Research On Fabrication Of A Flexible SAW Device And Its Performance As Ultraviolet Detectors

Surface acoustic wave(SAW)devices have been widely used in the field of sensing due to their advantages of good stability,high sensitivity,multi-parameter sensitivity,suitability for mass production,and wireless operation.With the development of the Internet of Things,SAW sensors are also developing in the direction of flexibility.In this paper,a flexible SAW device based on ZnO thin film was prepared along with the structure designed.And the performances of RF and UV dectection was studied.In this paper,carbon fibers(CF)were introduced into SAW devices for the first time.On the PI/CF composite substrate,a(0002)preferred orientation ZnO piezoelectric film was deposited by reactive magnetron sputtering,and then through thermal evaporation and photolithography,equal interdigitated electrodes and non-uniform interdigitated electrodes with wavelengths of 64?m,100?m,and 160?m were prepared.The test results of the device's RF characteristics and UV sensing performance show that the larger the design wavelength of the device,the lower the resonant frequency and the lower the UV sensing sensitivity;In addition,the UV detection sensitivity of the equal interdigitated electrode structure is better than the non-uniform interdigitated electrode.ZnO thin film based SAW UV sensor has a temperature frequency coefficient of 365ppm/K and a sensitivity of 56.92(ppm(m W/cm²)^-1 at a wavelength of 64?m and a resonance frequency of 14.6MHz.Through the finite element simulation analysis of the device using Comsol software,we speculate that this UV sensor is works in Rayleigh wave mode.In addition,our SAW device also exhibits the characteristics of electromagnetic metamaterials.The electromagnetic resonance frequency of a device with designed wavelength of 64?m is 4.7 GHz,the sensitivity of ultraviolet sensing at this frequency is38.3(ppm(m W/cm²)^-1.Meanwhile,the same device presented excellent performance on the glucose concentration monitoring when it worked as electromagnetic metamaterial device,giving a sensitivity of 34 MHz/(mg/m L).The flexible SAW device developed in this paper has the potential for multi-functional integration and multiple application scenarios.