Fabrication of two types of micro ion sources for a micro time-of-flight mass spectrometer

Abstract

This paper reports the fabrication of two types of micro ion sources for a micro time-of-flight mass spectrometer (TOFMS). The TOFMS is an analyzer that serves for the establishment of molecular weight by using the difference in the flight time of ions according to their mass-to-charge values. The micro TOFMS consists of a glass substrate with several nickel electrodes and a silicon substrate with an ion source. We have fabricated two types of ion sources using a hot filament and field emitters with a carbon nanoparticle structure. The overall size of the assembled device is 10 × 10 × 1 mm3. The hot filament is fabricated through the nickel electroplating process and some lithography processes. The carbon nanoparticle layer is grown by hot-filament chemical vapor deposition (HFCVD). The carbon nanoparticle field emitter has the triode structure with which we can control the emission current at low voltage. The maximum emission current of the hot-filament ion source is 0.28 μA. The emission current of the field emission ion source can be controlled from 0 to 18.5 μA when the gate voltage varies from 0 to 175 V.