A Hermetically Sealed Micro Vacuum Ultraviolet Light Source for Detection of VOCs

Abstract

Vacuum ultraviolet (VUV) light sources play a crucial role in volatile organic compounds (VOCs) detection and other analytical applications. In this letter, a hermetically sealed micro-chip with nitrogen-plasma for VUV light source is demonstrated. The designed $\mu $ VUV light source chip is fabricated based on silicon-on-insulator platform and hermetically sealed in a ceramic carrier equipped with a chip-scale MgF2 window for VUV light transmission. To verify device performance, the fabricated $\mu $ VUV light source chip is integrated with a commercial ionization chamber for achieving a micro photoionization detector ( $\mu $ PID). Measurement results illustrate that the reported $\mu $ VUV light source chip can emit VUV light with wavelength as low as 113.72 nm and the constructed $\mu $ PID achieves an ionization energy up to 10.9 eV. It exhibits a superior normalized photoionization efficiency, compared with a commercial PID typically with an ionization energy of 10.6 eV. Furthermore, its leakage rate ( ${1}.{5}\times {10} ^{-{12}}$ atm $\cdot $ cc/s) is three orders of magnitude lower than that of commercial VUV lamps, indicating a significantly extended operational liftime. It offers an innovative solution for high-performance VUV light source in $\mu $ PID, which provides a promising approach for the miniaturization and portability of VOCs detection devices, gas chromatograph and other ionization-based analytical instruments.