Suzhou Medical Institute proposes a new method for sensitivity enhancement of uncooled infrared detectors

[ Instrument Network Instrument Development ] The infrared heat detector changes the temperature, electromotive force, and resistivity of the probe material after absorbing infrared radiation, and feedbacks the infrared radiation energy or power of the target according to these changes. In recent years, infrared detectors based on thin-film piezoelectric principle have become one of the research hotspots of infrared heat detectors at home and abroad. These detectors reflect the infrared radiation information by causing the resonant frequency of the sensor to move due to the intrinsic temperature characteristics of the resonant film. Among them, the thin film piezoelectric Lamb wave sensor does not need the physical gap required for capacitive sensor driving, and has the advantages of uncooled, low power consumption, high CMOS process compatibility, etc., and is one of the ideal choices for the current infrared detection core device. However, when the thin film piezoelectric Lamb wave sensor is used for infrared detection, the correlation between infrared radiation and the resonant frequency of the sensor needs to be further studied, aiming to provide a scientific basis for the enhancement of detector performance.

Li Chuanyu and Zhou Lianqun, Laboratory of Suzhou Biomedical Engineering Technology Research Institute, Chinese Academy of Sciences, conducted research on thin film piezoelectric Lamb wave infrared detection technology based on photo-thermal-acoustic effect. Based on the vibration and sensing mechanism of thin film piezoelectric Lamb waves, the researchers established a theoretical model of photo-thermal and thermo-acoustic transformation, and demonstrated the relationship between photo-thermal and thermo-acoustic conversion efficiencies and key physical parameters of the sensor. According to the theoretical and experimental analysis, a new method of enhancing the sensitivity of infrared detection by Lamb wave sensor coating polydopamine (PDA) nanoparticles (PDA-Lamb) was proposed.

The researchers used the zero-order symmetry (S0) mode and the zero-order antisymmetric (A0) mode of the Lamb wave sensor and the A0 mode of the PDA-Lamb as the research object. The three modes respectively generate different frequency shifts before and after the infrared light irradiation, and the sensitivity of the infrared detection is reflected by comparing the relative movement amount of the frequency. The results show that the relative change of the resonant frequency of the PDA-coated Lamb wave sensor (PDA-Lamb) is highly linear with the infrared radiation intensity. The PDA-Lamb is nearly one order of magnitude higher than the uncoated channel. The increase in sensitivity is due to the improvement of the light-to-heat conversion efficiency, and the heat-to-sound conversion efficiency before and after coating is substantially unchanged. This study provides a reference for the design and optimization of high performance thin film piezoelectric acoustic infrared detectors, which will help to apply in the field of infrared therapy.

The research work was funded by the National Natural Science Foundation of China (51675517) and the Jiangsu Excellent Youth Fund (BK20160057). The corresponding research results have been published in Applied Physics Letters (APPL PHYS LETT, 2019, 114(18): 183505). .