Preparation And Properties Of YBa 2 Cu 4 O 8 Film

High temperature superconducting materials are widely used in the strong and weak electronics field.The superconducting thin films can be first applied in microelectronics devices.High temperature superconductor YBa2Cu4O8(for short,Y-124)is oxide completely which has a stable stoichiometric ratio and a nearly perfect crystal structure.The twin crystal and oxygen ions defects almost can be ignored.And Y-124 has larger anisotropy and smaller room temperature resistivity than Y-123.It can be expected to find a greater LIV signal and smaller response time in the Y-124 film.Therefore the study of Y-124 will help further to understand its characteristics and expand its field of application.In this paper,Y-124 films were prepared by pulsed laser deposition technique,and the properties of Y-124 were studied.Two kinds of annealing process were studied:in-situ annealing and post annealing.A set of optimized preparation process and technical parameters were summarized for Y-124 films.Y-124 targets were synthesized by solid phase method and sol-gel method respectively.Then Y-124 films with a-axis and c-axis orientation were prepared by these two kinds of targets.Some important technical parameters of thin film growth were discussed.In-situ annealing conditions include the substrate temperature,oxygen pressure,annealing temperature annealing oxygen pressure and annealing time.In post annealing,we discussed the influence of the annealing temperature,time and atmosphere on the films structure and performance.Found experimentally,the crystalline quality and properties of the film could be appropriately changed by an in situ annealing.The crystal state and growth orientation of thin films could be changed by post annealing.For the target that was synthesised by solid phase mothed,the Y-124 film with a-axis orientation was prepared,which depositied under optimum conditions(500 ?,80Pa),and then in-situ annealed under optimum conditions(700 ?,1atm).The Y-124 phase peak and quality were the greatest.R-T curve of Y-124 film was close to a positive slope,and room temperature resistance was small.The single-phase Y-124 film with c-axis orientation was prepared under the conditions of no power covering,flowing oxygen and annealed 12 hours at 750?,and the Y-124 phase peak is the strongest.For the target that was synthesised by sol-gel mothed,the Y-124 film with a-axis orientation was prepared,which depositied under optimum conditions(600? 80Pa),and then in-situ annealed 12 hours under optimum conditions(700?,1 atm).R-T curve of Y-124 film was close to a positive slope,and room temperature resistance was small.The single-phase Y-124 film with c-axis orientation was prepared under the conditions of no power covering,flowing oxygen and annealed 12 hours at 750?,and the Y-124 phase peak is the strongest.