Far ultraviolet C
(UVC) light sources have the potential for numerous
applications ranging from sterilization, purification, sensing, deodorization,
surface modification, and so on. In particular, a short wavelength
of far UVC is effective at sterilizing viruses and bacteria by minimizing
damage to mammalian skin. Recently, many researchers are devoting
materials and alternative light sources to overcome low efficiency,
small light-emitting area, UV absorption, and complicated manufacturing
processes of far UVC generation. Here, the sapphire wafer is evaluated
for far UVC light generation using electron beam irradiation with
carbon nanotube (CNT) emitters. A CNT-based cold cathode electron
beam (C-beam) that emits electrons and accelerated onto κ-Al2O3 of the sapphire wafer was used as an excitation
source to demonstrate high-power far UVC light generation. High-efficiency
226 nm far UVC is made with a power conversion efficiency of 0.87%
and a light-emitting area of 960 mm2. Far UVC generation
depends on the input power and the crystallinity of sapphire wafers.
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.
Large area deep ultraviolet (DUV) light is generated by carbon nanotube (CNT) cold cathode electron beam (C-beam) irradiation on Al0.47Ga0.53N/Al0.56Ga0.44N multi quantum wells (MQWs) anode. We developed areal electron beam (EB) with CNT cold cathode emitters. The CNT emitters on silicon wafer were deposited with an area of 188 mm2, and these were vertically aligned and had conical structures. We optimized the C-beam irradiation conditions to effectively excite AlGaN MQWs. When AlGaN MQWs were excited using an anode voltage of 3 kV and an anode current of 0.8 mA, DUV with a wavelength of 278.7 nm was generated in a large area of 303 mm2. This DUV area is more than 11 times larger than the light emitting area of conventional EB pumped light sources and UV-LEDs.
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