Cho Ju-Young, Lee So-Yeon
Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea.
School of Materials Science and Engineering, Kumoh National Institute of Technology, Gumi 39177, Republic of Korea.
Materials (Basel). 2024 Dec 31;18(1):132. doi: 10.3390/ma18010132.
Phase-change random access memory (PcRAM) faces significant challenges due to the inherent instability of amorphous GeSbTe (GST). While doping has emerged as an effective method for amorphous stabilization, understanding the precise mechanisms of structural modification and their impact on material stability remains a critical challenge. This study provides a comprehensive investigation of elastic strain and stress in crystalline lattices induced by various dopants (C, N, and Al) through systematic measurements of film thickness changes during crystallization. Through detailed analysis of cross-sectional electron microscopy data and theoretical calculations, we reveal distinct behavior patterns between interstitial and substitutional dopants. Interstitial dopants (C and N) generate substantial elastic strain energy (9 J/g) due to their smaller atomic radii (0.07-0.08 nm) and ability to occupy spaces between lattice sites. In contrast, substitutional dopants (Al) produce lower strain energy (5 J/g) due to their similar atomic radius (0.14 nm) to host atoms. We demonstrate that N doping achieves higher elastic strain energy compared to C doping, attributed to its preferential formation of Ge-N bonds and resulting lattice distortions. The correlation between dopant properties, structural features, and induced strain energy provides quantitative insights for optimizing dopant selection. These findings establish a fundamental framework for understanding dopant-induced thermodynamic stabilization in GST materials, offering practical guidelines for enhancing the reliability and performance of next-generation PcRAM devices.
相变随机存取存储器（PcRAM）由于非晶态锗锑碲（GST）固有的不稳定性而面临重大挑战。虽然掺杂已成为一种有效的非晶态稳定化方法，但了解结构改性的确切机制及其对材料稳定性的影响仍然是一项关键挑战。本研究通过系统测量结晶过程中的膜厚变化，全面研究了各种掺杂剂（碳、氮和铝）在晶格中引起的弹性应变和应力。通过对横截面电子显微镜数据的详细分析和理论计算，我们揭示了间隙型和替代型掺杂剂之间不同的行为模式。间隙型掺杂剂（碳和氮）由于其较小的原子半径（0.07 - 0.08纳米）以及占据晶格位点之间空间的能力，会产生大量的弹性应变能（约9焦耳/克）。相比之下，替代型掺杂剂（铝）由于其与主体原子相似的原子半径（0.14纳米），产生的应变能较低（约5焦耳/克）。我们证明，与碳掺杂相比，氮掺杂实现了更高的弹性应变能，这归因于其优先形成的锗 - 氮键以及由此产生的晶格畸变。掺杂剂性质、结构特征和诱导应变能之间的相关性为优化掺杂剂选择提供了定量见解。这些发现为理解掺杂剂诱导的GST材料热力学稳定化建立了一个基本框架，为提高下一代PcRAM器件的可靠性和性能提供了实用指南。
