Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign (UIUC), Urbana, IL 61801, USA.
Science. 2009 Nov 13;326(5955):980-4. doi: 10.1126/science.1177483.
Phase transformation generally begins with nucleation, in which a small aggregate of atoms organizes into a different structural symmetry. The thermodynamic driving forces and kinetic rates have been predicted by classical nucleation theory, but observation of nanometer-scale nuclei has not been possible, except on exposed surfaces. We used a statistical technique called fluctuation transmission electron microscopy to detect nuclei embedded in a glassy solid, and we used a laser pump-probe technique to determine the role of these nuclei in crystallization. This study provides a convincing proof of the time- and temperature-dependent development of nuclei, information that will play a critical role in the development of advanced materials for phase-change memories.
相变通常始于成核，在成核过程中，一小群原子组织成不同的结构对称性。经典成核理论已经预测了热力学驱动力和动力学速率，但除了在暴露的表面上，纳米级核的观察一直是不可能的。我们使用一种称为涨落透射电子显微镜的统计技术来检测嵌入玻璃态固体中的核，并使用激光泵浦探测技术来确定这些核在结晶中的作用。这项研究提供了核随时间和温度发展的令人信服的证据，这些信息将在相变存储器先进材料的开发中发挥关键作用。
