R&D: Direct Observation of Phase-Change Volume in Contact Resistance Change Memory Using N-doped Cr2Ge2Te6 Phase-Change Material

Applied Physics Letter has published an article written by Yi Shuang, WPI Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577, Japan, Daisuke Ando, Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-11 Aoba-yama, Sendai 980-8579, Japan, Yunheub Song, Department of Electronic Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, South Korea, and Yuji Sutou, WPI Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577, Japan, and Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-11 Aoba-yama, Sendai 980-8579, Japan.

Abstract: “As we strive for faster and denser nonvolatile memory, a two-terminal phase-change random access memory device has been developed to fulfill this pressing need. This device utilizes a phase-change material (PCM) that experiences reversible resistive switching. Our study delved into the resistive switching behavior in a nitrogen-doped Cr₂Ge₂Te₆ (NCrGT) contact resistance change memory, which employs a T-shape cell. The results of our study were highly promising: NCrGT memory cells showed a remarkable 90% reduction in Reset energy compared to the traditional PCM Ge₂Sb₂Te₅. This notable reduction is attributed to the smaller phase-change volume of NCrGT, which was fine-tuned by the contact property. Moreover, we found that the N dopant was robustly distributed in the CrGT matrix during switching. Furthermore, we directly observed the phase-change area of the T-shape cell using transmission electron microscopy and energy-dispersive x-ray spectroscopy. After 10⁴ of switching, our findings revealed that failure within the cells was caused by atom migration.“