Phase Change Nanowire Based On Electrochemical Method And The Low-power Memory Device

Phase change memory(PCM)is one of the most promising new types of memory,with significant advantages in terms of speed and integration,however,the large-scale application is still restricted by factors such as large power consumption.At present,the power consumption is mainly reduced by reducing the contact area through some new structural designs,but it often causes a large increase in process costs.In this paper,by introducing electrochemical method to prepare phase change materials,the crystalline morphology of the deposited materials can be flexibly adjusted.Small-sized phase change nanowires can be prepared without additional photolithographic processes,which minimizes PCM power consumption from the perspective of material optimization.The main contents of the thesis include:(1)The electrochemical preparation process of phase change materials was systematically studied,and phase change nanowires with good crystallinity and high purity were optimized.The grain sizes prepared from different substrates are compared,and substrates with small corrosion resistance and small particle size are preferred for deposition.The effect of the reaction p H on the density of the material is studied,and the degree of crystallization of the material is increased by adding EDTA complexing agent;Optimized the preparation and purification steps,greatly reducing the amount of impurities in the sample.(2)Aiming at the difficulty of preparing Bi₂Te₃nano-devices based on electrochemical methods,the design and comparison of FIB processing,dielectric electrophoresis,and dispersion methods for preparing nanowire lateral devices were designed and compared.Finally,nanowire memory devices with stable performance were prepared by the dispersion method.The prepared device exhibits ultra-low power consumption(Reset power consumption of 9 f J),while maintaining a large high-low resistance ratio and good cycle characteristics.(3)Based on microscopic characterization and first-principles calculations,the working mechanism of the above-mentioned Bi₂Te₃nanophase-change memory device was studied.A special crystalline/amorphous overlapping structure was observed in the nanowires through transmission electron microscopy,and first-principles calculations were used to find that this overlapping structure may be due to the introduction of C groups during the deposition process that hindered the crystallization process.The crystalline resistance of the device is increased,which significantly reduces the power consumption of the device.Based on this,the failure mechanism in this type of device is further explained.