Research on Modulation of Physical Properties of Typical Functional Thin Film Devices by Controllable Interface

Author:Yao Guang

Supervisor:lin zuo


Degree Year:2019





Advanced functional film materials cover the physical and chemical properties of electricity,magnetism,light,heat,etc.,and have always been the focus of worldwide academic,industrial and high-tech industries,and its related research has penetrated into many fields such as materials science,information science,and life science.The extensive research on new functional thin film materials will lead to an innovation in the field of materials technology and are expected to be applied in emerging fields such as highdensity information storage,high-precision smart sensing,and wearable electronic devices.However,the precise regulation of the structure of the functional thin film material,customization of film physical properties as well as the flexible and effective usage of them are a key challenge in implementing many functional devices.Hence,based on the mismatch strain introduced during the growth process and the applied strain,this dissertation focuses on the interface mechanism of physical properties of solid-state and flexible thin-film electronic devices,and carried out systematic research: a new model for the performance of local strain-regulated solid-state thin film devices has been established,and a model of the energy band structure of the external stress-regulating flexible thin film device was constructed.The PAD method was used to deposit the functional oxide film on the miscut LAO substrate with surface-step microstructure.The regulation of the performance of solidfilm devices by miscut LAO substrates has been investigated and proposed the local strain-regulated model.When the annealing pretreatment temperature reached 900 °C,the surface of the different miscut directions([100] and [110])forms a smooth surface and a zigzag step surface microstructure respectively.In addition,varying widths were formed on the surface of miscut substrates with different miscut angles,and annealing treatment promoted surface step gathering to reduce surface energy.Local strainregulated growth model can reduce the dislocation density in the CCTO film,and reduced the dielectric loss of the film while regulating the dielectric constant.Specifically,the CCTO dielectric constant on the 5° miscut substrate was 1400,and the dielectric loss was reduced by half an order of magnitude.In addition,the local strain induced by the miscut LAO substrate can regulate the magnetic and dielectric properties of the deposited LSMO and BST films,and anisotropic properties were introduced in both films.Specifically,the difference of dielectric constant(11%)and tuning ability(5%)can be obtained in BST film grown on the 1° miscut LAO substrate.Based on the inspiration of physical properties of thin film devices regulated by solid substrate stress,ITO/Si flexible heterojunction photoelectric devices were further designed,and the regulation mechanism of external stress on energy band structure of heterojunction was studied in depth.Experimentally,the problem of the transfer process of the multilayer film was solved.According to the experimental results and the mechanical theory model,the relationship between bending strain and energy band regulation was quantified.The method of energy performance optimization was discussed by using energy band strain regulation theory.The bending causes a red shift of the Raman characteristic peak of Si in the system due to the uniaxial tensile strain.The heterojunction has no obvious damage and crack after multiple bending,indicating that the flexible structure has mechanical reliability.By bending strain regulation,the turn-on voltage of the heterojunction can be reversibly transformed between 0.23 V and 0 V,with a valence band structure of Ohmic-Schottky reversible transition.Based on the IV curve,IPCE test results and theoretical model,the relationship between the bending strain and the barrier height of the heterojunction was established,and the test results were in good agreement with the theoretical model.The light response test of the flexible system shows that the heterojunction photodetector was responsive to light at 400-800 nm and has a large photocurrent when irradiated at 405 nm.Compared with the planar flexible heterojunction,the heterojunction with a bending radius of 3 cm has more stable detection sensitivity and linear dynamic range,and the response and recovery time under the optical pulse signal was reduced by an order of magnitude(<1 ms).The stable photoresponse of the flexible heterojunction for a long time confirms the reliability of the detection performance.In addition,the ITO/Si heterojunction has a light transmittance of up to 65% and is suitable for for multilayer integration.The research on the physical property control mechanism of solid-state and flexible thin-film electronic devices through strain provides technical and theoretical basis for the preparation of new thin-film electronic devices,and a new way for the expansion of interface strain control.