Tatsuo Iwata

Real-time measurement of vacuum pressure by field emission microscopy

Abstract A method for real-time measurement of ultra-high vacuum (UHV) or lower vacuum has been developed by field emission microscopy with tungsten and rhenium tips. Two different methods of pressure measurement were examined: (1) In the first method, the pressure P is determined with the equation P α d log I /d t under a constant applied voltage, where I is the emission current. (2) In the second method, the pressure is determined from P α (d V /d t )/ V 2 with a constant emission current, where V is the applied voltage to keep the emission current constant.

A quantitative estimation of the sensitivity of field-emission pressure-gauge

The sensitivity of field-emission pressure-gauge was studied from both theoretical and experimental aspects. The focus of the study was to find new operation modes which can allow real-time measurements of the vacuum pressure. The sensitivity S=7.1×103Pa−1s−1 (N2 equivalent) was experimentally determined for the residual gas of ion-pumped systems. For hydrogen, it was found that the sensitivity is mainly determined by the product of the dipole moment and the sticking probability of the adsorption system. Some possible effects attributed to electric fields required for field emission were considered and examined. It was concluded that under the usual operating field there was no significant effect on the sensitivity of the field-emission pressure-gauge.

Field-emission characteristics from carbon nanotube field emitter arrays (CNT FEAs) grown on silicon emitters

In this study, the relationship between fluctuation of the emission current and the number of active carbon nanotube emitters is discussed, and also the effect of gas adsorption on the emission characteristics is investigated.