Development of a compact FE-SEM and X-ray microscope with a carbon nanotube electron source

Abstract

A carbon nanotube (CNT) possesses various benefits as a field electron emitter. Multi-walled CNT (MWNT) have exhibited high brightness and the field emission (FE) current is stable even under poor high-vacuum condition of 10−6 – 10−7 Pa without ion pumping. In this study, we have experimentally manufactured a compact composite field emission scanning electron microscope (FE-SEM) and X-ray microscope (XRM) with a single isolated MWNT electron source. An electron beam from a MWNT was focussed and accelerated by a Butler electrostatic lens. Stable SEM images were observed at a Butler voltage Vbut = 1.5 kV and accelerating voltage Vacc ≃ 15 kV with a focussed probe current Ifoc = 61 pA. The spatial resolution of the SEM, which was estimated from 80 – 20 % edge profile of polystyrene latex spheres, was about 9 nm. XRM images were acquired by 30-min exposure at Vbut = 1.5 kV and Vacc ≃ 17 kV. A spatial resolution of about 200 nm was obtained for XRM. The present results prove the high performance of the compact FE-SEM and XRM using a single isolated MWNT electron source at 10–7 Pa.