低维凝聚态物质的相变与结构调控

Phase transitions and structural regulation of low-dimensional condensed-matter

低维凝聚态物质已被广泛应用于纳米电子、传感器、离子电池、太阳能电池、能量收集/存储和微/纳米机电等领域,其微观结构与物理性能的关联是凝聚态物理学研究的核心内容.在低维尺度下,凝聚态物质的结构对应力、温度、电场等外界因素非常敏感.因此,我们可以在一个多参数空间对其结构及物性进行精细调控,进而实现一系列新奇量子物态.澄清外场作用下低维凝聚态物质结构相变的原子机制是实现上述目标的关键一环.本文简要介绍本课题组近年来针对低维物质结构稳定性研究的相关进展:(1)应力场作用下,CuO和ZnO纳米线的可逆结构相变机理;(2)高温条件下,低维W、Cu_(2)Se的结构相变机制;(3)电场作用下,钠离子迁移对框架结构钠钨青铜纳米材料结构稳定性的影响;(4)高能电子束辐照对钠钨青铜结构稳定性的影响.上述结果澄清了低维凝聚态物质在单一外场作用下的原子尺度相变过程,进一步探讨了基于外场作用下低维凝聚态物质的结构调控机理.

Low-dimensional condensed matter has been widely used in nano electronics,sensors,ion batteries,solar cells,energy collection/storage,micro/nano electromechanical fields,etc.The relationship between its microstructure and physical properties is the core content of condensed matter physics research.At low dimensional scales,the structures of condensed matter are extremely sensitive to external environments including mechanical stress,temperature,electric field,etc.Therefore,we can finely tune the structures and physical properties in a multi-parameter space,thereby realizing a series of novel quantum states.Clarifying the atomistic phase transition mechanisms under the external fields is a key step in achieving the above objectives.Transmission electron microscopy has become an indispensable tool for characterizing the microstructure of low dimensional materials.The development of in situ transmission electron microscopy technology with high temporal and spatial resolution provides an excellent platform for dynamically characterizing the structure and chemical composition evolution of low-dimensional materials under external stimuli(stress field,temperature field,and electric field).In this review,we briefly introduce our recent progress on investigating the structural stability of low-dimensional materials:(1)Anelasticity of Cu O nanowires induced by phase transformation and structural stability of Zn O materials subjected to the mechanical stress;(2)structural stability of low-dimensional W and Cu_(2Se)materials at high temperatures;(3)the influence of Na+migration on the structural stability of low-dimensional frame structure sodium tungsten bronze under electric fields;(4)the effect of high-energy electron beam irradiation on structural stability of sodium tungsten bronze.The relevant results clarify the atomic-scale phase transition mechanisms of low-dimensional condensed matter and provide a reference for structural modulation by applying different external fields.In addition,there are still many areas that need to be explored.(1)This review only focuses on the influence of a single external field.In practical work,devices may be affected by multiple physical fields such as combined stress/temperature or stress/electric field.The development of multifunctional specimen holders could promote in situ electron microscopy technology in the future.(2)The current research focuses on the atomic structure of condensed matter.In the future,we need to combine electronic holography,segmented annular all field(SAAF)and other technologies to characterize the localized electronic structures.(3)Establishing the correlation between microstructures and macroscopic physical properties requires the continued development of large-scale and multi-scale structural characterization methods,which can provide comprehensive understanding of the microstructure-property interplay.