The NanoSIMS-HR:\nThe Next Generation of High Spatial\nResolution Dynamic SIMS

The\nhigh lateral resolution and sensitivity of the NanoSIMS 50\nand 50L series of dynamic SIMS instruments have enabled numerous scientific\nadvances over the past 25 years. Here, we report on the NanoSIMS-HR,\nthe first major upgrade to the series, and analytical tests in a suite\nof sample types, including an aluminum sample containing silicon crystals,\nmicroalgae, and plant roots colonized with a symbiotic fungus. Significant\nimprovements have been made in the Cs<sup>+</sup> ion source, high\nvoltage (HV) control, stage reproducibility, and other aspects of\nthe instrument that affect performance. The modified design of the\nNanoSIMS-HR thermal-ionization Cs<sup>+</sup> source enables a 5 pA\nprimary ion beam to be focused into a 100 nm spot, a ∼2.5-fold\nincrease compared to Cs<sup>+</sup> sources on previous instruments\n(∼2 pA at 100 nm). The brightness of the new Cs<sup>+</sup> source enables an ultimate lateral resolution as high as 30 nm and\nimproved detection limits for a given analysis area. Sample stage\nmovement accuracy is higher than 500 nm, enabling many-fold higher\nthroughput automated analyses. With the new HV control, the primary\nion beam impact energy can be reduced from 16 to 2 keV, which enables\nhigher depth resolution during depth profiling (a 2-fold improvement),\nalbeit with a 5-fold decrease in lateral resolution. In the NanoSIMS-HR,\nthe secondary ion column and detection system are identical to those\nused in the previous series, and the isotopic analysis performance\nis as precise as in previous NanoSIMS instruments.