| In the past three decades,due to their unique one-dimensional structure,high physical and chemical stability,and excellent optoelectronic properties,one-dimensional inorganic semiconductor materials have received wide attention and have great application potential in the high-performance photonic,electronic,and optoelectronic devices.With the advent of the post-Moore era,there are more urgent demands for high performance,miniaturization and high planar integration of optoelectronic devices.The performance of the device is mainly determined by the quality of the semiconductor materials.Thus,it is important to fabricate micro/nano-scale one-dimensional inorganic semiconductors with high crystalline quality and low defect density.However,most of the reported 1D semiconductor materials are usually grown out-of-plane disorderly.They are randomly distributed on the substrate and possess nonuniform morphology,growth direction and quality,which is not conducive to device fabrication and in-plane integration.Therefore,it is necessary to find facile and efficient routes to prepare large scaled high-quality one-dimensional inorganic semiconductor materials.In view of this,in this thesis,various large-scale in-plane one-dimensional semiconductor materials were prepared by vapor phase and solution-based methods.Their growth mechanisms were studied,and high-performance photodetectors and flexible devices were realized.The results of this thesis are as follows:(1)Unidirectional PbS and PbTe planar nanorod arrays were grown on CdS nanobelt via a two-step vapor deposition route.The microstructure characterization confirmed the high crystalline quality of Cds,PbS and PbTe.It can be obtained that the epitaxial relationships between PbX(X=S and Te)nanorods and CdS nanobelt were(001)PbX∥(001)CdS and(220)PbX∥(120)CdS.The photodetectors based on PbX/CdS heterostructures array exhibit a broadband photodetection performance in the visible to infrared region(405-1550 nm).Under the illumination of 405 nm,980 nm and 1550 nm light,the maximum responsivity of the photodetector can reach 2.9 × 105 A/W、8.89 A/W and 2.00 A/W.Additionally,the photocurrent generation mechanism of the photodetector was studied.Due to the absorption of infrared light by PbX,the photogenerated carriers generated in PbX can cross the barrier at the PbX/CdS heterogeneous interface and inject into CdS with the assistance of hot electron emission and photo-thermionic effect,resulting in infrared photoresponse.This work demonstrates that the photodetectors based on high crystalline quality PbX/CdS one-dimensional heterostructures array has potential application prospect in broadband photodetection.(2)High-quality in-plane Bi2S3 nanowire arrays were prepared on the muscovite substrate by physical vapor deposition.These Bi2S3 nanowires grown along its c-axis are arranged in six-fold symmetry on the mica substrate.The epitaxial relationship in the length direction is confirmed as[001]Bi2S3∥[100]mica.We investigated the in-plane and out-of-plane growth modes of the Bi2S3 nanowires at different growth temperatures,through a kinetic model.It was found that the increase of temperature would promote the out-of-plane growth of Bi2S3 nanowires and inhibit the in-plane growth of nanowires.The in-situ prepared Bi2S3 nanowire photodetectors show a broadband photodetection performance covering the whole visible region(500-980 nm).The photodetector also exhibits an ultrasensitive near-infrared photoresponse under 830 nm light ilumination with a power density of 64 nW/cm(the maximum responsivity is 5233 A/W;specific detectivity is 1.8x1012 Jones;rise and decay time are 21 μs and 7.8 ms,respectively).Furthermore,the photodetectors possess excellent stability and bending resistance in the atmosphere.This work demonstrates that the in-plane grown high-quality Bi2S3 nanowire arrays have potential application prospects in weak infrared light detection and flexible electronics in the future.(3)Millimeter-scale lead-free in-plane CsCu2I3 nanoribbons were prepared by a solution-based spatial confinement method.These nanoribbons can be grown on a variety of substrates,which lays a foundation for the application of multifunctional devices.The structural characterization verified that the CsCu2I3 nanoribbons with orthorhombic phase have high crystalline quality.The growth process of the CsCu2I3 nanoribbons was observed in real-time through a homemade in-situ observation system.It was found that the morphology evolution of nanoribbons depended on the change of local supersaturation of the solution,and the formation of nanoribbons was determined by the combined effect of thermodynamics and kinetics.The photodetectors based on the nanoribbons show sensitive and fast ultraviolet photoresponse(the maximum responsivity is 0.27 A/W under the illumination of 365 nm light;rise and decay time are 5.8 ms and 6.0 ms,respectively),excellent flexibility and bending resistance(no obvious attenuation of photoresponse after 770 times of bending).Additionally,based on the high-quality CsCu2I3 nanoribbons,we prepared CsCu2I3/CdS nanoribbons heterojunction device.Due to the built-in electric field at the heterointerface,the hybrid device exhibits an obvious self-powered ultraviolet photodetection ability without external bias(under the irradiation of 365 nm light,the maximum responsivity is 2.63 mA/W at 0 V).This work provides a new idea for the practical application of high-quality lead-free cesium copper halides and their heterostructures in optoelectronic devices and flexible wearable devices.(4)Centimeter-sc ale CsCu2I3 planar microwire arrays were prepared through the improved spatial confinement method.This method can confine the precursor solution in the pre-fabricated microchannel arrays and control the evaporation rate of the solvent.The microstructure characterizations reveal that the orthorhombic CsCu2I3 wires have high crystalline quality and grow along the c-axis,which is determined by the one-dimensional lattice structure.Control experiments and theoretical studies indicate that the confinement of microchannels and substrates and stable solute supply determine the growth of microwires.The photodetectors based on the microwire arrays show a high UV photodetection performance.The maximum responsivity of the photodetector under 330 nm and 365 nm light is 1.29 A/W and 80 mA/W,respectively,and the rise and decay times are～640 μs and～7.1 ms.The devices based on the microwire arrays also have excellent flexibility(the photoresponse has only about 5%attenuation at a bending angle of 180°)and UV light imaging capability.This work lays a foundation for the synthesis of one-dimensional array of lead-free cesium copper halides and their applications in integrated optoelectronic devices.In this thesis,we focus on material preparation,and aim to find suitable preparation methods for the in-plane growth of one-dimensional inorganic semiconductor materials to achieve high-performance optoelectronic devices.First,the vapor phase method is used to epitaxy planar one-dimensional structures on a semiconductor substrate surface with a large number of dangling bonds;Secondly,the planar nanowire arrays were epitaxially grown on the mica substrate surface without dangling bonds,which overcame the difficulty of transferring the epitaxial one-dimensional structure;Then,in order to explore the process of preparing planar one-dimensional structures on more kinds of substrates,the solution based spatial confinement method was used to realize the growth and preparation of planar nanoribbons on various kinds of substrates;Finally,in order to obtain planar one-dimensional structure arrays with controllable direction and uniform size,an improvement was made on the spatial confinement method.Large-area planar microwire arrays were prepared with the assistance of micro-channel substrate.This thesis provides effective ideas for the in-plane preparation of one-dimensional inorganic semiconductor materials,which is of great significance for their practical applications in the multifunctional optoelectronic devices. |
