Field ion microscopy of W and PtTi at about 1000°C

Bright new images including the image of atoms have been observed when a positive high voltage (～ 15 kV) was applied to a specimen heated to ～ 1000°C in a field ion microscope. A channel plate multiplier was especially effective to this effect. Since those images were observed even in a high vacuum of 10^?7 Torr, where imaging gas hardly exists, and the brightness of the images does not depend on the residual gas pressure, they can not be the usual images caused by gas ions emitted from the tip of the specimen. A tentative interpretation is that they are caused by metal gas ions which are vaporized from the heating loop of tungsten and ionized at the tip of the specimen.