line positioning method based on the thickness monitoring by EDS is introduced, where the intensities of the characteristic X-ray peaks from different layers are proportional to the relative thickness of them at the same acquisition conditions. A high density array of ∼100 nm squares BiFeO₃ nanodots with ∼ 25 nm thickness grown on a 20 nm thick SrRuO₃ bottom electrode and (001)-oriented SrTiO₃ substrate is selected for demonstration. By monitoring the intensities of Pt-M, Sr-L, Ti-K, Ru-L, Fe-K and Bi-M peaks, the relative thickness of Pt protection layer, the BiFeO₃, SrRuO₃ and SrTiO₃ can be obtained, which provide accurate position of the BFO nanodots array in the thickness direction. With these information, the cutting parameters are optimized and a high quality plan-view specimen of BFO nanodots array is prepared, which is confirmed by high resolution transmission electron microscopy. This positioning method should have a wide application for material science.

Keywords: EDS; FIB; Plan-view sample preparation; Positioning; Thickness monitoring.