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arXiv 2004.13678cond-mat.mtrl-sci
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反铁电硫系过氧化物BaZrS3薄膜的铁电极化

Ferroelectric Polarization in Antiferroelectric Chalcogenide Perovskite BaZrS3 Thin Film

Juhi Pandey, Debjit Ghoshal, Dibyendu Dey, Tushar Gupta, A. Taraphder, Nikhil Koratkar, Ajay Soni

摘要:

块状硫族化合物钙钛矿BaZrS 3(BZS)在可见光区具有直接带隙,是一种重要的光伏材料,但由于其反铁电(AF)性质而具有有限的适用性。目前,铁电(FE)钙钛矿基光致发光材料因其环境稳定性和更好的能量转换效率而引起了极大的关注,这是由于反转对称中心的丢失而导致的。利用变温拉曼光谱和第一性原理计算研究了化学气相沉积(CVD)法生长的BZS薄膜的反铁电-铁电(AF-FE)相。Fe相的起源是由A7 g ~ 300 cm-1和B1 g ~ 5 ~ 420 cm-1模的反常行为确定的,这涉及ZrS 6八面体顶位原子的振动。此外,低于60 K,B1 g1和B2 g2(~ 85 cm-1)模式出现,而B12 g(~ 60 cm-1)消失,以稳定Pnma结构对铁电性的局部扭曲。这里,B2 g2和B1 g2涉及Ba原子以AF方式的振动,而B1 g1还涉及八面体的旋转。我们的第一性原理计算证实了铁的出现是由于氧杂质局部地存在于硫原子的顶点位置,导致ZrS 6八面体中的反转对称中心丢失的结果。

英文摘要:

Bulk chalcogenide perovskite BaZrS3 (BZS), with a direct band gap in visible region, is an important photovoltaic material, albeit with limited applicability owing to its antiferroelectric (AF) nature. Presently, ferroelectric (FE) perovskite-based photovoltaics are attracting enormous attention for environmental stability and better energy conversion efficiency through enhanced charge separation, owing to loss of center of inversion symmetry. We report on antiferroelectric-ferroelectric (AF-FE) phases of BZS thin film, grown with chemical vapor deposition (CVD), using temperature-dependent Raman investigations and first-principles calculations. The origin of FE phases is established from anomalous behavior of A7g ~ 300 cm-1 and B1g5 ~ 420 cm-1 modes, which involves the vibration of atoms at apical site of ZrS6 octahedra. Additionally, below 60 K, B1g1 and B2g2 ( ~ 85 cm-1) modes appear whereas B12g (~ 60 cm-1) disappears to stabilize the Pnma structure against ferroelectricity by local distortion. Here, B2g2 and B1g2 involve vibrations of Ba atoms in AF manner while B1g1 involves, in addition, the rotation of octahedra as well. Our first-principles calculations confirm that FE appears as a result of loss of center of inversion symmetry in ZrS6 octahedra due to existence of oxygen (O) impurities placed locally at apical sites of sulfur (S) atom.

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