Phase transformation pathways of ultrafast-laser-irradiated Ln(2)O(3) (Ln = Er-Lu)

Article

关键词: X-RAY-DIFFRACTION;    INITIO MOLECULAR-DYNAMICS;    LATTICE INSTABILITY;    PRESSURE;    TIME;    SI;    SIMULATION;    GAAS;   

DOI  :  10.1103/PhysRevB.97.024104

来源: SCIE

【 摘 要 】

Ultrafast laser irradiation causes intense electronic excitations in materials, leading to transient high temperatures and pressures. Here, we show that ultrafast laser irradiation drives an irreversible cubic-to-monoclinic phase transformation in Ln(2)O(3) (Ln = Er-Lu), and explore the mechanism by which the phase transformation occurs. A combination of grazing incidence x-ray diffraction and transmission electron microscopy are used to determine the magnitude and depth-dependence of the phase transformation, respectively. Although all compositions undergo the same transformation, their transformation mechanisms differ. The transformation is pressure-driven for Ln = Tm-Lu, consistent with the material's phase behavior under equilibrium conditions. However, the transformation is thermally driven for Ln = Er, revealing that the nonequilibrium conditions of ultrafast laser irradiation can lead to novel transformation pathways. Ab initio molecular-dynamics simulations are used to examine the atomic-scale effects of electronic excitation, showing the production of oxygen Frenkel pairs and the migration of interstitial oxygen to tetrahedrally coordinated constitutional vacancy sites, the first step in a defect-driven phase transformation.

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