Abstract We report the tuning of third-harmonic generation and nonlinear absorption process in Cl doped ZnO (Cl: ZnO) thin films by energetic electron beam irradiation. The structural studies outcomes the stability of the films based on the nominal variations observed in structural parameters on irradiation. The absorption edge shows a redshift at higher irradiation dosage and bandgap of the film shows a drop from 3.28 eV to 3.22 eV at 20 kGy dosages. The morphology of the films has undergone a drastic change on irradiation and grains are found to be shattered and islands are formed at different regions of the scan area. The photoluminescence (PL) spectra show substantial change after the irradiation and number of emissions centres decreased along with peak broadening effect. The studies confirm that radiative defects in the films decreased which in turn give rise to enhancement of non-radiative defects. The Raman spectra depicts three phonon modes E2H-E2L, A1 (TO) and E2H similar to unirradiated films. The E2H mode peak has dominated in all the irradiated films confirming the hexagonal wurtzite structure of the films. On irradiation, the asymmetry observed in the core level O 1s XPS spectra has changed and a single peak positioned around 529.8 eV was observed indicating the quenching of oxygen-related defects. Third harmonic generation studies exhibit an enhancement in the THG intensity upon electron beam incorporation attributed to optical absorption and excitonic effects. Open aperture Z-scan measurement shows a high βeff of 31 × 10-2 cm/W at 20 kGy irradiated films due to enhanced scattering induced nonlinear absorption phenomena. The enhanced nonlinear optical properties exhibited by Cl: ZnO thin films show promising applications of grown material in frequency conversion and optical filtering devices.

中文翻译：

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在 Cl: ZnO 薄膜中电子束辐照下改进的三次谐波非线性光学过程

摘要 我们报告了通过高能电子束辐照在 Cl 掺杂的 ZnO (Cl: ZnO) 薄膜中调节三次谐波产生和非线性吸收过程。结构研究基于在辐射时观察到的结构参数的名义变化得出薄膜的稳定性。吸收边在较高辐射剂量下显示红移，并且在 20 kGy 剂量下，薄膜的带隙从 3.28 eV 下降到 3.22 eV。薄膜的形态在辐照下发生了剧烈的变化，发现颗粒破碎，在扫描区域的不同区域形成岛屿。光致发光（PL）光谱在辐照后发生显着变化，发射中心数量减少，峰展宽效应。研究证实，薄膜中的辐射缺陷减少，进而导致非辐射缺陷的增强。拉曼光谱描绘了三种声子模式 E2H-E2L、A1 (TO) 和 E2H，类似于未照射的薄膜。E2H 模式峰在所有辐照薄膜中占主导地位，证实了薄膜的六方纤锌矿结构。在辐照时，在核心能级 O 1s XPS 光谱中观察到的不对称性发生了变化，观察到一个位于 529.8 eV 附近的单峰，表明氧相关缺陷的淬灭。三次谐波产生研究表明，由于光吸收和激子效应，在电子束并入后 THG 强度增强。由于增强的散射引起的非线性吸收现象，开孔 Z 扫描测量显示在 20 kGy 辐照薄膜上具有 31 × 10-2 cm/W 的高 βeff。Cl: ZnO 薄膜表现出的增强的非线性光学特性显示了生长材料在频率转换和光学滤波装置中的有前景的应用。