Sapphire Wafer for 226 nm Far UVC Generation with Carbon Nanotube-Based Cold Cathode Electron Beam (C-Beam) Irradiation

Abstract

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.

Solid‐State Far‐Ultraviolet C Light Sources for the Disinfection of Pathogenic Microorganisms Using Graphene Nanostructure Field Emitters

“…Electron beam (EB)-pumped far-UVC light sources have been explored as a promising alternative to avoid these problems. Several groups have reported EB-pumped far-UVC light sources based on wide-bandgap materials, such as hexagonal boron nitride powder, [30] κ-Al 2 O 3 crystals [31,32] and ultrathin GaN/AlN multiple quantum wells. [33,34] Among these reports, a study by Oto et al [35] has attracted special interest regarding the possibility of EB-pumped AlGaN quantum wells because the UV emission at the peak wavelength below 240 nm was obtained with a high output power of 100 mW and a high power efficiency exceeding 40%.…”

“…Electron beam (EB)‐pumped far‐UVC light sources have been explored as a promising alternative to avoid these problems. Several groups have reported EB‐pumped far‐UVC light sources based on wide‐bandgap materials, such as hexagonal boron nitride powder, [ 30 ] κ‐Al 2 O 3 crystals [ 31 , 32 ] and ultrathin GaN/AlN multiple quantum wells. [ 33 , 34 ] Among these reports, a study by Oto et al.…”

Extreme Ultraviolet Lighting Using Carbon Nanotube-Based Cold Cathode Electron Beam

“…FE is known for its advantages such as fast switch-on time, compact size, high emission current density and resistance to temperature fluctuations [ 5 , 6 , 7 ]. The electrons emitted by the FE can be used in a variety of vacuum electronic devices, such as scanning electron microscopy (SEM) for high-resolution imaging [ 8 ], microwave amplifiers [ 9 ], compact X-ray sources with fast switching [ 10 ], flat panel displays [ 11 ], and UV light sources [ 12 , 13 ]. To improve the FE properties, the work function of the emitter material should be lowered, and the tip of the emitter sharpened to increase the field enhancement factor.…”

“…They have excellent electrical, mechanical, chemical, and structural properties [ 6 , 7 ]. Because of its extraordinary properties, CNTs have many applications [ 8 , 9 , 10 , 11 , 12 , 14 , 15 , 16 ]. CNTs are synthesized using arc discharge, laser ablation, chemical vapor deposition (CVD), and plasma enhanced chemical vapor deposition (PECVD) [ 15 , 16 ].…”

Optimized Aluminum Reflector for Enhancement of UVC Cathodoluminescence Based-AlGaN Materials with Carbon Nanotube Field Emitters

“…This inefficiency is for different reasons and is related to the quality of the nitride material with high aluminum (Al) composition and/or the technology employed for fabricating the diodes, where low external quantum efficiency is observed. One of the issues concerns the deepening of the Mg-acceptor level, which would make it difficult to deposit the high-conductivity p-type layer [ 7 , 8 , 9 , 10 ]. In addition, the poor structural quality of the AlGaN epitaxial layers would cause dislocations and create non-radiative defects that destroy the internal quantum efficiency of the LEDs [ 11 , 12 , 13 , 14 , 15 ].…”