Research On Micromachining Technology And Preparation Of DC SQUID Magnetomete

Since the discovery of superconducting materials,the research on superconducting materials has been deepening.Superconducting materials have important applications in weak magnetic detection,such as high-temperature superconducting magnetometers,gradient meters,and so on.At present,there are two research directions for the research of high-temperature superconducting magnetometers:firstly,the basic theory of device design and simulation for the direct current superconducting quantum interference device（DC SQUID）;secondly,the fabrication of DC SQUID under the guidance of theory.This dissertation mainly studies the basic principle of high-temperature superconducting magnetometer and describes the characteristic equations of DC SQUID according to its equivalent circuit.Based on the basic theory of DC SQUID,a high-temperature superconducting magnetometer is designed and manufactured.This dissertation is divided into the following three aspects:Firstly,the growth conditions for the high temperature superconducting thin films are studied.Using a single crystal STO substrates,the YBa₂Cu₃O_7-δ（YBCO）film growth conditions were explored.Before epitaxial growth of YBCO high temperature superconducting thin films,the STO substrate is been heat-treated to obtain a growth plane with atom level smoothness.By changing the substrate temperature,laser repeating frequency and target-to-substrate distance,the best epitaxial growth conditions are obtained,that is,when the substrate temperature is at 740°C,the laser repeating frequency is 2 Hz and the target-to-substrate distance is 6 cm,a good high-temperature superconducting thin film with a critical temperature as high as 89.0 K is successfully prepared on the single crystal substrate.Subsequently,high-quality epitaxial growth of YBCO films was also realized on 24oSTO（100）bicrystal substrates,with a critical transition temperature of 89.4K.Secondly,the micromachining technology of high temperature superconducting thin films is explored.Optimize and determine the best lithography conditions by changing the glue throwing speed,exposure time and development time;By changing the values of beam current and accelerating voltage,the effects of them on etching rate are verified,and the etching rates under different conditions are determined.Then,we selected the R-T curve to verify the effect of etching time on the properties of superconducting thin films,and selected the etching conditions with the least damage to the thin films,that is,argon ion energy of 345 e V and argon ion beam current of 60 m A.This micromachining process has guiding significance for processing micron-sized devices.Finally,the high-temperature superconducting thin film is processed by the above micromachining process,and the preparation of the high-temperature superconducting magnetometer is completed.Through the test of R-T curve and I-V characteristic curve of magnetometer,the transition temperature is 89.3 K and the critical current density is 2.3MA/cm².