Discovery of highly polarizable semiconductors BaZrS3 and Ba3Zr2S7
Discovery of highly polarizable semiconductors BaZrS3 and Ba3Zr2S7
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DOI：
10.1103/physrevmaterials.4.091601
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发表时间：
2020-06
影响因子：
3.4
通讯作者：
Stephen Filippone;Boyang Zhao;Shanyuan Niu;Nathan Z. Koocher;D. Silevitch;I. Fina;J. Rondinelli;J. Ravichandran;R. Jaramillo
中科院分区：
文献类型：
--
作者：
Stephen Filippone;Boyang Zhao;Shanyuan Niu;Nathan Z. Koocher;D. Silevitch;I. Fina;J. Rondinelli;J. Ravichandran;R. Jaramillo
很少有已知的半导体表现出强的光学响应和大的介电极化率。具有大介电极化率的无机材料往往是宽带隙复合氧化物。对可见光和红外光具有强烈光响应的半导体往往是弱偏振的。这些趋势的有趣例外是卤化物钙钛矿和相变硫属化物。在这里，我们介绍了复杂的硫族化合物的Ba-Zr-S系统的钙钛矿和Ruddlesden-Popper结构作为一个新的家庭的高度极化的半导体。我们报告的结果，建立BaZrS 3和Ba 3 Zr 2S 7作为半导体与低频相对介电常数（${\displaystyle $}_0$）在50 - 100的范围内，和带隙在1.3 - 1.8 eV的范围内的单晶的阻抗谱。我们的电子结构计算表明，在钙钛矿BaZrS 3与Ruddlesden-Popper Ba 3 Zr 2S 7的增强的介电响应主要是由于增强的IR模式有效电荷，声子频率沿着$\langle 001 \rangle$的变化;在玻恩有效电荷和晶格刚度的差异是次要的。这种晶体结构中的共价键结合在复合氧化物中更常见，导致相当大的Frohlich耦合常数，这表明电荷载流子是大的极化子。
There are few known semiconductors exhibiting both strong optical response and large dielectric polarizability. Inorganic materials with large dielectric polarizability tend to be wide-band gap complex oxides. Semiconductors with strong photoresponse to visible and infrared light tend to be weakly polarizable. Interesting exceptions to these trends are halide perovskites and phase-change chalcogenides. Here we introduce complex chalcogenides in the Ba-Zr-S system in perovskite and Ruddlesden-Popper structures as a new family of highly polarizable semiconductors. We report the results of impedance spectroscopy on single crystals that establish BaZrS3 and Ba3Zr2S7 as semiconductors with low-frequency relative dielectric constant (${\epsilon}_0$) in the range 50 - 100, and band gap in the range 1.3 - 1.8 eV. Our electronic structure calculations indicate the enhanced dielectric response in perovskite BaZrS3 versus Ruddlesden-Popper Ba3Zr2S7 is primarily due to enhanced IR mode-effective charges, and variations in phonon frequencies along $\langle 001 \rangle$; differences in the Born effective charges and the lattice stiffness are of secondary importance. This combination of covalent bonding in crystal structures more common to complex oxides results in a sizable Frohlich coupling constant, which suggests that charge carriers are large polarons.