363 nm UVA light generation with carbon nanotube electron emitters

Abstract

Mercury-vapor lamps with a wavelength of 365.4 nm are mainly used in photolithography processes as i-line. However, mercury-free ultraviolet (UV) light sources have been actively investigated for mercury environmental and human health hazards, and electron beam (E-beam) pumped UV light sources are one of alternative technologies. E-beam pumped light sources have advantages such as eco-friendlyness, simple fabrication process, and large area. We called electron beam irradiated pumping technology based on carbon nanotube (CNT) emitters as C-beam pumping and used it as an excitation source. The C-beam pumping technique excites electrons in the SrB4O7:Eu anode by high energy electron irradiation and generates UVA light through the relaxation process. The SrB4O7:Eu phosphor was stirred with a binder, followed by spin-coating on a quartz substrate, UV illumination, annealing, and Pt electrode fabrication. Anode was optimized through PL intensity analysis. The optimized annealing process condition is an annealing time of 30 min at 900 °C around the atmosphere, which results in the disappearance of carbon-based binder materials on the quartz substrate, thereby improving the UV properties. The optimized SrB4O7:Eu anode has UVA light with a peak wavelength at 363 nm by applying a bias of 12 kV and a current of 0.5 mA at the anode using the C-beam irradiation pumping technique.