Tang Guohong, He Yuqi, Liao Hongmei, Zhang Shuangqi, Chu Xiaofei, Si Rongxia, Jin Zhiyuan, Du Yuhang, Wang Chi, Chen Baojun, He Zhiyu, Huang Wei
College of Materials Science and Engineering, Sichuan University, Chengdu 610064, China.
ACS Appl Mater Interfaces. 2024 Nov 13;16(45):62411-62420. doi: 10.1021/acsami.4c14743. Epub 2024 Nov 2.
LiGaTe is a promising nonlinear optical crystal with a large figure of merit (/), but it is difficult to grow the LiGaTe single crystal due to its extreme instability. In this work, we used Ag to replace Li and successfully grew a LiAgGaTe crystal by the modified Bridgman method for the first time. We found it has thermal stability below 200 °C in an atmospheric environment, and the thermal expansion coefficient is positive. This is different from LiGaTe and AgGaTe which have a negative thermal expansion coefficient along the -axis. When the temperature exceeds 200 °C, LiAgGaTe is easily decomposed and oxidized. Under closed vacuum conditions, the melting and solidifying points of LiAgGaTe are measured to be 719 and 694 °C. XPS spectra show that the binding energies of Li, Ga, and Te are higher than LiGaTe, and the surface is easily oxidized. The A1 vibration modes are found at 117.72 and 135.44 cm by the Raman spectrum which is related to the Te and Ga-Te bond in [GaTe] tetrahedra. LiAgGaTe has a wide transmittance range from 0.94 to 20 μm, and there was two-photon absorption near 16 μm. The phonon spectrum and PDOS were simulated by the DFT calculation to study the phonon vibration modes in the lattice, which shows that the density of the Raman vibration is higher than those of AgGaTe and LiGaTe. The SHG test results showed that the SHG response intensity of LiAgGaTe is 1.5 times that of AgGaS, which shows its excellent nonlinear optical properties for mid-IR applications.
LiGaTe是一种有前途的非线性光学晶体，其品质因数较大，但由于其极端不稳定性，生长LiGaTe单晶很困难。在这项工作中，我们用Ag取代Li，并首次通过改进的布里奇曼法成功生长出LiAgGaTe晶体。我们发现它在大气环境中200℃以下具有热稳定性，且热膨胀系数为正。这与沿c轴具有负热膨胀系数的LiGaTe和AgGaTe不同。当温度超过200℃时，LiAgGaTe容易分解和氧化。在封闭真空条件下，测得LiAgGaTe的熔点和凝固点分别为719℃和694℃。XPS光谱表明，Li、Ga和Te的结合能高于LiGaTe，且表面容易氧化。通过拉曼光谱在117.72和135.44 cm-1处发现了A1振动模式，这与[GaTe]四面体中的Te和Ga-Te键有关。LiAgGaTe的透过率范围很宽，从0.94到20μm，在16μm附近存在双光子吸收。通过DFT计算模拟了声子谱和PDOS，以研究晶格中的声子振动模式，结果表明拉曼振动密度高于AgGaTe和LiGaTe。SHG测试结果表明，LiAgGaTe的SHG响应强度是AgGaS的1.5倍，这表明其在中红外应用中具有优异的非线性光学性能。
