Conventional triode ionization gauge with carbon nanotube cold electron emitter

Abstract

The authors presented a conventional triode ionization gauge with a linear-type carbon nanotube cold electron emitter, which was made by painting technology on a nickel wire. The gauge used the ratio of the ion current to the electron current to indicate the vacuum. Although there was fluctuation in the cathode’s emission current, the ratio of the ion current to the electron current kept stable with a variation of about ±10% in each pressure decade from 10−7to10−3torr. The gauge showed good measurement linearity in the vacuum range from 10−6to10−3torr.

A Cylindrical Triode Ultrahigh Vacuum Ionization Gauge with a Carbon Nanotube Cathode

“…This is mainly due to the fact that the X-rays mainly produced by electron-impact on the anode generate a photoelectron current from the ion collector, and thus produce a pressureindependent background current. This background current, in reality, is comparable to or even larger than the ion current originating from ionizing gas molecules in extremely high even ultrahigh vacuum pressure regions; consequently, a nonlinear characteristic in normalized ion current-pressure plots is generally observed in hot cathode ionization, as widely reported in previous studies [18,37,38]. In order to suppress the adverse impact of X-ray effects in very low pressure measurements, some measures (i.e., reducing the collector area, locating the collector out of the line of sight of the gauge grid and the filament, adding a suppresser electrode, and utilizing a current modulation technique) were employed to extend the lower limit of pressure measurements of the ionization gauge [6,35,39]; however, to date, the results have not been satisfactory.…”

“…For ionization gaugse, a low anode current (i.e., 20 μA) would greatly reduce the adverse impact of X-ray effects [ 12 , 18 , 35 ] in extremely low pressure measurements, even if it would cause difficulties due to weak collector current detection [ 7 , 8 ]. Thus, the metrological behaviors of the modified ionization gauge with a CNT electron source were investigated under a low anode current together with constant electrode voltages, as demonstrated in Figure 1 b.…”

“…Likewise, in Ref. [ 18 ], the lower limit achieved by BAG with a CNT cathode was approximately 1 × 10 −4 Pa; the value for the hot BAG cathode was about 1 × 10 −9 Pa. In this sense, the advantages of the application of such novel CNT field emission cathodes in extremely low pressure measurements have not yet been fully demonstrated.…”

“…However, conventional ionization gauges have long-standing intractable problems when measuring extremely low pressure, i.e., X-ray effects, electron-stimulated desorption effects, and outgassing effects [ 1 , 6 , 7 ]. Fortunately, recent studies [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ] have shown that ionization gauges with carbon nanotube (CNT) cathodes have unique advantages, such as low power consumption for electron emissions, fast responses, free from visible to infrared light radiation and thermal radiation, etc., in extremely low pressure measurements, which are largely due to the application of the novel CNT field emission cathode. For instance, Murakami et al [ 9 ] reported the application of a CNT field emission cathode in a Bayard–Alpert gauge (BAG) for the first time in 2001, and the lower limit of pressure measurement by this novel sensor was approximately 1 × 10 −4 Pa. Dong et al [ 8 ] reported on the design and investigation of a commercial extractor gauge (Leybold, IE 514) with a CNT cathode, which showed excellent measurement linearity from 10 −10 to 10 −6 Torr in nitrogen.…”

Fabrication Process and Electro-Thermal Modeling for the Cathode of the CMOS-Compatible Hot-Filament Vacuum Gauge

“…The micro tungsten resistor fabricated by tungsten film deposition and etching process is used as the cathode for the vacuum gauge [3,4]. Their measurement range can reach 10 -3 Pa. Also, the nanotube is introduced as the material for cathode to decrease the power consumption and the dimension [5,6]. All of these researches decrease the dimension of the gauge to some extent.…”