Synergetic Innovation Center for Quantum Effects and Application, Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, School of Physics and Electronics, Hunan Normal University, Changsha 410081, People's Republic of China.
Nanotechnology. 2018 Nov 16;29(46):465709. doi: 10.1088/1361-6528/aadf64. Epub 2018 Sep 6.
The optical confinement and strong carrier coupling within a semiconductor nanostructure cavity are crucial for the modulation of emission properties. Fundamental understanding of the light-matter interaction in a low dimensional system is important. In this paper, we synthesized high-quality hexagonal Te-doped CdS nanowires by two-step chemical vapor deposition and investigated systematically the doping concentration, temperature, excitation power, excitation wavelength dependent Raman, photoluminescence and carrier lifetime decay. Scanning electron microscopy, energy dispersive x-ray spectrometry and x-ray diffraction confirmed Te-doping in the as-prepared samples. The strong surface optical (SO) phonon mode is observed in the micro-Raman spectra of an individual Te-CdS nanowire, which is unsuitable in large-sized structures. In situ micro-photoluminescence (μ-PL) characterization shows dominant confined defect state emission with whispering gallery mode (WGM) characteristics. The emission peak position shifts under increased excitation power, demonstrating the inelastic scattering by bound carriers. In addition, the short wavelength emission modes are dominant at a low temperature (80 K) while the long wavelength emission modes are dominant at a high temperature (300 K) due to different recombination processes contributing to the WGM resonant bands, which was also confirmed by the time-resolved PL measurement. All these results reflect strong coupling between the surface evanescent-wave in the WGM cavity and the SO phonon/polaron, which will facilitate the rational tailoring of surface/interface relevant properties for nanophotonic device applications.
半导体纳米结构腔体内的光限制和强载流子耦合对于调节发射特性至关重要。深入了解低维系统中的光与物质相互作用非常重要。在本文中，我们通过两步化学气相沉积法合成了高质量的六方碲掺杂 CdS 纳米线，并系统地研究了掺杂浓度、温度、激发功率、激发波长对拉曼、光致发光和载流子寿命衰减的依赖关系。扫描电子显微镜、能谱和 X 射线衍射证实了所制备样品中的碲掺杂。在单个 Te-CdS 纳米线的微拉曼光谱中观察到了强烈的表面光学（SO）声子模式，这在大型结构中是不合适的。原位微光致发光（μ-PL）特性表明，具有 whispering gallery mode（WGM）特征的受限制的缺陷态发射占主导地位。发射峰位置随激发功率的增加而移动，表明通过束缚载流子发生非弹性散射。此外，由于不同的复合过程对 WGM 共振带的贡献不同，在低温（80 K）下短波长发射模式占主导地位，而在高温（300 K）下长波长发射模式占主导地位，这也通过时间分辨 PL 测量得到了证实。所有这些结果都反映了 WGM 腔体内的表面消逝波与 SO 声子/极化子之间的强耦合，这将有利于对纳米光子器件应用中的表面/界面相关性质进行合理的剪裁。
