We have developed a new nano-beam time-of-flight secondary neutral mass spectrometry system: laser ionization mass nanoscope or LIMAS. The primary ion beam column was equipped with a Ga liquid metal ion source and aberration correction optics. The primary ion beam was down to 40 nm in diameter under a current of 100 pA with an energy of 20 keV. The sputtered particles were post-ionized under non-resonance mode by a femtosecond laser. The post-ionized ions were introduced into a multi-turn mass spectrometer. A mass resolution of up to 40 000 was achieved. The vacuum of the sample chamber was maintained under an ultrahigh vacuum of 2 Â 10 À8 Pa. This instrument would be effective for ultrahigh sensitive analysis of nanosized particles such as return samples from asteroids, comets, and planets.

Laser ionization mass nanoscope is a time-of-flight sputtered neutral mass spectrometer associated with laser post-ionization by tunneling effect. A spherical and chromatic aberration corrector is installed in the primary ion column. The lateral spatial resolving power of He imaging of solid surface has been evaluated by scanning image using a probe diameter of 90 nm from crater edge slope of a He ion-implanted Si substrate. Helium distribution from the scanning image is quantitatively equivalent with depth profiling analysis from surface of the same substrate, indicating that spatial resolving power of 20 nm for depth resolution has been achieved on the He scanning image through use of oblique incident effect of the primary beam.

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A chromatic and spherical aberration corrector with liquid Ga ion metal source was developed. The aberration corrector reduced the ion probe diameter to ~1.5 times smaller for the 69 Ga + beam in aberration correction mode compared with the corrector in non-aberration correction mode. The probe current at a given probe size is approximately two times larger in aberration correction mode than in non-aberration correction mode. The aberration-corrected focused ion beam yields higher lateral resolutions and higher sensitivities with lower acceleration voltage for the same acquisition time down to 10 nm with a current of 1 pA.

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.