Cheng Yan, Cai Daolin, Zheng Yonghui, Yan Shuai, Wu Lei, Li Chao, Song Wenxiong, Xin Tianjiao, Lv Shilong, Huang Rong, Lv Hangbing, Song Zhitang, Feng Songlin
State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China.
Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, Shanghai 200241, China.
ACS Appl Mater Interfaces. 2020 May 20;12(20):23051-23059. doi: 10.1021/acsami.0c02507. Epub 2020 May 7.
Carbon (C)-doped GeSbTe material is a potential candidate in phase change random access memory (PCRAM) because of its superb thermal stability and ultrahigh cycle endurance. Unfortunately, the role and distribution evolution of C-dopant is still not fully understood, especially in practical industrial devices. In this report, with the aid of advanced spherical aberration corrected transmission electron microscopy, the mechanism of microstructure evolution manipulated by C-dopant is clearly defined. The grain-inner C atoms distinctly increase cationic migration energy barriers, which is the fundamental reason for promoting the thermal stability of metastable face-centered-cubic phase and postponing its transition to the hexagonal structure. By current pulses stimulation, the stochastic grain-outer C clusters tend to aggregate in the active area by breaking C-Ge bonding; thus, grain growth and elemental segregation are effectively suppressed to improve device reliability, for example, lower SET resistance, shorter SET time, and enlarged RESET/SET ratio. In short, the visual distribution variations of C-dopant can manipulate the performance of the PCRAM device, having much broader implications for optimizing its microstructure transition and understanding C-doped material system.
碳（C）掺杂的锗锑碲材料因其出色的热稳定性和超高的循环耐久性，是相变随机存取存储器（PCRAM）中的潜在候选材料。不幸的是，C掺杂剂的作用和分布演变仍未完全了解，尤其是在实际工业设备中。在本报告中，借助先进的球差校正透射电子显微镜，明确了由C掺杂剂操纵的微观结构演变机制。晶粒内部的C原子明显增加了阳离子迁移能垒，这是促进亚稳态面心立方相的热稳定性并推迟其向六方结构转变的根本原因。通过电流脉冲刺激，随机的晶粒外部C簇倾向于通过破坏C-Ge键在活性区域聚集；因此，有效地抑制了晶粒生长和元素偏析，从而提高了器件可靠性，例如降低了SET电阻、缩短了SET时间并扩大了RESET/SET比。简而言之，C掺杂剂可视化的分布变化可以操纵PCRAM器件性能，这对于优化其微观结构转变和理解C掺杂材料系统具有更广泛意义。
