Ultra-long Al doped core-shell nanowires: Relationship between structural defect and optical property

The defects in nanomaterials can greatly affect their photoluminescence (PL) properties. To investigate the role of defects in the PL properties of SiCnw and improve their properties, Al doping and core-shell structure design are employed. Based on the above purpose, ultra-long Al-SiCnw@SiO₂ with a length of hundreds of micrometers are prepared via one-step thermal evaporation process. The Al exists in the lattice of SiC and SiO₂ in the form of substitutional and interstitial atoms, respectively, causing more defects in the nanowires. These defects can enhance the phonon scattering and phonon energy. After doping Al, the PL property of nanowires is improved by 36% and 244%, respectively, compared with SiCnw@SiO₂ and SiCnw. The enhanced Fröhlich electron-phonon interaction caused by defects and the decreased band gap accelerating the transition of electrons are the main mechanisms of the property improvement. With the help of phonons, the electrons will be easier excited to conduction band. When they back to the ground state, more energy will be released, thereby improving the PL property. This work is helpful for the design of nanowires by doping elements to improve the PL property, and the preparation of large scale ultra-long doped nanowires applied in the optoelectronics.