Direct excitation of xenon by ballistic electrons emitted from nanocrystalline‐silicon planar cathode and vacuum‐ultraviolet light emission

Abstract

Abstract— To verify the possible use of energetic electrons for direct excitation of inert gas molecules, a nanocrystalline‐silicon (nc‐Si) planar ballistic emitter is operated in a high‐pressure xenon gas ambience. Under the pulse drive, vacuum‐ultraviolet (VUV) light emission is detected without any signs of discharge. The transient behavior of the VUV light emission properly corresponds to that of the nc‐Si emitter. In accordance with quantitative analyses of electron‐emission characteristics and the VUV output, the electron‐to‐photon conversion efficiency reaches 81% in the relatively efficient emitter case. The VUV output power is mainly determined from the number of electrons with energies compatible the with internal excitation of xenon. The emission spectrum observed at a pressure of 10 kPa shows peaks at 152 and 172 nm, which are thought to be originated from metastable Xe2* states. In contrast to the case of conventional impact ionization, no near‐infrared (NIR) peaks are seen in the spectrum. These results strongly suggest that the incidence of energetic electrons causes direct excitation of xenon molecules followed by radiative relaxation through intermediate states. The generated VUV light can be easily converted to visible light using a phosphor screen. As a discharge‐free VUV light emission, this phenomenon is potentially applicable to mercury‐free, high‐efficacy, and high‐stability flat‐panel light‐emitting device.