Preparation Of Heat Flow Sensitive Film With Perovskite Structure By MOCVD

Atomic layer thermopile（ALTP）heat flux sensor is based on the transverse Seebeck effect of thermoelectric anisotropic conductive films.Compared with the traditional heat flux sensor,the small volume,simple structure,fast response speed,and high sensitivity also has certain advantages.But mainly subject to material and preparation process limitation,the complicated preparation technology and the flexibility,its large-scale application has not been realized.This dissertation uses a self-built metal-organic chemical vapor deposition system（MOCVD）,based on the mature high temperature superconducting（HTS）oxide YBa₂Cu₃O_7-δ（YBCO）preparation technology in our laboratory.YBCO and the thermoelectric anisotropic film of colossal magnetoresistance（CMR）material La _XCa_1-XMn O₃（LCMO）with good stability in high temperature environment and the preparation process on tilted-MgO-buffered flexible substrate were studied.Furtherly,the thermoelectric sensing performance of ALTP heat flux sensor was calibrated and tested.The specific research content is as follows:1.The mature MOCVD preparation process of YBCO film on vertically oriented substrate was verified.And then the deposition of LCMO film on the same substrate was studied.For YBCO,when the tape heating current is 23.5 A,the film has a pure c-axis orientation.If the heating current is too high or too low,the film will be precipitated or grow incompletely along the c-axis.For LCMO film,the normal c-axis orientation can be achieved when the tape heating current is 27 A,and the full width at half maximum（FWHM）of in-plane and out-of-plane X-ray diffraction peaks of LCMO film are 2.83°and 1.52°respectively.2.On the basis of the preparation process of vertically oriented substrate,the fabrication process of YBCO and LCMO atomic layer ALTP film was studied by MOCVD process using the tilted-MgO-buffered flexible substrate.It was found that compared with the vertically oriented substrate,the heating current for YBCO film were significantly reduced to 20 A,while the heating current for LCMO film were still maintained at about 27 A.In addition,in order to further study the optimal growth and preparation parameters of LCMO film,the Ca doping ratio,Mn source content,liquid feeding rate,oxygen flux,etc.It was found that when the heating current being at 27 A,Ca doping ratio being about 60%,and Mn/（La+Ca）being 1.When the oxygen flux is 1050 sccm,the prepared LCMO film can basically inherit the zigzag structure of the tilting-oriented substrate,and the FWHM of in-plane X-ray diffraction peaks is 7.78°and that of out-of-plane X-ray diffraction peaks is 2.95°.3.Laser-induced voltage test was performed on the prepared YBCO film and LCMO film respectively.The shortest response time of the prepared YBCO film is 72ns,while the response time of the prepared LCMO film is only 34 ns.The sensitivity of YBCO film and LCMO film being 2.73μV/（k W·m²）and 5.03μV/（k W·m²）,respectively,after static calibration of heat flux.