To make the specific features of nanocrystalline silicon (nc-Si) cold cathode clear, its emission characteristics are investigated in low vacuum and atmospheric pressure. The experimental nc-Si diode is composed of a thin Au film, a nanocrystallized polysilicon layer, an n-type silicon wafer, and a back contact. It is shown that the ballistic electron emission mode of the nc-Si device is kept alive until the vacuum pressure is increased to about 10Pa, and that a significant current signal is detected at the collector even in air. The current observed in air can be interpreted as a result of energetic electron attachment into oxygen molecules in proximity to the front surface. The effectiveness of this emitter for the use in air is applied to surface charging of an insulating polymer. The experimental results demonstrate that the surface of a polymer film located in air at a distance of 1mm from the device surface is quickly charged up to a certain negative potential determined from the collector voltage. The surface-emitting nc-Si ballistic emitter is useful not only in vacuum, but also in air and gas ambient for various applications.

Drift tube ion mobility spectrometry with a novel atmospheric electron emission (AEE) source was developed for determination of gaseous and blister chemical warfare agents (CWAs) in negative mode. The AEE source was fabricated from an aluminum substrate electrode covered with 1 μm silver nanoparticle-dispersed silicone resin and a thin gold layer. This structure enabled stable tunneling electron emission upon the application of more than 11 V potential under atmospheric pressure. The reactant ion peak (RIP) was observed for the reduced mobility constant (K 0) of 2.18 and optimized at the charging voltage of 20 V. This RIP was assigned to O2 – by using a mass spectrometer. Hydrogen cyanide was detected as a peak (K 0 = 2.47) that was discriminatively separated from the RIP (resolution = 1.4), with a limit of detection (LOD) of 0.057 mg/m3, and assigned to CN– and OCN–. Phosgene was detected as a peak (K 0 = 2.36; resolution = 1.2; and LOD = 0.6 mg/m3), which was assigned to Cl–. Lewisite 1 was detected as two peaks (K 0 = 1.68 and 1.34; LOD = 12 and 15 mg/m3). The K 0 = 1.68 peak was ascribed to a mixture of adducts of molecules or the product of hydrolysis with oxygen or chloride. Cyanogen chloride, chlorine, and sulfur mustard were also well detected. The detection performance with the AEE source was compared with those under corona discharge and 63Ni ionizations. The advantage of the AEE source is the simple RIP pattern (only O2 –), and the characteristic marker ions contribute to the discriminative CWAs detection.

We developed herein an original electron emission device that can stably operate in the atmosphere. The important features of the device are that the energy of electrons is as extremely small as several eV, the emission current in the atmosphere is as large as several μA/cm2, and the durability is of several hundred hours. These characteristics are obtained by an original device structure based on a 1 μm-thick Ag nanoparticle/polymer composite layer. The electron emission device does not require a strong electric field in the space between the emitter and the collector as required for discharge or plasma. The physical mechanism of electron emission is a mixture of field emission according to the Fowler–Nordheim plot and electron emission caused by breakdown. The energy of the emitted electrons depends on the applied voltage and can be controlled. The electrons emitted from the device can generate various ions and radicals.

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