Bin Anooz Saud, Petrik Peter, Wang Yankun, Mukherjee Deshabrato, Schmidbauer Martin, Schwarzkopf Jutta
Opt Express. 2024 Apr 22;32(9):15597-15609. doi: 10.1364/OE.520426.
The dielectric function and interband critical points of compressively strained ferroelectric KNaNbO thin film grown by metal-organic vapor phase epitaxy (MOVPE) are studied in broad spectral and temperature ranges by spectroscopic ellipsometry (SE). The temperature dependence of the measured pseudodielectric functions is strongly affected by a structural phase transition from the monoclinic M-phase to the orthorhombic c-phase at about 428 K. Using a parametric optical constant model, the corresponding dielectric functions as well as the interband optical transitions of the film are determined in the spectral range of 0.73-6.00 eV. Standard critical point (SCP) analysis of the 2 derivatives of the dielectric functions identified three and four critical points for monoclinic and orthorhombic symmetries, respectively. A systematic redshift of the threshold energies with increasing temperatures was observed.
通过光谱椭偏仪（SE）在宽光谱和温度范围内研究了采用金属有机气相外延（MOVPE）生长的压缩应变铁电KNaNbO薄膜的介电函数和带间临界点。在约428 K时，从单斜M相到正交c相的结构相变对测量的伪介电函数的温度依赖性有强烈影响。使用参数光学常数模型，在0.73 - 6.00 eV的光谱范围内确定了薄膜的相应介电函数以及带间光学跃迁。对介电函数的二阶导数进行标准临界点（SCP）分析，分别确定了单斜和正交对称性的三个和四个临界点。观察到阈值能量随温度升高而系统地红移。
