A triode-type carbon nanotube ionizer for micro mass spectrometer

Abstract

This article presents an ionizer based on a triode structure for a micromachined time-of-flight mass spectrometer (TOFMS). The fabricated device has two components in one chip: a triode-type field emitter for ionization and an ion separator with acceleration electrodes. The electron emitter is an array of carbon-nanotube (CNT) pillars grown by hot-filament chemical vapor deposition (HFCVD). The anode current measured in the field-emission characteristic test of the fabricated device is high, up to 72.1 µA. The gate current is about 5% of the anode current, which implies low electron interception. We confirmed the ionization by electron impact and obtained the mass spectrum of the air from the fabricated device using a microchannel plate (MCP). The results show that the fabricated TOFMS is feasible for cheap miniature mass spectral analyzers.