Development of simultaneous single-event time-of-flight Rutherford backscattering spectrometry and elastic recoil detection

Abstract

Simultaneous time-of-flight (ToF) Rutherford backscattering spectrometry (RBS) and elastic recoil detection (ERD) were combined with a focused ion beam to establish a platform for comprehensive three-dimensional elemental visualization. RBS and ERD provide highly sensitivity to heavy and light elements, respectively, and their complementary characteristics enable broader elemental coverage than either technique alone. Large-diameter microchannel plates and the single-event ToF technique were used to improve the energy resolution and detection yield and stability during long-term measurements. A simplified configuration was achieved by precisely adjusting the delays for one start and two stop signals, and individual RBS and ERD measurements were used to optimize the timing conditions required for simultaneous acquisition. During simultaneous ToF-RBS and ToF-ERD measurements, broad peaks appeared in the RBS spectrum at large sample tilt angles required for the ERD geometry. These peaks were attributed to multiple scattering, as supported by numerical calculations. To demonstrate applicability, two- and three-dimensional micrometer-scale samples were analyzed. In the three-dimensional sample, the ToF peaks of In and Sn were slightly delayed compared with those in the two-dimensional sample, confirming that the embedded indium tin oxide (ITO) structures were successfully detected despite their buried structure. Reconstructed maps clearly visualized the island-shaped ITO structures in both samples. These results confirm the successful development of a simultaneous single-event ToF-RBS and ToF-ERD system, enabling non-destructive three-dimensional elemental visualization with nanometer-scale depth resolution and broadly applicable to complex multi-layer or patterned materials.