title: Remarkably stable amorphous metal oxide grown on Zr-Cu-Be metallic glass.
abstract: In the present study, we investigated the role of an aliovalent dopant upon stabilizing the amorphous oxide film. We added beryllium into the Zr50Cu50 metallic glass system, and found that the amorphous oxide layer of Be-rich phase can be stabilized even at elevated temperature above Tg of the glass matrix. The thermal stability of the amorphous oxide layer is substantially enhanced due to Be addition. As confirmed by high-temperature cross-section HR-TEM, fully disordered Be-added amorphous layer is observed, while the rapid crystallization is observed without Be. To understand the role of Be, we employed ab-initio molecular dynamics to compare the mobility of ions with/without Be dopant, and propose a disordered model where Be dopant occupies Zr vacancy and induces structural disorder to the amorphous phase. We find that the oxygen mobility is slightly suppressed due to Be dopant, and Be mobility is unexpectedly lower than that of oxygen, which we attribute to the aliovalent nature of Be dopant whose diffusion always accompany multiple counter-diffusion of other ions. Here, we explain the origin of superior thermal stability of amorphous oxide film in terms of enhanced structural disorder and suppressed ionic mobility due to the aliovalent dopant.
authors.affiliation: Metallic Materials Division, Korea Institute of Materials Science, 797 Changwondaero, Seongsan-Gu, Changwon, Gyeongnam 642-831 Korea.
authors.forename: Ka Ram
authors.initials: KR
authors.lastname: Lim
authors.affiliation: Global E3 Institute and Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-Ro, Seodaemun-Gu, Seoul 120-749 Korea.
authors.forename: Chang Eun
authors.initials: CE
authors.lastname: Kim
authors.affiliation: Center for Non-crystalline Materials, Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-Ro, Seodaemun-Gu, Seoul 120-749 Korea.
authors.forename: Young Su
authors.initials: YS
authors.lastname: Yun
authors.affiliation: Department of Optical Engineering, Cheongju University, 36 Naedock-Dong, Cheongju 360-764 Korea.
authors.forename: Won Tae
authors.initials: WT
authors.lastname: Kim
authors.affiliation: Global E3 Institute and Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-Ro, Seodaemun-Gu, Seoul 120-749 Korea.
authors.forename: Aloysius
authors.initials: A
authors.lastname: Soon
authors.affiliation: Center for Non-crystalline Materials, Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-Ro, Seodaemun-Gu, Seoul 120-749 Korea.
authors.forename: Do Hyang
authors.initials: DH
authors.lastname: Kim