Preparation And Properties Of Ge-Sb-Se Nanowires

Chalcogenide materials are widely used in mid-infrared?MIR?spectral imaging,biomedical technology,remote sensing and laser applications due to their high nonlinear refractive index,high photosensitivity and special transmission range across visible light.In recent years,they have also been widely used in the field of planar waveguides,and have been prepared into high-density multi-function photonic devices.However,previous device fabrication was top-down and limited by lithography techniques,making it difficult to achieve high density integration.Nanowires have good scalabiliy,large specific surface area and complete lattice structure due to their nanoscale size.The structural advantages of nanowires make it possible to explore material miniaturization and address high-density integration of devices.In this thesis,Ge-Sb-Se nanowires were prepared by VLS mechanism,and the nanowire growth conditions were systematically studied,including the temperature of the downstream zone,the carrier gas flow rate and the distance between the substrate and the source.The potential of Ge-Sb-Se nanowires for optical storage was explored.The main results are as follows:1.The growth conditions of the Ge-Sb-Se nanowires were optimized.The Ge-Sb-Se nanowires were prepared by VLS growth mechanism.The growth conditions of Ge-Sb-Se nanowires were optimized,that is:the distance between the substrate and the source was 7-11 cm,the carrier gas flow rate was 100 sccm,the downstream zone temperature is 350-380 ^oC and the upstream zone temperature is 540-580 ^oC.The supersaturation in the alloy droplets is the main factor to affect the morphology of the nanowires.When the supersaturation in the alloy droplets is too high,the alloy droplets tend to grow toward the large-scale nanocrystals;when the supersaturation is too low,the alloy droplets tend to grow into layer-stacked nanochips.When the appropriate supersaturation in the alloy droplets is benefit to the formation of nanowires.2.Characterization of Ge-Sb-Se nanowire microstructures.The nanowire sample grown on a substrate mainly has crystal phases such as Sb₂Se₃,GeSe₂,Ge and Se.The elemental distribution of Ge,Sb and Se in the nanowire is regular.The Ge and Sb elements are uniformly distributed over the entire nanowire,while the Se element is only distributed in a relatively narrow region near the nanowire axis.The nanowires are grown along the?111?direction,and the lattice spacing d of the Ge crystal phase is 0.331 nm,which matches the interplanar spacing d of the?111?crystal plane of the diamond structure.3.The application potential of Ge-Sb-Se nanowires in optical storage was explored.The laser ablation experiment was performed on the prepared nanowire samples.As the induced power increases?ranging from 0.5 W to 1.0 W?,the intensity of the Raman peak at 115 cm^-1,153 cm^-1 and 192cm^-1 gradually decreases.When the laser power increased to 0.7 W,the corresponding Raman spectrum is consistent with the Raman spectrum of Ge-Sb-Se glass.It indicates that the Ge-Sb-Se nanowire transformed from crystalline to amorphous.It indicates that the Ge-Sb-Se nanowires can be phase-transformed under laser induction,which provides reference value for subsequent applications in optical memory devices.