Submicron Ion Probes

An increased interest in developing focused ion beams has arisen in recent years. This was motivated by a great success of liquid metal ion (LMI) source technology. Primary experiments with this type of source originated in the 1960’s. Mahoney et al.[1] used a capillary emitter to obtain ion emissions of cesium, although their purpose was in an ion thruster. For a similar purpose Bailey[2] built an ion emitter which is thought to be an original model of the present LMI sources. Evans and Hendricks[3] used an alloy type LMI source of Ga-In as an ion source for mass spectrometry. Krohn and Ringo[4] built a focusing system, using an electrostatic einzel lens with a Ga source. Prewett and Jefferies[5] developed ion sources consisting of a capillary and a needle, which are almost the same configuration as that of Bailey’s. Seliger et al.[7] originally realized an ion probe of less than 1 micron in diameter, using a Ga ion source made by Clampitt’s group. Emission characteristics of LMI sources were intensively studied by Swanson et al.[8].