Preparation And Performance Study On The Wide Spectrum Pyroelectric Detector

Pyroelectric detectors,comparing with the other detectors,exhibit the advangtages of widely and lower price,small volume,light weight,working in room temperature.Recent years,it has been broadly applied in the military,civil,environmental protection,medical and many other fields.Conseque ntly,the preparation of high-performance pyroelectric detectors is of greatly significance for C hina's national economy and security.In this paper,according to the cutting-edge development of the room temperature pyroelectric detector,we have fully devoted ourselves to develop the pyroelectric detector on ultra-thin lithium tantalate chip by optimizing the unit and structure of detectors,preparing the absorption materials and whole devices.The fabricated unit device of pyroelectric detector could detect infrared and terahertz radiation in room-temperature ambient under the excitation of blackbody or terahertz source.The main targets and the corresponding research results of this paper can be summarized as the following five parts:1.Structural designing and simulation of pyroelectric detectorAfter optimizing the thermodynamic structure of the pyroelectric detector,the optical absorption film system based on lithium tantalate pyroelectric detector is constructed,the radiation absorption rate of each unit by the sensitive element has been improved.Comparing to conventional pyroelectric detectors,we used a support column structure to achieve better thermal insulation performance.Then we added a layer of metal film on the top of the unit sensitive element structure as an absorbing layer for radiation,which is absorbed by the resistance loss of the thin metal layer.Also,we increased the surface area of the unit,thus the ratio of radiation absorbed increased by the ratio of high surface to volume of the metal film.We have designed four standing columns for supporting the unit of detector.Next we established and simulated its model to study the stress,deformation and temperature rise of the sensitive element structure by using the finite element analysis method.Simulation results showed that the seven-layer coated structure of the sensitive absorption layer had a good temperature rise curve in infrared and terahertz band s by that the sensitive element size is 1.2×1.2mm² and the bridge leg width is 150×150?m².The center deformation of sensitive unit reached the smallest value and the mechanical properties was the best when the residual stress value of lithium tantalate wafer was+50MPa.Meanwhile,the simulated result of optimizing the film structure of the unit detector showed that the radiation absorption sensitivity of the cell structure could be maximized by adjusting the thickness?sheet resistance?and conductivity of the metal absorbing film.2.Preparation of pyroelectric detector structureWe have ensured a preparation process of seven-layer structure by IntelliSuite software designing,and then fabricated the seven-layer structure unit based on lithium tantalate wafers by microelectromechanical systems.We used the support column with better insulating properties,in order to improve the response rate.As for the preparation,we used silicon substrate which one side of the surface was sputtered Au film.The other side was coated with synthetic resin,and used the femtosecond laser to prepare the support column then added another sputtering Au films.The organic column pillars were the main pathways to dissipate heat,and the thermal conductivity of the column was controlled by controlling the Au layer resistance.3.Preparation of pyrolysis sensitive materialsWe proposed a thinning method of mechanical grinding and polishing,and chemical corrosion for lithium tantalate wafer.At last,we used the wet etching solution by the corrosion solvent of on H₂O₂ and KOH to obtained a 10?m thin film of lithium tantalate with a low-roughness flat surface.The tested result of the pyrolysis coefficient of 10?m crystal flakes was p=1.81×10^-4C/Km².4.Study of wide spectral absorption filmsWe used N iCr nano-metallic film as the radiation absorbing layer.By optimizing the thickness of NiCr film,the maximized absorption of the infrared and terahertz radiation can be achieved.After a chemical etching process,N iCr film surface was roughened significantly and the effective absorption area increased,forming an absorption-enhanced membrane structure.Meanwhile,after a chemical etching process,the prepared N iCr film with smaller thickness and high reflectivity could be presented an effectively enhanced performance of infrared and terahertz radiation absorption.5.Performance test of pyroelectric detectorWe encapsulated the prepared pyroelectric unit detector,built a unit-device test platform,and completely measured the device performance.The sources we choosed in the infrared band and the terahertz band for the device were blackbody and high power terahertz laser.We got the voltage response rate,noise,NEP and detection rate of the detector after testing the noise and response characteristics.The results showed that the noise equivalent power?NEP?has reached the value of 0.776×10^-10W/Hz^1/2 in the infrared band,the detection rate is 1.55×10⁹cmHz^1/2/W at 10Hz modulation frequency.Under the radiation of the source fixed at 2.56 THz,the NEP was 1.34×10^-10W/Hz^1/2,and the detection rate is 8.97×10⁸cmHz^1/2/W at 10Hz modulation frequency.As for the electrical response time of current pyroelectric detector,it was 1.16ms.