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Direct observation of growth, stability and random tiling of Al-Cu-Fe quasicrystal thin films    
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  • Hadi Parsamehr,
  • Shi-Wei Chen,
  • Shou-Yi Chang,
  • An Pang Tsai,
  • Chih-Huang Lai
Hadi Parsamehr
Department of Material Science and Engineering, National Tsing Hua University, Hsinchu, 30013, Taiwan
Author Profile
Shi-Wei Chen
National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
Shou-Yi Chang
Department of Material Science and Engineering, National Tsing Hua University, Hsinchu, 30013, Taiwan
An Pang Tsai
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan and National Institute for Materials Science, 305-0047 Tsukuba, Japan
Chih-Huang Lai
Department of Material Science and Engineering, National Tsing Hua University, Hsinchu, 30013, Taiwan

Abstract

The origin of stability in quasicrystal has been debated since the discovery of stable quasicrystals. Both energy-stabilized and entropy-stabilized mechanisms have been proposed. To address these issues, we directly observed the growth mechanisms involved in the formation of quasicrystals and other phases in real time for a multilayer Al-Cu-Fe thin films by in-situ XRD and in-situ TEM during heating and cooling. We show that the ternary phase is more thermodynamically stable compared to the binary phase, and quasicrystal formation occurs during the cooling process, specifically at 660°C, after the sample reached a liquid state. Evidence of random tiling was observed, suggesting that entropy contributes to thermodynamic stability during the initial stage of cooling. At a lower temperature of the cooling process, however, energy plays a key role in stabilization. We provide a better understanding of the growth mechanism, which is of particular importance for developing controllable synthesis of functional nanomaterials.