IOP PUBLISHING JOURNAL OF MICROMECHANICS AND MICROENGINEERING J. Micromech. Microeng. 17 (2007) 1542–1548 doi:10.1088/0960-1317/17/8/017 Fabrication of two types of micro ion sources for a micro time-of-flight mass spectrometer Hyeun Joong Yoon 1 , Seong Ho Song 1 , Nguyen Tuan Hong 2 , Kwang Woo Jung 3 , Soonil Lee 2 and Sang Sik Yang 1 1 Division of Electrical & Computer Engineering, Ajou University, Suwon, 443-749, Korea 2 Department of Physics, Ajou University, Suwon, 443-749, Korea 3 Division of Bio-Nano Chemistry, Wonkwang University, Iksan, 570-749, Korea E-mail: ssyang@ajou.ac.kr Received 17 April 2007, in final form 7 June 2007 Published 5 July 2007 Online at stacks.iop.org/JMM/17/1542 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 mm 3 . 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. (Some figures in this article are in colour only in the electronic version) 1. Introduction The role of analyzers becomes more important with the development of various fields such as chemistry, physics, biology, pharmacology, geology and environmental science. Especially, a mass spectrometer is one of the most important analytical instruments for the analysis of a wide variety of samples. Mass spectrometers can identify all the atoms and molecules that include gases, liquids and solids. It can correlate the spectrum and structure of a compound and identify its chemical bonds [1, 2]. Conventional mass spectrometers are large and very expensive. Moreover, they require large amounts of power to operate. To overcome these disadvantages, some researchers have investigated miniature mass spectrometers. Tuszewski has developed a miniature magnetic field mass spectrometer [3]. Applied voltages are less than 100 V and an average magnetic field is up to 0.28 T. This mass spectrometer is adequate for plasma applications. Diaz et al have developed a sub-miniature double-focusing magnetic field mass spectrometer with a 90 ◦ cylindrical crossed electric and magnetic sector-field analyzer with a radius of 2 cm [4]. It weighs 0.8 kg, and its power consumption is 2.5 W. Orient et al have proposed a miniature quadrupole mass spectrometer [5]. It consists of 16 rods in a 4 × 4 array to form nine separate quadrupolar regions. In another case, Geear et al have developed a quadrupole mass spectrometer with microelectromechanical systems (MEMS) technology [6]. The quadrupole mass filter is fabricated by deep silicon etch and lithography. Aside from these mass spectrometers, there is a micromachined Wien filter-type mass spectrometer [7] and a portable ion trap mass spectrometer [8]. In particular, 0960-1317/07/081542+07$30.00 © 2007 IOP Publishing Ltd Printed in the UK 1542