| Two-dimensional(2D)van der Walls layered materials exhibit unique physical and chemical properties which differ from their bulks due to their ultra-thin thickness,such as sub-nano or nano scales.They have attracted attention because of their huge application potential in next-generation transparent,flexible,wearable,low power consumption,and smart electronic devices.Indium selenide,including InSe and In2Se3,are typical III-VI group layered semiconducting materials.2D InSe and In2Se3display small electron effective mass and high electron mobility,small direct band gap and high light absorption coefficient,making great potential application in next-generation optoelectronic devices,especially in the field of photodetection.Up to now,the study about 2D indium selenide based self-powered photodetectors is still limited.The device structure should be further explored and the device performance should be further improved.In this dissertation,a series of indium selenide based self-powered photodetectors are designed and fabricated through combinating the structure-function relationship between material structure and properties,and device configuration and performance.The performance and working mechanism of InSe based self-powered photodetector induced by asymmetric Schottky junction and surface plasmon resonance are investagated.The modulation and enhancement mechanism of strain on the different crystalline InSe based self-powered photodetector are systematically investigated.A vertical InSe self-powered photodetector is fabricated and the performance enhancement mechanism of self-limited depletion region is studied.The ferroelectricity of 2D In2Se3 single crystal are investigated,and the self-powered photodetection performance of fabricated In2Se3ferroelectric diode is studied.In the research of plasmon resonance enhanced 2D InSe self-powered phtodetector,we design and fabricated the 2D InSe nanosheet based Schottky diode with asymmetric Schottky junction.We systematically studied the self-powered photodetection performance of InSe Schottky diode,which displays high photodetection performance,such as fast response speed and good long-term cycling stability.We synthesized Au nanoparticals arrays with nanosphere lithograph and thermal evaporation method.Next,we developed a method to realize dual-band self-powered photodetection induced by surface plasmon resonance of Au nanoparticals.The maximal enhancement ratio can reach up to 1100%.We investigated the enhanced light absorption efficiency in the range of visible-near infrared of InSe nanosheet by the quadrupole resonance of Au nanoparticals arrays.In the research of piezo-phototronic enhanced 2D InSe self-powered photodetector,a class of two-dimensional piezoelectric semiconductor materials with the same polarization orientation between layers were found,which can achieve good piezoelectric responsiveness and output stability in multi-layer materials at the same time,breaking through the limitation of piezoelectric characteristics of previous reported two-dimensional piezoelectric materials due to the number of odd and even layers.Then we designed an InSe self-powered photodetector with asymmetric depletion regions and study its photovolatic effect.Next,we systematically studied the modulation of strain on the performance of InSe based self-powered photodetectors.A method to improve the performance of?-InSe self-powered photodetector through piezoelectric-piezoresistive-optoelectronic coupling effect was developed.Under a tensile strain of 0.62%,the responsivity and detectivitiy were enhanced about 800%,and the response speed is enhanced one order of magnitude.In the research of self-limited depletion region enhanced InSe self-powered photodetector,we designed and fabricated a vertical Au-InSe-Gr Schottky diode,and the self-powered photodetection performance of the vertical InSe Schottky diode was investigated.The device exhibits a sensitive photodetection performance including an ultra-low noise current(1 f A/Hz1/2),a high responsivity(365 m A/W),and a high detectivity(1.26×1013 Jones).A concept of self-limited depletion region was proposed and its important influence on improving the response speed of vertical InSe self-powered photodetector.The strong electric field in the self-limited depletion region can drive the photo-generated carriers drift to electrode reaching a short response time of 200-450 ns,which is the fastest response speed compared with previous reported 2D semiconductor based self-powered photodetectors.In the research of bulk photovoltaic effect enhanced 2D?-In2Se3 self-powered photodetector,we studied the non-centrasymmetric structure of?-In2Se3 single crystal and found low symmetry in its multilayer form due to its unique layer stacking sequence.Then we investigated the ferroelectricity of?-In2Se3 and demonstrate the coupling of in-plane and out-of-plane polarization.Next,we studied the piezoelectricity of?-In2Se3 and find that the piezoelectric current and voltage outputs increase with layer increasing.The multilayer?-In2Se3 possesses not only high piezoelectric responsivity,but also good mechanical stability.We fabricated a ferroelectric?-In2Se3 diode and investigated its electric transport characterization and self-powered photodetection performance.The works in this dissertation have enriched the indium selenide based self-powered photodetectors,and lay a solid foundation for the application in low power consumption,high performance,and multifunctional optoelectronic devices. |
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