Uncovering β-relaxations in amorphous phase-change materials

Science Advances, vol. 6, pp. eaay6726

Abstract

Relaxation processes are decisive for many physical properties of amorphous materials. For amorphous phase-change materials (PCMs) used in nonvolatile memories, relaxation processes are, however, difficult to characterize because of the lack of bulk samples. Here, instead of bulk samples, we use powder mechanical spectroscopy for powder samples to detect the prominent excess wings-a characteristic feature of β-relaxations-in a series of amorphous PCMs at temperatures below glass transitions. By contrast, β-relaxations are vanishingly small in amorphous chalcogenides of similar composition, which lack the characteristic features of PCMs. This conclusion is corroborated upon crossing the border from PCMs to non-PCMs, where β-relaxations drop substantially. Such a distinction implies that amorphous PCMs belong to a special kind of covalent glasses whose locally fast atomic motions are preserved even below the glass transitions. These findings suggest a correlation between β-relaxation and crystallization kinetics of PCMs, which have technological implications for phase-change memory functionalities.

Authors 6

1. Si‐Xu Peng corresponding

   Huazhong University of Science and Technology

   Affiliation as printed

   Wuhan National High Magnetic Field Center and School of Physics, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China

2. Yudong Cheng corresponding Aachen I. Institute of Physics (IA)

   RWTH Aachen University

   Affiliation as printed

   I. Institute of Physics (IA), RWTH Aachen University, 52074 Aachen, Germany

3. Julian Pries Aachen I. Institute of Physics (IA)

   RWTH Aachen University

   Affiliation as printed

   I. Institute of Physics (IA), RWTH Aachen University, 52074 Aachen, Germany

4. Shuai Wei corresponding Aachen I. Institute of Physics (IA)

   RWTH Aachen University

   Affiliation as printed

   I. Institute of Physics (IA), RWTH Aachen University, 52074 Aachen, Germany

5. Hai‐Bin Yu corresponding

   Huazhong University of Science and Technology

   Affiliation as printed

   Wuhan National High Magnetic Field Center and School of Physics, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China

6. Matthias Wuttig corresponding Aachen I. Institute of Physics (IA)

   Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   I. Institute of Physics (IA), RWTH Aachen University, 52074 Aachen, Germany

   JARA-Institute Green IT (PGI-10), FZ-Jülich, 52428 Jülich, Germany