Xu Teng, Cai Qingyuan, Duan Weibo, Wang Kaixuan, Jia Bojie, Luo Haihan, Liu Dingquan
Shanghai Key Laboratory of Optical Coatings and Spectral Modulation, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China.
School of Physical Science and Technology, ShanghaiTech University, Shanghai 200031, China.
Materials (Basel). 2025 Aug 3;18(15):3644. doi: 10.3390/ma18153644.
Potassium bromide (KBr) thin films were deposited by resistive thermal evaporation at substrate temperatures ranging from 50 °C to 250 °C to systematically elucidate the temperature-dependent evolution of their physical properties. Structural, morphological, and optical characteristics were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier transform infrared spectroscopy (FTIR). The results reveal a complex, non-monotonic response to temperature rather than a simple linear trend. As the substrate temperature increases, growth evolves from a mixed polycrystalline texture to a pronounced (200) preferred orientation. Morphological analysis shows that the film surface is smoothest at 150 °C, while the microstructure becomes densest at 200 °C. These structural variations directly modulate the optical constants: the refractive index attains its highest values in the 150-200 °C window, approaching that of bulk KBr. Cryogenic temperature (6 K) FTIR measurements further demonstrate that suppression of multi-phonon absorption markedly enhances the infrared transmittance of the films. Taken together, the data indicate that 150-200 °C constitutes an optimal process window for fabricating KBr films that combine superior crystallinity, low defect density, and high packing density. This study elucidates the temperature-driven structure-property coupling and offers valuable guidance for optimizing high-performance infrared and cryogenic optical components.
通过电阻热蒸发在50°C至250°C的衬底温度下沉积溴化钾（KBr）薄膜，以系统地阐明其物理性质随温度的演变。通过X射线衍射（XRD）、扫描电子显微镜（SEM）、原子力显微镜（AFM）和傅里叶变换红外光谱（FTIR）对结构、形态和光学特性进行了研究。结果揭示了对温度的复杂、非单调响应，而非简单的线性趋势。随着衬底温度升高，生长从混合多晶织构演变为明显的（200）择优取向。形态分析表明，薄膜表面在150°C时最光滑，而微观结构在200°C时最致密。这些结构变化直接调节光学常数：折射率在150 - 200°C范围内达到最高值，接近块状KBr的折射率。低温（6K）FTIR测量进一步表明，多声子吸收的抑制显著提高了薄膜的红外透过率。综合来看，数据表明150 - 200°C构成了制备结合了优异结晶度、低缺陷密度和高堆积密度的KBr薄膜的最佳工艺窗口。本研究阐明了温度驱动的结构 - 性能耦合，并为优化高性能红外和低温光学元件提供了有价值的指导。
