研究缺铜 CuInP2S6 中相分离域之间的应变,Chemistry of Materials

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研究缺铜 CuInP2S6 中相分离域之间的应变
Chemistry of Materials ( IF 7.2 ) Pub Date : 2023-09-18 , DOI: 10.1021/acs.chemmater.3c01238
Rahul Rao ₁ , Ryan Selhorst _{1,

2} , Jie Jiang ₁ , Benjamin S. Conner _{3,

4} , Ryan Siebenaller ₅ , Emmanuel Rowe _{1,

4,

6,

7,

8} , Andrea N. Giordano _{1,

4} , Ruth Pachter ₁ , Michael A. Susner ₁

Affiliation

CuInP ₂ S ₆ (CIPS) 是一种新兴的层状铁电材料，其居里温度高于室温。当用 Cu 缺陷（即 Cu _{1– x} In _{1+ x /3} P ₂ S ₆）合成时，材料在同一单晶内偏析为 CIPS 和 In _4/3 P ₂ S ₆ (IPS) 自组装异质结构。这种偏析导致 CIPS 和 IPS 相之间出现显着的面内和面外应变，因为 CIPS (IPS) 域的体积分数随着 Cu 分数的减少而收缩（增长）。在这里，我们合成了具有不同 Cu 含量（x = 0、0.2、0.3、0.4、0.5、0.7、0.8 和 1）的 CIPS，并通过各自的拉曼、红外、和光学反射光谱。密度泛函理论计算揭示了 CIPS 和 IPS 相特有的振动模式，可用于通过二维拉曼映射来区分这两个相。CIPS 和 IPS 拉曼峰的成分依赖性频率和强度的比较显示出随着 CIPS 相分数（即 Cu/In 比率）降低的有趣趋势。我们的数据揭示了红移和蓝移的拉曼和红外峰值频率，我们将其与材料分离到 CIPS 和 IPS 化学域中产生的晶格应变相关联。_{当 Cu/In 比率为 0.33 (Cu 0.4} In _1.2 P ₂ S ₆ ) 时，应变最高，我们将其归因于 CIPS 和 IPS 相彼此施加的相等且相反的应变。此外，我们从光学反射光谱中提取的带隙显示值有所下降，其中 Cu _0.4 In _1.2 P ₂ S ₆具有最低值~2.3 eV。

"点击查看英文标题和摘要"

Investigating Strain between Phase-Segregated Domains in Cu-Deficient CuInP2S6

CuInP₂S₆ (CIPS) is an emerging layered ferroelectric material with a Curie temperature above room temperature. When synthesized with Cu deficiencies (i.e., Cu_1–xIn_1+x/3P₂S₆), the material segregates into CIPS and In_4/3P₂S₆ (IPS) self-assembled heterostructures within the same single crystal. This segregation results in significant in-plane and out-of-plane strains between the CIPS and IPS phases as the volume fraction of the CIPS (IPS) domains shrinks (grows) with a decreasing Cu fraction. Here, we synthesized CIPS with varying amounts of Cu (x = 0, 0.2, 0.3, 0.4, 0.5, 0.7, 0.8, and 1) and measured the strains between the CIPS and IPS phases through the evolution of the respective Raman, infrared, and optical reflectance spectra. Density functional theory calculations revealed vibrational modes that are unique to the CIPS and IPS phases, which can be used to distinguish between the two phases through two-dimensional Raman mapping. A comparison of the composition-dependent frequencies and intensities of the CIPS and IPS Raman peaks showed interesting trends with a decreasing CIPS phase fraction (i.e., Cu/In ratio). Our data reveal red- and blue-shifted Raman and infrared peak frequencies that we correlate to lattice strains arising from the segregation of the material into CIPS and IPS chemical domains. The strain is highest for a Cu/In ratio of 0.33 (Cu_0.4In_1.2P₂S₆), which we attribute to the equal and opposite strains that the CIPS and IPS phases exert on each other. In addition, the bandgaps we extracted from the optical reflectance spectra revealed a decrease in values, with Cu_0.4In_1.2P₂S₆ having the lowest value of ∼2.3 eV.

更新日期：2023-09-18

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