Nanoscale Crystalline to Amorphous Phase Transition Studies in Nanowires: Controlled Synthesis, Characterization, Memory Switching Devices and Size-Dependent Properties

技术：该项目研究了自组装Ge-Sb-Te纳米线(NW)材料在亚光刻长度尺度上的可逆晶态到非晶态的相变现象。该方法专注于合成和表征复杂的、定义良好的Ge-Sb-Te NW，并控制成分和尺寸以研究基本的相转换特性，以及原型存储元件的组装。该方法的组成部分包括：1)发展脉冲激光沉积(PLD)生长技术，以合成精确控制NW化学成分和直径的Ge-Sb-Te三元复合纳米Ws。2)用电子显微镜(扫描电子显微镜、电子显微镜)表征了纳米晶的结构和化学成分。3)研究了NWS的电场诱导相变行为及其与化学成分和尺寸(直径)的关系。研究了纳米粒子尺寸对热力学参数的影响及其对相变机制的影响。4)Ge-Sb-Te纳米晶结构相变随外加电流脉冲的原位电子显微镜分析。原子核非晶化和再结晶机制与尺寸和化学成分相关的研究。5)基于从上述实验中获得的见解来制造新型NW存储器件。非技术性：该项目涉及具有高度技术相关性的电子/光子材料科学专题领域的基础研究问题。研究和教育活动将通过本科生参与研究计划进行整合，将新的研究成果纳入教学模块，并培训来自费城地区的高中和大学教师，这些教师的学生人口来自少数族裔和代表性不足的地区。

Technical: This project addresses reversible crystalline to amorphous phase transition phenomena in self assembled Ge-Sb-Te nanowire (NW) materials at sub-lithographic length scales. The approach focuses on synthesis and characterization of complex, well defined Ge-Sb-Te NWs with control over composition and dimension for investigating fundamental phase switching properties, and assembly of prototype memory elements. Components of the approach include: 1) Development of pulsed laser deposition (PLD) growth technique to synthesize complex ternary Ge-Sb-Te NWs with precise control over NW chemical composition and diameters. 2) Characterization of structural and chemical composition of NWs with electron microscopy (SEM, TEM). 3) Investigation of electric field induced phase switching behavior and its dependence on chemical composition and size (diameter) of NWs. Study of the influence of size on thermodynamic parameters and its affect on phase transition mechanism in NWs. 4) Insitu TEM analysis of structural transformations in Ge-Sb-Te NWs as a function of applied current pulses. Size and chemical composition dependent study of amorphization and recrystallization mechanism in NWs. 5) Fabrication of novel NW memory devices based on insights obtained from the experiments described above. Non-technical: The project addresses basic research issues in a topical area of electronic/photonic materials science with high technological relevance. Research and educational activities will be integrated by the involvement of undergraduates in the research program, incorporating new research results in a teaching module, and training high school and college teachers from the Philadelphia district with student population from minority and underrepresented sections.