Deep-ultraviolet light source with a carbon nanotube cold-cathode electron beam

Deep-ultraviolet (UV) light is widely used in many industries including medicine because it has sufficient energy to kill viruses and bacteria. However, deep UV with a wavelength of 254 nm can damage human cells, so it is necessary to develop a deep-UV light source with a shorter wavelength to minimize the damage to human cells while still killing viruses. The authors used a carbon nanotube-based cold-cathode electron beam (C-beam) and wide-bandgap anode to fabricate a deep-UV light source with an emission wavelength below 250 nm. The anode was fabricated by annealing ZnO ink on a Si wafer; deep UV with a wavelength of 247 nm and full width at half maximum of 23 nm was obtained. In the case of C-beam irradiation of an anode fabricated on a quartz substrate, deep UV with wavelengths of 208, 226, and 244 nm was generated through excitation with a beam energy of 7 kV and beam currents of 0.3 and 0.5 mA.