PT  - JOURNAL ARTICLE
AU  - Peng, Si-Xu
AU  - Cheng, Yudong
AU  - Pries, Julian
AU  - Wei, Shuai
AU  - Yu, Hai-Bin
AU  - Wuttig, Matthias
TI  - Uncovering β-relaxations in amorphous phase-change materials
AID  - 10.1126/sciadv.aay6726
DP  - 2020 Jan 01
TA  - Science Advances
PG  - eaay6726
VI  - 6
IP  - 2
4099  - http://advances.sciencemag.org/content/6/2/eaay6726.short
4100  - http://advances.sciencemag.org/content/6/2/eaay6726.full
SO  - Sci Adv2020 Jan 01; 6
AB  - 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.