Research On Heat Flow Sensors Based On Thin Film Transverse Thermoelectric Effect And Thin Film Temperature Detectors

In recent years,with the development of semiconductor materials and their electronic devices,various semiconductor devices have not only greatly facilitated people’s production life,but also played an increasingly important role in the military field.In particular,applications in laser detection and analysis,temperature measurement,thermal fluid measurement and thermal imaging and other related fields are highly favoured.conventional conventional thermoelectric material devices are well known to the general public,while relatively little research has been carried out on the preparation of transverse thermoelectric material devices.YBa2Cu3O7-δ(YBCO)and Ca3Co4O9(CCO)materials are suitable as transverse thermoelectric materials for the fabrication.In order to further investigate the performance of the thermoelectric films,we have prepared good performance YBCO and CCO lateral thermoelectric films on tilted-angle substrates for further prototyping and testing of an Atomic layer thermopile(ALTP)passive heat flow detector.In order to improve the measurement accuracy and range of the sensor,this research explores the Pt thin film resistance temperature sensor(RTD)with the aim of integrating it with an ALTP detector to form a composite sensor with better overall performance.Although RTD devices have been extensively researched,the TCR(Temperature Coefficient of Resistance)of most reported Pt thin film RTDs is still below 3.0 × 10-3/℃ at room temperature,which does not meet international standards and is not conducive to ambient temperature monitoring.In this study,the comprehensive performance of the RTD is investigated based on the annealing temperature,annealing time,the addition of buffer layers and the choice of substrate.The basis is laid for further integration with the ALTP heat flow detector to form a composite sensor.The specific studies are as follows:(1)YBa2Cu3O7-δ and Ca3Co4O9 epitaxial films were systematically grown on single crystal substrates with different tilt angles using pulsed laser deposition(PLD)technique.A combination of XRD characterisation,TEM and observation of the microstructure at different stages of growth was carried out.The ALTP passive heat flow sensor was further fabricated using the c-axis tilted YBa2Cu3O7-δ and Ca3Co4O9 epitaxial films as the core sensitive elements.The response rate of the YBa2Cu3O7-δ device with a tilt angle of 5° was 0.408 Vcm2mJ-1 after pulsed laser irradiation(λ～532 nm)and energy density(4.71 mJ cm-2),which exceeded the response rate of the same type of device known in China.(2)The effect of the buffer layer,different annealing temperatures,and different annealing times on Pt RTDs was investigated by growing a patterned platinum layer on the substrate by RF magnetron sputtering and annealing in air.By comparing the effects of annealing temperature(700,800 and 900℃)and annealing time(1,3,10 and 60 min)on TCR,the physical mechanism of its influence on RTD devices was analysed.the TCR coefficient increased with increasing annealing temperature,and a trend of rising and then decreasing occurred with increasing annealing time,especially at 900℃ annealing time of 3 min,The maximum TCR factor for platinum films is 3.2 × 10-3/℃.The effect of annealing time on TCR is also revealed,as too long annealing time(e.g.60 min)will lead to significant diffusion and oxidation of the buffer layer,which will affect the use of the device;short annealing times allow the RTD to withstand higher annealing temperatures(e.g.900℃),which can fully expand the grain size and sufficiently reduce defects.Comparing thin-film temperature sensors grown on different substrates,the temperature sensors grown on LaAlO3 substrates achieve a TCR factor of 3.4 x 10-3/℃ and those grown on flexible polyimide substrates achieve a TCR factor of 3.36× 10-3/℃.